WATT’S EXPERIMENTS ON STEAM--INVENTS THE SEPARATE CONDENSER.
It was in the year 1759 that Robison first called the attention of his
friend Watt to the subject of the steam-engine. Robison was then only
in his twentieth, and Watt in his twenty-third year. Robison’s idea was
that the power of steam might be advantageously applied to the driving of
wheel-carriages, and he suggested that it would be the most convenient
for the purpose to place the cylinder with its open end downwards to
avoid the necessity of using a working beam. Watt admits that he was very
ignorant of the steam-engine at the time; nevertheless, he began making
a model with two cylinders of tinplate, intending that the pistons and
their connecting-rods should act alternately on two pinions attached
to the axles of the carriage-wheels. But the model, being slightly and
inaccurately made, did not answer his expectations. Other difficulties
presented themselves, and the scheme was laid aside on Robison leaving
Glasgow to go to sea. Indeed, mechanical science was not yet ripe for
the locomotive. Robison’s idea had, however, dropped silently into the
mind of his friend, where it grew from day to day, slowly and at length
fruitfully.
At his intervals of leisure and in the quiet of his evenings, Watt
continued to prosecute his various studies. He was shortly attracted
by the science of chemistry, then in its infancy. Dr. Black was at that
time occupied with the investigations which led to his discovery of the
theory of latent heat, and it is probable that his familiar conversations
with Watt on the subject induced the latter to enter upon a series of
experiments with the view of giving the theory some practical direction.
His attention again and again reverted to the steam-engine, though he
had not yet seen even a model of one. Steam was as yet almost unknown in
Scotland as a working power. The first engine was erected at Elphinstone
Colliery, in Stirlingshire, about the year 1750; and the second more than
ten years later, at Govan Colliery, near Glasgow, where it was known
by the startling name of “The Firework.” This had not, however, been
set up at the time Watt began to inquire into the subject. But he found
that the College possessed the model of a Newcomen engine for the use of
the Natural Philosophy class, which had been sent to London for repair.
On hearing of its existence, he suggested to his friend Dr. Anderson,
Professor of Natural Philosophy, the propriety of getting back the model;
and a sum of money was placed by the Senatus at the Professor’s disposal
“to recover the steam-engine from Mr. Sisson, instrument maker, in
London.”
In the mean time Watt sought to learn all that had been written on
the subject of the steam-engine. He ascertained from Desaguliers,
from Switzer, and other writers, what had been accomplished by Savery,
Newcomen, Beighton, and others: and he went on with his own independent
experiments. His first apparatus was of the simplest possible kind. He
used common apothecaries’ phials for his steam reservoirs, and canes
hollowed out for his steam pipes.[74] In 1761 he proceeded to experiment
on the force of steam by means of a small Papin’s digester and a syringe.
The syringe was only the third of an inch in diameter, fitted with a
solid piston; and it was connected with the digester by a pipe furnished
with a stopcock, by which the steam was admitted or shut off at will. It
was also itself provided with a stopcock, enabling a communication to be
opened between the syringe and the outer air to permit the steam in the
syringe to escape. The apparatus, though rude, enabled the experimenter to
ascertain some important facts. When the steam in the digester was raised
and the cock turned, enabling it to rush against the lower side of the
piston, he found that the expansive force of the steam raised a weight of
fifteen pounds with which the piston was loaded. Then, on turning the cock
and shutting off the connexion with the digester at the same time that a
passage was opened to the air, the steam was allowed to escape, when the
weight upon the piston, being no longer counteracted, immediately forced
it to descend.
[74] At a meeting held in Glasgow in 1839 to erect a monument
to Watt, Dr. Ure observed:--“As to the latent heat of steam,”
said Mr. Watt to me, “it was a piece of knowledge essential to
my inquiries, and I worked it out myself in the best way that
I could. I used apothecaries’ phials for my apparatus, and by
means of them I got approximations sufficient for my purpose at
the time.” The passage affords a striking illustration of the
large results that may be arrived at by means of the humblest
instruments. In like manner Cavendish, when asked by a foreigner
to be shown over his laboratories, pointed to an old tea-tray
on the table, containing a few watch-glasses, test papers,
a balance, and a blowpipe, and observed, “There is all the
laboratory I possess.”
[Illustration: PAPIN’S DIGESTER.]
