ELECTRICITY. 



107 



was enjoyed by resin, hair, glass, and some other substances. In fact, it soon 

 becams apparent that this property belonged in a greater or less degree to all 

 those substances which were then known to be capable of being rendered 

 electrical by friction, and which were denominated electrics. 



Grey now extended his inquiry to fluids and animal bodies. Having at that 

 time no other test of the electrical state of a body than its attraction for light 

 substances placed on a stand under it, the application of such a test to liquids 

 presented at first some difficulty. This was soon surmounted by the expe- 

 dient of blowing a soap-bubble from the bole of a tobacco-pipe. The bubble 

 was held suspended over some leaf metal, and on bringing the excited tube to 

 the small end of the pipe, the bubble immediately became electrical. 



It was in the prosecution of these experiments that he discovered that, when 

 the electrified tube was brought near to any part of a non-electric body, without 

 touching it, the part most remote from the tube became electrified. He thus 

 fell upon the fact which afterward led to the principle of INDUCTION. The 

 science, however, was not yet ripe for that great discovery, and Grey accord- 

 ingly continued to apply the principle of inductive electricity, without the most 

 remote suspicion of the rich mine whose treasures lay beneath his feet. 



In another series of experiments, Grey was also unfortunate in missing a 

 subsequent discovery on which he just touched. He found that certain electric 

 bodies were capable of becoming permanently excited without the previous 

 process of attrition. He took nineteen different substances, among which were 

 resin, gum-lac, shell-lac, sulphur, and pitch, and the remainder of which were 

 various compounds of these. The sulphur he melted in a glass vessel, the 

 others in a spherical iron ladle. When they became solid, and cooled, and 

 were removed from the moulds in which they were, in this manner, cast, he 

 found them to be electrified, and that, on preserving them from exposure to the 

 air, by wrapping them in paper or wool, this electrified state continued for an 

 indefinite time. In the case of sulphur, he found that not only the sulphur 

 was electrical, but also the glass from which it was removed. Had he carried 

 these inquiries further, and looked carefully into the circumstances of the at- 

 traction exhibited by the sulphur and the glass, he could not have failed in 

 discovering the existence of the two opposite electricities, and would probably 

 have also found the reason why the iron ladle did not exhibit electrical signs 

 as well as the glass. This, however, escaped him, and the honor of the dis- 

 covery was reserved for a contemporary philosopher. 



In his investigations respecting the power of liquids to receive electricity 

 from excited glass, Grey exhibited, in a manner which at that period appeared 

 striking, the attraction of the glass tube for liquids. We shall, however, pass 

 over these and some other experiments of less importance, since they did not 

 conduce to the development of any general principle. 



Contemporary with Grey was the celebrated Dufaye, who, though not im- 

 pelled by the same enthusiasm, nor exhibiting the same unwearied activity in 

 multiplying experiments, was endowed with mental powers of a much higher 

 order, and consequently was not slow to perceive some important consequences 

 flowing from the experiments of Grey, which had eluded the notice of that 

 philosopher. Dufaye, in the first place, extended the class of substances called 

 electrics showing that all substances whatever, except the metals and bodies 

 in the soft or liquid state, were capable of being electrified by friction with any 

 sort of cloth, and that, to secure the result, it was only necessary to warm the 

 body previously. He also showed that the property of receiving electricity 

 by contact with an excited electric was much more general than was supposed 

 by Grey, and that most substances exhibited that property in a greater or less 

 degree, when supported by glass well warmed and dried. Dufaye also showed 



