90 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



winds from different directions, the average and extreme velocities 

 encountered, and other data of special interest and value to aviators. 

 This " survey " is confined to those portions of the country east of 

 the Rocky Mountains, since free-air observations farther west are too 

 few for the purpose. Additional stations in the West and a few 

 more in the East than we now have are urgently needed, in order to 

 give complete information for all parts of the country. 



At the request of the National Advisory Committee for Aero- 

 nautics the preparation of a report on "Standard atmosphere" was 

 undertaken and completed. It has been published by that commit- 

 tee as Report No. 147 and will later be included in the annual report. 

 In it are discussed the need of a standard set of values of pressure, 

 temperature, and density at various altitudes, and the desirability 

 of adopting such values as are most in accord with actual average 

 conditions in order that corrections in individual cases may be as 

 small as possible. To meet this need, so far as the United States 

 is concerned, all free-air observations obtained by means of kites 

 and sounding balloons at several stations in this country near latitude 

 40° north have been used, and average values of pressure, tempera- 

 ture, and density, based upon these observations, have been deter- 

 mined for summer, winter, and the year, and for all altitudes up to 

 20,000 meters (65,000 feet). These values have been adopted by 

 the National Advisory Committee for Aeronautics for use ais 

 " standard " in this country. 



CLIMATOLOGICAL WORK. 



In the main, the regular work of the division w^as carried forward 

 as usual and all routine matters were well in hand at the close of 

 the year. 



The manuscript tables, charts, and text for the several publications 

 of the bureau, weekly, monthly, and annual, were prepared and 

 placed in the hands of the proper officials on the several dates speci- 

 fied. Likewise the thousands of meteorological reports from the 

 regular and cooperative observers have received increased scrutiny 

 to assure the accuracy required in the material placed before the 

 public through the various reports issued by the bureau. 



One of the main lines of work in the division, the furnishing of 

 weather information upon written or other requests from all classes 

 of persons and interests requiring such information, has continued 

 with the usual activitv, and this, too, has been met in a satisfactory 

 manner, as indicated^ by the numerous acknowledgments received, 

 which expressed entire satisfaction with the promptness of the in- 

 formation furnished. , 



Cooperative wo/^y^.— The extensive lines of cooperation by which 

 the Weather Bureau secures valuable observations of weather con- 

 ditions free of charge, save for the necessary observing outfits, have 

 continued as in the past. Hearty interest m this cooperation is 

 manifested in the thousands of reports carefully prepared day 

 after day, month after month, and for indefinite years, and for- 

 warded promptly to this office and to the State section centers 



The number of these cooperative workers has not materially in- 

 creased over those of previous years. In fact, effort to reduce the 



