62 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



ing thereon to face on Main Street, and effect greatly needed perma- 

 nent improvement in the equipment at that station. 



An acceptable bid was finally secured for the construction of a 

 new telegraph office and observatory building at Cape Henry. Va., 

 authorized by Congress in 1917, This building will be completed 

 within the appropriation therefor and be ready for occupancy in 

 September, 1918. 



The status of the Independence, Cal., station was changed from 

 that of a special meteorological to a fully equipped station, occu- 

 pying rented quarters. 



AEROLOGICAL INVESTIGATIONS. 



During the year considerable enlargement in the aerological work 

 of the Weather Bureau was effected, under the provisions of an item 

 in the Army bill, which reads as follows : 



For the establishment and maintenance by the Weather Bureau of additional 

 aerological stations for observing, measuring, and investigating atmospheric 

 phenomena in aid of aeronautics, including salaries, travel, and other expenses 

 in the city of Washington and elsewhere, $100,000, to be expended under the 

 direction of the Secretary of Agriculture. 



In accordance with this act, sites for aerological stations in addi- 

 tion to the one already established at Drexel. near Washington, 

 Nebr., have been selected at Broken Arrow. Okla., Ellendale, N. 

 Dak., Groesbeck, Tex., Leesburg, Ga., and Royal Center, Ind. This 

 distribution is as favorable as possible with the limited number of 

 stations to secure observations of free air conditions over a large 

 portion of the country. Installation of equipment has been com- 

 pleted at the Ellendale station, and free air observations were begun 

 in December, 1917. The other four stations are being equipped as 

 rapidly as the difficulties of obtaining suitable apparatus permit. 

 Surface meteorological observations are already being made at each 

 of the stations. 



Free air observations, by means of kites, were continued at the 

 Drexel Aerological Station during the entire year, and have been 

 obtained at the Ellendale Aerological Station since December 17, 

 1917. The data thus obtained include observations of atmospheric 

 pressure, temperature, humidity, wind direction and velocity, cloud 

 altitude and movement, and, at Drexel. electric potential. Daily 

 telegraphic reports of conditions at one or more selected levels were 

 sent to the forecast center of the Bureau at Washington, D. C, on 

 all days when flights were made. At Drexel, in addition to the daily 

 flights, series of observations covering a period of about 30 hours 

 were made whenever conditions were favorable. The data thus ob- 

 tained enable the bureau to follow in considerable detail the diurnal 

 changes at different altitudes. In all, 478 observations were made 

 from July 1, 1917, to June 30, 1918. Of these, 134 were made in 18 

 different series, the remaining 344 being made as daily observations. 

 The average altitude reached in all flights was about 3.000 meters. 

 At Ellendale 163 flights were made from December 17. 1917. to June 

 30, 1918, the mean altitude being about 2,400 meters. 



The free air data obtained at Drexel from April to December, 

 1916, inclusive, were published in Supplements 7 and 8 (Aerology 

 Nos. 3 and 4) of the Monthly Weather Review; those obtained dur- 



