THE WATT AND THE TREVITHICK ENGINES AT DOLCOATH.
Having up to 1816 traced the progress of the steam-engine in Cornwall
through a century, during the latter half of which Trevithick, sen.,
and his son were among its most prominent improvers, the latter
having devoted a quarter of a century to the work, the effect of
which is shown in the skeleton outlines of a few classes of engines,
one important feature still remains for examination before a correct
judgment can be formed of the events of this period and their prime
movers.
The use of an increasing pressure of steam gave increased force and
value to the improved steam-engine, but the power of constructing
engines and boilers to render the increased pressure manageable was the
result of a lifetime of labour.
Savery, whose engine was scarcely more than a steam-boiler, failed
to control its force, and is said to have blown the roof from over
his head. The mechanism of Newcomen's engine was well arranged, but
suitable only for the working of pumps, and its power was limited to
the weight of the atmosphere, from which it was called the atmospheric
engine.
In 1756, an atmospheric engine with a cylinder of 70 inches in diameter
worked at the Herland Mine, "the only objection to which was the cost
of the coal, to lessen which several methods had been suggested for
increasing the elasticity of the steam, and reducing the size of the
boiler."[47]
[Footnote 47: Borlase's 'Natural History of Cornwall.']
In 1775 Richard Trevithick, sen., removed the flat top of a Newcomen
boiler, and substituted a semicircular top, enabling it to contain
stronger steam, and at the same time he improved the mechanical part
of the engine by finding a better resting-place for the steam-cylinder
than the top of the large boiler. Pryce gives a drawing of this engine
as the best at that time in Cornwall.[48]
[Footnote 48: See drawing, vol. i., p. 25.]
"It is known as a fact that every engine of magnitude consumes
3000_l._ worth of coal every year.
"The fire-place has been diminished and enlarged again. The flame
has been carried round from the bottom of the boiler in a spiral
direction, and conveyed through the body of the water in a tube (one,
two, or three) before its arrival at the chimney.
"Some have used a double boiler, so that fire might act on every
possible point of contact, and some have built a moorstone boiler,
heated by three tubes of flame passing through it.
"A judicious engineer does not attempt to load his engine with a
column of water heavier than 7 lbs. on each square inch of the
piston."[49]
[Footnote 49: See Pryce's 'Mineralogia Cornubiensis,' published 1778.
Appendix.]
While Pryce's book was being printed, Watt in 1777 wrote of the Cornish
steam-engines:--
"I have seen five of Bonze's engines, but was far from seeing the
wonders promised. They were 60, 63, and 70 inch cylinders at Dolcoath
and Wheal Chance. They are said to use each about 130 bushels of coals
in the twenty-four hours, and to make about six or seven strokes per
minute, the stroke being under 6 feet each. They are burdened to 6,
6-1/2, and 7 lbs. per inch."[50]
[Footnote 50: Smiles' 'Lives of Boulton and Watt.']
The 63-inch was an open-top cylinder atmospheric engine at Dolcoath
Mine under the management of Trevithick, sen.; and shortly after, in
1777 or 1778, Watt's first engine was erected in Cornwall.[51]
[Footnote 51: See vol. i., p. 30.]
In 1783 Trevithick, sen., gave Watt an order for a patent engine for
Dolcoath, in size similar to the old Newcomen atmospheric, having a
cylinder 63 inches in diameter, that a working trial might be made
between the rival engines. The Watt engine having a cylinder-cover,
with the patent air-pump and condenser, was known in the county as the
Dolcoath great 63-inch double-acting engine. Three steam-engines were
then at work in that mine: Trevithick senior's Carloose (then called
Bullan Garden) atmospheric 45-inch cylinder, the atmospheric 63-inch
cylinder, and Watt's 63-inch cylinder double-acting vacuum engine; all
of which continued in operation side by side for five years until 1788,
when for a time Dolcoath ceased to be an active mine. Trevithick, jun.,
was then a boy of seventeen years.
After ten years of idleness and rust, as if mourning the death of
Trevithick, sen., in 1798 Richard Trevithick, jun., as engineer, and
Andrew Vivian as manager, induced shareholders to resuscitate the old
mine. Fire was again given to the voracious jaws of the boilers, and
the three engines recommenced their labours and their rivalries.
A year or two before this Trevithick had made models of high-pressure
steam-engines. Davies Gilbert, in 1796, met him among other engineers,
giving evidence in the Watt lawsuits, when he mentioned his ideas of
an engine to be worked solely by the force of steam. Watt had claimed
such an engine in his patent twenty-seven years before, but had failed
to carry it into practice. Hornblower had tried something like it in
his double-cylinder expansion engine, but he did not use high-pressure
steam, and consequently also failed.
The _idea_, therefore, of expansive steam was not new, but the _useful
mastery_ of it was. Savery had tried expansive steam before Watt
patented it; the latter went to law with Hornblower for an infringement
of the _idea_, when neither of them had in truth constructed an
expansive steam-engine. The low pressure of the steam from the boilers
used by Hornblower and Watt did not admit of profitable expansion
in the cylinder; at its full boiler pressure it constituted but a
comparatively small portion of the power of the engine: to reduce that
power by expansion was as apt to be a loss as a gain. The steam-engine
was still dependent for its power mainly on steam as an agent for
causing the required vacuum, until 1796, when Trevithick disclosed his
method of constructing small cylindrical boilers and engines suitable
for giving power from the strong pressure of the steam, irrespective of
vacuum.
Lean, who favoured Watt rather than Trevithick, thus records the advent
of Watt's expansive engine:--
"In 1779 to 1788 Mr. Watt introduced the improvement of working steam
expansively, and he calculated that engines which would previously do
nineteen to twenty millions would thus perform twenty-six millions;
but I do not find any record of this duty being performed in practice.
In 1785 Boulton and Watt had engines in Cornwall working expansively,
as at Wheal Gons and Wheal Chance in Camborne; but in these the steam
was not raised higher than before, and the piston made a considerable
part of the stroke therefore before the steam-valve was closed.
"In 1798, on account of a suit respecting their patent, which was
carrying on by Boulton and Watt, an account of the duty of all the
engines in Cornwall was taken by Davies Gilbert, Esq., and the late
Captain Jenkin, of Treworgie, and they found the average to be about
seventeen millions."[52]
[Footnote 52: Lean's 'Historical Statement of Steam-Engines in
Cornwall,' p. 7.]
One of these so-called expansive Watt engines, erected at Wheal Chance,
was converted into a real expansive engine by Trevithick, as described
in the foregoing chapter, by his high-pressure steam-boilers and the
addition of his pole-engine. The conversion of the other, a 63-inch
low-pressure vacuum engine at Wheal Gons, will be traced in this
chapter.
Mr. Taylor, who for many years took an active interest in Cornish
mining, says:--
"In 1798 an engine at Herland was found to be the best in the county,
and was doing twenty-seven millions, but being so much above all
others, some error was apprehended. This engine was probably the best
then ever erected, and attracted therefore the particular attention of
Messrs. Boulton and Watt, who, on a visit to Cornwall, came to see it,
and had many experiments tried to ascertain its duty. It was under the
care of Mr. Murdoch, their agent in the county.
"Captain John Davey, the manager of the mine, used to state that
it usually did twenty millions, and that Mr. Watt, at the time he
inspected it, pronounced it perfect, and that further improvement
could not be expected."[53]
[Footnote 53: 'Records of Mining,' by John Taylor, F.R.S., &c., part i.,
p. 155; published 1829.]
This best engine from the hands of Watt and Murdoch in the Herland Mine
in 1798 may be taken as a Watt stand-point, when its usual duty was
twenty millions; and Trevithick and Bull erected a competing engine,
probably with an increased steam pressure, for Trevithick's portable
high-pressure engines were at that time coming into notice;[54] but no
trace remains of the result of this contest of the Watt and the Bull
engine, though it was one of the causes of the lawsuits.
[Footnote 54: See vol. i., p. 95.]
"In 1799 Henry Clark worked as a rivet boy in Dolcoath, and carried
rivets to construct Captain Trevithick's new boiler, said to be the
first of the kind ever made. It looked like a great globe about 20
feet in diameter, the bottom hollowed up like the bottom of a bottle;
under this the fire was placed: a copper tube attached to this bottom
went around the inside of the boiler, and then passed out through the
side of the boiler, the outside brick flues then carrying the heat
around the outside of the boiler and into the chimney.
