When setting photoflash exposures, the guide number (GN) of photoflash devices (flashbulbs and electronic devices known as "studio strobes", "on-camera flashes", "electronic flashes", "flashes", and "speedlights") is a measure photographers can use to calculate either the required fstop for any given flash-to-subject distance, or the required distance for any given fstop. To solve for either of these two variables, one merely divides a device's guide number by the other.

Though guide numbers are influenced by a variety of variables, their values are presented as the product of only two factors as follows:

Guide number = f-number × distance

This simple inverse relationship holds true because the brightness of a flash declines with the square of the distance, but the amount of light admitted through an aperture decreases with the square of the f-number. Accordingly, as illustrated at right, a guide number can be factored to a small fnumber times a long distance just as readily as a large fnumber times a short distance.

Guide numbers are not an absolute measure of flash power (a property called luminous energy) because they are influenced by other variables, notably the camera's ISO setting (film speed) and flash coverage angle. For any given ISO setting and coverage angle however, an inherently more powerful flash device featuring a guide number that is, for instance, twice as great will permit subjects to be properly exposed from twice as far away for any given fstop, or conversely, will permit scenes at a given distance to be properly exposed at an fnumber twice as great.

The guide number system, which manufacturers adopted after consistent-performing mass-produced flashbulbs became available in the late 1930s, has become nearly superfluous due to the ubiquity of electronic photoflash devices featuring variable flash output and automatic exposure control, as well as digital cameras, which make it trivially easy, quick, and inexpensive to adjust exposures and try again. Still, guide numbers in combination with flash devices set to manual exposure mode remain valuable in a variety of circumstances, such as when unusual or exacting results are required and when shooting non-average scenery.

Different models of flash devices available on the market have widely varying maximum-rated guide numbers. Since guide numbers are so familiar to photographers, they are near-universally used by manufacturers of on-camera flash devices to advertise their products' relative capability. However, such a practice demands industry-wide standardization of both the ISO setting and illumination angle underlying the ratings; this has only been partially realized. For the most part, manufacturers state guide numbers relative to a sensitivity of ISO 100. However, manufacturers sometimes rate guide numbers at ISO 200, which makes them 41% greater. Furthermore, the illumination angles underlying manufacturers' ratings vary greatly, which can make it particularly difficult to compare models.

Understanding guide numbers

Units of measure

Throughout most of the world where the metric system (SI) is observed, guide numbers are expressed as a unitless numeric value like 34, even though they are technically a composite unit of measure that is a two-factor product:  As such, guide numbers can be reduced either to distance in meters or to fstops depending on how one uses the guide number in a calculation.

In the U.S. however, photographers typically measure distances in feet and require guide numbers scaled accordingly. To serve the U.S. market, manufacturers of flash devices typically provide foot-based guide numbers and add nomenclature such as feet, ft, or the foot symbol ( ′ ) to unambiguously denote that fact, e.g. Guide number: 92′. Another common practice when flash devices are marketed in the U.S. is to provide two guide numbers—which can be expressed in a variety of formats—so distances and fnumbers may be calculated using either feet or meters, e.g. Guide number:

Though nomenclature conventions such as these can make guide numbers misleadingly appear to be length-based units of measure, they serve as notations to eliminate ambiguity as to which length-based system of measurement underlies the guide numbers. As with metric-based guide numbers, foot-based guide numbers are a two-factor unit of measure except the units are

To convert a guide number given in meters to feet, divide by 0.3048. To convert a guide number given in feet to meters, multiply by 0.3048.

Calculating with guide numbers
It is easy to use guide numbers to calculate either an aperture or a flash-to-subject distance. Consider a flash device with a rating of 28 meters (which might be marked "92 feet", "28 DIN", "28/92", "92", etc.).

Suppose a photographer has a flash device with a guide number of 44 (m) / 144 (ft), sets the camera's aperture to , and wants to know the required flash-to-subject distance; he merely divides the guide number by 4. Thus, a subject 11 meters or 36 feet away will be correctly illuminated  = 11 m, and  = 36 ft). For the same guide number and an aperture of , the light source must be 5.5 meters or 18 feet from the subject.

Alternatively, if one has an established flash-to-subject distance and wants to find the required f-number, one divides the guide number by the distance. Example: Guide number = 48                          (m) and the distance is 6 meters; one needs and aperture of  (GN 48 ÷ 6 m = ).

Example for finding a distance
Suppose a photographer wants to shoot with an aperture of  and the guide number is 28 (m) / 92 (ft). The flash device must be 10 meters (33 feet) from the subject.
In metric: GN 28 ÷  = 10 m
In U.S. customary units: GN 92 ÷  = 33 ft

Example for finding an aperture
Suppose a photographer's flash-to-subject distance is 9.75 meters (32 feet) and the guide number is 39 (m) / 128 (ft). The aperture must be .
In metric: GN 39 ÷ 9.75 m =
In U.S. customary units: GN 128 ÷ 32 ft =

Details
The magnitude of guide numbers is a function of the following four variables:
 The total luminous energy (in lumen⋅seconds) emitted by the flash head (which is itself the product of the duration and the average luminous flux of a flash). See Glossary, below for illumination terminology.
 The solid angle subtended by the circular- or rectangular-profile beam as it leaves the flash head (the average of the beam's X- and Y-axis angles).
 The ISO sensitivity setting.
 Filters (either on the flash or on the camera lens). See Effect of filters, below.

The above variables fall into two classes that influence the magnitude of guide numbers:

 Those that affect the non-distance-related intensity of a flash arriving at a scene (a property called illuminance, measured in lux) or its duration; namely its power setting, flash coverage angle, and color gels in front of the flash head.
 Those that affect the camera's non-aperture-related light sensitivity; namely lens filters and the ISO rating of the film/imaging sensor.

Changing either the fstop or the flash-to-subject distance does not affect guide numbers because, by definition, choosing a different value for one factor is automatically accompanied by a reciprocal adjustment in the other.

Most modern flash devices can operate at guide numbers less than their maximum ratings via either manual adjustment of their power settings in binned steps, by an in-flash automatic light sensing feature, or by being cued by the camera's sensor; both the latter options make continuously variable adjustments. Manual attenuation settings are usually steps in powers of 0.5 (full fstops) that commonly extend five to eight fstops deep , ,  To calculate how reductions in power levels affect guide numbers, see Effect of power settings, below.

Shutter speeds do not factor into guide number calculations with electronic flash and, for the most part, have no effect on exposures. See Effect of shutter speeds, below.

Guide numbers are not affected by scene reflectance. Guide numbers are a function of the illuminance and duration of a flash (a property called luminous exposure that have lux⋅seconds as their units of measure) arriving at a scene as measured by an incident-light meter (pictured at right), not the amount leaving the scene. This often seems counterintuitive to hobbyists who incorrectly assume that cameras' built-in reflected-light meters are a definitive measure of exposure. However, this principle underlies why using a camera with a through-the-lens meter to photograph a park bench surrounded by sunlit snow underexposes the image, making the bench appear nearly black and the snow as dark as grass and foliage. This is because reflected-light meters are calibrated for an average scene reflectance of 18 percent and can't "know" when a scene has non-average reflectance. See also Gray card and Light meter.

Guide number distances are always measured from the flash device to the subject; if the flash device is detached from the camera, the position of the camera is irrelevant. Furthermore, unless a flash device has an automatic zoom feature that follows the setting of a camera's zoom lens, guide numbers do not vary with the focal length of lenses.

Note that manufacturers of flash devices may provide guide numbers ratings specified relative to ISO 200, which increases them by the square root of the difference, or a 41 percent increase relative to those given at ISO 100. See Effect of ISO sensitivity, below. When comparing or shopping for flash devices, it is important to ensure that the guide numbers are given in the same ISO sensitivity, are for the same coverage angle, and reduce to the same unit of distance (meters or feet). When these three variables have been normalized, guide numbers can serve as an relative measure of intrinsic illuminating energy rather than an inconstant metric for calculating exposures.

Effect of power settings
Most modern electronic flash devices have manually adjustable power settings. Moreover, virtually all modern on-camera flash devices that have manually adjustable power settings also provide either a built-in mechanical circular calculator (such as shown in the photo at the top of this article) or a digital display that automatically shows the effect power levels have on fstop and distance (guide number).

Nevertheless, for those who want to master the math, guide numbers diminish from their full-power ratings as the square root of their fractional setting per the following formula:

…where
 is the numerator in the fraction of the power setting
 is the denominator in the fraction of the power setting

The following is a step-by-step example of using the above formula: Suppose your full-power guide number is 48 (it is irrelevant if it is scaled for meters or feet for this purpose) and the flash device is set to  power. Divide 1 by 16 to obtain 0.0625. Take the square root of that (the  button on a calculator), which equals 0.25, and multiply that by the guide number of 48 to obtain a reduced-power guide number of 12.0.

The mathematical relationship between guide numbers and power levels can also be understood using the below alternative formula, which is suitable whenever the numerator in the fractional power setting is 1 (which is usually the case with flash devices):

…where
 is the denominator in the fraction of the power setting

Example: Suppose your full-power guide number is 51 and your flash device is set to  power. Take the square root of 32 (the  button on a calculator), which equals approximately 5.657. Divide 51 by 5.657 to obtain a reduced-power guide number of 9.0.

Effect of flash angle (zoom setting)
Many flash devices have auto- or manual-adjust zoom features that permit the illumination angle to be widened (lessening the guide number) to fully illuminate the image area of wide-angle lenses, or narrowed (increasing the guide number) for telephoto lenses. Such coverage angles may be given in degrees but are often expressed as being equivalent to lens focal lengths for full-frame, 35 mm cameras. Manufacturers' advertising practices vary as to the angle of coverage underlying their guide number ratings, in large part because some flash devices can be zoomed whereas others are fixed.

Virtually all modern on-camera flash devices with zoomable flash heads also have either a built-in mechanical circular calculator (such as shown in the photo at the top of this article) or a digital display; both automatically show the effect zoom levels have on fstop and distance (guide number).

Nonetheless, when comparing or shopping for flash devices with zoom heads, it would certainly be helpful if it were possible to mathematically convert advertised guide numbers from one manufacturer's flash angle (zoom level) to another manufacturer's flash angle. This is because guide numbers are often—though not always—given at their most zoomed setting and not all flash devices can zoom to the same extent.

