Polytechnic Association. 701 



facilitated by raising the temperature of the water, and must be indefi- 

 nitely facilitated when the water is vaporized and changed into steam. 

 It is reasonably inferred that the strong currents of electricity passing 

 through a summer cloud of the cmnulus order must be productive of 

 immense decompositions of the masses of vapor and evolution of those 

 gases. We have before spoken of heat and moisture as among the 

 most prolific sources of electricity. Every addition of caloric to 

 water evolves it, evaporation carries off immense quantities of elec- 

 tricity into the air, and the decomposition of the particles of water in 

 the form of vapor eliminates unappreciable quantities. It is not an 

 unreasonable supposition that, in the varied position of the surfaces 

 of the cumulus with respect to the sun's rays, the heat is often so 

 intensified as to raise the vapor into steam. Electricity is exhibited 

 in two forms : one produced by friction and manifested by the elec- 

 tric spark, to which form the lightning belongs ; the other passes in 

 silent currents, and is manifested chiefly in chemical action. This is 

 said to be weak in tension, but great in quantity ; the former to be 

 small in quantity, but of powerful intensity. It is with this distinc- 

 tion in hand, that we are to weigh the statement that Faraday showed 

 how a drop of water contains more electricity than is discharged in the 

 most violent flash of lightning. {Porter's Chemistry, 104.) And if 

 our wonder should shake our faith in the statement, we may find some 

 relief in the acknowledgment of Faraday himself at a meeting of the 

 British Association for the Advancement of Science: "There was a 

 time," he said, " when I thought I knew something about the matter ; 

 but the longer I live and the more carefully I study the subject, the 

 more convinced I am of my total ignorance of the nature of elec- 

 tricity." 



It is certain, however, that from evaporation rising from the earth's 

 surface, from the processes of vegetation, and from the action of every- 

 thing that lives or moves upon the surface, currents of electricity are 

 constantly ascending, filling the atmosphere and accumulating in the 

 clouds. These operating upon the expanded and heated vapors of 

 watery particles, those currents, as we believe, first decompose the 

 water, evolving the constituent gases, and surcharging, by their redun- 

 dant quantity, some prominent mass of cloud, or, excited by a collision, 

 the electricity is discharged in its intense form of the electric spark- 

 lightning, firing and exploding the gases with a concussion which 

 causes the earth and air to tremble. For these gases, when brought 

 together, we repeat, may continue in a mixed state without combin- 

 ing chemically, but, subjected to aflame or a spark of electricity, they 



