BLAIR— AEROLOGY. 



203 



Fig. 17 shows the vertical distribution of temperature to be ex- 

 pected in the different quadrants of the high-pressure area, based 

 on five years of observation at Mount Weather, while Fig. 18 con- 



FiG. 15. Mean of Wind Observations in " Lows " at 5000 Aleters above Sea 



Level, 1907-1912. 



tains similar information for low-pressure areas. The temperature- 

 altitude relation for a condition of neutral equilibrium in the atmos- 

 phere would be represented on one of these charts by a line drawn 

 at an angle of 45° to the axes. Such a gradient is more nearly ap- 

 proached by average conditions in the high-pressure areas of the 

 summer months than elsewhere, but the height to which it extends 

 does not often exceed 1,500 meters in these latitudes. 



Other convective systems than the planetary are in independent 



