AMERICAN GEOLOGY DECADE OF 1850—1859. 



435 



In the paleontological report by Dr. B. F. Shumard there were 

 described Carboniferous fossils from Washington and Crawford coun- 

 ties, Arkansas, and Cretaceous forms from Fort Wichita and the Cross 

 Timbers regions of Texas. 



Hitchcock, in his report, dwelt particularly on the possible Carbon- 

 iferous age of various beds of coal, reported by Shumard, and the 

 economic value of the gypsum, as well as the ores of copper and gold. 

 His reference to the canyons of the Red River is particularly interest- 

 ing in view of his early writings regarding the Connecticut (p. 31<»): 



You seem in doubt whether this gorge was worn away by the river or is the result 

 of some paroxysmal convulsion. You will allow me to say that I have scarcely any 

 doubt that the stream itself has done the work. The fact that when a tributary 

 stream enters the main river it passes through a tributary canyon seems to me to 

 show conclusively that these gorges were produced by erosion and not by fracture. 



Two papers on the subjects of rock decay 

 and erosion, of this year, are worthy of con- 

 sideration. Prof. Oliver P. Hubbard, of 

 Dartmouth College, during a study of the 

 trap dikes, noted that the same could be 

 traced continuously across 

 the countiy, at varying 

 levels, from mountain top to 

 From this fact he argued 

 that the valleys had been carved out through 

 decomposition and erosion since the dikes 

 were formed. The difference in altitude at 

 the various outcrops gave, then, a measure 

 of the amount of erosion. 



Dana's observations, though of a some- 

 what different nature, were none the less interesting. In writing on 

 denudation in the Pacific, he took the ground that the ocean is power- 

 less to excavate valleys along the coast, and that the deep valleys 

 like those of Tahiti are due to subaerial decomposition and erosion, 

 an observation no geologist of to-day would venture to doubt. 



In March, 1853, b} T resolution of the senate of the State of Califor- 

 nia, Dr. John B. Trask was called upon to furnish information in 

 relation to the geology of the State. As a result Doctor Trask sub- 

 mitted material issued in a pamphlet of 30 pages, pub- 

 lished by the assembly in the session of 1853. By a 

 joint resolution which passed the senate and assembly 

 on May 6, 1853, Trask was authorized to make a further examination 

 of some parts of the Sierra Nevada and Coast Range mountains. As 

 a result of this and subsequent acts there were issued reports on the 

 geology of the region mentioned in 1851, 1855, and 1856. 



Hubbard and Dana 

 on Subaerial 

 Erosion, 1852. 



vallev bottom. 



Fig. 54.— Oliver Payson Hubbard. 



Trask's Geological 

 Survey of 

 California, 1853. 



