REPOET OF THE CHIEF OF THE WEATHER BUREAU. 



United States Department of Agricui.ture, 



Central Office of the Weather Bureau, 



Washington, D. C, October 1, 1911. 



Sir: I have the honor to submit a report of the operations of the 

 Weather Bureau during the fiscal year ended June 30, 1911. 



Willis L. Moore, 



CTiief of Weather Bureau. 

 Hon. James Wilson, 



Secretary of Agriculture. 



MOUNT WEATHER RESEARCH OBSERVATORY. 



The work of the observatory has been carried on along practically 

 the same lines as for the previous year; at this time it is chiefly con- 

 cerned with the investigation of the upper air over the United States. 

 The work under this head may be divided into three separate 

 branches, as follows: 



1. Soundings of the upper air over Mount Weather, Va., by means 

 of kites and captive balloons. 



2. Soundings of the air at great altitudes by means of free balloons 

 carrying meteorological instruments. "N^Tiile all preliminary testing 

 and the later computing in this branch of the work are carried on at 

 Mount Weather, the actual ascensions are made in the West, since 

 the proximity of Mount Weather to the Atlantic Ocean on the east 

 makes it inadvisable to send up free balloons from that point. The 

 immediate supervision of all of the work enumerated under headings 

 1 and 2 is assigned to Research Director William R. Blair. 



3. Study of the temperature and pressure changes m the lower 

 layers of the air by means of summit and base stations in the moun- 

 tains of Colorado. 



progress in aerial investigations. 



Considering first the aerial work at Mount Weather, it may be 

 remarked that four years of nearly continuous kite or balloon records 

 have been secured and published. During the fiscal year just ended 

 299 soundings were made by kites and 69 by captive balloons. The 

 average altitude attained by the kites was 2,929 meters (9,609 feet) ; 

 by captive balloons, 2,150 meters (7,054 feet) above sea level. 

 Mount Weather itself is 525 meters (1,725 feet) above sea level. 

 The number of kite flights in which an altitude of a mile above the 

 mountain top (2,134 meters above sea level) was reached during the 

 year was 250; 2 miles, 85. In but 10 flights was an altitude of 3 



155 



