Correspondence. the Concentration and Sizing Of
90 DISCCSSIO-U ON SIZING OF CRUSHED NIBEEhLS. [Minutes Of Mr. Commans. Au!hor, when speaking of the digiculty of screening particles less than l& to 1 nlillimetre in diameter, was referring to screening in a wet condition, as commonly was the case with ore, and did not intend to referto thescreening or sieving of drymaterial, as Mr. J. H. Saunderson would seem to suppose. On the other hand, undoubtedly, even withdry material, a difficulty wasoften experienced with fine sieves of the meshes getting choked ; and if that was obviated in themachine referred to byMr. Saunderson, it was certainlya step in the right direction. With Mr. Garland's remarks about the jigger bottom having a forward inclination, he quite agreed. That plan should never be adopted, and whatever fall was required toassist the movement of the ore shouldbe obtained by slightly lowering each successive sieve, or the depth of the bedding, the sieves themselves remaining horizontal. Correspondence. JIr. Bartsch. Mr. W. J. BARTSCH,of Siegen,supplemented theAuthor's description by some details of results obtained with the Bartsch concentrator. As wouldbe seen from Figs. 45, that appliance consisted of a convex circular table carried at the centre on a bearing b, and at the circumference by rollers c. Radial blows were imparted by a cam f, and the slime and wash-water dis- tributors revolved over thetable, the main water-pipe being bent in a parabolic curve. The usual diameter of the table was 134 feet. For every 30 revolutions of the shaft, 120 bumps were imparted to the table, in which time(one minute) the distributors made half a revolution of the table.
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