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Other tim

wedges to relieve the screws. bers were next inserted aud shored up in pairs, in a similar way to the others, and when all these were secured other apertures were cut through the building to admit the upper timbers.

The next operation was the insertion of the timbers, with the rails fixed upon them. The centre timbers immediately below the upper beams were fixed first. These were firmly bedded on the stone pavement of the pier, and upon the solid masonry of the new work. The sheave balks to each were then threaded through the building, and firmly wedged to the timbers above, and to the rails below, by a series of wedges. The other rail and sheave balks were placed in a similar manner underneath each upper timber, and in the order in which they were inserted in the building. Finally, when all these wheels were brought to their bearing, the small portions of the original masonry left in the four corners of the building were cut away at one time, and the two remaining intermediate upper timbers were threaded through and secured.

While these works were in operation, the octagonal shaft was tied together in the following manner. Two planks, 44 feet in length, and 3 inches in thickness, were suspended from the cornice at each angle of the shaft, and then lashed closely to the masonry by ropes and wedges. Five horizontal tiers of iron straps, 24 inches broad, and seveneighths inch thick, were made to embrace the building, and these were drawn closely up by screws to the above-mentioned planks and filling-in pieces.

Immediately above the cornice, and on a level with the light-room floor, eight apertures were made through the walls (which were here only 10 inches in thickness), and pieces of timber were pushed through the apertures from the inside, and drawn back again till they met in the centre. Strong plates of malleable iron covered the joints above and below the timbers, and screwed bolts passed through the whole. This upper platform was connected with the cradle below by a large chain passing round a strong bar of iron at the top of the platform, and round a similar bar of iron on the lower side of the cradle, and the chain was drawn tight by a large screw.

The upper platform was further connected externally with the cradle by eight main uprights of timber 12 inches square, tenoned into the horizontal timbers at the cornice, and brought close to the masonry of the building at the base, and secured to the cradle and upper platform by stirrup-straps and bolts. The uprights were united together by three tiers of chock-pieces. Three

iron straps, 3 inches broad, and 1 inch thick, passed round the chock pieces and uprights, and the whole was drawn closely to the building by screws.

The raking braces were next erected, and their feet passed between the timbers of the cradle and cill-beams fixed thereon, so that the whole framing could be firmly bound together (fig. 3). The four diagonal beams and ledges fixed to the raking braces, further prevented any of the timbers from springing or twisting.

Up each angle of the building, above the cornice, battens, 2 inches thick, were fixed, with two tiers of horizontal junction pieces, kept together by binding screw straps. The dome of the building, which is of iron, covered with lead, was fastened by chains passing round the summit and the upper cornice, and continued down to the projecting timber of the upper platform, each chain being tightened by screws. The large plates of glass of the light-room were taken out, and window sashes, with ordinary crown glass, were put in their place. The light, however, was exhibited nightly, as usual, during all the operations of removal; a lead pipe, lengthened as required, being connected with the gas-works on the pier.

were

On the 2nd of August everything was prepared for drawing the building northward. For this purpose, five pulling screws were strongly fixed to the glacis of the pier, north of the building, and chains were attached to them, and to the cradle upon which the lighthouse rested. These screws worked by twenty-four men. Four forcing screws, worked by three men to each, were applied behind the cradle, to assist in propelling it. The total number of men employed on the occasion was forty. The cradle was supported on one hundred and forty-four wheels, which travelled on eight parallel lines of rails, but the extreme ends of the cradle were supported and moved on slide balks only. The operations for the removal northward were commenced at half-past 3 P. M., and at a few minutes after 8 P. M. it was safely landed on the new pier. The distance travelled was 20 feet 5 inches.

On the 7th of August the building was drawn, in a similar manner, to a further distance northward of 8 feet 1 inch.

The cradle was then shored with timber uprights, which allowed the railway and sheave balks to be withdrawn and reversed, for the purpose of taking the building to the eastward.

It is unnecessary to describe the process of placing these railway and sheave balks in a direction bearing east and west, as it is merely a repetition of the same operations

previously mentioned. Some difficulty was experienced in taking the building round the curve, which was a portion of a circle of 647 feet radius.

