"Hayle Foundry,September 14th, 1829.""Mr. Gilbert,"Sir,—I expected to have seen you before this, but am detained by Mr. Harvey's attorney to settle the Foundry Quay. As I made the drawing and model of the disputed ground, and was examined in evidence in court, it was thought proper that I should be present at the time that Mr. Peters came to determine the boundary line between the two companies. This cannot be concluded for ten days."As I have been so long detained I wish to await your arrival in Cornwall for the purpose of trying the new engine while you are down, and will thank you to inform me when you intend to be with us."I remain, Sir,"Your very humble servant,"Richard. Trevithick.
"Hayle Foundry,September 14th, 1829.
""Mr. Gilbert,
"Sir,—I expected to have seen you before this, but am detained by Mr. Harvey's attorney to settle the Foundry Quay. As I made the drawing and model of the disputed ground, and was examined in evidence in court, it was thought proper that I should be present at the time that Mr. Peters came to determine the boundary line between the two companies. This cannot be concluded for ten days.
"As I have been so long detained I wish to await your arrival in Cornwall for the purpose of trying the new engine while you are down, and will thank you to inform me when you intend to be with us.
"I remain, Sir,"Your very humble servant,"Richard. Trevithick.
Erskine, who had expressed the opinion favourable to Trevithick's engine more than twenty years before,[148]was in this trial the counsel for the opposing side. The verdict was in favour of Mr. Harvey, or Trevithick's side.
A former chapter[149]speaks of promises to pay certain savings by the use of Trevithick's inventions prior to his leaving for America. The United Mines refused to continue the payment, and on Mrs. Trevithick's application to Mr. Davies Gilbert for advice he kindly wrote to the Williamses, who managed those mines, and received the following reply:—
"Scorrier House,November 14th, 1820.""Dear Sir,"... with regard to Mrs. Trevithick's claims for savings on engines at the United Mines, there is much to be said."Before Mr. Trevithick went abroad he sold half the patent right to William Sims, our engineer, who very strongly recommended that two of the engines at the United Mines should be altered to what he considered his patent principle, but the alterations proved very inferior to his expectations, and to this circumstance I attribute much of the objections in question. Mr. Henry Harvey has perhaps told you who the partners are in the patent, and when you next come into this county I shall be much pleased to wait on you at Tredrea that you may hear the whole of the case; and though the United Mines adventurers are far from being a united body, I am very sure my sons, who are their managers, are desirous to recommend what appears to them right, and they will with myself be obliged for your opinion after you have heard the whole matter on both sides."Dear Sir,"Yours very sincerely,"Jno. Williams."Davies Gilbert, Esq., M.P."
"Scorrier House,November 14th, 1820.
""Dear Sir,
"... with regard to Mrs. Trevithick's claims for savings on engines at the United Mines, there is much to be said.
"Before Mr. Trevithick went abroad he sold half the patent right to William Sims, our engineer, who very strongly recommended that two of the engines at the United Mines should be altered to what he considered his patent principle, but the alterations proved very inferior to his expectations, and to this circumstance I attribute much of the objections in question. Mr. Henry Harvey has perhaps told you who the partners are in the patent, and when you next come into this county I shall be much pleased to wait on you at Tredrea that you may hear the whole of the case; and though the United Mines adventurers are far from being a united body, I am very sure my sons, who are their managers, are desirous to recommend what appears to them right, and they will with myself be obliged for your opinion after you have heard the whole matter on both sides.
"Dear Sir,"Yours very sincerely,"Jno. Williams.
"Davies Gilbert, Esq., M.P."
The opinion of Mr. Williams' elder son, Michael, has been given.[150]Some of the family were quakers. No further money payment for the saving of fuel followed this carefully civil note, until Trevithick, on his returnfrom America, called at Scorrier House in a very threatening attitude on 31st October, 1827, when Mr. Williams, sen., said his reason for not continuing the payment was from his belief that the term of the patent had expired. Then came the following lawyer's letter:—
"Penzance,7th November, 1827.""Sir,"I was at Captain Trevithick's yesterday, who observed to me he saw you at Scorrier a few days ago, and requested you would be good enough to settle the arrears on the savings on some of the engines in the mines for which you acted, none having been paid for a year or two, when you stated that the payment had been discontinued on account of the patent having expired. I find on a reference to the patent that it will not expire till May, 1830."Iam, Sir,"Your obedient servant,"Rd. Edmonds."John Williams, Esq.,Scorrier."
"Penzance,7th November, 1827.
""Sir,
"I was at Captain Trevithick's yesterday, who observed to me he saw you at Scorrier a few days ago, and requested you would be good enough to settle the arrears on the savings on some of the engines in the mines for which you acted, none having been paid for a year or two, when you stated that the payment had been discontinued on account of the patent having expired. I find on a reference to the patent that it will not expire till May, 1830.
"Iam, Sir,"Your obedient servant,"Rd. Edmonds.
"John Williams, Esq.,Scorrier."
"Hayle,January 24th, 1828."Sir,"Yesterday I called on Mr. Williams, and after a long dispute brought the old man to agree to pay me 150l.on giving him an indemnification in full from all demands on Treskerby and Wheal Chance Mines in future. He requested that you should make out this indemnification. I could not possibly get them to pay more, and thought it most prudent to accept their offer rather than risk a lawsuit with them."I remain, Sir,"Your obedient servant,"Richard. Trevithick."Rd. Edmonds, Esq.
"Hayle,January 24th, 1828.
"Sir,
"Yesterday I called on Mr. Williams, and after a long dispute brought the old man to agree to pay me 150l.on giving him an indemnification in full from all demands on Treskerby and Wheal Chance Mines in future. He requested that you should make out this indemnification. I could not possibly get them to pay more, and thought it most prudent to accept their offer rather than risk a lawsuit with them.
"I remain, Sir,"Your obedient servant,"Richard. Trevithick.
"Rd. Edmonds, Esq.
"Treskerby and Wheal Chance were, I believe, the only mines that paid for the use of the pole patent. Mr. John Williams, sen., of Scorrier, was purser of those mines. The agreement was that patentees should have one-fourth part of the savings of coal above twenty-six millions. The one-half of this fourth part from these two mines for some years was about 150l.per annum. This did not relate to the boilers;Trevithick unfortunately did not take out a patent for that improvement. The adventurers of two or three mines only had the honesty to pay 100l.for each mine; others made use of it without acknowledgment."Rd. Edmonds."Penzance,12th January, 1853."
"Treskerby and Wheal Chance were, I believe, the only mines that paid for the use of the pole patent. Mr. John Williams, sen., of Scorrier, was purser of those mines. The agreement was that patentees should have one-fourth part of the savings of coal above twenty-six millions. The one-half of this fourth part from these two mines for some years was about 150l.per annum. This did not relate to the boilers;Trevithick unfortunately did not take out a patent for that improvement. The adventurers of two or three mines only had the honesty to pay 100l.for each mine; others made use of it without acknowledgment.
"Rd. Edmonds.
"Penzance,12th January, 1853."
Such were the recollections of the family solicitor many years after the events had passed. The cylindrical high-pressure steam boiler and engine was really included in the patent of 1802; but frequent detail changes, consequent on size and position and local requirements, were made up to 1811, when a perfected form was arrived at, which is still in use. In principle it was unaltered and not materially different in form, but being used for larger engines, looked different. The inventor saw nothing in this difference, but the public did, and in the absence of the only man who could prove their error refused to pay on the plea of its not being patented. On his return from America he demanded 1000l.from each of the large Cornish mines, as a settlement in full for all benefits derived from the use of the Trevithick high-pressure steam-boiler. He had proved the weakness of the law years before, when three eminent counsel had given opinions on the 1802 patent, one of them believing the patent good, because the principle contained was new; two of them feared that similarity of details might invalidate it:[151]so he determined to apply to the Government for remuneration for benefits that might be called national.
