Life of Richard Trevithick by F. Trevithick: Volume 1: Chapter 12
From Graces Guide
CHAPTER XII. THAMES DRIFTWAY.
When Trevithick was dredging in the Thames, the Thames Archway Company were anxiously seeking new plans and a new engineer; not being satisfied with the proposals of Mr. Rennie and Mr. Chapman they sought out Trevithick, who soon found himself in a position most trying, and unsuitable to his energetic temperament.
At an annual meeting of the proprietors on the 4th of May, 1808, the directors refer to their second meeting in June, 1805 That it appears to this meeting that the well constructing the driftway is of the highest importance in the future progress of the works, involving in it the success or failure of the undertaking.
That, therefore, the works relating to the driftway be suspended until the opinion of a professional man of eminence be taken on the various matters respecting it.
Mr. Rennie and Mr. Chapman were accordingly consulted; but as their opinions did not coincide, nor indeed were stated upon all the points on which the directors chiefly wished for information, they felt themselves bound to resort to some other source; and Mr. Trevithick was introduced to them by their resident engineer, Mr. Robert Vazie, as a person skilled in mining. After a due examination into his character, as appears by the minutes of the directors, and having received the strongest testimonies in his favour from several quarters as to his skill, ingenuity, and experience, the directors were induced to contract with him for superintending and directing the execution of the driftway, such as he proposed it to be; for which they agreed to pay him £1,000, provided he succeeded in carrying it through to the north shore; or £500 if the directors ordered it to be discontinued in the middle, which they reserved to themselves the power of doing; but to receive nothing in case he did not succeed.
The driftway was accordingly commenced on the 17th of August.
On the 5th of September following Messrs. Vazie and Trevithick, in a joint report to the directors, strongly recommended the immediate purchase of a 30-horse-power steam-engine. The directors did accordingly purchase the same, and it is now ready to work. The driftway proceeded till about the beginning of October, when it appeared that the works had been very considerably interrupted and delayed in their progress. The directors therefore, on the 8th October, resolved to institute an inquiry into the cause; and the consequence of this investigation and disclosure of facts was the removal of Mr. Robert Vazie from his office as resident engineer, on the 19th October, by which time the drift had been extended 394 feet, that is, at the rate of 6 feet 2 inches per day, through a dry sand.
The works now proceeded without embarrassment, and with considerable less cost as from this time (the 19th October) to the 29th November, the ground continuing as nearly as possible of the same quality, it was extended 421 feet, or 11 feet 2 inches per day, which is nearly a double rate (deducting three days and a quarter that the works were suspended while the directors determined on the turn the drift should take).
From the 29th November to the 19th December the drift was extended only 138 feet, or 6 feet 10 inches per day, in consequence of the drift now running in a stratum of rock, great part of which was so hard that it could not be broken up without the use of chisels and wedges.
By the 21st December the drift had proceeded 947 feet from the shaft; and it was observed that the strata through which it passed dipped to the northward about 1 foot in 50, in consequence of which the rock that at one time formed the whole face of the breast, now only reached within 2 feet of the top, and which was occupied by a sandy clay, mixed with oyster and other shells, and containing some water.
On the 23rd, notwithstanding the workmen were proceeding with the utmost precaution, the roof broke down and discharged a great quantity of water from a quicksand, which was afterwards ascertained to be about 5 feet 6 inches above the roof.
By the 26th January the drift was extended 1,028 feet, having been worked through a considerable part of the quicksand; and at this period the river made its way into the drift by a fall of earth, which made a considerable orifice in the bed of the river, which has been filled up at several times with earth, carried there for that purpose, and the drift has since then been extended to 1,040 feet, which is the present length of it.
Resolved, that the money paid or claimed by the engineers, Mr. Rennie, Mr. Wilcox, Messrs. Stobart and Buddle, Mr. Thomas Cartwright, Mr. James Barnes, and Mr. William Chapman, whom the directors have consulted with as to the prosecution of the works, be allowed.
Resolved, that Mr. Richard Trevithick be, and is hereby appointed engineer to the said company, and be directed to proceed forthwith with the works.
At the second meeting of the proprietors in 1805 differences had arisen between the directors and their engineer, Mr. Robert Vazie, on the method of constructing the driftway. Mr. Rennie and Mr. Chapman were called in to advise a plan for the guidance of the directors. Their advice was not approved of and after much delay Mr. Vazie introduced to their notice Mr. Trevithick as a skilful miner and engineer. This was about the middle of 1807. On the 10th August 1807, the directors engaged with him to make the proposed driftway from the south shore of the Thames, at Rotherhithe, to half-way across the river, from which central point it was contemplated to commence forming the permanent tunnel, of the size to be then determined, either for foot-passengers alone, or if the nature of the work gave promise of success, to enlarge it sufficiently for the passage of carriages.
August 11th, 1807.
Sir, Last Monday I closed with the tunnel gents. I have agreed with them to give them advice, and conduct the driving the level through to the opposite side (as was proposed when you attended the committee); to receive £500 when the drift is half-way through, and £500 more when it is holed on the opposite side. I have written to Cornwall for more men for them. It is intended to put three men on each core of six hours' course. I think this will be making £1,000 very easily, and without any risk of loss on my side. As I must be always near the spot, to attend to the engines on the river, an hour's attendance every day on the tunnel will be of little or no inconvenience to me. I hope nine months will complete it. From the recommendation you gave me, they are in great hopes that the job will now be accomplished; and as far as Captain Hodge and myself could judge from the ground in the bottom of the pit, there is no doubt of completing it speedily. I am very much obliged to you for throwing this job in my way, and shall strictly attend to it, both for our credit as well as for my own profit.
I am, sir,
Your very humble servant,
Within a week of his engagement he had commenced the driftway. The sinking of the shaft on the south shore, from the bottom of which the driftway was to commence, was the extent of progress during the two or throe years before Trevithick's appointment. It was 68 feet 4 inches in depth from the surface; a wooden platform a slight distance above the bottom of the shaft served to form a reservoir for the drainage water from the drift, from which it was pumped to the surface by a steam-puffer engine. The bottom of the drift was even with this platform. In size it was sufficient only for the passage of a workman with his barrow, being 5 feet high, 3 feet broad at the bottom, and 2 feet inches at the top, inside measurements; the four sides were kept in form by woodwork and strong 3-inch planking. The working end required great care, and frequently the application of close planking across the end or face of the work to prevent a sudden fall of water and sand. As the drift proceeded the increasing quantity of water and earth or sand to be raised to the surface led the two engineers, Vazie and Trevithick, to make a joint report recommending a 30- horse-power steam-engine. Before two months had passed, this joint engineering broke down, and Trevithick was left to carry out his own plans on the work, but subject to annoying remarks from without.
The drift progressed at the rate of 6 or 10 feet daily, and in a little over four months, or up to the 21st December, it had advanced 947 feet, being more than three-quarters of the whole distance, and within about 200 feet of high-water mark on the north side.
