ADRUESS. Ixxiii 



liilion in climate as might go far to account for the excessive cold which was 

 (lc^'eloped at so modern a period in the earth's history. But even when we 

 assume all three of them to have been simultaneouslj- in action, we have by 

 no means exhausted all the resources which a difference in the geographical 

 condition of the globe might supply. Thus, for example, to name only one of 

 them, we might suppose that the height and quantity of land near the north 

 pole was greater at the era in qiiestion than it is now. 



The vast mechanical force that ice exerted in the glacial period has been 

 thought by some to demonstrate a want of imiformity in the amount of 

 energy which the same natural cause may put forth at two successive epochs. 

 But we must be careful, when thus reasoning, to bear in mind that the power 

 of ice is here substituted for that of running water. The one becomes a 

 mighty agent in transporting huge erratics, and in scoring, abrading, and 

 polishing rocks ; but meanwhile the other is in abeyance. When, for example, 

 the ancient lihone glacier conveyed its moraines from the upper to the lower 

 end of the Lake of Geneva, there was no great river, as there now is, forming 

 a delta many miles in extent, and several hundred feet in depth, at the 

 iipper end of the lake. 



The more we study and comprehend the geographical changes of the glacial 

 period, and the migrations of animals and plants to which it gave rise, the 

 higher our conceptions are raised of the duration of that subdivision of time, 

 which, though vast when measm-ed by the succession of events comjirised in it, 

 was brief, if estimated by the ordinary rules of geological classification. The 

 glacial period was, in fact, a mere episode in one of the great epochs of the 

 earth's history ; for the inhabitants of the lands and seas, before and after the 

 grand development of snow and ice, were nearly the same. As yet we have no 

 satisfactory proof that man existed in Europe or elsewhere during the period 

 of extreme cold ; but our investigations on this head are still in their infancy. 

 In an early portion of the postglacial period it has been ascertained that man 

 flourished in Europe ; and in tracing the signs of his existence, from the 

 historical ages to those immediately antecedent, and so backward into more 

 ancient times, we gradually approach a dissimilar geographical state of 

 things, when the climate was colder, and when the configuration of the 

 surface departed considerably from that which now prevails. 



Archaeologists are satisfied that in central Eiirope the age of bronze weapons 

 preceded the Roman invasion of Switzerland ; and prior to the Swiss-lake 

 dwellings of the bronze age were those in which stone weapons alone were 

 used. The Danish kitchen-middens seem to have been of about the same 

 date ; but what M. Lartet has called the reindeer period of the South of 

 France was probably anterior, and connected with a somewhat colder climate. 

 Of still higher antiquity was that age of inider implements of stone such as were 

 buried in the fluviatile drift of Amiens and Abbeville, and which were mingled 

 in the same gravel with the bones of extinct quadrupeds, such as the elephant, 

 rhinoceros, bear, tiger, and hyaena. Between the present era and that of 

 those earliest vestiges yet discovered of our race, valleys have been deepened 

 and widened, the course of subterranean rivers which once flowed through 

 caverns has been changed, and many species of wild quadrupeds have dis- 

 appeared. The bed of the sea, moreover, has in the same ages been lifted up, 

 in many places hundreds of feet, above its former level, and the outlines of 

 many a coast entirely altered. 



MM. de Yerneuil and Louis Lartet have recently found, near Madrid, fossil 

 teeth of the African elephant, in old valley-drift, containing flint imijlements 

 of the same antique type as those of Amiens and Abbeville. Proof of the 



