WEATHER BUREAU. 63 



ing 1917 have been sent to the printer: those during the first half 

 of 1918 have been reduced and will shortly be ready for publication. 

 In addition, considerable work has been done in the preparation of 

 a summary based on all free air data thus far obtained at Drexel. 

 In its purpose to render the greatest possible assistance in the 

 vigorous and successful prosecution of the war, the bureau has co- 

 operated with various branches of the United States Army in the 

 following ways: 



1. Papers on "Meteorology and Aeronautics," "Mean Values of 

 Free Air Barometric and Vapor Pressures, Temperatures and Den- 

 sities over the United States," and "The Turning of Winds with 

 Altitude" were prepared and published and copies have been fur- 

 nished for the information and use of the Aviation and Artillery 

 Services. 



2. Information relative to free air conditions at certain specified 

 times in this countrj^ and in different parts of Europe has been fur- 

 nished whenever requested. 



3. Instrumental equipment, including kite meteorographs, has 

 been supplied for the use of the American Expeditionary Forces and 

 the training camps in this country. 



4. In connection with special experimental tests, temporary field 

 stations have been established and kite flights made at Ellington 

 Field, Tex., Potomac Park, Washington, D. C, and Aberdeen Prov- 

 ing Grounds, Md. 



WORK IN CLIMATOLOGY. 



The regular climatological work of the Bureau was carried for- 

 ward during the year by the large corps of cooperative observers 

 as usual. Many changes occurred during the year in the observing 

 force, arising largely from the necessities attending the war. Some 

 of the younger observers have responded to the call for military 

 service, and others have voluntarily assum-ed lines of war work 

 which have either required their absence from home or taken up 

 their time to such an extent as to interfere with the observations. 

 Despite the added duties arising out of the var it is gratifying to 

 note a constant improvement in the character of the observations 

 furnished. The promptness of the observers in forwarding their 

 monthly reports is deserving of the highest commendation. 



No material effort has been made during the year to increase the 

 number of stations, but rather to effect a more satisfactory distri- 

 bution, improve their equipment, and secure better reports. 



Corclial cooperation continues between the Weather Bureau and 

 other branches of the Government, and reporting stations, under the 

 supervision of employees of these bureaus, have been established in 

 regions where it would be impossible to secure other observers. 

 This is particularly true as regards the Forest, Indian, and Reclama- 

 tion Services, whose employees have given valuable reports from 

 otherwise inaccessible regions, mostly in the high mountains of the 

 West. _ . 



The policy of more frequent inspection of cooperative stations in- 

 augurated recently has continued, and the beneficial results became 

 at once apparent. This has been especially noticeable in the Alaska 

 section, which has only lately been reorganized and put upon a basis 



