Fusion by the Hydro-orygen Blowpipe. 45 
pipes, six protrude through the brass casting forming the bottom 
of the copper case constituting the refrigerator, so as to be equi- 
distant from each other upon a circumference of three-fourths of 
an inch in diameter, the seventh protruding from the centre. 
The bores of these jets are such as not to admit a wire larger 
than ;', of an inch in thickness. Those of the larger instru- 
ments represented by the accompanying engravings were such as 
to admit wires of ;',th of an inch in thickness. 
The jet-pipes may be made by the following process :—A thin 
‘strip of sheet metal, somewhat wider than the length of the 
circumference required in the proposed pipe, after being roughly 
turned about a wire so as to form an imperfect tube, is drawn 
through several suitable holes in a steel plate, as in the wire- 
drawer’s process. Under this treatment the strip becomes con- 
verted into a hollow wire; the edges of the strip being brought 
into contact reciprocally, so as to leave only an almost impercep- 
tible crevice. Having drawn one strip of platina in this way, 
another strip sufficiently wide nearly to enclose it, is to be drawn 
over that first drawn, care being taken to have the crevices left 
at the meeting of the edges on contrary sides. ‘I'he compound 
hollow wire or tube thus fabricated, is finally to be drawn upon 
a steel wire of the diameter of the requisite bore. 
The following method of making jet-pipes, though more diffi- 
cult, is preferable; as there is less liability of the water of the 
refrigerator leaking into the bore. 
Select a very sound and malleable cylinder of platina, of about 
three-eighths of an inch in thickness, perforate it by drilling in a 
lathe, so that the perforation may be concentric with the axis. 
A drill between ;,th and }th of an inch in diameter may be 
employed. In the next place the cylinder may be elongated by 
the wire-drawing process, until the proper reduction of metallic 
thickness is effected, the diameter of the bore being prevented 
rom undergoing an undue diminution, by the timely introduc- 
ion of a steel wire. 
Of course, the metal must be annealed as often as it hardens, 
by drawing. For this purpose, a much higher temperature is 
necessary in the case of platinum, than in that of either copper, 
Silver, or gold. 
The annealing is best performed by the hydro-oxygen flame. 
If charcoal be used, the greatest care must be taken to have the 
fireplace clean. 
where great heat is to be resisted. No doubt, by employing pal- 
ium to solder the exterior juncture of the double drawn tubes 
above mentioned, they might answer as well nearly as when con- 
Structed of solid platinum. 
