Theboobylayshereggsonthebarerock；buttheternmakesaverysimplenestwithseaweed。Bythesideofmanyofthesenestsasmallflying-fishwasplaced；whichIsuppose，hadbeenbroughtbythemalebirdforitspartner。Itwasamusingtowatchhowquicklyalargeandactivecrab(Graspus)，whichinhabitsthecrevicesoftherock，stolethefishfromthesideofthenest，assoonaswehaddisturbedtheparentbirds。SirW。Symonds，oneofthefewpersonswhohavelandedhere，informsmethathesawthecrabsdraggingeventheyoungbirdsoutoftheirnests，anddevouringthem。
Notasingleplant，notevenalichen，growsonthisislet；yetitisinhabitedbyseveralinsectsandspiders。Thefollowinglistcompletes，Ibelieve，theterrestrialfauna：afly(Olfersia)livingonthebooby，andatickwhichmusthavecomehereasaparasiteonthebirds；asmallbrownmoth，belongingtoagenusthatfeedsonfeathers；abeetle(Quedius)andawoodlousefrombeneaththedung；andlastly，numerousspiders，whichIsupposepreyonthesesmallattendantsandscavengersofthewater-fowl。Theoftenrepeateddescriptionofthestatelypalmandothernobletropicalplants，thenbirds，andlastlyman，takingpossessionofthecoralisletsassoonasformed，inthePacific，isprobablynotcorrect；Ifearitdestroysthepoetryofthisstory，thatfeatheranddirt-feedingandparasiticinsectsandspidersshouldbethefirstinhabitantsofnewlyformedoceanicland。
Thesmallestrockinthetropicalseas，bygivingafoundationforthegrowthofinnumerablekindsofseaweedandcompoundanimals，supportslikewisealargenumberoffish。Thesharksandtheseamenintheboatsmaintainedaconstantstrugglewhichshouldsecurethegreatershareofthepreycaughtbythefishing-lines。IhaveheardthatarockneartheBermudas，lyingmanymilesoutatsea，andataconsiderabledepth，wasfirstdiscoveredbythecircumstanceoffishhavingbeenobservedintheneighbourhood。
FERNANDONORONHA，Feb。20th——AsfarasIwasenabledtoobserve，duringthefewhourswestayedatthisplace，theconstitutionoftheislandisvolcanic，butprobablynotofarecentdate。Themostremarkablefeatureisaconicalhill，aboutonethousandfeethigh，theupperpartofwhichisexceedinglysteep，andononesideoverhangsitsbase。Therockisphonolite，andisdividedintoirregularcolumns。Onviewingoneoftheseisolatedmasses，atfirstoneisinclinedtobelievethatithasbeensuddenlypushedupinasemi-fluidstate。AtSt。Helena，however，Iascertainedthatsomepinnacles，ofanearlysimilarfigureandconstitution，hadbeenformedbytheinjectionofmeltedrockintoyieldingstrata，whichthushadformedthemouldsforthesegiganticobelisks。Thewholeislandiscoveredwithwood；butfromthedrynessoftheclimatethereisnoappearanceofluxuriance。
Half-wayupthemountain，somegreatmassesofthecolumnarrock，shadedbylaurel-liketrees，andornamentedbyotherscoveredwithfinepinkflowersbutwithoutasingleleaf，gaveapleasingeffecttothenearerpartsofthescenery。
BAHIA，ORSANSALVADOR。BRAZIL，Feb。29th——Thedayhaspasseddelightfully。
Delightitself，however，isaweaktermtoexpressthefeelingsofanaturalistwho，forthefirsttime，haswanderedbyhimselfinaBrazilianforest。
