THE INVENTOR OF THE STEAM-ENGINE
IT has long been supposed that the steam-engine was invented
by an Englishman of the name of James Watt. But the real inventor of
the steam-engine was Denis Papin, a French doctor, who invented the
engine while in Germany, and described it in a book which he published
in England, where he lived for many years. He made friends with Huygens
in Paris, and assisted him in carrying out his experiments on the
air-pump.
[Illustration: Fig. 40.--Papin’s improved Air-Pump.]
Huygens was very busy with a great variety of inventions, and was glad
to have this young assistant, who would carry out experiments for which
he himself had no time.
Papin made a number of improvements in the air-pump. One of these was
a cock, constructed on the principle of a gas cock or water tap, but
having two channels through it. Another great improvement which he
made in the air-pump was that he put the objects under a glass shade
instead of in a bottle. The shade was placed upon a flat plate, and its
edge was well greased, so that no air could enter from below.
[Illustration: Fig. 41.--One of Papin’s Experiments. A bladder
containing very little air swells up when a vacuum is produced in the
bell-jar, owing to the expansion of the air contained in it.]
In the middle of the plate was a hole, and the air was pumped out from
below through this hole. Air-pump experiments could thus be made with
a great number of different objects, one after the other, by simply
lifting off the shade and replacing it after putting the object upon
the plate. This method was easier than screwing off the cap of the
bottle used by Huygens.
[Illustration: Fig. 42.--Papin’s Mining Pump. Water flowing over the
water wheel Q turns the shaft P, provided with a double crank. This
drives the double air-pump OO, which sends air through the tube R
alternately out of the cylinders H and L at each turn of the cock S.
The pistons wind and unwind the ropes E and F, and draw up water in the
bucket C attached to the wheel B.]
Papin described these improvements in the year 1674 in a little
book called _Experiments on Empty Space, with a Description of the
Machines by which it is obtained_. The little book was dedicated to
his master Huygens, to whom he wrote as follows:--“These experiments
belong to you. I have made nearly all of them according to your
instructions. But I know that they are only a recreation to you. You
would never have written them down, and certainly you would never have
published them. And so, I am sure, you will not mind my doing it for
you.” Ten years after his book was published, Papin was appointed by
the Royal Society of London a curator of experiments, his duty being to
devise and show experiments to the members of the Society.
Papin was greatly interested in mining, and he was always puzzling
about some way of pumping up the water out of a mine. At that time
the pumping had all to be done by hand, and it was done by a string
of buckets, such as are used in wells. Papin had the idea of making a
water-mill--driven by a brook—pump the water out of the mine. But this
method was difficult unless a brook was close to the mine. However,
Papin designed a system by which the water-power could be transported
easily to the shaft of the mine. The water-mill drove the pistons in
two cylinders connected with a long pipe. The pistons compressed the
air and drove it along the pipe till it got to the mine.
At the mine there was a big wheel, or pulley, bearing a rope with
buckets attached to it. Other ropes were attached to the shaft of the
pulley, and were fixed to two other pistons moving in two cylinders.
These cylinders were connected with the pipe containing the compressed
air. First one cylinder was connected, and the buckets were lowered;
then a tap was turned which connected the other cylinder instead, and
this raised the buckets full of water.
This plan was a great improvement on the hand-pump (p. 70), but it was
not quite satisfactory; and it failed when the brook ran dry in summer
or was frozen in winter. Also the pump was rather a clumsy one. Papin
invented a better instrument, which he called the centrifugal pump,
and it is used to the present day. The pump consisted of a round, flat
box containing a paddle wheel which whirled the water round. The water
entered the box at the centre of the paddle-wheel, and on one side of
the box was a pipe through which the water escaped on being whirled
round. Papin tried to use this pump for pumping water, but he found
that he had no machine for moving it quickly enough, nor did he get
such a machine until he had invented the steam-engine. This, however,
he did not succeed in doing for many years, and meanwhile he invented a
number of other instruments.
One of these was a submarine boat. The first man to invent a
diving-bell which could move under water was named Drebbel. He was said
to have taken a trip under the Thames, disappearing entirely under
water and coming up in a distant place. Some years after this, Boyle
asked a medical doctor who had married a daughter of Drebbel, how it
was that Drebbel and his crew were not suffocated under the water. He
was told that Drebbel possessed a certain extract of air which enabled
him to breathe in a confined space. We are nowadays not able to tell
how much truth there was in the story concerning Drebbel.
[Illustration: Fig. 43.--An early form of Diving-Bell.]
But it is certain that Papin succeeded in constructing a diving-bell,
and in using it under water. His diving-bell was not a bell at all,
but a round box 6½ feet high, in which three men could stand upright.
When sunk under water it did not disappear entirely, because a pipe
stuck out of the top through which fresh air could enter or the used-up
air be pumped out. The pump which did this was one of Papin’s own
centrifugal pumps. On one side of the diving-bell was a very wide tube,
through which a man could crawl. It had a little door at the extreme
end which could be opened under water. This would, of course, let in
the water, but Papin, with one of his pumps, drove air through the tube
from within the diving-bell. This stream of air kept the water back,
and the poor man in the tube (he must have been very uncomfortable)
could do some work in the water outside, such as laying a mine for
exploding an enemy’s ship.