"Captain Trevithick's first plunger-pole lifts in Dolcoath were put in
at this time and worked by this engine. Glanville, the mine carpenter,
was head man over the engines when Captain Trevithick was away."[55]
[Footnote 55: Henry Clark's recollections in 1869.]
"Charles Swaine worked as a rivet boy in making Captain Trevithick's
cylindrical wrought-iron boilers for the Dolcoath engine. Several
of Captain Trevithick's high-pressure boilers were working in the
mines before that, but not made exactly like the Dolcoath engine
boilers. When I was a boy about the year 1804, several years before
I worked on the Dolcoath engine boilers, I carried father's dinner
to the Dolcoath smiths' shop, where he worked, and used to stop
and watch the wood beam going up and down of Captain Dick's first
high-pressure steam-whim. She was not a puffer, but a puffer-whim
worked near by, called the Valley puffer. At that time most of Captain
Dick's high-pressure boilers were smallish, cast iron outside, and
wrought-iron tube."[56]
[Footnote 56: Working in the Valley smiths' shop, in Dolcoath Mine, in
1869.]
In 1799, shortly after the reopening of Dolcoath Mine, Trevithick,
jun., selected his father's second-hand atmospheric engine of 1775,[57]
to further improve it by a new boiler of uniformly globular figure,
with concave circular bottom, under which fire was placed; it was of
wrought iron, 24 feet in diameter, surrounded by external brick flues;
a large copper tube, starting from the boiler bottom, immediately
over the fire, served as an internal flue, carrying the fire by a
sweep around the interior in the water space, and then out through the
side of the boiler into the external brick flue. It may be said that
there was nothing new in a circular form of boiler, or in an internal
tube; but it will be admitted that this repaired engine, in this its
third stride in the march of advancement, made publicly known those
principles which in a few years more than doubled the power, the
economy, and the applicability of the steam-engine. His patent drawing
of 1802 shows this form of boiler applied to a small portable engine,
in which, for the sake of simplicity of structure and cheapness, cast
iron was used instead of wrought iron, and the internal tube omitted.[58]
[Footnote 57: See vol. i., p. 25.]
[Footnote 58: See vol. i., p. 128.]
The full detail estimate, from which the following items are extracted,
of the cost of alteration was written by Trevithick, jun., in the book
and on the page adjoining that containing the account of the former
alteration and re-erection of the same engine by Trevithick, sen., in
1775.
"A 45-inch cylinder engine, working 20 lbs. to the inch:--
£ _s._ _d._
Boilers, 8 tons at 42_l._ 336 0 0
Iron about ditto, 6 cwt. at 42_l._ 12 12 0
Castings about ditto, 15 cwt. at 42_s._ 18 0 0
Safety-valve and cocks 1 0 0
Wood about bob, 200 ft. at 6_s._ 60 0 0
Cast iron about ditto, 45 cwt. at 25_s._ 56 5 0
Brass about ditto, 60 lbs. at 2_s._ 6 0 0
Piston-rod, 4 in., 14 ft. long, 550 lbs. at 1_s._ 27 10 0
T-piece, 10 cwt. at 25_s._ 12 10 0
Cover, and bottom, and piston, 35 cwt. at 32_s._ 56 0 0
Nozzles, 6 cwt. at 32_s._ 9 12 0
Steam and perpendicular pipe, 10 cwt. at 25_s._ 12 10 0
Receiver, 2 ft. 4 in. long, and bottom, 15 cwt. at 25_s._ 18 15 0
Air-pump, bottom, and case, 10 cwt. at 25_s._ 12 10 0
Plunger, 22 in., 6 ft. long, 12 cwt. at 40_s._ 24 0 0
Force lift 5 0 0
Engineer 66 0 0"
The term "single" refers to its open-top cylinder as originally erected
by Newcomen, when it was called the Carloose engine, and so it remained
after its re-erection in 1775, under the name Dolcoath new engine,
alias Bullan Garden; but after the last re-erection in 1799 it had a
cylinder-cover, and was called the Shammal 45-inch engine; "working 20
lbs. to the inch" meant the force on each inch of the piston, including
vacuum on the one side of 14 lbs. and steam on the other side of 6 lbs.
to the inch.
Watt, on his first visit to Cornwall, in 1777, spoke disparagingly of
the Newcomen atmospheric engines "burdened to 6 or 7 lbs. net to the
inch." Fifty years later Stuart described Watt's engine as "using steam
of a somewhat higher temperature than 212 degrees, so as to produce a
pressure between 17 and 18 lbs. on each square inch of the piston; yet
in practice, from imperfect vacuum and friction, it cannot raise more
water per inch than would weigh about 8-1/2 lbs.,"[59] or an increase of
net force--when compared with the Newcomen atmospheric--of only a pound
or two on the inch in the lapse of years embracing the active lifetime
of Watt. The cause of this slight increase of power is so simple that
it has been passed by unnoticed by very many. The steam pressure in
the Newcomen atmospheric was continued unaltered in the Watt vacuum
engine. Trevithick constructed the first boiler and engine capable of
safely and economically using the power of high-pressure steam. Nelson
was obliged to come to close quarters, that his shot, propelled by
weak cannon and low-pressure powder, might penetrate wooden ships. We
now manufacture and control high-pressure powder, so that 12 inches
of iron armour-plates cannot resist its force; but this knowledge
has taken nearly as long in growing to perfection as did the mastery
of high-pressure steam, and its use in the much more complicated
steam-engine.
[Footnote 59: Stuart's 'History of the Steam-Engine,' published 1824.]
Watt's engine, as described a quarter of a century after the expiration
of his patent and the advent of the high-pressure steam-engine, still
derived its gross force from 14 lbs. of vacuum and 2 or 3 lbs. of
steam, resulting in a net force of 8-1/2 lbs. Trevithick's engine of
1799, which heralded the last hours of the Watt patent authority,
and may be taken as the first distinct evidence of comparatively
high-pressure steam in large Cornish pumping engines, derived its power
from 14 lbs. of vacuum and 6 lbs. of steam, being together but 2 or 3
lbs. on the inch more than the Watt engine, but its net force of 12
lbs. to the inch was half again as much as the net force of the Watt
engine, the increase being wholly from the steam pressure, which was
never practised by Watt, and which in its almost unlimited force gives
the greatly increased power to modern steam-engines.
Trevithick's estimate for a new engine of the same size as the old
was 2000_l._, but as the old one could be improved for 1300_l._, the
latter course was adopted, the wooden main beam with its segment head
was retained, a cover was added to the cylinder, and a new piston-rod
and piston; a pole air-pump was used in lieu of the more usual Watt
air-pump bucket; a feed-pole forced water into the boiler,--an indirect
proof of increased steam pressure. The new globular boiler with
internal tube weighed 8 tons; the engineer's charge for carrying out
the work was 66_l._
The use of strong steam as the prime mover of the steam-engine
increased more rapidly beyond than within the limits of Cornwall, for
in 1802 was erected at Coalbrookdale a high-pressure steam-puffer
engine, to which Trevithick attached a pump which forced water through
a column of upright pipes, that the power of the engine might be
accurately measured. It worked with steam of from 50 to 145 lbs. on the
inch, and wholly discarded the vacuum which had been Watt's mainstay.
"The boiler is 4 feet diameter, the cylinder 7 inches diameter, 3-feet
stroke. The water-piston is 10 inches in diameter, drawing and forcing
35 feet perpendicular, equal beam. I first set it off with about 50
lbs. on the inch pressure against the steam-valve, for the inspection
of the engineers about this neighbourhood. The steam continued to rise
the whole of the time it worked; it went from 50 to 145 lbs. to the
inch.
"The engineers at this place all said that it was impossible for so
small a cylinder to lift water to the top of the pumps, and degraded
the principle, though at the same time they spoke highly in favour of
the simple and well-contrived engine.
"After they had seen the water at the pump-head, they said that it was
possible, but that the boiler would not maintain its steam at that
pressure for five minutes; but after a short time they went off, with
a solid countenance and a silent tongue."[60]
[Footnote 60: See Trevithick's letter, August 22nd, 1802, vol. i., p.
153.]
