THE PNEUMATIC BLAST GRAIN-LIFTER
differs from the system just described in that the grain is driven through the pipes or hoses by air compressed to several pounds above atmospheric pressure. A small tube attached to the main hose conveys compressed air to the nozzle through which grain enters the tube. The nozzle consists of a short length of metal piping which is buried in the grain. One half of it is encased by a jacket into which the compressed air rushes. As the air escapes at high speed past the inner end of the piping into the main hose, it causes a vacuum in the piping and draws in grain, which is shot up the hose by the pressure behind it. As already remarked, the action of this pneumatic elevator is similar to that of a steam injector.
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.