August 28th, 1807.
Sir, Tuesday last was a week since we began to drive our level at the bottom of the engine-shaft at the archway.
The level is 5 feet high, 3 feet wide at the bottom, and 2 feet 6 inches wide at the top, within the timbering.
The first week we drove 22 feet. This week I hope we shall drive and timber 10 fathoms. As soon as the railway is laid I hope to make good 12 fathoms a week. The distance we have to drive is about 188 fathoms. The ground is sand and gravel it stands exceedingly well, except when we hole into le-areys, and holing into such houses of water makes the sand very quick. We have discovered three of these holes which contained about 20 square yards.
It is very strange that such spaces should be in the sand at this depth. When we cut into such places we are obliged to timber it up closely until the sand is drained of the water, otherwise it would run back and fill the drift and the shaft.
I cannot see any obstacle likely to prevent us from carrying this level across the river in six months. The engine throws down a sufficient quantity of air; and the railway underground will enable us to bring back the stuff, so as to keep the level quite clear, and the last fathom will be as speedily driven as the first. There is scarcely any water in the level — not above twenty gallons per minute — and not a drop falling from the back of the level (the end). Therefore, I think we may expect that the land-springs will not trouble us.
The spring that came down around the outside of the walling of the shaft is rather increased. The directors are in wonderful spirits, and everything goes on very easily and pleasantly. The engines on the river go on as usual.
I remain, Sir,
Your very humble servant,
Plough Inn, Kidney Stairs, Limehouse.
P.S.— The 2-inch iron air-pipes that were provided before I took the work in hand are too small. The smith's bellows has nearly two hundredweight on the top plank, yet at the bottom of the shaft it will scarcely blow out a candle. I shall put down larger pipes next week.
It is remarkable that in 1807 Trevithick familiarly spoke of a railway in connection with underground work, and of supplying miners with pure air by the use of the steam-engine, while in 1870 we talk of enforcing the latter by Act of Parliament.
September 12th, 1807.
Sir,— This day I received yours, and am very much obliged to you for your attention to my welfare. Last week we drove and secured in the tunnel 25 yards, and I see no doubt of getting on in future with the same speed. We are now about 180 feet from the shaft, and as we approach the river the ground is better, and the water does not increase; but to be prepared for the worst, it is agreed to have a 30-horse-power engine in readiness, to assist in case of cutting more water than the present engine can cope with.
The distance from the shaft to the spot on the opposite shore, where we intend to come up to the day, is about 1,220 feet. This distance I hope to accomplish in a short time, unless some unfavourable circumstance turns up, which at this time there is no sign of. Should the ground prove softer we can drive horizontal piles; should the water increase we shall have three times the power in reserve as we now occupy.
The directors are highly pleased with our present proceedings. In consequence of this job 1 have been called on to take the direction of a very extensive work, the nature of which I am not yet fully informed; but am to meet the party on Thursday next for further information, when I shall communicate the plan to you for your investigation; at the same time I must beg your pardon for so often troubling you on matters that cannot advantage you, and hope you will excuse my freedom, being driven to you as a source of information that I cannot be furnished with from any other quarter.
The engines continue to get on as usual on the river. The great engine is not yet at work; but hope it will soon be completed.
I remain, Sir,
Your very humble servant,
Plough Inn, Kidney Stairs, Limehouse.
In the midst of hoped-for success, a special meeting of proprietors was held on the 24th December, 1807, and it was put to the meeting that Mr. Trevithick does not possess the confidence of the company, and that the directors be requested to put an end to all engagements with him. The proposal was negatived by 137 against 61; the directors supporting their engineer. The continuance of this opposition (this was the second time this question was discussed during the four months) not only diverted the attention of the directors from the daily consideration of the progress of the work, but roused Trevithick's naturally impetuous action to drive ahead for the other shore.
The drift had been carried on a level line front the shaft until past the middle of the river, to facilitate drainage, when it ascended at about the same slope as the river-bed towards the northern side, the roof of the drift being about 30 feet under the bed of the river. The strata passed through from the shore to the middle was firm sand and gravel, while for the last 200 feet it had been rocky. This strata of rock had been seen in the shaft on the south side 7 feet 6 inches thick, and was known to dip going north about 1 in 50. While the driftway was under it, it helped to keep the water out and gave firmness to the ground but as going north it was deeper below the surface than on the south side, and as the driftway had to rise to the surface within a certain distance from high-water mark on the north side, it had of necessity to pass through this strata of rock. The rise of the drift was then about 1 in 9. The strata of rock had been cut through on the 21st December. The face or breastwork at the end showed that the lower half or bottom of the drift was still in rock, while the upper half or roof was in treacherous quicksand.
Then was the time for calm and thoughtful consideration of evidences in the drift by the directors, when a wise word would have averted failure and secured success. Unfortunately the directors were occupied in preparing to meet the dissatisfied proprietors at the special meeting to be held within three days; the drift followed its doomed course for two more critical days, when on the 23rd the water and quicksand rushed in, in spite of every precaution; and the next day, the 24th December, the directors, who should have been in quiet consultation at the driftway, were in noisy dispute with their opponents at the 'George and Vulture' tavern, Cornhill.
There is no trace of wise retreat under the shelter of the rock — in which course another 100 feet would have brought them beyond low-water mark on the south shore - except in the drawing made by Trevithick, showing a test-hole bored through it and strata above, just before reaching the point where the fatal rock was cut through. He calls it the test-hole, and says, "The stratum of sand with water showed that the break was the consequence of not boring in time. The Boyer hole near the shaft on the south shore, made by Robert Vazie, shows the evil consequence of communicating the two springs."
From Trevithick's words in his own writing there is no doubt that he feared to break through the rock, and foresaw the rush of sand and water as in the earlier experiment in the shaft. His opponents used this breakdown as an additional reason for his dismissal.
December 30th, 1807.
DAVIES GIDDY, ESQ.,
Sir,— Your politeness in answering my inquiries respecting Mr. Trevithick's engines some time ago, emboldens me to request a further favour of you, relating to that gentleman. Since the directors of the Thames Archway Company contracted with Mr. T. to execute the driftway, he has had the misfortune to incur the displeasure of a considerable proprietor (not a director), and who has had influence enough, by partial representations indefatigably urged, to form a strong party against him, so much so that a special assembly of the company was convened by this proprietor and his friends, for the special purpose (as it turned up in argument) to throw a degrading stigma on Trevithick's character, not only as an incompetent miner and engineer, but as a man of integrity; and indirectly to censure the directors for employing him. A resolution was proposed by this gentleman that Mr. T. does not possess the confidence of the company, and that he be discharged from all his engagements with it. Though the author of this proposition was induced by the sense of the company to withdraw it, yet his assertions, which were very bold and numerous, and unsupported by his facts, seemed to retain their weight on the minds of his own party, notwithstanding the folly and weakness of the proposition; folly, because Trevithick could not legally be discharged, and wicked, because if he could have been, it must have been by a breach of honour and good faith in the directors, to the great injury of Mr. Trevithick.
