GLACIAL GEOLOGY IN AMERICA. 359 



widely over New England. In 1863 the report of progress of the 

 Geological Survey of Canada gave an extended review of the sur- 

 face geology, by Prof. Robert Bell, in which he fully adopted the 

 glacial theory. Meantime, also, Professor Ramsay, in England, had 

 abandoned the iceberg doctrine for that of glaciers. 



In 1866 and 1867 important papers appeared by Charles Whit- 

 tlesey, and one by Edward Hungerford; this last, read before 

 the association, adopted the general views of Agassiz, with 

 some important limitations now generally received. In the same 

 year the revised edition of Dana's Manual gave yet fuller state- 

 ment and wider diffusion to the generally accepted views as held 

 to-day. 



Professor Eairchild sums up this historical sketch as comprising 

 four periods — viz., prior to 1841, undisputed reign of diluvial hy- 

 potheses; 1841 to 1848, suggestion and discussion of glacial hypoth- 

 eses; 1849 to 1866, gradual acceptance of the latter view; from 1867 

 onward, development of glacial geology. 



Erom this point, the address was occupied with consideration of 

 the various aspects of the subject as studied and wrought out during 

 the past twenty years by numerous observers. These are grouped 

 under four main heads, each with various subdivisions — viz., (1) the 

 ice sheet, as to its area, its thickness, its centers of dispersion, its 

 migration of centers, etc.; (2) the ice period, as to its cause, its 

 divisions, its duration, its distance in time; (3) the interpretation of 

 special phenomena, such as moraines, drumlins, eskers, " kettles," 

 and the like, valley drift, terraces, loess, etc. ; and (4) existing gla- 

 ciers, as discovered on our high mountains of the far West, and as 

 studied in closer relation to the ancient phenomena in the great 

 ice cap of Greenland and the immense glacier development in 

 Alaska. 



It is impossible to go into a detailed review of the numerous 

 points of interest covered in this discussion. Suffice it to say that 

 one who heard or who reads it finds an admirably clear and con- 

 densed account of all the problems and phenomena that have been 

 and that are now encountered in the study of glacial geology on this 

 continent, and of their gradual interpretation and solution by the 

 combined labors of many students. The progress of knowledge over 

 this wide field, advancing step by step, amid conflicting views and 

 perplexing conditions, is beautifully shown, and leaves a very strik- 

 ing impression on the mind, of the difficulties and the successes of 

 scientific research. Nor is Professor Fairchild disposed to claim too 

 much or assert too strongly. He recognizes that, with all that has 

 been met and mastered, there are still questions unsolved, and laurels 

 to be won by others. 



