[1] To avoid confusion, Sir Isambard Brunel has been called throughout by that designation, the one by which he is generally known: he was knighted on March 24, 1841.

His Life has been written by Mr. Richard Beamish, F.R.S. (London, 1862.)

[2] Lady Brunel survived her husband five years. Of their children, three lived to maturity, one son, Isambard Kingdom, and two daughters, Sophia, wife of the late Sir Benjamin Hawes, K.C.B., Under Secretary of State for War, and Emma, wife of the Rev. George Harrison, Rector of Sutcombe.

[3] He was sent to Paris to recover his knowledge of French, which had got rather rusty at school, and also to study mathematics. He retained through life a great admiration of the method of teaching this subject which was adopted in France.

In addition to the time spent in the study of mathematics and languages, Mr. Brunel occupied himself on his holidays in examining the various engineering works going on in Paris, and he used to send his father drawings and descriptions of them.

[4] Sir Isambard was also consulted upon a proposed suspension bridge over the Tamar at Saltash, where Mr. Brunel subsequently built the Royal Albert Bridge.

[5] This history has been written by Mr. Beamish in his Life of Sir Isambard Brunel, pp. 202-304, and also, up to the year 1828, in the very valuable work by Mr. Henry Law, C.E., entitled ‘A Memoir of the several Operations, and the Construction, of the Thames Tunnel,’ and published by the late Mr. Weale in his Quarterly Papers on Engineering.

[6] For an account of these earlier attempts see Law, pp. 3-7.

[7] This expectation does not seem to have been realised, as there was never any considerable traffic through the Thames Tunnel. Perhaps, however, it would have been otherwise had the large descents for carriages and horses been constructed.

[8] The results obtained by these borings were no doubt fallacious, but not to the extent which has sometimes been imagined. At a meeting of the Institution of Civil Engineers, in November 1849, Dean Buckland called attention to ‘the evils arising from the ignorance of the engineers who reported to Sir Isambard Brunel, previous to the commencement of the Thames Tunnel, that the whole of the bottom of the river at that spot was London clay.’ Whereupon Mr. Brunel rose and said, that he ‘agreed that knowledge of every kind was most desirable, and that it would be well if engineers were generally much better informed on many subjects which would be useful, and more particularly on matters connected with geology; at the same time he could not admit that they were deficient in that knowledge of the surface of the earth which was necessary for the purpose of guiding them in their work. It might be true that many members of the profession were, like himself, not perfectly well acquainted with the minute geological characteristics of the soils they had to deal with, but he thought the education and the practical experience of the profession generally rendered them well acquainted with those features and characteristics which were necessary for their guidance in the design or execution of work. He must also say a few words in defence of those persons (now nearly all dead) who made the borings in the Thames, and were stated to have made so fallacious a report previous to the commencement of the Tunnel. Now, although that statement had by constant repetition become a sort of historical fact, it was really only one of those popular fallacies which obtained too ready credence in the world. The position of the Tunnel was not determined by any report, or by the result of any borings, but with a view to establishing a communication between particular localities for encouraging the traffic which was anticipated from the facility of access to the docks, and for other local reasons, such as the general direction of the roads and streets on both shores. After the position was settled, and not until then, borings were made to ascertain what soils might be expected in that part of the river. It must be remembered that these borings were made full twenty-five years ago, when boring in the bed of a river through a depth of water of nearly thirty feet was not an ordinary occurrence. The tool then generally employed was the worm, and tubes were not even used in such cases. The borings showed the existence in that spot of something which, in the ordinary acceptation of the term, might have been inadvertently called London clay, but he had no recollection of its geological designation having ever been thought of. It was reported and shown to be a very fair clay for working in.... The errors which were made in giving the results of the borings did not, in fact, arise from ignorance, but from mechanical defects in the tools, for it was subsequently discovered that the worm frequently carried a portion of the upper tenacious clay through the softer strata beneath, and brought it up again. The tenacious clay might have been called London clay, but no value was attached to that particular designation; they cared little in engineering for its denomination, provided it was of a good tenacious quality. This mistake in terms (supposing it to have occurred) could not have had any influence on after proceedings; for, before the Tunnel was far advanced, he conducted with great care a series of borings extending across the Thames, and, as he used improved tools and worked through tubes, the holes were kept so dry that a candle was frequently lowered down to the bottom in order to see the amount of infiltration. By this means he was enabled to construct a correct section of the bed of the Thames at that spot, showing every layer of shells and gravel as well as every variation of the surface of the silt, &c. He entered more at length into these details than might perhaps appear necessary, because he felt it was incumbent upon those who had the conduct of works to show that they did not proceed so ignorantly or so recklessly as had been assumed, in the design or execution of large undertakings.’

[9] The paragraphs in small type, without any reference, are from Sir Isambard’s journals. The sentences inserted at the side are his marginal summary. Occasionally a few words are added (in square brackets) by way of explanation.

[10] The shaft subsequently made on the Wapping shore was sunk to its full depth without any under-pinning.

[11] Professor Rankine, in his work on Civil Engineering, p. 599, describes the Thames Tunnel works under the significant heading ‘Tunnelling in Mud.’

[12] Proceedings Inst. C. E. i. 34. The circumstances which led Sir Isambard to conceive the idea of a shield, and the earlier designs he made for it, are described, with illustrations, by Mr. Law, pp. 7-10.

[13] Mr. Law’s memoir contains a detailed description of every part of the shield, illustrated by careful drawings.

[14] Mr. Beamish had joined the works on August 7.

[15] On November 20 Mr. Brunel mentions in his diary that he had ‘passed seven days out of the last ten in the Tunnel. For nine days on an average 20⅓ hours per day in the Tunnel and 3⅔ to sleep.’

[16] On the previous day Mr. Brunel had been formally appointed resident engineer.

[17] Mr. Gravatt had been appointed an assistant engineer six months before.

[18] Sir Isambard’s journal of this eventful night consists—as he was not himself present—of Mr. Beamish’s journal, with a few words in warm commendation of that gentleman’s ‘judgment, coolness, and courage,’ followed by observations upon the stability of the shield. He then gives a statement made by Mr. Gravatt, and taken down in shorthand. No extracts are given in the text from Mr. Beamish’s narrative, as he has already inserted it in a condensed form in his Life of Sir Isambard Brunel, pp. 244-248.

[19] Mr. Michael Lane, at this time foreman bricklayer, became one of Mr. Brunel’s most valued assistants, and was employed by him on the Monkwearmouth Docks and the Great Western Railway. After filling various posts in the service of that company, he was in 1860 appointed their principal engineer, an office which he held till his death, in February, 1868.

[20] On this occasion an amusing incident occurred. Mr. Brunel was exceedingly unwilling to permit his visitors to make this expedition into the arch; but on the assurance that they could all swim perfectly well, he consented to take them, with the understanding that, if he jumped overboard, they were immediately to follow his example, and swim after him to the shaft. While they were in the arch Mr. Brunel (as Sir Isambard mentions) fell overboard. As soon as he recovered himself, and turned to swim back to the boat, he remembered that he had unwittingly given to his companions the signal to jump out into the water. He was much amused, on looking up, to see that they were not swimming after him, but were still sitting in the boat clinging to the gunwale, with faces expressive of blank despair.

[21] Mr. Brunel’s comment in his diary is as follows:—‘Without ascribing any particular merit to myself, I cannot help observing, for my future guidance, that being alone, and giving few but clear orders, and those always to the men who were to execute them, I succeeded in an operation not altogether mean, and which a very trifling want of precaution or order might have caused to be a total failure.’

[22] On January 15, 1828, the Directors of the Thames Tunnel Company passed the following resolution, which they ordered to be advertised in the Times, New Times, Herald, Ledger, and Courier:—‘That this court, having heard with great admiration of the intrepid courage and presence of mind displayed by Mr. Isambard Brunel, the company’s resident engineer, when the Thames broke into the Tunnel on the morning of the 12th instant, are desirous to give their public testimony to his calm and energetic endeavours, and to that generous principle which induced him to put his own life in more imminent hazard to save the lives of the men under his immediate care.’

[23] The Thames Tunnel was not successful as a commercial undertaking; but it has always been considered, especially by foreigners, one of the most interesting sights in London, and has been visited by several millions of persons. In 1865 it was purchased by the East London Railway Company, and trains now (March, 1870) run through it. The possibility of using the Tunnel as a railway had been considered in Mr. Brunel’s lifetime, and the idea was approved of by him.

[24] This description is based on the translation given by Mr. Drewry (Suspension Bridges, London, 1832, p. 75), from the Mémoire sur les Ponts Suspendus, by M. Navier (Paris, 1823, p. 49). M. Navier saw the bridges when they were erected at Sheffield in May 1823.

[25] The dimensions of these designs were as follows:—

[26] On plate I. is given (fig. 1) a facsimile on a smaller scale of the drawing sent in by Mr. Brunel for the last-mentioned (b) of these two designs.

[27] See below, p. 60.

[28] See above, p. 42.

[29] The dimensions proposed in this design were as follows:—

[30] A few days before this ceremony, an iron bar, 1½ inch diameter, and about 1,000 feet in length, was hung across the valley from Clifton Rocks to Leigh Down, to facilitate the works. It was traversed by a basket pulled by ropes. The first few journeys of this machine were somewhat perilous. It was intended that Mr. and Mrs. Brunel should be the first passengers; but, when all was ready, one of Mr. Brunel’s assistants started on a clandestine trial trip, and owing to a bend in the bar, the basket stuck half way, and the mast of a passing steamer caught in the rope. The rope was however cut, and he was drawn back. When the apparatus had been put to rights, on another occasion, when Mr. Brunel was in the basket, it got jammed, and he had to climb up the connecting link and get upon the bar, before he could release the basket.

[31]

[32] Plate I. fig. 2 (p. 49), shows an elevation of the bridge according to the designs on which it was commenced.

[33] See Mr. Brunel’s remarks:—Proceedings Inst. C. E. for 1841, pp. 78, 79.

[34] Rollers on an arched surface had been used previously in several bridges.

[35] The chains were used in the construction of the Saltash bridge.

[36] Speech of the Chairman, the late Captain Mark Huish, at the first general meeting, August 2, 1861.

[37] Some re-arrangement of Mr. Brunel’s design was rendered necessary in order to adapt the Hungerford bridge chains to the Clifton bridge, and there are three chains instead of two, as in Mr. Brunel’s design. The platform is stiffened by wrought-iron girders instead of by timber trussing, and the whole bridge is stiffened transversely by the wrought-iron girders at the sides, which are connected throughout by diagonal bracing. The clear width of the bridge is 30 feet, 5 feet less than originally intended. It should be added, that no attempt has been made to complete the towers according to Mr. Brunel’s architectural designs.

[38] A graphic account of this famous parliamentary contest will be found in the third volume of Mr. Smiles’ Lives of the Engineers, chapter xi.

[39] See Mr. Smiles’ Life of George Stephenson, p. 325.

[40] See Mr. Smiles’ Lives of the Engineers, vol. iii. chap. xv.

[41] By means of the railway (it was said) goods would be conveyed with ease from London to Reading in three or four hours, and from Bath to Bristol in one hour.

[42] During Mr. Stephenson’s cross-examination, several questions were put to him as to the dangerous consequences which might be expected to result from travelling through a tunnel a thousand yards long. At length he lost all patience at the ignorance displayed by the questions put to him by counsel, and the following passage of arms took place:—

‘Mr. Stephenson. I wish you had a little engineering knowledge—you would not talk to me so.

Counsel. I feel the disadvantage.

Mr. Stephenson. I am sure you must.’

In other parts of the engineering evidence there are some statements which read strangely enough at the present day, as for example the following: ‘The noise of two trains passing in a tunnel would shake the nerves of this assembly. I do not know such a noise. No passenger would be induced to go twice.’

[43] At this time the Lords’ committees were open to all peers who chose to sit on them, and it was not considered indecorous for peers who had not attended any of the previous sittings to vote on the division.

[44] The Great Western Railway was constructed with but few deviations from the line sanctioned in 1835. The only alteration of any importance was at the London end, where, by an Act passed in 1836, the line was taken to Paddington, instead of joining the London and Birmingham Railway near Kensal Green. This change of plan was rendered necessary by reason of a difficulty having arisen between the two companies as to the terms of their agreement, and not, as has been often stated, in consequence of the adoption of the broad gauge on the Great Western line.

[45] Sir William Armstrong’s hydraulic machinery at Paddington is described by him in a communication printed in the Report of the British Association for 1854, p. 418: ‘I have also applied it [water pressure machinery] extensively to railway purposes chiefly under the direction of Mr. Brunel, who has found a multitude of cases involving lifting or traction power in which it may be made available. Most of these applications are well exemplified at the new station of the Great Western Railway Company in London, where the loading and unloading of trucks, the hoisting into warehouses, the lifting of loaded trucks from one level to another, the moving of turn-tables, and the hauling of trucks and traversing machines are all performed, or about to be so, by means of hydraulic pressure supplied by one central steam engine with connected accumulators.’

[46] See p. 104.

[47] No copy of this report can be found; but documents of subsequent date sufficiently indicate the nature of the arguments Mr. Brunel used in it.

Mr. Brunel had about this time given much attention to the principles of wheel carriages, as is manifested by an interesting article ‘On Draught’ written by him for the work on ‘The Horse,’ published by the Society for the Diffusion of Useful Knowledge.

[48] With regard to this point, Mr. Brunel afterwards admitted that he had held a mistaken opinion. In speaking of his reasons for adopting the narrow gauge on the Taff Vale Railway in 1838, he said before the Gauge Commission:—‘One of the reasons, I remember, was one which would not influence me now; but at that time I certainly assumed that the effect of curves was such, that the radius of the curve might be measured in units of the gauge, in which I have since found myself to have been mistaken.’

[49] See Mr. Brunel’s report of August 1838, printed in Appendix I. p. 528.

This plan was never adopted, as it was found desirable upon the broad gauge to use still wider carriages overhanging the wheels; but advantage was taken of the broader base to use wheels of greater diameter. However, in the saloon carriages, where ease of travelling was the chief object aimed at, the bodies were placed within the wheels.

[50] In the course of constructing the earth-works of a railway, the contractors were accustomed to lay down temporary ways or lines of rail, for the earth waggons to travel upon. When these were done with, the proper road for the trains was laid down; and this, to distinguish it from the former one, was called the permanent way.

[51] See Wood On Railways, 3rd. edit. 1838, p. 151.

[52] A full description of the original road of the Great Western Railway, communicated by Mr. Brunel, will be found in Wood’s Treatise on Railroads, 3rd edit. 1838, p. 708.

[53] At this time Mr. Brunel was confined to the house by the effects of his accident on board the ‘Great Western’ steam-ship (see p. 242). Had he been on the spot, he would have been able to give the work careful consideration during its progress, and to judge of the expediency of proceeding with the plan.

[54] The continuity of the timbers diminishes the risk of trains leaving the line from small imperfections in the permanent way. And, should a train leave the rails, the injury to the carriages and to the road is generally less serious than it is when the wheels of a carriage off the rails come into repeated and violent contact with the cross sleepers. Instances have frequently occurred where carriages which have left the rails have run considerable distances on the longitudinal timbers without injury.

[55] This experiment excited the greatest interest, and it was long afterwards related how Mr. Brunel, by the stroke of a hammer, had knocked to pieces the scientific deductions of Dr. Lardner, who, as was well known, had prompted Mr. Wood’s decision in this matter.

Mr. Brunel was so much impressed with the great influence which the operation of the blast-pipe had on the working of the locomotive that he afterwards investigated the whole subject, and made further experiments to determine whether or not it might be expedient to abandon the steam blast, and to maintain the draught in the chimney with a fan worked by a rotary steam jet.

[56] The inconveniences of a break of gauge had already been brought into notice. One of the narrow-gauge companies, the Midland, worked two existing lines of railway, one between Birmingham and Gloucester, laid on the narrow gauge, and another between Bristol and Gloucester, on the broad gauge; and thus there was a break of gauge at Gloucester.

[57] It should, however, be added, that the Commissioners had stated in the body of their report: ‘We feel it a duty to observe here, that the public are mainly indebted for the present rate of speed, and the increased accommodation of the railway carriages, to the genius of Mr. Brunel and the liberality of the Great Western Company.’

[58] These experiments will be found in the Appendix to the Report of the Commissioners of Railways, respecting railway communication between London and Birmingham (ordered to be printed May 22, 1848).

[59] This was fully borne out afterwards, the express trains running in the same time, 3 hours, over both routes, though the length of the broad-gauge line was 129 miles, as against 113 of the narrow. Similar favourable results have been since exhibited in the competition between the broad and narrow gauge lines to Exeter.

[60] Among many important advances in railway travelling made on the Great Western Railway, it may be mentioned that it was on this line that express trains running long distances without stopping were first introduced; and that, in 1845, within about a year of the completion of the line to Exeter, express trains ran from London to Exeter, 194 miles, in 4½ hours. This rate of travelling, which was accomplished without difficulty by the broad gauge in its early days, has scarcely been exceeded since on any railway.

[61] Even in the locomotives when of equal power, Mr. Brunel calculated that the extra weight was not more than about 500 lbs.

The extra cost of the Great Western Railway was only, including land, from 300l. to 500l. per mile, or less than 10 per cent. of the whole; although Mr. Brunel had taken advantage of the broad gauge to get carriage bodies 2 feet wider than was then usual.

The wide carriages and waggons were found less costly than the narrow ones in proportion to the load they carried.

[62] The apparatus patented in 1839 by Mr. Samuel Clegg and Messrs. Jacob and Joseph Samuda, and improved from time to time by them, was that adopted in almost all the attempts made in this country to introduce the Atmospheric System. In reckoning up the force which was available for mastering the practical difficulties of the undertaking, the death, in 1844, of Mr. Jacob Samuda must be considered to have been to his brother, and to all others concerned, a great and irreparable loss.

[63] A considerable amount of engine power was necessarily consumed in exhausting the tube before the passage of the train commenced; and it might at first sight appear that this work was wasted, and that it was only the work which the engine performed during the passage of the train which was useful in traction. This, however, was not the case; for, as was admitted by the more scientific of the opponents of the Atmospheric System, the power employed in anticipatory pumping was work legitimately stored up and re-delivered in relief of the engines during the passage of the train. A waste of power incidental to the Atmospheric System was indicated by the heat of the air which was delivered by the exhausting pumps. This waste, however, amounted on the average to only 10 per cent. of the total work done. A further source of waste of power was the friction of the air passing along the tube to the exhausting pumps; this waste was found to amount, on the average, to from 10 to 15 per cent. of the total work done.

[64] This was almost the only case in which Mr. Stephenson approved of the application of the System.

Before the Croydon and Epsom Committee, in answer to the question, ‘Does the Atmospheric railway give you any power of using practically and usefully steeper inclines than the locomotive railways?’ Mr. Stephenson said, ‘Yes, I think it does, but still at a very inordinate loss of power; still it is within the scope of the Atmospheric System under particular circumstances. I remember a case where it might be advantageous. Mr. Brunel went to Italy for the purpose of laying out a line there, and from Genoa over the Apennines he had to form a line; it would probably rise 15 or 20 miles at 1 in 100 or 1 in 60 or 70. Where there is that continuous line of ascent, where no stoppages are required, where the locomotive is totally inapplicable, there I can conceive nothing more eligible than the Atmospheric plan’ (p. 80).

[65] The length of the line was 52 miles, but as it was considered that auxiliary stationary power would in any case be necessary on the 10½ miles of very steep inclines, the cost of the Atmospheric apparatus is taken on 41½ miles.

[66] It must be remembered that beyond the South Devon Railway was the projected railway through Cornwall, which, with its long and heavy gradients, was, in all its features, even more suitable than the South Devon for the application of the Atmospheric System. Had that system succeeded, and been introduced on the Cornwall Railway, a very great saving might have been made in the cost of the works of this line.

[67] I.e. before the Croydon and Epsom Committee. See above, p. 138.

[68] It will be found on pp. 35-52 of the Minutes of Evidence taken before the Atmospheric Committee (ordered to be printed April 24, 1845).

[69] This appeared with sufficient clearness from the general comparison between vacuum, weight of train, and speed. The exact appropriation of the force employed was shown by some dynamometric experiments made on the line.

The highest speed recorded was 68 miles per hour, with a train of 28 tons, the speed averaging 64 miles per hour for four level miles of the line, the vacuum being 16 inches. This speed should have exhibited a resistance of about 21 lbs. per ton, or 588 lbs., as the running resistance or friction, and 645 lbs. for the resistance of the air; in all 1,233 lbs. Now, the pressure due to 16 inches of vacuum on the piston is 1,390 lbs., which gives 157 lbs. as the friction of the piston; a result which corresponds sufficiently well with a direct dynamometric experiment.

Going to the other extreme, there are numerous records of trains of 100 tons which attained, on a level of four miles in length, average speeds of from 30 to 35 miles per hour, with 16·5 inches of vacuum, one train of 103 tons going 32·4 miles per hour with 16·9 inches of vacuum.

[70] This valve consisted of a number of long delicate blades of spring steel, arranged parallel to each other, as in a musical box, but with wider intervals. These plates rested on a series of truly faced bars, which crossed the end of the air-passage. The slightest pressure outwards lifted the springs; and as the area of opening was large, a very free passage was given to the air. On the current ceasing, the blades instantly, yet without shock, replaced themselves in contact with the bars, clipping them tightly under a very small reverse pressure, and effectually closing the passage. Their merit consisted in their being almost without weight, and thus promptly re-closing the aperture by a delicate elastic reaction.

[71] Trains frequently arrived late on the Atmospheric portion of the South Devon Railway, owing to its being at the end of the long trunk line from London to Exeter, and having at its other end a locomotive line contending with very heavy gradients.

[72] It may be mentioned that, from the date of the abandonment of the Atmospheric System, he refused to receive any remuneration for his professional services as engineer beyond a nominal retaining fee.

[73] See above, p. 138.

[74] These quantities are the result of the experiments made in September 1847. They agree with what is now the received opinion of authorities on train resistances, and represent favourably the case for the locomotives at the time of Mr. Brunel’s report in August 1844. At the time when Mr. Brunel wrote his report of August 1844, the weight of a locomotive, as has been said, bore a higher ratio to its power.

[75] It must be borne in mind that all the inconveniences attending the use of auxiliary locomotives must be encountered, or else the excessive dead weight of an engine powerful enough to take a train up the steepest gradient in a hilly district must accompany it for the whole length of that part of the line.

[76] No dynamometer was used in these experiments, but all other requisite data were recorded with the greatest exactness, and the horse-power employed may be deduced by means of the scale of resistance which the subsequent dynamomotric trials supply. Moreover, the result above arrived at for the consumption of coke is verified by an examination of published indicator diagrams taken off the same engine on another occasion.

[77] It would of course be impossible here to give a description of all Mr. Brunel’s bridges, or even to refer to the most important of them with that minuteness which would be required if this were a book written for professional use. The following publications may be consulted:—Bourne’s History and Description of the Great Western Railway, 1846; Brees’ Railway Practice, 1837; Simms’ Public Works of Great Britain, 1838; Proceedings of Institution of Civil Engineers, vols. 14, 25, and generally; Molinos et Pronnier, Construction des Ponts Métalliques, 1857; Humber’s Cast and Wrought-Iron Bridge Construction, 1861; and Humber’s Record of Engineering for 1866. At the end of the description of many of the bridges in this chapter a note has been given of publications in which the bridge has been referred to.

[78] In the early days of the Great Western Railway special designs were made for every one of the ordinary bridges over and under the railway; but when, in consequence of the rapid extension of the Great Western system, the number of bridges to be designed became very large, Mr. Brunel had a set of ‘standard drawings’ prepared and engraved, which embodied the experience gained, and contained designs suitable for various situations. The contract drawings were made by adapting to the particular circumstances of each case the standard drawing which was most applicable to it. This system, besides securing uniformity of construction, introduced a considerable amount of economy; since, the standard drawings being based upon the results arrived at in an extensive practice, the proper structural arrangements and dimensions were indicated with far greater accuracy than could be attained in a reasonable time by an independent calculation in each individual case.