22 WILLIAM H. ALEXANDER Vol. XXII, No. 1 



We explain, for example, the origin, the progress and the 

 ending of a thunderstorm when we classify the phenomena 

 presented by it with other more familiar phenomena of vapor- 

 ization and condensation. But primitive man explained the 

 same thing, to his own satisfaction at least, when he classified 

 it along with the well-known phenomena of human volition by 

 constructing a theory of a great black dragon pierced by the 

 unerring arrows of an heavenly archer. As late as 1600, a 

 German writer would illustrate a thunderstorm destroying a 

 crop of corn by the picture of a dragon devouring the produce 

 of the field with his flaming tongue and iron teeth. But we 

 of today no longer regard the thunderstorm as an object of 

 terror or as an unfathomable mystery, but rather as a natural 

 phenomenon of great economic and scientific interest, one in 

 every way worthy of our best and most serious consideration. 



The physics and physical features of the thunderstorm are, 

 we believe, fairly well understood. These have been ably and 

 fully discussed by Professor Humphreys of the U. S. Weather 

 Bureau, whose teaching we follow very closely in this discussion. 

 If the thunderstorm produced only lightning and thunder, it 

 would be of only relative importance, but it may bring along 

 a whole series of redoubtable phenomena, thus presenting 

 problems of real practical importance — problems the magni- 

 tude and importance of which are not always fully appreciated. 



2. Definition 



And now, first of all, let us ask and answ^er, if we can, this 

 question: ''What is a thunderstorm?" Ordinarily, for example, 

 we think of a w^indstorm as a storm characterized by high and 

 perhaps destructive winds; of a hailstorm as one characterized 

 by the production of hail; of a snowstorm as one that produces 

 snow; of a dust storm as one characterized by a great quantity 

 of flying dust; and so, quite properly, we think of a thunder- 

 storm as a storm characterized by thmider and lightning. This 

 may not, I grant you, serve as a satisfactory definition, but it 

 will, perhaps, be a sufficient answer for the time being to the 

 question asked. 



It is not necessary in this presence, perhaps, to point out 

 that the "snow," the "wind," the "hail," and the "dust," 

 are in no sense the cause of the storm to which they give name. 