Among the assertions of the proprietor alluded to, he represented that T. had imposed on the directors by magnifying beyond the truth the importance of his engagements in other objects, so as to induce the directors to believe that they could only secure his services by a bargain extravagantly favourable to him, and that all his representations to this effect were false in fact. Although the directors declared that these circumstances had no influence on their minds in making their contract with T., which they considered fair and reasonable, and do still, yet it seems highly desirable now, to the vindication of Mr. T.'s moral character, so grossly attacked, that some evidence be adduced at a future opportunity of the existence of some of those engagements which Mr. T. did certainly mention; and as I think you stated to the directors your knowledge or belief in some of them, it would be highly pleasing to me, and I believe to every other director, if you would take the trouble of informing me what you know or recollect about them.
It was said that he had represented himself to have large concerns or engagements in Cornwall, or in the neighbourhood of Bristol, an engagement with the Trinity House for raising ballast, and an offer of some engagement of importance with a Mr. Trotter. It was roundly asserted by the said proprietor that Trevithick had no foundation whatever for these representations. Speaking of him as an engineer, he treated him in the most degrading terms, and as a miner, a very quack.
Notwithstanding the directors have had no reason in any instance whatever to change the very favourable opinion they formed of him, at your recommendation, yet, sir, it would he eminently satisfactory to them to be able to refute, by such respectable evidence as yours, at some future period, those base calumnies attempted to be cast upon him — certainly in no respect justified by his conduct; and as I recollect you spoke of him in very flattering terms as a miner and engineer of great skill and experience, and as a man of great integrity, I venture to hope that you will indulge me with your candid opinion of him on all these points, as well for the sake of my own and co-directors satisfaction, as for doing justice to a man against whom a very illiberal attack has been made, and which if not refuted may very sensibly affect his future comfort.
I have the honour to be, Sir,
Your very obedient servant,
P.S.— The particulars of the observations made at the meeting on Mr. T. are not known to him, nor is he acquainted with this letter to you; but he has informed me that Mr. Robert Vazie once addressed a letter to you respecting him, and of your favourable answer. If you will have the goodness to favour me with copies of these, they may be used very advantageously in favour of Trevithick.
Mr. Wyatt was one of the few appreciative men that now and then crossed Trevithick's troubled path.
January 5th, 1808.
Sir, About ten days since I received your letter, which was wrongly directed, and did not come to me in due course. I have sold the ballast business to a company, which is carrying it on. I should have written to you on the receipt of your letter; but at the time it arrived we were in a quicksand, and I wished to get through it before writing. The drift is driven 952 feet from the shaft, and is about 140 feet from high-water mark on the north side of the river, and hope to be through in a fortnight. Some weeks we drove 20 fathoms; but for fifteen or twenty days before we met the quicksand we had a very hard lime rock, which much impeded us. During the last fortnight scarcely anything has been done in the end on account of the quicksand; but now we are again in a strong clay ground, and getting on quickly. The drift is 72 feet below high-water mark. When we commenced to drive from the shaft it was a firm green sand; soon a bed of gravel of about 8 inches thick came down from the back. As we drove north we found all the strata dip about 1 foot in 50. On the top of the gravel there is about 3 feet of clay, then a limestone rock (made from water) about 5 feet thick. It is evident that this is a made rock, because the green sand that we began to drive in is several feet under the rock, and there is a large quantity of branches of trees in it turned into stone. On the top of the rock there is a proper bed of oysters, mud and oysters about 2.5 feet thick. Above this is about 5 feet of clay mixed with sand; above that is the quicksand of 22 feet thick; and above that is a strong dry clay, which we suppose holds up to the bottom of the river, which is about 20 feet. We bored on the north side, and found this quicksand was above the back of the drift, and a great quantity of water in it.
I proposed to bore up in the back of the drift, to tap it and let down the water gently through an iron pipe, but I could not be permitted.
In course of working in the drift the water and quicksand broke down in the back of the drift, drowned the engine, and threw a great quantity of sand down into the drift. This sand is nearly as fine as flour, and when in water is exceedingly quick. We had the good fortune to stop up the drift tight with timber before the water got up to prevent us, and we have drained the sand, so that the engine is again complete master of it. I had a machine made to drive very long flat iron bars close up to the back of the drift, through the stopping boards in the end and then cleared out the drift under them, and timbered very closely under the bars. By driving a great number of bars of iron I again reached the end of the drift, which is now again in good course for driving. After we had stopped the end of the drift to prevent the quicksand from coming back, I bored 14 feet up in the back of the level, and forced up a 2-inch iron pipe above the quicksand, which prevented the quicksand from coming away with the water, and also took off the weight or pressure of water from the breaking ground in the back of the drift.
It was strongly proposed by one of the proprietors (when the drift was half-way in) to open out from that place the tunnel to 16 feet high and 16 feet wide. I refused to do it, knowing that this water and quicksand was over our head, and that as soon as we began to incline the bottom of the drift up toward the surface on the north side we should be into it. It was with the greatest difficulty that we could stop it in the drift, only 22 feet wide and 5 feet high.
Had we opened the tunnel to the full size, every man that might have been underground at the time most have been lost, and the river through into the tunnel in ten minutes, for the water would have brought the 2.5 feet stratum of quicksand into the tunnel, and then the clay roof would have sunk under the weight of the river; for it would have been impossible to stop it over a space 16 feet high and 16 feet wide; the engine would have been drowned in one minute, and the sand would have constantly come away until the roof fell through into the drift.
This proprietor has been very much exasperated against me ever since, because I would not open out the tunnel from the middle of the drift up to the full size. This gent was never in a mine in his life, neither does he know anything about it. He called a general meeting to discharge me, but he was taken no notice of, and the thanks of the meeting given to me for my good conduct, and his friend Mr. Vazie discharged. They have offered the £1,250 more for my attendance, to open the drift up to the full size of the tunnel, and wish me to, engage with them immediately, before the first contract expires.
The quicksand when drained is very hard, and after the drift is through the ground it will be so completely drained that I cannot see any risk in opening to the full size.
When you come to town I shall have several things to lay before you, and shall be very much obliged to you to say when you expect to be here.
I am, Sir,
Your humble servant,
In Trevithick's time geology had not become a familiar study, and probably he had never read a page on the subject: yet his reasoning is simple and logical; for the infiltrated limestone rock, "made from water," resting on a strata having in it branches of trees, was a proof that it was not an original limestone rock.
