266 ANNUAL liKPORTS OF DEPARTMENT OF AGRICULTURE. 



am) until April 22, 1912, at Washinglon. The intensity of direct 

 solar radiation was occasionally measured at Washington by means 

 of an Angstrom pyrheliometer^ and at Madison, Wis., throughout 

 the year whenever atmospheric conditions would permit, and after 

 November 10, 1911, at Lincoln, Nebr., by means of a Marvin pyrheli- 

 ometer. Preparations had been practically completed for the installa- 

 tion of a Marvin pyrheliometer on the Government reservation at 

 Santa Fe, N. Mex., in April, 1912. The removal of the Weather 

 Bureau office at Santa Fe from the Federal building necessitated 

 delay and a charige in plans, but the pyrheliometer will probably be 

 installed at the present office in Santa Fe before the close of 1912. 



The measurements of the intensity of direct solar radiation made at 

 Madison, Wis., during the two years ending with June, 1912, have 

 been prepared for publication in the Bulletin of the Mount Weather 

 Observatory. The most interesting feature of these results is the 

 high intensity measured each year during the months of February, 

 March, and April. Some measurements of the intensity of radiation 

 reflected from cloud surfaces, obtained at Madison and Mount 

 Weather, have been prepared for publication in the Bulletin, and also 

 some measurements of sky polarization and the intensity of both 

 direct and diffuse radiation, made at Mount Weather during the 

 dense haze that prevailed on June 10 and 11, 1912. Radiation meas- 

 urements not only give definite information with regard to an im- 

 portant climatological element, but after we once learn to interpret 

 them they must also serve as valuable integrating measurements of 

 atmospheric conditions at all levels. 



The effect of smoke upon the climate of cities constitutes a problem 

 in atmospheric transparency that received attention by the Weather 

 Bureau during the year. The results will be published by the 

 University of Pittsburgh, in connection with the results of other 

 studies of the smoke problem. 



Plans for the coming year at Mount Weather. — So far as the 

 aerial work at Mount Weather is concerned, it is proposed to modify 

 the plan heretofore followed to the extent of not attempting to obtain 

 a kite or balloon flight on each day regardless of the weather condi- 

 tions, unless there is a type of weather over the station which it is 

 desired to explore. The time so saved will be utilized in work on 

 other problems of the atmosphere which relate less directly to the 

 forecast work of the service. A beginning has been made on one 

 of these problems, namely, the nucleation of the atmosphere at the 

 low temperatures and pressures which prevail at the higher levels. 

 It is hoped to continue kite flights throughout the 24 hours on 

 selected dates, with a view of studying the diurnal temperature wave 

 in the atmosphere, a beginning in which has already been made. 



It is our purpose to utilize the equipment at Mount Weather in 

 the stud}'^ of such other problems in the practical work of the service 

 as may be susceptible of laboratory treatment, and also to under- 

 take photometric measurements of the intensity of sky light under 

 different atmospheric conditions. Aside from the economic value of 

 such measurements, they will be of meteorological interest because 

 of their close relation to radiation intensity and atmospheric 

 transparency. 



