512 ELECTRICITY. 



The most suitable substances upon which to make ex- 

 periments on the fusibility of metals with small machines, 

 are gold, silver or brass leaf, or even tin foil cut into 

 very slender strips, or a very fine flattened steel wire, 

 used by watchmakers, called watch pendulum wire. By 

 means of either of these, fusion may often be produced 

 by a common machine and by a single Leyden jar. 



If eat evolved by lightning. The power of those im- 

 mense charges of electricity which descend from the 

 clouds, to inflame combustibles and fuse metals is a mat- 

 ter of common observation. Small pieces of iron, i. e. 

 too small for the whole quantity of the fluid to pass them, 

 are melted. It must be borne constantly in mind that 

 this heat is developed only when the conducting sub- 

 stances are not sufficient to convey off the electricity 

 freely to the ground. There is no evidence that a com- 

 mon lightning lod, down which the electricity passes 

 freely, becomes in the least degree warmed by its power. 

 The points, however, at the top, are frequently fused. 



A house was once struck with lightning, and a pair of 

 tongs which were standing up against the fireplace were 

 thrown down. A person standing in the room, who for- 

 tunately was not injured by the shock, almost immedi- 

 ately took them up, and on examining them was surpris- 

 ed to find, that although the iron was cold as usual to 

 the touch, yet at the two extremities of the tongs, ap- 

 parently at the places where the fluid entered, and left, 

 there were two small melted spots. The iron was very 

 distinctly and evidently fused and the individual was 

 much surprised that the heat should be so great as to 

 melt the iron in any part, and yet not to heat it through- 

 out so as to render its warmth sensible to the hand. But 

 the fact is that the electric fluid is not, as many suppose, 

 hot itself. It produces heat, when passing through the 

 air. It will do this when coming out of ice, as well as 

 when coming from a metal ; and in the case above de- 

 scribed, the electric fluid, developed heat in coming 

 through the air to the tongs, and in passing through the 

 air from the tongs, in sufficient quantities to fuse the me- 

 tal at the points where it entered, and where it left. 



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