382 M. Agassiz on Glaciers, Moraines, and Erratic Blocks. 



The admission of an epoch of cold, which was so intense as 

 to cover the earth to such distances from the poles with so vast 

 a mass of ice as we have been contemplating, is a supposition 

 which appears in direct contradiction with those well known 

 facts, which shew a considerable cooling of the earth since the 

 most remote period. Nothing, however, has proved that this 

 refrigeration has been constant, and that it has occurred with- 

 out oscillations. On the contrary, whoever has been in the 

 habit of studying nature in a physiological point of view, will 

 be much more disposed to admit that the temperature of the 

 earth has been maintained, without any considerable oscilla- 

 tions, to a certain degree, during the whole period of any geo- 

 logical epoch, as is occurring in our own epoch, since it has 

 diminished suddenly and considerably at the termination of 

 each epoch, a change accompanied by the disappearance of the 

 organized beings which characterized it, that it may rise again 

 with the appearance of a new creation at the commencement of 

 the following epoch, although at a lower degree of mean tem- 

 perature than the preceding one, so that the diminution of the 

 temperature of the globe may be expressed by the following 

 line : — 



^^^ 



Thus, the epoch of extreme cold which preceded the pre- 

 sent creation, has only been a passing oscillation of the tempera- 

 ture of the globe, somewhat more considerable than the periodic 

 refrigeration to which the valleys of our Alps are subject. It wa."? 

 attended by the disappearance of the animals of the diluvian 

 epoch of geologists, as the mammoths of Siberia still attest, and 

 preceded the uprising of the Alps, and the appearance of the 

 animated nature of our day, as is proved by the moraines, and 

 the presence of fish in our lakes. Thei-e was thus a complete 

 sepai'ation between the existing creation and those which have 

 preceded it ; and, if the living species sometimes resemble in 

 our apprehension those which are hid in the bowels of the earth, 

 it nevertheless cannot be affirmed that they have regularly 

 descended from them in the way of primogeniture, o;-, what is 

 the same thing, that they are identical species. 



'By prosecuting these views, we may anticipate the time will 



