Gregory — Progress in Interpretation of Land Forms. 129 



and Irving in Wisconsin was undoubtedly helpful in 

 establishing the theory of continental glaciation. From 

 the intimate companionship in field and laboratory of 

 Hutton, Playfair and Hope, arose the profound influence 

 of the Edinburgh school, and the sympathetic cooperation 

 of Powell, Gilbert, and Dutton has given to the world its 

 classics in the genetic study of land forms. 



The influence of ideas has been closely associated with 

 clarity, conciseness, and attractiveness of presentation. 

 Hutton is known through Playfair, Agassiz's contribu- 

 tions to glacial geology are known to every student, while 

 Yenetz, Charpentier, and Hugi are only names. Cuvier's 

 discourses on dynamical geology were reprinted and 

 translated into English and German, but Lamarck's 

 ' ' Hydrogeologie ' ' is known only to book collectors. The 

 verbose works of Guettard, although carrying the same 

 message as Playfair 's " Illustrations " and Desmarest's 

 "Memoirs," are practically unknown, as is also Horace 

 H. Hayden's treatise (1821) on the drift of eastern 

 North America. It has been well said that the world- 

 wide influence of American physiographic teaching is due 

 in no small part to the masterly presentations of Gilbert 

 and Davis. 



It is surprising to note the delays, the backward steps, 

 and the duplication of effort resulting from lack of 

 familiarity with the work of the pioneers. Sabine savs 

 in 1864 : 73 ' 



"It often happens, not unnaturally, that those who are most 

 occupied with the questions of the day in an advancing science 

 retain but an imperfect recollection of the obligations due 

 to those who laid the first foundations of our subsequent 

 knowledge. ' ' 



The product of intellectual effort appears to be con- 

 ditioned by time of planting and character of soil as well 

 as by quantity of seed. For example: Erosion by 

 rivers was as clearly shown by Desmarest as by Dana and 

 Newberry 50 years later. Criteria for the recognition of 

 ancient fluviatile deposits were established by James 

 Deane in 1847 in a study of the Connecticut Valley 

 Triassic. Agassiz's proof that ice is an essential factor 

 in the formation of till is substantially a duplication of 

 Dobson's observations (1826). 



The volumes of the Journal with their very large num- 



Am. Jour. Sci.— Fourth Series, Vol. XLVI, No. 2T1.— July, 1918. 

 5 



