Change of Climate during Geological Epochs. 125 



now extinct in our British seas, viz. My a Uddevallensis, Saxicava 

 7'ugosa, Tellma proximo, Thracia myopsis, Astarte arctica, Leda 

 minuta, Leda truncata, Leda oblonga, Pecten Grcenlandicus, 

 Pecten Islandicus, Margarita cinerea, Turritella erosa, Scalaria 

 Grcenlandica, Natica clausa, Velutina undata, Buccinum ciliatum, 

 Fusus carinatus, Cylichna alba. Other arctic shells, such as 

 the Panopcea Norvegica, Puncturella Noachina, Nucula tenuis, 

 Trophon clathratus, Trophon scalariformis, Natica pusilla, Natica 

 helicoides, Trichotropis borealis, Saxicava arctica, Hypothyris 

 psittacea, Margarita undulata, Margarita helicina, Buccinum 

 Humphrey sianum, Cyprina Islandica, existed during the glacial 

 epoch in great abundance in our British seas, but are now fast 

 dying out in the deep and cold recesses of the ocean where they 

 have retreated in order to find a temperature more congenial to 

 their nature *. 



We freely admit that a warmer sea and a colder land would 

 tend to produce an accumulation of snow and ice such as pre- 

 vailed during the glacial period. And did the facts of geology 

 and the principles of physical science favour the idea that the 

 sea during that period was warmer than at present, we should 

 assuredly admit the warm sea to be at least one of the causes 

 of the glacial epoch. But when the very same result may be 

 conceived to follow upon the contrary supposition, which agrees 

 better with the evidence of geology — that the sea was actually 

 colder during the glacial period than at present — we feel inclined 

 to refer the cold of that period to some other cause than to a 

 warm sea. That a reduction of the mean temperature of both 

 land and sea in our latitude would produce the same effect, will 

 be obvious to all who will but reflect that at the present day 

 there exists in places where the mean annual temperature is not 

 much above the zero of the Fahrenheit scale, glaciers in magni- 

 tude equal to, if not greater than any which covered our valleys 

 during the glacial epoch. At the present day there are glaciers 

 upwards of 50 miles in breadth, and 2000 feet in depth, 

 merging into the cold and frozen seas around the north of 

 Greenland t- Greenland at the present day is probably a re- 

 presentation of what our island was during the glacial period. 



Of late, evidence of the most conclusive character has been 

 adduced by Prof. Ptamsay and others of the existence of a 

 glacial epoch in this country during the far back Palaeozoic age. 



* See a valuable paper " On the Glacial Drift of Scotland," by 

 Archibald Geikie, F.R.S.E., F.G.S. John Gray, Glasgow, 1 863. See also 

 a paper by Prof. E. Forbes " On the Connexion between the Distribution 

 of the existing Fauna and Flora of the British Isles, and the Geological 

 Changes which have affected their area during the period of the Northern 

 Drift" (Memoirs of the Geological Survey, vol. i.). 



t See Dr. Kane's 'Second Expedition,' vol. i. cnap. xviii. 



