. Mining and Scientific Press . f classifiers, ball-mills, concentrators, electromagnetic separators, and the like. Mr. Holmes, in your issue of May 11, is quite right inasking Why classify grinding! As certified by the experiments of Mr. Taylor stated in your issue of June IS, and by the tests conducted by Messrs. Gross andDavis at the Alaskan station of the Bureau of Mines,the main feature for successful recovery of gold from black sand is the grinding of the clean ups. and my ownpractical experience has led me to the same it all comes to the use of a cheap
. Mining and Scientific Press . f classifiers, ball-mills, concentrators, electromagnetic separators, and the like. Mr. Holmes, in your issue of May 11, is quite right inasking Why classify grinding! As certified by the experiments of Mr. Taylor stated in your issue of June IS, and by the tests conducted by Messrs. Gross andDavis at the Alaskan station of the Bureau of Mines,the main feature for successful recovery of gold from black sand is the grinding of the clean ups. and my ownpractical experience has led me to the same it all comes to the use of a cheap simplegrinding appliance. Such a one is the Berdan pan, whichsome thirty years ago was an .indispensable part of almostevery stamp-battery in Australia and New Zealand. Iventure to say that this device will solve the black-sandquestion, as it meets all the requirements of the case,doing the grinding and the amalgamation at the sametime, and not requiring any particular accompanying sketch shows the equipment. The. BEKDAN FAN pan A and the ball B (about 12 in. diam.) are of ordi-nary cast-iron and can be made in any foundry. C isa copper-plated amalgamating-table. Mercury is usedin the pan. which makes about 18 or 20 revolutions perminute. The incline of the shaft is about 60°. Thedriving gear is fixed beneath the pan to prevent oil andother greasy substances from interfering with the amal-gamation. The pan requires about J hp., and that amountcan always be taken from any steam-engine or electricmotor at work on the mine. Should this not be possiblethere generally is a ditch or a flume that can supply thewater necessary to drive the pan by a miniature over-shot wheel. The cost of installation should not exceeda couple of hundred dollars, I suppose, and the deviceis simple enough to set up anywhere, even at the mostremote placer mines of the interior of Alaska. It couldbe placed on any dredge. In working, one Berdan 424 MINING AND SCIENTIFIC PRESS September 24, 19
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