Theeleganceofthegrasses，thenoveltyoftheparasiticalplants，thebeautyoftheflowers，theglossygreenofthefoliage，butaboveallthegeneralluxurianceofthevegetation，filledmewithadmiration。Amostparadoxicalmixtureofsoundandsilencepervadestheshadypartsofthewood。Thenoisefromtheinsectsissoloud，thatitmaybeheardeveninavesselanchoredseveralhundredyardsfromtheshore；yetwithintherecessesoftheforestauniversalsilenceappearstoreign。Toapersonfondofnaturalhistory，suchadayasthisbringswithitadeeperpleasurethanhecaneverhopetoexperienceagain。Afterwanderingaboutforsomehours，Ireturnedtothelanding-place；but，beforereachingit，Iwasovertakenbyatropicalstorm。Itriedtofindshelterunderatree，whichwassothickthatitwouldneverhavebeenpenetratedbycommonEnglishrain；buthere，inacoupleofminutes，alittletorrentfloweddownthetrunk。Itistothisviolenceoftherainthatwemustattributetheverdureatthebottomofthethickestwoods：iftheshowerswerelikethoseofacolderclimate，thegreaterpartwouldbeabsorbedorevaporatedbeforeitreachedtheground。Iwillnotatpresentattempttodescribethegaudysceneryofthisnoblebay，because，inourhomewardvoyage，wecalledhereasecondtime，andIshallthenhaveoccasiontoremarkonit。
AlongthewholecoastofBrazil，foralengthofatleast2000miles，andcertainlyforaconsiderablespaceinland，whereversolidrockoccurs，itbelongstoagraniticformation。Thecircumstanceofthisenormousareabeingconstitutedofmaterialswhichmostgeologistsbelievetohavebeencrystallizedwhenheatedunderpressure，givesrisetomanycuriousreflections。
Wasthiseffectproducedbeneaththedepthsofaprofoundocean？ordidacoveringofstrataformerlyextendoverit，whichhassincebeenremoved？
Canwebelievethatanypower，actingforatimeshortofinfinity，couldhavedenudedthegraniteoversomanythousandsquareleagues？
Onapointnotfarfromthecity，wherearivuletenteredthesea，I
observedafactconnectedwithasubjectdiscussedbyHumboldt[note7]。AtthecataractsofthegreatriversOrinoco，Nile，andCongo，thesyeniticrocksarecoatedbyablacksubstance，appearingasiftheyhadbeenpolishedwithplumbago。Thelayerisofextremethinness；andonanalysisbyBerzeliusitwasfoundtoconsistoftheoxidesofmanganeseandiron。IntheOrinocoitoccursontherocksperiodicallywashedbythefloods，andinthosepartsalonewherethestreamisrapid；or，astheIndianssay，“therocksareblackwherethewatersarewhite。”Herethecoatingisofarichbrowninsteadofablackcolour，andseemstobecomposedofferruginousmatteralone。Handspecimensfailtogiveajustideaofthesebrownburnishedstoneswhichglitterinthesun’srays。
Theyoccuronlywithinthelimitsofthetidalwaves；andastherivuletslowlytricklesdown，thesurfmustsupplythepolishingpowerofthecataractsinthegreatrivers。Inlikemanner，theriseandfallofthetideprobablyanswertotheperiodicalinundations；andthusthesameeffectsareproducedunderapparentlydifferentbutreallysimilarcircumstances。Theorigin，however，ofthesecoatingsofmetallicoxides，whichseemasifcementedtotherocks，isnotunderstood；andnoreason，Ibelieve，canbeassignedfortheirthicknessremainingthesame。
OnedayIwasamusedbywatchingthehabitsoftheDiodonantennatus，whichwascaughtswimmingneartheshore。Thisfish，withitsflabbyskin，iswellknowntopossessthesingularpowerofdistendingitselfintoanearlysphericalform。Afterhavingbeentakenoutofwaterforashorttime，andthenagainimmersedinit，aconsiderablequantitybothofwaterandairisabsorbedbythemouth，andperhapslikewisebythebranchialorifices。Thisprocessiseffectedbytwomethods：theairisswallowed，andisthenforcedintothecavityofthebody，itsreturnbeingpreventedbyamuscularcontractionwhichisexternallyvisible：butthewaterentersinagentlestreamthroughthemouth，whichiskeptwideopenandmotionless；
