1736 - 1819
The British instrument maker and engineer James Watt developed
an efficient steam engine which was a universal source of power
and thereby provided one of the most essential technological
components of the early industrial revolution.
Watt was born on Jan. 19, 1736, in Greenock, Scotland, the son
of a shipwright and merchant of ship's stores. He received an
elementary education in school, but of much more interest to him
was his father's store, where the boy had his own tools and
forge and where he skillfully made models of the ship's gear
surrounding him. In 1755 he was apprenticed to a London
mathematical instrument maker; at that time the trade primarily
produced navigational and surveying instruments. A year later he
returned to Scotland. By late 1757 Watt was established in
Glasgow as "mathematical instrument maker to the university."
About this time Watt met Joseph Black, who had already laid the
foundations of modern chemistry and of the study of heat. Their
friendship was of some importance in the early development of
the steam engine.
Invention of the Steam Engine
In the meantime, Watt had become engaged in his first studies on
the steam engine. During the winter of 1763/ 1764 he was asked
to repair the university's model of the Newcomen steam engine.
After a few experiments, Watt recognized that the fault with the
model rested not so much in the details of its construction or
in its malfunctioning as in its design. He found that a volume
of steam three or four times the volume of the piston cylinder
was required to make the piston move to the end of the cylinder.
The solution Watt provided was to keep the piston at the
temperature of the steam (by means of a jacket heated by steam)
and to condense the steam in a separate vessel rather than in
the piston. Such a separate condenser avoided the large heat
losses that resulted from repeatedly heating and cooling the
body of the piston, and so engine efficiency was improved.
There is a considerable gap between having a good idea for a
commercial invention and in reducing it to practice. It took a
decade for Watt to solve all the mechanical problems. Black lent
him money and introduced him to John Roebuck of the Carron
ironworks in Stirlingshire, Scotland. In 1765 Roebuck and Watt
entered into a partnership. However, Watt still had to earn his
own living, and his employment as surveyor of canal construction
left little time for developing his invention. However, Watt did
manage to prepare a patent application on his invention, and the
patent was granted on Jan. 5, 1769.
By 1773 Roebuck's financial difficulties brought not only Watt's
work on the engine to a standstill but also Roebuck's own
business. Matthew Boulton, an industrialist of Birmingham,
England, then became Watt's partner, and Watt moved to
Birmingham. He was now able to work full time on his invention.
In 1775 Boulton accepted two orders to erect Watt's steam
engine; the two engines were set up in 1776 and their success
led to many other orders.
Improvements in the Steam Engine
Between 1781 and 1788 Watt modified and further improved his
engine. These changes combined to make as great an advance over
his original engine as the latter was over the Newcomen engine.
The most important modifications were a more efficient
utilization of the steam, the use of a double-acting piston, the
replacement of the flexible chain connection to the beam by the
rigid threebar linkage, the provision of another mechanical
device to change the reciprocating motion of the beam end to a
rotary motion, and the provision of a centrifugal governor to
regulate the speed.
Having devised a new rotary machine, the partners had next to
determine the cost of constructing it. These rotary steam
engines replaced animal power, and it was only natural that the
new engine should be measured in terms of the number of horses
it replaced. By using measurements that millwrights, who set up
horse gins (animal-driven wheels), had determined, Watt found
the value of one "horse power" to be equal to 33, 000 pounds
lifted one foot high per minute, a value which is still that of
the standard American and English horsepower. The charge of
erecting the new type of steam engine was accordingly based upon
On Watt's many business trips, there was always a good deal of
correspondence that had to be copied. To avoid this irksome
task, he devised letter-press copying, in which, by writing the
original with a special ink, copies could be made by simply
placing another sheet of paper on the freshly written sheet and
then pressing the two together.
Watt's interests in applied chemistry led him to introduce
chlorine bleaching into Great Britain and to devise a famous
iron cement. In theoretical chemistry, he was one of the first
to argue that water was not an element but a compound.
In 1794 Watt and Boulton turned over their flourishing business
to their sons. Watt maintained a workshop where he continued his
inventing activities until he died on Aug. 25, 1819.
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This web page was last updated on:
17 December, 2008