Thirty-first Annual Meeting 205 
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. Humpbreys, 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 
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