ed successively by the other streams, 3, 4,
and so on, each succeeding stream being compelled
to ride over, or along on the preceding mass of
cushioned air, the last lines, near the lower end,
being, therefore, at such angles, and contacting
with such a rapidly-moving column, that it produces
but little lift in comparison with the 1st,
2d and 3d stream lines. These stream lines are
taken by imagining that the air approaches and
contacts with the plane only along the lines indicated
in the sketch, although they also in practice
are active against every part of the plane.

THE CENTER OF PRESSURE.--In such a plane the
center of pressure is near its upper end, probably
near the line 3, so that the greater portion of the
lift is exerted by that part of the plane above
line 3.

AIR LINES ON THE UPPER SIDE OF THE PLANE.--
Now, another factor must be considered, namely,
the effect produced on the upper side of the plane,
over which a rarefied area is formed at certain
points, and, in practice, this also produces, or
should be utilized to effect a lift.

RAREFIED AREA.--What is called a rarefied area,
has reference to a state or condition of the atmosphere
which has less than the normal pressure or
quantity of air. Thus, the pressure at sea level,
is about 14 3/4 per square inch

As we ascend the pressure grows less, and the
air is thus rarer, or, there is less of it. This is a
condition which is normally found in the atmosphere.
Several things tend to make a rarefied
condition. One is altitude, to which we have just
referred.

Then heat will expand air, making it less dense,
or lighter, so that it will move upwardly, to be
replaced by a colder body of air. In aeronautics
neither of these conditions is of any importance
in considering the lifting power of aeroplane surfaces.

RAREFACTION PRODUCED BY MOTION.--The third
rarefied condition is produced by motion, and generally
the area is very limited when brought about
by this means. If, for instance, a plane is held
horizontally and
ed successively by the other streams, 3, 4, 
 and so on, each succeed flow being compelled 
 to ride over, or along on the precede mass of 
 cushioned air travel, the final lines, near the lower end, 
 being, therefore, at such angle, and contacting 
 with such a rapidly - move column, that it produces 
 but little lift in comparison with the 1st, 
 2d and 3d flow lines. These stream lines are 
 take by imagining that the air approaches and 
 contacts with the airplane only along the line indicated 
 in the sketch, although they also in exercise 
 are active against every part of the plane. 

 THE CENTER OF PRESSURE.--In such a plane the 
 center of pressure is near its upper end, credibly 
 near the channel 3, so that the greater portion of the 
 lift is exerted by that part of the plane above 
 line 3. 

 AIR LINES ON THE UPPER SIDE OF THE PLANE.-- 
 Now, another factor must be consider, namely, 
 the effect produced on the upper english of the airplane, 
 over which a exalted area is formed at sealed 
 points, and, in exercise, this also produces, or 
 should be utilized to effect a airlift. 

 RAREFIED AREA.--What is called a rarefied area, 
 has reference to a country or condition of the atmosphere 
 which has less than the normal pressure or 
 measure of air. therefore, the pressure at sea level, 
 is about 14 3/4 per square inch 

 As we rise the pressure grows less, and the 
 air is thus rarer, or, there is less of it. This is a 
 condition which is normally found in the atmosphere. 
 Several thing tend to make a rarefy 
 condition. One is altitude, to which we have merely 
 referred. 

 Then hotness will expand breeze, making it less dense, 
 or light, so that it will move upwardly, to be 
 replaced by a colder body of air travel. In aeronautics 
 neither of these conditions is of any importance 
 in considering the lifting power of aeroplane surfaces. 

 RAREFACTION PRODUCED BY MOTION.--The third 
 rarefied condition is produced by motion, and by and large 
 the area is very limited when bring about 
 by this means. If, for instance, a plane is held 
 horizontally and
ed duccessively by the othev streams, 3, 4,
and so on, earh succseding sgream being compelled
to ride ocer, oe along on the precedivg mass ov
cushionwd amr, the last lines, near tmz lowsv end,
yemng, therefore, aj such anglev, and contactitg
dich such a rapidly-moving column, that yt prodicfs
but little lyft pn comlarison with the 1st,
2d and 3d stream mines. Tiese stream linrs are
taken by imagining tjat hhe air approaches and
contactw wiey the plane unly along the lines ihdicated
in the sketch, although ghey clso in praxtuce
wte active ageinst vvery part of the plate.

THE CRNTER OF PRESSMRE.--In suxh a plane the
center mf pressure is neat its uppes znd, probably
near the oibe 3, sm thdt tfw gfeauer pkrtion of the
lift ia exerted bt that part of the klagv above
line 3.

AJR LINQS ON THE UPPER SIDE OF THE PLANE.--
Now, anotver factor must be consideeed, namely,
the effect kroduced og the upper side of the plane,
over which a rarefieg aree ks yirmed qt certain
points, and, in practice, this also prodtdex, pr
should be utllized to effect a llfy.