This high-pressure steam pumping engine in 1802 may be taken as the
first pumping engine of the puffer class using such strong steam.
In the spring of the following year[61] a somewhat similar engine was
erected in London. "The cylinder is 11 inches in diameter, with a
3-1/2-feet stroke. It requires the steam at a pressure of 40 to 45
lbs. to the inch to do its work well, working about twenty-six or
twenty-seven strokes per minute. It is much admired by everyone that
has seen it, and saves a considerable quantity of coal when compared
with a Boulton and Watt. Mr. Williams, Mr. Robert Fox, Mr. Gould, and
Captain William Davey were here, and much liked the engine; they gave
me an order for one for Cornwall as a specimen." This particular engine
was for driving machinery in a cannon manufactory. A high-pressure
pumping engine was at work at Greenwich, and some were at work in
Cornwall.
[Footnote 61: See Trevithick's letter, May 2nd, 1803, vol. i., p. 158.]
"PENYDARRAN, near CARDIFF,[**Check order of these lines]
"MR. GIDDY,
"_October 1st, 1803_.
"Sir,--In consequence of the engine bursting at Greenwich, I have
been on the spot to inspect its effects. I found it had burst in
every direction. The bottom stood whole on its seating; it parted
at the level of the chimney. The boiler was cast iron, about 1 inch
thick, but some parts were nearly 1-1/2 inch; it was a round boiler,
6 feet diameter; the cylinder was 8 inches diameter, working double;
the bucket was 18 inches diameter, 21 feet column, working single,
from which you can judge the pressure required to work this engine.
The pressure, it appears, when the engine burst, must have been very
great, for there was one piece of the boiler, about 1 inch thick and
about 5 cwt., thrown upwards of 125 yards; and from the hole it cut
in the ground on its fall, it must have been nearly perpendicular and
from a very great height, for the hole it cut was from 12 to 18 inches
deep. Some of the bricks were thrown 200 yards, and not two bricks
were left fast to each other, either in the stack or round the boiler.
It appears the boy that had care of the engine was gone to catch eels
in the foundation of the building, and had left the care of it to one
of the labourers; this man, seeing the engine working much faster than
usual, stopped it, without taking off a spanner which fastened down
the steam-lever, and a short time after being idle it burst, killed
three on the spot and another died soon after of his injuries. The
boy returned that instant, and was then going to take off the trig
from the valve. He was hurt, but is now recovering; he had left the
engine about an hour. I would be much obliged to you if you would
calculate the pressure required to burst this boiler at 1 inch thick,
supposing it to be a sound casting, and what pressure it would require
to throw the materials the distance I have before stated, for Boulton
and Watt have sent a letter to a gentleman of this place, who is about
to erect some of those engines, saying that they knew the effects
of strong steam long since, and should have erected them, but knew
the risk was too great to be left to careless enginemen, and that it
was an invention of Mr. Watt, and the patent was not worth anything.
This letter has much encouraged the gentlemen of this neighbourhood
respecting its utility; and as to the risk of bursting, they say it
can be made quite secure. I believe that Messrs. Boulton and Watt are
about to do me every injury in their power, for they have done their
utmost to report the explosion, both in the newspapers and in private
letters, very different to what it really was; they also state that
driving a carriage was their invention; that their agent, Murdoch, had
made one in Cornwall and shown it to Captain Andrew Vivian, from which
I have been enabled to do what I have done. I would thank you for any
information that you might have collected from Boulton and Watt, or
from any of their agents, respecting their even working with strong
steam, and if Mr. Watt has ever stated in any of his publications the
effects of it, because if he condemns it in any of his writings, it
will clearly show from that, that he did not know the use of it. Mr.
Homfray, of this place, has taken me by the hand, and will carry both
the engines and the patent to the test. There are several of Boulton
and Watt's engines being taken down here, and the new engines being
erected in their place. Above 700 horse-powers have been ordered at
12_l._ 12_s._ for each horse-power for the patent right, and the
persons that ordered them make them themselves, without any expense
to me whatever. If I can be left quiet a short time I shall do well,
for the engines will far exceed those of Boulton and Watt. The engine
at Greenwich did fourteen millions with a bushel of coals; it was
only an 8-inch cylinder, and worked without an expansive cock, and
under too light a load to do good duty; also on a bad construction,
for the fly-wheel was loaded on one side, so as to divide the power
of the double engine, and connected to the pump-rods on a very bad
plan. I remember that Boulton and Watt's 20-inch cylinders when on
trial did not exceed ten millions; I believe you have the figures
in your keeping. Let us have the 60-horse power at work that is now
building, and then I will show what is to be done. It will be loaded
at 30 lbs. to the inch on each side the piston, it has an 8-feet
stroke with an expansive cock, and the blowing cylinder directly over
the steam-cylinder, as free from friction as possible. There was no
engine stopped on account of this accident; but I shall never let the
fire come in contact again with the cast iron. The boiler at Greenwich
was heated red hot and burnt all the joints the Sunday before the
explosion.
"I have received a letter from a person in Staffordshire who has a
cylinder-boiler at work with the fire in it, and he says the engine
performs above all expectation; he requests me to give him leave
to build a great many more. I shall put two steam-valves and a
steam-gauge in future, so that the quicksilver shall blow out in case
the valve should stick, and all the steam be discharged through the
gauge. A small hole will discharge a great quantity of steam at that
pressure. There will be a railroad-engine at work here in a fortnight;
it will go on rails not exceeding an elevation of one-fiftieth part
of a perpendicular and of considerable length. The cylinder is 8-1/2
inches in diameter, to go about two and a half miles an hour; it is to
have the same velocity of the piston-rod. It will weigh, water and all
complete, within 5 tons.
"I have desired Captain A. Vivian to wait on you to give you every
information respecting Murdoch carriage, whether the large one at Mr.
Budge's foundry was to be a condensing engine or not.
"Is it possible that this engine might be burst by gas?
"I am, Sir,
"Your very obedient servant,
"RICHARD TREVITHICK."
This high-pressure puffer pumping engine at Greenwich, in 1803,
worked a pump of 18 inches in diameter. The engine boy having fixed
the safety-valve while he fished for eels, caused an explosion of
the boiler. This was the first mishap from the use of high-pressure
steam. The boiler was globular, 6 feet in diameter, and from an inch
to an inch and half in thickness, made of cast iron; the cylinder, of
8 inches in diameter, was partly let into and fixed on the boiler.
Its general design is seen in the patent drawing of 1802, Fig.
1.[62] Trevithick determined in future to use two safety-valves, and
also a safety steam-gauge. At that time one of his high-pressure
puffer-engines, with a cylindrical boiler and internal tube, was
working in Staffordshire.
[Footnote 62: See vol. i., p. 128.]
The Greenwich high-pressure puffer-engine did fourteen millions of
duty with a bushel of coals, 84 lbs. A 60-horse-power engine was being
built in Wales, with an 8-feet stroke, to work expansively with 30 lbs.
of steam on the inch in the boiler. For a more thorough test with the
low-pressure vacuum engines, in competition, the Government intended to
use the new engines, and some of Watt's engines having been removed to
make room for them, Boulton and Watt wrote to a gentleman who was about
to order an engine from Trevithick, "We knew the effects of strong
steam long since, and should have erected them, but knew the risk was
too great." Moreover, "it was an invention of Mr. Watt's, and the
patent (Trevithick's) was not worth anything." This admission clearly
shows not only that Watt did not make high-pressure steam-engines, but
that he did his best to prevent others from making them.
"MR. GIDDY, "PENYDARRAN, CARDIFF, _January 5th, 1804_.
"Sir,--I received yours a few days since, and should have answered
it sooner, but I was at Swansea for the last four weeks, and wished
to return here to give you as full an account of our proceedings as
possible.
"We have had an 8-inch cylinder at work here by way of trial; it
worked exceedingly well a hammer of the same size as is now being
worked here by an atmospheric engine 28 inches diameter, 5-feet
stroke, which does not master its work with greater ease than the
8-inch cylinder. The 8-inch is now removed to Swansea, and is winding
coals; the baskets hold 6 cwt. of coal; it lifts 80 yards in a minute
and a quarter, and burns 6 cwt. of coal in twenty-four hours. There
were twelve horses on this pit before, lifting 80 tons of coal in the
course of the twenty-four hours. You may fairly state that the 8-inch
cylinder does between thirty and forty horses' work in twenty-four
hours, with 6 cwt. of coal.
