whim-engines from Creuver and Wheal Abraham, and put it as a pumping
engine in Wheal Kitty, where it continued at work for about fifteen
years. The boiler was of cast iron, in two lengths bolted together,
about 6 feet in diameter and 10 feet long. At one end a piece was
bolted, into which the cylinder was fixed, so that it had the steam
and water around it. There was an internal wrought-iron tube that
turned back again to the fire-door end, where the wrought-iron chimney
was fixed; the fire-grate end of the tube was about 2 feet 6 inches
in diameter, and tapered down to about 1 foot 6 inches at the chimney
end. It was a puffer, working 60 lbs. of steam to the inch; it worked
very well. There were several others in the county at that time
something like it. It was made at the Neath Abbey Works in Wales."[69]
[Footnote 69: Recollections of Captain G. Eustace, engineer, residing at
Hayle, 1868.]
These boilers were of the kind first tried in Cornwall about 1800. The
oval tube in the Kensington model of 1798 continued in use in Cornwall
for many years. The cast-iron outer casing was soon abandoned, though
one of them in Wales remained in work fifty years, using steam of 60
lbs. to 100 lbs. to the inch.
"MY DEAR JANE,
"HAYLE FOUNDRY, _August 26th, 1810_.
"I saw Captain Andrew Vivian on Wednesday, who told me that he had
been offered 150_l._ a year to inspect all the engines in the county,
and report what duty they were doing, in order to stimulate the
engineers. He declined accepting it, having too much to do already;
and he thought it would be worth Trevithick's notice, as it would not
take him more than a day or two in a month.
"I remain, my dear Jane,
"Yours sincerely,
"H. HARVEY.
"I wrote this letter on Sunday, with an intention of sending it then,
but thought it best to wait until this day, in hopes of hearing the
determination of Government in your favour; but your letter has
arrived without the desired information. All that I can now say is,
to desire that Trevithick will make up his mind to return to Cornwall
immediately.
"H. H."
The application to the Government for remuneration for benefits
conferred on the public was unsuccessful. The office of registrar of
Cornish engines was unsuitable; fortunately for mining interests,
illness obliged Trevithick to revisit his native county, for by
the increased power and economy of his engines Dolcoath Mine, so
frequently mentioned, and so important in olden time, now returns
70,000_l._ worth of tin yearly.
Trevithick's first act on returning to Cornwall in 1810 was the
erection of the high-pressure boilers and pole vacuum engine at Wheal
Prosper; at the same time renewing his proposals to Dolcoath to use
his improved boilers, which had been broken off in 1806, and to apply
high-pressure steam to their low-pressure Watt engine, with the same
safety and profit as in Wheal Prosper; the evidence was undeniable,
so his plans were agreed to, and in the early part of 1811 the
high-pressure boilers, called the Trevithick or Cornish boilers, were
constructed in the Dolcoath Mine under his directions.
Old John Bryant, who worked the Dolcoath large engines both before and
after the introduction of higher pressure steam, including the Carloose
or Bullan Garden 45-inch cylinder engine, Wheal Gons 63-inch cylinder
single engine, and the Watt 63-inch cylinder double, with the bee-but
boiler, such as Trevithick, sen., used in 1775,[70] followed by the Watt
waggon boiler, and afterwards by the globular boiler of Trevithick,
jun., in 1799,[71] and still later also with the cylindrical boiler of
1811, gave the following statement, when seventy-four years old, to the
writer:--
[Footnote 70: See vol. i., p. 25.]
[Footnote 71: See vol ii., p. 119.]
"In the old bee-but and the waggon boiler the steam pressure in the
boiler was not much; we did not trouble about it so long as the
engines kept going: when the steam was too high it blew off through
the feed-cistern. When Captain Trevithick tried his high steam in
Dolcoath we hoisted up the feed-cistern as high as we could; when
the steam got up, it blew the water out of the cistern. Captain Dick
holloed out, 'Why don't you trig down the clack?'
"The cylindrical boilers when they were first put in leaked very
much; we could hardly keep up the fire sometimes. I reckon the steam
was 30 or 40 lbs. to the inch. Captain Dick's boilers made him lots
of enemies. I heard say in one mine where he was trying his boilers
against Boulton and Watt's waggon, a lot of gunpowder was put into the
heap of coal."[72]
[Footnote 72: Old John Bryant's statement in 1858.]
The waggon or hearse Watt boiler was attached to his 63-inch cylinder
double, and the old man recollected having raised the water cistern,
when Trevithick's globe boiler gave an increased pressure in 1799, ten
or twelve years before the cylindrical boilers were made in Dolcoath.
"Some time after Captain Dick's globe boiler and steam-whims had been
at work in Dolcoath, a letter came down from London, saying that he
would save the mine 100_l._ a month if they would put in one of his
new plan boilers.
"They were put in hand in the mine, and I worked about them; they were
wrought-iron cylindrical boilers, about 20 feet long, and 5 or 6 feet
in diameter; the fire-tube was about 3 feet in diameter; the fire
returned around the outside in brick flues. Three boilers were put in
side by side.
"When Captain Dick first tried them, he said to the men, Now mind, the
fire-bars must never have more than six inches of coal on them; give a
shovel or two to one boiler, and then to another. When Captain Dick's
back was turned, the men said they wasn't going to do anything of the
sort, there would never be no rest for them. They used to say that the
boilers saved more than 170l. the first month."[73]
[Footnote 73: Clark's recollections in 1869, when he was eighty-three
years old, and resided at Redruth.]
Clark, when a boy, in 1799, helped to construct Trevithick's globular
boiler in Dolcoath, and recollected the events of the few following
years, during the contests with the whim-engines about 1806, and the
introduction of the large cylindrical wrought-iron boilers for the
pumping engines in 1811, and the struggle preceding the downfall
of the Watt low-pressure steam vacuum engine, to make room for the
high-pressure expansive steam-engine, with or without vacuum.
"About 1812 Captain Trevithick threw out the Boulton and Watt waggon
boilers at Dolcoath and put in his own, known as Trevithick's boiler.
They were about 30 feet long, 6 feet in diameter, with a tube about 3
feet 6 inches in diameter going through its length. There was a space
of about 6 inches between the bottom of the tube and the outer casing.
Many persons opposed the new plans. The Boulton and Watt low-pressure
engine did not work well with the high steam, and the water rose
in the mine workings. Captain Trevithick, seeing that he was being
swamped, received permission from the mine managers to dismiss the
old engine hands and employ his own staff. Captain Jacob Thomas was
the man chosen to put things right. He never left the mine until the
engine worked better than ever before, and forked the water to the
bottom of the mine. Before that time the average duty in the county by
the Boulton and Watt engines was seventeen or eighteen millions, and
in two or three years, with Trevithick's boilers and improvements in
the engines, the duty rose to forty millions. About 1826 he (Captain
Vivian) was manager of Wheal Towan; their engines were considered the
best in the county, doing eighty-seven millions; they had Trevithick's
boilers, working with high-pressure steam and expansive gear; few if
any of Boulton and Watt's boilers could then be found in the county.
Sir John Rennie and other scientific men, who doubted the reports of
the duty, came and made their own trials with the engines, and were
satisfied that the duty was correctly reported.
"About that time a Mr. Neville requested him to report on the engines
at his colliery at Llanelthy; one was an atmospheric of Newcomen's,
doing six millions; and four or five of Boulton and Watt's patent
engines averaged fourteen millions."[74]
[Footnote 74: Captain Nicholas Vivian was a schoolfellow and intimate
friend of Trevithick's; he resided at Camborne in 1858, when he gave
his recollections.]
When at last the cylindrical high-pressure boiler was admitted, and men
had been taught to fire them, many persons still liked the old plans,
and among them the easy-going low-pressure enginemen. The consequence
was that the Watt engines under their management refused the early
doses of Trevithick's high steam, not easily digesting it, and their
obstinacy nearly swamped Trevithick and his plans.
"When a little boy, about 1812, I frequently carried my father's
dinner from Penponds to Dolcoath Mine. One day, not finding him in the
engine-house, I sought him in the account-house, but not knowing him
in a miner's working dress, refused to give him his dinner. William
West then worked with him. I heard there was difficulty in making the
new boilers and the old engine work well; engineers from other mines
looked on from a distance, not liking the risk of explosion. People
seemed to be against the new plans; some labourers worked with them."
This narration--sixty years after the events--from Mr. Richard
Trevithick, the eldest son of the engineer, shows that William West
helped in applying high-pressure steam to the Watt low-pressure engine,
and that but few sympathized with the innovators on old customs; but
among them was Captain Jacob Thomas, who successfully fed the old
engine with strong steam.