The rails on this curve were laid level to the point at which the tangential lines of the rails commenced, and from that point to the new pier-head they had a gradual inclination of 1 in about 225, making a total rise of 1 foot 7 inches above the original base of the building. This was accomplished on the raised platform by different heights of timber beams, and on the unfinished part of the pier, between the platform and the coping, by large stones set in mortar, on which the railway beams were solidly fixed. Fig. 4.

Fig. 5.

Fig. 6.

The series of wedges in the sheave balks, not only allowed them to be removed when required, but were otherwise of great use, for by slackening the wedges on the east side, and tightening those on the west, the building was retained in a perpendicular position, when the rails were on the inclined plane.

On one portion of the raised platform of the pier, the pavement was completed with large Yorkshire landings, from 6 inches to 8 inches in thickness. It was questionable whether they would be able to bear the great pressure of the building; but it was determined to try it, as the stones had been laid with the greatest care on a proper bed of rubble stone and the joints run with pozzolana mortar. As a precaution, planks were laid upon the pavement to equalise the pressure, and particular attention was paid to have the rail balks securely and thickly wedged upon the planks. Under the great load of the building very little impression was made upon the paving; in some few instances the joints of the mortar were

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cracked, but no stone whatever was broken, This is particularly noticed, because every practical man who inspected the pier was of opinion that the stones would not bear the pressure.

The cradle was supported on what are termed by ship-builders sliding balks; that is, the lower side of the travelling beam was convex, fitting into and sliding along the concave surface of the lower beam, which was solidly fixed upon the pier. These beams were greased with a mixture of soft soap and black lead, to diminish the friction. The sliding beams were connected with the cradle by a framing of timber, which formed part of the moving mass, with the view of saving expense, as it avoided the necessity of raising the surface of the pier to the level of the railway beams. The principal weight of the building was, however thrown upon the railways, and comparatively nothing of any consequence on the sliding balks.

Immediately underneath the area of the building, the cradle wheels were placed close together, but outside the area of the building they were separated from each other. Each of the wheel-plate castings had the under surface covered with a piece of felt dipped in tallow, and it was then secured to the sheave balk by a tapering wedge, fig. 4 (elevation), fig. 5 (plan), fig. 6 (section). By so doing, the timber was not injured with bolt holes, and the casting could at any time be easily taken out and replaced with another, had any accident happened to it. The spindles of the sheaves were very accurately turned, and the sheaves were likewise turned, to take off all irregularities from their surface. The rails were secured to the timbers by short spikes, formed with a head turned at right angles with the body, which allowed them to be easily drawn without much injury to the timber, when the rail had to be removed.

The cradle beams were all squared and planed, to distribute the pressure over the whole surface. They were of American oak, which is a very solid wood, and as it could be procured straight in long lengths, it was preferred to any other timber. The rest of the timber employed was Memel red and yellow pine. During the latter part of the operations the cast-iron rails were laid upon a plank of African oak, 1 inch thick, fixed upon the railway beams, as it was feared that the great weight would press the rails into the Memel timber.

The method employed in taking the building to the eastward, was different from that which was first attempted in moving it northward. The slow process of drawing the

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cradle forward by screws was abandoned, and recourse had to three ordinary winches. Each was worked by six men, with one man to hold on the tail-rope, which before arriving at the winch, passed through a twofold and threefold sheave block. The total number of men employed at the handles of the winches was eighteen, and the power of them, when so applied, may be reckoned at 562 lbs. The radius of the handles of the winches being 14 inches, worked a cog-wheel of 4 inches diameter, turning a spur wheel of 30 inches diameter, and a barrel of 10 inches diameter. The additional power of the twofold and threefold sheave blocks makes the whole power of eighteen men, applied in the manner stated to be 52,480 lbs. The gross weight moved

was calculated to be 757-120 lbs. or 338 tons. The distances traversed were determined by the various lengths of the railway beams which were taken up and relaid forward to save expense, but which, of course, prolonged the time of taking the building to its destination. The greatest speed with which the mass moved was at the rate of about 84 feet per hour, the winches being advantageously placed; but the average_actual rate was 33 feet per hour. The greatest distance accomplished at one time was 40 feet 7 inches; the average distance being about 28 feet. The actual time employed in moving the building to the eastward was thirteen hours twenty-four minutes, that distance being 447 feet 1 inch, to which if 28 feet 6 inches be added which it was

