WEATHEE BUBEAtf. 65 



Twenty-eight observations to an average height of 2,850 meters 

 were made in October and November, 1915. The addition of a man 

 to the station force in December, 1915, made it possible to begin at 

 that time daily observations injthe free air. In addition to the daily 

 observations, when opportunity offered, series of observations con- 

 tinuing for a period of 30 to 36 hours were made. During a series of 

 observations a kite flight is made every three to three and a half 

 hours. The data obtained enable us to follow atmospheric changes 

 in considerable detail. In connection with the daily observations, a 

 daily telegram, giving atmospheric conditions observed at one or two 

 selected levels, is sent to the forecast offices of the Weather Bureau 

 at Washington, D. C, and Chicago, 111. 



In all, 350 observations to an average height of about 2,800 meters 

 have been made up to June 30, 1916. Of these, 88 were made in 11 

 different diurnal series, 28 were made before December 1, 1915, and 

 the others were made as daily observations. 



Owing to the impossibility of importing meteorographs of the 

 kinds we have been using, or of getting parts for them, the work 

 of rebuilding, repairing, and calibrating these instruments has been 

 especially heavy during the past year. In addition to this, a work- 

 ing model of a self-recording balloon theodolite has been constructed 

 and preliminary work done on a simple form of meteorograph and on 

 a manometer for use in calibrating pressure elements of meteoro- 

 graphs directly in millibars. An additional kite reel was built for 

 us by an outside firm, and delivered in November, 1915. Some neces- 

 sary calibration on the reel has since been completed by us and the 

 machine made ready for issue to a new aerological station. 



It has been impossible for the past year or two to import rubber 

 balloons such as we use in making aerial soundings to great heights. 

 We have therefore gone into the subject of the manufacture of these 

 balloons with interested rubber companies in this country, in an 

 effort to have them produced here. A number of sample balloons 

 have been prepared and tested. Some of these have been of fair 

 quality, but not yet suitable for our work. 



SEISMOLOGICAL INVESTIGATIONS. 



The work of collecting and publishing earthquake data, begun De- 

 cember 1, 1914, has been continued during the past year. These data 

 are of two kinds — noninstrumental reports of earthquakes felt, and 

 instrumental records, often of quakes wholly imperceptible to the 

 senses. The noninstrumental reports are rendered by all the regular 

 stations of the bureau, nearly 200 in number, and also by nearly all 

 the bureau's 4,500 cooperative observers. The instrumental records 

 published by the bureau have been obtained in part by instruments 

 owned and operated by the bureau itself, one at Washington, D. C, 

 and another at Northfield, Vt., and partly through the cooperation of 

 18 additional stations distributed from Panama to Alaska and from 

 the Hawiian Islands to Porto Rico. 



During the calendar year 1915, 150 earthquakes were felt within 

 the borders of the United States proper. The great majority of these 

 produced no damage whatever, but some three or four were distinctly 

 severe, though only two occurred in populous regions. 