The propriety of forcing an iron pipe from the roof of the drift up into the top of the bed of quicksand for the purpose of drawing off the water was evidently a much-disputed point, and was carried against Trevithick, though after the water had forced its way into the drift his drain-pipe was approved of, and was used by him and others but the strata had then become broken, and the pipe less effective than it might have been at an earlier period. Trevithick has been called an obstinate man because of his improper use of this drain-pipe, but this letter proves quite the contrary, for it shows that he obeyed orders, and without a tinge of recrimination.
By a continuous working of the extra pumping engine which he had provided at the shaft in case of such an emergency, the water and sand were so far cleared out of the drift that men could go in. How were the numerous inpours of water and sand through every crevice to be stopped? The timbering at the top of the end was the most leaky; but in the cramped width of 2.5 feet it was impossible to remove and replace timbers with celerity. Iron plates were therefore driven through the stopping boards, close to the roof, in the end of the drift, into the disturbed strata, forming a roof of iron. This enabled the wood end to be moved, and to be advanced without bringing down the roof. Unfortunately the machine invented and made for driving those bars is not described.
He was also right in declining to undertake to enlarge the drift when half-way through, as proved by the great difficulty afterwards experienced by Mr. Brunel in driving the larger tunnel. The object was to perfect the drift that it should serve as a drain to free the larger tunnel from water during its construction, as well as a means of knowing the strata. By the 26th January, 1808, in a month's work since leaving the rock strata, they had only advanced 81 feet when the water and sand again rushed in in such increased quantities through the openings for advancing the end or breast-work, that the workmen could no longer resist it, and with difficulty reached the shaft, with but just sufficient space for breathing room between the surface of the rising water and the roof of the drift. Trevithick was one of the lot; and as the water filled the drift and rose in the shaft, the miners floated with it until rescued. Mrs. Trevithick spoke of her husband coming home through the streets without hat or shoes, half drowned, and covered with clay and dirt, but not discouraged by this first really serious breakdown, the drift being 1,028 feet in length. The driftway and shaft were filled with water and sand, and the bed of the river, 30 feet above it, sank into a dish form over the hole, from the quantity of sand carried by the rushing water into the drift; causing the thick strata of clay forming the bed of the river to sink more and more. A crack or hole through this clay would be fatal, therefore more clay was thrown into the river, to fill the hollow and prevent if possible any communication between the water and the beds of quicksand surrounding the drift. A large canvas sheet loaded with clay, and bags filled with clay, were also thrown on to the river-bed.
The following shows that even then he was sanguine of success:
February 2nd, 1808.
Sir, I have been for some time expecting a note from you, of your arrival, which is the reason for not having written to you long since. I am glad to find that both you and the old gentleman enjoy good health. I enjoy the same; but have a great deal of exercise both of body and mind about this job here.
Last week the water broke down on us from the river, through a quicksand, and filled the whole of the level and shaft in ten minutes. I have stopped it completely tight, and the miners are at work again. We are beyond low-water mark on the north side with the drift; if we have no further delays we shall hole up to the surface in ten or twelve days. I cannot give you as full a description, by the pen, as I wish; but will see you on Friday morning.
On Thursday, at twelve o'clock, there will be a meeting of the directors, on the spot. If they knew you are in town, you would be pressed very hard to attend. If you can attend I shall be very happy to see you on the spot, as I have a great deal to communicate to you. I have no doubt of accomplishing my job.
I am, Sir,
Your humble servant,
The discontented proprietors had now a real cause for talking, and made such a stir as reached the ears of the Lord Mayor, who accused the headstrong engineer of making a great hole in the bed of the river; and then the tide turned, and he was charged with forming a great bank in the river. The Lord Mayor laid an embargo of pains and penalties on all and every who should interfere with the river-bed without his permission and being dutifully asked, allowed the engineer to proceed. Trevithick struggled on slowly, and, at imminent risk of health and life, forced the drift forward 1,000 feet from the shaft, that narrow passage being the only means of escape, should any one of the numerous bits of planking break away and allow the inrush of sand and water. This was enough to prevent ordinary men from going on; and in addition was the impure, dull, unchanged air in that wooden drain, in which the dim light of a candle that could scarcely be kept burning, and the constant drip of water, where the workmen could never stand erect, or squeeze past one another without difficulty, and could only work one at a time in the narrow end, were more than sufficient to daunt the most determined.
Iron pipes were driven through the roof into the sand-beds, in the hope of drawing off the water; but they became choked with clay, and the slightest opening in tile planking of the end was followed by a rush of sand and water. Only 70 feet remained between the end and low-water mark on the opposite or north shore: a small barrier which was fated to be impassable. The directors stopped all proceedings, and considered what should next be done. Trevithick supplied the following plan and opinion: the Plate is copied from his original drawing, except that, for want of space, only the part bearing on the stoppage is shown. His plan, some 5 feet long, gives the whole length of the work.
This proposed plan (Plate IX.) for enabling the drift to be continued illustrates his genius; for he had never been taught to deal with river-beds, yet principles are here introduced which have since been largely applied, and spoken of as modern discoveries.
The day following the date of Trevithick’s last note to Davies Gilbert (then Giddy), another inrush of water and sand prevented progress. The drift, 1,028 feet in length, was through a considerable portion of the bed of quicksand, when a fall of earth in the roof filled the drift with sand, clay, and water, causing a sensible orifice in the bed of the river. Trevithick persevered, and again draining the drift, forced his way forward another 14 feet, making a total length of 1,040 feet.
The proprietors called a meeting, and desired two engineers to examine and report, and also to act.
Trevithick recommended a wood caisson filled with clay, with a wooden shaft through it, to be placed over the sunken hollow in the bed of the river, the shaft, to be carried down to the roof of the drift; another wooden shaft, hooped with iron was also to be sunk through the bed of the river, a little in advance of the end of the drift, to facilitate the carrying the drift through the remainder of the quicksand.
Directors, proprietors, and engineers were now at variance, and from a meeting of directors on the 12th April, 1808, the following particulars were sent to each proprietor:—
Since the removal of Robert Vazie from the office of resident engineer to the Thames Archway Company, several proprietors in that concern have expressed their dissatisfaction at the proceedings of the works under Mr. Trevithick, and have taken many steps to impede their progress and darken Mr. Trevithick's reputation; yet, as no act of Mr. Trevithick's incompetency was ever shown, though many were falsely alleged, and as the directors never observed any instance either of neglect or want of skill in him, but that on every occasion where his knowledge, his intelligence, and experience in his profession were questioned and examined by competent persons, his talents appeared very superior to the common level, the confidence which the directors reposed in him was not shaken. But the directors, upon the suggestion of the dissatisfied proprietors, and with a view to gratify their wishes, consented on the 29th February, 1808, to apply to two professional miners of high reputation in the North of England, approved by themselves, to come and examine the state of the works. These gentlemen, namely, Mr. William Stobart, of Lumley Park, Durham, and Mr. John Buddle, of Walls' End, Newcastle-upon-Tyne, arrived in London on the 5th instant, and inspected the works on the 7th; and on that day attended a meeting of the directors, when the written questions hereafter stated were delivered to them for their consideration and answers; and the meeting of the directors being adjourned to the 9th instant to receive the answers, those gentlemen attended on that day, and delivered to the Board their answers in writing.
