GEOLOGY OF THE NEW YORK CITY AQUEDUCT 21 



discussions. Where such cross reference is too cumbersome, the 

 items are repeated in preference to leaving the case obscure. Thus 

 it is hoped to make each case a unit, and the whole series useful 

 and understandable. 



Gathering data 



In the accumulation of data all the members of the engineering 

 corps^ as well as the men acting only in a consulting capacity have 

 taken part. Necessarily the bulk of the exact data has been 

 gathered by the men all the time on the ground and whose duty it 

 was to superintend explorations. The care and intelligence with 

 which this has been done is notable. A considerable proportion of 

 the labor of manipulating the accumulated data and interpreting it 

 so as to reach an explanation of conditions and formulate conclu- 

 sions has been assumed by the consulting men. 



Too much credit can not be given to the heads of departments 

 and divisions for the open-handed way in which all needed facts 

 were held available at all times for comparison and guidance toward 

 sound conclusions. The information upon which investigations 

 have been initiated have been chiefly the following: 



1 The geologic maps and reports of the New York State Survey 



2 United States topographic maps 



3 Geologic folio no. 83, New York city folio 



4 Earlier engineering records and reports 



5 Reports of special commissions on water supply 



1 In this worki no group of men have had so direct responsibility as the 

 division engineers. The success with which so many complicated explora- 

 tions were carried out is chiefly due to their constant care and foresight 

 and perseverance and the able assistance of their staff. Those who have had 

 especially important divisions for the geological problems involved are given 

 due credit in the discussions of part 2, of this bulletin. It is easy, how- 

 ever, to neglect sufficiently full acknowledgment of their services in gather- 

 ing and formulating data of this kind. Among those having charge of the 

 most important exploratory work the following names should appear : 



James F. Sanborn, for sometime assigned to geologic work on the North- 

 ern aqueduct. 



William E. Swift, in charge of the Hudson river explorations. 



William W. Brush, in charge of the early New York city explorations. 



Lazarus White, in charge of the Rondout valley explorations. 



Lawrence C. Brink, in charge of the Wallkill division explorations. 



J. S. Langthorn, in charge of the exploratory work at the Ashokan Reser- 

 voir. 



Wilson Fitch Smith, in charge of work at Kensico dam, and 



A. A. Sproul, in charge of the Peekskill creek and Sprout brook explora- 

 tions. 



