Fig. 448 is a sketch of a small handy crane for warehouse work; it is quick in action, and restricted to weights not exceeding twelve hundredweight. This form of crane may be strengthened to lift still greater loads, but in doing so the additional size of the parts, and the corresponding extra labour in working, detract from its efficiency 296 as a quick-acting crane for light weights. Fig. 449 shows an ordinary fixed three-ton jib crane, a very convenient size for general station work. The centre pillar is fixed into a bed of masonry or a solid block of concrete. The jib is of wrought-iron or steel, those materials being so much more reliable than timber, and very little more expensive. This crane must be fixed so that in one direction the jib may command the centre of a railway truck, while in the other it can conveniently raise the packages to or from the carts or loading-bank alongside. In the sketch the crane is shown as placed on the loading-bank, but it may be placed on the same level as the rails if preferred. Cranes of this type and strength are frequently found necessary for the inside work of goods-sheds, where packages of considerable weight have to be handled. A very similar class of jib-crane is constantly made for lifting weights of five or ten tons or more, the different parts being made stronger and heavier to correspond to the weights to be raised. Fig. 450 shows a five-ton travelling crane. Although more costly, it has the advantage over a fixed crane that it can be moved about from place to place. It is mounted on a very strong waggon framework, and provided with springs and spring buffers. Instead of moving round a long deep centre, the jib of the travelling-crane is arranged to work round a bevelled metal roller-path laid down on the platform of the waggon, and has a heavy counterweight loaded to correspond to its capacity. Before commencing to lift any weight strong oak blocks or filling pieces are inserted between the tops of the axle-boxes and the under side of main beams of waggon, to relieve the springs of the pressure which would arise from the weight lifted. From the four corners of the waggon are suspended chains carrying gripping-hooks to be attached or clipped round the rails. These gripping-hooks, when firmly secured to the rails, prevent the crane from tilting over, as the weight of the waggon and also of the rails and sleepers are brought into play to counteract any tendency to throw the crane off its proper balance. With the larger size travelling cranes, capable of lifting ten or fifteen tons or more, outriggers of joist or I-iron, moving in slides, are run out at right angles on either side, and can be loaded with bars of iron or other weights to form a counterpoise.