"Hayle,December 20th, 1827.""Mr. Rd. Edmonds,"Sir,—I send the principal heads of what you will have to put in form to lay before the House. It is very defective; but you will be assisted by Captain Andrew Vivian, who cangive dates and particulars, having been engaged with Mr. Gilbert and Captain Matthew Moyle in making out the duty performed at that time by Boulton and Watt and Hornblower's engines. He can also give you the results of the late improvements, with much more information than I can give. I saw him yesterday for this purpose; he will assist you with all his power, and will call on you at Penzance on Friday or Saturday. As I shall with pleasure pay him for his trouble, you need not fear calling on him for what assistance you need."Mr. Gerard and I propose to leave this for London on Saturday. If you think it necessary to see me, let Captain Vivian know it, and all meet at my house. I have sent you one of the monthly reports, in which you will see John Lean's report of Dolcoath engines, from which I have given you in my statement the average results and savings."I remain, Sir,"Your very humble servant,"Richard. Trevithick."P.S.—I was at Dolcoath account on Monday, and made known to them my intention of applying to Government, and not to individuals, for remuneration. They are ready to put their signatures to the petition, and so will all the county. I fear that it is as much as we shall do to get it before the House in time."
"Hayle,December 20th, 1827.
""Mr. Rd. Edmonds,
"Sir,—I send the principal heads of what you will have to put in form to lay before the House. It is very defective; but you will be assisted by Captain Andrew Vivian, who cangive dates and particulars, having been engaged with Mr. Gilbert and Captain Matthew Moyle in making out the duty performed at that time by Boulton and Watt and Hornblower's engines. He can also give you the results of the late improvements, with much more information than I can give. I saw him yesterday for this purpose; he will assist you with all his power, and will call on you at Penzance on Friday or Saturday. As I shall with pleasure pay him for his trouble, you need not fear calling on him for what assistance you need.
"Mr. Gerard and I propose to leave this for London on Saturday. If you think it necessary to see me, let Captain Vivian know it, and all meet at my house. I have sent you one of the monthly reports, in which you will see John Lean's report of Dolcoath engines, from which I have given you in my statement the average results and savings.
"I remain, Sir,"Your very humble servant,"Richard. Trevithick.
"P.S.—I was at Dolcoath account on Monday, and made known to them my intention of applying to Government, and not to individuals, for remuneration. They are ready to put their signatures to the petition, and so will all the county. I fear that it is as much as we shall do to get it before the House in time."
The following petition was drawn up and put into the hands of his old friend Davies Gilbert, then a Member of Parliament:—
"To the Honourable the Commons of the Kingdom of Great Britain and Ireland in Parliament Assembled."The Humble Petition of Richard Trevithick, of the Parish of Saint Erth, in the County of Cornwall, Civil Engineer, 27th February, 1828,"Sheweth:"That this kingdom is indebted to your petitioner for some of the most important improvements that have beenmade in the steam-engine, for which your petitioner has not hitherto been remunerated, and for which he has no prospect of being ever remunerated except through the assistance of your Honourable House."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 half (pounds of water lifted 1 foot high by 1 bushel of coals), although a chosen engine of theirs, under the most favourable circumstances, at Herland Mine lifted twenty-seven millions,[152]which was the greatest duty ever performed till your petitioner's improvements were adopted, since which the greatest duty has been sixty-seven millions, being 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 applied under it, and the whole surrounded with mason-work. That such shaped boilers were incapable of supporting steam of a high pressure, 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, who had been for many years employed in making steam-engines on the principle of Boulton and Watt, and had made considerable improvements in their machinery, directed his attention principally to the invention of a boiler which should be free from these disadvantages; and after having devoted much of his time and spent nearly all his property in the attainment of this object, he at length succeeded in inventing and perfecting that which has since been generally adopted throughout the kingdom."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 derivedfrom 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. Accidents by fire can never occur, as the fire is entirely surrounded by water, and greater duty can be performed by an engine with this boiler, with less than half the fuel, than has ever been accomplished by any engine without it. These great advantages render this small and portable boiler not only superior to all others used in mining and manufacturing, but likewise is the only one which can be used with success in steam-vessels or steam-engine carriages. The boilers in use prior to your petitioner's invention could never with any degree of safety or convenience be used for steam navigation, because they required a protection of brick and mason work around them, to confine the fire by which they were encircled, and it would have been impossible, independent of the great additional bulk and weight, that boilers thus constructed could withstand the rolling of vessels in heavy seas; and notwithstanding every precaution the danger of the fire bursting through the brick and mason work could never be effectually guarded against."That had it not been for this, your petitioner's, invention, those 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, much less a pressure of 60 lbs. to the inch, or even of above 150 lbs. to the inch when necessary."That as soon as your petitioner had brought his invention into general use in Cornwall, and had proved to the public its immense utility, he was obliged in 1816 to leave England for South America to superintend extensive silver mines in Peru, from whence he did not return until October last. That at the time of your petitioner's departure the old boilers were falling rapidly into disuse, and when he returned he found they had been generally replaced by those of his invention, and that the saving of coals occasioned thereby during that period amounted in Cornwall alone to above 500,000l.[153]
"To the Honourable the Commons of the Kingdom of Great Britain and Ireland in Parliament Assembled.
"The Humble Petition of Richard Trevithick, of the Parish of Saint Erth, in the County of Cornwall, Civil Engineer, 27th February, 1828,
"Sheweth:
"That this kingdom is indebted to your petitioner for some of the most important improvements that have beenmade in the steam-engine, for which your petitioner has not hitherto been remunerated, and for which he has no prospect of being ever remunerated except through the assistance of your Honourable House.
"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 half (pounds of water lifted 1 foot high by 1 bushel of coals), although a chosen engine of theirs, under the most favourable circumstances, at Herland Mine lifted twenty-seven millions,[152]which was the greatest duty ever performed till your petitioner's improvements were adopted, since which the greatest duty has been sixty-seven millions, being 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 applied under it, and the whole surrounded with mason-work. That such shaped boilers were incapable of supporting steam of a high pressure, 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, who had been for many years employed in making steam-engines on the principle of Boulton and Watt, and had made considerable improvements in their machinery, directed his attention principally to the invention of a boiler which should be free from these disadvantages; and after having devoted much of his time and spent nearly all his property in the attainment of this object, he at length succeeded in inventing and perfecting that which has since been generally adopted throughout the kingdom.
"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 derivedfrom 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. Accidents by fire can never occur, as the fire is entirely surrounded by water, and greater duty can be performed by an engine with this boiler, with less than half the fuel, than has ever been accomplished by any engine without it. These great advantages render this small and portable boiler not only superior to all others used in mining and manufacturing, but likewise is the only one which can be used with success in steam-vessels or steam-engine carriages. The boilers in use prior to your petitioner's invention could never with any degree of safety or convenience be used for steam navigation, because they required a protection of brick and mason work around them, to confine the fire by which they were encircled, and it would have been impossible, independent of the great additional bulk and weight, that boilers thus constructed could withstand the rolling of vessels in heavy seas; and notwithstanding every precaution the danger of the fire bursting through the brick and mason work could never be effectually guarded against.
