THE COMBINED SYSTEM
Under some conditions it is found convenient to employ both suction and blast in combination: suction to draw the grain from a vessel's hold into elevators, from which it is transferred to the warehouse by blast. Special boats are built for this work, e.g. the Garryowen, which has on board suction plant for transferring grain from a ship to barges, and also blowing apparatus for elevating it into storehouses or into another ship. The Garryowen has the hull and engines of an ordinary screw steamer, so that it can ply up and down the Shannon and partly unload a vessel to reduce its draught sufficiently to allow it to reach Limerick Docks. Floating elevators of this kind are able to handle upwards of 150 tons of grain per hour.
[CHAPTER XVII]
MECHANICAL TRANSPORTERS AND CONVEYERS
MECHANICAL CONVEYERS — ROPEWAYS — CABLEWAYS — TELPHERAGE — COALING WARSHIPS AT SEA
A man carrying a sack of coal over a plank laid from the wharf to the ship's side, a bricklayer's labourer moving slowly up a ladder with his hod of mortar—these illustrate the most primitive methods of shifting material from one spot to another. When the wheelbarrow is used in the one case, and a rope and pulley in the other, an advance has been made, but the effort is still great in proportion to the work accomplished; and were such processes universal in the great industries connected with mining and manufacture, the labour bill would be ruinous.
The development of methods of transportation has gone on simultaneously with the improvement of machinery of all kinds. To be successful, an industry must be conducted economically throughout. Thus, to follow the history of wheat from the time that it is selected for sowing till it forms a loaf, we see it mechanically placed in the ground, mechanically reaped, threshed, and dressed, mechanically hauled to the elevator, mechanically transferred to the bins of the same, mechanically shot into trucks or a ship, mechanically raised into a flour-mill, where it is cleaned, ground, weighed, packed, and trucked by machinery, mechanically mixed with yeast and baked, and possibly distributed by mechanically operated vehicles. As a result we get a 2-lb. loaf for less than three-pence. Anyone who thinks that the price is regulated merely by the amount of wheat grown is greatly mistaken, for the cheapness of handling and transportation conduces at least equally to the cheapness of the finished article.
The same may be said of the metal articles with which every house is furnished. A fender would be dearer than it is were not the iron ore cheaply transported from mine to rail, from rail to the smelting furnace, from the ground to the top of the furnace. In short, to whatever industry we look, in which large quantities of raw or finished material have to be moved, stored, and distributed, the mechanical conveyer has supplanted human labour to such an extent that in lack of such devices we can scarcely conceive how the industry could be conducted without either proving ruinous to the people who control it or enhancing prices enormously.
The types of elevators and conveyers now commonly used in all parts of the world are so numerous that in the following pages only some selected examples can be treated.
Speaking broadly, the mechanical transporter can be classified under two main heads—(1) those which handle materials continuously, as in the case of belt conveyers, pneumatic grain dischargers, etc.; and (2) those which work intermittently, such as the telpher, which carries skips on an aerial ropeway. The first class are most useful for short distances; the latter for longer distances, or where the conditions are such that the material must be transported in large masses at a time by powerful grabs.
Some transporters work only in a vertical direction; others only horizontally; while a third large section combine the two movements. Again, while some are mere conveyers of material shot into or attached to them, others scoop up their loads as they move. The distinctions in detail are numerous, and will be brought out in the chapters devoted to the various types.