36 Cincinnati Society of Natural History. 



there? In the Carboniferous period a fourth circle of deposition is 

 found, and here, as shown by many successive layers of coal, sand- 

 stone and limestone, can be noted more frequent oscillations than 

 have as yet been recorded from any of the older periods. 



In the report of Prof. N. S. Shaler on the "Investigations of the 

 Kentucky Geological Survey in 1873-74 and '75,'' is an extended 

 discussion of the Cincinnati axis. In this the origin of the sediment 

 forming the rocks of the Cincinnati Group is considered. He states 

 as the result of this investigation his conclusion that some of the beds 

 of the Cincinnati Group were formed in shallow water, and that this 

 water was swept by strong currents. His general conclusion is that 

 ' - the occurrence of salt deposits at one level, pebbles at a point some 

 hundred feet or more higher, of broken shells at yet another hundred 

 feet up in the section, and finally of salt deposits again in the Biue- 

 grass limestone (which forms the summit of the Cincinnati Group), 

 gives us fair reason to conclude that this series of deposits was formed 

 in a region which was balanced near the top of the ancient seas."* 



It is thus seen that Prof. Shaler long ago came to the same conclu- 

 sion as that announced by the writer in 1884.T It is but fair, how- 

 ever, to state that the conclusions of Professor Shaler were unknown 

 to the writer until recently, and that his statement, though made 

 eight or nine years subsequent to that of Professor Shaler, was 

 entirely independent of any observations by others. Professor 

 Shaler' s conclusions were reached through a study of conditions of 

 sedimentary deposit; my own through a study of the trails, burrows 

 and inorganic markings found in the rocks. 



•'-Second Geological Survey of Kentucky, new series, Vol. III., p. 141. 

 TSee this Journal, Vol. VII. p. 93, October, 18S4. 



