480 PIONEERS OF SCIENCE IN AMERICA. 



In 1842 Agassiz began the publication of his Nomenclator Zo- 

 ologicus, an alphabetical list of every genus, with the name of 

 the author, the work in which it originally appeared, the deriva- 

 tion of the name, and the family to which the genus belongs ; 

 the list embracing upward of seventeen thousand names. In 

 the introduction the author discusses at length the rules pro- 

 posed by the British Association and those of the British Com- 

 mittee, in regard to assigning and changing the names of genera 

 and species, the settlement of priority, the proper terminations 

 of zoological names, and other like matters. 



The Fossil Fishes was now approaching completion, but, in 

 consequence of additional material, Agassiz determined to pub- 

 lish a supplement; and accordingly there appeared, in 1844, 

 the Fossil Fishes of the Old Red Sandstone. It was accom- 

 panied by an atlas of thirty-nine folio plates illustrative of the 

 seventy-six species described. 



Of all Agassiz's investigations, perhaps none made his name 

 more popularly known than his studies on glaciers studies 

 which were pursued through a long course of years, and con- 

 ducted with the same painstaking care that had heretofore 

 characterized all his labours. 



About the year 1834, M. Charpentier advanced the theory 

 that the erratic blocks, and certain dikes of peculiar shape 

 found in the Alpine regions, were the result of the action of 

 former glaciers descending from the Alps and reaching even 

 the upper portions of the Jura. This theory Agassiz deemed 

 improbable, till, having visited Charpentier and investigated 

 the phenomena, he not only became convinced of the correct- 

 ness of Charpentier's views, but deduced from these and other 

 phenomena a theory which, at the time (1837), was startlingly 

 novel. It was that, previous to the elevation of the Alps, the 

 globe experienced a very great reduction of temperature, and 

 that the appearance of those mountains found the surface of 

 the globe, from the north pole to the Mediterranean Sea, cov- 

 ered with an immense sheet of ice. An elevation of tempera- 

 ture, consequent upon the upheaval of the Alps, caused this ice 

 slowly to disappear, remaining longest in the valleys, where it 

 gradually retreated to its present limits, leaving behind it, as a 

 record, the peculiar phenomena which have attracted the atten- 

 tion of so many observers. 



Of course a theory so novel at once raised a storm of oppo- 



