1823.] Royal Society. 393 



long, giving a total surface of 200 square feet. These plates 

 are wrapped or coiled round a common centre, and are prevented 

 from contact with each other by the interposition of three cords 

 of hair line, and also of notched slips of wood placed at intervals. 

 Two conductors of copper wire, nearly three-fourths of an inch 

 in diameter, are attached, one to the zinc, and the other to the 

 copper plate. In order that so large a mass may be readily 

 employed for experiment, the apparatus is suspended by means 

 of pulleys and a counterpoise, and so let down into a tub of acid, 

 or, when not in use, into one of water. It requires 55 gallons of 

 fluid. 



This instrument exhibits very powerful magnetic effects: 

 when the contact was made, a change in the direction of com- 

 pass needles was produced, at the distance of five feet ; steel 

 bars enclosed in cylinders of glass, with a spiral of wire round 

 them, were rendered magnetic, and several were suspended 

 together ; when the contact was broken, the bars fell, but one 

 of them was immediately taken up again on restoring the contact, 

 though it weighed above 270 grains. The electric intensity of 

 the apparatus is very slight ; it has not any decomposing action, 

 and will not make a spark with charcoal, nor will it deflagrate 

 the metals. 



A paper was also read, On the Condensation of several Gases 

 into Liquids. By M. Faraday, Chemical Assistant in the Royal 

 Institution. (Communicated by the President.) 



In this paper, Mr. Faraday described the results obtained by 

 the application of the mode of condensation by which he had 

 succeeded in liquefying chlorine, and Sir H. Davy muriatic acid 

 gas, to several other aeriform bodies. 



A portion of sulphuric acid being heated with mercury at one 

 end of a sealed glass tube, while the other was kept cool by 

 moistened bibulous paper, the sulphurous acid gas, which was 

 evolved, condensed into a liquid in the cool end : the same result 

 was obtained by forcing the dry gas into an exhausted tube with 

 a condensing syringe, until its pressure became equal to three 

 or four atmospheres. When the sealed tube was broken, the 

 liquid expanded into pure sulphurous acid gas. The refractive 

 power of liquid sulphurous acid is nearly that of water ; the pres- 

 sure exerted by its vapour in the tube was determined, by means 

 of a mercurial guage, to be equal to two atmospheres. Liquid 

 sulphuretted hydrogen was produced in the following manner : 

 The small and closed leg of a bent tube was filled with muriatic 

 acid ; a piece of platinum foil, crumpled up, was next intro- 

 duced ; and then some fragments of sulphuret of iron; the pla- 

 tinum foil being interposed in order to prevent the two substances 

 from contact until the tube was sealed, which operation would 

 otherwise have been rendered ineffectual by the pressure of the 

 evolved gas. When this had been done, the acid was made to 



