314 THE DIAMOND MINES OF SOUTH AFRICA
The
plans on other pages illustrate the manner in which the various levels
were laid off. Tunnels were driven across the crater at De Beers mine
from west to east, about 120 feet apart, and galleries 18 feet wide and
18 feet high were opened every 36 feet along the main tunnels, and were
worked up to within 12 feet of the loose ground in the top levels.
Pillars of solid blue ground 18 feet thick were left between the
galleries, but later on first the roof and then the pillars were taken
out.
This
method of mining was fairly successful for a time; but, as already
stated, as depth was attained, the roofs of the galleries or rooms
became unsafe before the galleries were opened through to those on the
next level above, and they frequently gave way, thus making the
extraction of the blue ground exceedingly difficult. This system was
both expensive and dangerous. No timber was used except in the main
tunnels or drifts, the nature of the blue ground being such that the
roofs and sides of the excavations stood fairly well for a short time,
provided they were well ventilated.
In
other parts of De Beers mine various companies were working or trying
to work underground ; but as no regular system of mining could be
carried on owing to the irregular shape of their holdings, and the more
or less temporary methods adopted, it was clearly impracticable to
devise and carry into effect any comprehensive system of operation for
the rapid and economical handling of the diamond-bearing breccia in the
craters, until the union of all the claims through the formation of one
controlling company permitted the installation of a single uniform
system of mining.
It has already been narrated how this was effected for De Beers mine during the year 1887, by the combination
of all the holdings in the mine into one company, and the organization
of De Beers Consolidated Mines Limited, in March, 1888. Kimberley mine
came formally into the possession of this great corporation on the 1st
of June, 1889, and controlling interests in the other two mines,
Dutoitspan and Bultfontein, were also secured. The assured control of
all the mines and their opera-