"That had it not been for this, your petitioner's, invention, those 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, much less a pressure of 60 lbs. to the inch, or even of above 150 lbs. to the inch when necessary.
"That as soon as your petitioner had brought his invention into general use in Cornwall, and had proved to the public its immense utility, he was obliged in 1816 to leave England for South America to superintend extensive silver mines in Peru, from whence he did not return until October last. That at the time of your petitioner's departure the old boilers were falling rapidly into disuse, and when he returned he found they had been generally replaced by those of his invention, and that the saving of coals occasioned thereby during that period amounted in Cornwall alone to above 500,000l.[153]
"That the engines in Cornwall, in which county the steam-engines used are more powerful than those used in any other part of the kingdom, have now your petitioner's improved boilers, and it appears from the monthly reports that these engines, which in 1798 averaged only fourteen and half millions now average three times that duty with the same quantity of coals, making a saving to Cornwall alone of 2,781,264 bushels of coals, or about 100,000l.per annum. And the engines at the Consolidated Mines in November, 1827, performed sixty-seven millions, being forty millions more than had been performed by Boulton and Watt's chosen engine at Herland, as before stated."That had it not been for your petitioner's invention, the greater number of the Cornish mines, which produce nearly 2,000,000l.per annum, must have been abandoned in consequence of the enormous expense attendant on the engines previously in use."That your petitioner has also invented the iron stowage water-tanks and iron buoys now in general use in His Majesty's navy, and with merchant's ships."That twenty years ago your petitioner likewise invented the steam-carriage, and carried it into general use on iron railroads."That your petitioner is the inventor of high-pressure steam-engines, and also of water-pressure engines now in general use."That his high-pressure steam-engines work without condensing water, an improvement essentially necessary to portable steam-engines, and where condensing water cannot be procured."That all the inventions above alluded to have proved of immense national utility, but your petitioner has not been reimbursed the money he has expended in perfecting his inventions. That your petitioner has a wife and large family who are not provided for."That Parliament granted to Messrs. Boulton and Watt, after the expiration of their patent for fourteen years, an extension of their privileges as patentees for an additional period, whereby they gained, as your petitioner has been informed, above 200,000l."That your petitioner therefore trusts that these his ownimportant inventions and improvements will not be suffered to go unrewarded by the English nation, particularly as he has hitherto received no compensation for the loss himself and his family have sustained by his having thus consumed his property for the public benefit."Your petitioner therefore most humbly prays that your Honourable House will be pleased to take his case into consideration, and to grant him such remuneration or relief as to your Honourable House shall seem meet."And your petitioner, as in duty bound, will ever pray, &c."Rd. Edmonds,"Solicitor, Penzance."
"That the engines in Cornwall, in which county the steam-engines used are more powerful than those used in any other part of the kingdom, have now your petitioner's improved boilers, and it appears from the monthly reports that these engines, which in 1798 averaged only fourteen and half millions now average three times that duty with the same quantity of coals, making a saving to Cornwall alone of 2,781,264 bushels of coals, or about 100,000l.per annum. And the engines at the Consolidated Mines in November, 1827, performed sixty-seven millions, being forty millions more than had been performed by Boulton and Watt's chosen engine at Herland, as before stated.
"That had it not been for your petitioner's invention, the greater number of the Cornish mines, which produce nearly 2,000,000l.per annum, must have been abandoned in consequence of the enormous expense attendant on the engines previously in use.
"That your petitioner has also invented the iron stowage water-tanks and iron buoys now in general use in His Majesty's navy, and with merchant's ships.
"That twenty years ago your petitioner likewise invented the steam-carriage, and carried it into general use on iron railroads.
"That your petitioner is the inventor of high-pressure steam-engines, and also of water-pressure engines now in general use.
"That his high-pressure steam-engines work without condensing water, an improvement essentially necessary to portable steam-engines, and where condensing water cannot be procured.
"That all the inventions above alluded to have proved of immense national utility, but your petitioner has not been reimbursed the money he has expended in perfecting his inventions. That your petitioner has a wife and large family who are not provided for.
"That Parliament granted to Messrs. Boulton and Watt, after the expiration of their patent for fourteen years, an extension of their privileges as patentees for an additional period, whereby they gained, as your petitioner has been informed, above 200,000l.
"That your petitioner therefore trusts that these his ownimportant inventions and improvements will not be suffered to go unrewarded by the English nation, particularly as he has hitherto received no compensation for the loss himself and his family have sustained by his having thus consumed his property for the public benefit.
"Your petitioner therefore most humbly prays that your Honourable House will be pleased to take his case into consideration, and to grant him such remuneration or relief as to your Honourable House shall seem meet.
"And your petitioner, as in duty bound, will ever pray, &c.
"Rd. Edmonds,"Solicitor, Penzance."
From the Patent Office to the House of Commons was, for a petitioner, as bad as out of the frying-pan into the fire. Trevithick solicited the support of Members of Parliament until tired of running after friends, and the petition became a dead letter, though the mining interests of Cornwall had in twelve years saved 500,000l.by his unrewarded inventions.
"Lauderdale House, Highgate,December 24th, 1831."Mr. Gilbert,"Sir,—I find that Mr. Spring Rice cannot get the Lords of the Treasury to agree to remunerate or assist me in any way. He appeared to be much disappointed, and said that he would write to the Admiralty Board on Thursday last, recommending them to adopt this engine. As yet I have heard nothing respecting it, nor do I expect to during the holy days; but in the interim I wish to look out for some moneyed man to join in it, otherwise I fear I shall lose the whole. Can you assist in recommending anyone you know? I wish Mr. Thompson would come into it, he would be a good man. Can you furnish me with a copy of your report to Mr. Spring Rice, or something relating thereto? It would be a great assistance in getting some one to join."The sum required is small, and the risk is less; but theprospect is great, beyond anything I ever knew offered on such easy terms. Waiting your reply,"I remain, Sir,"Your very humble servant,"Richard. Trevithick.
"Lauderdale House, Highgate,December 24th, 1831.
"Mr. Gilbert,
"Sir,—I find that Mr. Spring Rice cannot get the Lords of the Treasury to agree to remunerate or assist me in any way. He appeared to be much disappointed, and said that he would write to the Admiralty Board on Thursday last, recommending them to adopt this engine. As yet I have heard nothing respecting it, nor do I expect to during the holy days; but in the interim I wish to look out for some moneyed man to join in it, otherwise I fear I shall lose the whole. Can you assist in recommending anyone you know? I wish Mr. Thompson would come into it, he would be a good man. Can you furnish me with a copy of your report to Mr. Spring Rice, or something relating thereto? It would be a great assistance in getting some one to join.
"The sum required is small, and the risk is less; but theprospect is great, beyond anything I ever knew offered on such easy terms. Waiting your reply,
"I remain, Sir,"Your very humble servant,"Richard. Trevithick.
