WEATHER BUREAU. 175 



facilities. It is hoped to have the work well under way by August 

 or September, 1910. Two watersheds of similar topography and of 

 limited drainage areas have been selected, and the necessary weirs 

 and instruments for the measurement of stream flow will be located 

 at an approximate altitude of 9,500 feet above mean sea level, the 

 drainage area extending upward to an elevation of about 10,500 feet. 



It is proposed to measure the flow of the two streams for a suffi- 

 cient period, probably eight or ten j-ears, to demonstrate their be- 

 havior with equal forest cover. One of the watersheds will then be 

 denuded and streamflow measurements continued on both for another 

 period of eight or ten years, by which time it is probable that the 

 effects of the denudation, whatever they may be, can be stated in 

 positive terms. In order that all the climatic factors that affect or 

 modify stream flow may be considered, a complete equipment of mete- 

 orological instruments will be provided and observations will be taken 

 several times daih'. Automatic instruments will afford continuous 

 and permanent records of pressure, temperature, wind direction and 

 velocity, sunshine, jDrecipitation, and evaporation. 



The proposed period of observations is none too long, and in view 

 of the possible influence of the investigation upon certain questions 

 of public polic3% and in the interests of scientific research, it may be- 

 come necessary later on to extend it. 



INSTRUMENT DIVISION. 



About 200 stations of the Bureau are now fully equipped with re- 

 cording instruments, 3,000 cooperative observers are supplied with 

 maximum and minimum thermometers, rain gauges, and instru- 

 ment shelters, and about 150 stations are provided with steel towers 

 and high-2:)0wer oil or electric lanterns for the display of storm 

 warnings. 



The new stations at St. Joseph, Mo., and Lansing, Mich., at which 

 Weather Bureau buildings have recently been erected, were fully 

 equipped with standard sets of instruments during the year. The 

 regular station at Brawle}^, Cal., maintained in connection with the 

 observations on evaporation at the " Salton Sea," was closed in May, 

 1910, and the equipment transferred to the special station at Wagon 

 Wheel Gap, Colo. 



The kiosks installed a year ago in some of the large cities have 

 proved very popular, and more requests for these structures have 

 iDeen received than it has been possible to grant. Six kiosks were 

 purchased during the year; three have been erected at prominent 

 points in Hartford, Duluth, and Richmond, but the work of installa- 

 tion at Indianapolis, Salt Lake City, and Atlanta is not yet com- 

 pleted. 



NEW WORK AND APPARATUS. 



During the year Professor Marvin perfected certain new methods 

 of measuring the intensity of solar radiation in absolute units of heat 

 by the use of the electrical resistance thermometer. So far as known, 

 this method has never been employed heretofore. It seems to possess 

 great advantages over customary forms of the pyrheliomoter, owing 

 especially to the fact that the thermal capacity of the apparatus can 

 easily be determined from time to time in the ordinary course of 



