402 On the Blowpipe. 
screwed. . There is a brass cock at K, the plug of which is 
worked by a key on the outside of the box. This cock is in- 
tended to regulate the flow of gas into the safety cistern at I, 
and also to prevent any water entering the pipe when the box 
is filled with water above the level of the division BD. When 
air or gas is introduced into the chamber F, previously filled with 
water through the pipe G, the air rises to the surface of the 
chamber, and expels the water through the cylinder E. The air. 
cannot return through the pipe G, as the bottom of the pipe is 
closed by the water. There is a small cock or plug at L, in or- 
der to empty the water occasionally. 
Figures 2 and 3 are sections of the safety appendages deli- 
neated of the real size. AB represents the cistern, which is 14 
inch in depth, and half an inch in its internal diameter; when in 
use, this cistern must be filled with mercury as high as the dotted 
line at B. G is a bent pipe through which the gas enters the 
cistern A B; to the end of this bent pipe there is screwed a small 
valve F; this valve consists of a conical plug which fits its socket 
perfectly air tight ; to the bottom of the plug there is attached 
a tube with one or more small holes drilled in the top of it. 
There is a small plate screwed round the bottom of the tube, in 
order to assist the opening of the valve by presenting a larger 
surface to the action of the air. The tube is fitted into a socket, 
which allows it to work easily up and down. The gas enters 
the tube at K, forces up the valve, and issues through the 
small holes below the plug, round which it passes into the bent 
pipeG. The valve must be made very true and light, and should 
have some small grooves at the top of the plug in order to afford 
a passage for the gas when the valve rises against the bottom of 
the bent pipe G. The section represents the valve lifted up as 
when inaction. The lid C D screws into the cistern at AB; it 
is hollowed out in a conical form at D, and has the hole at E 
filled either with a piece of cane or wire-gauze. The gas which 
enters the cistern at H, below the. surface of the mercury, col- 
lects in the conical part of the lid at D, and passes through the 
cane or wire-gauze at E into the jet pipe, which screws into the 
lidat C. The safety appendages are connected with the pipe H 
by a screw at the bottom of the valve as shown at I, fig. I. 
When the cane or wire-gauze does not prevent the ignition of 
the gas in the safety cistern, the expansion of the gas forces the 
mercury up the bent pipe G, which falling on the plug shuts the 
valve, and closes all communication with the air chamber F, 
fig. 1. As soon as the ignition of the gas has ceased, the mer- 
cury returns into its place, and the gas flows through the cistern 
as at the commencement. 
I shall now endeayour briefly to show the disadvantages at- 
tending 