Unfortunately, the optics of flash heads are complex; each manufacture's designs not only have illumination areas that are slightly different, but are the product of differing relative proportions of transmission, diffusion, reflection, and refraction among their optical elements (flash tube, reflector, Fresnel lens, and add-on wide-angle adapter). Accordingly, there is no universal formula for precisely calculating how guide numbers diminish from, for instance, a 105 mm setting to 50 mm or 35 mm settings. One may consult the users guide for a specific flash device to obtain guide numbers for different zoom settings.

The below table illustrates the variation in guide numbers depending on zoom level for some select, relatively high-power zoom-capable flash devices.

Note A: Flash angle is equivalent to the denoted lens focal length for a full-frame 35 mm camera.

Effect of ISO sensitivity

Among other variables like illumination angle (for devices with zoomable flash heads) and power setting, guide numbers are a function of the ISO sensitivity (film speed or ISO setting on a digital camera). Guide numbers change as the square root of the difference in ISO sensitivity. Accordingly, a greater ISO sensitivity yields a greater guide number.

To allow photographers to properly calculate exposures, even older, base-model flash devices have at least a tabular table on the device showing its guide number for a limited range of common ISO sensitivities. Today, the state of the art has advanced so that with the exception of the least expensive models, virtually all modern on-camera flash devices feature either a built-in mechanical circular calculator (such as shown in the photo at the top of this article) or—more modern yet—a digital display; both methods automatically calculate the effect ISO settings have on fstop and distance (guide number). Such features make it exceedingly easy to find a suitable combination of fstop and distance so photographers seldom need to concern themselves with the mathematical details underlying how their flash devices' guide number changes with different ISO sensitivities.

Still, it can be helpful when comparing flash devices to understand how guide numbers vary with ISO sensitivity. Usually manufacturers state their products' guide number ratings relative to an ISO sensitivity of 100. However, some manufacturers of flash devices may provide guide numbers ratings specified relative to ISO 200, which increases its guide number by 41 percent relative to those given at ISO 100.

The below table shows the proportional change in a flash device's guide number relative to both ISO 100 and ISO 200.

Note that the extremely high guide numbers shown in the right-hand portion of the table have a limited real-world ability to extend flash distances. As the above photo illustrates, the fnumber × distance reciprocal relationship breaks down when on-camera flash devices that are set to full or near-full power are used in combination with cameras set to very high ISO sensitivities and large apertures (exceedingly long distances). ISO settings like 102,400 can yield guide numbers in excess of 1220 (m) / 4000 (ft) that seldom if ever permit extremely long-range flash photography due to particulates and aerosols typically present in outside air that fog images with haze glare and attenuate the reach of the light. Except in unusual atmospheric conditions, extraordinarily large guide numbers will produce suitable results only by either positioning the flash device off-axis from the camera by a fair distance or by shooting at the smallest apertures.

Note B: The ISO sensitivities shown in this table are their common nomenclature values; their actual underlying values may be slightly different, such as ISO 250, which is actually approximately 252.

Effect of filters
Filters reduce guide numbers regardless of whether they are gels placed over the flash device or are lens filters on the camera. Flash devices may come with detachable color-correction gels or filters to match the color of the flash with different types of ambient lighting such as incandescent and fluorescent. Some modern flash devices can even detect when color-correction gels have been attached and automatically compensate for their effect on guide numbers.

Unless a hot shoe-mounted electronic flash device's power can be controlled by a camera via through-the-lens metering (TTL), guide numbers must be manually compensated for the effect of on-lens filters. For instance a typical polarizing filter, which attenuates 1–1.5 fstops, will diminish guide numbers to 71–60% of their unfiltered rating.

Guide numbers diminish as the square root of filter attenuation in fstops, as per the following formula:

…where  equals the filter's rated loss in fstops.

The following is a step-by-step example of using the above formula: Suppose your guide number is 32 (it is irrelevant if it is scaled for meters or feet for this purpose) and the rated filter loss is 1.5 fstops. Take 0.5 and raise it to the power of 1.5 (using the  button on a scientific calculator), which equals roughly 0.35355. Take the square root of that (the  button), which equals approximately 0.595, and multiply that by the guide number of 32 to obtain a filtered guide number of 19.0.

The below table provides some common filter values.

When a flash device is set to manual (M) or automatic (A) exposure mode and is not being controlled via the camera's through-the-lens metering, a convenient way to compensate for the effect of a lens-mounted filter is to set the ISO rating on a camera to a higher value than the flash device. For instance, if a polarizing filter attenuates by 1 fstop and the flash device is set to ISO 100, then the camera can simply be set to ISO 200. The extra camera sensitivity compensates for the loss due to the filter.

The formula governing this relationship is as follows:

…where  equals the camera filter's rated loss in fstops.

Here is a step-by-step example of using this formula: Suppose a filter attenuates by 11/3 fstops and the flash device is set to ISO 100. Take 2 and raise it to the power of 1.3333 (using the  button on a scientific calculator), which is approximately 2.5198, and then multiply that by 100, which equals about 252. The nearest standard camera setting is ISO 250.

Effect of shutter speeds

With electronic flash
When electronic flash devices based on flashtube technology are used with most modern cameras (those with focal-plane shutters), shutter speed has no effect on guide numbers. See also Shutter (photography).

This is because even at the most powerful settings, flash durations seldom exceed a few milliseconds (thousandths of a second). With focal-plane shutters, a flash begins shortly after the shutter curtain has fully opened and must extinguish before the curtain begins to close. Selecting any shutter speed faster than the camera's rated Xsync speed, which is often between  and  of a second (from as long as 16.7 milliseconds to as little as 5.0 milliseconds) causes the shutter curtain to begin wiping closed across the film or sensor before the flash has extinguished. When this happens, an underexposed, gradated band appears along an edge of the image—often trailing off darker towards the left or bottom, as seen in the photo at top right.

Conversely, longer exposures also have no effect on guide number. After the flash has extinguished, longer shutter speeds will only increase the contribution from continuous ambient light, which can lead to ghosting with moving subjects. See also Flash synchronization.

With flashbulbs
Shutter speeds used to (and still do today) influence guide numbers when using flashbulbs due to their relatively long flash durations. Vintage flashbulbs, though no longer made, are still available and have a niche following, largely because even medium-size bulbs such as the once-popular General Electric Synchro-Press  had huge light outputs on the order of 23,000 lumen⋅seconds—far exceeding the most powerful of today's hot shoe-mounted electronic flash devices. At a relatively slow shutter speed of  of a second (40 milliseconds), the GE  had a guide number of 97.5 (m) / 320 (ft) at ISO 100 when using a typical 6- or 7-inch-diameter (150–175 mm) polished reflector. With peak powers often between one and two million lumens, many young baby boomers chased after fairylike retinal bleached spots (a symptom of flash blindness) for minutes after having their pictures taken at close distance with flashbulbs of the era.

If one wanted the benefit of all the light produced by a flashbulb (highest possible guide number), relatively long exposure times were required because most flashbulbs didn't stop producing useful amounts of light until 20–90 milliseconds (ms) after electrical current was applied. The GE  flashbulb for instance, was a Class M (medium peak) bulb, which were designed to produce peak luminous fluxes 20 ms after firing (see the graph at lower right). The  was intended for leaf shutter-type cameras and M sync photoflash triggering, which gave M bulbs a head start by delaying the opening of the shutter so any given camera's fastest exposure time would be centered at the 20 ms point (an 18.75 ms delay for instance, for a definitional camera capable of  second exposures, or 2.5 ms).  The GE  stopped producing useful amounts of light roughly 50 ms after current was applied. Thus, a camera with a fastest shutter speed of  of a second (one that began exposures 18.75 ms after a bulb was fired with M sync triggering), and which was set to  of a second, would close its shutter 59 ms after triggering a flashbulb (18.75 ms + 40 ms = 58.75 ms) and would achieve the maximum rated guide number from the .

So long as one used flashbulbs with leaf shutter-type cameras, faster exposures and larger apertures could be used to minimize motion blur or reduce depth of field at the expense of guide number. In the case of the GE Synchro-Press  with M sync for instance, shutter speeds as long as  of a second still diminished its guide number, though it still managed an impressive 140 (ft) at a  second exposure. This relationship between shutter speed and guide number was reflected in the guide number tables printed on flashbulb packaging after the industry-wide adoption of the guide number system, as exemplified by the below-left table for the .

Cameras with focal-plane shutters—even if they had PC connectors with X, F, M, or S-sync delays ("xenon sync" with zero delay and flashbulbs with peak delays of 5, 20, and 30 ms)—could not be used at speeds that attenuated guide numbers with most types of flashbulbs because their light curves were characterized by rapid rise and fall rates; the second shutter curtain would begin wiping shut during a period of rapid change in scene illuminance, causing uneven exposure across the image area that varied in nature depending on exposure duration and the type of bulb. With the GE SynchroPress  for instance, a modern camera with a focal-plane shutter and X sync would require a shutter speed of  of a second (67 ms) to obtain an even exposure across the entire image area—and a not-insignificant boost in the guide number by capturing all the luminous energy to the left of the 20 ms peak.

A notable exception to this limitation with focal-plane shutters was when using FP sync in combination with "flat peak" (FP) bulbs, which had  rise times followed by broad, relatively level plateaus in their light output curves. The FP bulbs, like GE's , allowed extraordinary flexibility with shutter speeds, ranging from the slowest speeds on the dial to the fastest where only a narrow slit passed over the film—at the expense of course, of guide number.

Fill flash: Guide numbers vs. distance
When filling in shadows outdoors, powerful flash devices (those with inherently greater guide numbers when compared at the same ISO sensitivity and coverage angle) can be useful because they permit photographers to increase the maximum flash-to-subject distance, such as when taking group photos. Clearly, more power helps because the sun is such a bright, unadjustable light source against which a flash device must compete. However, a contributing factor is that many modern cameras with focal-plane shutters can sync with flash devices at speeds no faster than  of a second; such a relatively long exposure requires particularly small apertures and/or low ISO sensitivities, both of which constrain how far a camera and its on-camera flash can be from the subject.

