Page:Travel letters from New Zealand, Australia and Africa (1913).djvu/308

 are more than three thousand feet deep, and the diamond dirt is hoisted and treated very much as gold-bearing rock is hoisted and treated Diamonds are found in blue dirt, in what the miners call "pipes." These pipes are the craters of extinct volcanoes, and taper toward the bottom like a funnel. The pipes are round, as may be seen in the old open workings, some of which are a thousand feet deep. The deepest working in any "pipe" is now at a depth of three thousand feet, but a diamond drill has been sent down a thousand feet further without the blue dirt giving out; so no one knows how deep they are The old open holes in the ground were found very expensive to work at a depth of eight hundred or a thousand feet, so the blue dirt is now hoisted by means of modern cages operating in timbered shafts, as coal is hoisted; down below, drifts are run, and the blue dirt hauled to the hoisting-shafts as is done in coal-mining. As the blue dirt is exhausted, the shafts are sunk deeper, and drifts run lower down. The "pipe" at the biggest diamond mine at Kimberley is three hundred yards across at the top, and, as I have already said, this tapers toward the bottom like the funnel you use in pouring vinegar into a jug. The Premier mine, near Pretoria, is very much larger than any mine at Kimberley, being eight hundred yards across at the top. This great Premier mine, which you hear little of, mines forty thousand tons of blue dirt per day, and employs twelve thousand men, as against twenty thousand employed in all the Kimberley mines. The Premier dirt, however, is worth only one dollar per ton, whereas that at Kimberley averages something