At that time the Watt engines in Cornwall had been doing seventeen or
eighteen millions; Trevithick's new boilers increased their duty to
forty millions.
"William Pooly[75] was working in Dolcoath before Captain Trevithick's
new boilers were put in, and helped to put them in.
[Footnote 75: William Pooly worked the Dolcoath 76-inch engine in 1869;
his recollections were given in the old engine-house, on the spot once
occupied by Watt and his 63-inch great double engine.]
"The Shammal 45-inch engine was an open-top cylinder, with a chain to
the segment-head wooden beam. So was the 63-inch cylinder Stray Park
engine, then called Wheal Gons[76] in Dolcoath sett, and the Boulton
and Watt 63-inch cylinder double-acting.
[Footnote 76: Smiles speaks of this as Bonze's.]
"There used to be great talking about different boilers; a boiler of
Captain Trevithick's worked with higher steam than the others. Just
before Captain Dick came back to the mine a Boulton and Watt hearse
boiler had been repaired with a new bottom; it was never used. I and
William Causan took a job to cut up the boiler at 1_s._ 6_d._ the
hundredweight; it weighed 17 tons. Jeffrie and Gribble were the mine
engineers; Glanville used to be considered Captain Dick's man in the
mine. You could stand upright on the fire-bars in the middle hollow
of the hearse boiler, and so you could in the outside brick flues;
the middle hollow was like a horse-shoe. When Captain Dick put in his
cylindrical boilers he altered the 63-inch single; there was hardly
anything of her left but the main wall, with the wood bob and a chain
to the piston-rod, and also to the pump-rods. There was an air-pump,
and I think a second-hand cylinder was brought, but it was a 63-inch;
the old Shammal engine had been altered, too.
"The new boiler put in was about 8 feet in diameter and from 30 to
40 feet long, two round tubes went through it; the fire-place in one
end of one tube and in the other end of the other tube; after going
through the tubes the draught went into the brick flues under the
bottom and sides. When the new engine was put in, Gribble said, Why,
these little things will never get steam enough; everybody said so.
"In the Boulton and Watt engines we didn't trouble about feed-pumps
and gauge-cocks.
"A wire came through a stuffing box in the top of the boiler; a
biggish stone in the boiler was fastened to one end of the wire, the
other end was fastened to a weighted lever near the water cistern,
just above the boiler; when the water got low the stone opened the
valve in the water cistern. That was when they were putting in Captain
Dick's new cylindrical boilers to the old 63-inch engine. She did so
much more work, with less coal, that in a year or so they agreed to
throw out Boulton and Watt's engine, and to put in a stronger one that
could stand Captain Dick's high steam. Jeffrie and Gribble were the
mine engineers that put her up. The 76-inch cylinder came from Wales.
The big beam was cast at Perran Foundry in 1815; you can see the name
and date upon it now. The boiler and the gear-work were made in the
mine. The exhaust-valve is exactly as when it was put in, worked by
a rack-and-tooth segment. The equilibrium valve is unchanged, except
that the rack is taken out and a link put in.
"The steam-valve was taken out soon after she went to work, and the
present double-beat valve was put in; it is the first of the kind I
ever saw. Some were made before that time with a small valve on the
top of the big one, that opened first, to ease the pressure.
"John West[77] fitted up the valve-gear in the mine with the expansive
tappets, the same as when she stopped a month or two ago, and the same
as the present new one has.
[Footnote 77: Three Wests, all skilful mechanical engineers, were
employed at that time in Dolcoath, all of them known to the writer,
who thinks the double-beat valve was the handiwork of John West, not
related to Trevithick's partner.]
"Captain Dick's cutting off his strong steam at an early part of the
stroke, used to make the steam-valve strike very hard; so the new
plan valve, with a double beat, was put in; that must have been about
1816 or 1817; and the valve and expansive horn for working were just
exactly like what they have put into the present new engine in 1869.
She was the engine that showed them how to fork the water, and burn
only half the coal.
"I worked in this mine the old atmospheric engines, and then Boulton
and Watt; and then Trevithick's boilers in Boulton and Watt; and then
Trevithick's boilers and engine; and now I come every day to the new
engine, though I can't do much. They give me 35_s._ a month; and my
name is William Pooly, Dolcoath, 1869."
Three years ago (in 1869), when the writer entered the old engine-house
in which Watt's 63-inch cylinder double had been erected in 1780,
adjoining the old walls that then enclosed that early Newcomen 45-inch
cylinder Carloose engine, re-erected by Trevithick, sen., in 1775 in
Bullan Garden portion of Dolcoath, an old man sat near a small window
in a recess in the thick wall of the engine-house, within reach of
the gear-handles of the Jeffrie and Gribble 76-inch cylinder engine
that Trevithick, jun., had erected in 1816 on the foundations of the
removed Watt engine; he held in one hand a portion of slate from the
roof, and in the other an old pocket-knife, one-half of the blade of
which had been broken off, leaving a jagged fracture, with which he
made the figures of some calculation on the rude slate; on his nose
rested the brass frame of a pair of very ancient spectacles, with horn
glasses. He answered the writer's question by, "Yes, I am William
Pooly; I worked this engine, and the other engines before it--the great
double and the little Shammal working out of the same shaft; and I am
seventy-four years of age. The 63 single worked upon a shaft up there;
she was called Wheal Gons." That old man, still living, had worked in
Dolcoath Mine one of the first steam-engines of Newcomen; the 45-inch,
modified by Trevithick, sen.; then the 63-inch double of Watt; and,
finally, the high-pressure engines of Trevithick, jun.; he saw the
open-top cylinders, atmospheric of Newcomen, in the Shammal 45-inch and
Wheal Gons 63-inch, with their wooden beams with segment-headed ends,
moving in rivalry with the Watt 63-inch double, with cylinder-cover
and parallel motion; he saw the two former engines, as altered by
Trevithick, jun., using the higher steam from the globular boiler on
which Henry Clark worked in 1799, when "there used to be great talking
about different boilers, and a boiler of Captain Trevithick's worked
with higher steam than the others; and the waggon boiler of Watt, that
had just been repaired, was discarded and cut up;" thus described by
Trevithick, "the fire-place is 22 feet from fire-door to fire-door, 9
feet wide, and 7 feet thick in fire,"[78] which he proposed to replace
in 1806 by a cylindrical boiler to give steam of 25 lbs. on the inch.
[Footnote 78: See Trevithick's letter, February 18th, 1806, vol. ii., p.
143.]
Pooly also saw the finishing stroke in 1811, when the boilers still
known as the Trevithick or Cornish boilers, gave steam to the three
engines; after a twelve years' fight between low and high pressure,
commencing with Trevithick's globular boiler and internal tube, in
Dolcoath, in the year 1799, from which time it gained step by step,
though in comparatively small engines, up to 1811, when the cylindrical
boilers took the place of the condemned hearse and globular boilers,
and gave really strong and expansive steam to the three Dolcoath
pumping engines that from time immemorial had been rivals, causing
all three of them to lift an increased quantity of water, and at the
same time to save one-half in the cost of coal; this continued for
four or five years, when in 1816 the 63-inch double and the 45-inch,
being the youngest and the oldest of the three, were removed, that a
new 76-inch cylinder, better adapted to Trevithick's expansive steam
might more cheaply perform their joint work. Prior to this change the
three engines were known by the names Shammal 45-inch, formerly Bullan
Garden,[79] but before that as Carloose, of the period and form of the
Pool engine;[80] Stray Park 63 single, formerly Wheal Gons,[81] dated
from 1770 to 1777; and the 63-inch double of Watt in 1780.
[Footnote 79: See vol. i., p. 25.]
[Footnote 80: See vol. i., p. 5.]
[Footnote 81: Query Bonze, spoken of by Smiles.]
"SIR,
"DOLCOATH MINE, _March 29th, 1858_.
"I have obtained the following information respecting the building
of the first cylindrical boilers, as ordered by your late father
for Dolcoath; and some information of the results as to the coals
consumed, compared with the consumption by the boilers previously in
use here.
"George Row, now about seventy-two years old, and working at Camborne
Vean Mine, says he assisted to build the two first cylindrical boilers
with internal tubes used in Cornwall. They were built in Dolcoath Mine
in the year 1811; they were 18 feet long, 5 feet diameter, having an
oval tube 3 feet 4 inches in the largest diameter at the fire end;
the other or chimney end of the tube was somewhat smaller. They were
found too small for the work to be done, and another boiler was built
immediately, 22 feet long, 6 feet 2 inches diameter, and he believed a
4-feet tube.