"One of Boulton and Watt's 18-inch double engine, about half a mile
from it, lifting baskets of the same size, and with the same velocity,
burns above three times the quantity of coal.
"The 8-inch engine requires the steam to be about 46 or 48 lbs. to the
inch to do its work well. The standers-by would not believe that such
a small engine could lift a basket of coal, but are now much pleased
with it, and have given orders for several more. There will be another
at work here for the same purpose in about six weeks, a 15-inch
cylinder, 6-feet stroke, which is a great power for a winding engine.
"Mr. Watt says, in a letter to Mr. Homfray, that he could not make any
of his experiments in strong steam answer the purpose. It is my belief
that he never made any experiments of any consequence in strong steam.
"A great number are building at different foundries. Mr. Sharratt, a
founder at Manchester, who has four in building, said that he would
not pay the patent right; on giving him notice of a trial he agreed to
pay the patent right.
"I have received a letter from London, saying that an engineer called
Dixon has two engines on the same plan working; and says that he
shall not pay anything to the patentee; that the words in Mr. Watt's
specification are enough to indemnify him from my threats. We have
had three counsels' opinions on the subject, and they all agree that
the patent is good. Counsels Marratt and Gibbs principally treated
on the construction of the engine, more than on the principle; but
Erskine was principally on the principle of the engine, and said very
little of its construction. They all say the words in Mr. Watt's
specification will have no weight whatever against us.
"I shall leave this place to-morrow for London to make inquiry into
those engines, and to get the business into court if they will
contend. I shall be at No. 2, Southampton Street, Strand, and expect
to be in town about five or six days, and if you will be so good as to
return here, from Oxford, with me, I will call on you in my journey
down. It is but 50 miles from Bristol, and not so much as 100 miles
from Oxford, and the coach passes very near this place.
"There is a great deal of machinery and mining here, which would
engage your attention for a few days, and very pleasant gentlemen
about the neighbourhood.
"If I had not been called to Swansea to put up the winding engine,
the road-engine would have been at work long since, but in my absence
very little was done to it. The work is all ready, and a part of it
put together. If I could tarry four or five days longer I could set
it to work before going to London. They promise me that it shall be
completed before my return. I think there is no doubt of its being
finished, as I have Frank Bennetts here from Cornwall about it, and a
plenty of hands to assist him.
"I have a thousand things to relate to you, too much for paper to
contain, therefore must request you to be so good as to go down from
Oxford with me, and I will promise, on warrant, that the road-engine
shall be finished before my return. When it is set to work I shall
return to Cornwall.
"I remain, Sir,
"Your humble servant,
"RICHARD TREVITHICK."
In 1804 an 8-inch cylinder high-pressure puffer-engine, with steam
of 48 lbs. to the inch, worked a large hammer as well as a 28-inch
cylinder atmospheric engine, and more economically than a Watt
low-pressure steam vacuum engine with an 18-inch cylinder, which was
five times as large as the little high-pressure. In consequence of this
superiority those who came to witness the trial ordered several more of
Trevithick's engines, one of which with a 15-inch cylinder and 6-feet
stroke was to be at work in a few weeks.
Watt wrote to Mr. Homfray "that he could not make any of his
experiments in strong steam answer the purpose," and Trevithick
declared Watt never could have tried any experiments with high steam.
Dixon refused to pay patent right because the words of Mr. Watt's
specification, "in cases where cold water cannot be had in plenty, the
engines may be wrought by the force of steam only, by discharging the
steam into the open air after it has done its office," "are enough to
indemnify him." Eminent counsel were of opinion that "the words in
Watt's specification will have no weight whatever."
Marratt and Gibbs were inclined to rest on the difference in the
construction of the two kinds of engines, while Erskine boldly said
that the principle was different, and he cared little for the kind of
construction.
The admission by Watt that he could do nothing with high steam after
an experience of thirty years from the date of his patent, shows how
difficult the work was to those who had to find the way; yet Trevithick
had several at work within a few months of his first mental sight of a
steam-engine without condensing water, fitful glimpses of which passed
and repassed while he sat unobserved in the crowded law court in 1796
hearing the remarks of engineers and counsel.
"The public until now called me a scheming fellow, but their tone is
much altered. An engine is ordered for the West India Docks, to travel
itself from ship to ship, to unload and to take up the goods to the
upper floors of the storehouses.
"Boulton and Watt have strained every nerve to get a Bill in the House
to stop these engines, saying the lives of the public are endangered
by them, and I have no doubt they would have carried their point, if
Mr. Homfray had not gone to London to prevent it; in consequence of
which an engineer from Woolwich was ordered down, and one from the
Admiralty Office, to inspect and make trial of the strength of the
materials."[63]
[Footnote 63: See Trevithick's letter, 22nd February, 1804, vol. i., p.
161.]
After a week or two another letter states,[64]--
"We are preparing to get the materials ready for the experiments by
the London engineers, who are to be here on Sunday next. We have fixed
up 28 feet of 18-inch pumps for the engine to lift water.
"These engineers particularly requested that they might have a given
weight lifted, so as to be able to calculate the real duty done by a
bushel of coal.
"As they intend to make trial of the duty performed by the coal
consumed, they will state it as against the duty performed by
Boulton's great engines, which did upward of twenty-five millions,
when their 20-inch cylinders, after being put in the best order
possible, did not exceed ten millions. As you were consulted on all
those trials of Boulton's engines, your presence would have great
weight with those gents, otherwise I shall not have fair play. Let
me meet them on fair grounds and I will soon convince them of the
superiority of the '_Pressure-of-steam engine_.'"
[Footnote 64: See Trevithick's letter, 4th March, 1804, vol. i., p. 166.]
Watt left no stone unturned to prevent the use of high-pressure
steam-engines, and fortune favoured him, for after four or five days
Trevithick again wrote:--
"I am sorry to inform you that the experiments that were to be
exhibited before the London gents are put off, on account of
an accident which happened to Mr. Homfray. I find myself much
disappointed on account of the accident, for I was desirous to make
the engine go through its different work, that its effect might be
published as early as possible."[65]
[Footnote 65: See Trevithick's letter, 9th March, 1804, vol. i., p. 168.]
While constructing those numerous high-pressure engines for rolling
mills, winding engines, and pumping engines, the Welsh and Newcastle
locomotives were being made and worked, yet he found time to teach the
people of Stourbridge.
"MR. GIDDY, "STOURBRIDGE, _July 5th, 1804_.
"Sir,--I should have answered your letter some time since, but waited
to set two other engines to work first. The great engine at Penydarran
goes on exceedingly well. The engine will roll 150 tons of iron a week
with 18 tons of coal. The two engines of Boulton's at Dowlais burn
40 tons to roll 160 tons; they are a 24-inch and a 27-inch double.
The engine at Penydarran is 18-1/2 inches, 6-feet stroke, works
about eighteen strokes per minute: it requires the steam about 45
lbs. to the inch above the atmosphere. I worked it expansive first,
when working the hammer, which was a more regular load than rolling;
then with steam high enough to work twelve strokes per minute with
the cock open all the stroke; then I shut it off at half the stroke,
which reduced the number of strokes to ten and a half per minute,
the steam and load the same in both; but I did not continue to work
it expansively, because the work in rolling is very uneven, and the
careless workmen would stop the engine when working expansive.
"When the cylinder was full of steam the rollers could not stop it;
and as coal is not an object here, Mr. Homfray wished the engine
might be worked to its full power. The saving of coal would be very
great by working expansively.
"The trials we have made for several weeks past against Boulton's
engines have been by working with the cylinder full of steam. The
cock springs out of its seat when water gets into the cylinder, and
prevents any mischief from the velocity of the fly-wheel.
"The tram-engine has carried two loads of 10 tons of iron to the
shipping place since you left this. Mr. Hill says he will not pay the
bet, because there were some of the tram-plates in the tunnel removed
so as to get the road into the middle of the arch.
"The first objection he started was that one man should go with the
engine, without any assistance, which I performed myself without help;
and now his objection is that the road is not in the same place as
when the bet was made.
"I expect Mr. Homfray will be forced to take steps that will force him
to pay. As soon as I return from here there will be another trial, and
some person will be called to testify its effects, and then I expect
there will be a lawsuit immediately. The travelling engine is now
working a hammer.
