suitable size and grind it to
fit, as described below. If only the little cross-piece at the end is
broken off, it can easily be replaced. In most ordinary stopcocks the
plug is solid, but the little handle is hollow. What has been said above
regarding care in heating and cooling glass rod applies with especial
force here. It is usually best to wind the whole of the plug with
several thicknesses of asbestos cord, leaving bare only the end where
the handle is to be joined. This diminishes the danger of cracking the
plug by too rapid heating, and also makes it more comfortable to hold. A
piece of rather thick-walled tubing of suitable diameter is chosen,
drawn out so as to have a suitable taper (taking care to heat enough of
the tube so that the capillary tail has good wall-thickness and
strength), and then a corresponding taper is drawn to form the other
side of the handle. The result is shown in Fig. 15, _a_. The capillary
tail is now heated and bent back to form a handle which will be in the
same straight line as the axis of the plug (_b_, Fig. 15) and the main
part of the tube drawn off at the dotted line, making a neat seal at
that point. The broken end of the plug is now slowly warmed in the smoky
flame, the heat gradually increased by a gentle stream of air from the
bellows, and the point at which this handle is to be attached finally
brought to the temperature at which the glass flows freely. In the mean
time, the little handle has been warmed almost to the softening point.
It is now quickly pushed into place (_c_, Fig. 15), taking care that its
axis is parallel to the hole in the plug, and then drawn away from the
plug just enough to make a graceful neck instead of the bulging one
indicated by the arrow in the figure. With a fine pointed flame the
little tail is now drawn off at the point indicated by the dotted line
(_c_, Fig. 15) and the whole carefully annealed. If necessary, the
handle can be blown a little before the tail is removed. Local heating
and blowing at the point where the handle joins the plug is often
necessary in order to make a smooth job.

[Illustration: FIG. 15.--Stopcock plug.]

=Regrinding.=--This is sometimes necessary to make stopcocks tight, when
the grinding has not been properly done in the factory. For this, a very
little fine flour of emery or carborundum is the best and quickest. If
this is not at hand, some clean sand may be ground in an agate mortar,
and if possible sieved. Only m