ool led to an irregularity of
surface; and with the utmost care on the workman's part, he could not
avoid occasionally cutting a little too deep, in consequence of which
he must necessarily go over the surface again, to reduce the whole to
the level of that accidentally cut too deep; and thus possibly the job
would be altogether spoiled by the diameter of the article under
operation being made too small for its intended purpose.

The introduction of the slide rest furnished a complete remedy for this
source of imperfection. The principle of the invention consists in
constructing and fitting the rest so that, instead of being screwed
down to one place, and the tool in the hands of the workman travelling
over it, the rest shall itself hold the cutting tool firmly fixed in
it, and slide along the surface of the bench in a direction exactly
parallel with the axis of the work. Before its invention various
methods had been tried with the object of enabling the work to be
turned true independent of the dexterity of the workman. Thus, a
square steel cutter used to be firmly fixed in a bed, along which it
was wedged from point to point of the work, and tolerable accuracy was
in this way secured. But the slide rest was much more easily managed,
and the result was much more satisfactory. All that the workman had to
do, after the tool was firmly fitted into the rest, was merely to turn
a screw-handle, and thus advance the cutter along the face of the work
as required, with an expenditure of strength so slight as scarcely to
be appreciable. And even this labour has now been got rid of; for, by
an arrangement of the gearing, the slide itself has been made
self-acting, and advances with the revolution of the work in the lathe,
which thus supplies the place of the workman's hand. The accuracy of
the turning done by this beautiful yet simple arrangement is as
mechanically perfect as work can be. The pair of steel fingers which
hold the cutting tool firmly in their grasp never tire, and it moves
along the metal to be cut with an accuracy and precision which the
human hand, however skilled, could never equal.

The effects of the introduction of the slide rest were very shortly
felt in all departments of mechanism. Though it had to encounter some
of the ridicule with which new methods of working are usually received,
and for a time was spoken of in derision as "Maudslay's Go-cart,"--its
practical advantages were so decided that i