Hoists And Travellers. A simple form of hoist is shown to the left in fig. 296. The stone to be lifted is secured to the chain by a contrivance called a "lewis," and the stone is hauled up by a crab or winch placed on the ground near the hoist. The " lewis " is shown in section in fig. 296 at a d d.
A wedge-shaped hole a is cut in the stone to be lifted, three irons, a' b c, are inserted in this, a' and b first, c last, and the three are kept together by a pin d d; the hook of the lifting chain is passed through the ring e. A "traveller" of a simple kind, worked by manual labour, is shown in fig. 297. A cross beam a a carries the rails upon which runs the hoisting apparatus b, which is also provided with gearing to enable it to be traversed along the girder a a as required - this being supported by the "verticals," or "gantrees," c c - the side shoring of which, in one form, is shown at a in fig. 298, which illustrates another form of "overhead traveller," in which steam is employed to hoist; the steam engine traversing from side to side along the beam when required, as well as along the rails of the gantrees a b. Fig. 299 illustrates an ordinary, and fig. 300 the "Derrick" form of lifting cranes.