During spring and summer 2019, as crews excavated for the foundation of the new Bonney Science Center, they removed a stunning amount of ancient blue-gray marine clay — more than 10,000 cubic yards, according to an estimate from subcontractor Gendron & Gendron.
We watched captivated as excavating machines scooped and scraped the clay, all clingy, sculptural, and glistening like unappetizing Jell-O. For weeks on end, a procession of G&G dump trucks arrived empty at the Campus Avenue site, across from Carnegie Science, and drove away full of clay.
We found it remarkable, but for G&G, as for earthwork contractors in much of Maine, it was no big whoop.
Likewise unsurprising to the construction team was the behavior of the clay left behind in the ground, which complicated preparations for laying the science center’s foundation — in what was just another installment of the complications clay has caused for the people who build and maintain facilities at Bates.
Still, in an ode to the transformative power of a 2,000-degree kiln, clay will soon find redemption at Bates. When it’s time to start covering the science center’s concrete walls, the college will look to Morin Brick Co., which will make the bricks for the job from its very own clay, mined across the river in Auburn.
The Morin mine and the Bonney site are parts of the glaciomarine clay layer that geologists call the Presumpscot Formation. Thousands of years old, the formation extends from Maine’s coast well inland, as far north as Millinocket.
(The formation was named in 1959 by a Yale doctoral student. Hurrying to finish his geology dissertation, he chose the clay-banked Presumpscot River, in southern Maine, for the formation’s namesake after his first choice, “Portland,” was rejected by his professors as being overused.)
Along with Maine’s many ponds and its rounded-off mountains, the Presumpscot Formation is a product of the Pleistocene Ice Age. About 35,000 years ago, according to the Maine Geological Survey, the Laurentide ice sheet began expanding into New England. At its largest, the sheet covered all of Canada and parts of the U.S. It grew thick enough to conceal Maine’s highest mountain, Katahdin, which stands nearly a mile above sea level.
So how does a glacier make clay? Friction is part of the answer. As the ice sheet advanced and retreated over time, it ground up and carried away whatever got in its path, even bedrock, which included feldspars, micas, and quartz. The smallest bedrock particles were fated to become clay. (The U.S. Geological Survey categorizes as clay those particles smaller than .002 millimeters, which are too small to see without a strong microscope.)
And the other clay-making thing the glacier did was melt. In our region, the ice sheet reached its maximum extension near today’s Georges Bank fishing ground about 20,000 years ago. Then, as the climate warmed, the retreat began, a slo-o-o-w melting back over thousands of years.
Glacial meltwater washed away the rock particles the ice had picked up during its advance. Over the centuries, these and other detritus liberated from the ice sheet flowed into the sea and settled on the seafloor — which was far inland from the present coastline. That’s because the unimaginable weight of the glacier, in a process called isostatic depression, smushed the land beneath it down to levels that were hundreds of feet well below current elevations.
Around 14,000 years ago, explains Bates geologist Mike Retelle, the meltwater was entering the sea at a delta at the south end of today’s Lake Auburn. (Retelle and UMaine geologist Thomas Weddle co-edited a book on Maine’s postglacial history.)
“Gracelawn Cemetery is the top of that delta, so if you’d been able to stand on the shoreline there, you’d be looking at kind of a fiord environment,” with water surrounded by sharply higher land, Retelle explains.
Much of the region otherwise was submerged, including the low-lying portions of Bates — that is, virtually all of campus — and the neighborhood. At the sea’s highest stand, Retelle estimates, the Bonney site was under 100 feet of seawater. And all the while, sand, silt, and clay were washing in with the meltwater and settling right where Bates and other institutions would later want to build things. (The nerve!)
One indication that Presumpscot Formation clay is sited on an ancient seabed, as opposed to some lake bottom, is the presence of preserved sea animals, including marine mollusk shells from the genus Yoldia, specimens of which turned up at the Bonney site during a June visit by Retelle, Beverly Johnson, and other geology faculty (a shell will be carbon-dated). In Augusta, the Maine State Museum has remains of a walrus and a mammoth found elsewhere in Maine clay.
The dynamics of this whole business get confusing. Being depressed in an isostatic sort of way, the land surface was much lower during the glacier’s reign — but so was sea level, because so much water was captive in glaciers around the world. As that water was released, sea levels rose. But so did land elevations — rebounding as the weight of the ice sheet went away. Today, the science center site is about 250 feet above sea level.
