REPORT OF THE SECRETARY. 191 



AIR DRAINAGE. 



In addition to the exploration of the free air by means of kites and 

 balloons, observations on the fluctuations in air temperatures in a 

 cross section of the atmosphere extending from the Shenandoah Val- 

 ley on the west across the Blue Ridge to the Loudoun "Valley on the 

 east have been made. This is a study of air drainage, and is chiefly 

 of interest to horticulturists. 



SOLAR RADIATION. 



The observatory has also conducted a series of measurements of 

 the amount and intensity of solar radiation, the degree of absorption of 

 the earth's atmosphere, and the polarization of blue sky light, and an 

 automatically recording device has been installed whereby a con- 

 tinuous record is made of the intensity of the radiation received from 

 the sun and sky upon a horizontal surface. Arrangements have also 

 been perfected to secure measurements of solar radiation at other 

 stations in the western portions of the country. 



SCHOOL OF INSTRUCTION. 



A part of the physical laboratory building has been set apart for 

 use of a Weather Bureau school of instruction, wherein it is aimed 

 to teach new employees of the weather service the duties required of 

 them and to give them actual experience in all phases of the work 

 that is required of assistant observers in any part of the service. This 

 new feature of the work at Mount Weather satisfies a want that has 

 been keenly felt during the last 20 years. 



The results of the observations and investigations made at Mount 

 Weather are regularly published in the bulletin of the Mount Weather 

 Observatory, a publication devoted to the discussion of the scientific 

 investigations of atmospheric phenomena. 



LIBRARY. 



At the central office of the Weather Bureau in Washington is main- 

 tained a library of meteorological and climatological literature, in 

 which has been brought together from every part of the world prac- 

 tically all the published material available on these and kindred 

 scientific subjects. In 1896 there were 20,940 books and pamphlets 

 in the library ; this number has since been increased to a total of 34,310 

 volumes. 



AGRICULTURAL STATISTICS. 

 CROP-REPORTING SYSTEM. 



One of the first undertakings of this department soon after its 

 creation in 1862 was the adoption of a crop-reporting system for the 

 purpose of ascertaining and publishing monthly information con- 



