1909.] BY MEANS OF KITES AND BALLOONS. 27 



are respectively characterized by more and less rapidly moving 

 storms. The effect of rapid motion upon a storm should be in 

 general to intensify it, for, the more rapidly it moves, the greater 

 the quantity of moist surface air that will be drawn up into it, and 

 consequently the greater the amount of latent heat liberated because 

 of the moisture condensation. 



The conclusion is that, for a given location and season, the depth 

 of a storm should indicate something of its rate of movement and 

 consequently of its intensity. This is in accord with the experience 

 at Mt. Weather. 



It is said that American storms are more intense than those of 

 Europe. If this be true, it is directly because of their more rapid 

 motion and indirectly because of their greater depth. 



Summer storms are less intense than those of winter. They are 

 not only deeper but move less rapidly. 



Cyclonic storm paths are, in general, found to pass through the 

 regions of greater surface humidity. They seldom cross the arid 

 or dry mountain regions, but travel along the great river basins, 

 over the Great Lakes or along the gulf and ocean coasts. 



So far the mean temperature change with altitude has been con- 

 sidered in two strata of the atmosphere: the lower, moist or storm 

 stratum extending from sea level up to 4,000 or 5,000 meters, and 

 the stratum above extending thence to 10,000 or 12,000 meters above 

 sea level. In the first the mean temperature gradient is about .5 

 degree Centigrade per 100 meters, in the second about .7 degree 

 Centigrade per 100 meters. The mean temperature at the top of 

 the first stratum is about — 10 degrees Centigrade, at the top of 

 the second about — 65 degrees Centigrade. 



Above these strata still a third distinct stratum has been explored 

 to an altitude of 25,000 meters above sea level. The striking pecu- 

 liarity of this stratum is that in it the temperature increases from 

 its base upward as far as it has been sounded. Its temperature 

 gradient is small but negative. It was at first called the isothermal 

 layer because the temperature seemed to change but little with 

 altitude. Later observations, however, show a decided negative 

 gradient or inversion of temperature and in consequence it is often 

 called the upper or permanent inversion, the adjective being neces- 



