Nov., 1921 THUNDERSTORMS 23 



Nor, so far as known, have the lightning and thunder any 

 influence on the formation, progress and termination of the 

 thunder-storm, although they may and often do constitute 

 the most impressive, spectacular, and even tragic features of 

 the storm. For as Prof. Humphreys well says,^ "No matter 

 how impressive or how terrifying these phenomena may be, 

 they never are anything more than mere incidents to or products 

 of the peculiar storms they accompany. In short, they are 

 never in any sense either storm-originating or storm-controlling 

 factors." 



3. Source of the Lightning 



Since w^e cannot have a thunderstorm without thunder, 

 and cannot have thunder without lightning, it seems quite 

 essential to a proper understanding of these storms to get a 

 correct, scientific explanation of the source or cause of the 

 lightning. Oh, yes, we are fully aware of the danger just here — 

 namely, how easily and how quickly one may get beyond his 

 depth when talking about the origin of electricity. We must 

 admit, of course, that we know very little if anything for 

 certain at this point, but then we would like to appear to know 

 something about this interesting phase of our discussion. We 

 are deeply indebted to Dr. G. C. Simpson^ of the Indian 

 Meteorological Department for our best information or knowl- 

 edge on this point. Dr. Simpson, by numerous observations and 

 laboratory experim.ents found out a great many extremely 

 valuable things concerning the electricity brought down by the 

 raindrop and the snowflake, and at the same time, by means 

 of a number of well-devised experiments, determined the 

 electrical effects of each obvious process that takes place in 

 the thunderstorm. He found out, for example, that no elec- 

 trification resulted from freezing and thawing, air-friction, etc., 

 but that when he allowed drops of distilled water to fall through 

 a vertical blast of air of sufficient strength to produce some 

 spray, 



(1) That breaking of drops of water is accompanied b}^ the 



production of both positive and negative ions. 



(2) That three times as many negative ions as positive ions 



are released. 



"Now," as pointed out by Professor Humphreys-, "a 

 strong upward current of air is one of the most conspicuous 



