THE IRPJGA TlOX A GE. 81 



an appropriation should be made, the constructing engineers would 

 modify many features, but the examinations have been carried far 

 enough to afford a close approximation of the cost. A considerable 

 number of reconnoissance surveys can be made during the field sea- 

 son, but large expenditures are required for detailed examinations, so 

 that it has been possible to complete comparatively few of the 

 latter. 



The reservoir sites surveyed or segregated have been listed or de- 

 scribed in various annual reports of the Survey, beginning with the 

 Eleventh. Reference should be made to these volumes for details. 

 During the last year, 1899, surveys in great detail have been made of 

 three sites on the Gila River in Arizona and of one large reservoir in 

 Hetch Hethby Valley on the head waters of Tuolumne River, Califor- 

 nia, also of several sites on the Rio Grande in New Mexico. The re- 

 sults of these surveys will be given in the Twenty-first Annual Report, 

 if not in earlier publications. 



It is proposed to continue these surveys as rapidly as funds may 

 be available, giving precedence to those where results have the great- 

 est public importance and interest. As a result of several years' ex- 

 perience, this office has a corps of competent engineers, together with 

 instruments and equipments, and is carrying forward the work prob- 

 ably more rapidly and economically than such work ordinarily can be 

 done by private or corporate enterprise. The question of expense has 

 been carefully considered and the methods in use have been adopted 

 to secure the maximum efficiency at a minimum cost, consideration be- 

 ing given, of course, to the importance and the permanent character 

 of the results. 



EXTENSION OF SURVEYS. 



The Geological Survey is often requested to examine reservoirs in 

 this and that locality, and is asked to do work, the aggregate cost of 

 which would far exceed its available funds. With the amount of mon- 

 ey that has been appropriated it is possible to do only a limited amount 

 of work each year, and it has been found economical to f >llow some- 

 what closely the progress of the topographic mapping. If the public 

 in general take an interest in the matter and funds are provided, work 

 can be expanded by an increase in the corps of skilled men. 



Another question frequently asked, is whether the Government 

 will build these reservoirs. That is a subject upon which this office 

 cannot express an opinion. The duty of the Survey is to ascertain 

 the existence of reservoir sites and the cost of storage works, whether 

 these are ultimately built by individuals, by corporations or by the 

 State or Federal Government. Some of the reservoirs surveyed or 

 examined have already been constructed, others may be, but the most 

 important are of such magnitude that they cannot be built except by 

 the use of public credit in one form or another. It is to develop these 