"Eastbourne,December 26th, 1831."Dear Trevithick,"I am sorry to find that you have not any prospect of assistance from Government. I have not any copy or memorandum of my letter to Mr. Spring Rice; but it was to the effect of first bearing testimony to the large share that you have had in almost all the improvements on Mr. Watt's engine, which have altogether about trebled its power; to your having made a travelling engine twenty-eight years ago; of your having invented the iron-tanks for carrying water on board ships, &c."I then went on to state that the great defect in all steam-engines seemed to be the loss, by condensation, of all the heat rendered latent in the conversion of water into steam; that high-pressure engines owed their advantages mainly to a reduction of the relative temperatures of this latent heat; that I had long wished to see the plan of a differential engine tried, in which the temperatures and consequently elasticities of the fluid might be varied on the opposite sides of the piston, without condensation; that the engine you have now constructed promised to effect that object; and that, in the event of its succeeding at all, although it might not be applicable to the drawing water out of mines, yet that for steam-vessels and for steam-carriages its obvious advantages would be of the greatest importance; and I ended by saying that although it was clearly impossible for me to ensure the success of any plan till it had been actually proved by experiment, yet judging theoretically, and also from the imperfect trial exhibited on the Thames, I thought it well worthy of being pursued. Your plan unquestionably must be to associate some one with you (as Mr. Watt did Mr. Boulton), and I certainly think it a very fair speculation for any such person as Mr. Boulton to undertake."It is impossible for me to point out any individual, as neverhaving had the slightest connection with trade or with manufacture in any part of my life, I am entirely unacquainted with mercantile concerns. I cannot, however, but conjecture that you should make a fair and full estimate of what would be the expense of making a decisive experiment on a scale sufficiently large to remove all doubt; and that your proposal should be, that anyone willing to incur that expense should, in the event of success, be entitled to a certain share of your patent. On such conditions some man of property may perhaps be found who would undertake the risk; and if the experiment proves successful, he will be sure to use every exertion afterwards for his own sake. With every wish for your success,"Believe me,"Yours very sincerely and faithfully,"Davies Gilbert.
"Eastbourne,December 26th, 1831.
"Dear Trevithick,
"I am sorry to find that you have not any prospect of assistance from Government. I have not any copy or memorandum of my letter to Mr. Spring Rice; but it was to the effect of first bearing testimony to the large share that you have had in almost all the improvements on Mr. Watt's engine, which have altogether about trebled its power; to your having made a travelling engine twenty-eight years ago; of your having invented the iron-tanks for carrying water on board ships, &c.
"I then went on to state that the great defect in all steam-engines seemed to be the loss, by condensation, of all the heat rendered latent in the conversion of water into steam; that high-pressure engines owed their advantages mainly to a reduction of the relative temperatures of this latent heat; that I had long wished to see the plan of a differential engine tried, in which the temperatures and consequently elasticities of the fluid might be varied on the opposite sides of the piston, without condensation; that the engine you have now constructed promised to effect that object; and that, in the event of its succeeding at all, although it might not be applicable to the drawing water out of mines, yet that for steam-vessels and for steam-carriages its obvious advantages would be of the greatest importance; and I ended by saying that although it was clearly impossible for me to ensure the success of any plan till it had been actually proved by experiment, yet judging theoretically, and also from the imperfect trial exhibited on the Thames, I thought it well worthy of being pursued. Your plan unquestionably must be to associate some one with you (as Mr. Watt did Mr. Boulton), and I certainly think it a very fair speculation for any such person as Mr. Boulton to undertake.
"It is impossible for me to point out any individual, as neverhaving had the slightest connection with trade or with manufacture in any part of my life, I am entirely unacquainted with mercantile concerns. I cannot, however, but conjecture that you should make a fair and full estimate of what would be the expense of making a decisive experiment on a scale sufficiently large to remove all doubt; and that your proposal should be, that anyone willing to incur that expense should, in the event of success, be entitled to a certain share of your patent. On such conditions some man of property may perhaps be found who would undertake the risk; and if the experiment proves successful, he will be sure to use every exertion afterwards for his own sake. With every wish for your success,
"Believe me,"Yours very sincerely and faithfully,"Davies Gilbert.
The petition to Parliament for a national payment for national gains, so hopefully taken up on his return from America, when experience had proved the value of his inventions, after four weary years of deferred expectation, was consigned to the tomb of forgetfulness.
Compare the petition of 1828 with a modern report.
"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 wagon; 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, and does not require half of the materials, nor does it occupy half the space required for any other boiler, and greater duty can be performed by an engine with this boiler with less than half the fuel, than by any engine without it, and is the only one that can be used with success in steam-vessels, as none of the old boilers could have withstood a pressure of above 6 lbs. on the inch, much less a pressure of 60 lbs. or even of 150 lbs. when necessary."
"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 wagon; 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, and does not require half of the materials, nor does it occupy half the space required for any other boiler, and greater duty can be performed by an engine with this boiler with less than half the fuel, than by any engine without it, and is the only one that can be used with success in steam-vessels, as none of the old boilers could have withstood a pressure of above 6 lbs. on the inch, much less a pressure of 60 lbs. or even of 150 lbs. when necessary."
A report of the Royal Mail Steam Packet Company in 1871 states, "by placing compound engines in the 'Tasmania,' they had reduced the consumption of coal to one-half the former quantity, doubled her capacity for freight, and increased her speed."[154]Presuming that the compound engines of the 'Tasmania' are like other engines known by that name, having high-pressure steam in a comparatively small cylinder from which it expands in a larger one, tubular boilers, surface condensers, and screw-propeller, the saving admitted in the 'Tasmania' is just what Trevithick's petition pointed out forty-three years ago—to lessen by one-half the weight, space, and fuel in marine steam-engines—his opinion being founded on the experience of a lifetime, for as early as 1804 he wrote on the question of compound engines, "I think one cylinder partly filled with steam would do equally as well as two cylinders;"[155]and again in 1816, describing expansion, "The engine is now working with 60 lbs. of steam, three-quarters of the stroke expansive, and ends with the steam rather under atmosphere strong;"[156]and in the same year worked the expansive compound engine at Treskerby.[157]
TUBULAR BOILER, SUPERHEATING STEAM, AND SURFACE CONDENSER.
