Connected with the cast-iron railways, preparations were also made at the eastern landing place, for lifting the stones by means of cranes or other machinery from the Praam-boats, and laying them upon the waggons to be conveyed to the building. After a good deal of consideration, patterns were prepared for an apparatus consisting chiefly of six pieces of cast-iron, four of which measured 12 feet in length, and of a corresponding strength. As will be seen in [Plate XI.], these bars met at the top in the form of two sets of sheers, but their lower ends were placed about 9 feet asunder. Connected with these, a pair of sheers were set up, which were moveable upon a bolt, and worked with a crab or winch machine, the whole being strongly batted to the rock. When the moveable pair of sheers, with their attached chain and hook, were suspended outwards over the stone to be lifted from the praam, the chain was hooked to the Lewis-bat, previously inserted into the block. The sheers were then raised till they were brought to a perpendicular position, when the motion of the winch was reversed, and the sheers were lowered inwards upon the wharf, and the stone thus laid upon the waggon. The chain was then unhooked, and the sheers were ready for lifting another stone, as will be better understood by referring to [Plate XI.], with its letter-press description.
Crane with moveable Beam.
Having, in the foregoing article, described the implement employed in landing the stones on the Bell Rock during the year 1808, we are now to notice the crane employed in laying or building them. It appears from Mr Smeaton’s Narrative, that the implements chiefly used for building at the Edystone, were a pair of moveable sheer-poles and a set of triangles, most ingeniously applied to their respective purposes. But such implements must have come far short of the expedition which the writer had conceived to be necessary at the Bell Rock, both on account of the much greater extent of the building, and also from its foundation being so much lower in the water. After considering the subject, and making minute inquiries into the practice at various public works, he found no implement of the description, which he considered applicable to his purpose. The common sheer-poles, still chiefly in use, were recommended as having upon the whole been successfully employed at the Edystone. In some instances, the common crane, with the beam fixed at the top, at right angles to the shaft, was applied for laying heavy materials. The writer, however, laid it down as a proposition to himself, That a more effective mode of building must be adopted at the Bell Rock than had hitherto been in use, by which all the stones at any time likely to be landed in the course of a tide, might be built and secured before the artificers left the rock.
The chief difficulties attending the application of the common crane in such a situation, consisted in the laying the stones perpendicularly into their respective places, as they were all of a dove-tail or angular form, as will be seen from [Plate XIII.] The fixed beam of the common crane was further objectionable, from its being more liable to interfere with the guy ropes. It would also have been difficult to have lifted it either laterally or perpendicularly upon the building, from one course to another. To these may also be added the great obstruction which the beam would have presented to the waves of the sea at high water. All these objections, however, were in a great measure got over, by substituting a moveable beam to work upon a bolt at the foot or lower end of the upright shaft, instead of a fixed beam at the top in the usual manner. But as we shall have occasion again to notice this machine in the operation of building, we shall here refer to [Plate XIV.] with its letter-press description. Three of these cranes, with moveable beams, were prepared for the work, in the course of the winter, one with an upright shaft of 28 feet in length, for laying the prepared stones upon the platform in the work-yard at Arbroath, and other two, with shafts of 21 feet, for building at the rock.
Sling Cart.
Though none of the stones of the Bell Rock Light-house were likely to exceed two tons in weight, in their finished state; yet, in their undressed state, they were much more ponderous. From the waste attending their dove-tailed form, and the working them square on all their sides, the blocks from the quarry were greatly reduced; in many instances, to one-half of the cubical contents of their quarry dimensions, before they were brought to the size of the moulds. The stones had not only to be conveyed from the harbour of Arbroath to the work-yard, a distance of from two to three hundred yards, but also required to be frequently lifted from place to place; as, for example, when in a hewn or dressed state, they were removed to the circular platform, in the middle of the work-yard, to be tried and marked;—they were again shifted from this position, and ultimately carried to the harbour to be shipped for the rock. From the various movements which each stone had thus to undergo, it became an object of importance to the facility and economy of the work, to consider how this could be most conveniently accomplished. Had a cart or carriage, with four wheels of the ordinary construction for great loads, been employed, it would have been extremely troublesome, in all the operations of loading, turning and moving from place to place. To have attempted to avoid this by the use of waggons with low wheels, and the introduction of railways along the quays and public streets of Arbroath, would also have been objectionable, especially as the object could be much more conveniently obtained by the use of what is called the Woolwich Sling-cart, represented in [Plate X.] By this machine, the weight is simply raised off the ground with a wheel and pinion apparatus fixed upon the frame of the cart, and in this manner, the stone, instead of being lifted upon the body of the carriage, had only to be suspended at the necessary height for overcoming the inequalities of the road. This vehicle had long been used with great advantage by military engineers, in moving ordnance; but was probably first employed at Mylnefield Quarry, and the Bell Rock works, in transporting blocks of stone.
Carpenter’s Jack.
Another implement prepared, in the course of the winter, for the Bell Rock work-yard, was the Carpenter’s jack, used for raising ships upon the blocks or props for the purposes of repair. This machine, which is simple in its construction, and direct in its application, consists of a rack and pinion, enclosed in a frame of oak timber, strongly bound with iron, as represented in [Plate X.] By working the handle of the jack, the stone-cutter is enabled, without the assistance of his fellow workmen, to turn and lay the heaviest stone to his hand. This apparatus the writer first saw used to much advantage, by the quarriers at Portland Island, in the year 1801; and though it had not perhaps at that time been put into the hands of the stone-cutter, it was obvious that it might also be applied to his purpose with equal effect.
It may further be noticed, regarding this useful implement, as strongly marking the prejudices of habit, that Mr Mylne, the proprietor of Mylnefield Quarry, who, with enlightened views, furnished his works with machinery of the very best description, among other articles, provided a number of these jack-machines for his quarriers, but, for a long time, they could not be induced to make use of them. One of the men, however, happening, of his own accord, to apply the jack in turning a heavy block, its utility soon became apparent; and Mr Allan the manager, who had previously taken considerable pains to get the jack introduced, was at length not a little pleased to find it, after having been laid up in store as useless, in much request throughout that extensive quarry.
Lewis Bat.