"John Bryant, now seventy-four years old, works a steam-engine at
West Wheal Francis. He worked at Dolcoath the 63-inch cylinder
double-acting engine, upon Boulton and Watt's plan. When he first
worked her she had the old bee-but boiler, 24 feet in diameter. They
were taken out for the Boulton and Watt waggon boiler, 22 feet long
and 8 feet wide, with two fire-doors opposite one another.
"Then the Boulton and Watt waggon was taken out for Captain
Trevithick's boilers, which he worked for several years. Two boilers
were put in, each 18 feet long, 5 feet diameter, with an internal oval
tube, he thinks, 3 feet by 2 feet 6 inches. Shortly after, another
boiler of similar form was added, 22 feet long, 6 feet diameter,
4-feet tube.
"He cannot say what the saving of coal was, but remembers that the
duty performed by the engine with the waggon boiler was thirteen to
fourteen millions. Mr. William West came to the mine as an engineer,
and by paying great attention increased the duty of the Boulton
and Watt engine and boiler to about fifteen millions. He does not
recollect the duty the engine performed with the cylindrical boilers.
"Mr. Thomas Lean, of Praze, the present reporter of mine engines in
the western part of Cornwall, in answer to a note I sent to him, says
he has no account of any report of Dolcoath engines for the _year
1812_, but during the month of April in that year the engines did
21-1/2 millions. During the whole of 1813 that engine was reported to
average a duty of twenty-one millions. The whole of the above are at
per bushel of 93 lbs., and the whole of the accounts furnished by Mr.
Lean are for Trevithick's cylindrical boilers.
"From the Dolcoath Mine books I find the following: Paid for coals for
the whole mine during the year 1811, 1150_l._ 15_s._ 10_d._, or per
month, 931_l._ 14_s._ 7_d._ During the first three months of 1812 the
coal averaged 1000_l._ per month. In May of this year, 1812, Captain
Trevithick is entered on the books as paid 40_l._ on account of
boilers; and in August of the same year, for erecting three boilers,
105_l._ I think the three boilers were at work in April, 1812, the
month Mr. Lean gives as the first reported. From April, 1812, to
December, during nine months, the cost of coals was 5512_l._ 6_s._,
averaging 612_l._ 9_s._ 6_d._ per month. During the next year, 1813,
the cost for coal was 7019_l._ 17_s._ 5_d._, or an average per month
of 590_l._ 16_s._ 5_d._ I cannot find the price paid per ton for the
coal in these years, but the average price during 1808 and 1815 was
much alike, making it probable that the price per ton during 1811,
1812, and 1813, was nearly the same; and that the saving of the above
300_l._ per month in Dolcoath was wholly on account of the saving
effected by Trevithick's cylindrical boilers.
"The testimony of John Bryant, that the duty with the waggon boiler
was say fourteen millions, and that of Mr. Lean, giving twenty-one
millions with the new Trevithick boiler, bear much the same proportion
as the charges for coals in the respective periods above given.
"In the year 1816 a new 76-inch single engine was erected in the place
of the old Boulton and Watt 63-inch double engine with Trevithick's
cylindrical boilers. The average duty performed during the year 1817
was 43-3/4 millions. This same engine is still at work, and her
regular duty is from thirty-six to thirty-eight millions.
"I am, Sir,
"Your most obedient servant,
"CHARLES THOMAS.
"FRANCIS TREVITHICK, Esq."
Captain Charles Thomas, who was one of the most experienced of Cornish
miners, for many years the manager of Dolcoath, and in youth the
acquaintance of Trevithick, states that the new high-pressure boilers
were made in the mine in 1811, and gave their first supplies of strong
steam to the three large pumping engines in April, 1812, with such good
effect that the increasing water which had threatened to drown the
mine was speedily removed, and that with a saving of nearly one-half
of the coal before consumed. Prior to their use Dolcoath Mine paid
1000_l._ monthly for coal; but for the latter nine months of the year,
in consequence of the new boilers, the cost was reduced to 612_l._ a
month. This saving in the pumping cost of one mine crowned with success
the high-pressure steam engineer, who had been steadily gaining ground
during his fight of twelve or fourteen years on the battle-ground
chosen by Watt thirty-three years before.
The low price of tin and copper, which caused so many engines to cease
working about the close of the last century, had changed for the
better, and the present century opened with an increasing demand for
steam power. Trevithick's high-pressure portable engines had worked
satisfactorily for several years; and as a means of making public the
relative duty performed by Cornish pumping engines, and of solving
conflicting statements on the rival systems of low and high pressure
steam, it was determined that an intelligent person should examine
and give printed monthly reports of the amount of duty done by the
different engines, and in 1810 Captain Andrew Vivian was requested
to take this work of engine reporter in hand; on his refusal it was
offered to Trevithick. In August, 1811, Mr. Lean commenced such monthly
reports, showing that the duty of twelve pumping engines at the end of
that year averaged seventeen millions, exactly the duty done by the
Boulton and Watt engines thirteen years before, as reported by Davies
Gilbert and Captain Jenkin in 1798, proving the small inherent vitality
of the Watt engine.
In 1814 the Dolcoath pumping engines, with Trevithick's cylindrical
boiler and high steam expansion, are thus reported:--"The Boulton
and Watt, Dolcoath great double engine, 63-inch cylinder, did a duty
of 21-1/2 millions; the Shammal 45-inch cylinder, single engine,
did 26-3/4 millions; and the 63-inch single, Stray Park engine, 32
millions." Shammal engine, nearly 100 years old, beat the Watt engine
of more than half a century later; and so did Stray Park 63-inch, which
Watt had laughed at when he first tried his hand as an engineer in
Cornwall in 1777.[82]
[Footnote 82: See vol. i., p. 30; vol. ii., p. 115.]
The marked change in these three engines, while for two or three years
under Trevithick's guidance, becoming more powerful and economical,
raised the usual swarm of detractors, and in 1815 a special trial was
made, which lasted for two days, to test the reported increased duty by
the cylindrical boilers and expansive working.
The unbelievers were then convinced, and agreed to throw out the
Boulton and Watt great double engine 63-inch cylinder, together with
its neighbour, the worn-out old 45-inch, and put in their stead one
engine with a cylinder of 76 inches in diameter, with expansive valve
and gear, and parts strong enough and suitable to the high-pressure
steam, on Trevithick's promise that it should do more than the combined
work of the other two with one-half the coal.
In 1816 this new engine commenced work, and did forty millions of
duty, increasing it during the next two or three years to forty-eight
millions, being three times the duty performed by the Watt 63-inch
double engine before it was supplied with steam from Trevithick's
boilers, and twice as much as it performed when so supplied. Lean
says, "This was the first instance of such duty having been performed
by an engine of that simple construction." The other mines followed
Trevithick's advice, but never paid him a penny. On this Lean again
says, "The engines at work in the county in 1835 would have consumed
80,000_l._ worth of coal over and above their actual consumption
yearly, but for the improvements that had been made since 1814."
Trevithick's engines were very durable, as well as cheap in first cost
and in working expense. This famous Dolcoath 76-inch engine remained
in constant work night and day for fifty-four years; after which good
service the steam-pipes, being thinned by rust, were held together by
bands and bolts; the steam-case around the cylinder would no longer
bear the pressure of steam; the interior of the cylinder from wear was
one inch larger in diameter than when first put in, and had to be held
together by strap-bolts. The original boilers were said to remain, only
they had been repaired until not an original plate remained; but there
they were in the old stoke-hole in 1869, when, from the fear of some
part of the engine breaking and causing accident, it was removed.
[Illustration: TREVITHICK'S DOLCOATH 76-INCH CYLINDER PUMPING
ENGINE, ERECTED IN 1816, CEASED WORKING 1869.
_a_, steam-cylinder, 76 inches in diameter, 9-feet stroke; _b_,
steam-jacket; _c_, steam expansion-valve, 11 inches diameter, double
beat; the upper beat 11 inches diameter, the under beat 9-1/2 inches,
valve 8 inches long; _d_, expansive cam on plug-rod; _e_, plug-rod
for moving the gear; _f_, expansive horn; _g_, equilibrium valve, 13
inches in diameter, single beat moved by a tooth-rack and segment; _h_,
exhaust-valve, 14-1/2 inches in diameter, single beat moved by a lever
and link; _i_, equilibrium-valve handle; _j_, exhaust-valve handle;
_k_, Y-posts for carrying the gear arbors; _l_, main beam in two plates
of cast iron; _m_, parallel motion; _n_, feed-pump rod; _o_, air-pump
bucket-rod, the pump, 2 feet 9 inches diameter; _p_, the main pump
rods.]