Watt saw that it would be easy to contrive that the cocks should be turned
by the machinery itself instead of by the hand, and the whole be made
to work by itself with perfect regularity. But there was an objection to
this method. Water is converted into vapour as soon as its elasticity is
sufficient to overcome the weight of the air which keeps it down. Under
the ordinary pressure of the atmosphere water acquires this necessary
elasticity at 212°; but as the steam in the digester was prevented
from escaping, it acquired increased heat, and by consequence increased
elasticity. Hence it was that the steam which issued from the digester
was not only able to support the piston and the air which pressed upon
its upper surface, but the additional load with which the piston was
weighted. With the imperfect mechanical construction, however, of those
days, there was a risk lest the boiler should be burst by the steam, which
was apt to force its way through the ill-made joints of the machine. This,
conjoined with the great expenditure of steam on the high-pressure system,
led Watt to abandon the plan; and the exigencies of his business for a
time prevented him pursuing his experiments. Watt’s own account of his
early experiments will be found appended as notes to Brewster’s edition
of the articles ‘Steam and Steam-engines,’ written by Dr. Robison for the
‘Encyclopædia Britannica,’ and afterwards published in a separate form.
[Illustration: THE NEWCOMEN MODEL.]
At length the Newcomen model arrived from London; and, in 1763, the little
engine, which was destined to become so famous, was put into the hands of
Watt. The boiler was somewhat smaller than an ordinary tea-kettle. The
cylinder of the engine was only of two inches diameter and six inches
stroke. Watt at first regarded it as merely “a fine plaything.” It was,
however, enough to set him upon a track of thinking which led to the most
important results. When he had repaired the model and set it to work, he
found that the boiler, though apparently large enough, could not supply
steam in sufficient quantity, and only a few strokes of the piston could
be obtained, when the engine stopped. The fire was urged by blowing, and
more steam was produced, but still it would not work properly. Exactly
at the point at which another man would have abandoned the task in
despair, the mind of Watt became thoroughly roused. “Everything,” says
Professor Robison, “was to him the beginning of a new and serious study;
and I knew that he would not quit it till he had either discovered its
insignificance, or had made something of it.” Thus it happened with the
phenomena presented by the model of the steam-engine. Watt referred to
his books, and endeavoured to ascertain from them by what means he might
remedy the defects which he found in the model; but they could tell him
nothing. He then proceeded with an independent course of experiments,
resolved to work out the problem for himself. In the course of his
inquiries he came upon a fact which, more than any other, led his mind
into the train of thought which at last conducted him to the invention of
which the results were destined to prove so stupendous. This fact was the
existence of Latent Heat.
In order to follow the track of investigation pursued by Watt, it
is necessary for a moment to revert to the action of the Newcomen
pumping-engine. A beam, moving upon a centre, had affixed to one end
of it a chain attached to the piston of the pump, and at the other a
chain attached to a piston that fitted into the steam cylinder. It was
by driving this latter piston up and down the cylinder that the pump was
worked. To communicate the necessary movement to the piston, the steam
generated in a boiler was admitted to the bottom of the cylinder, forcing
out the air through a valve, when its pressure on the under side of the
piston counterbalanced the pressure of the atmosphere on its upper side.
The piston, thus placed between two equal forces, was drawn up to the top
of the cylinder by the greater weight of the pump-gear at the opposite
extremity of the beam. The steam, so far, only discharged the office which
was performed by the air it displaced; but, if the air had been allowed
to remain, the piston once at the top of the cylinder could not have
returned, being pressed as much by the atmosphere underneath as by the
atmosphere above it. The steam, on the contrary, which was admitted by
the exclusion of the air, _could be condensed_, and a vacuum created, by
injecting cold water through the bottom of the cylinder. The piston being
now unsupported, was forced down by the pressure of the atmosphere on its
upper surface. When the piston reached the bottom, the steam was again let
in, and the process was repeated. Such was the engine in ordinary use for
pumping water at the time that Watt begun his investigations.
Among his other experiments, he constructed a boiler which showed by
inspection the quantity of water evaporated in any given time, and the
quantity of steam used in every stroke of the engine. He was astonished
to discover that a _small_ quantity of water in the form of steam, heated
a _large_ quantity of cold water injected into the cylinder for the
purpose of cooling it; and upon further examination he ascertained that
steam heated _six times_ its weight of cold water to 212°, which was
the temperature of the steam itself. “Being struck with this remarkable
fact,” says Watt, “and not understanding the reason of it, I mentioned it
to my friend Dr. Black, who then explained to me his doctrine of latent
heat, which he had taught for some time before this period (the summer of
1764); but having myself been occupied by the pursuits of business, if I
had heard of it I had not attended to it, when I thus stumbled upon one
of the material facts by which that beautiful theory is supported.”[75]
[75] Watt’s notes to Robison’s Articles on ‘Steam and
Steam-engines.’
