WEATHER BUREAU. 53 



on the watershed of Cottonwood Creek, a tributary of the Boise 

 River of Idaho, in the Paradise Creek Valley, on the headwaters of 

 the White River in Arizona, on the watershed of City Creek, near 

 Salt Lake City, Utah, and in the watershed of .Lake Tahoe, Nev. In 

 the last named the measurements were made in cooperation with 

 the agricultural experiment station of Nevada, at Reno. From the 

 nature of the case, intensive measurements of snow depth and density 

 can not be made on any considerable portion of the snow fields of 

 high altitudes ; in fact, grave difficulties are encountered at altitudes 

 between 8,000 and 10,000 feet. The purpose of the bureau in the 

 matter has been to develop methods and apparatus whereby the 

 measurements can be made quickly, and to demonstrate the practical 

 utility of the work by actual surveys over portions of small water- 

 sheds, whence comes the water supply of residents of the lowlands 

 below. A case in point is that of Salt Lake City, Utah, where the 

 water supply is drawn from the Wasatch Mountains to the eastward. 

 In summer, in the absence of sufficient rainfall, the flow of the 

 mountain streams is almost wholly derived from the melting of the 

 winter's snowfall. The usefulness of the method has been so clearly 

 shown to the officials of Salt Lake City for several years past that 

 they have independently conducted a survey over one of the larger 

 watersheds and have aided the bureau on a survey in one of the 

 smaller watersheds which contribute to the water supply of the city. 

 Aside from the importance of these snow surveys from a practical 

 point of view, they also contribute indirectly to our knowledge of the 

 relation which exists between the fundamental phenomena of pre- 

 cipitation and run-off. 



LIGHTSHIP WEATHER STATIONS. 



Through the cooperation of the Bureau of Lighthouses, Depart- 

 ment of Commerce, there has been introduced an entirely new class of 

 weather stations aboard lightships equipped with wireless apparatus. 

 These stations will report upon weather conditions by wireless twice 

 each day. Each will be equipped for measuring pressure, tempera- 

 ture, and wind velocity. At Frying Pan Shoals both the regular 

 and relief vessels have been equipped, but reports have not yet been 

 received. At Nantucket Shoals one ship has been equipped, but 

 reports have not yet been rendered. Plans are under way for equip- 

 ping the Heald Bank light vessel in the near future. 



EVAPORATION WORK. 



Although the demand for the installation of evaporation stations has 

 increased, the introduction of class A stations has progressed rather 

 slowly, because the funds for purchasing equipment and the facilities 

 for administration are not considered equal to a rapid extension of 

 this work. Eight stations have been equipped and are now rendering 

 monthly reports. 



STORM- WARNING STATIONS. 



The storm-warning stations of the bureau on June 30, 1916, were 

 as follows : 



Paid stations, 191, a decrease of 2 during the year. 