Maine has a longstanding love-hate relationship with Presumpscot Formation clay. In the “I Love PF Clay” column, Maine ceramicists make plates and pots from it. In addition, its cohesiveness makes it useful for capping defunct landfills. (And for water retention in Lake Andrews, whose floor, beneath the duck deposits, is marine clay.)
Of course, as mentioned above and below, Maine clay generally makes good bricks. (Morin adds a bit of sand to stabilize its formula.) In the 19th century, brickyards abounded in Maine. According to the Bangor Daily News, the town of Brewer alone had 18 brickyards in the 1870s.
And the “Hate” column? While Presumpscot clay goes into bricks that are good to build with, it’s not so swell as a substance to build upon. Compressed by the weight of a building, highway overpass pier, etc., a clay layer is prone to settling, and unpredictably so. While adding a frisson of adventure to your building project, these qualities often necessitate time-consuming and expensive “soil improvements.”
Prior to the construction of Lane Hall, in 1963, President Charles Franklin Phillips reported to the trustees that “[W]e swallowed hard when informed that the earth formation on the proposed site is such that 144 piles” were needed to support the building’s foundation. Phillips doesn’t say “clay,” but we’re thinking he meant clay.
During site preparation for Kalperis Hall, a couple blocks down the clay deposit from Bonney Science, an initial round of injected soil reinforcements, each resembling a stack of doughnuts, proved inadequate. A second round used a different approach, known as GeoConcrete Columns, which created underground piers with a bulbous, onion-shaped base.
Bonney Science itself, being constructed on clay that’s 50 feet or so thick (thicknesses of 200 feet have been documented in the Presumpscot Formation) required more than 200 so-called pipe piles to stabilize the soil.
“Without that layer of clay, we likely wouldn’t have needed to drive piles,” says Chris Streifel, the Facility Services project manager overseeing the Bonney and previously the Kalperis–Chu Hall projects. “It’s definitely made life more challenging. It’s mucky, messy, and slippery. It’s not a fun substance to work with in general, but that’s the nature of the business.”
Clay is the font of other dubious blessings. It makes a poor bed for parking lots, steam vaults, etc., which necessitates replacing it with more stable soils as part of infrastructure makeovers. Plants don’t thrive in clay, so grounds crews planting a tree or shrub in a new spot will generally “want to put in some good organics and soil in place of clay to get things to root,” says Jay Phillips, director of Facility Services operations.
Then there’s drainage (not). Spring rain and snowmelt can collect in long-lasting puddles on campus that are big enough for the ducks to enjoy. Garcelon Field was infamously damp and mucky until drainage infrastructure was installed, in 1986. “Only the muddy condition of the field, which made it impossible to kick a goal from a touchdown, gave the victory” to the University of Maine, The Bates Student griped after a 7-6 Bobcats loss in 1912.
But once water permeates clay, the clay wants to keep it. So Presumpscot Formation clay tends to be wet. Wet clay is plastic (hence the instability) and it’s also, weirdly, both slippery and sticky, depending on which condition will cause the most inconvenience, especially to the people who work closely with it on a job site every day. A Google search on “removing clay from clothes” generated 35,500,000 results.
A smaller but more meaningful number is the estimated count of brick — brick professionals don’t pluralize with “s” — needed to sheathe the walls of the Bonney Science Center: 180,000, project manager Streifel estimates.
The clay for those bricks (sorry, we need the “s”) is coming out of a mine in a field near a stand of trees in Auburn’s Danville neighborhood. And not far from the field is the Morin Brick Company plant.
On a July morning we met Morin’s director of sales and marketing, Jason Lachance, whose family once owned the company and who started in the brickyard when he was 17. Our visit included a drive past the lot where freshly mined clay is rototilled, dried, and stored in heaps; and a distant look at the mine itself.
We couldn’t get close because the dirt road was paved with rejected bricks that keep heavy machinery from bogging down but are too jagged for passenger vehicles.
Two employees of Shaw Brothers Construction, an earthworks contractor in Gorham, Maine, work the open-pit clay mine for Morin. “It’s about 86 acres,” Lachance said. “We’ve been mining there now for approaching 30 years,” with perhaps another five to 10 years of life left in the deposit. Given the need to find clay matching its established processes and customer interests, Morin is already taking steps to secure its next clay source. (The National Brick Research Center, at Clemson University, assays prospective clays for Morin.)