"At Worcester last week we put a 10-horse engine to work in a glover's
manufactory. The flue from the engine is carried through the drying
room and dries his leather. The steam from the engine goes to take
the essence out of the bark, and also to extract the colour out of
the wood for dyeing the leather. Then it boils the dye, and the steam
that is left is carried into his hot-house. It works exceedingly well.
This week I put another to wind coals at this place, a 10-horse power,
which works very well. All the tradesmen are set against it; they say
that there is no carpenter or mason work about it, and very little
smith-work, and that it will destroy their business. The engineer on
the spot is also against it very much. I do not expect that it will be
kept long at work after I leave it, unless the proprietor takes care
to prevent those people from doing an injury to it. Mr. Homfray was
here yesterday, but is now returned to Penydarran. I shall go from
here to Coalbrookdale.
"There is an engine there almost ready for the West India Docks. It
will be ready to send off to London in about four weeks. It will be a
very complete engine. The pumps for forcing the water will be fixed on
the back of the boiler. It will force 500 gallons of water 100 feet
high in a minute; above ten times the quantity that engines worked by
men can do. Mr. Homfray and myself shall be in town as soon as the
castings are sent off. I hope you will be there at the time. If you
wish to see the engines already at work in London, call on Mr. David
Watson, steam-engine maker, Blackfriars Road. He lives up about 500
or 600 yards above the bridge on the left-hand side; you will see his
name over his door. If you have time to inspect those engines you will
find by comparing them against Boulton's, doing the same work, that
there is a great saving of coal above other engines.... I shall go to
Liverpool and Manchester from here, and again to Coalbrookdale.
"There are three engines at the Dale begun, to work with condensers,
for places where coal is scarce. I think it is better to make them
ourselves, for if we do not, some others will, for there must be a
saving of coal by condensing. But with small engines, or where coal is
plentiful, the engine would be best without it. They say at the Dale
about putting two cylinders, but I think one cylinder partly filled
with steam would do equally as well as two cylinders.
"That engine at Worcester shuts off the steam at the first third of
the stroke, and works very uniformly. I cannot tell what coal it
burns yet, but I believe it is a very small quantity. I shall know in
a short time what advantage will be gained by working expansive. I
expect it will be very considerable. There are a great many engines
making and ordered. Boulton and Watt and several others are doing
everything to destroy their credit, but it is impossible to destroy
it now that it is so well known. I have not taken any of the ground
at Bristol to remove. I called on them and told them it was possible
to break the ground without men, and they wish me to take a piece to
clear out, but would not set but a small piece at a time; therefore
it would be disclosing the business to no purpose. They were very
desirous to know the plan, but I would not satisfy them, neither will
I unless they pay me for it in some way or other. If you direct for me
at the Dale it will find me. I am happy to find that you have a seat
in the House. I wish every seat was filled with such.
"I remain, Sir,
"Your very humble servant,
"RICHARD TREVITHICK."
Trevithick fully understood the value of the expansive principle in
1804: when working with steam of 45 lbs. to the inch, the engine went
at a speed of twelve strokes a minute. On cutting off the steam at
half-stroke, the speed and consequent work done fell to ten and a half
strokes a minute; in other words, the work performed by the engine fell
off only one-eighth part, while the quantity of steam and consequently
of coal was reduced by one-half. The principle was established, but
the application was practically incomplete from the want of heavier
fly-wheels, to give out their momentum during the latter half of the
stroke, when the expanding steam was lessening its force.
"The saving of coal would be very great by working expansively,
but as coal is not an object here," Mr. Homfray was careless about
the expansion. Thirty-three years after this indirect check to
steam-engine economy, the writer, then living in the Sirhowey Iron
Works, and within stone's-throw of Mr. Homfray's Works, recommended
the removal of the Boulton and Watt's waggon boilers, to make room
for Trevithick's boilers, on the plea of saving one-half the fuel,
and at the same time increasing the power of the engine, and thereby
the pressure of the blast in the iron furnaces. The proprietor was
careless about the saving of coal, and was doubtful that an increased
blast would increase the quantity of iron smelted. The promise that
the wages of one-half of the number of boiler firemen would be saved,
was understood. Trevithick's high-pressure boilers replaced the Watt
low-pressure, resulting in a largely-increased quantity of iron from
the greater power and pressure of blast in the furnaces, and at
one-half the expenditure of coal in the boilers: ten men had been
employed as firemen of the Watt boilers during twenty-four hours; with
Trevithick's boilers, five men did the work.
The high-pressure puffer-engine, with an 18-inch cylinder, working with
45 lbs. of steam, rolled as much iron as the two larger low-pressure
vacuum engines of Watt, of 24 and 27 inch cylinders, which together
were more than three times the size of the high-pressure engine, and
cost three times as much.
At Stourbridge, as elsewhere, everyone was against the new plan. The
engineer in charge did not like it, and the carpenters, smiths, and
masons saw the end of their occupation as engine erectors, if there was
no longer a necessity for foundations, well-work, &c., for condensing
water, and many other things, necessary to complete a Watt engine;
while the high-pressure puffer was no sooner unloaded than it was ready
to work.
A great charm in Trevithick's character was his freedom and largeness
of view in questions of competition. He was then making three engines
at Coalbrookdale, to be worked with high-pressure steam, combined with
the Watt air-pump and condenser; and though smarting from the contest
with his great rival, yet wrote, "I think it is better to make them
ourselves, for if we do not, some others will, for there must be a
saving of coal by condensing. But with small engines, or where coal is
plentiful, the engine would be best without it."
Those words accurately describe the practice of the present day, though
written sixty-six years ago, and were followed by others equally true
in principle, though varied in form to suit special requirement. "They
say at the Dale about putting two cylinders, but I think one cylinder
partly filled with steam would, do equally as well as two cylinders."
These sagacious views required the untiring labour of the following
twelve years to perfect and make practical, when applied to the largest
engines of the time; which we shall now trace in the construction of
a strong and economical boiler, supplying high-pressure steam to the
cylinder during only a comparatively small portion of the stroke,
completing it by expansion, so that at its finish the steam had become
of low pressure when passed to the condenser. The moving parts and
expansive gear were so simplified as to be applicable to the then
existing low-pressure steam vacuum engines without the complication of
the double cylinders of Hornblower and Woolf.
"DEAR SIR, "PENYDARRAN PLACE, _December 26th, 1804_.
"I have been favoured with your letter, and in answer, respecting Mr.
Mitchell, I am at a loss to know from your letter what kind of iron he
may likely want. If you will direct him to write to me, and explain
himself, I will immediately reply to him and do what I can to assist
and serve him. I believe there are vessels going over frequently from
Cardiff to Cornwall with coals, that he might have part in cargo and
the remainder in coals. I am happy to give you the most satisfactory
account of our 'Trevithick's engine' going on well. It has now been
at work many months, and is by far the best engine we have. We have
for weeks weighed the coal, and knowing the work it does, can speak
with confidence. Its 18 inches diameter steam-cylinder consumes as
near as can be 3 tons of coal in twenty-four hours, or 18 tons per
week; and in this time it rolls with ease 130 tons long weight of
iron from the puddling furnaces, at the same heat, into bars of 3
inches by about half an inch thick. Now, one on Messrs. Boulton and
Watt's plan, of '24 inches' steam-cylinder, at our neighbouring
works at Dowlais, employed in doing exactly the same kind of work,
consumes _full_ as much coal, and rolls only 90 tons in the week.
