Page:Popular Science Monthly Volume 62.djvu/72

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THE existence in crude form of some elementary devices for hoisting or otherwise handling certain classes of raw material, notably stone and logs, dates back many years, but it has been within the past decade and a half that there has taken place that remarkable progression which has constituted one of the most impressive achievements of the modern engineering world. Not only is bulk material, practically without limitation as to weight, hoisted to any height desired, but it has been rendered possible to transfer commodities at high speed for either long or short distances, and thus the mechanical operatives of the modern industrial world secure the trilogy of an economy of time, a saving of labor and the conservation of expenditures.

Easily the most interesting as well as the most significant advancement in this broad field is found in the introduction of improved methods for the handling of those two most important commodities coal and iron, the latter embracing of course a variety of forms from iron ore to finished steel. Indeed, in the case of the most useful of metals there has been evolved a cordon of mechanical devices, the functions of which so supplement each other that from the time the ore leaves the mine until it has been transformed into marketable iron or steel the factor of manual labor directly applied, is practically eliminated.

The initiatory machine in this chain is found in the steam shovel which takes the iron ore from the 'open pit' mines of the Lake Superior district and later is called into requisition 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 carriage 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