8 ORIGINAL CONNECTION OF THE EASTERN AND 



with a thin coating of beds which have since been brought to utter ruin 

 by the action of various agents. In order to avoid the charge of incon- 

 sistency that may be brought against my position on this point, I must 

 endeavor to reconcile this view of the condition of the Cincinnati axis 

 during the coal period with what I elsewhere held concerning the physi- 

 cal history of this important mountain fold. I have long been satisfied 

 that the Cincinnati axis began to lift itself above the sea floor very early 

 in the Upper Cambrian period. The fact that in the horizon of the cal- 

 ciferous sandstone we have an abundant supply of very saline brines, is 

 of itself proof that at the time of this horizon there was, from time to 

 time, an exposure of the deposits making on the old sea floors above the 

 surface of the sea. Again, in the horizon of the Cincinnati group, we 

 have a repetition of the evidence of shallow water or low-lying islands. 

 I am inclined to think that there can be no reasonable doubt as to the 

 extreme antiquity of this axis. It is to be remembered, however, that 

 the subsidence of the continent at various times in its history has been 

 great enough to have entirely submerged this low axis beneath the sea. 

 A sinking of the continent by twelve hundred feet would bring the ocean 

 over the top of this axis, though it might not have any distinct effect 

 upon the altitude of the axis as determined by its other relations. There 

 can be little doubt that during the formation of the Black, or, as I have 

 termed it in the Kentucky reports, the Ohio Shale, the whole of this Cin- 

 cinnati axis was deeply buried beneath the sea. The entire absence of 

 pebble beds in the deposits of the Waverly and higher Subcarboniferous 

 " beds is an equally strong argument against the exposure of this axis dur- 

 ing the time when they were being laid down. Nor in the time of the 

 millstone grit, when pebbles were swept by strong currents in a lifeless 

 sea from the mountains of Carolina, and possibly from the Laurentian 

 Hills as well, far and wide over our ocean floors, do we find a trace of 

 the waste this axis would have given if it had been above the level of 

 the sea. There is, therefore, no reason to look upon it as forming a nat- 

 ural barrier between the eastern and western districts of Kentucky in the 

 times immediately anterior to the coal period. It is far more reasonable 

 to suppose that while this axis was traced out in our rocks from an 

 early age, it was not until after the close of the carboniferous period 

 that it took on its present form, and became so dome-shaped in the 

 region about Nashville and in the district of which Lexington is the 



