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336 THE DIAMOND MINES OF SOUTH AFRICA
this mine is only about one-half that of the Kimberley mine. The following work is being done with the view of preventing them. A tunnel is being driven around the mine at the hard rock (melaphyre) level, about 380 feet from the surface, in order to take up the water which flows into the open mine below the shale. Tunnels are also being driven on the 1000-foot level on the south and east sides of the mine, which will be continued until they meet. Diamond drills are at work making holes between levels, with the view of tapping the water. Everything feasible will be done to free De Beers mine from the plague of water as perfectly as it has been done at Kimberley mine. The problems are not the same, however, for in Kim­berley mine the debris had followed down as the blue ground was extracted, and had left the hard rock more or less exposed to view, and one could see in places where the streams of water flowed into the open mine; but in De Beers no hard rock has been exposed until lately, and one must grope in the dark, as it were, to find out where the water enters the open or worked-out portions of the mine.
The pumping plants for freeing the mines from water have kept pace fully with the advance in the hoisting plants. For the service of De Beers mine, a new pumping engine was erected at the rock shaft in 1889. This is a compound sur­face-condensing engine made by James Simpson & Company, of London. Its high-pressure cylinder is 14-3/64 inches diam­eter, and its low pressure, 21 inches, with a stroke of 30 inches, It is capable of developing 120 horse-power. With this engine an average of nearly 6000 gallons an hour was readily drained from the mine from the start, and no difficulty was experienced in lift­ing over 8000 gallons an hour at times. The cost of pumping is largely offset by using the water drained from the mine for washing the pulverized blue ground. By combining this sup­ply with that obtained from surface reservoirs, enough water was obtained for the use of the concentrating plants, except in very dry seasons. For the Kimberley mine a Cornish pumping plant of 400 horse-power, from designs by the late Mr. L.I.