On the Blowpipe. 2 eS 
tending the use of Brookes’s gas blowpipe with Cumming’s safety 
cylinder as at present adopted, and will then state how I con- 
ceive they are obviated in the one I have described. Brookes’s 
blowpipe is obliged to have its sides made very thick and strong, 
in order to bear the condensation of the gases; consequently, 
when an explosion takes place, the sides are driven in all direc- 
tions, like the fragments of a bomb, to the great danger of those 
near it; whereas, admitting the possibility of an explosion in the 
one now described, I know from experiment, that when the gases 
are exploded in a tin vessel similar to the body of the hydraulic 
blowpipe, the effect is simply to tear open the sides without se- 
parating them from the rest of the instrument. When an ex- 
plosion takes place in Brookes’s blowpipe, it is usually destroyed 5 
whereas, owing to what has been before stated, the hydraulic 
blowpipe might generally be repaired at a trifling expense. 
From the experiment above alluded to, I know that the water 
greatly deadens the force of the explosion ; as the water is driven 
up the cylinder, which acts somewhat like a Welter’s tube of 
safety, and would probably, could the sides of the box be made 
sufficiently strong, entirely prevent the bursting of the blow- 
pipe. 
As the condensation in Brookes’s blowpipe diminishes, the 
flow of gas naturally becomes weaker, and this is probably the 
reason that the flame so frequently recedes. In addition to 
these inconveniences, the operator is interrupted every half mi- 
nute by the necessity of replenishing the blowpipe with gas, and 
cannot without an assistant continue an experiment for any 
length of time. In the hydraulic blowpipe the whole of the gas 
is introduced at ouce; consequently there is no interruption of 
the experiments, and the gas is not contaminated by remaining 
in the bladder, which very much deteriorates it. 
To fill the hydraulic blowpipe with gas, nothing more is ne- 
cessary than to fill a bladder, screw it on the top of the pipe G, 
and squeeze the gas out with the hands. No condensing syringe 
is required for that purpose. This, and the power of completely 
exhausting the air chamber by filling it with water, renders the 
gas much less liable to be contaminated by atmospheric air, 
In Cumming’s safety cylinder the oil, or water, is constantly 
dropping through the valve at the bottom; so that, if used for 
any length of time, the whole of the oil or water escapes through 
the gas chamber, and leaves the cylinder completely empty; the 
great force by which the valve is opened in Cumming’s safety 
cylinder, owing to the condensation of the gases, prevents it from 
closing properly when the gas within the cylinder is ignited, so 
that the expausion which then takes place (and which acts 
3E2 rather 
