. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . k, 1868. E. B. Smyth, The Gold Fields of Victoria, 4to, Melbourne, 1869. W. P. Blake, *The Production of the Precious Metals, 8vo, New York, 1869. Von Cotta, Treatise on Ore Deposits,-by Prime, 8vo, New York, 1870. P. M. Kandall,The Quartz Operators Handbook, 12mo, 1871. GONIOMETER. Fr., Goniomètre; Ger., Gonio-meter ; Span., Goniómetro. Various instruments termed goniometers are em-ployed in the measurement of the angles of kinds are in use—th
. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . k, 1868. E. B. Smyth, The Gold Fields of Victoria, 4to, Melbourne, 1869. W. P. Blake, *The Production of the Precious Metals, 8vo, New York, 1869. Von Cotta, Treatise on Ore Deposits,-by Prime, 8vo, New York, 1870. P. M. Kandall,The Quartz Operators Handbook, 12mo, 1871. GONIOMETER. Fr., Goniomètre; Ger., Gonio-meter ; Span., Goniómetro. Various instruments termed goniometers are em-ployed in the measurement of the angles of kinds are in use—the common or contact gonio-meter, and the reflecting goniometer. The first classonly of instrument is here described, as it will suf-ficiently answer every purpose of the mining mine-ralogist. The most simple form of instrument. , consists of a graduated brass semicircle, onwhich two metallic cross-blades are fixed. One ofthese cross-blades, a b, is fixed at the zero of the division ; the other, df, is movable, and denoteson the circle the angle of the crystal. In order to measure a dihedral angle, one of its faces is 5 Q. 1698 GONIOMETER. applied to the fixed cross-blade a b, in such a manner that the edge of the angle is perpendicularto the plane of the circle ; the movable cross-blade is then adjusted until its prolongation restsupon the outer face of the angle. It is evident that the angle comprised between the two cross-blades, and which is directly indicated on the circle, is the measure of the angle sought. The two cross-blades a d, df, slide in the grooves i K, g h, dn, so as to admit of the ends c a andc d being made as short as is required. This condition is indispensable, as it is often necessary tomeasure very small crystals, which can only be introduced easily between the two cross-bladeswhen their free ends can be very much shortened. This form, however, of the common goniometer has many inconveniences. The observationsare rendered difficult from the fa
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