GLACIAL GEOLOGY OF NORTHEASTERN AMERICA. 375 



AvouUl help bring on ;in abnormal extension of ice and snow in the Scandi- 

 navian Peninsula. That a much greater precipitation than that now taking 

 place would be one of the requisites for more extensive glaciation of the 

 region in question can hardly be doubted. This desired increase would be 

 the necessary result of a higher mean temperature of the earth. The greater 

 the actual amount of moisture raised from the surface of the ocean by evap- 

 oration, the larger would be the precipitation as a whole ; and local condi- 

 tions would cause this to be very unequally distributed, just as they now 

 do, the result being that in certain regions the fall of rain or snow would be 

 far superior in amount to what it is at the present time. 



Finally, we may turn to the consideration of the phenomena exhibited in 

 the second great and important region of past glaciation to wliich reference 

 has been made when indicating those parts of the earth where ice and snow 

 have once played a more important part than they now do. Complicated as 

 are the conditions over the glaciated region of which the Scandinavian 

 Range is the centre, we find them considerably more so in Northeastern 

 North America. The present volume will not, however, aftbrd us the neces- 

 sary space for anything like a complete analysis of that which has been 

 published on this side of the Atlantic, bearing on the nature and origin of 

 the Glacial epoch, including, as this material does, everything connected with 

 the occurrence of the superficial detrital formations over an area of more 

 than a million of square miles. All that can here be done is to point out 

 some of the more important facts having a special bearing on the question 

 before us, discussing them only to such an extent as is necessary to enable 

 the reader to form an idea of what is known, or may be reasonably inferred, 

 with regard to the climatic conditions connecting themselves with the epoch 

 of tlie former greater extension of ice in Northeastern America, and to satisfy 

 hunself especially that this phase of our geological history was not the result 

 of a lowering of the mean temperature of the continent. 



In order to enter understandingly into the contemplated discussion it will 

 be necessary to present a brief statement of the facts with which we have to 

 deal. This, however, will not be an easy matter, because, these being often 

 obscure, as has already been explained, geologists are wont to interpret them 

 in the light of previously adopted theories, so that on many points the evi- 

 dence is of a most contradictory kind. In making the following statement 

 the writer will endeavor to present the case impartially, relying on his own 

 examinations, which have extended over a large part of the area in question, 