The tables below show the distances at which deep shadows will be filled with one fstop less than the sunlit portions of the scene, which is a common fill level. The exposures given here assume average frontlit subjects under bright or hazy sun with distinct shadows for photos taken between 2 hours after sunrise and 2 hours before sunset.

As can be seen by referring to the above tables, if a photographer has a camera with an X-sync speed of 1/125 th of a second, is shopping for a flash device, and desires the capability to fill shadows from up to 2.5 meters (8 feet) away, a flash device with a guide number of at least  will be required.

Note that increasing the ISO sensitivity of a digital camera (or choosing a faster film speed) will not increase the distances given in these tables because the extent to which ISO sensitivity affects the exposure in the fill-flash areas of an image will equally affect the sunlit ones. For any given shutter speed, a flash device can only fill shadows to 50% the contribution from the sun out to a certain distance; at a camera's Xsync shutter speed, no change in ISO sensitivity—and accompanying fstop setting—can influence this proportional relationship.

History

General Electric introduced the guide number system in 1939 concurrently with the introduction of a compact, wire-filled flashbulb called the  This compelling new way of easily and accurately calculating photoflash exposures was quickly adopted by manufacturers of a wide variety of photographic equipment, including flashbulbs, film, cameras, and flashguns.

The first flashbulb was introduced in 1925 and was filled with flash powder. In 1929, Sashalite Limited in London invented the "Sashalite" flashbulb, which was filled with a crumpled wad of aluminum foil so thin (about one-tenth the width of a human hair) it could not be picked up with fingers. The Sashalite, which was manufactured under contract by General Electric Co., Ltd. in London, came with an instruction sheet directing photographers to insert the Sashalite into "an ordinary electric torch" and to set their shutter to either "Bulb" or "Time". The instruction sheet further suggested an aperture of  for Sashalite's larger flashbulb and  for the smaller. However, apparently assuming photographers using their product would be doing so in a relatively narrow range of distances common to portraiture, made no mention of flash-to-subject distance. The instruction sheet then directed the photographer as follows:

In 1932, Philips introduced what was arguably the first modern flashbulb with wire fill under the trade name "Hydronalium". Philips' technology was licensed in 1937 by Wabash Photolamp Corporation and introduced to the U.S. market as Superflash bulbs. Shortly later, in 1939, General Electric under their MAZDA brand introduced their very successful, golf ball-size, wire-filled, bayonet-base, Midget

Prior to GE's inverse of the squares innovation, photographers and publications—via tedious trial and error with different flashbulbs and reflectors—generated tables providing a large number of aperture-distance combinations. For instance, a 1940 edition (written too late to incorporate guide numbers) of the Complete Introduction to Photography by the Journal of the Photographic Society of America featured an exposure table for foil-filled flashbulbs, which is shown below. The parenthetical values in bold were not part of the original table; they show the equivalent guide number for each aperture-distance combination.  Note the scatter in the guide number values in each column; the data for the right-most flashbulb setup has over a three-quarter fstop variation from high to low.

Bear in mind that the above table is for only one film speed. For end users, obtaining proper exposures with flashbulbs was an error-prone effort as they mentally interpolated between distances and fstop combinations that weren't very accurate in the first place. Had the guide number system existed by this point, the above table would not have required the left-most column showing distances and would have required only one row (showing guide numbers) under each heading.

By 1941, two years after GE introduced the guide number system, guide number ratings for products like the GE  were being discussed  in books like Flash in Modern Photography. By 1944, the 16th edition of Wall's Dictionary of Photography featured a guide number table. Perhaps so as to not intimidate readers, that table still showed numerous combinations of distances and apertures, but it also featured a new column showing the guide number that every cell in its row equalled. The guide number system underlying that table drove slightly finer increases, averaging a factor of  each, from one distance to the next (6, 9, 12, 18, and 24 feet) so each step would be accompanied—by definition—by an increase in aperture of precisely one fstop. Not surprisingly, the data scatter was as tight as mathematical rounding to the nearest foot permitted.

By late 1949, authors catering to hobbyists were using guide numbers in articles in a routine fashion, as exemplified by the January 1950 issue of Popular Photography, as follows:

Upon introducing the new inverse of the squares concept in 1939, General Electric initially referred to the new system as "Flash Numbers". Two years later, Flash in Modern Photography (1941) used the term "guide number" on page 47, on the very next page used the term "Flash Number" (title case), and later still used the term "flash number" (lowercase). Terminology was similarly mixed in the United Kingdom for years after the introduction of the guide number system; circa 1954, "Flash Factor", "Flash number" (and sometimes "Guide number") were in use.

Glossary

See also
 Exposure (photography)
 Exposure value
 Flash comparison
 Flash (photography)
 Flash synchronization
 Flashtube

Notes

References

Further reading
 Bryan Peterson, Understanding Flash Photography: How to Shoot Great Photographs Using Electronic Flash, (paperback – August 30, 2011), Amphoto Books,

External links
 D. 'n' A. Seaver: Conley cameras
 Photographic Memorabilia: Flash Photography ~ History & ILFORD
 Scantips.com: Understanding Flash Guide Numbers, plus guide number Calculator
 Scantips.com: EV – Exposure Value (with EV table and EV calculator)
 Sekonic.com: EV/Lux/FootCandle Conversion Chart

Flash photography
Photographic lighting
Light sources

Guide number


Tim Burke (born May 29, 1955 in Melrose, Massachusetts) is a former ice hockey defenseman and assistant coach in many different leagues.

Career
Tim Burke serves as the director of scouting for the San Jose Sharks.  In this role, he coordinates and oversees the Sharks efforts in the National Hockey League's annual Entry Draft while working closely with Executive Vice President and General Manager Doug Wilson and his staff. In addition to being the principal decision-maker at the draft table, Burke is also responsible for evaluating amateur talent at every level in all North American and European leagues and supervises all aspects of the club's amateur scouting efforts.
Burke's hard work and keen decision making, coupled with the talents of his competent staff at evaluating players, has produced admired results. Burke's selection process has helped the Sharks create a solid foundation of talented players from which to build the franchise around — including Patrick Marleau (1997), Douglas Murray (1999), Ryane Clowe (2001), Joe Pavelski (2003), Thomas Greiss (2004), Torrey Mitchell (2004), Marc-Edouard Vlasic (2005), Jamie McGinn (2006) Justin Braun (2007) and 2011 Calder Memorial Trophy runner-up Logan Couture (2007), all of whom played prominent roles in the Sharks recent seasons.
Since the 2003 NHL Draft, no NHL team has produced more games played among their drafted players than the Sharks (3,123) and the Sharks are tied for first in the NHL for average number of homegrown players on the team's roster each season since the 2005-06 (12).
	A member of the Sharks scouting department since the 1992-93 campaign, Burke was promoted to his current position on June 4, 1996. Before his promotion, Burke served as director of professional scouting from 1992–96 and evaluated talent throughout all North American professional leagues and assisted with amateur scouting.
	From 1987-92, he spent five seasons in the New Jersey Devils organization, serving in several capacities, including as a Devils assistant coach, head coach for the American Hockey League's Utica Devils and as a pro scout. Burke was also an assistant coach at Princeton University from 1984-86.
	A former defenseman, Burke was selected by the Montreal Canadiens in the seventh round (124th overall) of the 1975 NHL Entry Draft and by the Chicago Cougars in the second round (25th overall) of the 1974 World Hockey Association Entry Draft. He was a four-year letterman in both hockey and baseball at the University of New Hampshire, where he was named to the NCAA's All-America hockey team after his senior campaign.
	He played seven years of professional hockey following his outstanding collegiate career, including three seasons (1977–80) with the Nova Scotia Voyageurs, the Canadiens AHL affiliate, and one season with Jokerit Helsinki in the Finnish Elite League.

See also
List of New Jersey Devils head coaches

Awards and honors

References

External links

1955 births
Living people
AHCA Division I men's ice hockey All-Americans
American ice hockey coaches
American men's ice hockey defensemen
Baltimore Skipjacks (ACHL) players
Cape Cod Buccaneers players
Chicago Cougars draft picks
Ice hockey coaches from Massachusetts
Ice hockey players from Massachusetts
Jokerit players
Montreal Canadiens draft picks
New Hampshire Wildcats men's ice hockey players
New Jersey Devils coaches
New Jersey Devils scouts
Nova Scotia Voyageurs players
Sportspeople from Melrose, Massachusetts
San Jose Sharks scouts
Ice hockey people from Middlesex County, Massachusetts
Wichita Wind players

Tim Burke (ice hockey)


The European long-distance paths (E-paths) are a network of long-distance footpaths that traverse Europe. While most long-distance footpaths in Europe are located in just one country or region, each of these numbered European long-distance paths passes through many countries.

The first long-distance hiking trail in Europe was the National Blue Trail of Hungary, established in 1938. The formation of the European Union made transnational hiking trails possible. Today the network consists of 12 paths and covers more than , crisscrossing Europe. In general the routes connect and make use of existing national and local trails such as the GR footpaths.

The paths are officially designated by the European Ramblers' Association.

List

See also
Geography of Europe
GR footpath
EuroVelo, the European cycle route network
Long-distance trails in the United States

References

External links

Overview of the paths (European Ramblers' Association)
Find all hiking trails (Waymarkedtrails.org)
Find the OpenStreetMap Project on E-paths (Openstreetmap.org)
Transcaucasian Trail (Transcaucasian Trail)

01
Europe

European long-distance paths


José Gabriel Lopes da Silva, also known as Gabriel Mariano (May 18, 1928 in Ribeira Grande – February 18, 2002 in Lisbon, Portugal), was a Cape Verdean poet, novelist, and an essayist.

He studied at São Joaquim and graduated as director in Lisbon.  He returned to Cape Verde 1950 where he participated in the creation of the magazine Restoration (with Jorge Pedro Barbosa and others), the Cultural Supplement (with Carlos Alberto Monteiro and others) and Boletim Cabo Verde (Cabo Verde Bulletin).  His cultural activity brought him to the attention of the local governor and he was deported to Mozambique.

He published poems, novels and essays, in Portuguese and Cape Verdean Creole.

After independence, he returned to Cape Verde.  He wrote Vida e Morte de João Cabafume in 1976 which won the African Literary Award, an essay on Capeverdean culture in 1991 and a poetic anthology named Ladeira Grande in 1993.  He spent the remainder of his life in Portugal, he died on February 28, 2002.