[Illustration: CYLINDER, MAIN BEAM, AND PUMP-ROD OF DOLCOATH
76-INCH CYLINDER ENGINE.]
In 1867 the writer was a member of the Dolcoath Managing Committee,
when it was determined that the old engine of 1816 should be replaced
by a new one. The cylinder sides were reduced in thickness by half an
inch; the steam-pipes and nozzles were thinned by rust and decay; the
valves and gear-work remained in good order. Captain Josiah Thomas, the
present manager of the mine, offered to sell this old engine at scrap
price, that it might be stored in the Patent Museum at Kensington as a
memento of the early high-pressure expansive steam pumping engine.
[Illustration: BOILERS ERECTED IN 1811 IN DOLCOATH, USED IN
THE BOULTON AND WATT 63-INCH ENGINE, THEN IN THE NEW 76-INCH UNTIL
1869.
_a a_, two wrought-iron cylindrical boilers, 5 feet in diameter, 18
feet long, with internal fire-tube, oval, 3 feet 4 inches by 3 feet;
_b_, a boiler, 6 feet 2 inches diameter, 22 feet long, cylindrical
tube, 4 feet diameter in the fire-place, the remainder 3 feet; _c_,
brick bridge; _d_, fire-bars; _e_, brick external flues under boiler;
_f_, brick side-flues; _g_, ashes, or other non-conductor; steam 30 to
50[**unclear] lbs. on the inch above the atmosphere.]
The steam-cylinder of 1816 was cast in South Wales; the beam still
working in the new engine of 1869 was cast in the foundry of the
Williams' at Perran. John West replaced the original flat expansive
steam-valve with a double-beat valve; the gear was principally made
by him on the mine, and remained in good working to the last. This
double-beat valve is the first the writer has met with; it is of the
same form as the modern double-beat valve; an earlier plan was to have
a small valve on the top of the main valve. The steam in ordinary
working was shut off when the piston had moved from an eighth to a
quarter of its stroke.
The Gons, or Stray Park 63-inch cylinder, survived its companions, the
63 double, and 45 single, for some ten or fifteen years, having beaten
both of them in duty. A memorandum in Trevithick's handwriting shows
that he in 1798, when designing his large globular boiler with internal
flue at the reworking of Dolcoath, tested the relative duty of the
Watt 63-inch double and the 63-inch single engine, then called Wheal
Gons, the latter in its original form of open-top cylinder atmospheric;
shortly after which it probably received a cover about the same time
as the 45-inch, for both those engines were thoroughly repaired by
Trevithick at the reworking of the mine, twelve or fourteen years prior
to the use of the cylindrical boilers.
"At the time that Boulton and Watt made their trial of Seal-hole
engine against Hornblower's engine at Tin Croft, the engines were put
in the best order, and good coals brought in for the purpose, to work
for twenty-four hours. The trial was attended by the principal mining
agents; the result was about ten millions by each engine.
"At Dolcoath Mine an old atmospheric engine continued to work for
several years by the side of one of Boulton and Watt's engines of the
same size; the water lifted and coals consumed were carefully taken
and made known to the public, showing that Boulton and Watt's engine
performed, when compared with the old engine, as 16 to 10."[83]
[Footnote 83: Memorandum in Trevithick's writing.]
Hornblower was an active engineer in Cornwall before Watt; the patent
of the latter claiming the sole right of working an engine by steam
in the cylinder,[84] drove the former to use two cylinders, in one
of which the expansion was carried out, as a means not described in
Watt's patent; a lawsuit was the consequence. The two engines when
tried by Trevithick[85] performed an equal duty of ten millions. In
1798 he tested the Dolcoath atmospheric 63-inch single against Watt's
great 63-inch double action. "The atmospheric performed ten millions,"
precisely the duty of the patent Watt and the patent Hornblower
contests of six years before; but the Watt Dolcoath engine, then
considered the best he had made, did sixteen millions. These trials in
1792 and 1798 enable us to compare the Newcomen, the Hornblower, and
the Watt engines; shortly after which Trevithick tried higher steam in
one or more of those same engines from his globular boiler.[86]
[Footnote 84: See vol. i., p. 46.]
[Footnote 85: See vol. i., p. 57.]
[Footnote 86: See vol. ii, p. 119.]
"SIR CH. HAWKINS, "CAMBORNE, _March 10th, 1812_.
"Sir,--This day I shall attend the account at Wheal Prosper Mine, in
Gwythian, to contract with the adventurers for erecting a steam-engine
on my improved plan, for drawing the water 50 fathoms under the adit.
I called on Wheal Liberty adventurers at St. Agnes last week, and
found that several of them had given up their shares rather than put
in a new engine, and the remainder of them very sick.
"I told them that I would fork the water with the present engine, and
draw instead of 40 gallons each stroke, 47 fathoms deep (which she
did), 85 gallons per stroke, 65 fathoms deep, by altering the engine
on the same principle as I have done with the Dolcoath great engine,
and several more that are now altering. The expense of altering the
engine, and forking the water to bottom, and proving the mine, will
not exceed 1000_l._
"All the adventurers are very anxious to again resume their shares and
make the trial, on condition that I will undertake the completion of
the job at a certain sum, but not otherwise.
"I am certain, from what Dolcoath engine is doing, that I can far
exceed the power above stated, and perform the duty with one-half
the coal the engine consumed before, and would not hesitate a moment
to engage the job on the terms they propose, but I have not money
sufficient to carry it into execution, as I must lay out a large sum
in erecting the engine on the Gwythian Mine, and unless I can be
assisted with 500_l._, shall not be able to undertake the job.
"If you think it worth your notice to encourage this undertaking by
lending me the above sum for six months, I will pay you interest for
it, and before drawing any part of it from you would get materials in
the mine that should amount to above that sum, and also give you an
order on the adventurers to repay you the whole sum before receiving
any part myself.
"As I have been a bankrupt, perhaps you may scruple on that account,
but that business is finally settled, and I have my certificate; and
indeed I never was in debt to any person; not one shilling of debt was
proved against me under the commission, nothing more than the private
debts of my swindling partner.
"At Wendron we are working an engine lately erected on a copper lode,
which has a very promising appearance, and near this spot you have
land at Besperson, where there is also a very kindly copper lode,
which deserves trial; if you are inclined to grant a sett, I think I
can find adventurers to join me to try the mine.
"I have lately read a letter from your hind, that the engine continues
to mend; it far exceeds my expectation. I am now building a portable
steam-whim, on the same plan, _to go itself_ from shaft to shaft; the
whole weight will be about 30 cwt., and the power equal to twenty-six
horses in twenty-four hours.
"The only difference in this engine and yours will be the fire in the
boiler, and without mason-work, on account of making it portable.
I shall pass the rope from the fly-wheel round the cage of the
horse-whim.
"If you should fall in with any West India planter that stands in
want of an engine, he may see this one at work in a month, which will
prove to him the advantage of a portable engine, to travel from one
plantation to another. The price, completely finished and set to work,
free of all expense, in London, 105_l._
"I am, Sir,
"Your very humble servant,
"RD. TREVITHICK.
"N.B.--Captain John Stephens informed me, a few days since, that the
lead mine at Newlyn was rich."
In Wheal Prosper Mine the first high-pressure expansive
steam-condensing pole-engine had been worked, just before the date of
the foregoing letter, and that evidence of increased power and economy
was immediately followed by the application of the same principles of
high-pressure steam and very expansive working to the Watt low-pressure
steam vacuum engines at Wheal Alfred, Dolcoath, and other mines,
with such satisfactory results as to warrant his offering, on the
battle-ground of his first attack on the Watt low-pressure steam vacuum
principle at Seal-hole in St. Agnes, fourteen years before,[87] at his
own pecuniary risk, to so apply those principles in the Wheal Liberty
low-pressure steam-engine, which had failed to drain the mine, lifting
only at the rate of 1880 gallons of water one fathom high at each
stroke; that it should lift an increased quantity of water, and that,
too, from an increased depth, making the load equal to 5525 gallons,
and to perform such increase of work with one-half of the quantity of
coal before used; in other words, he was willing to engage to make
the old low-pressure steam-engine perform by its conversion into a
high-pressure steam-engine threefold its original work, and also to
increase its duty or economic value sixfold; resting his argument on
the similar changes, then to be seen in operation at Wheal Alfred Mine,
and especially in the Watt 63-inch double-acting engine at Dolcoath,
whose history we have been tracing. Well might Sir Charles Hawkins
hesitate to believe what the experience of sixty years has barely
sufficed to make plain to us.
[Footnote 87: See vol. i., p. 90.]
"CAPTN. TREVITHICK, "PENZANCE, _March 27th, 1813_.
