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was as yet only employed in driving spinning…machines； rolling
metals； pumping water； and such like purposes。 In the working of wood
no machinery had been introduced beyond the common turning…lathe and
some saws； and a few boring tools used in making blocks for the navy。
Even saws worked by inanimate force for slitting timber； though in
extensive use in foreign countries； were nowhere to be found in Great
Britain。*
＇footnote。。。
Life of Sir Samuel Bentham； 97…8。
。。。＇
As everything depended on the dexterity of hand and correctness of
eye of the workmen； the work turned out was of very unequal merit；
besides being exceedingly costly。 Even in the construction of
comparatively simple machines； the expense was so great as to present
a formidable obstacle to their introduction and extensive use； and
but for the invention of machine…making tools； the use of the
steam…engine in the various forms in which it is now applied for the
production of power could never have become general。
In turning a piece of work on the old…fashioned lathe； the workman
applied and guided his tool by means of muscular strength。 The work
was made to revolve； and the turner； holding the cutting tool firmly
upon the long； straight； guiding edge of the rest； along which he
carried it； and pressing its point firmly against the article to be
turned； was thus enabled to reduce its surface to the required size
and shape。 Some dexterous turners were able； with practice and
carefulness； to execute very clever pieces of work by this simple
means。 But when the article to be turned was of considerable size；
and especially when it was of metal； the expenditure of muscular
strength was so great that the workman soon became exhausted。 The
slightest variation in the pressure of the tool 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 it gradually
made its way； and became an established tool in all the best
mechanical workshops。 It was found alike capable of executing the
most delicate and the most ponderous pieces of machinery； and as
slide…lathes could be manufactured to any extent； machinery；
steam…engines； and all kinds of metal work could now be turned out in
a quantity and at a price that； but for its use； could never have
been practicable。 In course of time various modifications of the
machine were introducedsuch as the planing machine； the
wheel…cutting machine； and other beautiful tools on the slide…rest
principle；the result of which has been that extraordinary
development of mechanical production and power which is so
characteristic a feature of the age we live in。
〃It is not； indeed； saying at all too much to state；〃 says Mr。
Nasmyth；*
＇footnote。。。
Remarks on the Introduction of the Slide Principle in Tools and
Machines employed in the Production of Machinery； in Buchanan's
Practical Essays on Mill Work and other Machinery。 3rd ed。 p。 397。
。。。＇
a most competent judge in such a matter； 〃that its influence in
improving and extending the use of machinery has been as great as
that produced by the improvement of the steam…engine in respect to
perfecting manufactures and extending commerce； inasmuch as without
the aid of the vast accession to our power of producing perfect
mechanism which it at once supplied； we could never have worked out
into practical and profitable forms the conceptions of those master
minds who； during the last half century； have so successfully
pioneered the way for mankind。 The steam…engine itself； which
supplies us with such unbounded power； owes its present perfection to
this most admirable means of giving to metallic objects the most
precise and perfect geometrical forms。 How could we； for instance；
have good steam…engines if we had not the means of boring out a true
cylinder； or turning a true piston…rod； or planing a valve face？ It
is this alone which has furnished us with the means of carrying into
practice the accumulated result's of scientific investigation on
mechanical subjects。 It would be blamable indeed；〃 continues Mr。
Nasmyth； 〃after having endeavoured to set forth the vast advantages
which have been conferred on the mechanical world； and therefore on
mankind generally； by the invention and introduction of the Slide
Rest； were I to suppress the name of that admirable individual to
whom we are indebted for this powerful agent towards the attainment
of mechanical perfection。 I allude to Henry Maudslay； whose useful
life was enthusiastically devoted to the grand object of improving
our means of producing perfect workmansh