When Watt found that water, in its conversion into vapour, became such a
reservoir of heat, he was more than ever bent on economising it; for the
great waste of heat involving so heavy a consumption of fuel, was felt
to be the principal obstacle to the extended employment of steam as a
motive power. He accordingly endeavoured, with the same quantity of fuel,
at once to increase the production of steam, and to diminish its waste.
He increased the heating surface of the boiler, by making flues through
it; he even made his boiler of wood, as being a worse conductor of heat
than the brickwork which surrounds common furnaces; and he cased the
cylinders and all the conducting-pipes in materials which conducted heat
very slowly. But none of these contrivances were effectual; for it turned
out that the chief expenditure of steam, and consequently of fuel, in the
Newcomen engine, was occasioned by the reheating of the cylinder after
the steam had been condensed, and the cylinder was consequently cooled by
the injection into it of the cold water. Nearly four-fifths of the whole
steam employed was condensed on its first admission, before the surplus
could act upon the piston. Watt therefore came to the conclusion, that to
make a perfect steam-engine, it was necessary that _the cylinder should be
always as hot as the steam that entered it_; but it was equally necessary
that the steam should be condensed when the piston descended,--nay, that
it should be cooled down below 100°, or a considerable amount of vapour
would be given off, which would resist the descent of the piston, and
diminish the power of the engine. Thus the cylinder was never to be at a
less temperature than 212°, and yet at each descent of the piston it was
to be less than 100°; conditions which, on the very face of them, seemed
to be wholly incompatible.
We revert for a moment to the progress of Watt’s instrument-making
business. The shop in the College was not found to answer, being too
far from the principal thoroughfares. If he wanted business he must go
nearer to the public, for it was evident that they would not come to him.
But to remove to a larger shop, in a more central quarter, involved an
expenditure of capital for which he was himself unequal. His father had
helped him with money as long as he could, but could do so no longer.
Though he was as much respected by his neighbours as ever, he had grown
poor by his losses; and, instead of giving help, himself needed it. Watt
therefore looked about him for a partner with means, and succeeded in
finding one in a Mr. John Craig, in conjunction with whom he opened a
retail shop in the Salt-market, nearly opposite St. Andrew’s Street, about
the year 1760; removing from thence to Buchanan’s Land, on the north side
of the Trongate, a few years later.[76] Watt’s partner was not a mechanic,
but he supplied the requisite capital, and attended to the books. The
partnership was on the whole successful, as we infer from the increased
number of hands employed. At first Watt could execute all his orders
himself, and afterwards by the help of a man and a boy; but by the end of
1764, the number of hands employed by the firm had increased to sixteen.
[76] The following advertisement in the ‘Glasgow Journal’ of the
1st Dec., 1763, fixes the date of this last removal:--
“James Watt has removed his shop from the Saltmercat to Mr.
Buchanan’s land in the Trongate, where he sells all sorts of
Mathematical and Musical Instruments, with variety of toys, and
other goods.”
His improving business brought with it an improving income, and
Watt--always a frugal and thrifty man--began to save a little money. He
was encouraged to economise by another circumstance--his intended marriage
with his cousin, Margaret Miller. In anticipation of this event, he had
removed from his rooms in the College to a house in Delftfield Lane--a
narrow passage then parallel with York Street, but now converted into
the spacious thoroughfare of Watt Street. Having furnished his house in a
plain yet comfortable style, he brought home his young wife, and installed
her there in July, 1764. The step was one of much importance to his
personal wellbeing. Mrs. Watt was of a lively, cheerful temperament; and
as Watt himself was of a meditative disposition, prone to melancholy, and
a frequent sufferer from nervous headache, her presence at his fireside
could not fail to have a beneficial influence upon his health and comfort.
[Illustration: WATT’S HOUSE, DELFTFIELD LANE.]
