ich
is seldom given. The men go out of the compounds to their work through
tunnels and return the same way.

Besides the native Kafirs already mentioned, about two thousand white
laborers are employed, the greater number being engaged in the offices
and workshops and on the depositing floors.

Electric lights are used throughout the mines, and underground work is
carried on both day and night by three shifts. Every known scientific
device is pressed into service. In all of the deep mines the laborers
are taken up and down the shafts in cages.

The method of mining and working the diamond-bearing earth at present
employed is far more economical than in former years. After the blue
material has been brought up it is carried to the depositing floors
where it is allowed to remain several months. In the meanwhile it is
harrowed several times to break the lumps. The part that resists this
treatment is carried to a mill to be crushed. The disintegrated and
pulverized material is then carried to the washing machines.

The coarser fragments of the concentrates from the washing machines are
picked out by hand; the finer are sent to the pulsators. Each
shaking-table of the pulsators is made of corrugated iron plates in
several sections with a drop of about an inch from one division to
another.

A sufficient quantity of thick grease is spread over the plates to cover
them to the top of the corrugations. The concentrates are continuously
spread over the upper portion of the table automatically while running
water washes them down.

Strange as it may seem, the diamonds stick fast to the grease; the other
material is washed away. It has been found by trial that grease will
cling to the precious stones but to nothing else. After a few hours the
grease with the diamonds is scraped off the tables and steamed in
perforated vessels to separate them.

[Illustration: Sorting gravel for diamonds in the Kimberley mine]

One of the De Beers mines has been worked to a depth of about two
thousand feet with no diminution in the quantity or quality of the
diamonds. The "pipe" or plug of blue-stuff shows no signs of giving out.
Nature, in her underground laboratory, works in a mysterious way,
baffling the astutest students of science to find the process by which
she is able to manufacture such beautiful gems as the diamond. Many
theories have been propounded to explain the genesis of the diamond, the
most plausible one being that the cryst