Hydro-oxygen Blowpipe. 43 
The valve at the end of the rod, attached to the lever, L, being 
kept shut by the catch, M, the screw plug, H, removed, the acid 
is introduced through the aperture thus opened. In the next 
place, the plug being replaced, and the valve depressed by means 
of the lever and rod, so as no longer to close the opening, which 
it had occupied, the acid descends from the chamber into the cav- 
ity of the vessel beneath it. ‘The valve is of course restored to 
> 
the gas in the upper vessel bein sed td nearly half its 
previous bulk, the pressure will be nearly four atmospheres. It 
will, in fact, always be nearly double that which existed before 
the pipe, B, was closed. . 
In order that nearly the whole of the acid shall be expelled 
from the inferior vessel, the tray must be depressed till it touches 
the bottom of that vessel. 
The pressure being four atmospheres at commencement, as 
soon as, by means of a pipe attached to the valve-cock, N, an 
escape of gas is allowed, the acid is forced again upon the zine, 
and thus prevents a decline of pressure to any extent sufficient 
to interfere with the process. Pig iale Ms 
e gases may be used froma receiver in which they exist, 
in due proportion, safely by the following means:——~ 
Two safety tubes are to be made, not by Hemming’s process 
exactly, but as follows: ; 
es eoppet tube, silver soldered, of which the metal is about the 
eighth of an inch in thickness, is stuffed with the finest copper 
Wire, great care being taken to have the filaments straight and 
the acid and zinc, and finally suspend it altogether. Meanwhile 
ing conden 
*T have used for a gauge an instrament, like G, fig. 5, the tube being about two 
e 
feet in length, and sealed at the upper 