Watt continued to pursue his studies as before. Though still occupied
with his inquiries and experiments as to steam, he did not neglect his
proper business, but was constantly on the look-out for improvements in
instrument making. A machine which he invented for drawing in perspective
proved a success; and he made a considerable number of them to order,
for customers in London as well as abroad. He was also an indefatigable
reader, and continued to extend his knowledge of chemistry and mechanics
by perusal of the best books on these sciences.
Above all other subjects, however, the improvement of the steam-engine
continued to keep the fastest hold upon his mind. He still brooded over
his experiments with the Newcomen model, but did not seem to make much
way in introducing any practical improvement in its mode of working. His
friend Robison says he struggled long to condense with sufficient rapidity
without injection, trying one expedient after another, finding out what
would do by what would _not_ do, and exhibiting many beautiful specimens
of ingenuity and fertility of resource. He continued, to use his own
words, “to grope in the dark, misled by many an _ignis fatuus_.” It was a
favourite saying of his, that “Nature has a weak side, if we can only find
it out;” and he went on groping and feeling for it, but as yet in vain.
At length light burst upon him, and all at once the problem over which he
had been brooding was solved.
One Sunday afternoon, in the spring of 1765, he went to take an afternoon
walk on the Green, then a quiet, grassy meadow, used as a bleaching and
grazing-ground. On week-days the Glasgow lasses came thither with their
largest kail-pots, to boil their clothes in; and sturdy queans might be
seen, with coats kilted, tramping blankets in their tubs. On Sundays the
place was comparatively deserted, and hence Watt, who lived close at hand,
went there to take a quiet afternoon stroll. His thoughts were as usual
running on the subject of his unsatisfactory experiments with the Newcomen
engine, when the first idea of the separate condenser suddenly flashed
upon his mind. But the notable discovery is best told in his own words,
as related to Mr. Robert Hart, many years after:--
“I had gone to take a walk on a fine Sabbath afternoon. I had entered the
Green by the gate at the foot of Charlotte Street, and had passed the old
washing-house. I was thinking upon the engine at the time, and had gone as
far as the herd’s house, when the idea came into my mind that as steam was
an elastic body it would rush into a vacuum, and if a communication were
made between the cylinder and an exhausted vessel, it would rush into it,
and might be there condensed without cooling the cylinder. I then saw that
I must get rid of the condensed steam and injection-water if I used a jet,
as in Newcomen’s engine. Two ways of doing this occurred to me. First, the
water might be run off by a descending pipe, if an off-let could be got
at the depth of 35 or 36 feet, and any air might be extracted by a small
pump. The second was to make the pump large enough to extract both water
and air. He continued: I had not walked further than the Golf-house[77]
when the whole thing was arranged in my mind.”[78]
[77] About the site of the Humane Society’s House.
[78] Mr. Robert Hart’s ‘Reminiscences of James Watt,’ in
‘Transactions of the Glasgow Archæological Society, 1859.’
Great and prolific ideas are almost always simple. What seems impossible
at the outset appears so obvious when it is effected that we are prone to
marvel that it did not force itself at once upon the mind. Late in life
Watt, with his accustomed modesty, declared his belief that if he had
excelled, it had been “by chance and the neglect of others.” To Professor
Jardine he said “that when it was analysed the invention would not appear
so great as it seemed to be. In the state,” said he, “in which I found the
steam-engine, it was no great effort of mind to observe that the quantity
of fuel necessary to make it work would for ever prevent its extensive
utility. The next step in my progress was equally easy--to inquire what
was the cause of the great consumption of fuel: this, too, was readily
suggested, viz., the waste of fuel which was necessary to bring the whole
cylinder, piston, and adjacent parts from the coldness of water to the
heat of steam, no fewer than from fifteen to twenty times in a minute.”
The question then occurred, how was this to be avoided or remedied? It was
at this stage that the idea of carrying on the condensation in a separate
vessel flashed upon his mind, and solved the difficulty.[79]
[79] “The last step of all,” says Professor Jardine, “was more
difficult--the forming of the separate condensing vessel.
The great knowledge he had acquired of the mechanical powers
enabled him to construct it, but I have often heard him say
this was a work of great difficulty, and that he met with many
disappointments before he succeeded. I have often made use
of this beautiful analysis received from Mr. Watt, in another
department in which I have been long engaged, to illustrate and
encourage the progress of genius in youth, to show, that once
in possession of a habit of attention, under proper direction,
it may be carried from one easy step to another, till the mind
becomes qualified and invigorated for uniting and concentrating
effort--the highest exertion of genius.”
