APRIL 1, 1897 | 
NATURE 
521 
of the mine. From the east and west tunnels offsets are driven 
to the surrounding rock. When near the rock, they are widened 
into galleries, these in turn being stoped on the sides until 
they meet, and upwards until they break through the blue 
ground. The fallen reef with which the upper part of the 
mine is filled, sinks and partially fills the open space. The 
workmen then stand on the fallen reef, and drill the blue ground 
overhead ; as the roof is blasted back the débris follows. When 
stoping between two tunnels, the blue is stoped up to the débris 
about midway between the two tunnels. The upper levels are 
worked back in advance of the lower levels, and the works 
assume the shape of irregular terraces. The main levels are 
from 90 to 120 feet apart, with intermediate levels every 30 
feet. Hoisting is done from only one level at a time through 
the same shaft. By this ingenious method of mining, every 
portion of blue ground is excavated and raised to the surface, 
the rubbish on the top gradually sinking down and taking its 
place. 
The scene below ground in the labyrinth of galleries is be- 
wildering in its complexity, and is about as little like one’s 
idea of a diamond mine as can well be conceived. Electric 
light is universal in the workings. One set of workers attends 
to the rock-drilling machines for blasting the blue ground ; in 
other parts the blue is shovelled into wagons, which, when 
filled, are carried along rails by moving ropes till they get to 
the gallery, where the contents are sent to the surface. 
At the bottom of the main shaft, at the 1300-foot level, the 
galleries converge to a large open space where the tram lines 
carrying the trucks meet. In front is a shoot to which the 
trucks full of blue ground are rapidly wheeled, tipped over, their 
contents discharged, when they are shunted to make way for 
other trucks. At the foot of the shoot is a skip holding 64 
cubic feet, or four truck-loads. As soon asa skip has received 
its allotted four loads an electric bell sounds at the engine house, 
when the skip is hoisted to the surface and another takes its 
place. So the work proceeds, and on busy days ground has 
been hoisted at the rate of 20 loads every three minutes, equal 
to 400 loads an hour. In 1894 the record hoisting of blue 
ground at the Kimberley mine was 470 loads an hour; in one 
shift of eight hours 3312 loads; and ina day of three shifts, 
7415 loads. 
All below ground is dirty, muddy, grimy; half-naked men, 
black as ebony, muscular as athletes, with perspiration oozing 
from every pore, are seen in every direction, hammering, pick- 
ing, shovelling, wheeling the trucks to and fro, keeping up a 
weird chant, which rises in force and melody when a titanic task 
requires excessive muscular strain. The whole scene is far more 
suggestive of a coal mine than a diamond mine, and all this 
mighty organisation, this strenuous expenditure of energy, this 
clever, costly machinery, this ceaseless toil of skilled and black 
labour, going on day and night, is just to win a few stones 
wherewith to deck my lady’s finger ! 
At the four mines about 8000 persons are daily employed, 
namely, 1500 whites and 6500 blacks. The wages are—whites, 
54. or 64. a week; blacks, underground, 4s. to 5s. a day, and 
above ground 21s. a week. 
With gems like diamonds, where so large an intrinsic value is 
concentrated into so small a bulk, it is not surprising that 
robbery has to be guarded against in the most elaborate manner. 
The Illicit Diamond Buying (I.D.B.) laws are very stringent, 
and the searching, rendered easy by the ‘‘ compounding” of the 
natives—which I shall describe presently—is of the most drastic 
character. It is, in fact, very difficult for a native employé to 
steal diamonds ; even were he to succeed, it would be almost 
impossible to dispose of them, as a potential buyer would prefer 
to secure the safe reward for detecting a theft rather than run 
the serious risk of doing convict work on the Cape Town Break- 
water for a couple of years. 
THE DEposItING FLOORs. 
Owing to the refractory character of blue ground fresh from 
the mines, it has to be exposed to atmospheric influences before 
it will pulverise under the action of water and mechanical 
treatment. 
