3i WALDON FAWCETT 



each machine is an automatic dumping tub or bucket, the 

 discharge of which may be made at the will of the operator, 

 either at the full height of the tramway or by an automatic 

 deflection of their motion and with no appreciable loss of 

 speed the buckets may be caused to descend and discharge 

 their contents at any point below the tramway. 



The bridge tramways are usually built in plants or groups 

 of three or four bridges which may be supported on either 

 single or double piers. The tramways are, as a rule, provided 

 with hinged aprons designed to extend over the vessels and 

 very frequently cantilever extensions are provided at the 

 opposite end, so that the buckets are enabled to serve a space 

 of 300 to 350 feet in width. The operation of the tuJD or 

 bucket is effected by means of a wire cable connected with 

 a drum in the engine room, and the engine is usually of the 

 double cylinder type. The piers supporting a bridge tram- 

 way are on wheels, and it is thus possible to skew or move side- 

 ways the entire structure, in order to bring the bridges in 

 line with the hatches of the vessel being unloaded. This 

 type of machine hoists the bucket of ore from the hold of 

 the vessel, conveys it to any desirable point on the tramway 

 and automatically dumps the material on the dock or into 

 waiting railroad cars. 



As indicating the capacity of the bridge tramway, it 

 may be cited that a plant of three bridges will readily handle 

 1,200 tons of ore in a day of ten working hours, hoisting the 

 material, conveying it a distance of 100 to 150 feet, and 

 dumping automatical^. In the case of the bridges of ex- 

 ceptional length a round trip can be made from the hold of 

 the vessel to the extreme end of the cantilever and back again, 

 a distance of 600 feet in one minute, and in actual operation 

 a rate of 45 seconds per trip has been maintained for hours 

 at a time. The buckets or tubs for conveying ore are usually 

 of one ton or a ton and a half capacity. There are several 

 modifications of the bridge tramway system, notably cable 

 tramways in which wire cables are substituted for the bridges 

 and what are technically known as fast plants wherein in- 

 stead of the long bridges there are extremely short ones with 

 tramway projections over the vessel and cantilever exten- 



