ularly stable. The exit tube from the phosphorus pentoxide
should be drawn down to form a nozzle, from, say, half an inch to
one-eighth of an inch in diameter, so as to easily fit almost any bit
of rubber tube. The entry to the calcium chloride should be
permanently fitted to about a yard of fine soft rubber tubing, as
light as possible. The ends of this tube should terminate in a glass
mouthpiece, which should not be too delicate.

As an additional precaution against dust, I sometimes add a tube
containing a long plug of glass wool, between the phosphorus pentoxide
and the delivery tube, and also a tube containing stick potash on the
entry side of the calcium chloride tube, but it may safely be left to
individual judgment to determine when these additions require to be
made. In practice I always keep the affair set up with these
additions. The communication between all the parts should be
perfectly free, and the tubes should be nearly filled with reagents,
so as to avoid having a large volume of air to compress before a
pressure can be got up.

The arrangement will be clear by a reference to Fig. 8, which
illustrates the apparatus in use for joining two long tubes. I have
tried blowing-bags, etc, but, on the whole, prefer the above
arrangement, for, after a time, the skill one acquires in regulating
the pressure by blowing by the mouth and lips is such an advantage
that it is not to be lightly foregone.

Fig. 8.

Sec. 18. The Table.

The system of four blow-pipes is, of course, a fixture. In this case
the table may be about a yard square, and may be covered with asbestos
mill-board neatly laid down, but this is not essential. The table
should have a rim running round it about a quarter of an inch high.
The tools should be laid to the right of the worker, and for this
purpose the blow-pipes are conveniently fixed rather to the left of
the centre of the table, but not so far as to make the leg of the
table come so close to the operator as to make him uncomfortable, for
a cheerful and contented spirit ought to be part of the glass-worker's
outfit.

The most convenient height for a blow-pipe table--with the blow-pipes
about 2 inches above the table top--is 3 feet 2 inches. Nothing is
so convenient to sit upon as a rough music-stool with a good range of
adjustment. The advantage of an adjustable seat lies in the fact that
for some operations one wants to be well over the work, while in
others the advant