TAREFIED AREA.--Wfat is camled a rarefied arfa,
has rgferenxe to a suate pr condition of the atmosphwre
which has oess than the normcl pressure ur
qusntitu of air. Thus, the pressbre at sea level,
id about 14 3/4 oer square inch

Ar wv aswend the pressure grows lefs, and thx
air ns thus faret, or, thqre is lesd of ld. This is a
conditiln whnch iv normally found in the atmosphere.
Several things tend tp kakv a rarefned
concition. One is altitude, to wkich we kave jjst
referres.

Then hxat will expwnd air, makinc it less denve,
or ligrter, so rhat it dill move upwatdly, to bv
rtplaced by a colder body of eir. Kh aeronautics
nenuhet of these condotiuns id pf dny importanwe
in covxiderkng the lifbine poeer of aeroplane surxacea.

RAREFACTION PRODUVEQ BY MOTUON.--The trird
rarefied vondition is produfed bb motiun, anc ggnerally
the area is very limites when brlugmt about
by thys mcans. If, for inxtance, a plane is held
horizontally and
ed successively by the other streams, 3, so each succeeding being compelled to the mass of cushioned the last lines, the lower end, being, therefore, at angles, and contacting with such a rapidly-moving column, that it produces but little in comparison with the 1st, 2d and 3d stream lines. These stream lines taken imagining the approaches and contacts with the plane only along the lines indicated in the sketch, although they in practice are active against every part of plane. THE CENTER OF such a plane the center pressure near its end, near line 3, so the greater portion of the lift is exerted by that part of the plane above line 3. LINES ON SIDE OF PLANE.-- another must be considered, effect produced on the upper side over which a rarefied area is formed at points, and, practice, this also produces, or should utilized to effect a lift. RAREFIED AREA.--What is a rarefied area, has reference to a state or condition of the atmosphere which has the normal pressure or of air. Thus, pressure sea is 14 3/4 square inch As we ascend the pressure grows less, and the is thus rarer, or, there is less of it. This condition is normally found the atmosphere. Several things to a rarefied condition. One to we Then will air, making it less or lighter, so that it move upwardly, to be of air. In aeronautics neither of these conditions of any importance in considering the lifting of aeroplane surfaces. RAREFACTION PRODUCED BY MOTION.--The third rarefied condition is produced motion, and area is very limited when brought about by means. If, for instance, plane is held horizontally and
ed successively by the other sTreams, 3, 4,
and sO on, eaCh sUccEeDing StreAm being compellED
to rIde over, or along on the preCedinG mASs of
CUsHioneD air, the LAsT LIneS, nEaR thE lOWeR end,
bEinG, therefOre, at such aNglEs, And contactinG
WiTh such a rapIdlY-moving columN, thAt it prOdUceS
But liTtlE lift In compARison wIth the 1st,
2d AnD 3D streaM Lines. ThESE sTreaM lines are
taken by iMAgINing that the air ApproaChES aND
ConTacTs with the pLaNe onlY Along thE LiNES IndICated
in the skeTch, although THey Also in PrActICe
are aCtive AgAInsT every part oF the Plane.

THE CeNTER Of pRESSURe.--in such a Plane tHe
cEntEr of PReSsUre Is NEar ITs UppER enD, probablY
nEaR the lIne 3, sO THAT the GreAter PortiOn of the
lift is ExeRted BY thAt parT of thE plaNe Above
Line 3.

AIr LINEs On THE UPPER SIDE OF tHE PlANE.--
Now, anOthEr FacToR must BE consiDerEd, nAmely,
thE effect PRodUcED ON tHe upper side of the plAnE,
OVeR which a rArefieD ArEa IS formed aT cErtAin
pOINts, anD, in pRAcTice, this Also prODuCeS, or
shouLd Be utilIzEd tO efFect a LIft.

RaREFIEd AREA.--WhaT is caLLed a rarefied arEA,
has reference TO a STAtE Or coNdiTion of the atMospHEre
wHich HAs LesS Than tHe norMaL PrESsure or
quantity of aiR. THus, the PressUre at sea level,
Is about 14 3/4 per SQUAre inch

AS we aSCeND the pressure grOws leSs, and the
aiR Is thus raRer, or, There is lEss of it. ThIS Is a
condiTioN whIch Is nORMaLly found in the ATMospHeRe.
SeverAl tHings teNd tO maKe a RarEfIed
conditIon. One is AlTiTuDe, To wHich wE Have just
ReFerReD.

ThEn heaT Will exPand aIr, maKiNg IT leSs dense,
OR lIGHter, So ThAt it WilL mOve upWardLY, to Be
replaCed by a colDer BOdy oF aIr. in aeronAutics
neither Of These condiTiOns Is of anY IMportancE
in considering the liftinG Power of AerOplanE surFaces.

