GEOLOGY OF THE NEW YORK CITY AQUEDUCT I9 



easier simply to know that they must ultimately be stated in terms 

 precise enough for the use of engineers, and to know furthermore 

 tliat the real facts are to be laid bare when construction begins and 

 as it progresses. But from another viewpoint it may be regarded 

 as an exceptionally fine opportunity to study applied geology in its 

 best form and to see the intimate interrelationship between an 

 engineering enterprise of great public utility and a commonly con- 

 sidered more or less obscure science. The services of geology have 

 been seldom so consistently employed in earlier undertakings of 

 similar character. It is to be hoped that the accompanying illus- 

 trations of the practical application of geologic knowledge and facts 

 to engineering plans and practice may add to the appreciation of 

 the commonness and variety of such service in many everyday 

 affairs. Furthermore, this unique enterprise, the like of which for 

 magnitude and complexity has never before been attempted, has 

 given to those whose good fortune has brought them into working 

 relations with its problems, the opportunity of a generation in their 

 chosen field.^ The success stages from isolated observations, 

 inference, hypothesis, theory, conclusions, and fully proven facts 

 are all represented. The steps more or less fully coincide with the 

 degree of confidence observable in the tone of advisory reports to 

 the engineers in charge — representing suggestions, recommenda- 

 tions, or specific advice. 



It is one of the cherished wishes of the writer of this bulletin 

 that some of these problems may be presented in such manner as 

 to serve a distinct educational purpose. For this reason in part, 

 deeming it even of greater importance than the m.ere enumeration 

 of newly discovered facts, the writer has chosen to treat the sub- 

 ject from the standpoint of an Instructor illustrating the develop- 

 ment of working conclusions. It is certain that not all readers have 

 the same degree of preparation or acquaintance with the subject- 

 matter, and it may therefore be useful to include many things that 

 some may well pass by. No excuse is offered except that such 

 method of treatment, in behalf of the general intelligent public that 

 it is hoped to reach, seems to the author to be advisable. 



1 W. O. Crosby of the Massachusetts Institute of Technology'. James 

 F. Kemp and Charles P. Berkey of Columbia University have constituted 

 the staff of consulting- geologrlsts throughout most of the exploratory' work. 



