|
104
GOLD MESXJG IX GEORGIA.
|
||
|
|
||
|
may be shut off as necessity requires. The lift is set into the slate to such depth as may he desired, and connection is made with the water-supply pipe. The discharge-pipe is then slipped over the throat and the discharge-flume is put in place, the discharge-pipe being set at such an angle of inclination as may be necessary to give proper grade to the tailings-flume and allow the pipe to extend a few inches through the bottom of the hooded box.
The air-pipe, E, is then screwed into place, and the lift is ready for operation. We govern the depth to which we set the lift into the bed-rock slate by the hardness or softness of the latter. If it be hard, frequent moving is cheaper than cutting slate-drains. If soft, we go as deep as the slate will stand without timbering. This we find to be about 7 feet.
A main drain is then started in the general direction of our work, from which laterals are afterwards cut as required; and, at some suitable place near the lift-pit, a box about 6 feet long by 32 inches wide is set into the drain at grade, and in this is placed a cast-iron " grizzly " having round holes 2% inches in diameter. This catches any rocks which may escape the forkers, and insures that nothing will get to the lift which will not readily pass through the throat, which has, when new, an opening of three inches.
We use straight-bar riffles in the discharge-flume to catch any gold that may pass through the lift. This we find in practice to be about 5 per cent, of the total amount recovered, a result largely due to the fact that, when work is started at a new pit, the ground-sluices are not long enough to settle the gold thoroughly.
Whenever the drainage afforded by a pit is exhausted the pipe-line is extended, a new pit is sunk near the gravel-breast, and the work is continued as before.
As the work follows the general course of the river, the tailings are discharged into the river at the nearest point, the portable tailing-Hume being extended far enough to insure the safety of the immediate bank. The tailings finally flow through a ditch into the river.
We usually use about 200 feet of 5-inch pipe in the lift water-supply before extending the 9-inch pipe-line; and we often move up 100 feet, dig the pit. re-ser the lift and get ready for work again in one 12-hour shift with 5 men.
As to the work which the lift will accomplish. I may say that we are using a lift with 1%-inch nozzle, discharging through a 3-inch throat into a 0-inch pipe. and lifting an average of 18 feet vertically, with water at about i';i'i pounds pressure per square inch.
As we are quite near the river, and have the drainage of a side-hill, the surface-water is considerable, probably fifty gallons per minute. We use a lti-ineh nozzle on the giant, and the lift readily handles all this and all The dirt and gravel we are able to wash to it. The latter we estimate, from measurements taken at different times, to be about V. cubic yard per minute of ' topping.' The quantity of gravel is hard to determine, owing to varying conditions: but it is safe to say that it is all that the amount of water employed will wash."
"Water is supplied to both the elevator and the giant by direct pressure (about 60 pounds to the square inch) from the Blake pump. This direct appliance of pressure, without intermediate stand-pipe or reservoir, has proved very successful, the only precaution necessary being tn shut off the pump before closing the feed of the giant or elevator. Tt
|
||
|
|
||