GASES PASS WHEN RESISTED BY THE FORCE OF MANY ATMOSPHERES. 51 



a resort- to such an energetic but unwieldy apparatus. A straight tube was, therefore, 

 taken, about three sevenths of an inch in bore (Jig. 21), and a rim turned on it at a a; 

 at the closed extremity the platina wires, b c, entered, a gauge tube, d d, was dropped in 

 between them, water was then poured in to the height, e e, and, lastly, a tube,/ con- 

 taining the appropriate chemical test, was inserted, its bottom resting on the top of the 

 gauge tube. Nothing then remained but to tie on the India-rubber, with its silken sup- 

 port, and bv the voltaic batterv to proceed to condense. In this instrument, the test fluid 

 was never out of sight, nor did the volume of the gas suffer any inconvenient change; 

 the gauge, too. was well located for observation, and a given condensation could be pro- 

 duced in less time, and by a less amount of electricity, than with the siphon tube ; for 

 the space contained between a a and e e was less in volume. As an auxiliary arrange- 

 ment, a glass tube, a a a a (Jig. 22), one inch in diameter and ten long, with a support, b, 

 was taken, and its mouth ground true, so that a piece of plate glass, e c, would close it when 

 placed over it ; this tube served in many cases as a gas generator, and also as a receiver 

 for the tube ( fig. 22), which was dropped into it It is to be observed, that in the ar- 

 rangement here adopted, the gaseous matter evolved from water mingles with the atmo- 

 spheric air in the upper part around the tube,/ and, therefore, the passage of the gases 

 tried does not take place into atmospheric air, but into a mixture of oxygen, hydrogen, 

 and nitrogen gases. 



160. The tube /"being filled with lime-water, and a pressure amounting to ten atmo- 

 spheres being produced in the vessel, it was exposed to an atmosphere of carbonic acid, 

 generated in the tube a a a a, jig. 22, procured by dropping a few pieces of marble into 

 the tube, and pouring thereon dilute muriatic acid. When the vessel was full, the 

 plate e c was laid upon it, and any surplus gas generated escaped by lifting it up. In 

 the course of a few minutes, the upper part of the tube containing lime-water began to 

 look milky, and in an hour, a cloud of particles of carbonate of lime had fallen to the 

 bottom. 



161. Asrain, having filled the tube/ with a solution of acetate of lead, and produced 

 a pressure amounting to twelve atmospheres, it was exposed to sulphuretted hydrogen, 

 generated in the vessel, Jig. 22, from protosulphuret of iron and dilute sulphuric acid. 

 In a very short time, the black sulphuret of lead appeared, giving tokens of the rapid 

 passage of this gas through the barrier. A comparative experiment was made, in order 

 to discover whether the transmission took place more slowly than when it was not re- 

 sisted by such a severe pressure. It appeared, however, so far as the experiment could 

 be tried under similar circumstances, as regards the thickness of the barrier, &c., that 

 sulphuretted hydrogen went through the barrier against a pressure of three hundred and 

 sixty inches of mercury, as readily as if no such force were exerted against it. 



162. As numerous experiments, which had been tried on various gases, had hitherto 

 failed to indicate any obstacle to their passage, it became necessary to know whether, 

 at the extremes! pressures that could be commanded, they would pass through a bar- 

 rier. To accomplish this, I took a strong and narrow tube, and, having turned a rim 

 at one end and sealed fine platina wires in the other, I filled it with distilled water, and 

 enclosed in it a narrow capillary tube, the gaseous contents of which were small. As 