Some of his poems are in the Tertúlia collection of poems which were also made by other poets.

One of his poem can be found on the CD Poesia de Cabo Verde e Sete Poemas de Sebastião da Gama (2007) by Afonso Dias

He is not the same but could be related to another poet who was born in the island of São Nicolau, José Lopes da Silva (January 15, 1872- September 2, 1962 in Mindelo), he was also a professor and a journalist.

Works
 A Mestiçagem: seu papel na formação da sociedade caboverdeana (an essay published in "Suplemento Cultural", 1958)
 Do Funco ao Sobrado ou o Mundo que o Mulato Criou (a published essay  in "Colóquios Caboverdeanos", 1959)
 12 Poemas de Circunstâncias (12 Poems of Circumstances) (1965)
 Amor e partida na poesia crioula de Eugénio Tavares ou inquietação amorosa
 Capitão Ambrósio (Captain Ambrósio)
 Inquietação e serenidade. Aspectos da insularidade na poesia de Caboverde
 Nome de casa e nome de igreja
 O Rapaz Doente (1963)
 Osvaldo Alcântara — O Caçador de heranças ou inquietação social
 Uma Introdução à Poesia de Jorge Barbosa (An Introduction Of Poetry From Jorge Barbosa)
 Vida e Morte de João Cabafume (Via Editora, 1976), won the African Literary Award
 Cultura Caboverdeana (Capeverdean Culture) (essays, Vega, 1991)
 Ladeira Grande (poetic anthology, editora Vega, 1993)

Notes

References
''The first version of the article is translated and is based from the article at the Portuguese Wikipedia (Main Page)

1928 births
2002 deaths
Cape Verdean essayists
Cape Verdean novelists
Cape Verdean poets
People from Santo Antão, Cape Verde
20th-century poets
20th-century novelists
20th-century essayists

Gabriel Mariano


De Witt Clinton Fort (June 8, 1830, Hardeman County, Tennessee – May 25, 1868, Hempstead, Texas). He was a member of the Texas House of Representatives and soldier in the Confederate army during the American Civil War.

Personal background
Fort received his A.B. degree from Centre College, Danville, Kentucky in 1850.
He was admitted to the practice of law in 1852 in Mississippi and in 1857 in Texas.
He was elected to serve in the Eighth Texas Legislature (1859-1861) and the special "Adjourned Session" (March 18, 1861 - April 9, 1861).

Fort closed his Austin County, Texas law office for the duration of the war in June 1861 and paid his own travel expenses to join J.E.B. Stuart's cavalry in Virginia for the First Battle of Manassas.  He was captured in Tennessee following the Battle of Farmington in May 1862, but escaped by leaping from a Union prison steamboat into the Mississippi River. Later, he created "Fort's Scouts," a small unit of Confederate Cavalry, acting in concert with General Nathan Bedford Forrest.  By the end of the war he had served with the Confederate units in Texas, Virginia, Mississippi, Tennessee and Missouri.  He was wounded during the closing weeks of the war.  His unit surrendered about one month after General Lee's surrender.

Fort was "clubfooted" and badly crippled from birth and unsuitable for military service.  However, by the time he surrendered, his small band had closed down the Memphis & Charleston Railroad to Union military travel and only large Union cavalry patrols would venture outside the Union military headquarters at Memphis, TN.

He carried the sobriquet, Captain "Clubfoot" Fort, C.S.A. proudly.

References
 14 Letters to A Friend by Laurier B. McDonald

1830 births
1868 deaths
People from Hardeman County, Tennessee
Politicians from Austin, Texas
People of Texas in the American Civil War
Centre College alumni
Texas lawyers
Members of the Texas House of Representatives
19th-century American politicians
19th-century American lawyers

De Witt Clinton Fort


In mathematics, a bilinear form is a bilinear map  on a vector space  (the elements of which are called vectors) over a field K (the elements of which are called scalars). In other words, a bilinear form is a function  that is linear in each argument separately:
   and
   and

The dot product on  is an example of a bilinear form.

The definition of a bilinear form can be extended to include modules over a ring, with linear maps replaced by module homomorphisms.

When  is the field of complex numbers , one is often more interested in sesquilinear forms, which are similar to bilinear forms but are conjugate linear in one argument.

Coordinate representation
Let  be an -dimensional vector space with basis .

The  matrix A, defined by  is called the matrix of the bilinear form on the basis .

If the  matrix  represents a vector  with respect to this basis, and similarly, the  matrix  represents another vector , then:

A bilinear form has different matrices on different bases. However, the matrices of a bilinear form on different bases are all congruent. More precisely, if  is another basis of , then

where the  form an invertible matrix . Then, the matrix of the bilinear form on the new basis is .

Maps to the dual space
Every bilinear form  on  defines a pair of linear maps from  to its dual space . Define  by

This is often denoted as

where the dot ( ⋅ ) indicates the slot into which the argument for the resulting linear functional is to be placed (see Currying).

For a finite-dimensional vector space , if either of  or  is an isomorphism, then both are, and the bilinear form  is said to be nondegenerate.  More concretely, for a finite-dimensional vector space, non-degenerate means that every non-zero element pairs non-trivially with some other element:
 for all  implies that  and
 for all  implies that .

The corresponding notion for a module over a commutative ring is that a bilinear form is  if  is an isomorphism. Given a finitely generated module over a commutative ring, the pairing may be injective (hence "nondegenerate" in the above sense) but not unimodular. For example, over the integers, the pairing  is nondegenerate but not unimodular, as the induced map from  to  is multiplication by 2.

If  is finite-dimensional then one can identify  with its double dual . One can then show that  is the transpose of the linear map  (if  is infinite-dimensional then  is the transpose of  restricted to the image of  in ). Given  one can define the transpose of  to be the bilinear form given by

The left radical and right radical of the form  are the kernels of  and  respectively; they are the vectors orthogonal to the whole space on the left and on the right.

If  is finite-dimensional then the rank of  is equal to the rank of . If this number is equal to  then  and  are linear isomorphisms from  to .  In this case  is nondegenerate. By the rank–nullity theorem, this is equivalent to the condition that the left and equivalently right radicals be trivial. For finite-dimensional spaces, this is often taken as the definition of nondegeneracy:

Given any linear map  one can obtain a bilinear form B on V via

This form will be nondegenerate if and only if  is an isomorphism.

If  is finite-dimensional then, relative to some basis for , a bilinear form is degenerate if and only if the determinant of the associated matrix is zero. Likewise, a nondegenerate form is one for which the determinant of the associated matrix is non-zero (the matrix is non-singular). These statements are independent of the chosen basis. For a module over a commutative ring, a unimodular form is one for which the determinant of the associate matrix is a unit (for example 1), hence the term; note that a form whose matrix determinant is non-zero but not a unit will be nondegenerate but not unimodular, for example  over the integers.

Symmetric, skew-symmetric and alternating forms
We define a bilinear form to be
 symmetric if  for all ,  in ;
 alternating if  for all  in ;
  or  if  for all ,  in ;
 Proposition Every alternating form is skew-symmetric.
 Proof This can be seen by expanding .

If the characteristic of  is not 2 then the converse is also true: every skew-symmetric form is alternating. However, if  then a skew-symmetric form is the same as a symmetric form and there exist symmetric/skew-symmetric forms that are not alternating.

A bilinear form is symmetric (respectively skew-symmetric) if and only if its coordinate matrix (relative to any basis) is symmetric (respectively skew-symmetric). A bilinear form is alternating if and only if its coordinate matrix is skew-symmetric and the diagonal entries are all zero (which follows from skew-symmetry when ).

A bilinear form is symmetric if and only if the maps  are equal, and skew-symmetric if and only if they are negatives of one another. If  then one can decompose a bilinear form into a symmetric and a skew-symmetric part as follows

where  is the transpose of  (defined above).

Derived quadratic form

For any bilinear form , there exists an associated quadratic form  defined by .

When , the quadratic form Q is determined by the symmetric part of the bilinear form B and is independent of the antisymmetric part.  In this case there is a one-to-one correspondence between the symmetric part of the bilinear form and the quadratic form, and it makes sense to speak of the symmetric bilinear form associated with a quadratic form.

When  and , this correspondence between quadratic forms and symmetric bilinear forms breaks down.

Reflexivity and orthogonality

A bilinear form  is reflexive if and only if it is either symmetric or alternating.  In the absence of reflexivity we have to distinguish left and right orthogonality. In a reflexive space the left and right radicals agree and are termed the kernel or the radical of the bilinear form: the subspace of all vectors orthogonal with every other vector.  A vector , with matrix representation , is in the radical of a bilinear form with matrix representation , if and only if . The radical is always a subspace of .  It is trivial if and only if the matrix  is nonsingular, and thus if and only if the bilinear form is nondegenerate.

Suppose  is a subspace.  Define the orthogonal complement

For a non-degenerate form on a finite-dimensional space, the map  is bijective, and the dimension of  is .

Different spaces
Much of the theory is available for a bilinear mapping from two vector spaces over the same base field to that field

Here we still have induced linear mappings from  to , and from  to . It may happen that these mappings are isomorphisms; assuming finite dimensions, if one is an isomorphism, the other must be. When this occurs, B is said to be a perfect pairing.

In finite dimensions, this is equivalent to the pairing being nondegenerate (the spaces necessarily having the same dimensions). For modules (instead of vector spaces), just as how a nondegenerate form is weaker than a unimodular form, a nondegenerate pairing is a weaker notion than a perfect pairing. A pairing can be nondegenerate without being a perfect pairing, for instance  via  is nondegenerate, but induces multiplication by 2 on the map .

Terminology varies in coverage of bilinear forms. For example, F. Reese Harvey discusses "eight types of inner product". To define them he uses diagonal matrices Aij having only +1 or −1 for non-zero elements. Some of the "inner products" are symplectic forms and some are sesquilinear forms or Hermitian forms. Rather than a general field , the instances with real numbers , complex numbers , and quaternions  are spelled out. The bilinear form

is called the real symmetric case and labeled , where .  Then he articulates the connection to traditional terminology:

Relation to tensor products
By the universal property of the tensor product, there is a canonical correspondence between bilinear forms on  and linear maps . If  is a bilinear form on  the corresponding linear map is given by

In the other direction, if  is a linear map the corresponding bilinear form is given by composing F with the bilinear map  that sends  to .

