hammer for forging iron and making
steel. "Three hundred blows per minute--a thing never done before,"
filled him, as his biographer says, with feelings of excusable
pride. Another patent in the steam-engine series, taken out in 1784,
contained, besides other methods of converting a circular or angular
motion into a perpendicular or rectilineal motion, the well-known
and much-admired _parallel motion_, and the application of the
steam-engine to give motion to wheel-carriages for carrying persons
and goods. To ascertain the exact number of strokes made by an
engine during a given time, and thereby to check the cheats of the
Cornish miners, Watt also invented the "Counter," with its several
indexes. Among his leading improvements, introduced at various
periods, were the _throttle-valve_, the application of the
_governor_, the _barometer_ or float, the _steam-gauge_, and the
indicator. The term during which he seems to have thus combined the
greatest maturity with the greatest activity of intellect, and the
portion of his life which they comprehended, was from his fortieth
to his fiftieth year. Yet it was a term of increased suffering from
his acute sick-headaches, and remarkable for the infirmities over
which he triumphed; notwithstanding, he himself complained of his
"stupidity and want of the inventive faculty."

Watt's chemical studies in 1783, and the calculations they involved
from experiments made by foreign chemists, induced him to make a
proposal for a philosophical _uniformity of weights and measures_;
and he discussed this proposal with Priestley and Magellan. While
Watt was examining the constituent parts of water, he had
opportunities of familiar intercourse not only with Priestley, but
with Withering, Keir, Edgeworth, Galton, Darwin, and his own
partner, Boulton--all men above the average for their common
interest in scientific inquiries. Dr. Parr frequently attended their
meetings, and they kept up a correspondence with Sir William
Herschel, Sir Joseph Banks, Dr. Solander, and Afzelius. Mrs.
Schimmelpenninck, who was greatly given to physiognomical studies,
has left us this picture of Watt at this period.

"Mr. Boulton was a man to rule society with dignity; Mr. Watt, to
lead the contemplative life of a deeply introverted and patiently
observant philosopher. He was one of the most complete specimens of
the melancholic temperament. His head was generally bent forward, or
leaning on his hand in meditation;