Mankind has been more just to Watt than he was to himself. There was no
accident in the discovery. It had been the result of close and continuous
study; and the idea of the separate condenser was merely the last step
of a long journey--a step which could not have been taken unless the
road which led to it had been traversed. Dr. Black says, “This capital
improvement flashed upon his mind at once, and filled him with rapture;” a
statement which, spite of the unimpassioned nature of Watt, we can readily
believe.
On the morning following his Sunday afternoon’s walk on Glasgow Green,
Watt was up betimes making arrangements for a speedy trial of his new
plan. He borrowed from a college friend a large brass syringe, an inch and
a third in diameter, and ten inches long, of the kind used by anatomists
for injecting arteries with wax previous to dissection. The body of the
syringe served for a cylinder, the piston-rod passing through a collar of
leather in its cover. A pipe connected with the boiler was inserted at
both ends for the admission of steam, and at the upper end was another
pipe to convey the steam to the condenser. The axis of the stem of the
piston was drilled with a hole, fitted with a valve at its lower end, to
permit the water produced by the condensed steam on first filling the
cylinder to escape. The first condenser made use of was an improvised
cistern of tinned plate, provided with a pump to get rid of the water
formed by the condensation of the steam, both the condensing-pipes and
the air-pump being placed in a reservoir of cold water.
“The steam-pipe,” says Watt, “was adjusted to a small boiler.
When steam was produced, it was admitted into the cylinder, and
soon issued through the perforation of the rod, and at the valve
of the condenser; when it was judged that the air was expelled,
the steam-cock was shut, and the air-pump piston-rod was drawn
up, which leaving the small pipes of the condenser in a state
of vacuum, the steam entered them and was condensed. The piston
of the cylinder immediately rose and lifted a weight of about
18 lbs., which was hung to the lower end of the piston-rod.
The exhaustion-cock was shut, the steam was readmitted into the
cylinder, and the operation was repeated. The quantity of steam
consumed and the weights it could raise were observed, and,
excepting the non-application of the steam-case and external
covering, the invention was complete, in so for as regarded the
savings of steam and fuel.”
[Illustration: WATT’S APPARATUS.]
But, although the invention was complete in Watt’s mind, it took him
many long and laborious years to work out the details of the engine.
His friend Robison, with whom his intimacy was maintained during these
interesting experiments, has given a graphic account of the difficulties
which he successively encountered and overcame. He relates that on his
return from the country, after the College vacation in 1765, he went
to have a chat with Watt and communicate to him some observations he
had made on Desaguliers’ and Belidor’s account of the steam-engine. He
went straight into the parlour, without ceremony, and found Watt sitting
before the fire looking at a little tin cistern which he had on his knee.
Robison immediately started the conversation about steam, his mind, like
Watt’s, being occupied with the means of avoiding the excessive waste of
heat in the Newcomen engine. Watt, all the while, kept looking into the
fire, and after a time laid down the cistern at the foot of his chair,
saying nothing. It seems that Watt felt rather nettled at Robison having
communicated to a mechanic of the town a contrivance which he had hit upon
for turning the cocks of his engine. When Robison therefore pressed his
inquiry, Watt at length looked at him and said briskly, “You need not fash
yourself any more about that, man; I have now made an engine that shall
not waste a particle of steam. It shall all be boiling hot,--ay, and hot
water injected, if I please.” He then pushed the little tin cistern with
his foot under the table.
Robison could learn no more of the new contrivance from Watt at that time;
but on the same evening he accidentally met a mutual acquaintance, who,
supposing he knew as usual the progress of Watt’s experiments, observed to
him, “Well, have you seen Jamie Watt?” “Yes.” “He’ll be in fine spirits
now with his engine?” “Yes,” said Robison, “very fine spirits.” “Gad!”
said the other, “the separate condenser’s the thing: keep it but cold
enough, and you may have a perfect vacuum, whatever be the heat of the
cylinder.” This was Watt’s secret, and the nature of the contrivance was
clear to Robison at once.
[Illustration: DR. JOSEPH BLACK.]