thislatteractionmust，therefore，dependonsuction。Theskinabouttheabdomenismuchlooserthanthatontheback；hence，duringtheinflation，thelowersurfacebecomesfarmoredistendedthantheupper；andthefish，inconsequence，floatswithitsbackdownwards。CuvierdoubtswhethertheDiodoninthispositionisabletoswim；butnotonlycanitthusmoveforwardinastraightline，butitcanturnroundtoeitherside。Thislattermovementiseffectedsolelybytheaidofthepectoralfins；thetailbeingcollapsed，andnotused。Fromthebodybeingbuoyedupwithsomuchair，thebranchialopeningsareoutofwater，butastreamdrawninbythemouthconstantlyflowsthroughthem。
Thefish，havingremainedinthisdistendedstateforashorttime，generallyexpelledtheairandwaterwithconsiderableforcefromthebranchialaperturesandmouth。Itcouldemit，atwill，acertainportionofthewater，anditappears，therefore，probablethatthisfluidistakeninpartlyforthesakeofregulatingitsspecificgravity。ThisDiodonpossessedseveralmeansofdefence。Itcouldgiveaseverebite，andcouldejectwaterfromitsmouthtosomedistance，atthesametimemakingacuriousnoisebythemovementofitsjaws。Bytheinflationofitsbody，thepapillae，withwhichtheskiniscovered，becomeerectandpointed。Butthemostcuriouscircumstanceis，thatitsecretesfromtheskinofitsbelly，whenhandled，amostbeautifulcarmine-redfibrousmatter，whichstainsivoryandpaperinsopermanentamannerthatthetintisretainedwithallitsbrightnesstothepresentday：Iamquiteignorantofthenatureanduseofthissecretion。IhaveheardfromDr。AllanofForres，thathehasfrequentlyfoundaDiodon，floatingaliveanddistended，inthestomachoftheshark，andthatonseveraloccasionshehasknowniteatitsway，notonlythroughthecoatsofthestomach，butthroughthesidesofthemonster，whichhasthusbeenkilled。Whowouldeverhaveimaginedthatalittlesoftfishcouldhavedestroyedthegreatandsavageshark？
March18th——WesailedfromBahia。Afewdaysafterwards，whennotfardistantfromtheAbrolhosIslets，my；attentionwascalledtoareddish-brownappearanceinthesea。Thewholesurfaceofthewater，asitappearedunderaweaklens，seemedasifcoveredbychoppedbitsofhay，withtheirendsjagged。Theseareminutecylindricalconfervae，inbundlesorraftsoffromtwentytosixtyineach。Mr。Berkeleyinformsmethattheyarethesamespecies(Trichodesmiumerythraeum)withthatfoundoverlargespacesintheRedSea，andwhenceitsnameofRedSeaisderived[note8]。Theirnumbersmustbeinfinite：theshippassedthroughseveralbandsofthem，oneofwhichwasabouttenyardswide，and，judgingfromthemud-likecolourofthewater，atleasttwoandahalfmileslong。Inalmosteverylongvoyagesomeaccountisgivenoftheseconfervae。TheyappearespeciallycommonintheseanearAustralia；andoffCapeLeeuwinIfoundanalliedbutsmallerandapparentlydifferentspecies。CaptainCook，inhisthirdvoyage，remarks，thatthesailorsgavetothisappearancethenameofsea-sawdust。
NearKeelingAtoll，intheIndianOcean，Iobservedmanylittlemassesofconfervaeafewinchessquare，consistingoflongcylindricalthreadsofexcessivethinness，soastobebarelyvisibletothenakedeye，mingledwithotherratherlargerbodies，finelyconicalatbothends。Twooftheseareshowninthewoodcutunitedtogether。Theyvaryinlengthfrom。04
to。06，andevento。08ofaninchinlength；andindiameterfrom。006
to。008ofaninch。Nearoneextremityofthecylindricalpart，agreenseptum，formedofgranularmatter，andthickestinthemiddle，maygenerallybeseen。This，Ibelieve，isthebottomofamostdelicate，colourlesssac，composedofapulpysubstance，whichlinestheexteriorcase，butdoesnotextendwithintheextremeconicalpoints。Insomespecimens，smallbutperfectspheresofbrownishgranularmattersuppliedtheplacesofthesepta；andIobservedthecuriousprocessbywhichtheywereproduced。
