AMERICAN" GEOLOGY DECADE OF 1870-1879. 



561 



of preparation by sedimentation; (2; a stage of yielding by horizontal 

 pressure; and (3) a stage of erosion or mountain decay. 



Le Conte was born in Liberty County, Georgia, February 26, 1823, 

 and grew to manhood under influences of ease and enjoyment such as 

 have fallen to the lot of few American geologists. Educated as a 



physician, he early gave up practice and in 1850 re- 

 sketch of Le Conte. moved to Cambridge, in Massachusetts, to become a 



student of Agassiz. In less than two years he, how- 

 ever, returned to Georgia, where he became professor of natural 

 science at Oglethorpe University. His stay here was brief. In 

 December, 1852, he became attached to the University of Georgia, at 

 Athens, and, in 1856, professor of chemistry and geology in South 

 Carolina College, at Columbia. Here he remained, enduring the vicis- 

 situdes of the civil war, but abandoned his beloved South in L869 (at 

 a period when men of his t} r pe were most needed) to become professor 

 of geology, zoology, and botany in the Uni- 

 versity of California, at Berkeley. Here 

 he remained until his death, in 1902. 



In 1866 E. W. Hilgard, at the suggestion 

 of Professor Henry, of the Smithsonian 

 Institution, visited the salt deposits of Petite 



Islands and published the 



Hilgard's Work at , . r . 



Petite Anse, results or his observations 



Louisiana, 1872. • i o ■ i • r^ 



in the Smithsonian Contri- 

 butions to Knowledge in 1872, under the 

 title On the Geology of Lower Louisiana 

 and the Salt Deposits of Petite Anse. 



As was to be expected, Hilgard differed 

 completely with Thomassy, whose work has 

 been noted, and who, it will be remembered, 

 regarded the island as of volcanic origin. On the contrary, the island, 

 and others of the group, were regarded as Cretaceous outliers, with 

 mappings of drift and other alluvial matter, the salt beds themselves 

 being of Cretaceous. age. 



Both Hilgard and Thomassy believed the sand and shingle detritus 

 covering a large portion of the States bordering on the lower Missis- 

 sippi was due to a great flood, which might have resulted from the rapid 

 melting of the northern glaciers. Referring to the belief expressed 

 by some of the western geologists to the effect that the main body of 

 the drift was due to floating icebergs on an inland sea, Hilgard con- 

 ceived its northern limits to have been fixed by the ice barriers. 

 Toward the east, southeast, and southwest it would be defined by the 

 Allegheny, Cumberland, and Ozark ranges, the main outlet lying, 

 doubtless, in the axis of the Mississippi Valley, the gap between the 



NAT MUS 1904 36 



Pig, 88.-r-Joseph Lu Conte. 



