The speed quoted by Carnkie as to the rev's of a Hockin & Oxland calciner is a little slow, these revolved at between 6 and 8 rev's per hour otherwise there would be little advantage over the Brunton. also in most cases the inclination would be 1 in 24.
In the drawing A is the cylinder lined with fire-brick,set at a slight inclination and supported on rollers. B is a screw which brings down a regular supply of ore from a hopper. The ore travels along very gradually in the direction of the arrow and then drops into chamber C.
D is the fireplace opening into the lower end of the cylinder, and E is the beginning of the flues in which the arsenious acid is condensed and through which the sulfurous acid passes on its way to the chimney. The longitude ribs of fire brick, extending two-thirds of the length of the furnace from the lower end, serve to lift up the charge and let it fall, so as to expose new surfaces to the action of the air.
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