AMERICAN GEOLOGY DECADE OF 1850-1859. 465 



in 1857, Joseph Le Conte, then professor of chemistry and geology 



in the University of South Carolina, made his first appearance in the 



geological arena, with a paper, subsequently pub- 



josephLe Conte on Hshed in the American Journal of Science, in which he 



Coral Growth, 1857. 



argued that the peninsula of Florida owed its southern 

 continuation to a double process of coral-reef growth and sedimenta- 

 tion from the Gulf Stream. It was his idea that the sediments brought 

 down by the Mississippi sank to a depth beyond observation before 

 reaching the Keys, but were gradually deposited along the inner side 

 of the curve formed by the current as it passed around the point. 

 When the bottom should have become sufficiently elevated by this 

 process, a new reef would begin to form. This process he thought to 

 have gone on until the channel had become narrowed as now, and the 

 rush of water, together with the depth, practically precluded further 

 deposition. Waves throwing broken material upon the beaches would 

 serve to till the old channels and convert them into dry land. In brief, 

 "the peninsula and Keys of Florida have been the result of the com- 

 bined action of at least three agencies. First, the Gulf Stream laid 

 the foundation; upon that corals built up to the water level; and, 

 finally, the work was completed by the waves." 



Le Conte further conceived that the rate of flow of the Gulf Stream 

 has been gradually accelerated by the narrowing of its channel, and 

 hence had made itself manifest at a greater distance into the Atlantic, 

 thus bringing about a gradual amelioration of the climate of England. 



In 1855 the first State geological survey of Iowa was organized, and 



Dr. James Hall made State geologist. The organization continued 



through 1858. The reports of the survey appeared in the form of 



two octavo volumes, of which the second volume was 



Hall's Geological . in i i tt n • x i 



Survey of iowa, given up wholly to paleontology. Hall was assisted 

 in this survey by J. D. Whitney, who served as 

 chemist and mineralogist, and by A. H. Worthen, F. B. Meek, and 

 R. P. Whitfield. 



Hall noted the rapid westward thinning out of the various beds of 

 sedimentary rocks, including those of the Hudson River, Medina, 

 Clinton, Niagara, and Onondaga salt group, and Catskill Mountain 

 group, and made the following comment: 



This remarkable fact of the thinning out westerly of all the sedimentary forma- 

 tions points to a cause in the conditions of the ancient ocean, and the currents which 

 transported the great mass of material along certain lines, which became the lines 

 of greatest accumulation of sediments, and consequently present the greatest thick- 

 ness of strata at the present time. It is this great thickness of strata, whether dis- 

 turbed and inclined as in the Green and White mountains and the Appalachians 

 generally, or lying horizontally as in the Catskill Mountains, that gives the strung 

 features to the hilly and mountainous country of the East and which gradually dies 

 out as we go westward just in proportion as the strata become attenuated. 

 NAT mus 1904 30 



