94 RAILWAY CONSTRUCTION. 



will be observed that the operations of the turn-table and the 

 traverser are quite distinct. With the former a vehicle can be 

 transferred from one line to another, and also turned completely 

 round ; but with the traverser the vehicles are simply moved in 

 a parallel direction, from one line to another, and when it is 

 necessary to turn or change a vehicle end for end, as in the case 

 of a mail-bag-catching apparatus van or a special saloon, then 

 resort must be had to a turn-table. 



Cranes. A large portion of the merchandise conveyed on 

 railways must be lifted into or out of the trucks by cranes. 

 The position, description, and capacity of these will depend upon 

 the materials to be handled. Large slow-working powerful 

 cranes will be necessary for raising heavy castings, large logs of 

 timber, or massive blocks of stone ; while the small quick-acting 

 cranes will be more suitable for dealing with the lighter packages, 

 casks, and bales. 



Fig. 447 shows a gantry or overhead crane, used for lifting 

 heavy weights out of an ordinary road-waggon, carrying them 

 a short distance, and then depositing them in a railway truck, 

 or vice versa. Double-flanged rollers, attached to the ends of the 

 platform C, C, run upon the rails R, R, which are fixed on the top 

 of the beams B, B, secured to the verticals A, A. The working 

 length of the gantry is only limited by the number of the 

 verticals, and this, being the fixed portion of the work, may be 

 extended out to any distance required. The travelling or carry- 

 ing girders of the platform C, C may be made of wrought-iron, 

 steel, or timber. They must be strongly framed and braced 

 together as a platform to carry the lifting machinery and weight 

 lifted, and have convenient gearing for effecting the transverse 

 or side-to-side movement, as well as a horizontal movement along 

 the line of rails on top of the verticals. Where the fixed portion 

 of the gantry is of considerable length, two or more travelling 

 platforms can be used. In the sketch given above, the entire 

 gantry is shown as made of timber, but iron or steel can be 

 equally well adopted, and continuous masonry or brickwork 

 walls may be built to serve as verticals. 



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 



