4 



The Naturalist. 



scientific society of Europe. His next work was his Descr'qdlon of 

 Eclimodernu^ followed, in 1839, by Ms grand treatise on the Fresh- 

 water Fisli of Europe. 



But the book by which he attained his highest honours, and 

 won his best and widest European fame, was his treatise entitled 

 Studies of Glaciers, the result of many years of observation. His • ' 

 theory, promulgated in 1837, formed a singular advance upon 

 previous geographical discoveries. It is needless to recall to your 

 recollection the fact that Werner and Hutton were then the grand 

 oracles on this subject. Werner referred to water nearly all the 

 changes undergone by the face of the globe. Hutton held that 

 fire had been the prime agent. So eminent did their respective names 

 become in connection with these two theories, that the one was 

 familiarly called by geologists the Wernerian system, and the other 

 the Huttonian. Strong parties of advocates and supporters arose on 

 both sides. But the majority of scientific people could not coincide 

 wholly with either party. The action of both water and fire on the 

 surface of the earth was too plain to be disputed, and to regard either 

 as the sole agent could not be generally admitted. So that, in the 

 course of time, the principal questions came to be, " Which of the 

 powers had done most ? And in what ways had they acted ?" It was 

 perfectly plain that the deeper stratifications had resulted from both 

 agencies, aqueous and igneous (or volcanic) ; but which of them had had 

 the largest share in arranging the outer and existing crust of the earth, 

 in forming its mountains, its vales, and all the varied appearances 

 which it presents, was a point really open to discussion. On this 

 head men of science still continued to doubt and dispute. By his 

 close and searching observations on the icy masses called glaciers, as 

 they are to be found in Switzerland and other Alpine countries, 

 Professor Agassiz threw a flood of light on this important subject. In 

 fact, he began a new era in geology, for it was he who first pointed 

 out the signs of the Glacial Period. He proved, beyond question, 

 that, in arranging the visible parts of the earth as they stand, water 

 had been an agent in a form before scarcely thought of, and to an 

 extent before not apprehended. He proved that, in the shape of mighty 

 rivers of ice, it had modified the terrestrial surface most materially 

 in places where the climate no longer permits of such action. Thus* 

 the glacier or ice theory came to involve many curious points, 

 relating as well to the temperature of the earth as to its actual super- 

 ficial structure in early ages. It accounted, also, for matters which 

 science had before looked on hopelessly, as, for example, on the 

 existence of boulders, or large water-worn stones, in positions far above 



