946 Dr. J. W. Draper's Remarks on the 



atmospheres, it was exposed to sulphuretted hydrogen. In a 

 very short time the black sulphuret of lead appeared, giving 

 tokens of the rapid passage of the gas. A comparative ex- 

 periment was made, in order to discover whether the trans- 

 mission took place more slowly than when it was resisted by 

 such a severe pressure. It appeared, however, so far as the 

 experiment could be tried under similar circumstances, as re- 

 gards the thickness of the barrier, &c., that sulphuretted hy- 

 drogen gas went through a barrier against a pressure of 

 three hundred and sixty inches of mercury, to mix with another 

 gas, as readily as if no force were exerted against it. 



As numerous experiments, which had been tried on various 

 gases, had failed to indicate any obstacle to their passage, it be- 

 came necessary to know whether at the most extreme pressures 

 that could be commanded they would pass through a barrier. 

 To accomplish this, I took a strong and narrow tube, and 

 having turned a rim at one end, and sealed five platina wires 

 into the other, \Jilled it with distilled water, and inclosed a 

 narrow capillary tube in it, the gaseous contents of which 

 were small. As a test, in the upper part of the arrangement, 

 and in lieu of the tube f, I placed a slip of paper which had 

 been alternately soaked in acetate of lead and carbonate of 

 soda; the India-rubber was fortified by a piece of very strong 

 silk, which was carefully tied on; there was not therefore any 

 gaseous matter present, except the small quantity of air in 

 the gauge tube. The condensation went on with great ra- 

 pidity, a mixture of oxygen and hydrogen gradually accumu- 

 lating in the top of the vessel, bulging out the India-rubber 

 and silk barrier, until it was almost hemispherical. It was 

 my intention to try a pressure of twenty-five atmospheres ; 

 and when that was supposed to be reached, the instrument 

 was immersed in sulphuretted hydrogen. Very soon the test 

 paper became of a tawny yellow, and finally it was quite 

 black ; the pressure when the experiment was over was de- 

 termined to be twenty-four and a quarter atmospheres. 



At a temperature of 48° Fahr., and pressure 29*74< bar. 

 sulphuretted hydrogen gas passes through a barrier into a 

 mixture of oxygen and hydrogen, though it may be resisted 

 by a pressure of twenty-four arid a quarter atmospheres, or 

 nearly seven hundred and thirty inches of mercury. Like sul- 

 phurous acid, it will become diffused into an atmosphere beyond 

 it under a greater pressure than that which is sufficient to con- 

 dense it into a liquid. 



These results would appear, at first sight, entirely opposed 

 to the hypothesis of gaseous action, and important enough to 

 cast doubts upon its correctness, if not entirely to destroy it. 



