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Page 20
Savory had the honour of showing this engine to His Majesty William III.
at Hampton Court Palace, and to the Royal Society. He proposed the
following uses, which perhaps may as well be mentioned, as they show how
little was then known of the real value of the power of steam:--1. To
raise water to drive mill-wheels--fancy erecting a steam engine now, of
say fifty horse-power, to raise water to turn a wheel of say thirty; 2.
To supply palaces and houses with water; 3. Towns with water; 4.
Draining marshes; 5. Ships; 6. Draining mines. There is one more thing I
may mention as curious, that though the steam he used must have been of
a high pressure, he did not use a safety-valve, though it had been
invented about the year 1681 by Papin. The consumption of fuel was
enormous in Savory's engine, as may easily be perceived from the great
loss of steam by condensation. Nevertheless, it was on the whole a good
and a workable engine, as we find the following said of it by Mr.
Farey:--"When comparison is made between Captain Savory's engine and
those of his predecessors, the result will be favourable to him as an
inventor and practical engineer. All the details of his invention are
made out in a masterly style, so as to make it a real workable engine.
His predecessors, the Marquis of Worcester, Sir S. Morland, Papin, and
others, only produced outlines which required to be filled up to make
them workable."
I must not detain you much longer before I proceed to the great Watt,
but I will just name Newcomen, who invented an engine with a cylinder,
and introduced a beam, to the other end of which he fixed a pump rod
like a common or garden pump. He made the weight of the pump and beam to
lift the piston, and then let the steam enter below the piston and
condensed it by a jet of water, thus causing a vacuum, when the pressure
of the atmosphere drove the piston from the top to the bottom of the
cylinder and lifted the pump rods in the usual way. There were various
cocks to be opened and shut in the working of this engine for the right
admission of steam and water at the required moments, a task which was
performed by boys who were termed cock-boys. I will now mention an
instance which, though in practice not to be imitated, yet was one of
those happy accidents which sometimes turn out for the best. One of
these boys, like many, more fond of play than work, got tired of turning
these cocks day by day, and conceived the idea of making the engine do
it for itself. This idle boy--we will not call him good-for-nothing, as
he proved good for a great deal in one way--was named Humphrey Potter,
and one day he fixed strings to the beam, which opened and shut the
valves, and so allowed him to play, little thinking this was one of the
greatest boons he could possibly have bestowed on the world at large,
for by so doing he rendered the steam-engine a self-acting machine.
We now come to a period which was destined to advance the cause of steam
to a far greater extent--in fact, the time which rendered the
steam-engine the useful and valuable machine it now is. This is the time
of James Watt. This great man, be it said to the credit of Scotland, was
born in Greenock, on the Clyde, on the 19th January 1736. His
grandfather was a farmer in Aberdeenshire, and was killed in one of the
battles of Montrose. His father was a teacher of mathematics, and was
latterly chief magistrate of Greenock. James Watt, the celebrated man of
whom I now speak, was a very delicate boy, so much so, that he had to
leave school on account of his health, and was allowed to amuse himself
as he liked. This he did in a scientific way, however, as an aunt of his
said to him one day: "Do you know what you have been doing? You have
taken off and put on the lid of the teapot repeatedly; you have been
holding spoons and saucers over the steam, and trying to catch the drops
of water formed on them by it. Is it not a shame so to waste your time?"
Mrs. Muirhead, his aunt, was little aware that this was the first
experiment in the way which afterwards immortalised her nephew.
In 1775 Watt was sent to London to a mathematical instrument maker, but
could not stay on account of his health, and soon afterwards came back
to Glasgow. He then got rooms in the College, and was made mathematical
instrument maker to the University, and he afterwards opened a shop in
the town. He was but twenty-one years of age when he was appointed to
this post in the College, and his shop became the lounge of the clever
and the scientific. The first time that his attention was directed to
the agency of steam as a power was in 1734, when a friend of his, Mr.
Robinson, who had some idea of steam carriages, consulted him on the
subject,--little is said of this, however. In 1762 Watt tried some
experiments on high-pressure steam, and made a model to show how motion
could be obtained from that power; but did not pursue his experiments on
account of the supposed danger of such pressure. He next had a model of
Newcomen's engine, which would not work well, sent him to repair. Watt
soon found out its faults, and made it work as it should do. This did
not satisfy him, and setting his active mind to work, he found in the
model that the steam which raised the piston had of course to be got rid
of. This, as a natural consequence, caused great loss of heat, as the
cylinder had to be cooled so as to condense the steam; and this led him
at last, after various plans, to adopt a separate vessel to condense
this steam. Of course, if you wish to save fuel, it is necessary that
the steam should enter a heated cylinder or other vessel, or else all
the steam is lost,--or in other words, condensed,--that enters it, until
it has from its own heat imparted so much to the cylinder as to raise
it to its own temperature, when it will no longer condense, and not till
then does it begin to exert its elastic power to produce motion. This
was the great object gained by James Watt, when, after various
experiments, he gave up the idea altogether of condensing steam in its
own or working cylinder, and then made use of a separate vessel, now
called the condenser.
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