of a war that was to determine for
the future the course of political events in the Western Hemisphere.

Another event of April 1775 occurring in Birmingham now appears to have
been one that marked the beginning of a new era of technological
advance. It was near the end of this month that Boulton, at the Soho
Works, wrote to his partner and commented upon receiving the cast iron
steam engine cylinder that had been finished in John Wilkinson's boring
mill:

... it seems tolerably true, but is an inch thick and weighs about
10 cwt. Its diameter is about as much above 18 inches as the tin
one was under, and therefore it is become necessary to add a brass
hoop to the piston, which is made almost two inches broad.[4]

[Footnote 4: _Ibid._, vol. 2, p. 84.]

This cylinder indeed marked the turning point in the discouragingly long
development of the Watt steam engine, which for 10 years had occupied
nearly all of Watt's thoughts and all the time he could spare from the
requirements of earning a living. Although there were many trials ahead
for the firm of Boulton and Watt in further developing and perfecting
the steam engine, the crucial problem of leakage of steam past the
piston in the cylinder had now been solved by Wilkinson's new boring
mill, which was the first large machine tool capable of boring a
cylinder both round and straight.

The boring mill is pertinent to the development of linkages "in great,"
being the first of a new class of machine tools that over the next 50 or
60 years came to include nearly all of the basic types of heavy
chip-removing tools that are in use today. The development of tools was
accelerated by the inherent accuracy required of the linkages that were
originated by Watt. Once it had been demonstrated that a large and
complex machine, such as the steam engine, could be built accurately
enough so that its operation would be relatively free of trouble, many
outstanding minds became engaged in the development of machines and
tools. It is interesting, however, to see how Watt and others grappled
with the solutions of problems that resulted from the advance of the
steam engine.

During the 1770's the demand for continuous, dependable power applied to
a rotating shaft was becoming insistent, and much of Boulton's and
Watt's effort was directed toward meeting this demand. Mills of all
kinds used water or horses to turn "wheel-work," but, while these
sources of power were ad