The life of Isambard Kingdom Brunel, Civil Engineer Part 39

It is desirable that all engaged in directing any part of the work should understand the general course of proceeding which it is intended to pursue, so far as may be found practicable; circ.u.mstances may modify these pre-arranged plans, and may compel a total departure from them, but every endeavour will be made to adhere to them.

GENERAL COURSE OF PROCEEDING.

[Sidenote: To start about noon of Tuesday.]

I propose to commence operations about two hours before high water, or about noon, and to endeavour to get the s.h.i.+p down as quickly as I can into the water, and down to within about 36 feet of the bottom of the ways.

My object in starting at this particular time of tide would be to get the s.h.i.+p into the water, and waterborne to some extent as soon as I could.

[Sidenote: Stop short of end of ways.]

I propose to stop short of the end, in order to avoid the necessity of having to knock away all the sh.o.r.es, and clear the cradle at the evening tide, when it would be dark, and to float on the morning tide, when it would be also dark.

I should propose then to stop about 36 feet short of the end.[162]

[Sidenote: _Evening._ Clear away sh.o.r.es of the 20-feet cradles.]

At low water, although dark, I shall endeavour to knock away the sh.o.r.es of the 20-feet cradles, or as many of them as possible, and clear all from these cradles except the unbolting of the filling-pieces.

[Sidenote: Under favourable circ.u.mstances clear away also _all_ the sh.o.r.es on the port side.]

If the operations have proceeded easily, and the ways not sunk much, I shall also knock away all the long sh.o.r.es on the insh.o.r.e or port side of the s.h.i.+p, so as to leave less to do on the following day.

[Sidenote: Prepare for a further pull at the night's high water.]

I shall then prepare at leisure to place the barges to get one pull of 36 feet, or as much more as I can (as I shall not hesitate to pull the cradles 20 feet off the ways) after high water of that night.

[Sidenote: Last move at 4 A.M.]

Soon after the high water of that night, and when the water has fallen sufficiently to prevent any risk of floating, but while the s.h.i.+p is still waterborne, probably about 4 or half-past 4 A.M., I shall make the last pull; and although it will be in the dark, yet having only one pull to make, and plenty of time to prepare, and no expedition required in the operation, I think it may be easily done.

[Sidenote: Float on high water, Wednesday afternoon.]

The s.h.i.+p will then be left till low water, when we shall clear away everything we can from the cradles, and get all ready for floating at high water on the afternoon of Wednesday.

Provided the mechanical arrangements should prove efficient, the success of the operation will depend entirely upon the perfect regularity and absence of all haste or confusion in each stage of the proceeding and in every department, and to attain this nothing is more essential than _perfect silence_. I would earnestly request, therefore, that the most positive orders be given to the men not to speak a word, and that every endeavour should be made to prevent a sound being heard, except the simple orders quietly and deliberately given by those few who will direct.

In a memorandum of 'Particular Instructions,' dated the next day, October 31, there is the following pa.s.sage:--

_Starting_.--A strain being brought upon all the purchases, and the holding-back purchase being slack, if the s.h.i.+p does not move, the two presses will then be worked; if she does not then move, or if, when moved, she stops and each time requires the presses, the attempt will be postponed, and more moving power applied for the next time.

If, after being started by the presses, the river purchases are found sufficient to move her, the operations will proceed.

In another part of these 'Instructions' Mr. Brunel again shows that he was not, as has sometimes been supposed, under the impression that the friction would be so small that the only important thing to be thought of was to check the s.h.i.+p from rus.h.i.+ng too fast.

On the contrary, he foresaw the possibility of her not moving at all, even with the presses, that is to say, with a force of 1,100 tons over and above the action of gravity. If after moving she stopped, and then required the presses again to move her, this would show that the operation could not be properly carried out, and that the work must be suspended till more motive power was applied. If, again, the river tackle were sufficient to move her, then the work was to proceed, but the friction might even then be so great as to render it desirable to remove all r.e.t.a.r.ding force. He says, in another pa.s.sage in his 'Instructions:'--

It is very likely that no checking whatever at the drums will be found necessary, but that, on the contrary, it will be found desirable to get rid of any resistance by overhauling the heavy chains through the sheaves.

The best day on which to begin the launch was Tuesday, November 3, as it left two or three days of the high full moon spring-tides for the operations, should they be prolonged.

On Monday, November 2, the chief work remaining to be done was stowing kentledge or iron ballast on the cradles, to prevent the timbers floating when the s.h.i.+p should be moved off them. All the appliances were ready, and, except the river tackle, had been carefully examined. This, as has been already said, had not been tested.

It was now for Mr. Brunel to consider whether, in consequence of the river tackle not having been properly tested, he should postpone the launch till the following month.

It was most important for the Company that the s.h.i.+p should be afloat as soon as possible; and, as any defects which might exist in the river tackle would almost certainly declare themselves in the earlier part of the operation, when nothing worse than delay could be apprehended, Mr.

Brunel, after a careful review of all the circ.u.mstances, determined to attempt the launch.

