54 DESCRIPTION OF AN APPARATUS FOR 



terminates at the bottom in a stuffing-box, through which a copper rod slides 

 so as to reach above the level of the air-pump plate. The end of the rod sup- 

 ports a small horizontal platform of sheet brass, which receives four upright 

 screws. These, by pressure on brass bars extending from one to the other, 

 are competent to secure upon the platform a parallelepiped of charcoal. Upon 

 the air-pump plate a glass bell is supported, and so fitted to it, by grinding, as 

 to be air-tight. The otherwise open neck of the bell is also closed air-tight by 

 tying about it a caoutchouc bag, of which the lower part has been cut off, while 

 into the neck a stuffing-box has been secured air-tight. Through the last men- 

 tioned stuffing-box a second rod passes, terminating within the bell in a kind 

 of forceps, for holding an inverted cone of charcoal, (E.) 



The upper end of this sliding rod is so recurved as to enter some mercury 

 in a capsule, (F.) By these means and the elasticity of the caoutchouc bag, 

 this rod has, to the requisite extent, perfect freedom of motion. 



The lower rod descends into a capsule of mercury, (G,) being, in conse- 

 quence, capable of a vertical motion, without breaking contact with the mer- 

 cury. It is moved by the aid of a lever, (H,) connected with it by a stirrup 

 working upon pivots. 



Of course the capsules may be made to communicate severally with the 

 poles of one or more deflagrators. The substance to be deflagrated is placed 

 upon the charcoal forming the lower electrode, being afterwards covered by 

 the bell, as represented in the figure. By means of the valve-cocks and leaden 

 pipes a communication is made with a barometer gage; (see fifth volume of 

 this work ; ) also with an air-pump, and with a large self-regulating reservoir 

 of hydrogen. 



The air being removed by the pump, a portion of hydrogen is admitted, and 

 then withdrawn. This is repeated, and then the bell glass, after as complete 

 exhaustion as the performance of the pump will render practicable, is prepared 

 for the process of deflagration in vacuo. But, if preferred, evidently hydrogen 

 or any other gas may be introduced from any convenient source by a due com- 

 munication through flexible leaden pipes and valve-cocks. 



Having described the apparatus, I will give an account of some experiments, 

 made with its assistance, which, if they could have illuminated science as they 

 did my lecture room, would have immortalized the operator. But, alas, we may 

 be dazzled, and almost blinded by the light produced by the hydro-oxygen 