It will be observed that Watt had not made a secret of it to his other
friends. Indeed Robison himself admitted that one of Watt’s greatest
delights was to communicate the results of his experiments to others, and
set them upon the same road to knowledge with himself; and that no one
could display less of the small jealousy of the tradesman than he did. To
his intimate friend, Dr. Black, he communicated the progress made by him
at every stage; and the Doctor kindly encouraged him in his struggles,
cheered him in his encounter with difficulty, and, what was of still more
practical value at the time, he helped him with money to enable him to
prosecute his invention. Communicative though Watt was disposed to be, he
learnt reticence when he found himself exposed to the depredations of the
smaller fry of inventors. Robison says that had he lived in Birmingham
or London at the time, the probability is that some one or other of the
numerous harpies who live by sucking other people’s brains, would have
secured patents for his more important inventions, and thereby deprived
him of the benefits of his skill, science, and labour. As yet, however,
there were but few mechanics in Glasgow capable of understanding or
appreciating the steam-engine; and the intimate friends to whom he freely
spoke of his discovery were too honourable-minded to take advantage
of his confidence. Shortly after, Watt fully communicated to Robison
the different stages of his invention, and the results at which he had
arrived, much to the delight of his friend.
It will be remembered that in the Newcomen engine the steam was only
employed for the purpose of producing a vacuum, and that its working power
was in the down stroke, which was effected by the pressure of the air
upon the piston; hence it is now usual to call it the atmospheric engine.
Watt perceived that the air which followed the piston down the cylinder
would cool the latter, and that steam would be wasted in re-heating it.
In order, therefore, to avoid this loss of heat, he resolved to put an
air-tight cover upon the cylinder, with a hole and stuffing-box for the
piston-rod to slide through, and to admit steam above the piston, to act
upon it instead of the atmosphere. When the steam had done its duty in
driving down the piston, a communication was opened between the upper
and lower part of the cylinder, and the same steam, distributing itself
equally in both compartments, sufficed to restore equilibrium. The piston
was now drawn up by the weight of the pump-gear; the steam beneath it
was then condensed in the separate vessel so as to produce a vacuum, and
a fresh jet of steam from the boiler was let in above the piston, which
forced it again to the bottom of the cylinder. From an atmospheric it had
thus become a true steam-engine, and with a much greater economy of steam
than when the air did half the duty. But it was not only important to
keep the air from flowing down the inside of the cylinder: the air which
circulated within cooled the metal and condensed a portion of the steam
within; and this Watt proposed to remedy by a second cylinder, surrounding
the first with an interval between the two which was to be kept full of
steam.
One by one these various contrivances were struck out, modified, settled,
and reduced to definite plans; the separate condenser, the air and water
pumps, the use of fat and oil (instead of water as in the Newcomen engine)
to keep the piston working in the cylinder air-tight, and the enclosing
of the cylinder itself within another to prevent the loss of heat. They
were all but emanations from the first idea of inventing an engine working
by a piston, in which the cylinder should be kept continually hot and
perfectly dry. “When once,” says Watt, “the idea of separate condensation
was started, all these improvements followed as corollaries in quick
succession; so that in the course of one or two days the invention was
thus far complete in my mind.”
The next step was to construct a model engine for the purpose of embodying
the invention in a working form. With this object Watt hired an old
cellar, situated in the first wide entry to the north of the beef-market
in King Street, and there proceeded with his model. He found it much
easier, however, to prepare his plan than to execute it. Like most
ingenious and inventive men, Watt was extremely fastidious; and this
occasioned considerable delay in the execution of the work. His very
inventiveness to some extent proved a hinderance; for new expedients were
perpetually occurring to him, which he thought would be improvements, and
which he, by turns, endeavoured to introduce. Some of these expedients
he admits proved fruitless, and all of them occasioned delay. Another
of his chief difficulties was in finding competent workmen to execute
his plans. He himself had been accustomed only to small metal work, with
comparatively delicate tools, and had very little experience “in the
practice of mechanics _in great_,” as he termed it. He was therefore
under the necessity of depending, in a great measure, upon the handiwork
of others. But mechanics capable of working out Watt’s designs in metal
were then with difficulty to be found. The beautiful self-acting tools
and workmanship which have since been called into being, principally by
his own invention, did not then exist. The only available hands in Glasgow
were the blacksmiths and tinners, little capable of constructing articles
out of their ordinary walks; and even in these they were often found
clumsy, blundering, and incompetent. The result was, that in consequence
of the malconstruction of the larger parts, Watt’s first model was only
partially successful. The experiments made with it, however, served to
verify the expectations he had formed, and to place the advantages of the
invention beyond the reach of doubt. On the exhausting-cock being turned,
the piston, when loaded with 18 lbs., ascended as quick as the blow of
a hammer; and the moment the steam-cock was opened, it descended with
like rapidity, though the steam was weak, and the machine snifted at many
openings.