"Hayle Foundry,December 14th, 1828.""Mr. Gilbert,"Sir,—On my return from London five weeks since I was disappointed at not finding you in Cornwall. I have made inquiry into the duty performed by the best engines, and the circumstances they are under, from which it appears to me there is something which as yet has not been accounted for, particularly in Binner Downs engines. A statement was given to me by Captain Gregor, the chief agent and engineer of the mine, which appears so plain that I cannot doubt the facts, though they differ very widely from all former opinions. There are two engines, one of 42 inches diameter, the other of 70 inches diameter, 10-feet stroke."Formerly those engines worked without cylinder cases, when the 70-inch cylinder burnt 1½ wey of coal, and performed a regular duty of forty-one millions; since that time brickwork has been placed round the cylinder and steam-pipes, leaving a narrow flue, which is heated by separate fires. These flues consume about 5 bushels of coal in twenty-four hours; the heat is not so great as to injure the packing, which stands good for thirteen weeks; the saving for several months past has increased the duty to sixty-three millions."Before the use of this flue 108 bushels of coal were consumed under the boiler, now only 67 bushels are needed, which with the 5 bushels in the flue gives 72 bushels. The coal burnt under the boiler gives a duty of sixty-six millions, or an expansion of 60 per cent. by the heat of 5 bushels of coal in the flues, and a duty of 1781 millions gained in twenty-four hours by 5 bushels of coal, which amounts to 350 millions gained by each of these 5 bushels. The 42-inch cylinder is as near as possible under the same circumstances, no other alterationshave been made; and to prove this they left out the fires in the flues, and the engines fell back to their former duty, and the condensing water increased in the same proportion."The surface sides heated by this 5 bushels of coal is about 300 surface feet, the saving effected is 1781 millions, which is six millions saving for each foot of surface on the castings in the flues. In Wheal Towan engine that did eighty-seven millions, the surface sides of the boiler was 1000 feet of fire-sides for every bushel of coal burnt in an hour, and the duty performed per minute from each foot of boiler fire-sides was 1500 lbs. 1 foot high. Now it appears that the heating of Binner Downs 300 surface feet gave a saving of 6000 lbs. per minute per surface foot; whereas the boiler sides only gave 1500 lbs. of duty per minute for each foot of boiler fire-sides. Therefore the saving by heating the sides of the cylinder is equal to four times the duty done by each square foot of boiler sides; and further, it appears that the 300 feet, when not heated, though clothed round with brickwork, condensed or prevented from expanding the steam of 41 bushels of coals, which was eight times as much steam condensed as the 5 bushels of coal would raise. Now if this be a report of facts, which I have no reason to doubt (but still I will be an eye-witness to it next week), there must be an unknown propensity in steam above atmosphere strong to a very sudden condensation, andvice versâ, to also a sudden expansion, by a small heat applied to the steam-sides; and if by heating steam, independent of water, such a rapid expansion takes place, certainly a rapid condensation must take place in the same ratio, which might be done at sea by cold sides to a great advantage, always working with fresh water."I shall have a small portable engine finished here next week, and will try to heat steam, independent of water, in small tubes of iron, on its passage from the boiler to the cylinder, and also try cold sides for condensing."If the above statement prove to be correct, almost anything might be done by steam, because then additional water would not be wanted for portable engines, but partially condensed and again returned into the boiler, without any fresh supply or the incumbrance of a great quantity; and boilers might be madewith extensive fire-sides, both to heat water and steam, and yet be very light."It appears that this engine, when working without the heated flues round the cylinder and pipes, evaporated 20,000 gallons of water into steam, in twenty-four hours, more than when the flues were heated, and the increase of condensing water was in the same proportion. It is so unaccountable to me that I shall not be satisfied until I prove the fact, the result of which I will inform you, and shall be very glad to receive your remarks on the foregoing statement."The first engine that will be finished here for Holland will be a 36-inch cylinder, and a 36-inch water-pump, to lift water about 8 feet high; on the crank-shaft there is a rag-head of 8 feet diameter, going 8 feet per second, with balls of 3 feet diameter passing through the water-pump, which will lift about 100 tons of water per minute. It is in a boat of iron, 14 feet wide, 25 feet long, 6 feet high, so as to be portable, and pass from one spot to another, without loss of time. It will drain 18 inches deep of water (the annual produce on the surface of each acre of land) in about twenty minutes for the drainage of each acre, with one bushel or sixpennyworth of coal per year. The engine is high pressure and condensing."I remain, Sir,"Your very humble servant,"Richard. Trevithick."P.S.-Woolf is making an apparatus to throw back from the bottom of the cylinder on to the top of the piston a fluid metal every stroke. He says he proved by an indicator that he raised 18,000 inches of steam from 1 inch of water, of 11 lbs. to the inch pressure on a vacuum, and that the reason why this engine did not do 300 millions, was because the steam passed by the sides of the piston. That an engine at the Consolidated Mines working 10 feet 2 inch stroke, going 7/8ths expansive, beginning with steam of 20 lbs. to the inch above the atmosphere, and ending with 11 lbs. on a vacuum. I doubt this statement; however, there is some hidden theory as yet, becausesome engines perform double as much as others, under the same known circumstances, and I believe that nothing but practice will discover where this defect is, for, in my opinion, no statement of theory yet given is satisfactory why high-pressure engines so far exceed low-pressure engines. It is facts that prove it to be so, therefore all theory yet laid down must be defective."
"Hayle Foundry,December 14th, 1828.
""Mr. Gilbert,
"Sir,—On my return from London five weeks since I was disappointed at not finding you in Cornwall. I have made inquiry into the duty performed by the best engines, and the circumstances they are under, from which it appears to me there is something which as yet has not been accounted for, particularly in Binner Downs engines. A statement was given to me by Captain Gregor, the chief agent and engineer of the mine, which appears so plain that I cannot doubt the facts, though they differ very widely from all former opinions. There are two engines, one of 42 inches diameter, the other of 70 inches diameter, 10-feet stroke.
"Formerly those engines worked without cylinder cases, when the 70-inch cylinder burnt 1½ wey of coal, and performed a regular duty of forty-one millions; since that time brickwork has been placed round the cylinder and steam-pipes, leaving a narrow flue, which is heated by separate fires. These flues consume about 5 bushels of coal in twenty-four hours; the heat is not so great as to injure the packing, which stands good for thirteen weeks; the saving for several months past has increased the duty to sixty-three millions.
"Before the use of this flue 108 bushels of coal were consumed under the boiler, now only 67 bushels are needed, which with the 5 bushels in the flue gives 72 bushels. The coal burnt under the boiler gives a duty of sixty-six millions, or an expansion of 60 per cent. by the heat of 5 bushels of coal in the flues, and a duty of 1781 millions gained in twenty-four hours by 5 bushels of coal, which amounts to 350 millions gained by each of these 5 bushels. The 42-inch cylinder is as near as possible under the same circumstances, no other alterationshave been made; and to prove this they left out the fires in the flues, and the engines fell back to their former duty, and the condensing water increased in the same proportion.
"The surface sides heated by this 5 bushels of coal is about 300 surface feet, the saving effected is 1781 millions, which is six millions saving for each foot of surface on the castings in the flues. In Wheal Towan engine that did eighty-seven millions, the surface sides of the boiler was 1000 feet of fire-sides for every bushel of coal burnt in an hour, and the duty performed per minute from each foot of boiler fire-sides was 1500 lbs. 1 foot high. Now it appears that the heating of Binner Downs 300 surface feet gave a saving of 6000 lbs. per minute per surface foot; whereas the boiler sides only gave 1500 lbs. of duty per minute for each foot of boiler fire-sides. Therefore the saving by heating the sides of the cylinder is equal to four times the duty done by each square foot of boiler sides; and further, it appears that the 300 feet, when not heated, though clothed round with brickwork, condensed or prevented from expanding the steam of 41 bushels of coals, which was eight times as much steam condensed as the 5 bushels of coal would raise. Now if this be a report of facts, which I have no reason to doubt (but still I will be an eye-witness to it next week), there must be an unknown propensity in steam above atmosphere strong to a very sudden condensation, andvice versâ, to also a sudden expansion, by a small heat applied to the steam-sides; and if by heating steam, independent of water, such a rapid expansion takes place, certainly a rapid condensation must take place in the same ratio, which might be done at sea by cold sides to a great advantage, always working with fresh water.
"I shall have a small portable engine finished here next week, and will try to heat steam, independent of water, in small tubes of iron, on its passage from the boiler to the cylinder, and also try cold sides for condensing.
"If the above statement prove to be correct, almost anything might be done by steam, because then additional water would not be wanted for portable engines, but partially condensed and again returned into the boiler, without any fresh supply or the incumbrance of a great quantity; and boilers might be madewith extensive fire-sides, both to heat water and steam, and yet be very light.
"It appears that this engine, when working without the heated flues round the cylinder and pipes, evaporated 20,000 gallons of water into steam, in twenty-four hours, more than when the flues were heated, and the increase of condensing water was in the same proportion. It is so unaccountable to me that I shall not be satisfied until I prove the fact, the result of which I will inform you, and shall be very glad to receive your remarks on the foregoing statement.
"The first engine that will be finished here for Holland will be a 36-inch cylinder, and a 36-inch water-pump, to lift water about 8 feet high; on the crank-shaft there is a rag-head of 8 feet diameter, going 8 feet per second, with balls of 3 feet diameter passing through the water-pump, which will lift about 100 tons of water per minute. It is in a boat of iron, 14 feet wide, 25 feet long, 6 feet high, so as to be portable, and pass from one spot to another, without loss of time. It will drain 18 inches deep of water (the annual produce on the surface of each acre of land) in about twenty minutes for the drainage of each acre, with one bushel or sixpennyworth of coal per year. The engine is high pressure and condensing.