"Sir,--In consequence of the conversation that has passed between
you and West Wheal Tin Croft adventurers, the said adventurers have
resolved to put an engine on that mine, agreeable to the proposals
offered by you; that is, the engine shall be capable of lifting a
5-inch bucket, 50 fathoms, 4-feet stroke, 15 strokes per minute,
or a duty equal thereto; for which they will pay you 50 guineas one
month after the engine shall be at work, and 50 guineas more at four
months after that, and 50 guineas more at four months from that time,
making the full payment of 150 guineas in nine months from the time
the engine shall set at work, the adventurers paying all expense,
except the engine materials, which shall be delivered on the mine. But
in case the engine not performing the above duty, the adventurers to
be at liberty to return the same engine, and you to pay back all the
money that you had received for the said engine.
"Signed by GABL. BLEWETT,
"in behalf of the Adventurers and Company."
Trevithick was willing to spend more than his last penny in
establishing the superiority of his high-pressure steam expansive
engines, but the selfishness of adventurers retarded their progress.
The atmospheric, mentioned by Watt as working in Dolcoath in 1777,[88]
did five or six millions of duty, yet in Trevithick's hands, about 1798
to 1800, when he erected his globular boiler with internal tube, one
of them was tested with the 63-inch Watt low-pressure vacuum engine,
when the latter did sixteen millions to ten millions by the atmospheric
engine, being nearly double the duty it performed in its original form;
and we shall still trace this same engine as Bonze or Gons until it
increased to six times its first duty under the name of Stray Park
63-inch.
[Footnote 88: See vol. i., pp. 30, 57; vol. ii., p. 115.]
Trevithick having erected a high-pressure steam condensing whim-engine
at Cook's Kitchen,[89] and in Dolcoath[90] a high-pressure puffer
whim-engine, pleaded hard in 1806[91] to be allowed to supply the large
pumping engines of Newcomen and Watt with higher pressure steam from
his cylindrical boiler, which after years of consideration Dolcoath, in
1811, agreed to. In 1813 he wrote:--"That new engine you saw near the
sea-side with me is now lifting forty millions, one foot high, with one
bushel of coal, which is very nearly double the duty that is done by
any other engine in the county. A few days since I altered a 64-inch
cylinder engine at Wheal Alfred to the same plan, and I think she will
do equally as much duty. I have a notice to attend a mine meeting to
erect a new engine, equal in power to a 63-inch cylinder single."[92]
[Footnote 89: See vol. i., p. 91.]
[Footnote 90: See vol. i., p. 91.]
[Footnote 91: See vol. ii., p. 142.]
[Footnote 92: See Trevithick's letter, January 26th, 1813, vol. ii., p.
55.]
The beneficial results of those acts are too large to be here
entered into in detail. In round numbers, the early pumping engines
of Newcomen did five millions;[93] Trevithick caused them to do ten
millions of duty with a bushel of coal. Watt, during thirty years of
improvements, caused the duty to reach sixteen or twenty millions in
1800. Trevithick, on the expiry of the Watt patent, then came into
play, and before he had reigned half the time of Watt, again doubled
the duty of the steam-engine, as he states in 1813 "his new engine was
doing forty millions, being nearly double the duty of any other engine
in the county." These statements by Trevithick agree very nearly with
the generally-received accounts of the progressive duty of the large
pumping steam-engine.
[Footnote 93: See vol. i., p. 41.]
"In 1798 Davies Gilbert, Esq., and the late Captain Jenkin of
Treworgie, found the average of the Boulton and Watt engines in
Cornwall to be about seventeen millions. In August, 1811, the eight
engines reported averaged 15·7 millions. During the year 1814 Dolcoath
great engine, with a cylinder of 63 inches in diameter, did twenty-one
and a half millions nearly. Dolcoath Shammal engine, with a cylinder
of 45 inches in diameter, did twenty-six and three-quarter millions.
Dolcoath Stray Park engine, with a cylinder of 63 inches in diameter,
did thirty-two millions.
"In 1815 a trial was made, to prove the correctness of the monthly
reports. Stray Park engine at Dolcoath was chosen for the purpose,
because its reported duty was such as led some persons to entertain
doubts of its accuracy. The trial was continued for ten days, to the
full satisfaction of all concerned.
"In 1816, Jeffrie and Gribble erected a new engine, 76-inch cylinder,
single, at Dolcoath, which did forty millions. This was the first
instance of such duty having been performed by an engine of that
simple construction.
"In 1819, Dolcoath engine performed the best during this year, and at
one time reached forty-eight millions.
"In 1820, Treskerby engine, to which Trevithick's high-pressure pole
had been adapted, reached 40·3 millions.
"In 1816, Sims also erected an engine at Wheal Chance, to which he
applied the pole adopted by Trevithick in his high-pressure engines.
This engine attained to forty-five millions.
"In 1828 public attention had now been attracted to the improvements
which Captain Grose had introduced into his engine at Wheal Towan.
The duty of this engine, in the month of April this year, equalled
eighty-seven millions.
"This again gave rise to suspicions of error in the returns. This
engine was accordingly subjected to a trial (as Stray Park engine had
been in 1815), which was superintended and conducted by many of the
principal mine agents, engineers, and pitmen of other mines.
"The quantity of coal consumed in 1835, compared with the quantity
that would have been consumed by the same engines in the same time,
had they remained unimproved from the year 1814, shows that the saving
to the county amounts to 100,000 tons of coal, or 80,000_l._ sterling
per annum."[94]
[Footnote 94: Lean's 'Steam-Engine in Cornwall.']
Lean seems to have calculated on a bushel of coal as 94 lbs. In 1798,
when Trevithick was about to give increased pressure of steam to the
Cornish engines, his friend Davies Gilbert reported the average duty of
the Watt engine in Cornwall to be seventeen millions.
In August, 1811, the reported duty averaged 15·7 millions. This was
the month and year in which Trevithick, after twelve years of working
evidences of the reasonableness of his promises of increased power
and economy from using high-pressure steam, was allowed to erect his
cylindrical boilers for the large pumping engines in Dolcoath Mine.
Has the reader realized that the 45-inch atmospheric Carloose engine,
of nearly 100 years before,[95] had in 1775[96] become the Bullan Garden
engine of Trevithick, sen., which was improved and re-erected by
Trevithick, jun., in 1799,[97] when the name was again changed, this
time to Shammal, because it was linked to another engine, no other than
the Watt 63-inch double engine? This Shammal 45-inch took steam from
the globular boiler, using a pole air-pump[98] and a Watt condenser,
though retaining the beam with the arched head and chain connection;
and again in 1811 took still more highly expansive steam from the
cylindrical boilers with a new beam and parallel motion, enabling it in
1814 to beat its rival, the Watt Dolcoath great double engine.[99] The
old 63-inch Gons, under the name of Dolcoath Stray Park engine, with
Trevithick's improvements, did sixty-seven per cent. more work than the
Watt 63-inch with an equal quantity of coal.
[Footnote 95: See vol. i., p. 21.]
[Footnote 96: See vol. i., p. 25.]
[Footnote 97: See vol. ii., p. 120.]
[Footnote 98: See vol. ii., p. 122.]
[Footnote 99: See Lean's report, vol. ii., p. 175.]
This startling fact was disbelieved by the advocates of low-pressure
steam, and as the visible change in the Dolcoath engine from Newcomen
to Watt, and from Watt to Trevithick, had been gradual and not very
striking, and the public were careless of principles, the one most
puffed was most thought of; but the money saved was tangible, and in
1815 a special trial was made, which lasted two days, to discover if it
was really true that Trevithick's appliances could so increase the duty
of the engine. The 63-inch cylinder, then called Stray Park engine,
was selected; the result proved that the large saving reported from
Trevithick's boilers and expansive working during the last three or
four years, was an incontrovertible fact.
The high-pressure steam was also given to the defeated Watt 63-inch
double engine; yet this newest of the three engines was the first to be
condemned, and her place was taken in 1816 by an engine of 76 inches in
diameter, which Trevithick promised should, with his high steam and new
expansive gear, do the work of the Watt 63-inch and the old 45-inch put
together; which was more than fulfilled by its doing forty millions,
and, as Lean says, "was the first instance of such duty having been
performed by an engine of that simple construction."
