Nov., 1921 THUNDERSTORMS 31 



may be established in one of three ways, as above pointed out. 

 Now, inasmuch as the passage of a cumulus cloud overhead, 

 however large, so long as rain does not fall from it, does not 

 materially disturb the surface winds, in other words, does not 

 bring on any of the familiar gusts and other thunderstorm 

 phenomena, we must infer that in some way the rain is an 

 important factor both in starting and maintaining the winds 

 we have just noted. On the other hand we cannot assume 

 that the rain is the whole cause of these winds for they do not 

 accompany other and ordinary showers, however heavy the 

 rainfall. 



The "rain-gush" or heavy downpour after a heavy clap 

 of thunder has often been misunderstood and has been made 

 to serve as a proof of the claims of the so-called "rain-makers." 

 The fact is the rain is the cause of the thunder or lightning, 

 and not the thunder the cause of the heavy rain. 



Then there is the lightning in its various forms, the "streak" 

 lightning, the so-called "rocker" lightning, the "ball" light- 

 ning, the "sheet" lightning, the "beaded" (?) lightning, the 

 "return" lightning, and some people say the "dark" lightning, 

 and so on. To discuss all these would carry us far beyond our 

 limit. Then there is the question of the temperature along the 

 path of a lightning discharge, how does the lightning render the 

 atmosphere through which it passes luminous, etc. Perhaps no 

 one knows the answer to these questions but it is very certain 

 that the temperature along the path of the lightning discharge 

 is very high from the fact that it sets fire to many objects, such 

 as buildings, that fall within its path. Just how the lightning 

 discharge renders its path through the atmosphere luminous is 

 not definitely known. Of course it does make the air along its 

 path very hot but no one so far as I know has ever succeeded 

 by any ordinary means in rendering oxygen or nitrogen luminous 

 by heating. It must be therefore, that the luminosity?- is due to 

 something besides high temperature, probably, according to 

 Prof. Humphreys, to "internal atomic disturbances induced by 

 the swiftly moving electrons of the discharge." The spectrum 

 reveals to us the interesting fact that lightning flashes are of 

 two colors, white and pink or rose. The rose-colored flashes, 

 when examined in the spectroscope, show several lines due to 

 hydrogen, which of course are due to the decomposition of 

 some of the water along the lightning path. The duration of 