These being facts, open for any person daily to see, must convince
any dispassionate man of the superiority of 'Trevithick's engines,'
and that the saving of fuel is nearly one-third, besides the other
advantages of saving water and grease, which is no little. The
packing of the piston now gives us little or no trouble, it goes
from a fortnight to a month, opening the top now and then to screw
it down, as it gets slack, which should be attended to. We use no
grease or oil in packing the piston or working the engine, having
found blacklead mixed with water, and poured 'a little now and then'
through a hole on the top into the steam-cylinder, suits the packing
of the piston much better, and is cheaper than anything else. About
1_s._ worth of blacklead will last our engine a week. We are now so
thoroughly convinced of the superiority of these engines that I have
just begun another of larger size. The boiler is to be 24 or 26 feet
long, 7 feet diameter, fire-tube at wide end 4 feet 4 inches, and at
narrow end, where it takes the chimney, 21 inches, steam-cylinder 23
inches diameter. This boiler, on account of the length of its tube
withinside, will, I have no doubt, get steam in proportion, and work
the engine with much less coals than our present one. Trevithick is
at Coalbrookdale, Manchester, &c., &c., very busy, a great number
of engines being in hand in that part of the world; and I think by
perseverance the prejudice is wearing away very fast, and in spite of
all Messrs. Boulton and Watt's opposition, they must and will take the
lead of theirs. Any person now wanting engines, must be next kin to an
idiot to erect one of Boulton's in preference to Trevithick's. I find
there is a small one making near you by Mr. Vivian. I hope they have
corresponded with Trevithick about the proportions of it; if they
have not, I shall be particularly obliged to you to desire them to do
so, for by his experience of what he has done they may be benefited,
for it would be a shocking thing to have a bad engine put up for the
first time in his native county.
"Mrs. Homfray unites with me in best compliments, and wishing you many
happy returns of the season.
"I remain, dear Sir,
"Your most obedient servant,
"SAMUEL HOMFRAY.
"_To Mr. Davies Giddy._"
The evidence in this contest between the Watt low-pressure steam
vacuum engine and the Trevithick high-pressure steam-puffer engine is
in favour of the new principle; for the steam-engine with an 18-inch
cylinder did fifty per cent. more work than the vacuum engine with a
24-inch cylinder with an equal quantity of coal, though the latter was
seventy-five per cent. larger than the former; and a still greater
economy was expected from the larger boiler to be built, 26 feet long,
7 feet in diameter, with internal fire-tube 4 feet 4 inches diameter at
the fire end, tapering to 21 inches at the chimney end.
Thus in 1804 the cylindrical boiler in Wales had nearly reached its
present form, and Homfray thought that none but idiots would prefer the
Watt engine; forgetting that Trevithick's near friends and neighbours
were carrying on a similar contest at Dolcoath Mine.
"PENYDARRAN PLACE, _January 2nd, 1805_.
"MR. DAVIES GIDDY,
"Dear Sir,--I have duly received your favour enclosing a letter for
Mr. Trevithick, and which I, according to your desire, forwarded to
him at Manchester, where he now is; and a letter directed to him, to
the care of Mr. Whitehead, Soho Foundry, Manchester, will find him, as
he will stay a little time there, being very busy. I had lately the
pleasure of writing to you, and gave you the account of our engine
working, and the satisfaction it gives; I have nothing more to add
on the subject, but that it is now at work, going on as usual, and I
should be happy for you to have a sight of it.
"We are beginning another of a larger size, and I have no doubt but
by making the cylindrical boiler larger, so as to take a longer tube
withinside it, by which means the fire will spend itself before it
leaves the tube to go up the chimney, that we shall work to much
better advantage in point of fuel than we do at this present one, as
this boiler is so short that a great deal of the flame of the fire
goes up the chimney. We are now better acquainted with the different
proportions than we at first were, for which reason I am anxious
that one now making by Mr. Vivian should be made according to the
directions of Mr. Trevithick.
"I beg leave to offer you the compliments of the season, and many
happy returns, and
"Remain, respectfully, dear Sir,
"Your most obedient servant,
"SAMUEL HOMFRAY."
Trevithick, always busy, was just now doing the work of a host, for
everybody had to be taught how to make high-pressure steam-engines; and
the Newcastle locomotive, the Thames steam-dredging, and other special
applications of steam-power required his presence, especially the fight
with Watt at Dolcoath Mine, where Andrew Vivian, as mine manager, was
erecting a high-pressure steam-puffer whim-engine to compete with a
Watt low-pressure steam vacuum whim-engine.
"The adventurers grumbled because Captain Trevithick was so often away
from the mine. Glanville, the mine carpenter, the head man over the
engines, made a trial between Trevithick's high-pressure puffer whim
and Watt's low-pressure condenser. When Captain Trevithick heard of
it, he wrote down from London that he would bet Glanville 50_l._ that
his high-pressure puffer should beat Watt's low-pressure condenser.
Then he came down from London and found that the piston of his engine
was half an inch smaller in diameter than the cylinder. When a new
piston was put in, she beat Boulton and Watt all to nothing. Persons
were chosen to make a three or four weeks' trial, and when it was
over, 'a little pit was found with coal buried in it, that Glanville
meant to use in the Watt engine.'"[66]
[Footnote 66: Recollections of Henry Clark, living at Redruth in 1869.]
Pooly, Smith, and others, say that Trevithick's Dolcoath puffer had
the outer case of the boiler of cast iron, the fire-tube of wrought
iron, the cylinder horizontal, and fixed in the boiler. Captain Joseph
Vivian saw Trevithick's whim in Stray Park Mine about 1800 or 1801,
and a similar one was erected in Dolcoath, and after a year or two a
Boulton and Watt low-pressure whim was put up to beat it. The trial was
in favour of the Watt engine, but everybody said the agents were told
beforehand which way the report ought to go; so the engine that _puffed
the steam up the chimney_ was beaten.
Trevithick, who was busily engaged in Manchester at that time, the
early part of 1805, when informed of what was going on in Cornwall,
wrote:--
"I fear that engine at Dolcoath will be a bad one. I never knew
anything about its being built until you wrote to me about Penberthy
Crofts engine, when you mentioned it. I then requested Captain A.
Vivian to inform me the particulars about it, and I find that it will
not be a good job. I wish it never was begun."[67]
[Footnote 67: See Trevithick's letter, January 10th, 1805, vol. i., p.
324.]
"MR. GIDDY, "CAMBORNE, _February 18th, 1806_.
"Sir,--On my return from town I altered the pressure of the
steam-engine at the bottom of the hill, Dolcoath. Before I returned
there was a trial between mine and one of Boulton's; both engines in
the same mine and drawing ores from the same depth. The result was,
Boulton's beat the pressure-engine as 120 to 55. Since it was altered
there have been three other trials; the result was 147 to 35 in favour
of the pressure of the steam-engine. They are now on trial for another
month, and at the next account _they intend to order a new boiler for
the great engine_, and work with high-pressure steam and condenser,
provided this engine continues to do the same duty as was done in the
former trials. This engine is now drawing from a perpendicular shaft,
and Boulton and Watt's from an underlay shaft; but to convince Captain
Jos. Vivian, we put it to draw out of the worst shaft in the mine, and
then we beat more than three to one; we lifted in forty-seven hours,
233 tons of stuff 100 fathoms with 47 bushels of coal. The engine was
on trial sixty-six hours, but nineteen hours were hindered by the
shaft and ropes, &c., which made the consumption of coals about 3/4ths
of a bushel per hour. The fire-tube is 2 feet 3 inches diameter, and
the fire-bars were only 14 inches long. The fire-place was but 2 feet
3 inches wide by 14 inches long, and the fire about 4 or 5 inches
thick; it raised steam in plenty; it was as bright as a star. The
engine is now doing the work of two steam-whims; the other steam-whim
in the Valley is turned idle, and both shafts will not more than half
supply it. 233 tons are equal to nearly 2000 kibbals, which were drawn
in forty-seven hours.
"Mr. Harris has a 12-inch cylinder making at Hayle, for Crenver, and
Mr. Daniel has a 14-inch for Perran-sand, and a great number are
waiting for the trial of this month, _before altering their boilers to
the great engines_.
"The steam-whim that is now turned idle at the Valley was 13-1/2-inch
cylinder, 4-feet stroke; it turned the whim one revolution to one
stroke, and lifted the kibbal the same height at a stroke as my
engine did, and I think took the same number of gallons of steam to
lift a kibbal as mine did. Their steam was not above 4 lbs. to the
inch; _mine was near 40 lbs. to the inch_; yet I raised my steam of
near 40 lbs. with a third of the coals by which they got theirs of
4 lbs. to the inch. This is what I cannot account for, unless it is
by getting the fire very small and extremely hot. Another advantage
I have is, that there is no smoke that goes off from my fire to clog
the fire sides of the boiler, while the common boilers get soot half
an inch thick, and the mud falls on the bottom of the boiler, where
the fire ought to act; but in these new boilers the mud falls to
the bottom, where there is no fire, and both the inside and outside
of the tube are clean and exposed both to fire and water. This
fire-*place[**hyphenated below] of 14 inches was 5 feet long when I
came down, and then the coal did not do above one-seventh of the duty
that it now does.
