Improvements in Science. 121 



heterogeneous circle presents, under the relations of elec- 

 tric conductibility, to the difference of chemical re-action 

 which accomj^anies the passage of the currents.* 



3. Employment of electricity in dissolving calculi. — M. Bonnet, 

 Surgeon of the Hotel Dieu, at Lyons, proposes to dissolve 

 stones in the bladder, by injecting a solution of nitrate of 

 potash into the bladder, "and then introducing electrical 

 conductors on each side of the calculus ; the electrical in- 

 fluence being exerted, will evolve nitric acid on one side, 

 and potash on the other. So that whatever be the compo- 

 sition of the calculus, if soluble in an acid or alkali, it must 

 be acted on. When the calculus consists of plates, as in 

 urate of ammonia and in triple phosphates, or if it is porous 

 as in ammoniaco-magnesian phosphates, he found, that it 

 was softened, and that its layers readily separated. A great 

 objection to this ingenious method is its extreme tardiness. 

 Oxalate of lime acted on by a pile of 100 pairs of 1\ inch 

 scpiare plates was not attacked in the course of a night ; the 

 others were partially destroyed;-f- 



A. Electricity developed by the friction of metals. — Beccmerel 

 discovered, that by rubbing one metal against another, 

 placed at the two extremities of a galvanometer, an electric 

 current is produced, in which, one of the metals exposed to 

 friction is positive, and the other negative. He also 

 shewed, that in causing some metallic dust to slide over 

 the surface of a metal, of the same, or of a different nature, 

 opposite electric tensions were produced in the metal, and 

 in the dust. 



M. De la Rive has prosecuted the subject, and has found, 

 that the slightest friction with the finger, or with any sub- 

 stance, is sufficient to determine on a metallic surface a 

 tension often remarkable. The simplest mode of perform- 

 ing the experiment, is to bring in contact with the plate 

 of the condenser, pieces of metal of different kinds, held by 

 means of isolating handles, and then to rub gently the sur- 

 face of these metals with the finger, which ought to be very 

 dry. Employing as agents for friction, the finger, ivory, 

 horn, cork, and other species of wood, he found, that the 

 following metals acrmired by friction negative electricity : 



• Bibliotheqne CJniverselle, February, 19:>.'>. 

 t Ibid. April, 1835,391. 



