from the mines the blueground is conveyed to the floors —
large flat areas — where it i sleft from three to six months, or more,
to soften. These floors are very large, those of the DeBeers and
Kimberley mines covering two thousand acres. The blueground on the
floors is harrowed by steam traction engines to assist in pulverizing
the ground. This, with the action of the sun and rain, finally
disintegrates the material so that it can be taken to the washing
machines or pulsators, as they are technically called. The
yield of diamonds per load of blue-ground is very small, but by the
careful and comprehensive methods used, practically no diamonds are
lost and the total yield is very large. Of the South African mines the
Kimberley and DeBeers have until recently produced most of the
diamonds. These mines have now been worked so deep, about three
thousand feet, that, owing to the heat and danger at that depth, they
are at present considered about worked out and comparatively, few
stones now come from these mines. The Dutoitspan mines are at present
the largest producing mines in South Africa, and give very sound
material, about the same as that of the Kimberley, DeBeers, and
Wes-selton. The Bulfontein in point of production is the second largest
mine under the DeBeers