I extract only those portions bearing directly on Trevithick and his acts.
2nd. - Do you approve of the methods he has pursued for stopping the water from the river?
We do approve of the methods Mr. Trevithick has pursued of stopping the water from the river.
4th. — Do you approve of sinking a shaft, as proposed by Mr. Trevithick, for securing the ground injured by the fracture in the bed of the river or would you advise any other method?
Taking all the circumstances into consideration, we do not think that any better plan can be adopted for the security of the ground injured by the fracture in the bed of the river, than that suggested by Mr. Trevithick.
11th.— Is it your opinion that this fracture has been occasioned by any unskilfulness on the director of the works, Mr. Trevithick?
This fracture, in our opinion, has not in any degree been occasioned by the unskilfulness of the undertaker, Mr. Trevithick, although we might have recommended a continuance of the drift in a horizontal direction for about 140 feet farther, previous to the commencement of its ascent. We might have recommended this 140 feet additional, only to have given equal width between the drift and the river; but, if this had been done, the tunnel itself must have been so much longer, or else the rise quicker in proportion.
12th.— Have you in any part of the works discovered a want of knowledge and intelligence in Mr. Trevithick in the business of this undertaking?
No part of the works, in our opinion, exhibits any want of knowledge or intelligence in Mr. Trevithick in the business of this undertaking. As a practical miner, this work does credit to any man who has performed it; and he has great merit in the performance, and need not be afraid of anyone viewing the work.
"17th.— From what you have observed of Mr. Trevithick, on this occasion, are you of opinion that he is a proper person to conduct the undertaking?
We have not the least hesitation in saying that he is. He has shown most extraordinary skill and ingenuity in passing the quicksand and we do not know any practical miner that we think more competent to the task than he is. We judge from the work itself, and until this occasion of viewing the work, we did not know Mr. Trevithick.
18th.- Do you approve of the borings which Mr. Trevithick made in the roof of the drift; and putting up the pipes to draw off the water?
It was the most judicious method he could pursue.
After perusing the opinion of men of such eminence in their profession as Messrs. Stobart and Buddle, the directors, whose confidence in Mr. Trevithick has been unvaried, made no doubt that the proprietors at large, whose minds are not infected by prejudice or invidious motives, will concur with them, that that confidence was not only well founded, but that Mr. Trevithick's character stands even higher in his profession than their discernment of his merits had led them to judge of him.
Not only did a Member of Parliament, highly respected for the purity of his conduct and scientific requirements (Mr. Davies Giddy), attend the Board of Directors, and give so high a character of Mr. Trevithick, both as to his talents as a miner and integrity as a man, that not a single director hesitated on that head, but also, a proprietor, Mr. Butt, who is a distinguished individual of the discontented party, did himself bring to the Board, from another quarter of great respectability, a report as favourable to Mr. Trevithick as that given by Mr. Giddy.
The directors received these opinions of Messrs. Stobart and Buddle on the 7th April, 1808, and directed Mr. Ryan to make borings on the north shore; but being still in doubt, on the 19th April sought advice from Mr. Charlton, from whose report a few questions and answers are selected to show the confusion of management.
3rd. Do you conceive that the drift corresponds with the plans?
Yes; I see nothing to the contrary.
4th.— Is the drift made in such a way as you would have advise?
For a temporary drift it is.
5th.— Is it carried on in such a way as you would have advised as to its level and distance from the river?
Any man would naturally take it as near the river as he could with safety, and I would have advised it.
8th.— Whether you would have advised making a drift in the way this has been done, for the purpose of enlarging that drift to the extent of 11 or 12 feet diameter?
I would not; it is my opinion that you should have finished as you went on.
9th.— Whether you would advise in the present state of the drift to continue it to the north side, or abandon it and make another drift?
I think that as it is gone so far, if it was driven through it would give great advantage for air, and convenience for bringing out and taking in materials, and safer for the workmen, and therefore I would advise it to be carried through.
15th. Would you advise the borings that are now making to be completed?
Resolved, from the evidence adduced at this meeting, that Mr. Trevithick was acquainted with the borings already made in the north shore of the river, notwithstanding the representation to the contrary appears in Mr. Braithwaite's report.
At a meeting of directors on the 21st April, 1808:—
Resolved, that the borings on the north side of the river be discontinued till further orders, and that notice thereof be given to Mr. Rastrick.
At a meeting of directors, 9th May, 1808, Mr. Trevithick attended this meeting and stated that the new engine was completed and at that work; and he now thought it prudent to attempt proceeding with the drift, previously to sinking a caisson, as he expected to get through the quicksand, after proceeding with the drift 5 or 6 feet farther.
Resolved, that Mr. Trevithick be directed to open the breast, and proceed with the drift without delay. Mr. Trevithick delivered to this meeting the following claim upon the company, for the time he has lost since the works were last suspended, namely, thirty-four days at two guineas per day.
Resolved, that the consideration of the above claim be suspended for the present.
At a meeting of directors on the 16th May, 1808, Mr. Trevithick attended, and delivered the following report:— "On opening the breast this week we found the wood piles rather loose, which were driven up and fastened after which the miners attempted to proceed, but were driven back several times by water and sand. Opened several old pipes that were put in the roof, out of which water flowed strongly leaving the breast; this enabled the miners to proceed 22 inches.
At a meeting on the 6th June, 1808, Mr. John Rastrick's report is received by the directors:—
Your workmen were employed last week in taking up 40 tons of clay and gravel, which formed a ridge on the bed of the river, and in putting a sail over the broken ground, getting, loading, and unloading 160 tons of clay, which clay covers the sail about 3 feet thick. The drift is quite clear of sand up to the door; which door is 18 feet from the face, and is full of sand. The water at the tin and door flows strong and clear.
Resolved, that Mr. Trevithick be directed to put the old engine in repair.
In June, 1808, Mr. Rastrick was the engineer of the driftway, and on the 11th made a report to the directors:—
Monday, men were employed in driving iron piles, and loading a barge with clay.
Tuesday, boring a hole 98 feet south of the incline: this pipe, like all the former ones, discharged water free of sand for half an hour, during which time the end was dry, when the sand flowed and plugged up the pipe. The rock at this hole is 5 feet thick.
Wednesday, boring a hole 109 feet south of the incline, out of which we could get no water, though it was bored 16 feet high. Opened pipe 98 feet south of the incline; this eased the breast, and miners proceeded in driving piles. They had not been above half an hour at this work before the pipe stopped, and sand and water flowed strong through pipe 109 feet.
