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 covered with steel sieving with holes from Je to f of an inch in diameter. The five sizes which pass through the cylinder flow upon a combination of jigs, termed at the mines the pulsators. The bottoms of the jigs are covered with screens, or sieving, the meshes of which are a little larger than the holes in the revolving cylinder immediately at the back of them.
Over each screen is spread a layer of bullets to prevent the rich deposit from passing too rapidly through the screens. The jigs themselves are stationary, but from below an intermittent stream of water passes in rapid pulsations with an up and down movement. This pulsation keeps the diamantiferous gravel constantly moving " alive " is the expressive word used and tends to sort out the constituents roughly according to their specific gravity,
S3