In 1819 the new 76-inch engine which had been erected by the mine
engineers, Jeffrie[100] and Gribble, who had long been employed by
Trevithick in Dolcoath, was the best in the county, doing forty-eight
millions, nearly three times the duty as given by Mr. Gilbert for the
Watt engine in 1798. In 1827 Trevithick's pupil, Captain Samuel Grose,
erected his Wheal Towan engine, which performed a duty of eighty-seven
millions, some of the working drawings of which were made by the
writer. In 1835 the principle laid down by Trevithick had become so
general in the county as to cause a saving to the Cornish mines, in
coal alone, of 80,000_l._ yearly. In addition to this, the increased
power of the engine lessened the first cost by at least one-half.
[Footnote 100: See vol. i., p. 106.]
The national importance of such weighty facts calls for further
corroborative proof, for we can scarcely believe that two atmospheric
low-pressure steam-engines, made before the time of Watt, could be
altered so as to perform more work, and at a less cost than the
Watt engine, by an ingenious supply of higher steam pressure from
Trevithick's boilers, together with the Watt air-pump and condenser.
The following words from Watt are descriptive of his practice, though
contrary to his patent claim:--
"At a very early period, while experimenting at Kinneil, he had formed
the idea of working steam expansively, and altered his model from
time to time with that object. Boulton had taken up and continued the
experiments at Soho, believing the principle to be sound, and that
great economy would attend its adoption.
"The early engines were accordingly made so that the steam might be
cut off before the piston had made its full stroke, and expand within
the cylinder, the heat outside it being maintained by the expedient of
the steam-case. But it was shortly found that this method of working
was beyond the capacity of the average enginemen of that day, and it
was consequently given up for a time.
"'We used to send out,' said Watt to Robert Hart, 'a cylinder of
double the size wanted, and cut off the steam at half-stroke.'
"This was a great saving of steam, so long as the valves remained as
at first; but when our men left her to the charge of the person who
was to keep her, he began to make, or try to make, improvements, often
by giving more steam. The engine did more work while the steam lasted,
but the boiler could not keep up the demand. Then complaints came of
want of steam, and we had to send a man down to see what was wrong.
"This was so expensive, that we resolved to give up the expansion of
the steam until we could get men that could work it, as a few tons of
coal per year was less expensive than having the work stopped. In some
of the mines a few hours' stoppage was a serious matter, as it would
cost the proprietor as much as 70l. per hour."[101]
[Footnote 101: Smiles' 'Lives of Boulton and Watt,' p. 228.]
Pole expresses the same view, intimating that Watt only used steam of 1
or 2 lbs. pressure to the inch.
"In Watt's engine, as is well known, the pressure of steam in the
boiler very little exceeded the pressure of the atmosphere. He
recommended that when the engine was underloaded, this excess should
be equal to about 1 inch of mercury; and when full loaded, ought not
to exceed 2 inches; adding, 'It is never advisable to work with a
strong steam when it can be avoided, as it increases the leakages of
the boiler and joints of the steam-case, and answers no good end.'[102]
[Footnote 102: Appendix A to Tredgold, 'Pole on Cornish Engines,' p. 49.]
"Mr. Watt's engines with such boilers" (which will not retain steam of
more than 3-1/6 lbs. per square inch above the atmosphere) "cannot be
made to exert a competent power to drain deep mines, unless the supply
of steam to the cylinder is continued until the piston has run through
more than half its course.[103]
[Footnote 103: 'Phil. Mag. and Annals,' N.S., vol. viii., p.
309, by W. J. Henwood.]
"In 1801-2 Captain Trevithick erected a high-pressure engine of small
size at Marazion, which was worked by steam of at least 30 lbs. on
the square inch above atmospheric pressure. In 1804, as Mr. Farey
admits,[104] the same gentleman introduced his celebrated and valuable
wrought-iron cylindrical boilers,[105] now universally used in this
county.
[Footnote 104: Ibid., p. 313.]
[Footnote 105: Ibid., vol. i., p. 127.]
"To these, everyone at all acquainted with the Cornish improvements
ascribes a great part of the saving we have obtained. This will
farther appear from an extract from a valuable work edited by John
Taylor, Esq., F.R.S.[106]
[Footnote 106: 'Records of Mining,' p. 163.]
"The monthly consumption of coal in Dolcoath Mine was, in 1811, 6912
bushels; in 1812, 4752 bushels.[107] The alteration in the boilers was
the introduction of Captain Trevithick's cylindrical boilers in the
place of the common waggon boilers, which had until then been there in
use.
[Footnote 107: Alteration in the boilers that year.]
"Mr. Woolf, as Mr. Farey states, came to reside in Cornwall about the
year 1813, and his 'first engines for pumping water from mines were
set up by him in 1814.'"[108]
[Footnote 108: 'Phil. Mag. and Annals,' vol. x., p. 97, "Notes on Some
Recent Improvements of the Steam-Engine in Cornwall," by W. Jory
Henwood, F.G.S.]
The foregoing was read at the Philosophical Society in 1831, to refute
erroneous statements on the Watt and Trevithick engines. My friend
Mr. Henwood had at that time made official experiments in conjunction
with Mr. John Rennie on the detail, working, and duty of high-pressure
steam Cornish engines, the Watt low-pressure steam principle having
been wholly given up. Rees's 'Cyclopædia'[109] also bears the following
similar testimony to date of the increased duty:--
[Footnote 109: See Rees 'On the Steam-Engine,' published 1819.]
"Trevithick's high-pressure engine was erected in Wales in 1804 to
ascertain its powers to raise water. The duty was seventeen millions
and a half pounds raised one foot high for each bushel of coals.
"The high-pressure steam-engines require a greater quantity of coals,
in proportion to the force exerted, than the engine of Mr. Watt, and
consequently are not worked with advantage in a situation where coals
are dear.
"From the reports of the engines now working in the mines of Cornwall,
which, with the exception of a few of Woolf's engines, are all on Mr.
Watt's principle, and most of them constructed by Messrs. Boulton and
Watt, taking the average of nine engines--bad, good, and indifferent
together--they were found in August, 1811, to raise only thirteen
millions and a half. But when it was known by the engine keepers
that their engines were under examination, they took so much pains
to improve the effects, that by gradual increase the engines in
1815 lifted twenty-one millions and a half, taking the average of
thirty-three engines. In 1816, Stray Park, a 63-inch cylinder, 7 feet
9 inches stroke, single-acting, being one of the three engines on
the vast Dolcoath Mine; its performance in four different months was
thirty-one, thirty-one and a quarter, twenty-eight, and twenty-eight
and a half millions."
This statement reveals a source of error in estimating the relative
values of the Watt and the Trevithick engine; that of the latter was
the Welsh locomotive, compared in duty with the large Watt pumping
engine, pointed out in Trevithick's letter[110] of that time, as an
unfair comparison; the small high-pressure puffer, in 1804, is admitted
to have done seventeen and a half millions of duty with a bushel of
coal of 84 lbs., while in Rees' calculation of the engines, he gives
Watt 94 lbs. of coal to a bushel; and having stated that the Watt
pumping engines in Cornwall, in 1811, averaged but thirteen and a half
millions of duty, draws the false conclusion that the high-pressure
cannot compete with the low-pressure where coals are dear; yet he
agrees with other writers that the great increase in the duty of the
Cornish pumping engines commenced from 1811 (when Trevithick first
gave them his high-pressure steam); and states that in 1816 the Stray
Park 63-inch cylinder single-acting engine,[111] being one of three then
working in Dolcoath, did thirty-one millions.
[Footnote 110: See vol. i., p. 166.]
[Footnote 111: See Watt's statement, vol. ii., p. 115.]
The 'Encyclopædia Britannica' on the question of duty states:[112]--
[Footnote 112: See "Steam-Engine," published 1860.]
"The duty of the best of Smeaton's engines was, in 1772, 9,450,000
foot pounds per cwt. of coal. On the expiration of Watt's patent,
about the year 1800, the highest duty of his engines amounted to
twenty millions, or more than double the former duty, which may
represent the economical value of the improvement effected by Watt
under his various patents.
"The reported duty of Cornish pumping engines, by the consumption of
94 lbs. of coals, rose from an average of nineteen millions and a
half, and a maximum of twenty-six millions in 1813, to an average of
sixty millions and a maximum of ninety-six millions in 1843. It is
necessary to bear in mind the distinction between the duty of a bushel
of coal and 112 lbs."
Here, also, are the same general facts as to the duty of the Watt
engine, and the marked and rapid increase of duty dating from
Trevithick's Dolcoath engines in 1811; but the confusion and even
contradictions in the statements prove how little the subject was
understood.
"A rough draft, prepared by Mr. Edmonds on Trevithick's return from
America, dated 1828, for an application to Parliament for remuneration
to Trevithick, says, 'That this kingdom is indebted to your petitioner
for some of the most important improvements that have been made in the
steam-engine.