Few people know that Papin was the real inventor of the steam-engine.
But everybody acknowledges his invention of a kettle for cooking food
under high pressure. He called it a “digester.” When water is boiling
it cannot be made any hotter by putting greater heat under it. Greater
heat simply makes it boil away more quickly. But it can be made hotter
by preventing the steam from escaping. When the lid is stuck on tight,
and the spout is stopped up, the steam cannot escape until it reaches a
high pressure, and this means a higher temperature at which the water
boils.
Papin, therefore, constructed a kettle which was closed at the top by
means of a heavy weight. He did not close up the kettle with a screw,
since that would have led to an explosion. He only made sure that the
steam could not escape until it was hot enough and strong enough to
lift the heavy weight. People thought at that time that if they could
cook things at a very high temperature, they could get nourishment not
only out of meat, but out of the bones as well. They thought they could
make the bones eatable. Papin thought so too, and he cooked some bones
in his new kettle. The hardest bones of beef and mutton were made as
soft as cheese, and the extract from them made thick jelly, though the
bones themselves were not good to eat. The digester is used to obtain
gelatine from bones in this way at the present time.
[Illustration: Fig. 44.--Papin’s Cylinder, in which the Piston was
raised by boiling water under it.]
When Papin seriously set about inventing the steam-engine, he was
guided by what he remembered about a machine invented by Huygens. In
the year 1674 he had himself constructed this machine. It was intended
to raise water by an explosion of powder. The water was intended to be
used for the great water-works in the palace of the King of France.
A long cylinder containing a heavy piston was fixed in an upright
position. In the bottom of the cylinder was a plug which could be
screwed in. Before it was screwed in, some gunpowder and a slow match
were placed on the plug. Shortly after the plug was screwed in, the
match lighted the powder, the powder exploded, and drove the piston up
to the top of the cylinder. When the cylinder cooled down, the pressure
of the air drove down the piston. The piston was made to pull a chain
going over a pulley to which buckets were attached.
In the year 1690, Papin took the first step towards constructing the
steam-engine by inventing a cylinder in which the piston, instead of
being driven by the explosion of gunpowder, was forced upwards by
boiling some water under it. This plan made the plug unnecessary. The
piston A was driven up by the steam, and fixed at the top by a rod E
until it could be taken off the fire and made to do some work. There
was one difficulty about this cylinder. If the piston fitted tight,
it was not able to sink down to the level of the water at the bottom
of the cylinder, because in doing so the air in the cylinder would be
compressed, and would resist with a great force.
This difficulty was got rid of by Papin by means of another rod M,
which fitted in a hole in the piston. This rod was pulled out so as to
let the air escape. When the piston was down far enough, the rod was
pushed into the hole again so as to stop it up.
The great fault of this machine was that the cylinder had first to be
heated in order to drive out the piston and afterwards cooled, both of
which processes took time. About the year 1704, a German prince gave
Papin the order to build a steam-engine for pumping up water.
[Illustration: Fig. 45.--Papin’s Steam-Engine.]
Just at about that time Papin had seen a design of a machine by a man
of the name of Savery, which was not, however, a success. His own
machine consisted of a boiler which was to be put in the fire and
kept there. The steam from this boiler was conducted into a cylinder
half-filled with water. On the top of this water there was a wooden
float, so that the steam hardly came into contact with the water at
all. The float contained an iron box, into which a red hot iron
ball was placed. The steam, therefore, was not cooled on entering
the cylinder, but drove the float to the bottom of the cylinder and
forced the water into an upright pipe which was surrounded by another
cylinder. This water compressed the air in the second cylinder, and
valves were so arranged that the air could not turn back. It was
therefore used for forcing water up a pipe. Water was then allowed to
return into the first cylinder, and the operation was repeated. The
first cylinder afterwards always remained sufficiently hot to preserve
the power of the steam. In this respect Papin’s machine was a great
improvement on Newcomen’s machine set up at Wolverhampton in the year
1711.
Papin tried his machine in the presence of the German prince in the
year 1706. He did succeed in pumping water seventy feet high, but
the long pipes began to leak, and the German prince was so disgusted
that he would not give the money necessary to carry out any further
experiments. Papin, therefore, went back to London, and in the next
year he published a book called _New Art of Lifting Water with the
Help of Fire in a most Successful Manner_. He had great plans about
his machine. It was not only to pump water out of mines, but also to
fire guns, and to drive ships and carriages.
But Papin died a few years afterwards without being able to carry out
his great ideas beyond constructing a paddle-boat. He was one of the
world’s greatest inventors, but the engineers of his time were not
able to carry out his great inventions. Though his engine differs very
greatly from the steam-engines now made, it certainly contained a
piston working in a cylinder, and a safety valve, which are essential
parts of a modern steam-engine.