"I remain, Sir,"Your very humble servant,"Richard. Trevithick.
"P.S.-Woolf is making an apparatus to throw back from the bottom of the cylinder on to the top of the piston a fluid metal every stroke. He says he proved by an indicator that he raised 18,000 inches of steam from 1 inch of water, of 11 lbs. to the inch pressure on a vacuum, and that the reason why this engine did not do 300 millions, was because the steam passed by the sides of the piston. That an engine at the Consolidated Mines working 10 feet 2 inch stroke, going 7/8ths expansive, beginning with steam of 20 lbs. to the inch above the atmosphere, and ending with 11 lbs. on a vacuum. I doubt this statement; however, there is some hidden theory as yet, becausesome engines perform double as much as others, under the same known circumstances, and I believe that nothing but practice will discover where this defect is, for, in my opinion, no statement of theory yet given is satisfactory why high-pressure engines so far exceed low-pressure engines. It is facts that prove it to be so, therefore all theory yet laid down must be defective."
Mount's BayMount's Bay.[W. J. Welch.]
Mount's Bay.[W. J. Welch.]
At the date of this letter Trevithick had been rather more than a year in England, residing generally at Hayle, within half-a-dozen miles of Mount's Bay, from which he had sailed for America; and after eleven years of wandering in countries where steam-engines were unknown, except those that he himself had constructed, was again on his return giving his whole thoughts to the idol of his life.
During that period scientific men in Europe thought and wrote much on the question of relative temperature, pressure, economy, and manageability of steam. Newcomen's great discovery a century before was the avoidance of the loss of heat by the cooling at each stroke of the exterior of the steam-vessel of Savery's engine by injecting cold water into the steam in the cylinder. After fifty years came the Watt improvement, still reducing the loss of heat by removing the cold injection-water from the steam-cylinder to a separate condenser.
The high-pressure steam-engine was perfect without injection-water, though when convenient its use was equally applicable as in the low-pressure engine. Trevithick, on his return to civilized life, read the views of Watt on steam, as given in 'Farey on the Steam-Engine.' On informing Davies Gilbert of his doubts of the accuracy of those views, and of his intention of testing them by comparison with the work performed by Cornish pumping engines, his friend, who had just published his 'Observations on the Steam-Engine,'[158]forwarded a copy, from which the following is an extract:—
"One bushel of coal, weighing 84 lbs., has been found to perform a duty of thirty, forty, and even fifty millions, augmenting with improvements, chiefly in the fire-place, which produce a more rapid combustion with consequently increased temperature, and a more complete absorption of the generated heat; in addition to expansive working, and to the use of steam raised considerably above atmospheric pressure."
"One bushel of coal, weighing 84 lbs., has been found to perform a duty of thirty, forty, and even fifty millions, augmenting with improvements, chiefly in the fire-place, which produce a more rapid combustion with consequently increased temperature, and a more complete absorption of the generated heat; in addition to expansive working, and to the use of steam raised considerably above atmospheric pressure."
Those words gave the result of Trevithick's experience made known to his friend during twenty years of labour,[159]and yet by a seeming fatality his name is not found in his friend's book.
Sir John Rennie, who in youth had been employed under Boulton and Watt at Soho, and had risen to be a member of the Royal Society, came about that time into Cornwall, at the request of the Admiralty, to make examination into the work performed by Cornish pumping engines, and selected Wheal Towan engine on which to make special experiments.[160]The subject of Trevithick's note was therefore at that period, and still is, a matter of importance; and his practical treatment of the question is more instructive to young engineers than complex rules. Arthur Woolf was at the same time experimenting on steam at the Consolidated Mines, and finding the want of agreement between the rules of low-pressure and the practice of high-pressure engines, imputed the error to the escape of steam by the sides of the piston. Trevithick disbelieved this, "because some engines perform double as much as others, under the same known circumstances," and advocated the observance of general practice to prove why high-pressure engines were more economical than those of low-pressure. Captain Gregor had placed fire-flues around the steam cylinder and pipes, hoping thereby to exceed the duty of the Wheal Towan engine, whose boiler, cylinder, and steam-pipes were carefully clothed with a thick coating of sawdust or other non-conductor of heat, and lifted eighty-seven millions of pounds of water 1 foot high by the heat from a bushel of coal weighing 84 lbs. This was the greatest duty that had ever been recorded from a steam-engine. The Trevithick or Cornish boilers,similar to those in Dolcoath,[161]measured at the rate of 1000 superficial feet of heating surface for each bushel of coal burnt in an hour, and in round numbers gave a duty of 1500 lbs. lifted a foot high to each foot of boiler surface. In words not technical, the heat from 1 lb. of coal gave steam that raised 460 tons weight of water 1 foot high.
The cylinder of this engine used the Watt steam-jacket. The Binner Downs engine was doing not one-half this duty, namely, forty-one millions; when brick flues were built around the cylinder, cylinder cover, and steam-pipes, and one or two fire-places, fixed near the bottom of the cylinder, of a size to conveniently burn 5 bushels of coal in twenty-four hours, the heat from which circulated through those flues on its way to the chimney, and increased the duty of the engine by one-half, raising it to sixty-three millions; in other words, during twenty-four hours of working, 67 bushels of coal in the boiler, and 5 bushels in the cylinder flues, did the same work as 108 bushels in the boiler without the cylinder flues, causing a saving of fifty per cent. by their use. Another startling fact was the greater effect for each foot of heating surface in the steam-cylinder flues than in the boiler flues; the latter gave a power of 1500 lbs. raised 1 foot high by a bushel of coal, while the former gave 6000 lbs. of power from the same amount of coal and heating surface.
Here was a mystery that Trevithick would not believe until he had seen it with his own eyes: he searched for it for a year or two, and overlooking the fact that the more simply arranged engine of his once pupil, Captain Samuel Grose, was doing more duty than the superheating steam-engine at Binner Downs, heworked at what seemed to be new facts, and converted them into a new engine.
We have traced how succeeding engineers tried to prevent loss of heat. Trevithick took the first bold step, and aiming at the same object, made the boiler the steam-jacket for the cylinder, and in his patent of 1802 went still further and protected the boiler from external cold, and thus describes it:—"The steam which escapes in this engine is made to circulate in the case round the boiler, where it prevents the external atmosphere from affecting the temperature of the included water, and affords by its partial condensation a supply for the boiler itself."[162]So that a quarter of a century before the date of those Binner Downs experiments he had patented an engine having neither cylinder nor boiler exposed to the cooling atmosphere. The flues around the Binner Downs cylinder were difficult of control. Trevithick says the piston packing had not been injured, showing that observers thought it would be, and even the cylinder was endangered, for the writer, who stoked those heating flues, recollects the fires burning very brightly in them. The ready transmission of heat through thin metal, used by Trevithick in 1802 for heating feed-water, and in the cellular bottom of the iron ship of 1808, serving as a surface condenser,[163]and his experience in 1812, that "the cold sides of the condenser are sufficient to work an engine a great many strokes without any injection,"[164]still followed up in 1828 by condensing steam without the use of injection-water, led to what is since known as Hall's surface condenser.