"I would be very much obliged to you for your opinion on what I have
stated, and what _advantage you think the great engine is likely to
get from working with steam about 25 lbs. to the inch, and shut off
early in the stroke, so as to have the steam about 4 lbs. to the inch
when the piston is at the bottom. I think this, with the advantage of
the fire-place, will make a great saving._
"The present fire-place is 22 feet from fire-door to fire-door, 9 feet
wide, and 7 feet thick in fire. There is not one-tenth of the coals
that are in the fire-place on fire at the same time; it will hold 30
tons of coals at one time, and I think that a great deal of coal is
destroyed by a partial heat before it takes fire. A boiler on the
new plan will not cost more than two-thirds of the old way, and will
last double the time, and can be cleaned in three hours. It requires
twenty-four hours in the old way, and we need to clean the boilers
only one-fourth the number of times.
"Though these trials have shown so fairly that it is a great
advantage, my old acquaintances are still striving with all their
might to destroy the use of it; but facts will soon silence them.
"I am about to enter into a contract with the Trinity Board for
lifting up the ballast out of the bottom of the Thames for all the
shipping. The first quantity stated was 300,000 tons per year, but
now they state 500,000 tons per year. I am to do nothing but wind up
the chain for 6_d._ per ton, which is now done by men. They never
lift it above 25 feet high. A man will now get up 10 tons for 7_s._
My engine at Dolcoath has lifted above 100 tons that height with 1
bushel of coals. I have two engines already finished for this purpose,
and shall be in town in about fifteen days to set them at work. They
propose to engage with me for twenty-one years. The outlines of the
contract they have sent me down, which I think is on very fair terms.
I would thank you for your answer before I leave this county.
"I am, Sir,
"Your very humble servant,
"RD. TREVITHICK."
In the trial at Dolcoath during his absence the high-pressure
steam-puffer whim was beaten by Watt's low-pressure steam vacuum
whim-engine as 55 to 120; but having corrected some oversight in the
puffer-engine, it then beat Watt as 147 to 35. The trial was to be
continued for a month; and provided the superiority of his whim-engine
could be maintained, the adventurers would allow him to apply his
high-pressure boilers to their large Boulton and Watt pumping engine.
The trial with the whim-engines was for the greatest number of kibbals
of mineral raised to the surface by the least consumption of coal. A
dispute arose on the difference of the shafts, the one causing more
friction to the moving kibbal than the other, when Trevithick agreed
to take the worst shaft in the mine. On a trial during sixty-six hours
Watt's engine was beaten by more than four times; and as Trevithick's
engine did the work that before required two engines, one of the
low-pressure steam Watt engines was removed that the engine working
with 40 lbs. on the inch might perform the whole work.
"My fire-tube is 2 feet 3 inches in diameter, and the fire-bars only
14 inches long, and the fire only about 4 or 5 inches thick; it raised
steam in plenty, and was as bright as a star." These words certainly
imply the use of the blast-pipe, making the fire as bright as a star,
and enabling the small boiler to give the required supply of steam.
Several high-pressure puffer-engines had been ordered, and many persons
were waiting the conclusion of the month's public trial to enable them
to judge between the Watt and the Trevithick engine.
"MR. GIDDY, "CAMBORNE, _March 4th, 1806_.
"Sir,--The day after I wrote to you the first letter, I received
yours, and this day I have yours of the 1st instant.
"I am very much obliged to you for the figures you have sent me. I am
convinced that the _pressure of steam will not hold good as theory
points it out, because on expanding it will get colder, and of course
lose a part of its expansive force after the steam-valve shuts_. I
think there can be no risk in making this trial on Dolcoath great
engine, as they intend to have a new boiler immediately, so as to
prevent stopping to cleanse; and a boiler on this new plan can be
made for one-third less expense than on the old plan, when you count
the large boiler-house and ashes-pit, and brickwork round the boiler.
It is not intended to alter any part of the engine or condenser, but
only work with high steam from this new boiler; and if this boiler
only performs as good duty as the old one, it will be a saving of near
300l. to them on the erection. _The vast matter this great engine has
in motion will answer in part the use of a fly-wheel_: the whole of
the matter in motion is near about 200 tons, at a velocity of about
160 feet a minute. This I know will not be sufficient; but it will be
about equal to a fly-wheel of 20 feet diameter, 25 tons weight, twenty
rounds per minute, if weight and velocity answer the same purpose.
"Since Monday, the 18th February, being Dolcoath account-day, both
engines have been on trial, and are to be continued until the next
account, 17th instant. The engines are kept on in the usual way, as
at other times. Neither of the engines have done so much duty as on
the first trials, as they have not been so strictly attended to. The
average of the trial at this time stands 26 cwt. for a bushel of coals
to Boulton and Watt's engine; mine, 83 cwt. for a bushel of coals.
"If I do not remain in Cornwall to attend next Dolcoath account, I
shall be in town about the 15th instant, otherwise about the 20th
instant. I shall call on you immediately on my arrival. In this time
I should be glad to hear from you again. The Trinity business will
answer exceedingly well; I have two engines ready for that purpose to
put to work on my arrival in town.
"I am, Sir,
"Your very humble servant,
"RD. TREVITHICK.
"P.S.--I would try the evaporation of water by both boilers, but
Boulton and Watt's engine is so pressed with work, and being on the
best part of the mine, they will not stop it a moment. A boiler of 8
feet diameter and 30 feet long will have as much fire-sides in the
tube as there is now in Dolcoath great boiler. The fire-tube in this
boiler would be 5 feet diameter, and a fire-place 6 feet long in it
would be 30 feet of fire-bars. In the whim-engines I find that a
fire-place 14 inches long and the tube 2 feet 3 inches diameter would,
being forced, burn 1 bushel per hour. At this rate the great tube
would burn near 12 bushels per hour, which is above the quantity that
the great engine boiler can consume, now at work. Small tubes would
have an advantage over large ones. Two boilers would not cost much
more than one large one, and be much stronger."
The battle-ground of the fight between low and high pressure from 1806
to 1812 had also served for the personal encounter of Trevithick, sen.,
and Watt a quarter of a century before, when the Dolcoath great pumping
engine was erected to compete with the two earlier atmospherics; all
three were still at work, overlooked by Carn Brea hill and castle, once
the resort of Druid priests, whose sacrificial rites are still traced,
by the hollows and channels for the blood of victims on the granite
rocks.
[Illustration: CARN BREA CASTLE. [W. J. Welch.]]
"MR. GIDDY, "CAMBORNE, _March 21st, 1806_.
"Sir,--The trial between the two engines ended last Monday, which
was Dolcoath day. Boulton and Watt's engine, per average of trial,
1 ton 20 cwt. 2 qrs., with 1 bushel of coals; the other, 5 tons 11
cwt. 3 qrs., with 1 ditto, the same depth of shaft. The adventurers
ordered the new castings that were made for another of Boulton and
Watt's engines to be thrown aside, and another new engine of mine to
be built immediately. The great boiler for the old engine is not yet
ordered.
"I have received orders for nine engines within these four weeks, all
for Cornwall. Two 12-inch cylinders, two 16-inch ditto, three 9-inch
ditto, one 8-inch ditto, one 7-inch ditto. I expect one will be put to
work next week at Wheal Abraham, for lifting water.
"This day I shall leave Cornwall for London. Shall stop two days in
the neighbourhood of Tavistock, and take orders for three engines. As
soon as I arrive in town I will call at your lodgings. I expect that
the patent will be brought into court about the end of May. A person
in Wales owes us about 600_l._ patent premium, and he says that the
patent is not good. More particulars you shall have on my arrival.
"The railroad is going forward. I have the drawings in hand for the
inclined plane.
"I am, Sir,
"Your very humble servant,
"RD. TREVITHICK."
The fact that expansion of steam caused reduction of heat was so
evident to Trevithick that he ventured to doubt his friend's theory.
