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LXXVI. On the Electric Properties of Metals, and the abso- 

 lute Positive and Negative Electric Powers of various Sub- 

 stances. Btj Mr. J. Tatum. 



To Mr. Tillocli. 



Sir, — Should you think the account of the followins; expe- 

 riments calculated to remove the erroneous but widely dissemi- 

 nated opinion of the non-electric properties of metals; and aho, 

 of the absolute positive and negative electric powers residing in 

 peculiar substances, they are very much at your service. 



To prove that metals possess all the electric properties with 

 which vitreous and resinous bodies are endowed, nothing but 

 friction is necessary, when their positive and negative properties 

 will be elicited, and to as great an extent as is produced by the 

 above bodies. 



Exp. 1. Let a plate of zinc (of about two inches diameter) 

 provided with an insulating handle rising, from its centre, be 

 quicklv drawn over a piece of silk, and on presenting it to an 

 electrometer, it will be found to produce strong signs of positive 



electricity. 



Exp. 2. But if a plate of silver of the same size be subject to 

 friction on silk, (or, what is better, on fur, for then I have had it 

 produce a spark which could be both heard and seen,) it will 

 produce signs of Ttegative electricity. 



From these experiments, we see that both positive and nega- 

 tive electricity are produced frcm metallic bodies, and by the 

 same means with which they are produced from vitreous and re- 

 sinous substances. 



That positive and negative electricity is not peculiar to any 

 particular body, but depends on the greater or less attraction 

 which the rubber possesses for the electric fluid, will, I think, be 

 evident from the following experiments. 



Exp. 3. If in the place of silk, on which the plate of zinc was 

 rubbed, we substitute ywr, the plate of zinc will now give signs 

 of negative electricity. 



Ex . 4. And if we draw white silk over black silk, we shall 

 find the white betray signs of positive electricity, and the black 

 negative electricity. 



"Exp. 5. i'ut if the same tvhite silk be drawn over fur, it will 

 now give signs of negative electricity. 



Exp.G. if yellow silk be drawn over the white silk, the yellow 

 will be neoalifelri electrified, and the white positively electrified. 



Exp. 1 . But if the yeiloiv be drawn over the black, the yellow 

 will now become positively electrified. 



From 



