ft for permanent regulation,
and must not be used to turn the supply on or cut it off. In some
respects this blow-pipe will be found more easy to manage than an
oxygas blow-pipe, for the glass is not so readily brought to the very
fluid state, and this will often enable a beginner who proceeds
cautiously to do more than he could with the more powerful instrument.

Though I have mentioned glass nozzles for the air supply, there is no
difficulty in making nozzles of brass. For this purpose let the end
of a brass tube of about one-eighth of an inch diameter be closed by a
bit of brass wire previously turned to a section as shown (Fig. 6),
and then bored by a drill of the required diameter, say -.035 inch. It
is most convenient to use too small a drill, and to gradually open the
hole by means of that beautiful tool, the watchmaker's "broach." The
edges of the jet should be freed from burr by means of a watchmaker's
chamfering tool (see Saunier's Watchmaker's Hand-book, Tripplin,
1882, p. 232, Sec. 342), or by the alternate use of a slip of Kansas
stone and the broach.

Fig. 6.

The construction of this blow-pipe is so simple, that in case any one
wishes to use a brush flame, he can easily produce one simply by
changing his air jets to bits of the same size (say one-eighth to
one-sixteenth of an inch) tubing, cut off clean. To insure success,
the ends of the tubes must be absolutely plane and regular; the
slightest inequality makes all the difference in the action of the
instrument. If a jet is found to be defective, cut it down a little
and try again; a clean-cut end is better than one which has been
ground flat on a stone. The end of a tube may, however, be turned in
a manner hereafter to be described so as to make an efficient jet.
Several trials by cutting will probably have to be made before success
is attained. For this kind of jet the air-pressure must be greatly
increased, and a large Fletcher's foot-blower or, better still, a
small double-action bellows worked with vigour will be found very
suitable. A fitting for this auxiliary blow-pipe is shown in Fig. 5
at B.

Professor Roentgen's discovery has recently made it necessary to give
more particular attention to the working of soft soda glass, and I
have been obliged to supplement the arrangements described by a table
especially intended for work with glass of this character. The
arrangement has proved so convenient for general work that I give the