Founded in 1912 and now Maine’s last maker of clay brick, Morin also bills itself as North America’s last manufacturer of “waterstruck” brick. Where most brick is extruded, like dough from a pasta machine, waterstruck is made with the age-old technique of pressing soft wet clay into wooden molds. (“Waterstruck” refers specifically to the use of a jet of water to knock bricks out of the molds. Morin makes extruded as well as waterstruck.)
The many Bates buildings cloaked in Morin waterstruck include the 2008 Commons and, on Campus Avenue, Chu and Kalperis halls, for which the company devised an extra-long brick.
“No two waterstruck brick are exactly alike,” Lachance explained. “That irregularity and random event, if you will, combined with a manipulation of flash in the kiln” — extra-hot flare-ups — “yield some wonderful ranges of colors. The Bates campus is a perfect example of what can be accomplished with waterstruck brick.”
Not to mention what can be accomplished with waterlogged clay.
Katika majira ya kuchipua na majira ya joto ya 2019, kama wafanyakazi kuchimbua kwa ajili ya msingi wa mpya Bonney Science Center, wao kuondolewa kiasi stunning ya kale bluu-kijivu bahari udongo - zaidi ya 10,000 mita ya mraba, kulingana na makadirio kutoka subcontractor Gendron & Gendron. Tulitazama kwa mshangao huku mashine za kuchimba zikichimba na kuchimba udongo, uliokuwa wenye kunata, wenye umbo la sanamu, na wenye kung'aa kama jelly-o isiyo na ladha. Kwa wiki kadhaa, msafara wa malori ya G&G ulifika tupu kwenye eneo la Campus Avenue, kinyume na Chuo Kikuu cha Sayansi cha Carnegie, na kuondoka wakiwa wamejaa udongo. Kwa kweli, hii ni ya kushangaza, lakini kwa G&T, ambayo ni kampuni ya ujenzi wa ardhi ya Maine, haikuwa kubwa. "Hivyo vile, haishangazi timu ya ujenzi tabia ya udongo iliyobaki chini, ambayo ilifanya maandalizi ya kuweka msingi wa kituo cha sayansi kuwa magumu, katika kile ambacho kilikuwa tu awamu nyingine ya ugumu udongo umesababisha kwa watu ambao wanajenga na kudumisha vifaa katika ""Bates.""" Hata hivyo, katika wimbo wa kuabudu nguvu ya kubadilisha ya tanuru ya digrii 2,000, udongo utapata ukombozi katika Bates. Wakati wa kuanza kufunika kuta za saruji za kituo cha sayansi, chuo kikuu kitatafuta kampuni ya Morin Brick, ambayo itafanya matofali kwa kazi hiyo kutoka kwa udongo wake mwenyewe, uliochimbwa ng'ambo ya mto huko Auburn. Mgodi wa Morin na eneo la Bonney ni sehemu ya safu ya udongo wa glaciomarine ambayo wataalamu wa jiolojia huita Muundo wa Presumpscot. Mimea hiyo yenye umri wa maelfu ya miaka inaenea kutoka pwani ya Maine hadi kaskazini mwa nchi, hadi Millinocket. Jina la kundi hilo lilitokana na mwanafunzi wa shahada ya kwanza wa chuo kikuu cha Yale mwaka 1959. Alipokuwa akimalizia kwa haraka dissertation yake ya jiolojia, alichagua Mto Presumpscot, kusini mwa Maine, kwa ajili ya jina la malezi baada ya chaguo lake la kwanza, <unk>Portland,<unk> lilikataliwa na maprofesa wake kwa kuwa linatumiwa kupita kiasi.) Pamoja na vidimbwi vingi vya Maine na milima yake iliyozungukwa, Mkusanyiko wa Presumpscot ni bidhaa ya Enzi ya Barafu ya Pleistocene. Kulingana na utafiti wa utafiti wa kijiolojia wa Maine, barafu ya Laurentide ilianza kuenea hadi New England. Wakati wa ukubwa wake, karatasi hiyo ilifunika Kanada yote na sehemu