The set of all linear maps  is the dual space of , so bilinear forms may be thought of as elements of  which (when  is finite-dimensional) is canonically isomorphic to .

Likewise, symmetric bilinear forms may be thought of as elements of   (dual of the second symmetric power of ) and alternating bilinear forms as elements of  (the second exterior power of ). If , .

On normed vector spaces
Definition: A bilinear form on a normed vector space   is bounded, if there is a constant  such that for all ,

Definition: A bilinear form on a normed vector space  is elliptic, or coercive, if there is a constant  such that for all ,

Generalization to modules
Given a ring  and a right -module  and its dual module , a mapping  is called a bilinear form if

for all , all  and all .

The mapping  is known as the natural pairing, also called the canonical bilinear form on .

A linear map  induces the bilinear form , and a linear map  induces the bilinear form .

Conversely, a bilinear form  induces the R-linear maps  and .  Here,  denotes the double dual of .

See also

Citations

References

 . Also:

External links

Abstract algebra

Linear algebra
Multilinear algebra

Bilinear form


The Nine Tailors is a 1934 mystery novel by the British writer Dorothy L. Sayers, her ninth featuring Lord Peter Wimsey. The story is set in the Lincolnshire Fens, and revolves around a group of bell-ringers at the local parish church. The book has been described as Sayers' finest literary achievement, although not all critics were convinced by the mode of death, nor by the amount of technical campanology detail included.

Plot
Twenty years before the events of the novel, the family of Sir Henry Thorpe, squire of the Fenland village of Fenchurch St Paul, had suffered the theft of a valuable emerald necklace, still unrecovered. The family's then butler, Geoffrey Deacon, and his accomplice, Nobby Cranton, had been convicted and imprisoned. In 1918 Deacon had escaped from prison but apparently died shortly afterwards, the body lying in a quarry where it was found two years later, still in prison clothes. Deacon's widow Mary subsequently married one of the village bell-ringers, William Thoday.

The novel opens with Lord Peter Wimsey running his car into a ditch near Fenchurch on a snowy New Year's Eve. Stranded for a few days while repairs are carried out, Wimsey helps ring an all-night peal on the church bells after William Thoday is struck down with influenza. Lady Thorpe, Sir Henry's wife, dies the next day.

When Sir Henry dies the following Easter, a man's mutilated body is found in his wife's grave, believed to be that of a labourer calling himself 'Stephen Driver'. Oddly, the dead man was wearing French-made underclothes. The rector writes to Wimsey asking him to return to  investigate.

At the Post Office, Bunter, Wimsey's manservant, finds an uncollected letter posted in France. The writer is the French wife of a British soldier, Arthur Cobbleigh, who had deserted in 1918. Cobbleigh evidently knew where the emeralds were hidden and plotted to recover them with 'Driver' – who is revealed to be not the mutilated man, but Cranton.

A document found in the bell chamber is a cipher, written on the same paper as the letter from France. Wimsey's knowledge of change ringing enables him to decipher it, leading him to the emeralds, still in their hiding place in the church. He shows the document to Mary Thoday, and she and William promptly abscond to London. Wimsey speculates they have gone to be remarried, Mary having recognised the handwriting as that of Deacon, her first husband, and realising that her marriage to William was void as Deacon had still been alive at the time.

Wimsey identifies the mutilated man as Deacon himself. After his escape, Deacon had killed Cobbleigh and swapped clothes and identities with him, leaving him in the quarry. After marrying bigamously in France, Deacon had waited several years to return for the emeralds that he had hidden before his arrest. He had asked Cranton for help, sending him the cipher as a token of good faith. Cranton had broken into the church, discovered Deacon's body in the bell chamber and fled, horrorstruck.

William Thoday and his brother Jim, a merchant seaman, are interviewed. William confesses that on 30 December he had encountered Deacon, whom he had long believed to be dead, prowling around the church. Desperate to protect his wife from the scandal of a bigamous marriage, he had tied Deacon up and locked him in the bell chamber, planning to bribe him to leave the country the next day. Unfortunately, his bout of influenza prevented him from returning, and Jim discovered Deacon's dead body still tied up two days later. Still loyal to his brother, Jim had waited until the night after Lady Thorpe's funeral, when he made the body unrecognisable, hid it in her grave, then returned to his ship. When the body was rediscovered at Easter, each of the brothers thought that the other had killed Deacon.

When Wimsey returns to Fenchurch the following Christmas, floods are threatening the countryside, and Wimsey climbs the tower as the bells are sounding the alarm. The appalling noise in the bell chamber convinces him that Deacon, tied there for hours during the all-night New Year peal, could not have survived: Deacon had been killed by the bells themselves. Wimsey explains, "We needn't look for a murderer now. Because the murderers of Geoffrey Deacon are hanging already, and a good deal higher than Haman". William Thoday is drowned in the flood trying to save another man. Wimsey speculates that "I think perhaps he guessed at last how Geoffrey Deacon died and felt himself responsible".

Principal characters
 Lord Peter Wimsey
 Bunter, his manservant
 The Reverend Theodore Venables, rector of Fenchurch St Paul; his wife, Mrs Agnes Venables
 Sir Henry Thorpe, the local squire; his wife Lady Thorpe; their daughter Hilary
 Superintendent Blundell
 Geoffrey Deacon, once the Thorpes' butler, convicted of the theft of a necklace 20 years previously
 Nobby Cranton, London jewel-thief and Deacon's accomplice
 William Thoday, absent bell ringer, struck down with influenza
 Mary Thoday, William Thoday's wife, previously married to Deacon
 James "Jim" Thoday, William's brother, merchant seaman
 Potty Peake, village idiot
 The bell ringers: Hezekiah Lavender, leader, Rings Bell 8. Tailor Paul; Harry Gotobed, sexton Rings Bell 4. Jericho; Joe Hinkins, gardener, Rings Bell 5. Jubilee; Ezra Wilderspin, blacksmith, Rings Bell 1. Gaude; Alfred "Alf" Donnington, landlord of the Red Cow inn, Rings Bell 6. Dimity; Jack Godfrey, churchwarden, Rings Bell 7. Batty Thomas; Walter "Wally" Pratt, trainee ringer, Rings Bell 3. John; William "Will" Thoday and Lord Peter Wimsey, Ring Bell 2. Sabaoth.

Title
The Nine Tailors of the book's title are taken from the old saying "Nine Tailors Make a Man", which Sayers quotes at the end of the novel. As explained by John Shand in his 1936 Spectator article The Bellringers' Art, "'Nine Tailors' means the nine strokes which at the beginning of the toll for the dead announce to the villagers that a man is dead. A woman's death is announced with 'Six Tailors'. Hence the old saying  ... which might otherwise be construed as a slander on a worthy profession".

Awards and nominations
In 1996 the British Crime Writers' Association awarded the story a Rusty Dagger award for the best crime novel of the 1930s, an  award devised and organised for the Association by the noir writer, Russell James.

Literary significance and criticism
Writing in The New York Times on the book's first publication, Isaac Anderson said, "It may be that you, like this reviewer, do not know the difference between a kent treble bob major and a grandsire triple, but even so, you will probably enjoy what Dorothy Sayers has to say about them and about other things concerned with the ancient art of change-ringing, since her dissertation is all woven into a most fascinating mystery tale.... This is, most emphatically, Dorothy Sayers at her very best."

John Shand, writing in The Spectator in 1936, said "Those who would appreciate an artist's picture of a group of village bellringers – of the kind who can pull a rope with any Londoner – may find one in [this novel], [which] contains the best description known to me of the bells, the ringers and the art. It is probably, indeed, the only novel based on a study of campanology. Its very title and chapter-headings pay tribute to the peculiar vocabulary of the art." Shand considered the means of death to be "Novelist's licence, I am afraid. But a trifle like that cannot spoil a good story."

In his 1941 book Murder for Pleasure: The Life and Times of the Detective Story, Howard Haycraft noted that Sayers has been called by some critics the greatest of living mystery writers. He went on, "Whether or not the reader agrees with this verdict, he can not, unless he is both obtuse and ungrateful, dispute her preëminence as one of the most brilliant and prescient artists the genre has yet produced... [This book is] in the writer's estimation her finest achievement and one of the truly great detective stories of all time."

Taking the opposite view, the American critic Edmund Wilson, in his excoriating 1945 essay attacking the entire genre of detective fiction, Who Cares Who Killed Roger Ackroyd?, criticised The Nine Tailors in particular for being dull, overlong and far too detailed. He considered the bell-ringing prose to be "a lot of information of the kind that you might expect to find in an encyclopaedia article on campanology". In his view, Sayers does not, really, write very well: "it is simply that she is more consciously literary than most of the other detective story-writers and that she thus attracts attention in a field which is mostly on a sub-literary level."

Sayers' obituarist, writing in The New York Times in 1957, noted that many critics regarded The Nine Tailors as her finest literary achievement.

In their review of crime novels (revised edn 1989), the American writers Barzun and Taylor called this novel "For many reasons, no great favourite... despite Dorothy's swotting up of bell-ringing and the two good maps. The cause of death, however, is original, and the rescue scene in the church amid the flood shows the hand of the master. It should be added that this work is a favourite with many readers. Sinclair Lewis judged it the best of his four 'indispensables'. "

Also writing in 1989, H. R. F. Keating said that the author "incautiously entered the closed world of bell-ringing in The Nine Tailors on the strength of a sixpenny pamphlet picked up by chance – and invented a method of killing which would not produce death, as well as breaking a fundamental rule of that esoteric art by allowing a relief ringer to take part in her famous nine-hour champion peal."

Background
As a child and young teenager, Sayers lived on the southern edge of the Fens at Bluntisham-cum-Earith, where her father was rector. She also was inspired by her father's restoration of the Bluntisham church bells in 1910.

Much of the technical detail of the novel was taken from Charles Troyte's Change Ringing, quotations from which are placed at the start of many of the chapters.  In a letter discussing the book, Sayers said "I wrote [the novel] without ever having seen bells rung, by brooding over Troyte on Change-Ringing and trying to translate its technical descriptions into visual effects. That ... 'came out' beyond expectation".

