GEOLOGY OF THE NEW YORK CITY AQUEDUCT I4I 



Rondout siphon statistics 



1 Total borings on the siphon line. Three different boring 

 equipments have been used owned by different parties and records 

 have been kept so that the work of each can be followed or com- 

 pared with the others. 



On this division the Board of Water Supply owned and operated 

 one machine with their own men, another equipment was owned 

 and operated by C. H. McCarthy, while a third which finally did 

 a majority of the work, belonged to Sprague & Henwood, Con- 

 tractors, of Scranton, Pa. 



The totals of different general types of material penetrated by 

 these machines are as follows : 



Feet Feet Total Per cent 



of of feet of of core 



drift rock depth saved 



a B. W. S. Equipment 1740.5 2175.5 39i6 89.4 



^Sprague & Henwood 3647 6831 10478 60.04 



c McCarthy machine 181 1228 1409 78. 1 



i 

 The average saving of core by all machines, cutting all kinds of 



bed rock was 75.96;^ 



2 Core recovery from various strata. So nearly as can be 

 done the strata represented in the drill cores have been identified 

 and summarized as to total penetration and core saving. The core 

 saving is a factor of prime importance in judging of the quality of 

 rock and its freedom from disturbance. The following items are 

 gathered from a study of the whole series. 



a Holes 6, 10, 12, 13, 15, 17, 18, 21, 22 and 25 penetrate Helder- 

 berg limestone, a total combined depth of 1096 feet. Individual 

 holes vary in core saving from 39.3;^ (no. 13) to 95.3^ (no. 15). 

 The average core saving is 78.19;^. 



b Holes 8 and 9 are in Onondaga limestone with a total pene- 

 tration of 197 feet. The core saving varies from 56.2^ to 92.8^ 

 with an average of 74.5^. 



c Holes II, 19, 20, 23, 24, 2"/ penetrate Hudson River shale and 

 together represent a total of 696.5 feet. The core saving varies 

 from i6.6fc to 89;^, with an average of 42.1^. 



d Holes 6, 10, II, 12, 14, 16 and 20 cut High Falls shales to a 

 combined total of 410 feet. The saving varies in different holes 

 from 17^ to 83.3^, with an average core saving of 44.5^. 



e Holes 8 and 26 penetrate Esopus shale and penetrate ^6 feet. 



