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south African diamonds (Continued)
The
average output from each mine today is over 5,000 sixteen cubic foot
truck loads during an eight hour shift, which is equal to 4,000 tons.
The ground is loaded into trucks, mechanically transported to the main
rock shaft and loaded into the hoisting skips. At one time electric
locomotives were used for haulage purposes, but these have been
discarded and an endless rope engaging with jockeys on the top of the
trucks is now in use. The rope is driven by electric motors through
suitable gearing. Each skip in the main shaft holds ten of these
trucks, and to prevent confusion at the shaft the full trucks are
attached to the haulage rope in spans of five. The full trucks as they
run past the loading box are automatically tipped, ten truck loads
being fed alternately into each half of the box. When a hoisting skip,
after its trip to the surface, arrives at the bottom of the shaft, it
comes to rest upon a strong carrying beam so placed that the upper lip
of the skip is just below the door of the loading box. The door is
opened by means of a machine operated by compressed air, and the ten
loads which have, during the time occupied by the trip, been tipped
into the box slide into the skip at once. The box door is closed and
the signal is given to the engine driver at the surface for him to
commence his wind. The time occupied in filling the skip is about five
seconds.
At
first diamonds were found only on the surface. It was soon learned that
diamonds were found twenty feet below the surface. After this was
learned, mining started in earnest. Two farms were sold for a few
thousand dollars
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