508 REPORT OF NATIONAL MUSEUM, 1904, 



Louis Agassiz at the meeting of the Boston Society of Natural History, 

 March 21, 1860. 



Rogers argued that the strata between Lake Ontario and the Penn- 

 sylvania coal region were deposited on gradually subsiding sea bot- 

 ,„ . toins. On this supposition only could he account for 



Ideas ot Rogers and r r .' 



Agassizon fc ne relative position of the beds and their very great 



Subsidence and i • » 



Deposition, 1860. thickness. Had they been formed as argued by some 

 on a gradually rising sea bottom, the older deposits would crop out 

 at the higher levels and the successively later ones at lower levels. 

 Agassiz, on the other hand, maintained that there was no subsidence 

 during the deposition of the New York strata, and that the facts indi- 

 cated just the reverse, i. e., an upheaval. During the upheaval, he 

 argued, the level of the sea might be actually less, from the contraction 

 of the earth while cooling, but in consequence of this contraction the 

 ocean would always remain at a certain depth, sufficient for the depo- 

 sition of the thousands of feet of strata. The study of the fossils he 

 argued was also opposed to the theory of subsidence and denudation, 

 since those of the Primary were never found carried into the Secondary 

 beds. 



At the April 4 meeting the discussion was resumed, when Rogers 

 took the ground that an assumption of an upward movement of the sea 

 bottom carried with it the admission of an original depth so enormous 

 as to be incompatible with the accumulation of the material of the 

 earlier strata, unless, indeed, the strata were supposed to be formed 

 exclusively within a moderate distance of the shore. 



We might imagine a series of strata to be successively laid down in a gentle slope 

 approximately parallel to that of the ancient sea bottom, each terminating against 

 this surface without being continued into the profounder depths beyond, and we 

 might suppose the floor to be rising in the region of this accumulation at such a rate 

 as to bring successive tracts, farther and farther from the ancient shore line, within 

 limits of depth admitting of mechanical and orgauic deposition; but in such circum- 

 stances of formation these earlier strata, instead of extending, as they are believed to 

 do, almost continuously over the whole ocean floor, would be seen to determinate at 

 no great distance from the original shore line, but abutting against the bottom at the 

 places where the depth had set a limit to their accumulation. 



No hypothesis of a secular rising of the sea bottom, he therefore 

 argued, could explain the formation of the Appalachian Paleozoic 

 deposit. They indicated, rather, a long period of subsidence of the 

 ocean floor, varied by many and long pauses of upward oscillations. 



Agassiz, in reply, admitted the probable shallowness of the ocean in 

 which the strata Mere deposited, and that during a local upheaval of 

 the shore, the whole sea bottom was probably subsiding, the subsidence 

 being due to shrinkage, caused by the cooling of the earth's crust. 

 This view was accepted by Rogers as amounting to a virtual disclaim- 

 ing of the theory as advanced. 



The removal of B. F. Shumard as State geologist of Texas in 1860, 

 as noted on page 4S7, was immediately followed by the appointment of 



