UTILITIES FOR HANDLING RAW MATERIAL 33 



sions over the railroad tracks on the dock, the effect of this 

 short haul being to reduce tremendously the lapse of time 

 necessary for the transference of raw material from vessels 

 to cars. 



In the case of all forms of bridge tramwa}' apparatus 

 it is necessary to employ large gangs of men to fill by means of 

 hand shovels the tubs or buckets carried by the trolleys, and 

 naturally therefore there is in the transportation world a 

 tendency to regard with favor the latest inventions in the 

 line of machinery for the rapid unloading of iron ore, namely, 

 the automatic unloaders which dispense entirely with human 

 energy directly applied in the unloading operations. The 

 fundamental principle of all the automatic unloaders is found 

 in the operation of some sort of a clam shell bucket which 

 is let down into the hold of a vessel with its iron jaws ex- 

 tended and, closing them, retains in its grasp one or more 

 tons of ore while it is lifted from the hold and run back to a 

 stock pile or waiting railroad cars after the manner of the 

 bucket of the bridge tramwa}^ The original automatic un- 

 loader, introduced only a few years ago and in active use 

 to-day, weighs several hundred tons, and is equipped with 

 a great mast to be lowered through the vessel hatch and from 

 which depends a clam shell bucket capable of holding ten 

 tons of ore. The later patterns of unloaders, automatic in 

 their action, are fitted with excavating buckets of only about 

 one ton capacity, and which therefore permit of hoisting and 

 transference by wire cable instead of necessitating the pon- 

 derous iron and steel structure required to support the mast 

 and clam shell in the original design. 



Bridge tramways similar to those in use on the ore un- 

 loading docks are employed in the furnace yards to convey 

 the ore from the railroad cars to stock piles, and a patent 

 furnace hoist automatically conveys the ore together with 

 the coke and limestone to the top of the blast furnace and 

 performs the operation of charging. The automatic hoist 

 consists of an inclined iron trussed bridge reaching from the 

 floor of the stock house to the top of the furnace shell and 

 from thence over the top opening of the furnace. On this 

 bridge is laid a track of T rails on which travels a skip or car, 



Vol. 6-3 



