http://b4hntuy3fimfh2227vf4f74emnya7p35i5brtqujs6leqvtclfwvjbqd.onion/doc/physics/diamonds-crookes/The%20Project%20Gutenberg%20eBook%20of%20Diamonds,%20by%20William%20Crookes..html
The depositing floors are prepared by
removing the bush and grass from a fairly
level piece of ground; this ground is then
rolled smooth and hard. The floors extend
over many square miles of country and [47] 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.