466 REPORT OF NATIONAL MUSEUM, 1904. 



Again, with reference to the subdued features of the West, he 

 wrote: 



The thickness of the entire series of sedimentary rocks, no matter how much dis- 

 turbed and denuded, is not here great enough to produce mountain features. 



In this, it will be observed, is given the gist of his theory of moun- 

 tain formation, as announced two years later. 



Numerous changes in nomenclature and important correlations were 

 made, or at least attempted. The Lower Magnesian limestone of 

 Owen he considered as identical with the Calciferous of New York, 

 and gave the name Galena to the limestone immediately succeeding 

 the Trenton, and which Owen had called Upper Magnesian. The 

 "Coralline and Upper Pentamerus beds of the Upper Magnesian 

 limestone," of Owen, he identified as Niagara, and proposed the name 

 Leclaire to designate a gray to whitish limestone lying next above the 

 Niagara and found outcropping near the town of that name. The 

 entire series of Coal Measure rocks he showed to have been deposited 

 after the disturbances producing the low folds in the Silurian rocks, 

 illustrating their relative position by the section here reproduced. 



The encrinital group of Burlington and that of Hannibal, Missouri, 

 thought by D. D. Owen to be distinct, were considered by Hall to be 

 identical. The entire series of Carboniferous limestones were regarded 

 as " successively deposited in an ocean, the limits of which were grad- 

 ually contracted upon the north while at the south the conditions were 

 becoming more and more favorable to the development of this kind of 

 deposition and to the support of the fauna which abounded throughout 

 the period, until both culminated in the great limestone formation of 

 Kaskaskia. (The Archimedes limestone of Owen.) 



In discussing the relationship of the limestone and coal, Hall quoted 

 from his report on the geology and paleontology of the Mexican 

 Boundary, elsewhere alluded to. With reference to this he wrote: 



The conditions favorable to the production of an extensive deposit of marine lime- 

 stone are not such as usually accompany the production of coal. In the present 

 instance the ocean, depositing the great limestone formations previous to the coal 

 period, occupied to a great extent the present area of the Coal Measures which suc- 

 ceeded in the valley of the Mississippi. * * * We begin thus to comprehend the 

 truth, that during the period of the great coal formations of the West, in which these 

 calcareous deposits were in course of formation — that during the oscillations which 

 we know to have occurred throughout the coal period there was a time when the 

 whole area became depressed so as to allow the waters of the western ocean to 

 tl<»\v over all the Coal Measure region; or, at least, as far northward and eastward 

 as the northeastern part of Ohio, and from hence it derived the limestone under 

 consideration. 



The series of beds immediately underlying the Carboniferous rocks 

 at Burlington, and now considered as Kinderhook (sub-Carboniferous), 

 Hall relegated to the Chemung; this proved to be an error, and one 

 that it required many years to eradicate. 



