The ice must expand somewhere, and chooses the spot where least resistance is offered to it. Consequently, it expands in the india-rubber tube, but does not break it, and, when the thaw comes, there is no overflow of water.
Man utilises this power of ice in stone-splitting. Instead of taking the trouble to cut the stone by manual labour, the workmen bore a series of holes, fill them with water, insert tightly a wooden plug to prevent the ice, when formed, from oozing out of the holes, and leave the rest for the frost to do.
A like effect is produced in the warm weather by substituting similar plugs, but quite dry, having been baked for hours in an oven, for the purpose of driving out every particle of moisture. These plugs are hammered into the holes as deeply as they will go, and there left. Even if there be no rain, the nightly dews make their way into the pores of the dry wood, and cause it to swell with such irresistible force that the stone is split with scarcely any manual labour on the part of the workmen.
Yet another plan for cutting hard stones. Some of my readers may be aware that a singularly ingenious instrument has been invented for cutting boles in granite and other hard rocks. It is called the Diamond Drill, because its tip is armed with uncut diamonds.
It is necessary that the diamond should not be cut, as the natural edges are needed. A glazier’s diamond, for example, is always set as it came out of the mine. The stories that are told about cutting out panes of glass with a diamond ring are all absurd. A diamond, when it has once passed through the hands of the jeweller, cannot cut glass. It can scratch glass, but not one whit better than a flake of ordinary flint.
It is found that the Diamond Drill works with wondrous rapidity, cutting away the stone with ease, and suffering scarcely any damage itself. The tube to the end of which the diamonds are fixed is generally made in telescopic fashion, so as to allow it to penetrate deeply into the rock, without the necessity of shifting the machine by which it is turned. I need hardly say that its rate of speed is very great indeed.
Our old friend, the Gad-fly, again affords an example of a parallel.
The ovipositor is tubular, telescopic, and furnished at the top with five little hard, sharp, scaly knobs, which act the same part as the diamonds of the mining tool. Even the scoop-like shape of the tip, and the telescopic shaft, are almost identical in both instances.