Thursday, miners opened the above pipes, which, as before, discharged sand and water; plugged up, and opened the breast, which appeared favourable, but as soon as the first pile was driven, the whole of the piles came back about an inch and half. Secured the breast and left the drift.
Friday, opened the hole 109 feet, and put up pipes 3 feet long, making pipes in this hole 15 feet. Water flowed strong and clear for two hours, during which time miners opened breast and drove piles, after which sand flowed very strong through the pipe; plugged up, and left the drift.
Saturday, bored a hole 173.5 feet south of the incline. This hole was bored 19 feet high, through which the sand flowed very strong; plugged up, and drove four iron plates in the breast 18 inches long and 10 inches broad.
Sunday, opened breast, cut out piles, and prepared for a set of timbers. At this moment the piles appeared loose; sand and water flowing strong out of the bottom of the drift, about 8 feet from the end. Secured breast, caulked the joints, and left the drift.
Without attempting to define Trevithick's position during this knocking together of heads of eminent engineers, directors, and shareholders, it is evident that for two or three months Mr. Rastrick had power to act, closing his short authority by the significant words, "secured breast, caulked the joints, and left the drift."
Mr. Rastrick and other engineers acted on Trevithick's plans without even suggesting any particular change. They would scarcely have been employed, except on the understanding that they could do Letter than Trevithick; yet they made no progress, and admitted that he was the only man for the work.
During this short respite from daily attendance on the driftway, Trevithick had constructed the first London railway, and had conveyed or was about conveying the first railway passenger train by the locomotive ‘Catch-me-who-can.' The drift having been idle for nearly two months, Trevithick recommended a new plan, and a special meeting for its consideration was called.
THAMES ARCHWAY, ROTHERHITHE,
July 28th, 1808.
Sir,— I have yours of the 24th, and intend to put the inscription on the engine, which you sent to me.
About four or five days ago I tried the engine, which worked exceedingly well, but the ground was very soft, and the engine (about eight tons) sunk the timbers under the rails, and broke a great number of them. I have now taken up the whole of the timber and iron, and have laid balk, of from 12 to 14 inches square, down on the ground, and have nearly all the road laid again, which now appears very firm. We prove every part as we lay it down, by running the engine over it by hand. I hope it will all be complete by the end of this week.
The tunnel is at a stand, and a special meeting is called for Saturday, in consequence of my proposing a new method of carrying it on; and if put into effect (of which I have no doubt) the driftway is long enough, and would not be of more service if wholly across.
The plan I have laid before them is to make a caisson, 50 feet long, 30 feet wide, and as high as from the bottom of the river to high water. It is made of whole balk, the joints caulked tight as a ship. On the caisson is placed an engine for driving the piles and drawing them again, and also for lifting bricks out of the barges, and the stuff out of the caisson into the barges, by a crane worked by the engine. The piles must be driven within this caisson, in every square, and as deep as the bottom of the tunnel. Then remove the earth and construct 50 feet in length of brick tunnel; then remove the caisson, draw the piles, and refix them 50 feet farther on in the river, and add another piece to the tunnel, and so on, until the whole is finished.
By this plan only 50 feet of the river would be occupied at one time, or less than a 400-ton ship at anchor in the river. We must bore up from the roof of the drift and put up a pipe to tap down the water from the caisson every time we move it.
The caisson and engine, with all its materials, will float together, and almost all the work will be done by the steam engine.
The first plan was for a tunnel of 11 feet in diameter, for foot passengers only, and was to be 14 feet lower than this present plan.
This plan is two tunnels side by side, 12 feet diameter, each to have a waggon-road of 8 feet wide, and a foot-path of 4 feet wide; one tunnel to admit persons going forward, the other backward, so as to prevent mischief in passing.
This plan can be completed for £10,000 less than the original foot-path of 11 feet wide. I think this a safe and sure plan, while the other would he very expensive, dangerous, and uncertain; and if ever executed would be but a foot passage.
No. 1 is the frame that guides the piles straight.
No. 2, pieces of timber across over the back of the arches, to keep the feet of the piles firm when we move the caisson.
No. 4, showing the piles, with a half-circle cut out of each, about 3 inches in diameter, down which oakum is driven to make the piles water-tight in the joints.
This plan will shorten the tunnel; it is not so deep as the other, therefore will come to clay much sooner on each side of the river, and the timber to support the roof will be saved. Your opinion on this plan will very much oblige
Your very humble servant,
The proposed caisson for repairing the drift seems not to have been adopted, and was followed by a recommendation to build two brick tunnels, each 12 feet in diameter, to accommodate the to and from streams of passengers and wheel-carriages, in lieu of the original intention of one tunnel of 11 feet in diameter: it was to be 6 feet below the bed of the river, or 14 feet nearer the surface than the original design thus reducing the stiff and very objectionable incline to and from the tunnel from its low level.
The double tunnel was to be constructed on a new plan. Instead of mining through the quicksand, a water-tight box of planks and piling was to be placed in the river, the enclosed earth excavated to the required depth, a length of brick tunnel built, the river-bed replaced, and the box removed ahead, for an additional length of brick tunnel, while the materials were to be moved, and the piles drawn, by a steam-crane, introduced by Trevithick a few years before, and the surplus water drained by a pipe into the old driftway.
This plan for an improved double way, estimated to cost £10,000 less than the tunnel or mining process, came before the directors on the 4th August, 1808, when " they resolved that the works be not proceeded with until further orders;" and on the 16th November,
Resolved (Mr. Trevithick and Mr. Rastrick attended the meeting) it having been stated to the directors by Mr. Trevithick that from unforeseen difficulties arising in continuing the present drift through the quicksand and broken ground on the north shore, the same will be attended with much greater expense than was originally estimated; and he having at the same time suggested another mode of making the tunnel at a much less expense, the directors think it expedient that such plan should be taken into consideration.
Resolved, that the following gentlemen be requested to take the said plan into their consideration: General Twiss, Lieut.-Colonel Mudge, Lieut.-Colonel Shrapnell, and Sir Thomas Hyde Page, with a request that they will report to the Board their opinion thereon.
On the 18th March, 1809, Mr. Healing, the attorney of Mr. Trevithick, attended this meeting, and stated he was authorized by Mr. Trevithick to accept £800, in addition to what he had received, in full of all demands on the company, or to consent to leave his demand to arbitration; but the directors not consenting to so large a sum, Mr. Healing withdrew, having no authority to accept a less sum.
The following plan, together with a description of the work done, was issued by the directors in March, 1809, soliciting opinions from fresh engineers; but the writer believes this attempt to tunnel the Thames never advanced another inch:-
Fig. 1 is the section of the shaft sunk on the south shore, lined with 9-inch brickwork laid in cement impervious to water.
Description of the Strata through which it passed.
- No. 1. Stratum consisting of brown clay . . . . . . . . . 9 ft. 0 in.