Adaptations
The Nine Tailors has been adapted several times for BBC Radio: as a four-part serialisation by Giles Cooper for the BBC Light Programme in 1954, with Alan Wheatley as Lord Peter Wimsey; as an eight-part adaptation by Alistair Beaton for Radio 4 in 1980, with Ian Carmichael as Wimsey; and as a single two-hour Murder for Christmas programme by Michelene Wandor in 1987, with Gary Bond as Wimsey.

In 1974 the novel was adapted for BBC television by Anthony Steven as a series of four hour-long episodes, starring Ian Carmichael as Wimsey.

References

Further reading

External links

1934 British novels
Campanology
Novels by Dorothy L. Sayers
British mystery novels
Novels set in the 1930s
Novels set in England
Victor Gollancz Ltd books
British novels adapted into television shows
Identity theft in popular culture

The Nine Tailors


The Carrizo Plain (Obispeño: tšɨłkukunɨtš, "Place of the rabbits") is a large enclosed grassland plain, approximately  long and up to  across, in southeastern San Luis Obispo County, California, United States, about  northwest of Los Angeles.  The southern portion of the Carrizo Plain is within the  Carrizo Plain National Monument, which also includes most of the Caliente Range. The Carrizo Plain is the largest single native grassland remaining in California.  It includes Painted Rock in the Carrizo Plain Rock Art Discontiguous District, which is listed on the National Register of Historic Places. In 2012 it was further designated a National Historic Landmark due to its archeological value. The San Andreas Fault occurs along the eastern edge of the Carrizo Plain at the western base of the Temblor Range.

Geography and geology

The Carrizo Plain extends northwest from the town of Maricopa, following the San Andreas Fault.  Bordering the plain to the northeast is the Temblor Range, on the other side of which is California's Central Valley. Bordering the plain to the southwest is the Caliente Range.  The community of California Valley is in the northern part of the plain.  The average elevation of the plain is about . Soda Lake, a  alkaline lake, is in the center of the plain with the popular Painted Rock containing Chumash and Yokuts rock art nearby. As the central depression in an enclosed basin, Soda Lake receives all of the runoff from both sides of the plain.  At , Caliente Mountain, southwest of the plain, stands as the highest point in San Luis Obispo County.  The climate type of the Carrizo Plain is semi-arid grassland.  No trees grow there and the annual rainfall is around  per year.

The Carrizo Plain is an easily accessible place to see surface fractures of the San Andreas Fault; they are clearly visible along the eastern side of the plain, at the foot of the Temblor Range. They are best seen in early morning and evening light, when shadows enhance the topography. In addition to its spring wildflower displays, Carrizo Plain is also famous for Painted Rock, a sandstone alcove adorned with pictographs created by the Chumash people around 2000 BC.

Wallace Creek

Wallace Creek is a small stream, draining into Soda Lake, that remains dry most of the year.  It drains perpendicular to the San Andreas Fault, and the creek bed is currently offset by  due to the movement of the fault.  About  of the displacement was created during the 1857 Fort Tejon earthquake. The current segment began forming 3,700 years ago. Sometime between 1540 and 1630 A.D., the creek was offset by about  feet in an even larger earthquake.

Two other older creek beds lie  northwest along the San Andreas Fault.  The first creek bed was created around 13,000 years ago when climate change formed the creek on a large active alluvial fan. The second bed was created about 11,000 years ago.

The creek has been carefully studied by geologists to find a correlation between the offset and historical events, such as earthquakes, that have occurred along the San Andreas Fault. Although Wallace Creek is not the only creek that has been offset by the San Andreas Fault, it is the most spectacular.

Access

State Route 166 passes the south entrance to the Carrizo Plain, and State Route 58 crosses through the northern portion.  Connecting them is the narrow Soda Lake Road, the only dependably passable road through the plain—but even this may become impassable during or soon after a rain since the middle portion of it is gravel.

Geology

San Andreas Fault
The most prominent geologic feature of the Carrizo Plain is the San Andreas Fault, which runs along the northeast side of the plain, at the base of the Elkhorn Scarp. The section of the fault in the Carrizo Plain is the oldest section along the entire fault zone. Displacement on the San Andreas is responsible for the development of distinctive features, including shutter ridges, diverted or decapitated stream channels, and sag ponds. One feature relating to the San Andreas Fault and aligned to it in the Carrizo Plain is the Dragon's Back pressure ridge.

Other faults
The Big Spring Fault, the San Juan Fault, the Morales Fault, and the White Rock Fault are small faults that run parallel to the San Andreas Fault along the Caliente Range on the western boundary of the Carrizo Plain.

Soil taxonomy

The parent materials for soils in the Carrizo Plain are predominantly alluvium deposits.  Alluvium is soil that has been deposited by rivers or flowing water.  The Paso Robles formation is a Pleistocene aged alluvium deposit that reaches up to  thick near the San Andreas fault and thins out towards the north and west.  The Paso Robles formation is a well known aquifer that has been reliably productive for ground wells throughout the area.  The upper layers of soil are more recent alluvium.  This recent layer is thickest near Soda Lake and thins out towards the mountains to the east and west.  Throughout the valley the soil composition varies greatly and includes clay loams, silty clay loams, loams, sandy loams, and gravelly loams.   The sandier soils tend to reside near the slopes of the valley and provide greater drainage while the soils with more clay are located on the valley floor near Soda Lake, and have much poorer drainage.   The soils in the Carrizo Plain have very low fertility because of their high alkalinity content and low rainfall due to the semi-arid climate.

Fauna

The Carrizo Plain is home to 13 species listed as endangered either by the state or federal government, the largest concentration of endangered species in California. Some of these species include the San Joaquin kit fox, the San Joaquin antelope squirrel, the blunt-nosed leopard lizard, the giant kangaroo rat, greater and lesser sandhill cranes, and the California condor.  The tule elk, pronghorn, black-tailed jackrabbit, western coyotes, and Le Conte's thrasher all also make their homes in the Carrizo Plain.  The hotter climate and ecology of Carrizo Plain allows the Le Conte's thrasher of the Southwestern United States to have a small disjunct range farther north than normal.
 San Joaquin kit fox – a small nocturnal subspecies of the kit fox that was formerly common throughout the San Joaquin Valley but has recently become endangered.
 Blunt-nosed leopard lizard – a small, 3–5 inch gray to brown lizard with large dark spots and cream-colored cross bands. It has a broad, triangular shaped head and is endemic to California. It inhabits the grasslands and alkali flats of the San Joaquin Valley and the surrounding foothills and valleys.
Giant kangaroo rat – the largest of all kangaroo rats.  The giant kangaroo rat is also endemic to California and now only occupies about 2% of its original range, making it critically endangered.
San Joaquin antelope squirrel – a light tan squirrel with a white belly and a white stripe down its back and sides.  Most of its habitat is used for agriculture, making the Carrizo Plain the habitat for most of the remaining population.

Carrizo Plain National Monument

Management—historical overview

In 1988, U.S. Bureau of Land Management (BLM), the California Department of Fish and Game (DFG), and the Nature Conservancy (TNC) partnered together to purchase an  parcel of Carrizo Plain land. This joint effort ensured the protection of the plain. Then in 1996, the Carrizo Plain Management Partners again created a joint initiative called the Carrizo Plain Natural Area (CPNA) Plan. The goal of this plan was to:
 Establish long-term mission and vision statements that reflect the long-term objectives of the CPNA,
 Outline objectives and goals for the life of this plan that will help to achieve the mission,
 Consolidate a descriptive inventory of area resources and outline appropriate public uses of those resources,
 Provide an overview of operations, maintenance and personnel needs to assist in developing annual work plans and budgeting for implementation of plan goals.

On January 12, 2001, President Bill Clinton signed a presidential proclamation establishing the Carrizo Plain as a national monument. The first manager of the new Carrizo Plain National Monument was Marlene Braun (1958–2005); she was succeeded by Johna Hurl. The managerial partners of the CPNA took the responsibility of maintaining this new national monument. Since then, the area of protected land has increased to .

Carrizo Plain Natural Area Plan

Mission statement
"Manage the Carrizo Plain Natural Area (CPNA) so that indigenous species interact within a dynamic and fully functioning system in perpetuity while conserving unique natural and cultural resources and maintaining opportunities for compatible scientific research, cultural, social and recreational activities."

Administration
Routine monthly meetings and coordinated planning are essential parts in the management of the CPNA. The administration partners of the CPNA work together to make decisions about the area and what needs to be taken care of in order to maintain the natural environment of the plain. Although each partner has its own headquarters and administrative personnel, the Education Center Coordinator is one position that is funded by all of the CPNA partners. At BLM the staff consists of a project manager, a biological technician, a heavy equipment operator, a computer specialist, and a law enforcement ranger. All TNC personnel are located at their office in San Francisco. DFG at the moment has only one Wildlife Biologist at CPNA along with a Wildlife Assistant II and a Scientific Aide. Outside specialists also volunteer their time to study the area, from plant ecologists to species specialists. The fire suppression administration is the responsibility of BLM, which has formal agreements with Kern, Santa Barbara, and San Luis Obispo counties to help share in the support and funding of its fire suppression program. Funding for other programs within Carrizo Plain National Monument come from its management partners.

Research

When the CPNA Plan was implemented in the late 1990s, one of its first assignments was to gather information on the area's biological, cultural, recreational, and physical resources. The information obtained by the management partners has helped to ensure that each decision made on behalf of the Carrizo Plain National Monument will benefit all of its resources. This research has also helped to manage different activities and events within the plain. For example, plant community restoration seems to be one tool that could benefit the entire region by promoting native species diversity, re-establishing natural biological processes, and protecting endangered species habitats.

Current management projects
One of the current range management projects involves removing non-native grasses by selective cattle grazing early in the season when non-native grasses emerge. Later in the season, the management team removes the cattle, giving native plants a competitive advantage versus the non-native vegetation. The use of grazing on the Carrizo Plain National Monument remains a controversial practice.

Future management projects

There are an abundant amount of minerals in the Carrizo Plain National Monument. Gypsum, a white mineral used in plasters and wallboards, is a plentiful resource in the plain found in shallow, low-grade areas. In addition, there are detectable amounts of uranium and phosphates. All of these minerals are of low-grade quality, making them unprofitable to reclaim and manufacture.