On the morning of November 3, the work of putting kentledge on to the cradles was completed by firelight, and the rails were rubbed over with a mixture of oil and black-lead. All the sh.o.r.es and props which supported the weight of the s.h.i.+p had been removed, and she was now resting entirely on the cradles.

Later on in the morning the brakes of the drums were tightened down, and the dogsh.o.r.es were removed from the ways in front of the cradles. Mr.

Brunel, who had been engaged from an early hour in examining all the preparations, superintended this operation, and, having satisfied himself that all was clear and ready, returned to the upper part of the yard.

By this time it was crowded with people. The Directors, contrary to Mr.

Brunel's expressed wish, and without informing him of their intention, had issued a large number of tickets of admission. A few days before, Mr. Brunel had suggested that four policemen should be obtained, thinking that all they would have to do would be to contend with trespa.s.sers. The police force actually present were ignorant of the portions of the yard to be kept clear, and Mr. Brunel had himself to go and a.s.sist in ordering visitors away from the neighbourhood of the path prepared for the tackle of the stern hauling gear. The crowd soon became so great that it was almost impossible for the men in charge of the hauling-engine at the stern to see the signals given from the middle of the yard, or for those in the middle of the yard to see what was happening at the stern.

At about half-past 12 o'clock the fastenings of the s.h.i.+p at the bow and stern were let go, and Mr. Brunel ordered a small amount of slack to be given off from each drum. This was done by men turning the handles of the gearing which had been provided for winding the chain on to the drums. The order was then given to haul on the bow and stern tackle, and to pump at the hydraulic presses. It is doubtful what amount of strain was put on by the tackle and the presses, but it was probably not very great.

Presently a shout from the forward cradle announced that it was moving, and almost immediately the stern cradle also started with what appeared to be a considerable speed. The men who had been engaged in turning the handles of the gearing had remained leaning against them. As soon as the s.h.i.+p had moved a few inches, she took up all the slack chain. This made the drum revolve, and the handles of the gearing spun round very rapidly, striking the men, and throwing them into the air. The men who were at the brake-handle next to the gearing ran away. Mr. Brunel, who was standing near the drum when the accident happened, shouted to the men to hold on to the brakes, and ran to the spot. The men who had remained at the other brake-handle hauled it down with the tackle. A great restraining force was thereby brought upon the s.h.i.+p, and her progress ceased; the forward cradle having moved 3 feet, and the after cradle 4 feet 3 inches.

Five men were injured. On the death of one of them it was stated at the inquest, by the foreman of the drum, that, after the slack had been paid out, he had ordered the men to stand clear. Be this as it may, it cannot be denied that the handles should not have been used after the securing chains had been let go; and indeed Mr. Brunel said at the inquest, 'I may blame myself, for I did not antic.i.p.ate that the handles would have revolved so rapidly.'

After this accident, Mr. Brunel determined to wait till high water before recommencing the operations. In the meantime the gearing was removed from both drums.

A more important change was also made in the arrangements. When the s.h.i.+p moved, the men on the four middle barges became frightened, thinking she was about to overwhelm them; a rush was made, and one man, jumping into a small boat, shoved off, leaving the rest to their fate. A report was at once sent to Mr. Brunel that the men were untrustworthy, and that they would not remain; and that, as the barges would be of no use without the men, the chains had better be dropped and the barges removed. To this Mr. Brunel consented.

It would, however, have been sufficient to take the men off, leaving a tug-boat and a few steady men to keep the barges out of the way of the s.h.i.+p; they would then have been available if required. Mr. Brunel, a short time after he had given the order, ran round the bow with Captain Harrison to countermand it; but it was too late, as it had been already acted upon. As events turned out no harm was done, as the centre barges alone would not have been sufficient to go on with, after the rest of the tackle failed.

The result of these changes was that when the operations were recommenced, the only hauling gear was the bow and stern purchases; the hydraulic presses were also available to start the s.h.i.+p.

At a little after 2 o'clock the signal was given to haul on the bow and stern tackle, the presses being at the same time pumped up. The brakes of the drums were slackened, but kept all ready for tightening.

Not long after the strain had been brought on the tackle, several of the teeth of one of the wheels of the bow steam crab gave way, and the chief anchor at the stern began to drag, so that no efficient strain could be obtained. On this being reported, the operations were discontinued; and, as there was no possibility of getting things ready by the next day, the launching operations were postponed till December 2, the next full moon spring-tides.

As soon as this was known the visitors rushed in on the works, crowding about the cradles and ways; and Mr. Brunel had to postpone those investigations which he wished to make at once.[163] The whole yard was thrown into confusion by a struggling mob, and there was nothing to be done but to see that the s.h.i.+p was properly secured, and to wait till the following morning.[164]

The next day was devoted to an examination of what had gone wrong, and to the consideration of what should be altered before another attempt was made.

At the stern mooring the anchor was bedded into the ground on the further side of the river.

The difficulty with regard to the four centre barges was got over by placing the four crabs with their tackles in the yard, on the landward side of the s.h.i.+p. The four chains attached to the s.h.i.+p, which had before been hauled on directly from the barges, were now pa.s.sed round sheaves on the barges, and brought back under the s.h.i.+p's bottom to the tackles in the yard.