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Snæfell at Last

           Iceland,whichisentirelydevoidofalluvialsoil,iswhollycomposedofvolcanictufa,thatistosay,anagglomerationofporousrocksandstones.Beforethevolcanoesbrokeoutitconsistedoftraprocksslowlyupraisedtotheleveloftheseabytheactionofcentralforces.Theinternalfireshadnotyetforcedtheirwaythrough.

           Butatalaterperiodawidechasmformeddiagonallyfromsouth-westtonorth-east,throughwhichwasgraduallyforcedoutthetrachytewhichwastoformamountainchain.Noviolenceaccompaniedthischange;thematterthrownoutwasinvastquantities,andtheliquidmaterialoozingoutfromtheabyssesoftheearthslowlyspreadinextensiveplainsorinhillockymasses.Tothisperiodbelongthefelspar,syenites,andporphyries.

           Butwiththehelpofthisoutflowthethicknessofthecrustoftheislandincreasedmaterially,andthereforealsoitspowersofresistance.Itmayeasilybeconceivedwhatvastquantitiesofelasticgases,whatmassesofmoltenmatteraccumulatedbeneathitssolidsurfacewhilstnoexitwaspracticableafterthecoolingofthetrachyticcrust.Thereforeatimewouldcomewhentheelasticandexplosiveforcesoftheimprisonedgaseswouldupheavethisponderouscoveranddriveoutforthemselvesopeningsthroughtallchimneys.Hencethenthevolcanowoulddistendandliftupthecrust,andthenburstthroughacratersuddenlyformedatthesummitorthinnestpartofthevolcano.

           Totheeruptionsucceededothervolcanicphenomena.Throughtheoutletsnowmadefirstescapedtheejectedbasaltofwhichtheplainwehadjustleftpresentedsuchmarvellousspecimens.Weweremovingovergreyrocksofdenseandmassiveformation,whichincoolinghadformedintohexagonalprisms.Everywherearounduswesawtruncatedcones,formerlysomanyfierymouths.

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