178 NEW YORK STATE MUSEUM 



than is already shown in holes no. i and no. 11 [see profile and 

 cross section, fig. 33]. The elevation indicated by no. 3 D is be- 

 lieved to be misleading because of the use of a drill that was 

 capable of destroying a part of the ledge rock that would usually 

 core. The points believed to be weakened by structural disturbance 

 and therefore most likely to be attended by erosion and stream 

 action are in the vicinity of hole no. 11, near the present creek, and 

 hole no. 25, near Peekskill Hollow road. 



4 Buried channels 



From the accompanying cross section it will be seen that the 

 drift cover is more than 100 feet thick over large portions of Peeks- 

 kill valley. The rock floor in the middle of the valley averages 

 approximately 25 feet A.T., while the drift surface except where 

 cut out by stream erosion is at about 125 feet. In the rock floor 

 there are two depressions, the large one wholly within the lime- 

 stone belt and the smaller following the limes tone-phy Hi te contact. 

 There is not much difference in their depth so far as explored, but 

 there is a possibility of a somewhat deeper notch in each one. The 

 depth to which some of the limestone beds are decayed by under- 

 ground circulation would lead to the belief that a deeper notch may 

 exist. 



The drift cover is chiefly partially assorted sands and gravels in 

 the central portion of the valley, and more of a till on the eastern 

 valley side. It is noteworthy that the present Peekskill creek lies 

 far to one side following closely the phyllite wall. 



5 Underground water 



Present elevation above sea level is so slight that there is appar- 

 ently little encouragement of deep underground circulation. But 

 at certain points the rock has been found to be very badly decayed 

 to a great depth — to at least 200 feet below sea level. This is 

 believed to have been accomplished chiefly at a time when the re- 

 gion stood at a higher level. Hole no. 22 is especially notable in 

 this connection. A comparison of the figures of core saving is one 

 of the best lines of evidence on this question. Wherever data are 

 at hand the percentages of saving have been put on the cross sec- 

 tion. Hole no. 29, for example, shows a saving of only ufc in the 

 lower 250 feet, reaching a depth of 297 feet below sea level. 



The present water table profile is shown on the cross section. A 

 great body of water stands in the assorted sands directly upon bed 



