The modern Hydrant system, which bids fair to supersede the cumbrous machinery of fire-engines, even when worked by steam, is based on the same principle. The water-tanks are placed at such a height that, when a hose is attached, and the tap turned, the water can be thrown over the roof of the highest building. Such hydrants have been attached to Canterbury Cathedral since the fire which so nearly consumed that magnificent and venerable building.
A very remarkable use has been made of this power of water in mining operations. Most of my readers know that in gold mines the metal is chiefly found scattered among quartz, one of the hardest of the minerals. The usual plan has been to dig out the quartz, pound it to powder with specially devised machines called “stamps,” to pass the powder through mercury, which amalgamated with the gold, and gave it up again on being heated to a certain temperature.
Now a different mode of mining is brought into operation, the pickaxe, spade, and stamps, with all their expensive machinery, being abandoned, and water made to do the duty of all three, some ingenious individual having noticed the effect which water has on the hardest rock.
Such, for example, is the case with those wonderful Victoria Falls of Africa, where the rushing water has cut its sinuous channel through so many hundreds of yards of rock. Such, also, is the case with the more celebrated, but not so wonderful, Falls of Niagara, which have been gradually working their way backwards, having worn away the rocks over which they fall, and which are shown to be many miles away from the spot where the river first discharged itself over the cliff.
In fact, it is well known that the Falls are receding at a definite rate annually, and that the rate has been calculated with scientific accuracy. The cliffs of our own coasts-say of Margate or Ramsgate—crumble away with equally calculable speed.
In the hydraulic mining system large tanks are erected, at least two hundred feet above the level of the mine. From these tanks proceed pipes, terminated by hose, just like those of our ordinary fire-engines. The miners, instead of using pickaxe or crowbar, simply direct the streams of water against the solid rock. Their effect is tremendous. They tear it to powder, and carry it down the wooden troughs called “flumes,” in which the mercury is so arranged that not a single atom of quartz rock can pass without having its gold extracted.
The following graphic account of Hydraulic Mining at Nevada is taken from Mr. J. K. Lord’s “Naturalist in British Columbia:”—
“Near Nevada are the famed Hydraulic washings. The gold is disseminated through terraces of shingle conglomerates, often three hundred feet in thickness. These terraces are actually washed entirely off the face of the country by propelling jets of water against them, forced by pressure through a nozzle.
“To accomplish this, the water is brought in canals, tunnels, and wooden aqueducts, often forty miles away from the ‘draft.’ This supply of water the miners rent.