The trials between the whim-engines having continued a fortnight,
showed that the high-pressure steam-puffer had lifted 83 cwt., while
the low-pressure steam vacuum only lifted 26 cwt. with the consumption
of a bushel of coal. A suitable high-pressure boiler for the Watt
low-pressure steam 63-inch pumping engine should be 30 feet long,
8 feet in diameter, with an internal fire-tube 5 feet in diameter;
proportions approved of in the present day. The recommendation in 1806
to use small tubes may claim to be the first practical decision on the
advantage of tubular boilers; and at the same time we read of the first
hesitating step on the part of the public to use high-pressure steam
in a Watt low-pressure engine, which was still deferred for further
consideration, even with the limited pressure of 25 lbs. to an inch;
so the large Watt pumping engines were doomed for another four or five
years to struggle through their work with low-pressure steam, though at
that time Cook's Kitchen high-pressure expansive condensing whim-engine
had been for years at work close by.
The shareholders professed to have fear of explosion; but party-feeling
and ignorance were the real causes of opposition, for working men had
no dread of the new engines, while influential men leaned toward Watt's
old-fashioned plans.
This fear of Trevithick's expansive plans and high steam is the more
surprising, because at that time a new boiler was required for the Watt
63-inch cylinder pumping engine and Trevithick's cylindrical tubular
boiler could be made for one-third less cost than the Watt waggon
boiler, thus saving 300_l._, and in addition he promised to apply the
higher pressure of steam to the Watt engine without any change in
its parts or expenditure of money, and make it set in motion at the
commencement of the stroke the 200 tons of pump-rods, the momentum of
which would, with the expansion of the steam, when shutting it off soon
after the first start in the movement of each stroke, carry it through
to the end; and he practically compares this advantage from hoarded
momentum in the pumping engine with his experience of the fly-wheel of
the rolling-mill expansive engine in Wales.
The whim-engine with a fire-tube 2 feet 3 inches in diameter used 84
lbs. of coal per hour; and at that rate one cylindrical boiler 30 feet
long, 8 feet in diameter, with internal fire-tube 5 feet in diameter,
would supply steam for Watt's 63-inch cylinder; but in place of it he
preferred two smaller boilers, because small tubes have an advantage
over large ones, and are much stronger.
The whim trials--high-pressure puffer against low-pressure vacuum--went
on for another fortnight, when high pressure, having done twice as
much work as low pressure, with an equal consumption of coal, the
adventurers threw aside the work that had been made for another Watt
engine, ordering one in its stead from Trevithick; but they could not
just then make up their minds to place the Watt 63-inch pumping engine
in his hands.
"DEAR SIR, "CAMBORNE, _May 30th, 1806_.
"I am very happy to find you have so far continued your agreement with
the Trinity gents, and think the bargain is a good one. Must still beg
leave to remind you not to proceed to show what your engine will do
till the agreement is fully drawn up and regularly signed.
"Dolcoath agents, since they are informed of the accident at the
iron-works in Wales, _of the engine blowing to pieces_, have requested
me to have your opinion whether the old cylinder is strong enough for
the boiler of the intended new engine, or whether you would recommend
them to have a new one. Your answer to this as soon as possible, as
Mr. Williams and some others are likely to make some objections.
"Mr. Sims, the engineer, has published in the Truro paper, that one of
Boulton and Watt's engines at Wheal Jewell has drawn more than a ton
of ore over and above that drawn by the Dolcoath engine from the same
depth by a bushel of coal. On inquiry I found they had only tried for
twenty-two hours. They said they left off with as good a fire as they
began with. This I argued was not a fair trial. They say they are now
on a trial for a month.
"The little engine at Wheal Abraham does its duty extremely well. The
particulars as to consumption of coal cannot be fairly ascertained, as
she has never been covered, is fed with cold water, and has not water
to draw to keep her constantly at work.
"I wish I could give a better account of the mines than is in my power
to give, or of the standard price for ore, though the latter is rather
looking up than otherwise. Our friend, North Binner Downs, is better
than paying cost, but very little. At present the levels are all poor;
the lode in the west shaft has underlayed faster than the shaft, and
we have not seen it for several fathoms. The ground lately in the
shaft has been cleaner killas, and if any alteration, better ground.
It is now 9 fathoms under the 55-fathom level, and we are driving to
cut the lode. The ground in the cross-cut is harder than when you were
on the spot. The water is sinking in old Binner; it is about 7 fathoms
under the adit in the western part, and deeper in the eastern part; we
do not account for this. Wheal St. Aubyn combined poor. Wheal Abraham
looks promising, and Creuver about paying cost. Dolcoath is better
than when you left us, or when I was in London. The last sale was only
about 800 tons. The next sale on Thursday is upwards of 1100 tons, and
we expect a little better standard.
"I wish you could discover who that old gent is that wanted a large
slice in Dolcoath, that I might get at him through some unknown
channel, for I want money sadly.
"Cook's Kitchen continues poor, Tin Croft ditto; Wheal Fanny not rich.
We had a pretty little fight last account there with T. Kevill and W.
Reynolds, Esquires: black eyes and bloody noses the worst effects. T.
Kevill's face was much disfigured, and he might have found a new road
out of his coat.
"At a meeting of Condurrow adventurers yesterday, twenty-four of them
agreed to have one of our engines, cylinder 12 inches in diameter and
6-feet stroke, provided the Foxes do not object to it. When the order
is given I shall write to Mr. Hazeldine, provided I do not hear from
you that it is better to send the order to any other place.
"If you have occasion to write Mr. Hazeldine, I wish you would press
him to hasten the engines for Wheal Goshen, &c.
"I am served with a Vice-warden's petition by Mr. Harris for not
working the Weith mine in a more effectual manner, and he prays the
Vice-warden to make the sett void. The trial will come on some time
the beginning of July, and by that time I suppose we shall have two
fire-engines working thereon.
"Had Mr. Harvey done as he was desired we should have had one working
there at this time, but he has but now begun to do anything to it. We
have the cylinder and ends home from Polgooth, and my cousin Simon
Vivian is making the tubes. We have the other cylinder from Wheal
Treasury, and I have ordered Horton to cast a cock for it the same as
that at Dolcoath. We have cut the south lode at the adit level about
50 or 60 fathoms east of the engine, and have driven about 20 fathoms
on it. It turns out about half a ton per fathom at 20_l._ a ton. The
ground at 40_s._ per fathom; this all in a hole, and is better going
down. The back is sett to four men at 3_s._ 11_d._; their time is out
this week, and I suppose they must have 5_s._ next. This may turn out
a few thousands, and I think too promising a thing to give up to Mr.
Harris.
"I am happy to inform you that all our friends are in good health, and
beg my most respectful compliments to Mrs. Rogers and adopted son; and
am,
"Dear Sir,
"Yours very sincerely,
"ANDW. VIVIAN.
"The promised news respecting the engine business I am very anxious
to have, as it will I hope make me _proud_, as proud I shall be when
I am able to pay everyone their demands, and have sufficient to carry
on a little business to maintain my family and self without the
assistance of others. May you succeed in your undertaking and also
be independent, is the sincere wish of your friend. John Finnis and
others are anxious to know when they will be wanted.
"A. V."
The explosion at Greenwich in 1803 was made much of, though the
fault was clearly not in the boiler. Three years afterwards, in
1806, a steam-cylinder burst in Wales, therefore Mr. Williams, a
large shareholder in Dolcoath, objected to the use of high-pressure
expansive steam in their large Watt pumping engine, and desired their
engineer, Mr. Sims, to make a competitive trial after his own fashion.
At Condurrow Mine one of Trevithick's engines was to be ordered if the
Foxes and Williamses did not object; and so it was that Trevithick's
high-pressure steam-boiler was not ordered, and the Watt vacuum engine
was for a longer time to receive no increase of power.
"Some of Captain Dick's early boilers had flattish or oval fire-tubes.
In 1820 I repaired an old one in Wheal Clowance Mine in Gwinear. The
flat top had come down a little; we put in a line of bolts, fastening
the top of the tube to the outer casing.
"About 1818 I saw in Carsize Mine in Gwinear a pumping engine that
Captain Dick had put up. The boiler was a cylinder of cast iron, with
a wrought-iron tube going through its length in which the fire was
placed. The steam-cylinder was vertical, fixed in the boiler. She had
an air-pump and worked with a four-way cock. The steam was about 100
lbs. to the inch."[68]
[Footnote 68: Banfield's recollections in 1869.]