Gregory — Progress in Interpretation of Land Forms. 117 



written in 1837 and containing additional evidence and 

 argument remained unpublished until Murchison, in 

 1842, 41 paid his respects to the remarkable work of a 

 remarkable man.* 



k ' I take leave of the glacial theory iu congratulating American 

 science in having possessed the original author of the best 

 glacial theory, though his name had escaped notice; and in 

 recommending to you the terse argument of Peter Dobson, a 

 previous acquaintance with which might have saved volumes of 

 disputation on both sides of the Atlantic." 



Glaciers vs. Icebergs. 



The glacial theory makes its way into geological lit- 

 erature with the development of Agassiz (1837) of the 

 views of Venetz (1833) and Charpentier (1834), that the 

 glaciers of the Alps once had greater extent. The bold 

 assumption was made that the surface of Europe as far 

 south as the shores of the Mediterranean and Caspian 

 seas was covered by ice during a period immediately 

 preceding the present. The kernel of the present gla- 

 cial theory is readily recognizable in these early works, 

 but it is wrapped in a strange husk : it was assumed that 

 the Alps were raised by a great convulsion under the 

 ice and that the erratics slid to their places over the 

 newly made declivities. The publication of the famous 

 "Etudes sur les Glaciers' ' (1840), remarkable alike for 

 its clarity, its sound inductions, and wealth of illustra- 

 tions, brought the ideas of Agassiz more into prominence 

 and inaugurated a 30-years' war with the proponents of 

 currents and icebergs. The outstanding objections to the 

 theory were the requirement of a frigid climate and the 

 demand for glaciers of continental dimensions ; very 

 strong objections, indeed, for the time when fossil evi- 

 dence was not available, the great polar ice sheets were 

 unexplored, and the distinction between till and water- 

 laid drift had not been established. 



The glacial theory was cordially adopted by Buck- 

 land (-1841 ) 42 and in part by Lyell in England but 

 viewed with suspicion by Sedgwick, Whewell, and Man- 

 tell. In America the response to the new idea was 

 immediate. Hitchcock (1841) 17 concludes an able dis- 



* Peter Dobson (1784-1878) came to this country from Preston, England, 

 in 1809 and established a cotton factory at Vernon, Conn. 



