1880
effective hauling machinery was substituted for the carts, and the
precious ground was extracted so rapidly that the depth of about five
hundred feet was reached in the open working, a point probably beyond
any attained in the other pits. Here, too, as at De Beers, there was an
effort to protect the mine by cutting back the reef in terraces ; but
this safeguard was tried too late, and in any event it could only have
deferred for a few years the fate of the mine. Before the close of the
year 1889 almost the whole of the pit bottom was covered with fallen
reef and only four engines were at work hauling blue ground.
The Extraction of the Diamonds
While
the sinking of the pits was progressing with improved mining
appliances, there had been a considerable advance in the methods of
concentrating the diamond-bearing ground and win-
