SPONTANEOUS COMBUSTION. 317 



of zinc op. A brass tube a b c, is fitted at a into 

 the neck of the globe CD, and through this tube, 

 which is furnished with a stop-cock d, the gas can 

 escape at the small aperture c. A brass pin cf^ 

 carrying a brass box P, is made to slide through 

 a hole h, so that the brass box P, in which the 

 spongy platinum is placed, can be set at any 

 required distance from the aperture c. If sul- 

 phuric acid, diluted with an equal quantity of 

 water, is now poured into the vessel AB by its 

 mouth at S, now closed with a stopper, the fluid 

 will descend through the tube m n o p, and if the 

 cock d is shut, it will compress the air contained 

 in CD. The dilute acid thus introduced into CD 

 will act upon the ring of zincoj^, and generate 

 hydrogen gas, which, after the atmospheric air in 

 CD is let off, will gradually fill the vessel CD, the 

 diluted acid being forced up the tube o p m n, 

 into the glass globe AB. The ring of zinc o p 

 floats on a piece of cork, so that when CD is full 

 of hydrogen, the diluted acid does not touch the 

 zinc, and consequently is prevented from produc- 

 ing any more gas. The instant, however, that 

 any gas is let off at c, the pressure of the fluid 

 in the globe AB, and tvibemnop, overcomes 

 the elasticity of the remaining gas in CD, and 

 forces the diluted acid up to the zinc o p, so as to 

 enable it to produce more gas to supply what has 

 been used. 



The lamp being supplied with hydrogen in the 

 manner now described, it is used in the following 

 manner. The spongy platinum in P being brought 

 near c, the cock d is turned, and the gas is thrown 

 upon the platinum. An intense heat is imme- 

 diately produced, the platinum becomes red-hot, 

 and the hydrogen inflames. A taper is then 



