TREATMENT OF SULPHURET OKES AT CHARACTERISTIC MINES. 135
stopes can be filled from the surface and the ore in the pillars, {. e., what is left toward the hanging wall, can be taken out.
Blasting is done with 40 per cent. Hercules powder. One-inch steel is iL-'ed for both hand and machine-work. The number of air-drills is limited by the size of the compressor an Ingersoll machine, with 3-drill capacity. The ore is carried from the loading-chutes to the shafts in sheet-iron cars of ^-ton capacity, running on 18-inch gauge track. At Xo. 2 Shaft (7x12 feet, single compartment) they are hoisted by cage, with automatic safety catch. The new shaft is 6x14 feet, double compartment, and the ore is raised by a novel skip designed by Mr. Thies (fig. 25). The body of the skip, made of sheet iron, has two projecting lugs riyeted to it below the centre of grayity and the bail is lugged one inch from the vertical centre line.
Each lug runs between a pair of yellow-pine guides set 2 inches apart. When the skip is raised above the landing-chute two iron pins are thrown across the openings between each set of guides. The skip is dropped down on these and the ore is dumped into a loading-chute placed on the heavier side of the skip. The skip is raised and righted by the bail, the iron pins are withdrawn by the lander, and the skip descends. The operation is rapid and simple and the cost of the device is light. The mine is not wet, a Xo. 9 Cameron pump easily handling the water.
MILLING AND ORE TREATMENT AT THE HAILE MINE.
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The ore is crushed to 1-J-inch size in a 10x20-inch Blake crusher at the Beguelin, and a 7xl0-inch crusher at the Cross mine, and is stored at both places in bins of 30 tons capacity. The broken ore is hauled to the mill in narrow-gauge, bottom-dumping cars, holding 3 tons; 8 cars are run to the trip. The mill bin has a capacity of 300 tons, and is so arranged that every stamp can be supplied separately with ore, as, owing to the different character of the ore at the Beguelin and the ITaile, it is treated in separate batteries. A hinged plate, not shown in the accompanying illustration, is for this purpose hung at the apex of the bin floor. A vertical cross-section of the mill is shown in fig. 26. Two vertical sections of a similar battery at the Reimer mine are shown in fig. 19 (p. 120).
The mill is a 60-stamp back-to-back one, 30 on each side, built by the Mecklenburg Iron Works of Charlotte, X. C. The ore is fed by Hendey self-feeders. The weight of the stamps is 750 pounds; chilled iron shoes and dies are used; the stamps drop 6 inches, 86 times per minute, in the order 1, 3, 2, 5, 4. The crushing capacity is 2 tons to the stamp in 24 hours. The screens are 30-mesh, made of Xo. 20 brass wire; these work well if no cyanide is used in the battery. The average height of