fulani za Marekani Mto huo ulikua kuwa mzito vya kutosha kuficha mlima mrefu zaidi wa Maine, Katahdin, ambao unasimama karibu kilometa moja juu ya usawa wa bahari. Kwa hiyo, barafu hutokezaje udongo? Mvutano ni sehemu ya jibu. Kwa muda, barafu hiyo ilizidi kupanuka na kurudi nyuma, ikisababisha kila kitu kilichokuwa njiani, hata miamba, ikiwa ni pamoja na feldspars, mica, na quartz. Chembe ndogo-ndogo za mwamba zilikuwa zimepangwa kuwa udongo. "Kifungu cha utafiti wa kijiolojia cha Marekani (U.S. Geological Survey) kinasema kwamba udongo ni ""chembe ndogo sana ambazo haziwezi kuonekana bila kutumia darubini.""" Jambo jingine ambalo lilifanya barafu hiyo iwe na udongo ni kuyeyuka. Katika eneo letu, barafu ilifikia urefu wake mkubwa karibu na eneo la uvuvi la leo la Georges Bank miaka 20,000 iliyopita. Kisha, hali ya hewa ilipopungua, mvua hiyo ilianza kuyeyuka polepole kwa maelfu ya miaka. Maji ya barafu yaliyokuwa yameyumbika yaliondoa chembechembe za mwamba ambazo barafu hiyo ilikuwa imechukua wakati wa kusonga mbele. Kwa karne nyingi, vipande hivyo na vingine vilivyotokana na barafu vilimwagika baharini na kukaa kwenye sakafu ya bahari - ambayo ilikuwa mbali na pwani ya sasa. Hiyo ni kwa sababu uzito usioweza kufikiriwa wa barafu, katika mchakato unaoitwa kushuka kwa isostatic, ulipunguza ardhi chini yake hadi viwango ambavyo vilikuwa mamia ya futi chini ya urefu wa sasa. "Mimi na Mike Retelle, mtaalamu wa jiolojia wa Bates, tulikuwa tukifikiria jinsi maji ya barafu yalivyopatikana katika eneo la delta la kusini mwa Ziwa Auburn.""" (Retelle na mtaalamu wa jiolojia wa UMaine Thomas Weddle walishirikiana kuhariri kitabu kuhusu historia ya Maine baada ya barafu.) "Gracelawn Cemetery ni juu ya delta hiyo, hivyo kama ungeweza kusimama kwenye pwani huko, ungeangalia aina ya mazingira ya fjord, "na maji kuzungukwa na ardhi ya juu sana, Retelle anaelezea. Sehemu kubwa ya mkoa vinginevyo ilikuwa imezama, ikiwa ni pamoja na sehemu za chini za Bates - ambayo ni, karibu chuo kikuu chote - na jirani. Katika eneo la juu zaidi la bahari, Retelle anakadiria, eneo la Bonney lilikuwa chini ya futi 100 za maji ya bahari. Wakati huohuo, mchanga, matope, na udongo ulifyonzwa na maji yaliyokuwa yameyuka na kukaa mahali ambapo baadaye Bates na mashirika mengine yalipenda kujenga vitu. (Uchungu!) "Kuna dalili kwamba udongo wa Presumpscot Formation unapatikana kwenye sakafu ya bahari ya kale, kinyume na baadhi ya chini ya ziwa, ni uwepo wa wanyama wa baharini waliohifadhiwa, ikiwa ni pamoja na makombora ya mollusk ya baharini kutoka jamii ya Yoldia, ambayo sampuli zake zilipatikana katika tovuti ya Bonney wakati wa ziara ya Juni na Retell, Beverly Johnson, na kitivo kingine cha jiolojia. """ Katika Augusta, Jumba la Makumbusho la Jimbo la Maine lina mabaki ya walrus na mammoth yaliyopatikana mahali pengine katika udongo wa Maine. Hali ya biashara hii yote inakuwa yenye kutatanisha. Kwa kuwa ilishuka kwa njia ya isostatic, uso wa ardhi ulikuwa chini sana wakati wa utawala wa barafu - lakini ndivyo ilivyokuwa na kiwango cha bahari, kwa sababu maji mengi yalikuwa yamekamatwa katika barafu ulimwenguni kote. Maji hayo yalipokuwa yakitolewa, kiwango cha bahari kiliongezeka. Lakini ndivyo vile vilivyoongezeka vya ardhi - vikirudia tena wakati uzito wa barafu