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 inches 95 times per minute, 1·33 h.p. ” 750 ” ” ” ” 1·18 ” ” 650 ” ” ” ” 1·00 ” For an 8-inch by 10-inch Blake pattern rock-breaker 9·00 ” For a Frue or Triumph vanner, with 220 revolutions per minute,0·50 ” For a 4-feet clean-up pan, making 30 ” ” 1·50 ” For an amalgamating barrel, making 30 ” ” 2·50 ” For a mechanical batea, making 30 ” ” 1·00 ” The writer has had small practical experience of the working of that excellent hydraulic motor, the Pelton wheel, but if by horse-power in the table given is meant nominal horse-power, it appears to be high. Working with 800 cwt. stamps, 80 blows a minute, 1 h.-p. nominal per stamp will be found sufficient with any good modern engine, which has no further burden than raising the stamps and pumping the feed water. It is always well, however, particularly when providing engine power, to err on the right side, and make provision for more than is absolutely needed for actual battery requirements. This rule applies with equal potency to pumping engines. TO AVOID LOSS IN CLEANING UP. The following, is a hint to quartz mill managers with respect to that common source of loss of gold involved in the almost inevitable loss of mercury in cleaning up operations. I have known hundreds of pounds’ worth of gold to be recovered from an old quartz mill site by the simple process of washing up the ground under the floor.