And, lastly, the sluice begat the jet, or hydraulicking proper, which is at present the highest effort of placer-mining. We thus reverse the primitive process which carried the wash-dirt to the water; we now carry the water to the wash-dirt. In California I found the miners washing down loose sandstones and hillocks of clay, passing the stuff through sluices, and making money when the gold averaged only 9d. and even 4d. to the ton. A man could work under favourable circumstances twenty to thirty tons a day. An Australian company, mentioned by Mr. R. Brough Smyth, with 200 inches of water, directed by ten hands, 'hydraulicked' in six days 224,000 cubic feet of dirt. The results greatly vary; in some places a man will remove 200 cubic yards a day, and in others only 50.
Hydraulic mining on the Gold Coast, owing to the conformation of the country, will be a far simpler and less expensive process than in California or Australia. In the latter water has first to be bought, and then to be brought in pipes, flumes, leats, or races from a considerable distance, sometimes extending over forty miles. It is necessary to make a reservoir for a fall. The water then rushes through the flexible hose, and is directed by a nozzle against the face of the excavation. The action is that of a fireman playing upon a burning house. Most works on mining insist upon those reservoirs, and never seem to think of washing from below by the force-pump.
I have shown that the surface of the lands adjoining the Ancobra is a series of hummocks, rises, and falls, sometimes, though rarely, reaching 200 feet; that water abounds, and that it is to be had gratis. In every bottom there is a drain, sometimes perennial, but more often a blind gully or creek, [Footnote: The gully feeds a 'creek,' the creek a river.] which runs only during the Rains, and in the Dries carries at most a succession of pools. Here Norton's Abyssinian tubes, sunk in the bed after it has been carefully worked by the steam-navvy for the rich alluvium underlying the surface, would act like pumps, and dams would form huge tanks. Nor would there be any difficulty in making reservoirs upon the ridge-tops, with launders, or gutters, to collect the rain. Thus work would continue throughout the year, and not be confined, as at present, to the dry season. A pressure of 100 to 200 lbs. per square foot can easily be obtained, and the force of the jet is so great that it will kill a man on the spot. The hose should be of heavy duck, double if necessary, rivetted and strengthened by metal bands or rings—in fact, the crinoline-hose of Australia. Leather would be better, but hard to repair in case of accidents by rats; guttapercha would be expensive, and perhaps thin metal tubes with flexible joints may serve best. The largest hose carried by iron-clads measures 19 to 20 inches in diameter, and is worked by 30 to 40 horse-power. Other vessels have a 15-inch hose worked by manual labour, fifty men changed every ten minutes, and will throw the jet over the royal yards of a first-class man-of-war. The floating power-engines attached to the Dockyard reserves would represent the articles required.
With a diameter of from ten to fifteen inches, and a nozzle of three to four inches, a 'crinoline-hose' will throw a stream a hundred feet high when worked by the simplest steam-power process, and tear down a hill more rapidly than a thousand men with shovels. The cost of washing gravel, sand, and clay did not exceed in our colonies 1d. to 2d. per ton; and thus the working expenses were so small that 4d. worth of gold to the ton of soft stuff paid a fair profit. Lastly, there is little danger to the miner; and this is an important consideration.
It is well known that California was prepared for agriculture and viticulture by 'hydraulicking' and other mining operations. It will be the same with the Gold Coast, whose present condition is that of the Lincolnshire fens and the Batavian swamps in the days of the Romans. Let us only have a little patience, and with patience perseverance, which, 'dear my Lord, keeps honour bright.' The water-jet will soon clear away the bush, washing down the tallest trees; it will level the ground and will warp up the swamp till the surface assumes regular raised lines. We run no risk of covering the face of earth with unproductive clay. Here the ground is wanted only as a base for vegetation; sun and rain do all the rest. And thus we may hope that these luxuriant wastes will be turned into fields of bustling activity, and will tell the tale of Cameron and me to a late posterity.
But gold is not the only metal yielded by the Gold Coast. I have already alluded in the preceding pages to sundry silver-lodes said to have been worked by the old Hollanders. As is well known, there is no African gold without silver, and this fact renders the legend credible. Even in these dullest of dull days 63,337l. worth was the export of 1880. Iron is everywhere, the land is stained red with its oxide; and manganese with cobalt has been observed. I have mentioned that at Akankon my companion showed me a large vein of cinnabar. Copper occurs in small quantities with tin. This metal is found in large veins streaking the granite, according to M. Dahse, who gave me a fine specimen containing some ten and a half per cent. of metal. He has found as much as twelve per cent., when at home 2 to 2-1/2 per cent. pays. [Footnote: 'The present percentage of block-tin derived from all the tin-ore ... of Cornwall is estimated at 2 per cent., or nearly 45 lbs. to the ton of ore.'—Davies, p. 391.] The aspect of the land is diamantiferous; [Footnote: I hear with the greatest pleasure that a syndicate has been formed for working the diamond-diggings of Golconda, a measure advocated by me for many years. Suffice to say here that the Hindús rarely went below 60 feet, because they could not unwater the mine, and that the Brazilian finds his precious stones 280 feet below the surface. Moreover the Indian is the only true diamond: the Brazilian is a good and the Cape a bad natural imitation.] and it has been noticed that a crystal believed to be a diamond has been found in auriferous gravel. In these granitic, gneissose, and quartzose formations topazes, amethysts and sapphires, garnets and rubies, will probably occur, as in the similar rocks of the great Brazilian mining-grounds. The seed-pearl of the Coast-oyster may be developed into a tolerable likeness of the far-famed pear-shaped Margarita of Arabian Katifah, which was bought by Tavernier for the sum, then enormous, of 110,000l.
Pearl-culture is an art now known even to the wild Arab fisherman of the far Midian shore. Lastly, the humble petroleum, precious as silver to the miner-world, has been found in the British Protectorate about New Town.