with
sheet-iron to protect it from the action of the fragments of hot glass
that will fall upon it. The tubes that supply air and gas to the
blow-pipe should come from beneath the table, and may pass through holes
cut for the purpose.

Many glass-blowers prefer to work at a rather high table, and sit on a
rather high stool, so that they are well above their work. No doubt this
gives extra command over the work in hand, which is often valuable. On
the other hand, it is somewhat fatiguing. For a long spell of labour at
work which is not of a novel character nor specially difficult, I am
disposed to recommend sitting on a chair or low stool, at a table of
such height as will enable the elbows to rest easily upon it whilst the
glass is held in the flame. The precise heights that are desirable for
the table and stool, and the exact position of the blow-pipe, will
depend upon the height and length of arm of the individual workman, and
it must therefore be left to each person to select that which suits him
best. A moveable rest made of wood, for supporting the remote end of a
long piece of glass tube a few inches above the table, whilst the other
end is being heated in the flame, will be found convenient.

=The Blow-pipe.=--Formerly a lamp, in which sweet oil or tallow was
burnt, was employed for glass-working, and such lamps are still
occasionally used. Thus, lamps burning oil or tallow were used on board
the _Challenger_ for hermetically sealing up flasks of water collected
at various depths to preserve them for subsequent examination. I shall
not, however, give an account of such a lamp, for the gas apparatus is
so much more convenient for most purposes that it has now practically
superseded the oil lamps. Fig. 1 shows a gas blow-pipe of exceedingly
simple construction, which can be easily made, and with which good work
can be done.

[Illustration: FIG. 1.]

The tube _A_ is of brass, and has a side tube _B_ brazed to it, ten to
twelve centimetres from the end _E_, according to the dimensions of the
tube. A tube of glass, _EC_, is fitted into _A_ by a cork at _D_. _B_
is connected to a supply of gas by a flexible tube, _C_ is similarly
connected to the blower. By means of _CE_ a stream of air can be forced
into gas burning at the mouth of the blow-pipe _G_, and various flames,
with the characters described in a later section, can be produced with
this instrument. For producing the pointed flame (Fig. 3, p. 9) the
open