cury, to then empty into the stamper box two
or three pounds weight; with what effect may be easily surmised.

HOW WATER SHOULD ENTER STAMPER BOXES

The following extract which relates to Californian Gold Mill practices
is from Bulletin No. 6 of the California State Mining Bureau. I quite
agree with the practice.

"The battery water should enter both sides of the mortar in an even
quantity, and should be sufficient to keep a fairly thick pulp which
will discharge freely through the grating or screen. About 120 cubic
feet of water per ton of crushed ore may be considered an average, or 8
to 10 cubic feet per stamp per hour.

"Screens of different materials and with different orifices are used;
the materials comprise wire cloth of brass or steel, tough Russian sheet
iron, English tinned plate, and, quite recently, aluminium bronze. The
'aluminium bronze' plates are much longer lived than either of the other
kinds, and have the further advantage that, when worn out, they can be
sold for the value of the metal for remelting; these plates are bought
and sold by the pound, and are said to contain 95 per cent of copper and
5 per cent of aluminium. Steel screens are not so much used, on account
of their liability to rust."

I have had no experience with the aluminium bronze screen. I presume,
however, that it is used only for mills where mercury is not put in the
mortars, otherwise, it would surely become amalgamated. The same remark
applies to brass wire cloth and tinned plate. Unless the metal of which
they are composed will not readily amalgamate with mercury, I should be
chary of using new screen devices. Mercury is a most insidious metal
and is often found most unexpectedly in places in the battery where
it should not be. Probably aluminium steel would be better than any
substance mentioned. It would be hard, light, strong, and not readily
corrodible. I am not aware if it has been tried.

Under the heading of "Power for Mills" the following is taken from the
same source.

POWER FOR MILLS

"As the Pelton wheel seems to find the most frequent application in
California, it may be convenient for millmen to have the following rule,
applicable to these wheels:

"When the head of water is known in feet, multiply it by 0.0024147,
and the product is the horse-power obtainable from one miner's inch of
water.

"The power necessary for different mill parts is:

For each 850lb. stamp, dropping 6 in. 95 times per minu