288 Dr. Henry’s Description of an Apparatus j or the 
of the oxygen gas, the water is raised by a syphon to a proper 
height within the receiver b, as appears in the drawing. 
The apparatus being thus disposed, the cock/ is connected 
by the chain h, with the prime conductor of an electrical 
machine ; and a rapid succession of sparks is made to pass 
betwee n the copper ball at the end of the wire g, and the 
orifice of the burner. The cocks q and r being now opened, 
the stream of gas is kindled ; and in order to prevent the 
flame from playing upon the wire, the jar n n is moved a little 
nearer to the cistern a, which brings the point of the burner 
into the axis of the receiver. At the same time, by opening 
the cock x, water flows into the jar n n, and finds its way into 
the receiver, through two small holes w w drilled near its 
mouth. 
The combustion continues, until either the whole of the in- 
flammable gas is consumed, or till the cocks q and rare shut. 
The wedges v v are removed ; the receiver o o unscrewed ; 
and the bent tube removed from itf 5 place It is at this 
moment, that the cock r is useful, by preventing the escape of 
the gas from the receiver b through the tube s s . The upper 
part of the receiver is cooled by the application of a wet 
sponge. Without waiting, however, till the gas has attained 
the temperature of the atmosphere, a very small and sensible 
thermometer is introduced into it ; and the height of the 
mercury is noted, as soon as it becomes stationary. The 
volume of the residuary gas is then observed, and is reduced 
by calculation, to the bulk which it would occupy at 6o° of 
Fahrenheit. Either the whole, or an aliquot part of it, is 
removed by a transferring vessel, screwed upon the cock/. 
