PROGRESS IN ELECTRICITY 



stand and that set on a plate of glass, or on the brim 

 of a drinking-glass, previously chafed, or otherwise 

 warmed), I have found, upon trial, that the same 

 thing happened to all bodies without exception, wheth- 

 er solid or fluid, and that for that purpose 'twas suffi- 

 cient to set them on a glass stand slightly warmed, 

 or only dried, and then by bringing the tube near them 

 they immediately became electrical. I made this ex- 

 periment with ice, with a lighted wood-coal, and with 

 everything that came into my mind ; and I constantly 

 remarked that such bodies of themselves as were least 

 electrical had the greatest degree of electricity com- 

 municated to them at the approval of the glass 

 tube." 



His next important discovery was that colors had 

 nothing to do with the conduction of electricity. "Mr. 

 Gray says, towards the end of one of his letters," he 

 writes, "that bodies attract more or less according to 

 their colors. This led me to make several very sin- 

 gular experiments. I took nine silk ribbons of equal 

 size, one white, one black, and the other seven of the 

 seven primitive colors, and having hung them all in 

 order in the same line, and then bringing the tube near 

 them, the black one was first attracted, the white one 

 next, and others in order successively to the red one, 

 which was attracted least, and the last of them all. I 

 afterwards cut out nine square pieces of gauze of the 

 same colors with the ribbons, and having put them one 

 after another on a hoop of wood, with leaf -gold under 

 them, the leaf -gold was attracted through all the col- 

 ored pieces of gauze, but not through the white or 

 black. This inclined me first to think that colors con- 



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