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. [Sidenote: Carpenter’s Jack.]