"'That the duty performed by Messrs. Boulton and Watt's improved
steam-engines in 1798, as appears by a statement made by Davies
Gilbert, Esq., and other gentlemen associated for that purpose,
averaged only fourteen millions and a half (pounds of water lifted 1
foot high by 1 bushel of coal), although a chosen engine of theirs
under the most favourable circumstances lifted twenty-seven millions,
which was the greatest duty ever performed till your petitioner's
improvements were adopted, since which the greatest duty ever
performed has been sixty-seven millions, being much more than double
the former duty. That, prior to the invention of your petitioner's
boiler, the most striking defect observable in every steam-engine was
in the form of the boiler, which in shape resembled a tilted waggon,
the fire being applied under it, and the whole being surrounded with
mason work. That such shaped boilers were incapable of supporting
steam of a high pressure or temperature, and did not admit so much of
the water to the action of the fire as your petitioner's boiler does,
and were also in other respects attended with many disadvantages.
That your petitioner's invention consists principally in introducing
the fire into the midst of the boiler, and in making the boiler of a
cylindrical form, which is the form best adapted for sustaining the
pressure of high steam.
"'That the following very important advantages are derived from this
your petitioner's invention. This boiler does not require half of the
materials, nor does it occupy half the space required for any other
boiler. No mason work is necessary to encircle the boiler.[**'"]
"'That, had it not been for this your petitioner's invention, those
late vast improvements which have been made in the use of steam
could not have taken place, inasmuch as none of the old boilers
could have withstood a pressure of above 6 lbs. to the inch beyond
the atmosphere, much less a pressure of 60 lbs. to the inch, and is
capable of standing a pressure of above 150 lbs. to the inch.'"
Trevithick's retrospect views of 1828 are supported by the letter of
the late Michael Williams, M.P., the most experienced of Cornish mine
workers, but belonging to the eastern district that had been for many
years the users of the Watt engines in Cornwall.
"In reference to his great improvements in the steam-engine, I have a
more particular recollection, and can confidently affirm that he was
the first to introduce the high-pressure principle of working, thus
establishing a way to the present high state of efficiency of the
steam-engine, and forming a new era in the history of steam power. To
the use of high-pressure steam, in conjunction with the cylindrical
boilers, also invented by Mr. Trevithick, I have no hesitation in
saying that the greatly-increased duty of our Cornish pumping engines,
since the time of Watt, is mainly owing; and when it is recollected
that the working power now attained amounts to double or treble that
of the old Boulton and Watt engine, it will be at once seen that it is
impossible to overestimate the benefit conferred, either directly or
indirectly, by the late Mr. Trevithick on the mines of this county.
I have often expressed my opinion that he was at the same time the
greatest and the worst-used man in the county."[113]
[Footnote 113: See letter of Michael Williams, chap. xix.]
The late Sir John Rennie and other scientific persons were, about 1830,
associated with Mr. Henwood[114] in examining the work performed by
Cornish pumping engines: their reports are curtailed in the following
comments on Wheal Towan engine, similar to Trevithick's Dolcoath engine
of 1816, except perhaps that the last named was a little inferior
in its detail movements, while much less care was taken to avoid
unnecessary loss of heat.
[Footnote 114: Henwood, 'Edinburgh Journal of Science,' 10.]
[Illustration: STEAM DIAGRAM OF WHEAL TOWAN PUMPING ENGINE, ERECTED
1827.]
Mr. Henwood also gave indicator diagrams of the expansion of the steam,
on one of which the writer has marked ten horizontal lines, indicating
the position of the piston at each foot of its stroke, and ten
longitudinal lines dividing the diameter of the cylinder into tenths.
The steam pressure in the boiler was 46·8 lbs. on the square inch
above the atmosphere, or 4·68 lbs. for each of the ten longitudinal
line divisions. _x_ to _c_ represents the top of the steam-cylinder 80
inches, diameter; _x_ to F the length of the cylinder for a 10-feet
stroke of the piston. By the time the piston had moved through
one-twentieth of its course, reaching _c_, the expansive working had
commenced; and when one-tenth of the stroke had been run, half of a
division was cut off, showing by the curved indicator line the decrease
in pressure of steam to 44.46 lbs. The comparatively small passage
through the steam-valve not giving room for sufficient steam to follow
up the increasing speed of the piston, led to its continued expansion
in the cylinder, and by the time the piston had moved 2 feet, reaching
D, the steam pressure was reduced by two divisions or 9.36 lbs., or a
pressure of 37.44 lbs. on the piston; at this point the steam-valve was
closed, and the remaining four-fifths of the stroke was performed by
expansion; at the fifth horizontal line, or middle of the stroke, only
three divisions of steam are left, giving a pressure of 14.04 lbs. to
the inch; at the finish of the stroke there is only half a division,
from E to F, or 2.34 lbs. of steam to the inch above the pressure of
the atmosphere. On the return up-stroke of the piston, when it had
reached within a foot of the finish of its course at C, the equilibrium
valve closed, causing the enclosed steam of 2.34 lbs. to the inch to
be compressed at the finish of the up-stroke shown by the curve G A to
9.36 lbs. on the inch, equal to its pressure about the middle of the
down-stroke at N.
Trevithick's expansive engine therefore, commencing its work with
steam of 46.8 lbs. on the inch above the atmosphere, only took a full
supply from the boiler during one-tenth of its stroke, and none after
one-fifth had been performed, while at the finish of the stroke it had
about the same pressure as Watt began with.
The _power_ of the Watt low-pressure steam vacuum pumping engine was
increased by Trevithick from two to three fold, and its economical
duty in about the same proportion; in other words, he increased
the effective power of the steam-engine two or three fold without
additional consumption of coal.
In the Wheal Towan engine the steam-cylinder was 80 inches in diameter,
with a 10-feet stroke. The shaft was 900 feet in depth; the main pumps
16 inches in diameter; the pump-rods were of wood, about 14 inches
square, and weighed more than the column of water in the pipes. The
boilers were Trevithick's cylindrical with internal tube, wholly of
wrought iron. The cylinder and steam-pipes were surrounded with sawdust
about 20 inches in thickness, as a non-conductor of heat. The upper
surfaces of the boilers were covered with a layer of ashes for the same
purpose. The duty performed was 86·58 millions of pounds of water,
raised one foot high by the consumption of a bushel of coal weighing 84
lbs. The immense power and economy of this engine are best understood
by its average labour costing only one farthing in coal for lifting
1000 tons one foot high.
At or about that time an old intimate of Trevithick's, Captain Nicholas
Vivian, managed the mine, and Mr. Neville, a shareholder, also a
user of steam-engines in Wales, observing the economical working of
Wheal Towan high-pressure steam expansive engine, doing eighty-seven
millions, requested its manager to examine colliery engines, all
of which were of the low-pressure kind; one of them was a Newcomen
atmospheric, whose duty was six millions; four or five others were Watt
low-pressure steam vacuum engines, doing fourteen millions; therefore
the high-pressure steam-engine did six times as much work with a bucket
of coal as the low-pressure steam vacuum, and fourteen times as much as
the low-pressure steam atmospheric engine. Several competitive trials
by the county engineers were published about that time, in one of
which, after a personal examination of the engine, Mr. W. J. Henwood[115]
and others reported a duty of 92·6 millions with a 91-lb. bushel of
coal.[116]
[Footnote 115: Address, Royal Institution of Cornwall, by W. J. Henwood,
1871.]
[Footnote 116: Trevithick calculated 84 lbs. to a bushel; Watt generally
112 lbs.; Lean 94 lbs., but latterly 112 lbs.]
Mr. Rennie had been a pupil, a fellow-worker with low-pressure Watt,
and while his son, Sir John Rennie, was examining the high-pressure
steam expansive engine erected by Trevithick's pupil, Captain Samuel
Grose, under the management of Trevithick's friend, Captain Nicholas
Vivian, the latter was engaged in reporting on certain low-pressure
steam-engines in Wales, one of which was a Newcomen's atmospheric,
probably the last of its race, whose principle of construction was a
century old, working in company with the Watt low-pressure steam vacuum
engine, then half a century old, the principles of both systems being
on their last legs, and under the care of Trevithick's supporters.
During this jumble of engines, old and new, without a clear
comprehension of their differences in principle, Trevithick, who had
just returned from America, and lived within a few miles of Wheal
Towan, looked on unconsulted and unconcerned on questions which in
his mind had been settled by him in Dolcoath fifteen or twenty years
before. The writer, during the Wheal Towan controversy, was the daily
companion of Trevithick, and made drawings of the engine at the works
of Harvey and Co., of Hayle, where it was constructed about 1827.
