98 PAL5:0NT0L0GY OP NEW-YORK. 



formation, that it is impossible at the present time to parallelize the 

 deposits of these two regions of country. It is only by a considera- 

 tion of the physical conditions of the period that we may arrive at 

 some conclusion. 



From the gradual recession of the ocean to the southward during 

 the deposition of these limestones, and the manner of their overlapping, 

 it is evident that there is a certain degree of unconformity among the 

 jnembers of the series. This becomes more manifest when we carry our 

 examinations into the Coal measures, which lie unconformably over all 

 these limestones, except, perhaps, the upper one ; and also, to some 

 extent, over the Devonian and Silurian rooks beneath. 



The recession, and the consequent unconformability, could only have 

 resulted from a movement in the pre-existing land or sea bottom. 

 Further evidences of such a movement are to be seen in the Cincinnati 

 axis, which, extending from Canada to Tennessee, has elevated the 

 lower rocks ; and it may be that the movement producing this axis 

 •was initiated prior to the deposition of these limestones. 



Admitting this view of the subject, the elevation of that axis, or the 

 subsidence of the sea bottom on the east and on the west, may have 

 so far divided the waters that the sediments derived from the east 

 were not carried beyond that line ; while to the west there may 

 have been a quiet, shallow sea, fitted for the development of these 

 faunas, and for the accumulation of the calcareous material forming 

 this great series of limestones. This view may be sustained by the fact 

 that nowhere, so far as I know, do the Carboniferous limestones appear 

 beneath the Coal measures on the east of the Cincinnati axis, in Ohio 

 or Kentucky. 



I regard this question as one open for investigation ; and we shall 

 arrive at a true solution of the problem much sooner by studying the 

 long lines of outcrop in the west, than by any discussion of probable 

 physical conditions. It is a question of the highest interest for the true 

 exposition of our geology. 