From the surface-boxes, into which the blue ground is tipped 
when it reaches the top of the main shaft, it is transferred to 
side-tipping trucks, and sent to the depositing floors by means 
of endless wire-rope haulage. ‘ 
The depositing floors are prepared by removing the bush and 
grass from a fairly level piece of ground ; this ground is then 
NO. 1431, VOL. 55 | 
rolled smooth and hard. The floors extend over many square 
miles of country, and are surrounded by 7-foot barbed wire 
fences, vigilantly guarded day and night. The De Beers floors, 
on Kenilworth, are laid off in rectangular sections 600 yards 
long and 200 yards wide, each section holding about 50,000 
loads. The ground from the Kimberley mine is the softest, and 
only needs a few months’ exposure on the floors; the ground 
from De Beers is much harder, and requires at least six months’ 
exposure ; while some ground is so hard that it will not dis- 
integrate by exposure to the weather under one or two years. 
The De Beers mine contains a much larger quantity of this hard 
blue ground than the other mines, and, in order to save the loss 
of time consequent on keeping an enormous stock of blue con- 
stantly on the floors, it has recently been decided to pass the 
harder and more refractory stuff direct from the mine through 
crushing mills. 
For a time the blue ground remains on the floors without 
undergoing much alteration. But soon the heat of the sun and 
moisture produce a wonderful effect. Large pieces, hard as 
ordinary sandstone when taken from the mine, commence to 
crumble. At this stage the winning of the diamonds assumes 
more the nature of farming than mining. The ground is fre- 
quently harrowed and occasionally watered, to assist pulverisa- 
tion by exposing the larger pieces to atmospheric influences. 
The length of time necessary for the ground to weather before it 
becomes sufficiently pulverised for washing depends on the season 
of the year and the amount of rain. The longer the ground 
remains exposed the better it is for washing. 
In June 1895, the quantity of blue ground on the floors was 
3,360,256 loads, representing diamonds to the value of nearly 
one million sterling. The risk of robbery at this stage of the 
operations is somewhat serious, and precautions are correspond- 
ingly elaborate. A native working on the floors may come 
across a large stone and secrete it about his person. Careful 
search soon reveals this crude form of robbery. Or he may 
hide it, note its position in the field, and after working hours 
creep back and furtively secure the prize. As a safeguard five 
powerful search-lights, each of 25,000 candle-power, sweep 
across the floors all night, and guards are on the watch to pre- 
vent any unauthorised person entering the mining area, and to 
prevent natives who are working at night from leaving the floors 
without being seen. 
WASHING AND CONCENTRATING MACHINERY. 
After the blue ground has been weathered for a sufficient 
time, it is again loaded into trucks and hauled to the washing 
machinery. 
About 14 per cent. of all the ground sent to the depositing 
floors are too hard to weather, so of late years crushing and con- 
centrating plant has been erected to deal effectually with the hard 
lumps, thus saving the great lock-up of capital consequent on 
letting them lie on the floor a year or two. 
The hard lumps being hauled to the upper part of the 
machine, are tipped into bins, whence they pass to crushing 
rollers which so reduce them that they will pass through a ring 
two inches in diameter. The coarse powder is screened through 
revolving cylinders having 4 inch and rj inch perforations. The 
stuff passing through the finer holes goes to the finishing mill, 
while the coarser stuff goes to smaller crushers. Before the 
coarse lumps are re-crushed they pass over revolving picking 
tables, where any specially large diamonds are rescued, thus 
preventing the risk of breakage. Finally the crushed and 
graded stuff goes to a series of jigs, and after further concentra- 
tion the diamantiferous gravel is taken in locked trucks to the 
pulsators. 
THE PULSATOR. 
The pulsator is an ingeniously designed but somewhat com- 
plicated machine for dealing with the diamantiferous gravel 
already reduced one hundred times from the blue ground ; the 
pulsator still further concentrating it till the gravel is rich enough 
fo enable the stones to be picked out by hand. The value of 
the diamonds in a load of original blue ground being about 30s., 
the gravel sent to the pulsator from the pans, reduced a hundred- 
fold, is worth 150/. a load. Stuff of this value must not be 
exposed to risk of peculation. The locked trucks are hoisted by 
a cage to a platform, where they are unlocked, and their contents 
fed into a shoot leading to a cylinder. This cylinder is covered 
with iron plates perforated in sections with four sizes of round 
holes, 4 inch, +87 inch, } inch, and ~ inch ‘n diameter. That 
portion of the deposit too coarse to pass through the 2-inch 