- No. 2. Loose gravel with a large quantity of water . . . 26 ft. 8 in.
- No. 3. Blue alluvial earth inclining to clay . . . . . . . 3 ft. 0 in.
- No. 4. Loam .. .. .. .. .. .. .. 5 ft. 1 in.
- No. 5. Blue alluvial earth inclining to clay, mixed with shells . 3 ft. 9 in.
- No. 6. Calcareous rock, in which are imbedded gravel stones, and so hard as to resist the pickaxe, and to be broken only by wedges . . . 7 ft. 6 in.
- No. 7. Light-coloured muddy shale, in which were imbedded pyrites and calcareous stones . . . 4 ft. 6
- No. 8. Green sand with gravel and a little water . . . 0 ft. 6 in.
- No. 9. Green sand . . . . . . . . . . . . . . . . . . 8 ft. 4 in.
- Total . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 ft. 4 in.
- From the surface of the ground to high-water mark . . . . . 8 ft. 0 in.
- Depth of the shaft from high-water mark . . . . . . . . . . 76 4 in.
The gravelly stratum No. 2 in the shaft extends about 400 feet into the river from high-water mark at T, to V: at this latter place it is about 2 feet thick, and underneath is alluvial earth approaching the nature of clay.
- a The entrance of the driftway (further described in Fig. 2), 5 feet high, 3 feet wide at the bottom, 2 feet 6 inches at the top in the clear.
- b b The framing of the drift, consisting of 3-inch plank.
- c The platform.
Fig. 2 (shown in Plate X.) is a section, on a smaller scale, of the river, with the shaft and driftway.
Fig. 3 is a plan of the same.
In proceeding with the driftway towards the north shore, the strata were constantly varying. The following is a description of the strata as they appeared at the face of the drift, at the several places specified. The variations in the intermediate spaces were not noted, but the surface of each stratum was nearly even for the greater part of those spaces.
- Face of the drift at the entrance from the shaft, measuring from the bottom upwards,—
- Green sand . . . 4 ft. 6 in.
- Gravel . . . 0 ft. 6 in.
- Total: . . . 5 ft. 0 in.
- At a, being 177 feet from the shaft,—
- Green sand . . . 4 ft. 0 in.
- Gravel . . . 0 ft. 6 in.
- Blue muddy shale . . . 0 ft. 6 in.
- Total: . . . 5 ft. 0 in.
- At b, 234 feet,
- Green sand . . . 3 ft. 9 in.
- Gravel . . . 0 ft. 3 in.
- Blue muddy shale . . . 1 ft. 0 in.
- Total: . . . 5 ft. 0 in.
- At c, 295 feet,
- Green sand . . . 3 ft. 7 in.
- Gravel . . . 0 ft. 3 in.
- Blue muddy shale . . . 1 ft. 2 in.
- Total: . . . 5 ft. 0 in.
- At d, 317 feet,
- Green sand . . . 3 ft. 5 in.
- Gravel . . . 0 ft. 4 in.
- Blue muddy shale . . . 1 ft. 3 in.
- Total: . . . 5 ft. 0 in.
- At e, 321 feet,
- Green sand . . . 3 ft. 3 in.
- Gravel . . . 0 ft. 4 in.
- Blue muddy shale . . . 1 ft. 5 in.
- Total: . . . 5 ft. 0 in.
- At f, 333 feet,
- Green sand . . . 3 ft. 3 in.
- Gravel . . . 0 ft. 4 in.
- Blue muddy shale . . . 1 ft. 5 in.
- Total: . . . 5 ft. 0 in.
- At g, 350 feet,
- Green sand . . . . 2 ft. 8 in.
- Gravel . . . . . . 0 ft. 4 in.
- Blue muddy shale . 2 ft.8 in.
- Total: . . . . . . 5 ft. 0 in.
- At h, 493 feet, the green sand ends.
- At i, 730 feet,
- Hard calcareous rock, mixed with loamy land. . . 5 ft. 0 in.
- At k, 799 feet,
- Hard rock . . . 5 ft. 0 in.
- At l, 858 feet,
- Ditto . . . 5 ft. 0 in.
- At m, 901 feet,
- Ditto . . . 5 ft. 0 in.
- At n, 931 feet,
- Rock, with a little sand and shells, and water in the roof. . . 5 ft. 0 in.
- At o, 945 feet,
- Hard rock . . . 2 ft. 6 in.
- Clay and shells . . . . 2 ft. 6 in.
- Total: . . . 5 ft. 0 in.
- At p, 996 feet,
- Rock . . . 0 ft. 3 in.
- Clay . . . 0 ft. 4 in.
- Shells . . 2 ft. 0 in.
- Clay . . . 1 ft. 0 in.
- Cockle shells . . . 0 ft. 4 in.
- Clays and shells . . . 1 ft. 0 in.
- Sand . . . 0 ft.2 in.
- Clay. . . 0 ft.6 in.
- Sand . . . 0 ft.5 in.
- Total: . . . 6 ft. 0 in.
- At q, 972 feet,
- Clay and shells . . . 4 ft. 0 in.
- Sand . . . 1 ft. 0 in.
- Total: . . . 5 ft. 0 in.
- At r, 992 feet,
- Clay and shells . . . 0 ft. 8 in.
- Sand . . . 4 ft. 4 in.
- Total: . . . 5 ft. 0 in.
- At s, 1011 feet,
- Sand . . . 3 ft. 6 in.
- Clay . . . 1 ft. 6 in.
- Total: . . 5 ft. 0 in.
The quantity of water in the gravel, No. 2, was so considerable, that a 14-horse engine could only keep the water a few feet below its natural level, and the shaft was sunk through by far the greatest part of this stratum into the blue stratum No. 3, with the water standing in it to the depth of several feet. It is well ascertained that this stratum of gravel extends through a considerable part of the adjoining country; but borings being made in the shaft from the bottom of this stratum, no water was met with in the substrata to the depth of 86 feet from high water, where a spring was discovered, which rose in a few hours, through pipes inserted for that purpose, to a higher level than that in the gravelly stratum No. 2. The shaft was therefore sunk only to the depth of 76 feet 4 inches.
The drift was then carried forward in a horizontal direction to the north, 559 feet. And, in order to explore the ground in the northern part of the line of the then proposed tunnel, the drift was turned to the west 23 feet 6 inches from the centre of the former line to the centre of the new direction, and then to the north (intended to be enlarged afterwards to the size of the tunnel), and carried forward 341 feet, making the distance from the shaft to the beginning of the rise at D 922 feet. Through the whole of this line no material interruption occurred; the strata consisted of firm sand, calcareous rock, and concreted gravel, with no more water than was easily kept under by a 14-horse engine.
