12 



ing a Ley'den jar the electricity will break through 

 the glass (especially is it apt to do so if the glass 

 contains lead), and ruin the jar thereafter for ex- 

 perimental purposes. Likewise, sometimes, elec- 

 tricity, under such high potentials, in the upper, 

 rare atmosphere (in storm-clouds, for instance), will 

 break through the intervening denser air and dis- 

 charge itself into the ground or water this we call 

 a stroke of lightning. 



Franklin raised his kite into such charged clouds, 

 and their electricity came down the string and filled 

 his Leyden jar, proving the identity of the elec- 

 tricity of the atmosphere with that of the plate 

 machines ordinarily used to charge Leyden jars. 



What if Paulin's geomagnetifers could be made 

 to penetrate miles up into this reservoir of elec- 

 tricity and thus furnish an easy path for it to the 

 earth ? It is interesting to speculate upon the pos- 

 sibility of our being able to tap this great store- 

 house of stimulus to vegetation possibly even to 

 human development at will. 



If we ask whence the outer, rare layers of our 

 atmosphere get their electricity, we may come 

 nearest a correct answer by saying from the sun, 

 that great source of so many forms of energy. We 

 know that displays of the aurora borealis, and also 

 electric storms, which are so unwelcome to tele- 

 graphers, are most frequent during the prevalence 

 of sun-spots, and we know that these spots are due 

 to some great disturbance upon the sun. Whether 

 the electricity thus generated upon the sun is carried 

 to' our upper atmosphere by minute particles thrown 



