At Kimberley mine nine levels are being worked, from the 1840-foot to
the 2160-foot level inclusive. The galleries are not supported in any
way by timbers, but all tunnels in soft blue
ground are timbered with sets of two props and a cap of round timber, and are covered with inch and a half lagging.
blue ground is drilled with long jumper drills sharpened at both ends.
In hard blue ground, drills and single-hand hammers are used. The
native workers become very skilful in both methods of drilling, and do
quite as much work as white men would do under similar conditions.