Captain Samuel Grose's Wheal Towan engine was in general character
similar to his teacher's Dolcoath 76-inch engine of 1816, working with
about the same steam pressure and degree of expansion. The valves,
gear, and nozzles were perhaps improved in detail; but the groundwork
was unchanged. The first high-pressure steam Cornish pumping engine
made in France was designed and superintended by the writer at the
works of Messrs. Perrier, Edwards, and Chaper, at Pompe-à-feu, in
Chaillot, a suburb of Paris. The principle was the same as the Dolcoath
engine, and the detail differed but little from it or the Wheal
Towan, except that its exterior was a little more artistic than its
prototypes in Cornwall, in keeping with French requirements. It was
built in 1836, within a few yards of the low-pressure steam pumping
engine erected by Perrier and others in 1779, which still continued
pumping water from the Seine for the supply of Paris. Stuart says,
"An engine by Boulton and Watt was sent to France, and erected by M.
Perrier at Chaillot, near Paris. The French engineer, Proney, with a
detestable illiberality, attributes all the merit of the improvements
in the Chaillot engine to his friend Perrier, the person who merely put
together the pieces he had brought from Soho."[117]
[Footnote 117: Stuart 'On the Steam-Engine,' p. 141.]
The Perrier of 1779 was related to the Perrier of the Pompe-à-feu
engine-building works of 1836, and his nephew took the Trevithick
engine from Paris to a coal mine not far from Brussels, but not fully
understanding the use of the balance-bob--the woodwork for which had
not been completed in Paris, though all other parts had been fully
erected--did not find it easy to manage the engine. The writer viewed
Perrier's move as an infringement of the agreement between him and
Edwards, the partner of Perrier and Chaper, and therefore declined to
take any further interest in the engine.
Mr. Edwards had before that been a partner with Woolf, in a small
engineering works in Lambeth; and the writer had also before that been
a pupil of Woolf's, in the works of Messrs. Harvey and Co., of Hayle.
The drawing of 'La Belle Machine' (Plate XIII.), of 1836, serves not
only as a record of that time, but also in conjunction with the drawing
of Dolcoath engine of 1816, enables an engineer to form a sufficiently
correct idea of the Wheal Towan engine and boilers of 1827, which in
effective duty is scarcely excelled by the best pumping engines of the
present day.
The events connected with those Paris engines bring together the
engineering works of Watt, Proney, Perrier, Trevithick, and Woolf, in
the person of his once partner, Edwards. The writer, when constructing
'La Belle Machine,' had not the slightest knowledge of those links, and
heard the name and repute of his engine by the following chance:--
In 1838 a passenger leaving the train of the Great Western Railway
at Drayton Station, asked the writer's permission to walk on the
line and examine its construction. During a short conversation he
mentioned the having purchased at a sale in France the drawings of
an engine known as 'La Belle Machine,' representing the Cornish
high-pressure expansive steam pumping engine:--_a_, steam-cylinder, 48
inches in diameter, 8-feet stroke; _b_, steam-pipe from boiler; _c_,
regulating steam-valve, double beat; _d_, regulating rod and handle for
steam-valve; _e_, expansive steam-valve, double beat; _f_, balanced
lever and rod for opening expansive valve; _g_, expansive clamp on
plug-rod, with regulating rod and thumb-screws; _h_, cataract-rod for
relieving expansive valve-catch; _i_, quadrant relieving the catch;
_j_, plug-rod; _k_, equilibrium valve, double beat; _l_, clamp in
plug-rod to close equilibrium valve by its action on the handle; _m_,
balanced lever and rod to open equilibrium valve; _n_, quadrant and
catch relieving equilibrium valve by the action of cataract-rod; _o_,
regulating slide on cataract-rod; _p_, equilibrium steam-pipe conveying
steam from the top to the bottom of the piston; _q_, exhaust-valve,
double beat; _r_, clamp on plug-rod, closing the exhaust-valve by
its descent on the handle; _s_, balance lever and rod, opening
exhaust-valve; _t_, quadrant and catch, relieving equilibrium valve
by the action of cataract-rod; _u_, regulating slide on cataract-rod;
_v_, exhaust-pipe to condenser; _w_, Y-posts for carrying the gear.
The steam in the boiler was from 40 lbs. to 50 lbs. on the square inch
above the atmosphere.
[Illustration: PLATE 13.
LA BELLE MACHINE. HIGH PRESSURE STEAM EXPANSION PUMPING ENGINE.--1836.
London: E.& F N. Span. 48, Charing Cross. Kell. Bro^s. Lith. London.]
Lean states that had the pumping engines at work in Cornwall in 1835
remained unimproved since 1814, at which time they had benefited by
three years of continuous improvement, a yearly additional expenditure
of 80,000_l._ for coal would have been the consequence, and that the
first step was Trevithick's expansive steam from the cylindrical
tubular boiler, engines using such steam performing a duty three or
four fold what Boulton and Watt had ever attained, or perhaps thought
possible of attainment.[118] The birth of the idea of using expansive
steam may in truth be traced back nearly one hundred years to the time
of Newcomen's atmospheric engine, and the hope expressed in 1746 of
a smaller boiler and more elastic steam[119] was partially realized in
the engine and boiler of Trevithick, sen., in Bullan Garden in 1775,
followed in 1780 by the competing engine erected by Watt in Dolcoath
Mine, under Trevithick's management. Little further change was made
until 1799, when the globular boiler and internal tube of Trevithick,
jun., gave a second start to the use in large engines of more expansive
steam; and even this partial move was the result of years of thought
and practical experiment; for in 1792, when twenty-one years of age, he
was the elected judge on a competitive trial between the Watt engine at
Seal-hole, patented in 1782, and Hornblower's double-cylinder engine at
Tin Croft. Each engine performed a duty of ten millions, both of them
were called expansive, while in fact neither of them were so, for the
pressure of the steam in the boiler did not admit of it. As Lean says,
"As the steam used was raised but little above the pressure of the
atmosphere, it was found that the power gained did not compensate for
the inconvenience of a more complicated and more expensive machine."
Or, as Watt said to Robert Hart, "We resolved to give up the expansion
of the steam until we could get men that could work it," as he found
it more costly than profitable. Again in 1798, Trevithick's own
writing records his experiment in Dolcoath between the Bullan Garden
45-inch atmospheric engine and the Watt 63-inch great double-acting
engine, when the latter did sixteen millions to ten millions by the
atmospheric. At that very time he was constructing his high-pressure
steam portable engines, and in the following year, after seven years of
most active experience, prompted by the Watt lawsuit against Cornish
engineers, he in 1799 gave the beaten 45-inch engine steam of a higher
pressure from the stronger globular boiler. People, following the
ideas of Watt, were still afraid of Trevithick's plans, distinctly
laid down in his letters of 1806, recommending a cylindrical boiler
for the Dolcoath pumping engine, because similar boilers giving steam
to his whim-engines have enabled them to beat the Watt whims. This
continued until 1810, when the greatly-increased power and economy
of the high-pressure expansive steam pumping engine at Wheal Prosper
caused the neighbouring Dolcoath in 1811 to give Trevithick's plans
free scope. The long smouldering rivalry between low and high pressure,
on the eve of the final discomfiture of the former, burst forth in
loud words and evil prognostications, causing the mining interest of
Cornwall to appoint an examiner who should publish monthly the duty
performed by the various pumping engines, the first of which appeared
in the autumn of 1811, when Trevithick was building his boilers in
Dolcoath, and preparing the engines, as far as was possible, to submit
to strong steam. By expansive valves and suitable gear, balance of
power between the engine and the pump-work necessitating balance-bobs,
strengthening the pit-work to bear the more powerful and sudden
movement, and fifty other things, which we know must have presented
themselves in such work, occupied the greater part of Trevithick's time
from 1811 to 1814. That first report enumerates twelve pumping-engines,
probably all of them Watt engines, averaging a duty of seventeen
millions.
[Footnote 118: See Lean's Historical Statement, p. 154; published 1839.]
[Footnote 119: See vol. i., p. 7.]
We have before traced the rapid and immense increase in the power and
in the duty of Cornish pumping engines from 1811, and it may be taken
as comparatively true in the larger sense applying to the improvement
of the steam-engine everywhere.
Dolcoath Mine, one hundred years ago, under the management of
Trevithick, sen., followed by his son as the strong-steam engineer, and
by his grandson as one of the committee of management in these modern
times, has served during that long period to illustrate the progress of
the steam-engine, and still in active operation, was thus spoken of in
'The Times' of Dec. 18th, 1871:--"This old and extraordinary mine is
now raising about 100 tons of tin every month, worth from 8000_l._ to
9000_l._"