420 



ELECTRICITY. 



lU^qr. her becomes smooth, the electricity will again become 

 ""^M"** negative. " Thus," says Mr Canton. may tin po*i- 

 tive and negative powers of electricity U- produced 

 at pleasure by altering the surfaces of the tube and 

 rubber, according a the one or tlir other is roost af- 

 fected by the friction between them ; lor if the polish 

 be taken off one half of the tube, the different po\\ t -i> 

 may be excited w ith the same ruliln-r ;it a single stroke : 

 And the rubber is found to move much easier over 

 the rough than over the polished part." Phil. Tntns. 

 1754, vol. xlviii. p. 780, &c. Mr Canton afterward* 

 found that the smoothest glass will acquire a ne- 

 gative electricity by being drawn over the back of a 

 cat. 



Having observed that the friction of mercury, in- 

 cluded in a glass tube, not only produced electrical light, 

 but aNo electrified the glass on the outside, Mr ( 'union 

 plunged a piece of dry glass in a basin of mercury, and 

 found that by taking it out, the mercury was ele< 

 negatively and the glass positively, and to a consiii. 

 degree. He likewise found that amber, sealing-wax, 

 and Iceland crystal, were all electrified positively when 

 taken out of mercury. From these experiments Mr 

 Canton was led to the discovery of an amalgam of mer- 

 cury and tin, which he always found highly efficacious 

 in the excitation of glass. The subject of electric at- 

 mospheres was also illustrated by some fine experi- 

 ments of Mr Canton. These experiments exhibit a cu- 

 rious variety of attractions and repulsions of electri- 

 fied bodies under different circumstances, and led to 

 the establishment of the general fact, that bodies im- 

 merged in electric atmospheres always become posses- 

 sed of the electricity contrary to that of the body into 

 whose atmosphere they are plunged. 



Discoveries Contemporary with Mr Canton, was Giambattista 

 of Beccaria. Beccaria, who has laid the science of electricity under 

 iv i la?' ff" 6 ** obligations, and has published his discoveries in 

 a work entitled, Dell' elettricimw artificialc e iiatiirale, 

 which appeared at Turin in 1753, and was translated 

 into English in 1776. Having no knowledge of the 

 experiments of Mr Canton, Beccaria made the same dis- 

 covery respecting the communication of electricity to 

 the air. He demonstrates that the air which is adja- 

 cent to an electrified body acquires gradually the .same 

 electricity ; that the electricity of the body is counter- 

 acted and diminished by this electricity of the air ; and 

 that the air parts with its electricity very slowly. He 

 also found that there was a mutual repulsion between 

 the particles of the air and electric matter, and that a 

 temporary vacuum is formed by the electric fluid in 

 passing through any portion of air. His experiments 

 on water are equally interesting and important. He 

 has shewn that water is a very imperfect conductor of 

 the electric fluid ; that it conducts electricity according 

 to its quantity ; and that a small quantity of water 

 makes a great resistance to the electric fluid. Small 

 tubes of water, for example, when forming port of the 

 electric circuit, refused to transmit a shock, while it 

 was readily conveyed by tubes of a larger bore. He 

 f\en made the electric spark visible in water, by insert- 

 ing wires nearly meeting in tubes filled with water, and 

 discharging shocks through them. The electric spark 

 appeared as if no water had been present; but the tubes, 

 though often 8 or 10 lines thick, were generally bro- 

 ken to pieces with tremendous force. The same phi- 

 losopher discovered also that metals were not perfect 

 conductors; and by suspending a wire of 500 Paris li-et 

 in length, and using a pendulum vibrating half seconds, 

 he thought that he could detenmns the rate at which 



Died 1781. 



the electric fluid advanced. Light bodies, for exam- 

 ple, placed at one end of the wire, did not mote till one 

 vibration after a charged phial hail l>. en applied at the 

 other extremity. When u hempen cord was used, five 

 or six vibration* clap.-cd, and only three or four when 

 II wetted. 



These experiments of Si^iior Heccaria, valuable as 

 they are, were greatly surpassed by those which he 

 made on the electrical phenomena of the atmosphere. 

 An account of these experiments however, would re- 

 quire us to enter into u minuteness of detail which is 

 inconsistent with a general hi*tory of electricity. They 

 will IM- given with more propriety in another part of 

 the article. 



About this time, the death of Professor llichman of 

 St Petersburg, while employed in bringing electricity 

 from the heavens, created a great sensation in the scien- 

 tific world, and is well entitled to be particularly men- 

 tioned in a history of electricity. This eminent individual 

 was engaged in a work on the electricity of the atmo- 

 sphere, and was therefore extremely desirous of obcr- 

 ving the clcdric.il state of the uir during thunder storms. 

 On the (ith of August 175:. he had prepared his appara- 

 tus for observation. From a metallic rod passing through 

 a perforated bottle, and fixed upon the roof of his house. 

 there passed a chain surrounded with electrics. The 

 other end of this chain was fixed to another metallic 

 rod placed in a glass vessel, and to this second rod was 

 attached a linen thread, which marked, by its elevation 

 on a quadrant, the intensity of the electricity of the 

 rod. 



While Professor Richman was attending an ordinary 

 meeting of the Academy of Sciences in the forenoon, 

 his attention was excited by the sound of distant thun- 

 der. He immediately set oft" for his own house to ob- 

 serve the electrical state of the air, and took with him 

 his engraver Sokolow, that he might be enabled to give 

 a better representation of any phenomena tliat should 

 present themselves. Richman remarked, that the thread 

 pointed to four degrees on his quadrant ; and while he 

 was describing to his friend the dangerous consequen- 

 ces that might ensue if the thread rose to 45, a dread- 

 ful clap of thunder alarmed all the inhabitants of St 

 Petersburg. Richman inclined his head to the gnomon 

 to see the degree of electricity which was indicated, and 

 when he was in that bent posture, with his head about 

 a foot distant from the rod, a large globe o!' white and 

 bluish fire, about the size of Mr Undnr'l fist, flashed 

 from the rod to his head, with a report as loud as that 

 of a pistol. The Professor fell back upon a chest be- 

 hind him, and instantly expired. Sokolow was stupi- 

 fied and benumbed by a sort of steam or vapour, and 

 was struck by several fragments of the red-hot wires; 

 and the moment he recovered, he ran out of the IIOIIM-, 

 acquainting every person whom he saw with the accident. 

 In the mean time, Mrs Richman, who heard the stroke of 

 thunder, hastened to the chamber, and found her husband 

 without any appearance of life, in the .Attitude of sitting 

 upon the chest, and leaning against the wall. The 



was filled with a sulphureous vapour ; an 

 lish clock wa> stopped in an adjoining room, the 

 were thrown from the fire-place, and the door-p.ots of 

 the house were rent asunder. As soon as m. -i;i. d .<-- 

 sistance was obtained, a vein of the Pi body 



was opened, but no blood flowed, and every attempt to 

 restore life by violent chafing, and other mean*, were 

 wholly fruitless. When the Ixidy w;is turned upside 

 down, a small quantity of blood fell from the mouth 

 during the rubbing, and on the forehead appeared a 



Iliuory. 



Hi.- experi- 

 ments OH 

 lightning. 



Death of 

 Professor 

 Richman by 

 lightning. 



