578 
SECOND REPORT- 1832. 
out danger of explosion. The blowpipe of Newman, with Pro¬ 
fessor Cumming’s safety cylinder, were described. The im¬ 
proved blowpipe by Gurney was exhibited, and the well and 
safety-chamber also described with the improvement made by 
Wilkinson on the latter, by introducing layers of asbestos be¬ 
tween some of the discs of wire gauze. Mr. Hemmings stated 
that the latter, which is decidedly superior to all the others, 
occasionally, however, permitted the flame to recede through 
it, and that he had found when the gases contained a portion 
of water mechanically suspended in them, by passing through 
a long column of water in the well, the flame would return 
through the chamber many times in succession, and explode 
the gases in the well, and sometimes in the reservoir also. 
He then introduced his own safety-tube, which had with¬ 
stood every attempt to produce a recession of the flame through 
it, although tried under circumstances which invariably pro¬ 
duced explosion in the others. 
It is a cylinder of brass about six inches long and | inch di¬ 
ameter, filled with fine brass wire in lengths equal to that of 
the tube. The diameter of the wire should not exceed T £^th 
of an inch. When the tube is packed with the wires as closely 
as possible, a pointed rod of equal length is forcibly driven 
through the centre of the bundle of wires, which brings them 
into still closer approximation, and wedges them firmly toge¬ 
ther : the rod is about ^ inch diameter. 
The interstices between these wires, when thus closely 
packed, are extremely small, and become, in effect, congeries 
of metallic tubes, of smaller bore than the finest capillary tubes 
of glass. The cooling and conducting power of these is infi¬ 
nitely greater than could be effected, if a cylinder of equal 
length were filled with discs of the finest wire gauze, as the 
diameter of these tubes is infinitely less than that of the aper¬ 
tures in the finest wire gauze, and it possesses the important 
advantage of unbroken continuity in the tube from one extre¬ 
mity of the chamber to the other. Since the invention of this 
tube, Mr. Hemmings has dispensed with the well, &c. &c. of 
the ordinary blowpipe, and has operated constantly with the 
bladder of the mixed gases under his arm. In this manner he 
ignited, before the members of the Association, a piece of lime 
from the jet; he then removed the jet, and ignited, the gases 
at the extremity of the tube; and although this aperture is 
nearly | inch diameter, and pressure on the bladder was fre¬ 
quently withdrawn to permit recession of the flame if possible, 
yet no accident occurred. 
* An approximate idea of the size of the apertures may be 
