Stratijied Fossiliferous Deposits resting on Drift. 115 



glacial drift is contemporaneous. It would seem, however, 

 as if the extensive accumulation of drift all around the nor- 

 thern pole in Europe, Asia, and America was of the same 

 age as the erratic of the Alps. The climatic circumstances 

 capable of accumulating such large masses of ice around the 

 north pole, having no doubt extended their influence over 

 the temperate zone, and probably produced, in high mountain 

 chains, as the Alps, the Pyrenees, the Black Forest, and the 

 Vosges, such accumulations of snow and ice as may have 

 produced the erratic phenomena of those districts. But ex- 

 tensive changes must have taken place in the appearance of 

 the continents over which we trace erratic phenomena, since 

 we observe in the Old World, as well as in North America, 

 extensive stratified deposits containing fossils which rest 

 upon the erratics ; and as we have all possible good reasons 

 and satisfactory evidence for admitting that the erratics 

 were transported by the agency of terrestrial glaciers, and 

 that, therefore, the tracts of land over which they occur stood 

 at that time above the level of the sea, we are led to the 

 conclusion that these continents have subsided since that 

 period below the level of the sea, and that over their inun- 

 dated portions, animal life has spread, remains of organized 

 beings have been accumulated, which are now found in a 

 fossil state in the deposits formed under those sheets of 

 water. 



Such deposits occur at various levels in different parts of 

 North America. They have been noticed about Montreal, on 

 the shores of Lake Champlain, in Maine, and also in Sweden 

 and Russia ; and what is most important, they are not every- 

 where at the same absolute level above the surface of the 

 ocean, shewing that both the subsidence and the subsequent 

 upheaval which has again brought them above the level of 

 the sea, have been unequal ; and that we should therefore 

 be very cautious in our inferences respecting both the con- 

 tinental circumstances under which the ancient glaciers were 

 formed, and also the extent of the sea afterward, as compared 

 with its present limits. 



The contrast between the unstratified drift and the sub- 



h2 