Camping

Campgrounds
Camping within Carrizo Plain National Monument is available at two primitive campgrounds – KCL Campground and Selby Campground. These two sites differ markedly.

KCL is located in the southern part of the monument, west and very close to Soda Lake Road. Access from the main road is easy, and the camping area is generally bounded by a wooden fence. The campground has eight picnic tables and firepits, and is frequently occupied by "day use" visitors, although overnight camping is also allowed. Trees about the campground provide shade – some of the only shade in the monument's valley.  As this site was previously owned by the Kern County Land Company, there are several outbuildings in a non-maintained state. The corrals may be used by visitors to stable their horses.

Selby is located more to the north and more distant from Soda Lake Road.  A good gravel road leads to the campground from Soda Lake Road over a distance of five miles.  The road is generally usable in all weather conditions, but does wind and have some moderate grades as it approaches the campground area.  This site is much more rugged, located on a man-made cut into the natural terrain, bounded by hills and canyons.  Camp tables are covered by shade structures, a permanent and toilet outhouse is available (no water), camping is allowed anywhere upon the large flat areas.  Hiking up and into the adjoining Wilderness Study Area provides hearty exercise and impressive views.  The nearby Selby Rocks formation offers a view of large granite boulders.  (It is not advised to climb the rocks as the loose granite surface is fragile.)  A recent addition is a water spigot that provides non-potable water to the campsites.

Primitive camping
Car camping is also an option within certain areas within the monument, primarily in the foothills.  Camping is not allowed in the main valley floor.  See the CPNM Visitor Resource Map.

Conservation management issues

World Heritage Site

The Wilderness Society considered the Carrizo Plain as a nominee for World Heritage Site status.  Only two other locations in California – Redwood National Park and Yosemite National Park – have received this status.  This idea was greatly opposed by The Independent Petroleum Association and the residents of the nearby city of Taft, while supporters of the nomination included the City of San Luis Obispo, the San Luis Obispo Chamber of Commerce, and the San Luis Obispo Chapter of the League of Women Voters.

Advantages of World Heritage Site status for the Carrizo Plain might have included increased tourism for the plain and for surrounding areas, as well as increased ability to attract private and public funding for habitat conservation, sustainable tourism, and increased management support.  However, opponents of the nomination were concerned that World Heritage Site status would create problems for oil production, grazing rights, off-road recreation, and private property rights.  One point of controversy was a buffer zone around the monument; opponents expected this would adversely affect nearby oil drilling sites.  Some local residents were also fearful of the international organizations that would monitor and report on the monument's adherence to World Heritage treaty obligations, because maintenance of World Heritage status would depend on compliance with the 1972 Convention Concerning the Protection of World Cultural and Natural Heritage, ratified by the United States.  The idea was widespread that the United States would lose sovereignty over the area.

The Wilderness Society eventually decided not to nominate the Carrizo Plain National Monument as a World Heritage Site, as nominations are successful only if they have almost unanimous support.

Oil drilling

While the Carrizo Plain is dotted with dry holes drilled and abandoned by oil companies in decades past, no commercially viable quantities of petroleum have ever been found on the plain itself.  Small quantities of drillable oil have been found south of the Caliente Range, near the Russell Ranch Oil Field, and in the northeast part of the Temblors, abutting the giant McKittrick and Cymric fields.  As the plain is adjacent to the super-giant oil fields of Kern County – the Midway-Sunset Oil Field, third largest in the United States, is on the other side of the Temblor Range – the Carrizo Plain has long been considered to have at least a moderate potential for oil development. As it is separated from the major oil fields by the San Andreas Fault, and the underlying source rock, the Monterey Formation appears not to have been buried at the right conditions of temperature and pressure, and as the stratigraphy has not favored petroleum entrapment, accumulations of oil in economically recoverable quantities have not been found.  Vintage Production, a subsidiary of Occidental Petroleum, owned the mineral rights to 30,000 of the monument's .  When oil prices spiked in 2007, Vintage notified the U.S. Bureau of Land Management (BLM) of its intentions to find out if oil is contained in the Carrizo Plain. The mineral rights owned by Vintage pre-exist the monument's creation by President Bill Clinton in 2001. The BLM approved an oil well and pipeline project in the Russell Ranch Oil Field within the monument in 2018, but withdrew it after Los Padres ForestWatch and the Center for Biological Diversity filed objections citing the potential for oil spills, air pollution and harm to wildlife, among other environmental concerns. The BLM approved the project in 2020 after their analysis showed that the new well posed no undue health or safety concerns, had no significant impacts to the environment and was consistent with management directives for the monument. An agreement was reached in 2022 over a lawsuit against the BLM filed by the conservation groups in 2020. The BLM issued an order to E&B Natural Resources to permanently close and remove 11 long-dormant oil wells, return the oil pads and more than  of access roads to natural conditions, as well as removing pipelines, powerlines and other infrastructure from within the monument.

Solar power

The remote Carrizo Plain's status as one of the sunniest places in the state was exploited by the solar power industry from 1983 to 1994. This was by far the largest photovoltaic array in the world, with 100,000 of the  photovoltaic arrays producing 5.2 megawatts at its peak.  The plant was originally constructed by the Atlantic Richfield oil company (ARCO) in 1983. During the 1979 energy crisis ARCO became a solar energy pioneer, manufacturing the photovoltaic arrays themselves. ARCO first built a 1 megawatt pilot operation, the Lugo plant in Hesperia, California, which is also now closed. The Carrizo Solar Corporation, based in Albuquerque, New Mexico, bought the two facilities from ARCO in 1990, but the price of oil never rose as was predicted, so the solar plant never became competitive with fossil fuel-based energy production. Carrizo Solar sold its electricity to the local utility for between three and four cents a kilowatt-hour, while a minimum price of eight to ten cents a kilowatt-hour would have been necessary in order for Carrizo to make a profit. Another photovoltaic facility was planned for the site by the Chatsworth Utility Power Group; with an output of 100 megawatts, it would have been many times larger than the existing facility, but the facility never got off the drawing board. The Carrizo Solar Company dismantled its  facility in the late 1990s, and the used solar panels are still being resold throughout the world.

In October 2007, the Palo Alto company Ausra, doing business as Carrizo Energy, filed an application for a 177 MW (peak) Carrizo Energy Solar Farm (CESF) on  adjacent to the previous ARCO site. Instead of photovoltaic cells (as used by ARCO), however, Ausra will use Fresnel reflectors that concentrate solar energy onto pipes in a receiver elevated above the ground. The concentrated solar energy boils water within a row of specially coated stainless steel pipes in an insulated cavity to produce saturated steam. The steam produced in the receivers is collected in a series of pipes, routed to steam drums, and then to the two turbine generators. Steam used by the steam turbines is condensed into liquid water and then returned to the solar field. Electricity from the steam generators will be used in San Luis Obispo county. Local opposition to some solar farm proposals centers on concerns about height above grade, noise and heat plume.

The solar field would have operated daily from sunrise to sunset. Typical operating hours for the CESF would have been approximately 13 hours per day, or an average of 4,765 hours per year. In November 2009, the project was canceled.

On August 14, 2008, Pacific Gas and Electric Company announced agreements to buy the power from two proposed photovoltaic plants in the Carrizo Plain, Topaz Solar Farm and High Plains Ranch, with a combined peak power of 800 MW. If built, these will be the largest photovoltaic plants in the world.

As of November 2014 Topaz Solar Farm is operational, with peak power of 550 MW.

California Valley Solar Ranch opened in 2013.

Grazing

Few issues regarding the CPNM have been as controversial as grazing.  The internal dispute in the Bureau of Land Management created national headlines when Marlene Braun, the first Monument Manager of the CPNM, died by suicide in 2005. An investigative article by Los Angeles Times reporters Julie Cart and Maria LaGanga revealed that Braun discussed grazing extensively in correspondence just before her death. The proclamation for the Carrizo Plain National Monument addressed grazing, but its language is similar to that found in most similar proclamations. The proclamation directed BLM to manage grazing in accordance with existing laws and regulations. Braun chose to allow Taylor Grazing Act allotments to expire and replaced them with free use permits. This action was opposed both by many ranchers and Braun's field office supervisor, Ron Huntsinger. Her practice, which would allow BLM to set stocking rates each season as opposed to guaranteeing stocking rates for ten-year periods, was contrary to the desires of the Department of the Interior under President George W. Bush. Bakersfield District Office Manager Ron Huntsinger was brought in to oversee a continuation of the Taylor Grazing Act permit system. Braun and Huntsinger clashed repeatedly and Braun faced the prospect of stiff penalties for insubordination at the time of her death. The LA Times, in a follow-up article by Julie Cart, said, "What began as a policy dispute – to graze or not to graze livestock on the fragile Carrizo grasslands – became a morass of environmental politics and office feuding that Braun was convinced threatened both her future and the landscape she loved." The monument manager's suicide brought "into stark focus the difficulty BLM managers had in trying to balance the demands of providing protection in accordance with the proclamations and balancing the multiple use mandate of FLPMA."

See also
List of national monuments of the United States
List of National Historic Landmarks in California
National Register of Historic Places listings in San Luis Obispo County, California

References

External links

 Carrizo.org: The Friends of the Carrizo Plain
USGS: Carrizo Plain National Monument – 3D photographic tour featuring regional geology.
 The Nature Conservancy: Carrizo Plain
 April 16, 2009 The Santa Barbara Independent — story on the Carrizo Plain
 Despite being located less than 130 miles from downtown Los Angeles, few Americans have heard of Carrizo Plain – BBC
 Suicide Casts a Shadow on Conservation Battle – Los Angeles Times

Valleys of California
Grasslands of California
Plains of the United States
Valleys of San Luis Obispo County, California
Valleys of Kern County, California
National Monuments in California
National Historic Landmarks in California
National Register of Historic Places in San Luis Obispo County, California
Natural history of San Luis Obispo County, California
Protected areas of Kern County, California
Protected areas of San Luis Obispo County, California
California Coast Ranges
Temblor Range
Protected areas established in 2001
2001 establishments in California
Campgrounds in California
Geology of California
Bureau of Land Management areas in California
Units of the National Landscape Conservation System
Historic districts on the National Register of Historic Places in California

Carrizo Plain


The blue shark (Prionace glauca) is a species of requiem shark. It has a slim, smooth-looking body with large eyes, and a long, cone-shaped snout. The dorsal surface is a dark blue colour, and the belly is white.

