REPORT OF THE DIRECTOR IQII I3 



of modern petrography. The quality of sands and gravels for gen- 

 eral construction purposes may be approximated in a similar 

 manner. 



The importance which the present scheme of highway improve- 

 ment in the State has assumed requires that every possible advantage 

 be taken of the situation with regard to the occurrence and avail- 

 ability of road-making materials. It is not necessary at this time to 

 set forth in detail the geological considerations which enter into 

 the subject. One element among many to be considered is the prac- 

 tical absence of suitable rock materials over the large area occupied 

 by the Devonic shales and thin-bedded sandstones in the southern 

 tier of counties, and the possible application of other local materials 

 for use on the highways of that section. It would appear desirable 

 to have a systematic inventory of the resources that may be drawn 

 upon for road construction. 



Another practical side of geological investigation is illustrated in 

 the engineering of large projects which involve unusual care or 

 discrimination in dealing with rock materials. In such cases the 

 correct interpretation of structural features and processes of rock 

 change that are in progress is often of considerable moment, if not 

 on occasion of critical importance. The foundation work of large 

 structures like dams and bridges that must be secured against the 

 very slight but cumulative effects of physical agencies, and the exca- 

 vation of canals and tunnels are examples of this kind. 



A notable instance of the varied bearings which geology may have 

 upon engineering is afforded by the construction of the Catskill 

 aqueduct for the supply of water to New York City. The difficulty 

 of the undertaking can scarcely be appreciated without a knowledge 

 of the physical characteristics of the country in which the work 

 had to be accomplished and the complications arising from the magni- 

 tude of the project. The engineering plans have been formed only 

 after most extensive exploration of the features related to the sur- 

 face and rock topography, character of the formations, tectonic 

 structures, underground water circulations, and other matters which 

 from the nature of the problem might influence the course or success 

 of the work. To assemble and interpret the data a staff of geologists 

 was maintained and was in constant touch with the situation. An 

 insight into the manifold character of the scientific investigations 

 and their relation to the conduct of the operations are given in a 

 recent volume ^ prepared by a member of the geological staff. To 



^ Geology of the New York Aqueduct, by Charles P. Berkey. N. Y. State 

 Museum Bulletin 146, igii. 



