UTILITIES FOR HANDLING RAW MATERIAL 31 



to transfer the ore from the stock piles at the mines to the 

 railroad cars provided to carry it either direct to the blast 

 furnaces or to the vessels wherein it will be given water car- 

 riage to the great lakes. The steam shovels for the latest 

 approved practice range in weight from fifty five to ninety 

 five tons, and in this feature alone is afforded ample evidence 

 of progress, for but a few years since the shovels of thirty 

 five or forty five tons weight were deemed sufficient for all 

 the exactions imposed by this work. The shovels now in 

 use have dippers ranging in capacity from two and one half 

 to five yards, and something of the celerity of movement 

 with which they are operated may be appreciated from the 

 fact that on many occasions ordinary railroad cars are loaded 

 with ore and pushed out of the way of the machine at the rate 

 of one every two minutes. 



In the unloading of the immense cargo carrying vessels 

 of the inland seas, wherein the iron ore is conveyed from the 

 Lake Superior mining district to the ports adjacent to the 

 blast furnaces of the middle west, are employed the various 

 forms of hoisting and convejdng apparatus, all of American 

 origin, which probabl}^ constitute the most famous of all 

 the installations for transportation purposes. In this field 

 of activity methods advanced, at a single step, from the old 

 plan of unloading the vessels by means of wheelbarrows and 

 permanent trestles to the bridge tramway structures which 

 are up to the present date in almost universal use. 



The conspicuous elements in any such installation em- 

 brace the elevated tramway — spanning the dumping ground 

 or railroad yard and connecting it with the vessels — the 

 trolley or carriage traversing this tramway and the system 

 of mechanism by which the whole is operated and controlled. 

 Such an apparatus is operated, of course, by a motive power 

 located beyond the limit of travel, and while the operation 

 is at every stage subject to the control of an operator, a large 

 proportion of the important functions are automatic, the 

 positive movements of the parts through such operations 

 being derived entirely from the bodily movement of the ap- 

 paratus itself, while actuated by momentum, gravity or the 

 direct action of the hoist rope. Attached to the trolley of 