Satisfied that he had laid hold of the right principle of a working
steam-engine, Watt felt impelled to follow it to an issue. He could give
his mind to no other business in peace until this was done. He wrote
to a friend that he was quite barren on every other subject. “My whole
thoughts,” said he, “are bent on this machine. I can think of nothing
else.”[80] He proceeded to make another and bigger, and, he hoped, a
more satisfactory engine, in the following August; and with that object
he removed from the old cellar in King-street to a larger apartment in
the then disused pottery or delftwork near the Broomielaw. There he shut
himself up with his assistant, John Gardiner, for the purpose of erecting
his engine. The cylinder was five or six inches in diameter, with a
two-feet stroke. The inner cylinder was enclosed in a wooden steam-case,
and placed inverted, the piston working through a hole in the bottom of
the steam-case. After two months’ continuous application and labour it
was finished and set to work; but it leaked in all directions, and the
piston was far from air-tight. The condenser also was in a bad way, and
needed many alterations. Nevertheless, the engine readily worked with 10½
lbs. pressure on the inch, and the piston lifted a weight of 14 lbs. The
improvement of the cylinder and piston continued Watt’s chief difficulty,
and taxed his ingenuity to the utmost. At so low an ebb was the art of
making cylinders that the one he used was not bored but hammered, the
collective mechanical skill of Glasgow being then unequal to the boring of
a cylinder of the simplest kind; nor, indeed, did the necessary appliances
for the purpose then exist anywhere else. In the Newcomen engine a little
water was poured upon the upper surface of the piston, and sufficiently
filled up the interstices between the piston and the cylinder. But when
Watt employed steam to drive down the piston, he was deprived of this
resource, for the water and the steam could not coexist. Even if he had
retained the agency of the air above, the drip of water from the crevices
into the lower part of the cylinder would have been incompatible with
keeping the surface hot and dry, and, by turning into vapour as it fell
upon the heated metal, it would have impaired the vacuum during the
descent of the piston.
[80] “I have now (April, 1765) almost a certainty of the
_facturum_ of the fire-engine, having determined the following
particulars: The quantity of steam produced; the ultimatum of
the lever engine; the quantity of steam destroyed by the cold
of its cylinder; the quantity destroyed in mine; and if there
be not some devil in the hedge, mine ought to raise water to
44 feet with the same quantity of steam that theirs does to
32 (supposing my cylinder as thick as theirs), which I think I
can demonstrate. I can now make a cylinder 2 feet diameter and
3 feet high, only a 40th of an inch thick, and strong enough
to resist the atmosphere; _sed tace_. In short, I can think of
nothing else but this machine.”--Watt to Dr. Lind, quoted in
Muirhead’s ‘Life of Watt,’ 94–5.
While he was occupied with this difficulty, and striving to overcome it
by the adoption of new expedients, such as leather collars and improved
workmanship, he wrote to a friend, “My old white-iron man is dead;” the
old white-iron man, or tinner, being his leading mechanic. Unhappily,
also, just as he seemed to have got the engine into working order, the
beam broke, and having great difficulty in replacing the damaged part, the
accident threatened, together with the loss of his best workman, to bring
the experiment to an end. But though discouraged by these misadventures,
he was far from defeated, but went on as before, battling down difficulty
inch by inch, and holding good the ground he had won, becoming every
day more strongly convinced that he was in the right track, and that
the important uses of the invention, could he but find time and means to
perfect it, were beyond the reach of doubt.
But how to find the means! Watt himself was a comparatively poor
man; having no money but what he earned by his business of mechanical
instrument making, which he had for some time been neglecting through his
devotion to the construction of his engine. What he wanted was capital,
or the help of a capitalist willing to advance him the necessary funds to
perfect his invention. To give a fair trial to the new apparatus would
involve an expenditure of several thousand pounds; and who on the spot
could be expected to invest so large a sum in trying a machine so entirely
new, depending for its success on physical principles very imperfectly
understood?
There was no such help to be found in Glasgow. The tobacco lords, though
rich, took no interest in steam power, and the manufacturing class, though
growing in importance, had full employment for their little capital in
their own concerns.