ulipoondoka. Kituo cha Sayansi cha New York ni juu ya mita 250 juu ya usawa wa bahari. Maine ina uhusiano wa muda mrefu wa upendo na chuki na udongo wa Muundo wa Presumpscot. Katika safu ya "Ninapenda PF Clay", wasanii wa kauri wa Maine hutengeneza sahani na sufuria kutokana nayo. Kwa kuongezea, muunganiko wake hufanya iwe na manufaa kwa ajili ya kufunika mabwawa ya taka yasiyo na matumizi. (Na kwa ajili ya kuhifadhi maji katika Ziwa Andrews, ambalo sakafu yake, chini ya matope ya bata, ni udongo wa baharini.) Bila shaka, kama ilivyotajwa hapo juu na hapa chini, kwa kawaida udongo wa Maine hutokeza matofali mazuri. (Morin anaongeza mchanga kidogo ili kudumisha muundo wake.) Katika karne ya 19, mashamba ya matofali yalienea sana huko Maine. Kulingana na gazeti la Bangor Daily News, mji wa Brewer pekee ulikuwa na viwanda 18 vya kutengeneza matofali katika miaka ya 1870. Na safu ya "Chuki"? Ingawa udongo wa Presumpscot hutumiwa kutengeneza matofali yanayofaa kwa ajili ya ujenzi, si jambo zuri sana la kujenga juu yake. Kwa sababu ya uzito wa jengo, daraja la barabara, na kadhalika, tabaka la udongo huelekea kutiririka, na kwa njia isiyotazamiwa. "Kabla ya ujenzi wa Lane Hall, Rais Charles Franklin Phillips aliripoti kwa wasimamizi kwamba ""Wameumwa sana wakati walipotangazwa kwamba muundo wa ardhi kwenye tovuti iliyopendekezwa ni kwamba nguzo 144 zinahitajika kuunga mkono msingi wa jengo.""" Phillips hasemi "matope", lakini tunafikiri alimaanisha matope. Wakati wa maandalizi ya eneo la Kalperis Hall, mawe kadhaa ya udongo kutoka Bonney Science, mzunguko wa kwanza wa kuimarisha udongo, kila mmoja unafanana na rundo la donuts, ulithibitika kuwa haitoshi. "Mfano wa pili ni ""GeoConcrete Columns"" ambayo ni sehemu ya chini ya ardhi iliyoundwa na msingi wa bulbous." Bonney Science yenyewe, ikiwa imejengwa juu ya udongo wenye unene wa futi 50 au zaidi (unene wa futi 200 umeandikwa katika muundo wa Presumpscot), ilihitaji zaidi ya vijiti 200 vya mabomba ili kuimarisha udongo. "Bila tabaka hilo la udongo, labda hatungehitaji kuendesha vilele", anasema Chris Streifel, meneja wa mradi wa Huduma za Kituo cha Usimamizi wa Bonney na hapo awali miradi ya Kalperis <unk> Chu Hall. Ni dhahiri alifanya maisha changamoto zaidi. Ni chafu, chafu, na laini. Si dutu ya kufurahisha kufanya kazi nayo kwa ujumla, lakini hiyo ni asili ya biashara. Clay ni fonti ya baraka nyingine zenye kutiliwa shaka. Inafanya kitanda duni kwa ajili ya maegesho, vaults mvuke, nk, ambayo inahitaji kubadilisha na udongo imara zaidi kama sehemu ya miundombinu makeovers. Mimea haifanyi vizuri katika udongo, kwa hiyo wafanyakazi wa shamba wanaopanda mti au kichaka katika eneo jipya kwa ujumla "watataka kuweka viumbe bora na udongo badala ya udongo ili kupata vitu kwa mizizi", anasema Jay Phillips, mkurugenzi wa shughuli za Huduma za Kituo. Kisha kuna mifereji ya maji (si). Mvua ya majira ya kuchipua na theluji inaweza kukusanya katika vidimbwi vya muda mrefu kwenye chuo kikuu ambavyo ni kubwa vya kutosha kwa bata kufurahia. Garcelon Field ilikuwa na unyevu na uchafu mpaka mfumo wa mifereji ya maji ulipowekwa mnamo 1986. "Mchezo huo ulichezwa na timu ya Maine, na baada ya kushindwa kwa 7-6 na timu ya Bobcats mwaka 1912.""" Lakini mara tu maji yanapoingia ndani ya udongo, udongo huo hutaka