. Transactions. 30 A COMPARISON OF GRAlN-SlZE MEAStJREMENTS It is also described by Zay Jeffries and others.^ A circle mm. indiameter was used in counting and the diameter of the average grain inmillimeters was determined. The following formulas, proposed by , were used: w = boundary grains; z = completely included grains; X = equivalent number of whole grains in 5000 sq. mm. (circle diameter or rectangle having area of 5000 sq. mm.); m = magnification used; f = multiplier to obtain grains per square millimeter; n = number of grains per square millimeter; d = diameter

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. Transactions. 30 A COMPARISON OF GRAlN-SlZE MEAStJREMENTS It is also described by Zay Jeffries and others.^ A circle mm. indiameter was used in counting and the diameter of the average grain inmillimeters was determined. The following formulas, proposed by , were used: w = boundary grains; z = completely included grains; X = equivalent number of whole grains in 5000 sq. mm. (circle diameter or rectangle having area of 5000 sq. mm.); m = magnification used; f = multiplier to obtain grains per square millimeter; n = number of grains per square millimeter; d = diameter of average grain in millimeters; a = area of average grain in U^. -y2W + z / = 500. 1 1,000,000 ?\/n X = n = fx d = n n Tables 2, 3, and 4 give a resume of the results obtained. Table 2.—Brinell Hardness and Grain Size on 69-31 Brass (See Fig. 2) Bar No. 1. Rolled from in. to in. ( mm. to mm.), Reduction by rolling per cent. (4 —B. & S. numbers. Hard) Anneal. Temp., Degrees \/n Av. BrinellNumber fromTwo Imp. andFour Readings 850800 750 700 650 600 S50 600 450 425400375350325300275250200Hard. i i I I

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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries