A, B, C, D, E, F, G, H, I, K, L, M, N, O, P, Q, R, S, T, U, V, W. ‘ 284 LONDON: PRINTED BY
FOOTNOTES: His Life has been written by Mr. Richard Beamish, F.R.S. (London, 1862.) 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.
‘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.’ 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. 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. 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. 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. 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). 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. These crabs were subsequently used at the floating of the Saltash trusses, and at the launch of the ‘Great Eastern.’ A similar arrangement was applied in the paying-out machinery of the Atlantic cable, and is still used for the picking-up gear in the ‘Great Eastern.’ A few extracts from letters relating to bridges of large span will be interesting: ‘January 31, 1852. ‘I have revised my calculation as to a span of 1,000 feet, and find that even with the loads and limitations of strains which I adopt—namely a proper thickness of ballast, and a possible load of a train of engines without tenders, and a limitation under such a load of 5 tons’ strain per square inch, that a span of 1,000 feet may be made in England of the very best workmanship, and sent out and erected for I should say safely 250,000l., of course a single way—another 250,000l. ought, I should think, to cover the rest of the bridge. I should like to explain to you the mode I should propose for raising such a bridge, weighing 7,000 tons. ‘December 1, 1852. As you ask me my opinion of the advisability of patenting your bridge, I give it you; though you will probably be the first person who will have followed such advice if you do so, and might safely patent such a novel mode of using advice. In my opinion you cannot patent the bridge. Without detracting in the least from your merit of invention, the form has been so frequently and exactly applied that no patent could hold. The Saltash bridge now just advertised for letting is exactly on the same principle as regards form; and this is so old to my knowledge that I can claim no invention, and the use of cast iron for such purpose is also incapable of being patented. There is much that is good in your bridge, and you deserve credit, but you would find innumerable claimants to dispute, and successfully, your attempt to claim a monopoly by a patent—I myself for one. Besides, I see it published in a book. ‘May 30, 1854. ‘As to your present enquiry, I do not think that what I am doing at Saltash would be applicable in this case; but without being guilty of great presumption, I think I may say that if the same plan will not do, it is fair to assume that the same brains which concocted the plan to suit the difficulties of the Tamar might very likely find the means of overcoming those of the Severn. If I should be able to suggest a feasible plan, and there should be found people ready to make it, I shall have the satisfaction of bridging the Severn as well as the Tamar.’ Mr. Brunel also mentions in another letter that the ‘very simple and effectual manner’ of applying the pneumatic apparatus, by forming the annular space round the circumference of the bottom of the cylinder, was suggested to him by Mr. Brereton, when the method of constructing the cylinder was being finally settled. The strain on the iron of the tube and of the chains with a load of one ton per foot run, in addition to the weight of the truss, flooring, and ballast, is under four tons per square inch. The principal dimensions of the hull and engines are given in the note to this chapter (p. 245). The Report in the Bristol Mirror newspaper of the same date (copied from the Liverpool Standard) is as follows:—‘Dr. Lardner’s speech was little beyond a repetition of his discourse last year in Bristol, re-published by him in the Edinburgh Review. The voyage to America by steam he treated as practicable, but so uncertain as to render a profitable result hopeless.... During nearly all the year there was an adverse west wind, and the Gulf Stream was to be avoided.’ Mr. Bremner’s apparatus is also described in a paper read by him at the Institution of Civil Engineers, and printed in the twenty-first volume of the Transactions, p. 160. Accurate illustrations of the break-water and floating apparatus will be found in the Illustrated London News of August 21, 1847. In publishing the correspondence to which reference has been made, the Directors acknowledge their obligations to all concerned in the arduous task of saving the ‘Great Britain;’ and they add—‘to Mr. Brunel above all their thanks are most due, for opening their eyes to what might be accomplished, and for taking upon himself the responsibility of her release, provided that Captain Claxton was employed to carry out his views.’ ‘By constant observation, to lay down position and course of ship, and correct compasses. ‘To record speed of ship through water by logs. ‘Revolution of engines. ‘Force and direction of wind. ‘Draught and trim of ship, sails carried, &c. ‘Temperature and peculiarities of sea water. ‘As the result of these observations, to plot down hour by hour the position of the ship, to compute the speed, variations of compass, the direction and force of current, and true direction and force of the wind.’ ‘When we started the “Great Western” to New York, I had a chart drawn and engraved of the sea (that is, the lines of latitude and longitude, and the bearings of the compass, and the coast and soundings) on a cylindrical projection of a great circle from Bristol to New York; and we found it very useful for the captain to see his great circle sailing, and to see how much he was deviating from it.’ After calling the Directors’ attention to the important step they were about to take, he proceeds:— ‘I am not pointing out a danger without being prepared to propose a remedy. The same man who, after he has been selected and appointed on account of his previous character as a sailor, and as an experienced naval man, would probably feel disposed to reject advice coming from those who do not profess to be sailors, and to resist directions which might appear to him as trenching upon his authority, or as implying doubts of his ability, could have no such feeling (if he is a sensible man and fit for the position) if his attention had been drawn to these views before his appointment, and if he accepts the trust reposed in him on the understanding that he is expected to pay attention to these opinions, and if, as I shall urge upon the Directors to ascertain, he entertains no objection to the adoption of them, and agrees to follow the principles of action which I hope to induce the Directors to adopt as rules in the navigation of the ship. ‘I propose therefore to lay before the Directors the result of my anxious consideration of this subject, to urge upon them the adoption of my views, and, if they adopt them, to urge that they should make it a condition in the selection and appointment of a commander that such views are approved of and adopted by him. ‘This is a strong and plainly stated request, but not more strongly put than I feel that the occasion requires. ‘I have an immense stake in the success of this enterprise. I do not refer merely to my pecuniary investment; but, as affecting my professional reputation, my stake is much deeper; as, although I was accidentally led by circumstances into proposing the plan we have adopted, and the Company was not originally formed to carry it out, and although the plan when proposed was well weighed and considered by men competent to judge, at all events, upon the prospects as a commercial speculation, and although it was adopted by them, and therefore they must share in the responsibility, and although many may share with me in the credit of our success; yet there is no doubt that I should have to bear solely and very heavily the blame of a failure. On this ground alone, therefore, the Directors, I am sure, will willingly allow me to urge my views strongly, and will excuse the length at which I do so. But I shall rely upon satisfying them that my views and opinion should command their concurrence on their own merits; and with this preface, which has already reached an undue length, I will lay before them a paper on the subject, most of which has been written for some time in anticipation of the present circumstances, and having been thus written at different periods is, I fear, somewhat disjointed, and wanting in arrangement, and therefore much longer than it might have been.’ This plan had, however, the effect of increasing the number of his correspondents, as several of them wrote a second time to express their regret that their letters had had no better effect than to be classed with the numerous communications which Mr. Brunel said he had received on the same subject, which had seemed unworthy of his notice; and they explained that though other people’s schemes were, no doubt, worthless, still that their own, if adopted, would launch the ship. February 1, 1858. My dear Brunel,—I slept last night like a top, after I received your message. I got desperately anxious all day, but my doctor would not permit me to venture so far away as Millwall. I do, my good friend, most sincerely congratulate you on the arrival of the conclusion of your anxiety. Yours sincerely, A letter from Mr. Brunel to his friend Mr. Froude, describing the floating, is given in note B to this chapter. He also had a model made, with arrangements for altering the levels of weights placed inside. By this means the results of the calculations were verified. It was determined that the ship would make a single roll from one side to the other in about six seconds. While she was in the Thames a steamer struck the hulk alongside and gave the great ship a slight impulse. Mr. Brunel, who was on board, took advantage of the opportunity to observe the period of the roll she made, and was pleased at finding it agree with the calculated period. It is to the investigations initiated at that time by Mr. Brunel that are due the great steps since made in the knowledge of the laws which govern the rolling of ships. Had Mr. Brunel lived he would no doubt have taken the same pains to record the rolling of the ‘Great Eastern’ as he had in the case of the ‘Great Western’ when, in 1839, he sent an assistant to America and back, who took observations of the rolling and pitching of that vessel in several voyages. These observations were made by a simple angle-measuring instrument, adjusted by the visible level line of the horizon, and not by the fallacious method of noting down the swings of a pendulum. The ‘Great Eastern’ remains almost perfectly steady in ordinary rough seas. When the seas become very long, so that their period is nearly the same as that of the ship, she rolls; though the number of degrees on either side of the perpendicular is not large. By stowing the weights of cargo high in the ship, the tendency to roll has been much diminished, and when engaged in cable laying, with the enormous weights in the cable tanks all placed above the lower deck, she is remarkably steady. The Sluice was made in the abutment of Prince’s Street Bridge, and was intended to create a scour after the water had been let off from either side of the float, the opening at the bridge being closed by a caisson which had long been in use when (as was formerly the case) the upper part of the float was scoured through Bathurst Basin. The Trunk, near the entrance from Cumberland Basin, is a wooden culvert between the floating harbour and the river. As much of the mud as could be dragged there was deposited at the entrance of the trunk, and, when the tide was low in the new channel of the Avon, sluices were opened, and the water rushed through from the floating harbour, carrying the mud with it. The Drag-Boat was fitted with a steam-engine which worked a large windlass with three compartments, round two of which chains were passed and fixed to posts on the quays, and the boat was dragged backwards and forwards. The third compartment of the windlass worked a chain which elevated or depressed a scraper, attached to a long pole at the stern, and secured from swerving by a chain-bridle which passed under the boat. The scraper stirred up the mud, and deposited the more solid parts at the entrance of the trunk. Mr. Brunel also desired that the float boards of the Neetham Dam should be put into proper working order; and that they should be altered so that, in times of land floods, the whole or a considerable portion of the excess of water should be retained, and passed through the feeder; and that even the water of spring tides should be allowed to pass the dam, and then be stopped back for the same purpose. Mr. Brunel’s family, by the permission of the Dean of Westminster, have placed a memorial window in the north aisle of the nave of Westminster Abbey. Along the bottom of the window (which consists of two lights, each 23 feet 6 inches high and 4 feet wide, surmounted by a quatrefoil opening, 6 feet 6 inches across) is the Inscription, ‘IN MEMORY OF ISAMBARD KINGDOM BRUNEL, CIVIL ENGINEER. BORN APRIL 9, 1806. DEPARTED THIS LIFE, SEPTEMBER 15, 1859.’ Over this are four allegorical figures (two in each light): Fortitude, Justice, Faith, and Charity. The upper part of the window consists of six panels, divided by a pattern work of lilies and pomegranates. The panels contain subjects from the history of the Temple. The three subjects in the western light represent scenes from the Old Testament—viz. the Dedication of the Temple by Solomon, the Finding of the Book of the Law by Hilkiah, and the Laying the Foundations of the Second Temple. The subjects in the eastern light are from the New Testament—viz. Simeon Blessing the Infant Saviour, Christ Disputing with the Doctors, and The Disciples pointing out to Christ the Buildings of the Temple. In the heads of each light are angels kneeling, and in the quatrefoil is a representation of Our Lord in Glory, surrounded by angels. The work was placed in the hands of Mr. R. Norman Shaw, architect, who prepared the general design, arranged the scale of the various figures, and designed the ornamental pattern work. The figure subjects were drawn by Mr. Henry Holiday, and the whole design was executed in glass by Messrs. Heaton, Butler, & Bayne. |