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Jan 1, 1938

Jan 1, 1938

Jan 1, 1938

Jan 1, 1940

Jan 1, 1940

Jan 1, 1938

Jan 1, 1943

Jan 1, 1945

Jan 1, 1943

Jan 1, 1920

Jan 1, 1899

Jan 1, 1916

Jan 1, 1888

By James Harding

THE usual method of sampling mineral deposits is to drill holes and assay the sludge or core. Though the results thus obtained may not represent the true average value of the deposit, it is on these results that estimates of practically all large orebodies are made. In a large number of cases, the results of exploitation fall far short of the estimated value of the orebody. The standard method of making these estimates is to find the cubic contents of triangular prisms, in the apexes of which the drill holes are placed, .by multiplying the surface area by the average depth of the ore in the three drill holes and then multiplying the cubic contents by the specific gravity of the ore or rock to find the tonnage. The assay value is found by dividing the sum of the products of the depth of ore in each hole and the corresponding assay value by the sum of the depths of the ore in the three holes. As the latter part of this method is subject to many mathematical errors, it should not be depended on.. Some engineers, therefore, use a discount factor, but as this factor is either arbitrarily selected or is obtained by obscure methods, the results are no better than guesswork. The standard method is correct when the drill holes are so laid out that the triangular prisms are equilateral in cross-section. But as ore deposits cannot always be drilled into at regular intervals and because of the human factor, if many holes are drilled, triangular prisms of all degrees of angularity are produced. In such cases, it is necessary to assume that the influence of the different holes is not the same in all directions, which assumption of course is absurd.

Jan 1, 1921

By Louis Ware

A leading executive finds this a bad time to "cry" about taxes. Needed reforms must cede to emergency demands.

Jan 7, 1951

Jan 1, 1882

[PRESIDENT AND DIRECTOR H. G. MOULTON3 NEW YORK, N. Y. PAST PRESIDENTS AND DIRECTORS - D. C. JACKLING1 SAN FRANCISCO, CALIF. DONALD B. GILLIES2 CLEVELAND, OHIO TREASURER AND DIRECTOR KARL EILERS3 SEA. CLIFF, N. Y.]

Jan 1, 1940

Launching Platform - Drift Indicator- Stratascope-are components of Carbide and Carbon Chemicals new Mining Machine No. 3.

Jan 1, 1953

Jan 1, 1939