would have proved a failure; inasmuch as even with the internal railways and wheels, it sometimes required the utmost exertions of the men at the winches to pull the cradle forward. The outer part of the cradle, which bore the weight of the raking braces, was, to save expense, supported on sliding balks; on one occasion, when the ropes were tightly stretched, a few blows given to these sliding balks, caused the cradle, with its enormous weight, to start suddenly forward a distance of nearly 2 feet. In consequence, they were always tapped afterwards, whenever the cradle encountered any obstacle to its motion. M. le Bas experienced the same difficulty in moving the Luxor obelisk, both in Egypt and at Paris, where a great force was employed to drag it forward. The huge rock of the statue of Peter the Great at St. Petersburgh, was moved on balls of brass, turned very accurately and running in brass channels; yet they frequently stuck fast, and required the attention of a man to each, with an iron rod, to keep them in motion and equidistant from each other. The use of railways, with wheels moving in carriages fixed to the cradle, undoubtedly saved trouble and expense and to a certain degree reduced the friction.

At the time of building the new pier, preparations were made for the site of a lighthouse, by piling an area of about 20 feet square in the centre of the head, founding upon the piles and bringing up along with the other work, a mass of masonry, in large blocks properly squared and bedded solidly in pozzolana mortar. The foundation was therefore in readiness for the reception of the building. On the 4th of October it was brought to its destination. Timber uprights were immediately wedged up under the cradle, which permitted the different sheaves and railway balks to be withdrawn. Upon this being done, the masons commenced operations by building on the foundations above alluded to, pillars of stones with retreating courses, striking the shores, from time to time, as these pillars took their bearing under the original masonry.

The mortar used was made from blue lias lime, with a mixture of sand and pozzolana, and was laid in very thin joints. The chief difficulty arose in making good the last course, as the joint had to be made rather thicker than usual, for the admission of the masonry. The stones of the course, before insertion in the building, had their upper surface covered with thin sheet lead, firmly beat down and lapped for a breadth of 2 inches over the back part of the stone. This was done, to equalise the pressure and to prevent the external masonry from being

7

flushed, by the weight of the building it had to sustain. The joints were run with grout through the funnel of a tube, carried up a few feet in height to give additional pressure. They were previously closed all round with Roman cement, excepting a few apertures left on purpose for the air to escape, and which allowed the grout completely to fill the joint. Great care was taken to make the masonry sound and perfect, by properly bonding the joints, both internally and externally, by which means there is not any indication of the building having ever been displaced. The masonry was completed on the 12th of November.

Before cutting into the lighthouse for the insertion of the cradle, the different corners of the base were accurately levelled with an instrument, and trial was made whether the building was exactly perpendicular by a plummet. From time to time, as the building was moved forward, other trials were made for the like purpose, and also after it had been brought to its destination on the new pier-head. In all cases it was found to be as at first. No settlement was ever perceptible, even where the new masonry was placed, on withdrawing the cradle; nor has the slightest crack appeared since, in any part of the building.

The timbers and the chief part of the other materials employed, were used in other works, then carrying on by the Harbour Commissioners, and the men who worked at the winches, when they had accomplished their task, were taken off to other work connected with the building of the pier. The cost of carrying the work in question into execution, amounted to 8277. The building was erected in 1802, at an expense of upwards of 1,400. If to 8271. be added 2801., the estimated cost of a light-keeper's dwelling, gas-house, and other apparatus, it would have made 11077. as the total expenditure of this department. The estimated cost of building a new lighthouse on the high ground near the Fort, with a tide light on the north pier, dwellings, and other contingencies, amounted to 2,000l.; consequently, by adopting the removal of the building, as is above mentioned, there was a saving of 8937., and no inconvenience was experienced from the want of a harbour-light.

Since the completion of this undertaking, the author has had the honour to receive the thanks of the Board of Commissioners for his exertions; and a piece of plate of the value of 1007. has been unanimously voted to him as a further acknowledgment of his services on that occasion.