698 Transactions of the American Institute. 



The universal diffusion of electricity, whether considered as fluid or 

 force, is conceded by philosophers. The marvelous properties mani 

 fested in its ready combination with heat, magnetism and light, its 

 rapid transmission through the most opaque and solid substances, 

 which it permeates (the earth for instance), with little or no obstruc- 

 tion, its velocity being far greater than that of light, the inexhaustible 

 supply evinced by the readiness with which it may be evoked from 

 the surrounding atmosphere, its tendency to equalization, when dis- 

 turbed, all lead to the conjecture that this may be the mysterious 

 element which the Almighty has provided, pure " effluence of bright 

 essence increate," to fill all the spaces of the universe unoccupied by 

 the solidity and compound masses of the planetary worlds, and which 

 has hitherto passed under the name of ether. No such thing as sheer 

 vacancy can be admitted to exist. Natura vacuum abhorret. Encke 

 has ascertained that there is a resisting medium in the interplanetary 

 spaces by the fact that his comet, which revolves round the sun in 

 1,207 days, has a regularly accelerated motion, by which the period 

 of each revolution is shortened by about six hours. These considera- 

 tions indicate the redundant sources from which the electricity of the 

 clouds is derived. The manner in which it is accumulated in the 

 thunder cloud may be understood by considering the causes which are 

 assigned for atmospheric electricity. " Some have ascribed it to 

 friction of the air against the ground, some to the vegetation of 

 plants or to the evaporation of water. Some, again, have compared 

 the earth to a vast voltaic pile, and others to a therm ometrical 

 apparatus." Many of these causes may, in fact, concur in producing 

 the phenomena. Volta first showed that evaporation produced 

 electricity. {Gemot 1 s Physics.) The atmosphere always contains free 

 electricity, sometimes positive", sometimes negative ; but alwaj^s positive 

 when the sky is cloudless ; and its intensity is greatest in the highest 

 and most isolated places. The positive electricity of fine weather is 

 much stronger in winter than in summer. The electricity of the 

 ground has been ascertained by Peltier to be always positive, but in 

 different degrees, according to the temperature of the atmosphere. 

 But when the sky is clouded, the electricity of the atmosphere is not 

 always positive ; it often happens that it changes during the day from 

 its positive to negative, or vice versa, owing to the passage of an 

 electrified cloud. 



The formation of positively electrified clouds is usually ascribed .to 

 the vapors which are disengaged from the ground and condense in 

 the higher regions. This is but one of several co-operative causes, 



