means of a cone turned up from a bit of
cast iron. This is put in the lathe and pushed into the mouth of the
bottle, the latter being supported by the hands. Use about the same
surface speed as would be employed for turning cast iron. In this
case the emery is better used with kerosene.

If a cylindrical bit of cast iron about an inch in diameter is turned
down conically nearly to a point, it will save a good deal of trouble
in making separate cones. If it gets ground into rings, and it
becomes necessary to turn it up, use a diamond tool until the skin is
thoroughly removed; the embedded emery merely grinds the edge off any
ordinary steel tool.

For diamond tools see Sec. 55.

Sec. 42. Use of the Lathe in Glass-working.

If it is necessary to remove a good deal of glass, time may be saved
by actually turning the glass in a lathe. According to the direction
given above for grinding a tube into the neck of a bottle, very little
glass need be removed if the drawing down is well done, so that for
this purpose turning is often unnecessary.

If the taper of the stopper be small and it is permissible to use a
thick tube, or if a solid stopper only has to be provided, or an old
stopper quickly altered to a new form, turning is very useful. The
glass may be "chucked" in any suitable manner, and run at a speed not
exceeding 10 feet per minute. Prepare a three-cornered file by
mercury-hardening and by grinding the end flat so as to form a cutting
angle of about 80 deg., and use a moderate amount of kerosene lubrication,
i.e. enough to keep the glass damp, but even this is not essential.
Use the file as an ordinary brass turning tool, and press much more
lightly than for metal turning. The glass will be found to scrape off
quite pleasantly.

By chucking glass tubes on wooden mandrells the ends may be nicely
turned in this manner ready for accurate closing by glass plates.

The process of grinding also is made much more rapid--at all events
in the earlier stages--by chucking either the stopper or the bottle
and holding the other member in the fingers, or in a wooden vice held
in the hands. The finishing touches are best given by hand.

I ought to say that I think a good deal of glass-grinding, as
practised in laboratories, might be advantageously replaced by glass
turning or filing and certainly will be by any one who will give these
methods a trial.

If one tube is to be ground into another, as in grinding a