The following letter is in the handwriting of thepresent writer; it is the only one of Trevithick's numerous letters not written by himself:—
"Hayle,December 30th, 1828.""Mr. Gilbert,"Sir,—On the 28th inst. I received your printed report on steam, and have examined Farey's publication on sundry experiments made by Mr. Watt, which are very far from agreeing with the actual performance of the engines at Binner Downs. Mr. Watt says that steam at one atmosphere pressure expands 1700 times its own bulk as water at 212°, and that large engines ought to perform eighteen millions when loaded with 10 lbs. to the inch of actual work, the amount of condensing water being one-fortieth part of the content of the steam in the cylinder at one atmosphere strength, the cold condensing water at 50°, and when heated 100°. This would give for the Binner Downs engine, with a 70-inch cylinder, 10-inch stroke, 11 lbs. effective work on the inch (this load being one-tenth more than in Watt's table, by Farey, for an engine of this size and stroke), 57 gallons of injection-water for each stroke, and when working eight strokes per minute, to do eighteen millions would consume 11¼ bushels of coal per hour."Now the actual fact at Binner Downs, at the rate of working and power above mentioned, is that 3 bushels of coal per hour were burnt, using 13 gallons of injection-water at each stroke at 70° of heat, which was raised by its use to 104°, or an increase of 34°, which, multiplied by 13 gallons, gives 442. Mr. Watt's table for this engine and work gives 57 gallons of condensing water at 50°, heated by use to 100°. This 50° raised, multiplied by the 57 gallons of water, amounts to 2850, or six and a half times the quantity really used in the Binner Downs engine, and nearly four times the coal actually used at present. Mr. Watt further says that steam of 15 lbs. to the inch, or one atmosphere, from 1 inch of water at 212° occupies 1170 inches, and that steam of four atmospheres, or 60 lbs. to the inch, gives only 471 inches at a heat of 293°. Now deducting 50° from 212° leaves 162° of heat raised by the fire. Multiply 15 lbs. to the inch by 1700 inches of steam, and divide it by 162°, gives 138°, whereas if you deduct 50° from 293°, it leaves the increase of heat by the fire 243°. Steam of 60 lbs. to the inch multipliedby 471, being the inches of steam made by 1 inch of water divided by 243°, the degrees of heat raised by the coal, gives a product of 116; therefore, by Mr. Watt's view it appears that low steam would do one-fifth more duty than high steam, and yet Binner Downs engine in actual work performs about four times the duty given by Mr. Watt's theory and practice, with only one-sixth part of the amount of heat carried off by the condensing water, proving that high steam has much less heat, in proportion to its effective force; and this is further proved by the small quantity of condensing water required to extract its heat."Yesterday I proved this 70-inch cylinder while working with the fire-flues round it, which flues only consumed 5 bushels of coal in twenty-four hours. The engine worked eight strokes a minute, 10-feet stroke, 11 lbs. to the inch effective force on the piston; steam in the boiler 45 lbs. above the atmosphere, consuming 12 bushels of coal in four hours, using 13 gallons of condensing water at each stroke, which was heated from 70° to 104°; but when the fires round the cylinder were not kept up, though still having the casing of hot brickwork around it, and performing the same work, burnt 17 bushels of coal in the same time of four hours, and required 15½ gallons of condensing water, which was heated from 70° to 112°. You will find that the increased consumption of coal, by removing the fire from around the cylinder, was nearly in the same proportion as the increase and temperature of the condensing water, showing the experiment to be nearly correct."From the general reports of the working of the engines it appears that when the surface sides of the castings are heated, either by hot air or high steam, the duty increases nearly fifty per cent. from this circumstance alone."A further proof of the more easy condensation of high steam was in the Binner Downs 42-inch cylinder engine, 9-feet stroke, six strokes per minute, 11 lbs. effective power on each inch, burning 1-1/3 bushel of coal an hour. In this engine the proportion of saving by the heating flues was the same as in the large engine. I tried to condense the steam by the cold sides of the condenser, without using injection-water. Thewater in the condenser cistern was at 50°. After working for twenty-five minutes the small quantity of hot water discharged at the top of the air-pump reached 130° of heat, but then would rise no higher, the cold sides of the condenser being equal to the condensation of all the steam. The eduction-pipe and air-pump, with its bottom and top, gave 60 feet of surface sides of thick cast iron, and about 20 feet more of surface sides of a thin copper condenser; altogether, 80 feet of surface cold sides, surrounded by cold water. About half a pound on the inch was lost in the vacuum, the discharged water being 130° of heat instead of 100°. The vacuum was made imperfect by about 1½ lb. to the inch."It is my opinion that high steam will expand and contract with a much less degree of heat or cold in proportion to its effect, than what steam of atmosphere strong will do. I intend to try steam of five or six atmospheres strong, and partially condense it down to nearly one atmosphere strong, and then by an air-pump of more content than is usual to return the steam, air, and water, from the top of the air-pump, all back into the boiler again, above the water-level in the boiler, and by a great number of small tubes, with greatly heated surface sides, to reheat the returned steam; though by this plan I shall lose the power of the vacuum, and also the power required on the air-bucket to force the steam and water back again into the boiler, yet by returning so much heat I shall over-balance the loss of power, besides having a continued supply of water, which in portable engines, either on the road or on the sea, will be of great value."I shall esteem it a very great favour if you will be so good as to turn over in your mind the probable theory of those statements, and give me your opinion. If Mr. Watt's reports of his experiments are correct, how is it possible that the high-pressure engine that I built at the Herland thirteen years ago, which discharged the steam in open air, did more than twenty-eight millions? If you wish, I will send a copy of the certificate of the duty done by this engine, which states very minutely every circumstance. Now that cylinder, with every part of the engine, was exposed to the cold; had it been heated aroundthose surfaces, as on the present plan, it would have done above forty millions."Suppose the Binner Downs 70-inch cylinder engine, 10-feet stroke, working with full steam to the bottom of the stroke, when, by the experiment, the heated flues were again laid on would have worked one-third expansive, by the heat of 5 bushels of coal around the cylinder. Now one-third of the power would make a 3 feet 4 inch stroke, 11 lbs. to the inch effective power, eight strokes a minute, during twenty-four hours, by the consumption of 5 bushels of coal applied on the surface sides of the cylinder, performing a duty of 324 millions with a bushel of coal. Now suppose the cylinder without the heating flues had the steam cut off at two-thirds of the stroke, and that it is possible in a moment to heat the cylinder by the flues; in that case the steam would, by its expansion from the hot sides, fill the last third of the cylinder to the bottom of the stroke; then if that steam could be suddenly cooled, so as to contract it one-third, the piston would ascend one-third its stroke in the cylinder; and it appears in theory by this plan, that a cylinder once filled two-thirds full of steam, by receiving the heat on its surface sides from 5 bushels of coal, and again suddenly cooling down, would continue to work for ever, without removing the steam from the cylinder, and would perform a duty of 324 millions. This never can be accomplished in practice in this way, but the effect may be obtained by partially condensing in a suitable condenser, and again heating by hot sides."This mystery ought to be laid open by experiment, for what I have stated are plain facts from actual proofs, and I have no doubt that time will show that the theory of Mr. Watt is incorrect. Though there were 300 feet of cold sides, yet 200 feet were not condensing steam, because on the return of the piston, what was condensed below, and while the engine was resting, did not make against it more than what was condensed above the piston on its descent; therefore you may count on 150 feet of cold external sides constantly condensing, that made this third-part difference against the expansion of the steam."I remain, Sir,"Your humble servant,"Ricd. Trevithick.
"Hayle,December 30th, 1828.
