Inventions in the Century

by William Henry Doolittle

Other crushers have been invented, formed on the principle of abrasion. The stones, or ore, fall between two great revolving disks, having corrugated steel faces, which are set the desired distance apart, and between which the stones are crushed by the rubbing action. In this style of machine the principle of a gradual breaking from a coarse to a finer grade, is maintained by setting the disks farther apart at the centre where the stone enters, and nearer together at their peripheries where the broken stone is discharged. Large smooth or corrugated rollers, conical disks, concentric rollers armed with teeth of varying sizes, and yet so arranged as to preserve the feature of the narrowing throat at the bottom or place of discharge, have also been devised and extensively used.

A long line of inventions has appeared especially adapted to break up and separate coal into different sizes. To view the various monstrous heaps of assorted coals at the mouth of a coal mine creates an impression that some great witch had imposed on a poor victim the gigantic and seemingly impossible task of breaking and assorting a vast heap of coal into these separate piles within a certain time—a task which also seems to have been miraculously and successfully performed within such an exceedingly short time as to either satisfy or confuse the presiding evil genius.

Modern civilisation has been developed mostly from steam and coal, and they have been to each other as strong brothers, growing more and more mutually dependent to meet the demands made upon them.

The mining of coal, and its subsequent treatment for burning, before the invention of the steam engine, were long, painful, and laborious tasks, and the steam engine could never have had its modern wants supplied if its power had not been used to supplement, with a hundredfold increased effect, the labour of human hands.

It being impracticable to carry steam or the steam engine to the bottom of the mine for work there, compressed air is there employed, which is compressed by a steam engine up at the mouth. By this compressed air operated in a cylinder to drive a piston, and a connecting rod and a pick, a massive steel pick attached to the rod may be driven in any direction against the wall of coal at the rate of from ninety to one hundred and twenty blows per minute; and at the same time the discharged compressed, cold, pure, fresh air flows into and through the mine, affording ventilation when and where most needed.

In addition to these great drills, more recent inventors have brought out small machines for single operators, worked by the electric motor.

After the coal is lifted out, broken and assorted, it needs to be washed free of the adhering dust and dirt; and for this purpose machines are provided, as well as for screening, loading and weighing. The operations of breaking, assorting and washing are often combined in one machine, while an intermediate hand process for separating the pieces of slate from the coal may be employed; but additional automatic means for separating the coal and slate are provided, consisting in forcing with great power water through the coal as it falls into a chamber, which carries the lighter slate to the top of the chamber, where it is at once drawn off.

The chief of machines with ores is the ore mill, which not only breaks up the ore but grinds or pulverises it.

Some chemical and other processes for reducing ores have been referred to in the Chapter on Metallurgy.

Other mechanical processes consist of separators of various descriptions—a prominent one of which acts on the principal of centrifugal force. The crushed material from a spout being led to the centre of a rapidly rotating disk is thrown off by centrifugal force; and as the lighter portions are thrown farther from the disk, and the heavier portions nearer to the same, the material is automatically assorted as to size and weight. As the disk revolves these assorted portions fall through properly graded apertures into separate channels of a circular trough, from whence they are swept out by brushes secured to a support revolving with the disk.