At this point D the drift was made to incline upwards at the rate of 1 foot in 9. In prosecuting this part of the drift, at the distance of 23 feet from the beginning of the incline, the earth in the roof broke down, and discharged a great quantity of sand and water into the drift. At the time this circumstance happened, a space of only 6 inches by 30 of earth in the roof and none in the face was left untimbered; and through this space the earth kept falling by degrees, until a hole was formed capable of letting a man stand up in it, who perceived a quicksand, about 3 feet thick, and about 4 or 5 feet above the roof of the drift. The stratum between the drift and sand was clay; and water flowed from the sand. The hole was after some difficulties filled up, and the works proceeded.
From the observations which had been made in the progress of the drift, the engineer found that the strata dipped slightly from the south to the north, and concluded that the gravelly stratum No. 2 in the shaft would end in quicksand. This inference was confirmed by borings in the north shore at E, and by the fact that the wells there are much deeper than on the south. In expectation therefore of drawing off the water from the face of the work, borings were made at Nos. 6, 7, 8, 9, and pipes were forced up to the top of the quicksand at those places, which had the desired effect. The water came free from sand for a considerable time; but when the sand began to come through any of the pipes they were plugged up, and others occasionally inserted in different places, to the south of these, with the same object in view, and which kept the face of the work dry. By this means, and by using the utmost precaution in all other respects, the drift was afterwards extended 70 feet beyond this fracture where the roof broke down a second time, and sand and water entered the driftway with great violence, and to an alarming degree; so that in about a quarter of an hour the water rose in the shaft nearly to the top of it. On examining the river an opening or hole at w was discovered in the bed of about 4 feet diameter and 9 feet deep, and its sides nearly perpendicular. Into this hole clay, partly in bags, and other materials were thrown sufficient to fill it up; and which succeeded in stopping the communication between the river and the drift. The face of the drift was again opened, but the men could make but little progress, as the water and sand frequently burst in upon them, and drove them away. The pipes Nos. 1, 12, 13, and 14, were put up, and the drift was extended 20 feet inches farther, in nearly a horizontal direction, through the quicksand. At pipe No. 14 the first 14 inches above the roof was clay, and 3 feet of sand above it. The face was then timbered up, to prevent any further fall of earth or sand; and the pipe No. 18, 9 feet long, forced upwards diagonally, and the pipe No. 19 horizontally. The first 8 feet through which the pipe 18 passed was blue clay, and the last foot quicksand, of which a considerable quantity immediately flowed into the drift. This pipe soon became clogged up, it is presumed with clay, as some lumps came through nearly as large as the diameter of the pipe. The pipe No. 19 was 8 feet 6 inches long, and discovered nothing but blue clay; no sand nor water came through it.
At this period the engineer reported that he had examined the bed of the river, and found the hole at w considerably increased both in width and depth, and the earth at x very much sunk; and that he had no doubt these two fractures communicated underneath. He then gave it as his opinion that an underground tunnel could not be made in that line, unless the fractures were covered by caissons, without which the further progress of the drift would be useless; but that he had no doubt of being able to make a tunnel over the same line through the river, sufficiently deep into its bed, by means of movable caissons, or coffer-dams, and at a less expense considerably than the original estimate for the underground plan, and without any impediment to the navigation of the river. Under these circumstances the further progress of the works was suspended.
It is an important consideration with the company, that the size of the tunnel be large enough to admit two carriages to pass each other; or two of smaller dimensions, each to admit a carriage.
The company contemplate a foot tunnel, only in the event that a larger one should appear to be impracticable.
The plans must be formed with regard to the tunnel being lighted.
N.B.— That plan whose line is the shortest, and ascent the easiest, will have great claims to preference, if equal in merit in other respects.
By order of the directors, S. W. WADESON, Clerk. AUSTIN FRIARS, LONDON, March 30th, 1809.
Trevithick had not counted on this abandonment of the work; for at the time when the directors put aside the plans of their engineer, "and thought proper to invite ingenious men of every description to a consideration of the best means of completing so useful and so novel an undertaking," he was in communication with his brother-in-law, Mr. Henry Harvey, to arrange the preparing and sending to London "300 tons of scantled Cornish granite fortnightly," and his old friend. William West was to superintend the cutting and shipping of the stone.
As the free movement of ships in the river prevented the use of a bridge, the chief object in this underground passage was to avoid the great inconvenience of the boat-ferries across the river, between Rotherhithe and the large commercial docks on the south side of the Thames, and the narrow street on the north side, near the river entrance of the Regent's Canal at Limehouse, not far from the West India Docks, and about 2.5 miles below London Bridge.
Trevithick was engaged on this driftway a year and a half; during less than half of which active operations were in progress, while the remaining portion was taken up with vacillations and weakness in the directory, and interference and discord from the discontented shareholders.
After a lapse of nearly twenty years, Brunel, in 1825, commenced the Thames Tunnel, which, after great difficulties and unlooked-for expense, was opened to passengers in 1843, from Rotherhithe across the river to Wapping, near the London Docks, about a mile and a half below London Bridge; it consisted of a double tunnel made of brick, something like Trevithick had recommended but instead of using the proposed caisson, Brunel followed the principle applied in the drift, of underground working through the river-bed, securing the sides with brick or other material, and the working end by wood or iron, or other means allowing small openings through which the earth was removed, which could be closed when quicksand or water overpowered the workmen. Brunel called this end apparatus a movable shield; it was a large complicated structure, allowing about thirty-six men, each in a small compartment, to work in the end. In 1837, Sir Isambard Brunel informed the writer that the plans and papers on the driftway left by Trevithick had given him the highest opinion of his character and genius.
In 1869 the Thames subway was constructed by Mr. Barlow between Tooley Street and Tower Hill, about half a mile below London Bridge consisting of a cast-iron tube, 7 feet in diameter, put together in pieces.
The general outline of procedure was similar to that in the driftway, except that the work was secured by cast iron in lieu of wood. Trevithick's drift was of wood, Brunel's tunnel of brick, Barlow's of iron.
The many scientific and practical men brought into contact with Trevithick during the progress of the driftway helped very much to diffuse the knowledge of his high-pressure engines and railway locomotion.
Among the seventeen gentlemen who reported on his work were Rennie, Braithwaite, and Rastrick, all afterwards eminent in the engineering world, and others equally well known. Lieutenant-General Twiss, Lieutenant-Colonel Mudge, Lieutenant-Colonel Shrapnell, helped with their particular experience; and Mr. William Stobart, of Durham, and Mr. John Buddle, of Newcastle-upon-Tyne, experienced miners, were also present. All these persons undoubtedly saw Trevithick's high-pressure engines at the Tunnel and elsewhere in London; the dredging machines then at work in the river; and the locomotive and passenger railway at that time carrying passengers at a shilling a ride near Euston Square. The Newcastle and Durham coal proprietors in particular must have seen the engines, as they knew that Trevithick had sent a colliery locomotive to Newcastle and to Wales, and were especially interested in such matters.
- See Trevithick's letter, 10th January, 1805, chap. xv.