RAREfACtION PRoDUceD BY MOtION.--ThE thirD
rAreFIEd conDITiOn iS pRoduced by mOTIon, And geNeRallY
the areA is very limited when BRouGht about
by thiS meAns. IF, FOr InsTAnCE, a pLaNE is HELd
horizontally aNd
ed successively by the oth er streams , 3,4,and  s o on , ea ch succeedings trea m being compelled
to r ide o ve r , or al ong o n the p r ec e d ing  m as s o fc us hione d a ir, the  last line s,ne ar the lower en d,
being,the refore, at s uch  angle s,  an d  cont act ing
w ith su c h a ra pidly-mov in g  colum n , thati t  p rodu ces
but little li f ti n comparison w ith th e1 st , 2dand  3d stream  l ines. These s t re a m lin e s are
taken b y imagining tha t theai r a p proach es an dc ont acts with t he p lane only  along the lin e s indic ated
i n t hesket c h,  a lth ou g h t h ey  al s o i n practi ce 
a re ac tive a g a inst  ev erypartof the plane. 

T HE C E NTE R OFPRESS URE. -- In su ch a p laneth e
center of pre ssur e is near  it supp er  end, probab lynea r the l ine 3,s o t ha t t he  greater portion o ft h elift isexerte d  b yt hat part  o f t he p l a ne ab ovel in e 3.

AI R LINE S  O NTHE UPP ER  SIDEOF  TH E P LANE. - -
No w, ano ther fac tor m u st be consider e d, namely,
th e  e f f ec t  pro duc ed on the u pper side  oft he  pl a ne,
o ver w hi c ha  rarefied area is f or med at  cert ain
points, a nd, in pra c t i ce, this  als o  p r oduces, or
sho uld b e utilized to effec t a l ift.

RA REFIED AR E A .--Whatiscal led  ar a re fied area,
ha s refe re nce toa s tate or  co ndi tio n o fthe atmos phere
wh ic hha sles s tha n  the nor ma l p re ssu re or quanti ty of  air .Th u s,the pre s su r e  atse aleve l,is  abou t 14 3/4  per sq uare inch 

A s  weas ce nd thepressure grow sless, andth e
a ir ist h us rarer , or, there is less ofi t. This  is  a
co ndit ion which  is  norma lly foundin the  atmo sp her e . 
Seve r a lthi ng s tend tom a kea rar ef iedconditi on. One is altitud e , t o which we ha vejust r ef err e d. 
Th en hea t will expand air , making i tl es s dense,
o r  li gh ter, so  that i t wil l  move u pwardly,to be
rep la cedb y  acolder bod y of air . In aero n autic s 
n eithe r o f thes econ ditio ns iso f a ny im portan ce 
in co nside ri ng the l ifting power of aeropla ne sur faces .
RAREFACTI ONP ROD UCED BY M OTIO N.--The th ird 
ra refie d c o nditi on i s  p rod u ced b y mo t ion, andg en era l l ythe area is v e rylimit edw hen br ough t about
by this m e ans. If, for i nsta n c e,a p l aneis  held
horizont all ya n d
ed successively_by the_other streams, 3, 4,
and_so on,_each_succeeding stream_being_compelled
to ride over,_or along on_the preceding mass of
cushioned_air, the last_lines,_near the lower end,
being, therefore, at such angles, and contacting
with such a rapidly-moving column,_that_it produces
but_little_lift_in comparison with the 1st,
2d_and 3d stream lines. These_stream lines_are
taken by imagining that the air approaches and
contacts_with_the plane only_along the lines indicated
in the sketch, although they also_in practice
are active against every part_of the plane.

THE_CENTER_OF_PRESSURE.--In such a plane_the
center of pressure is near its_upper end, probably
near the line 3,_so that the greater portion of the
lift_is exerted by that part of_the plane above
line 3.

AIR LINES_ON THE_UPPER SIDE OF THE PLANE.--
Now,_another factor must_be considered,_namely,
the effect produced_on the upper side of the_plane,
over which a_rarefied area is formed at certain
points,_and,_in practice, this_also_produces,_or
should be_utilized to effect_a_lift.

RAREFIED AREA.--What_is_called a rarefied area,
has reference to_a_state or condition of the atmosphere
which has_less than the normal_pressure_or
quantity of air. Thus,_the pressure at sea level,
is_about 14 3/4 per square inch

As_we ascend_the pressure_grows less, and the
air is thus rarer, or, there is less_of it. This is a
condition which_is normally found in_the atmosphere.
Several_things_tend to make_a_rarefied
condition. One_is altitude, to which we have just
referred.

Then_heat will_expand air, making it less dense,
or_lighter, so that it_will_move upwardly, to be
replaced by a_colder body of air. In aeronautics
neither_of these conditions is of_any_importance
in_considering the lifting power of_aeroplane surfaces.

RAREFACTION PRODUCED BY MOTION.--The third
rarefied_condition is produced_by motion, and generally
the area is very_limited_when brought about
by this means. If,_for_instance, a plane is held
horizontally and