""Mr. Gilbert,
"Sir,—On the 28th inst. I received your printed report on steam, and have examined Farey's publication on sundry experiments made by Mr. Watt, which are very far from agreeing with the actual performance of the engines at Binner Downs. Mr. Watt says that steam at one atmosphere pressure expands 1700 times its own bulk as water at 212°, and that large engines ought to perform eighteen millions when loaded with 10 lbs. to the inch of actual work, the amount of condensing water being one-fortieth part of the content of the steam in the cylinder at one atmosphere strength, the cold condensing water at 50°, and when heated 100°. This would give for the Binner Downs engine, with a 70-inch cylinder, 10-inch stroke, 11 lbs. effective work on the inch (this load being one-tenth more than in Watt's table, by Farey, for an engine of this size and stroke), 57 gallons of injection-water for each stroke, and when working eight strokes per minute, to do eighteen millions would consume 11¼ bushels of coal per hour.
"Now the actual fact at Binner Downs, at the rate of working and power above mentioned, is that 3 bushels of coal per hour were burnt, using 13 gallons of injection-water at each stroke at 70° of heat, which was raised by its use to 104°, or an increase of 34°, which, multiplied by 13 gallons, gives 442. Mr. Watt's table for this engine and work gives 57 gallons of condensing water at 50°, heated by use to 100°. This 50° raised, multiplied by the 57 gallons of water, amounts to 2850, or six and a half times the quantity really used in the Binner Downs engine, and nearly four times the coal actually used at present. Mr. Watt further says that steam of 15 lbs. to the inch, or one atmosphere, from 1 inch of water at 212° occupies 1170 inches, and that steam of four atmospheres, or 60 lbs. to the inch, gives only 471 inches at a heat of 293°. Now deducting 50° from 212° leaves 162° of heat raised by the fire. Multiply 15 lbs. to the inch by 1700 inches of steam, and divide it by 162°, gives 138°, whereas if you deduct 50° from 293°, it leaves the increase of heat by the fire 243°. Steam of 60 lbs. to the inch multipliedby 471, being the inches of steam made by 1 inch of water divided by 243°, the degrees of heat raised by the coal, gives a product of 116; therefore, by Mr. Watt's view it appears that low steam would do one-fifth more duty than high steam, and yet Binner Downs engine in actual work performs about four times the duty given by Mr. Watt's theory and practice, with only one-sixth part of the amount of heat carried off by the condensing water, proving that high steam has much less heat, in proportion to its effective force; and this is further proved by the small quantity of condensing water required to extract its heat.
"Yesterday I proved this 70-inch cylinder while working with the fire-flues round it, which flues only consumed 5 bushels of coal in twenty-four hours. The engine worked eight strokes a minute, 10-feet stroke, 11 lbs. to the inch effective force on the piston; steam in the boiler 45 lbs. above the atmosphere, consuming 12 bushels of coal in four hours, using 13 gallons of condensing water at each stroke, which was heated from 70° to 104°; but when the fires round the cylinder were not kept up, though still having the casing of hot brickwork around it, and performing the same work, burnt 17 bushels of coal in the same time of four hours, and required 15½ gallons of condensing water, which was heated from 70° to 112°. You will find that the increased consumption of coal, by removing the fire from around the cylinder, was nearly in the same proportion as the increase and temperature of the condensing water, showing the experiment to be nearly correct.
"From the general reports of the working of the engines it appears that when the surface sides of the castings are heated, either by hot air or high steam, the duty increases nearly fifty per cent. from this circumstance alone.
"A further proof of the more easy condensation of high steam was in the Binner Downs 42-inch cylinder engine, 9-feet stroke, six strokes per minute, 11 lbs. effective power on each inch, burning 1-1/3 bushel of coal an hour. In this engine the proportion of saving by the heating flues was the same as in the large engine. I tried to condense the steam by the cold sides of the condenser, without using injection-water. Thewater in the condenser cistern was at 50°. After working for twenty-five minutes the small quantity of hot water discharged at the top of the air-pump reached 130° of heat, but then would rise no higher, the cold sides of the condenser being equal to the condensation of all the steam. The eduction-pipe and air-pump, with its bottom and top, gave 60 feet of surface sides of thick cast iron, and about 20 feet more of surface sides of a thin copper condenser; altogether, 80 feet of surface cold sides, surrounded by cold water. About half a pound on the inch was lost in the vacuum, the discharged water being 130° of heat instead of 100°. The vacuum was made imperfect by about 1½ lb. to the inch.
"It is my opinion that high steam will expand and contract with a much less degree of heat or cold in proportion to its effect, than what steam of atmosphere strong will do. I intend to try steam of five or six atmospheres strong, and partially condense it down to nearly one atmosphere strong, and then by an air-pump of more content than is usual to return the steam, air, and water, from the top of the air-pump, all back into the boiler again, above the water-level in the boiler, and by a great number of small tubes, with greatly heated surface sides, to reheat the returned steam; though by this plan I shall lose the power of the vacuum, and also the power required on the air-bucket to force the steam and water back again into the boiler, yet by returning so much heat I shall over-balance the loss of power, besides having a continued supply of water, which in portable engines, either on the road or on the sea, will be of great value.
"I shall esteem it a very great favour if you will be so good as to turn over in your mind the probable theory of those statements, and give me your opinion. If Mr. Watt's reports of his experiments are correct, how is it possible that the high-pressure engine that I built at the Herland thirteen years ago, which discharged the steam in open air, did more than twenty-eight millions? If you wish, I will send a copy of the certificate of the duty done by this engine, which states very minutely every circumstance. Now that cylinder, with every part of the engine, was exposed to the cold; had it been heated aroundthose surfaces, as on the present plan, it would have done above forty millions.
"Suppose the Binner Downs 70-inch cylinder engine, 10-feet stroke, working with full steam to the bottom of the stroke, when, by the experiment, the heated flues were again laid on would have worked one-third expansive, by the heat of 5 bushels of coal around the cylinder. Now one-third of the power would make a 3 feet 4 inch stroke, 11 lbs. to the inch effective power, eight strokes a minute, during twenty-four hours, by the consumption of 5 bushels of coal applied on the surface sides of the cylinder, performing a duty of 324 millions with a bushel of coal. Now suppose the cylinder without the heating flues had the steam cut off at two-thirds of the stroke, and that it is possible in a moment to heat the cylinder by the flues; in that case the steam would, by its expansion from the hot sides, fill the last third of the cylinder to the bottom of the stroke; then if that steam could be suddenly cooled, so as to contract it one-third, the piston would ascend one-third its stroke in the cylinder; and it appears in theory by this plan, that a cylinder once filled two-thirds full of steam, by receiving the heat on its surface sides from 5 bushels of coal, and again suddenly cooling down, would continue to work for ever, without removing the steam from the cylinder, and would perform a duty of 324 millions. This never can be accomplished in practice in this way, but the effect may be obtained by partially condensing in a suitable condenser, and again heating by hot sides.
"This mystery ought to be laid open by experiment, for what I have stated are plain facts from actual proofs, and I have no doubt that time will show that the theory of Mr. Watt is incorrect. Though there were 300 feet of cold sides, yet 200 feet were not condensing steam, because on the return of the piston, what was condensed below, and while the engine was resting, did not make against it more than what was condensed above the piston on its descent; therefore you may count on 150 feet of cold external sides constantly condensing, that made this third-part difference against the expansion of the steam.
"I remain, Sir,"Your humble servant,"Ricd. Trevithick.
The writer's note-book used during those experiments is in his possession, as well as Trevithick's note-book giving particulars of experiments at several mines, from which the following extracts are taken:—