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THE POPULAR SCIENCE MONTHLY. 



the air. Bring the tube near the leaf: it plunges toward the tube, 

 stops suddenly, and then flies away. You may chase it round the 

 room for hours without permitting it to reach the ground. The leaf 

 is first acted upon inductively by the tube. It is powerfully attracted 

 for a moment, and rushes toward the tube. But from its thin ed^es 

 and corners the negative electricity streams forth, leaving the leaf 

 positively electrified. Repulsion then sets in, because tube and leaf 

 are electrified alike. The retreat of the tassel in the last experiment 

 is due to a similar cause. 



There is also a discharge of positive electricity into the air from 

 the more distant portions of the gold-leaf, to which that electricity 

 is repelled. Both discharges are accompanied by an electric wind. 

 It is possible to give the gold-leaf a shape which shall enable it to 

 float securely in the air by the reaction of the two winds issuing from 

 its opposite ends. This is Franklin's experiment of the Golden Fish. 

 It was first made with the charged conductor of the electrical machine. 



Fig. 22 



M. Srtsczek revived it in a more convenient form, using instead of the 

 conductor the knob of a charged Leyden-jar. You may walk round 

 a room with the jar in your hand; the "fish" will obediently follow 

 in the air an inch or two, or even three inches, from the knob. (S* i 

 A B, Fig. 22.) Even a hasty motion of the jar will not shake it 

 away. 



Well-pointed lightning-conductors, when acted on by a thunder- 

 cloud, behave in the same way. The opposite electricity streams out 

 from them against the cloud. 



Franklin saw this with great clearness, and illustrated it with 

 great ingenuity. The under-side of a thunder-cloud, when viewed 





