easons better if I
insert it after what I had written further with regard to the cutting of
glass.

_How to Sharpen the Wheel Cutter._--The right way to do this is
difficult to describe in writing. You must, first of all, grind down the
"shoulders" of the tool, through which the pivot of the wheel goes, for
they are made so large that the wheel cannot reach the stone (fig. 6),
and must be reduced (fig. 7). Then, after first oiling the pivot so that
the wheel may run easily, you must hold the tool as shown in fig. 8, and
rub it swiftly up and down the stone. The angle at which the wheel
should rest on the stone is shown in fig. 9. You will see that the angle
at which the wheel meets the stone is a little _blunter_ than the angle
of the side of the wheel itself. You do not want to make the tool _too
sharp_, otherwise you will risk breaking down the edge, when the wheel
will cease to be truly circular, and when that occurs it is absolutely
useless. The same thing will happen if the wheel is _checked_ in its
revolution while sharpening, and therefore the pivot must be kept oiled
both for cutting and sharpening.

[Illustration: FIG. 5.]

[Illustration: FIGS. 6 and 7.]

It is a curious fact to notice that the tool, be it wheel or diamond,
that is _too sharp_ is not, in practice, found to make so good a cut as
one that is less sharp; it scratches the glass and throws up a line of
splinters.

_How to Cut Glass._--Hold the cutter as shown in the illustration (fig.
5), a little sloping towards you, but perfectly upright laterally; draw
it towards you, hard enough to make it just _bite_ the glass. If it
leaves a mark you can hardly see it is a good cut (fig. 10B), but if it
scratches a white line, throwing up glass-dust as it goes, either the
tool is faulty, or you are pressing too hard, or you are applying the
pressure to the wheel unevenly and at an angle to the direction of the
cut (fig. 10A). Not that you can make the wheel _move_ sideways in the
cut actually; it will keep itself straight as a ploughshare keeps in its
furrow, but it will press sideways, and so break down the edges of the
furrow, while if you exaggerate this enough it will actually leave the
furrow, and, ceasing to cut, will "skid" aside over the glass. As to
pressure, all cutters begin by pressing much too hard; the tool having
started biting, it should be kept only _just biting_ while drawn along.
The cut should be almost _noiseless_. You think you're n