The largest blue sharks can reach lengths of up to 3.8 metres, and weigh as much as 206 kg. The shark is found worldwide in temperate and tropical waters. They range from the surface to as deep as 350 metres, and prefer water with the temperature of 7 to 16 °C.

Description

The blue shark has a slim, smooth-looking body with large eyes, and a long, cone-shaped snout that is longer than the width of its mouth. It has extremely long, pointed pectoral fins. The dorsal fin is moderate in size. It is closer to the pelvic fins than to the pectoral fins. The blue shark's name comes from its distinct dark blue dorsal surface, and bright blue sides. The belly is white. The colours of the blue shark help it to camouflage in the open ocean. The largest blue shark on record measured 3.8 metres (12.5 feet), but they are rumored to get as large as 6.1 metres (20 feet). Males reach maturity at the ages of 4–5 years, when they are at the lengths of between 1.8-2.8 metres (6-9.2 feet). Females mature at slightly older ages from 5–6 years, when they are at the lengths of between 2.2-3.2 metres (7.2-10.5 feet). The largest blue sharks range in weights from 204–206 kg (450-454 pounds).

Habitat
Blue sharks are found worldwide, in temperate and tropical waters. They are a pelagic species that rarely comes near shore. They have been known to frequently swim to inshore areas around oceanic islands, and locations where the continental shelf is narrow. In the western Atlantic they can be found from Newfoundland, Canada to Argentina. In the eastern Atlantic they range from Norway to South Africa, including the Mediterranean. In the Indian Ocean, they range from South Africa to Indonesia. In the western Pacific they are found from Japan to New Zealand. In the eastern Pacific, Blue sharks range from the Gulf of Alaska to Chile.

Being a pelagic species, the shark's habitat consists of open ocean areas, from the surface to 350 metres (1,148 feet) in depth. They prefer cooler water ranging from 7 to 16 °C (45-61 °F) in temperature. They are known to swim in water with the temperature of 21 °C (70 °F) or greater. When in the tropics, the shark usually swims to deeper water with cooler temperatures. This is common in the tropical Indian Ocean, where the majority of Blue sharks are found at depths of 80–220 metres (263–722 feet), where water temperatures range from 12-25 °C (54-77 °F). In the Pacific, at latitudes between 20°N and 50°N, they are known to migrate to higher latitudes during the summer and lower latitudes during the winter. Their populations remain constant throughout the year between 20°N and 20°S latitude.

Behaviour

The blue shark has one of the largest ranges in terms of depths of the water. They can be found from the surface to the bottom. This type of adaption makes it easy for them to be able to find food. Blue sharks are known to migrate thousands of miles for food and for mating. This species of shark often is not found alone. Instead, they form groups based on their gender and on their size. They are often referred to as the "Wolves of the Sea" due to the complex levels of hierarchy that they form within their groups which highly reflects the behaviour of wolves. Due to their territorial instincts and their aggressive behaviours, divers have to be very careful around them. Many of the filmings of these sharks have been done with the divers in cages for the divers' own personal safety.

Feeding
The majority of the blue shark's diet consists of invertebrates such as squid, cuttlefish, and pelagic octopus, and bony fish such as herring and sardines. They also feed on various types of sea birds, crustaceans such as lobster, crab, and shrimp, and they also feed on carrion.

They are very opportunistic when it comes to hunting. They have been known to feed on almost anything that they can find, including prey items which they can find in large numbers such as shrimp. They have been known to feed until they actually can not eat any more. Since they feed on almost anything that they can find, they have been known to feed on garbage and rubbish such as plastic and rubber tires. This can result in the shark falling ill, and even dying.

Reproduction
Blue sharks are viviparous, with the males maturing at the age of 4-5, and females reaching maturity at the age of 5-6. The gestation period lasts from 9 to 12 months. During mating, the males have been known to bite the females, but their thick skin is believed to stop any pain. Pups are 41 to 50 cm (16 to 20 inches) long at birth, with females giving birth to 4-135 pups at a time, but the number of pups depend on the size of the female, with larger females giving birth to more pups. Blue sharks live to up to 20 years.

Predators
Predators of the blue shark include the California sea lion and larger sharks such as the shortfin mako shark, and the great white shark.

Human interaction
Recreationally, blue sharks are considered a sport fish, and large individuals provide a challenge for fishermen. Most commercially caught blue sharks are considered bycatch.  It is estimated that 10 to 20 million are killed each year, possibly having a negative impact on world populations. The salmon, mackerel, and sardine fisheries are affected by Blue shark predation on catches, and entanglement in nets. The fins of blue sharks are sold to Asian markets and are used to make shark-fin soup.

Having been known to attack humans and boats, blue sharks are considered to be a dangerous species. Twelve unprovoked attacks and four boat attacks have been documented by the International Shark Attack File (ISAF). Three documented attacks resulted from air or sea disasters. There are several accounts where Blue sharks attacked shipwrecked sailors floating in the open ocean. The blue shark sometimes circles swimmers or divers for up to fifteen minutes or more. While not overly aggressive, it is not a timid shark, and needs to be approached with caution, especially if it has been circling, since it may attempt to bite.

Conservation
Although blue sharks are among the most abundant, widespread, and fast growing shark, they are one of the most heavily fished sharks in the world. With an estimated 10 to 20 million individuals caught and killed each year, there is concern not only about what this is doing to Blue shark populations, but also about the effect the removal of such an important predator might have on the oceanic ecosystem. Blue sharks are one of the most important species in the international shark-fin trade. However, their meat, while eaten in a few countries, is not very popular. The blue shark is listed as Near Threatened by the IUCN.

References

Other websites

 ARKive - Images and movies of the blue shark (Prionace glauca)
 Canadian Shark research laboratory
 BBCNews - 'Jaws' comes to a US beach 3 August 2010.
 BBCNews - Footage of shark which closed New Quay (Wales) beach 8 August 2012.

Sharks

Blue shark


The Nantucket Whaling Museum is a museum located in Nantucket, Massachusetts. It is run by the Nantucket Historical Association. The Whaling Museum is the flagship site of the Nantucket Historical Association's fleet of properties.

Restored in 2005, the Nantucket Whaling Museum has an expanded exhibit and program space that connects the 1847 Hadwen & Barney Oil and Candle Factory and the 1971 Peter Foulger Museum. The new structure includes the Gosnell Hall Whale Hunt Gallery, where a 46 foot (14 meter) long sperm whale skeleton is suspended from the ceiling. The Hadwen & Barney Oil and Candle Factory, featuring the massive lever press, is interpreted as an industrial site where the complicated process of refining oil and making spermaceti candles is explained, along with the other Nantucket industries that arose from the whaling era. Eleven galleries and exhibit spaces featuring artifacts and art pertaining to Nantucket life, art, and ideas are on display.

In 2008, the Whaling Museum received accreditation from the American Association of Museums. The museum was reaccredited in 2017.

History
William Hadwen and Nathaniel Barney were partners in a whale-oil manufacturing firm on the island in the mid-19th century, Hadwen & Barney. In 1848, they purchased the oil and candle factory building on Broad Street at the head of New North Wharf (now Steamboat Wharf) built by Richard Mitchell & Sons in 1847, a year after the Great Fire swept through the area. The Greek Revival-style industrial building (similar to the Thomas Macy Warehouse on Straight Wharf) was originally the core of a complex of buildings devoted to oil processing and candle manufacturing, supplying oil for street lamps in London and Paris and lighthouses along the Atlantic coast of the United States.

After the local whaling industry failed, the last whaling ship sailed from Nantucket in 1869, the building was used as a warehouse, and much later as an antiques shop. In 1929, it was purchased by the Nantucket Historical Association to house a collection of whaling artifacts donated by Edward F. Sanderson, a Congregational minister. The Whaling Museum opened in the Hadwen & Barney Oil and Candle Factory in 1930, with Sanderson's collection of whaling implements and other material relating to the industry displayed in the refinery building. Harpoons, lances, blubber hooks, cutting spades, and a whaleboat fitted out for action were enlivened with the whaling tableaux and commentary of "custodian" George Grant.

The collections of the NHA continued to expand in the twentieth century. While the Whaling Museum featured the industry that made Nantucket an internationally recognized name in the eighteenth and nineteenth centuries, the Fair Street Museum showcased artifacts that told the story of island life, and the NHA's house museums interpreted domestic life during successive historical eras. Space to preserve and exhibit the relics of an earlier age was always at a premium, but Admiral William Mayhew Folger, a descendant of early settler Peter Foulger, left a bequest to the NHA in 1929 that honored his ancestor. He specifically required the NHA to use the funds from his bequest to construct a building similar to the Coffin School, a Greek Revival-style brick building built on Winter Street in 1852 with funds donated by Sir Isaac Coffin, a British admiral descended from Tristram Coffin. Admiral Folger's gift was received in 1968, after the death of his last surviving beneficiary, and following his wishes, the building at the corner of Broad and North Water streets was completed in 1971, providing new exhibit halls, a library room, office space, and more room to store collections.

The NHA library and artifact collections were housed in their own dedicated buildings in the late twentieth and early twenty-first centuries, freeing up the Broad Street compound for improvement. A new museum was designed, incorporating the 1847 Hadwen & Barney Oil and Candle Factory and the 1971 Peter Foulger Museum on the opposite corner of the block as part of a new site that bridged the two buildings with exhibit and program space, including Gosnell Hall, where a forty-foot-long sperm-whale skeleton is suspended from the ceiling. The Hadwen & Barney Oil and Candle Factory, featuring the massive lever-press, is interpreted as an industrial site where the complicated process of refining oil and making spermaceti candles is explained. New exhibition spaces extend above and around Gosnell Hall, including a scrimshaw and decorative arts gallery and galleries for changing exhibits about Nantucket life, arts, and ideas.

See also
 List of maritime museums in the United States

References

External links

Institutions accredited by the American Alliance of Museums
Museums established in 1929
Whaling museums
Museums in Nantucket, Massachusetts
Tourist attractions in Nantucket, Massachusetts
Maritime museums in Massachusetts

Nantucket Whaling Museum