anical invention with which his name is usually identified--that of
the Slide Rest. It continued to be his special delight, when engaged
in the execution of any piece of work in which he took a personal
interest, to introduce a system of identity of parts, and to adapt for
the purpose some one or other of the mechanical contrivances with which
his fertile brain was always teeming. Thus it was from his desire to
leave nothing to the chance of mere individual dexterity of hand that
he introduced the slide rest in the lathe, and rendered it one of the
most important of machine-tools. The first device of this kind was
contrived by him for Bramah, in whose shops it continued in practical
use long after he had begun business for himself. "I have seen the
slide rest," says Mr. James Nasmyth, "the first that Henry Maudslay
made, in use at Messrs. Bramah's workshops, and in it were all those
arrangements which are to be found in the most modern slide rest of our
own day,[2] all of which are the legitimate offspring of Maudslay's
original rest. If this tool be yet extant, it ought to be preserved
with the greatest care, for it was the beginning of those mechanical
triumphs which give to the days in which we live so much of their
distinguishing character."

A very few words of explanation will serve to illustrate the importance
of Maudslay's invention. Every person is familiar with the uses of the
common turning-lathe. It is a favourite machine with amateur
mechanics, and its employment is indispensable for the execution of all
kinds of rounded work in wood and metal. Perhaps there is no
contrivance by which the skill of the handicraftsman has been more
effectually aided than by this machine. Its origin is lost in the
shades of antiquity. Its most ancient form was probably the potter's
wheel, from which it advanced, by successive improvements, to its
present highly improved form. It was found that, by whatever means a
substance capable of being cut could be made to revolve with a circular
motion round a fixed right line as a centre, a cutting tool applied to
its surface would remove the inequalities so that any part of such
surface should be equidistant from that centre. Such is the
fundamental idea of the ordinary turning-lathe. The ingenuity and
experience of mechanics working such an instrument enabled them to add
many improvements to it; until the skilful artisan at length produced
not merely circular turning of t