ed with two manometers
and proper taps, etc. As I have reason to know that arrangements of
this kind work very ill unless really well made, I venture to add that
the Gerhardt arrangement to which I refer is No. 239 in his
catalogue, and costs about three pounds. It hardly gives enough air,
however, to work four blow-pipes, and the blast requires to be
steadied by passing the air through a vessel covered with a rubber
sheet.

In default of any of these means being available, one of Fletcher's
foot-blowers may be employed, but it must be worked very regularly. A
table mounted with one blow-pipe made on this plan, and worked by a
double-acting bellows, is recommended for students' use. For working
flint glass, the air jet may be one-eighth of an inch in diameter and
the pressure higher--this will give a brush flame. See Fig. 25.

It will be seen, on looking at the sketch of the blowpipe system, that
the pair of blow-pipes farther from the observer can be caused to
approach or recede at will by means of a handle working a block on a
slide. It often happens that after using all four blow-pipes at once
it is necessary to have recourse to one blow-pipe only, and to do this
conveniently and quickly is rather an object. Now, in my arrangement
I have to turn off both the gas and air from the farther system, and
then put in a bit of asbestos board to prevent the nozzles being
damaged by the flame or flames kept alight. As I said before, when
some experience is gained, glassblowing, becomes a very simple art,
and work can be done under circumstances so disadvantageous that they
would entirely frustrate the efforts of a beginner. This is not any
excuse, however, for recommending inferior arrangements.

Consequently, I say that the pipes leading in gas and air should be
all branches of one gas and one air pipe, in so far as the two remote
and one proximate blow-pipe are concerned, and these pipes should come
up to the table to the right hand of the operator, and should have
main taps at that point, each with a handle at least 2 inches long.
By this arrangement the operator can instantly turn down all the
blow-pipes but one, while, if the inverse operation is required, all
the three pipes can be started at once. [Footnote: I find, since
writing the above, that I have been anticipated in this recommendation
by Mr. G. S. Ram, The Incandescent Lamp and its Manufacture, p.
114.]

The separate air and gas taps must be le