kuushikilia. Kwa hiyo udongo wa Presumpscot Formation huwa na unyevu. Weave ni plastiki (kwa hiyo kutokuwa na utulivu) na pia, kwa kushangaza, ni laini na laini, kulingana na hali ambayo itasababisha usumbufu zaidi, haswa kwa watu ambao hufanya kazi kwa karibu nayo kwenye tovuti ya kazi kila siku. Utafutaji wa Google juu ya "kuondoa udongo kutoka kwa nguo" ulitoa matokeo 35,500,000. "Nambari ndogo lakini yenye maana zaidi ni takriban hesabu ya matofali - wataalamu wa matofali hawajaongeza ""s"" - yanahitajika kufunika kuta za Kituo cha Sayansi cha Bonney: 180,000, ""msimamizi wa mradi Streifel anakadiria." "Kila kitu kinachotumiwa kutengeneza matofali hayo (samaha, tunahitaji ""s"") kinatokana na mgodi ulio katika shamba karibu na mti katika kitongoji cha Danville cha Auburn." Na si mbali na shamba hilo kuna kiwanda cha Kampuni ya matofali ya Morin. "Mwanzoni mwa Julai, tulikutana na mkurugenzi wa mauzo na uuzaji wa Morin, Jason LaChance, ambaye familia yake ilikuwa na kampuni hiyo na ambaye alianza kazi katika kiwanda cha matofali akiwa na umri wa miaka 17.""" Ziara yetu ilitia ndani kuendesha gari kupitia eneo ambapo udongo uliochimbuliwa hivi karibuni huchimbwa, kukaushwa, na kuhifadhiwa katika rundo; na kutazama mgodi huo wenyewe kwa mbali. Hatukuweza kukaribia kwa sababu barabara ya udongo ilikuwa imefunikwa kwa matofali yaliyokataliwa ambayo huzuia mashine nzito kutoka kwenye matope lakini ni yenye miiba sana kwa magari ya abiria. Wafanyakazi wawili wa Shaw Brothers Construction, kampuni ya ujenzi ya ardhi huko Gorham, Maine, wanafanya kazi katika mgodi wa udongo wa wazi wa Morin. "Ni kuhusu ekari 86", Lachance alisema. """Tumekuwa tukichimba madini huko kwa karibu miaka 30 sasa, na labda miaka mingine mitano hadi kumi ya maisha imebaki katika amana hiyo." Kwa kuzingatia haja ya kupata udongo unaolingana na michakato yake iliyowekwa na maslahi ya wateja, Morin tayari inachukua hatua za kupata chanzo chake cha udongo kijacho. (Kituo cha Kitaifa cha Utafiti wa matofali, katika Chuo Kikuu cha Clemson, huchunguza udongo unaotarajiwa kwa ajili ya Morin.) Ilianzishwa mwaka 1912, Morin ni mtengenezaji wa mwisho wa matofali ya udongo wa Maine, na pia inajitangaza kama mtengenezaji wa mwisho wa matofali ya maji ya Amerika Kaskazini. Katika sehemu ambazo matofali mengi hutengenezwa kwa njia ya extrusion, kama vile unga unaotengenezwa kwa mashine ya kutengeneza pasta, matofali hayo hutengenezwa kwa kutumia mbinu ya kale ya kufagia udongo laini na unyevu na kuufanya uwe umbo la mbao. (Waterstruck inahusu hasa matumizi ya mtiririko wa maji kubomoa matofali nje ya mitindo. Morin hufanya extruded kama vile waterstruck.) Majengo mengi ya Bates yaliyofunikwa na maji ya Morin ni pamoja na Commons ya 2008 na, kwenye Campus Avenue, vyumba vya Chu na Kalperis, ambavyo kampuni hiyo ilibuni matofali marefu zaidi. "Hakuna matofali mawili yaliyoathiriwa na maji yanayofanana kabisa", Lachance akaeleza. <unk>Hiyo irregularity na tukio random, kama wewe itakuwa, pamoja na udanganyifu wa flash katika tanuru <unk> <unk> ziada-moto flare-ups <unk> <unk> kuzalisha baadhi ya mbalimbali ya ajabu ya rangi. Chuo cha Bates ni mfano kamili wa kile kinachoweza kutimizwa na matofali yaliyoangushwa na maji. <unk> Bila kutaja kile kinachoweza kutimizwa na udongo uliojaa maji.