BLAIR— AEROLOGY. 



201 



Fig. 13. Mean of Wind Observations in " Lows " at 4000 Meters above Sea 



Level, 1907-1912. 



closed. The change in direction of the wind with height may be 

 shown in a general way by Table I., based upon data obtained at 

 the Mount Weather Observatory. 



Tables II. and III. show frequency and speed, respectively, of 

 winds at different levels above Mount Weather. Table II. indicates 

 the decided increase in frequency of west and westerly winds with 

 height. The increase in wind speed with height is rapid for the 

 first 500 to 700 meters above the earth's surface, less rapid at 

 higher levels. 



In the study of any convective system the temperature distribu- 

 tion in the system is of prime consideration. The vertical distribu- 

 tion of temperature is of interest to the aeronaut, not only in connec- 



