(^188) THE WEALTH AND POVERTY OF NATIONS
A long time—sixty years—passed before James Watt invented an en
gine with separate condenser (1768) whose fuel efficiency was good
enough to make steam profitable away from the mines, in the new in
dustrial cities; and it took another fifteen years to adapt the machine to
rotary motion, so that it could drive the wheels of industry. In be
tween, engineers and mechanics had to solve an infinitude of small
and large problems of manufacture and maintenance. The task, for ex
ample, of making cylinders of smooth and circular cross section, so that
the piston would run tight and air not leak to the vacuum side, re
quired care, patience, and ingenuity.* In matters of fuel economy,
every shortcoming cost, and good enough was not good enough.
That was not all. Another line remained to be explored: high-
pressure engines (more than atmospheric), which could be built more
compact and used to drive ships and land vehicles. This took another
quarter century. Such uses put a premium on fuel economy: space was
limited, and one wanted room for cargo rather than for coal. The an
swer was found in compounding—the use of high-pressure steam to
drive two or more pistons successively; the steam, having done its work
in a high-pressure cylinder, expanded further in a larger, lower-pressure
cylinder. The principle was the same as that developed in the Middle
Ages for squeezing energy out of falling water by driving a series of
wheels. Compounding went back to J. C. Hornblower (1781) and
Arthur Woolf (1804); but it did not come into its own until the 1850s,
when it was introduced into marine engines and contributed mightily
to oceanic trade.
Nor was that the end of it. The size and power of steam engines were
limited by the piston's inertia. Driving back and forth, it required enor
mous energy to reverse direction. The solution was found (Charles A.
Parsons, 1884) in converting from reciprocating to rotary motion, by
replacing the piston with a steam turbine. These were introduced into
central power plants at the very end of the nineteenth century; into
- The technique that worked for boilers (roll up a sheet, weld the seams, and cap top
and bottom) would not work for an engine cylinder—too much leakage. The new
method, which consisted in boring a solid casting, was the invention of John Wilkin
son, c. 1776, who learned by boring cannon (patent of 1774). A year later, Wilkinson
was using the steam engine to raise a 60-pound stamping hammer to forge heavy
pieces. By 1783, he was up to 7.5 tons. With this he was soon building rolling mills,
coining presses, drawing benches (for wire manufacture), and similar heavy machinery.
"By a strange caprice of public fancy," writes Usher, "this grim and unattractive char
acter has never secured the fame he deserves as one of the pioneers in the development
of the heavy-metal trades." History of Mechanical Inventions, p. 372. Vulcan wasn't
pretty either.