and
Kimberley mines, Cornish pumping plants were put in, by means of which
all the water is now pumped from the mines. The average quantity of
water taken from De Beers mine is 435° gallons an hour, and from
Kimberley, 8385 gallons. Nearly half of the latter influx comes from a
crevice at the junction of the quartzite with an intrusive dike of
igneous rock which was struck while driving the 1200-foot tunnel at a
distance of 600 feet from the mine. While no water is found in the
blue ground or mine itself, that which flows into the mine from the
surrounding rock mixes, as before described, with the debris which has
fallen into the worked-out portion of the De Beers and Kimberley mines,
and makes mud. Enormous quantities of this mixture are from time to
time forced suddenly into the working parts of the mine, which are
connected by tunnels with the loose debris. At times hundreds of feet
of tunnels were filled in a few minutes. Mud rushes became so frequent
that the working of the mines was seriously interfered with, and the
loss of life was very great.
At
Kimberley mine, large springs of water flowed into the open works at
the junction of the melaphyre with the shale. Only a small part of the
melaphyre was then exposed to view, and the position of the other part
was unknown. A tunnel was started from the Standard shaft, and driven
to the south around the mine. Another tunnel was started from the
Harvey shaft and driven to the west end around the mine in the opposite
direction until the two tunnels met. The total length was 2097 feet.
Through these tunnels all the surface water and all water coming into
the mine above the melaphyre was taken up and led to the pumps by means
of pipes. All water which enters the mine in the deeper workings is
taken down in passes, sunk in the rock outside of the mine. By these
precautions mud rushes have been completely stopped in Kimberley mine,
and none have occurred for many years past.
De Beers mine has not been so fortunate, and mud rushes are of frequent occurrence, although the quantity of water in
