50 GASES PASS WHEN RESISTED BY THE FORCE OF MANY ATMOSPHERES. 



to be absolutely essential to the transit of the electricity. Now it might be supposed 

 that, if some powerful force were brought to bear against and antagonize this, as where, 

 by a severe pressure, the oxygen and hydrogen are prevented from being evolved, one of 

 four things must happen: 1st. That the water would become a non-conductor. 2d. 

 That the vessel, no matter how strong it might be, would burst. 3d. That the current 

 would pass without any decomposition happening; or, lastly, that the current would 

 pass and gas be evolved, but as fast as evolved, it would be dissolved in the water. A 

 quantity of boiled water was hermetically sealed up in a glass tube, which it filled en- 

 tirely, except a small space occupied by a bubble of air, probably not more than one 

 fiftieth part of an inch in diameter. A pair of platinum wires had been fixed into the 

 tube so as to transmit the voltaic current. The current passing freely, as was indicated 

 by a galvanometer, decomposition of the water ensued; extremely minute bubbles making 

 their appearance^ the water absorbing the greatest part of them, its temperature rising 

 very much, so that the tube communicated a sensation of warmth when touched by the 

 finger. When the pressure was estimated to have risen to about fifty atmospheres, the 

 tube burst, and in an instant all the gas that had been imprisoned in the water made its 

 escape, throwing it into a violent effervescence. Hence we find, that when water is 

 enclosed hermetically in a vessel, and a galvanic current passes through it, decomposition 

 ensues, a portion of the gases making their appearance in a gaseous form, replacing the 

 small space occupied by the decomposed water, the whole of the remainder being ab- 

 sorbed by that fluid as fast as it is given off. When the pressure is high, it is probable 

 that the dimensions of the vessel become greater, and hence the little bubble of air ac- 

 cumulated exceeds in bulk the volume of decomposed water. It is also found that any 

 pressure up to forty or fifty atmospheres may be commanded in this way. 



158. Being thus furnished with a very convenient and very portable method of con- 

 densation, I proceeded to examine the force of passage of gaseous matter into atmo- 

 spheric air. Sulphurous acid passed instantaneously into atmospheric air, against a 

 pressure equivalent to two hundred and twenty inches of mercury, or seven atmospheres 

 and a third. Some experiments were made on the absorbing action of the sample of 

 India-rubber here used, which had been softened in ether for the purpose of procuring 

 it in thin sheets. Of the gas here spoken of, it was found to absorb sixteen times its 

 own volume. It is to be expected that, even had a much more powerful pressure been 

 applied, the gas would, nevertheless, have gone through. 



359. The curved form of the instrument described in (155) was found to present cer- 

 tain inconveniences when pressures upward of six or seven atmospheres were made use 

 of; the volume of air which, at the beginning of the experiment, occupied the greater 

 part of the extent of the shorter limb, had now collapsed much in its dimensions, and 

 owing to the unavoidable giving way of the India-rubber and its silk, had retreated out 

 of sight beneath it. It was not found convenient to lengthen this limb, for that entailed 



a corresponding increase in the dimensions of the battery, in order to produce a given 

 condensation in a given time ; an objection also applying, in a measure, to the apparatus 



even at lower pressures. Though I had the command of batteries, consisting of six 



hundred pairs of four-inch plates, I preferred a modification in the instrument itself, than 



