REVERSALS OF DRAINAGE 



481 



From the many borings, Mr. Clute found that there is a bed of pure 

 salt 200 feet thick, and also other beds of salt and shale, so that the 

 whole series is 900 feet thick. Tlie formation extends northward and 

 underlies the widest part of Seneca Lake, rising at the rate of nearly 25 



FiGUEB 1. — Sketch Map of Region adjacent to Seneca and Cayuga Lakes 

 Showing the pre-Glacial drainage basins 



feet per mile. The overlying strata are there broken and undulating, as 

 if a local subsidence had occurred. 



From the absence of a rock barrier as found by borings and on account 

 of the post-Glacial northward warping, it appears that Cayuga Lake is 

 not a rock basin; but no borings have been made in the line of Seneca 



