1816, Mr. Watt, in company
with his friend, Mr. Walkinshaw--whom the author some years
afterward heard relate the circumstance--made a voyage in a
steamboat as far as Rothsay and back to Greenock--an excursion,
which, in those days, occupied a greater portion of a whole day.
Mr. Watt entered into conversation with the engineer of the
boat, pointing out to him the method of "backing" the engine.
With a footrule he demonstrated to him what was meant. Not
succeeding, however, he at last, under the impulse of the ruling
passion, threw off his overcoat, and, putting his hand to the
engine himself, showed the practical application of his lecture.
Previously to this, the "back-stroke" of the steamboat engine
was either unknown, or not generally known. The practice was to
stop the engine entirely a considerable time before the vessel
reached the point of mooring, in order to allow for the gradual
and natural diminution of her speed.

The naval review at Spithead, upon the close of the Crimean war in 1856,
was the greatest up to that time. Ten vessels out of two hundred and
fifty still had not steam power, but almost all the others were
propelled by the screw--the spiral oar of Watt's letter of 1770--a
red-letter day for the inventor.

Watt's early interest in locomotive steam-carriages, dating from
Robison's having thrown out the idea to him, was never lost. On August
12, 1768, Dr. Small writes Watt, referring to the "peculiar improvements
in them" the latter had made previous to that date. Seven months later
he apprises Watt that "a patent for moving wheel-carriages by steam has
been taken out by one Moore," adding "this comes of thy delays; do come
to England with all possible speed." Watt replied "If linen-draper Moore
does not use my engine to drive his chaises he can't drive them by
steam." Here Watt hit the nail on the head; as with the steamship, so
with the locomotive, his steam-engine was the indispensable power. In
1786 he states that he has a carriage model of some size in hand "and am
resolved to try if God will work a miracle in favor of these carriages."
Watt's doubt was based on the fact that they would take twenty pounds of
coal and two cubic feet of water per horse-power on the common roads.

Another of Watt's recreations in his days of semi-retirement was the
improvement of lamps. He wrote the famous inventor of the Argand burner
fully upon the su