The specific gravity of the metallic acids (5.769) is too high for niobic acid, while no tantalic acid was detectable by Rose's method,-facts which Professor König does not understand.Beaumontite.-Several crystals of this mineral have recently been measured by Messrs. Burton and Gill,' who find no reason to suppose that it is not crystallographically identical with heulandite, as Des Cloizeaux found it to be in its optical properties.-Rutile.—The rutile crystals occurring in the spodumenebearing pockets of the gneiss in Sharp's township, Alexander County, N. C., are described by Messrs. Hidden and Washington as small, with the rare basal pinacoid prominent and well polished. Measurements of these crystals resulted in the detection of the new forms 4P, P, P, 4P, and Pg. A recalculation of the axial relations gave 1: 0.64425.-Apatite.-A small crystal of apatite implanted on muscovite, from the same locality as that mentioned for rutile, is described by the same writers as almost unique in habit, the prisms 1⁄2P, P, and 2P2 predominating. From data obtained in the measurement of this crystal, a recalculation of the axial relations for apatite gives this as I: 0.7343. A cruciform twin of apatite is described and figured, in which the twinning plane is 2P2. This is interesting as the first description of a twin of this species.—Beryl.—Two new planes have been discovered by the same authors on the emerald beryls of the Alexander County locality. These planes are P and P. On all the beryl from this locality it was observed that the prism face P is perfectly smooth, while P2 is covered with little triangular pits.—Quartz.-Some time ago Vom Rath3 noted the occurrence of the plane P on the alternate prismatic edges of certain quartz-crystals from Alexander County, N. C. Messrs. Hidden and Washington find this same form holohedrally developed in each consecutive prismatic edge.—Topaz. -A clear crystal of topaz from Zacatecas, Mexico, contains the new plane 7 Poo-Pyroxene.-Certain crystals of pyroxene from Orange County, N. Y., possess a tubular habit due to the development of the basal plane, and are remarkable besides in that they are hemimorphic in the direction of the vertical axis. The upper portions of the crystals show the forms oP, -P, P, 2P, ∞, ∞P, and P. Moreover, the lower planes are so developed that these portions of the crystals must be regarded as twinned, while the upper portions are simple individuals. Scorodite. In a late number of the American Journal of Science, Mr. Hague discusses the deposition of scorodite from the arsenical waters of the Yellowstone National Park. The mineral occurs as a green coating covering the siliceous sinter de posited by the Joseph's Coat Springs and other geysers, and is also often found in little nodules in the cavities of this sinter. An analysis of the purified scorodite yielded Mr. Whitfield, Analyses of the waters of these geysers show a small percentage of arsenious acid.-Reusch has examined the crystallized kaolin from Denver, Colorado, to which Cross and Hillebrand first called attention.2 He declares it to be triclinic and not orthorhombic as Hillebrand supposed.-A. Kenngott3 describes two peculiar crystals of gypsum from Poland, Ohio, and calls attention to a new formula for tantalite from Dakota, based upon the analysis of Schaeffer, published a few years ago. * Neues Jahrb. f. Min., etc., 1887, ii., p. 70. 2 Bull. U. S. G. S., No. 20. 3 Ib., 1887, ii., p. 84. Dec. 10, 1887. 4 Amer. Jour. Sci., 1884, xxviii., p. 430. (EXTRACTED FROM THE AMERICAN Naturalist, December, 1887.) Petrographical News.-In an exceedingly interesting paper recently published, Dr. A. Lagorio discusses some of the fundamental principles relating to the nature of the glassy base of porphyritic rocks, the succession of crystallization in rockmagmas, and the classification of rocks. He emphasizes the thought that the geologist must ask the aid of chemistry and physics in solving the problems which present themselves to him. He must obtain all the light that these kindred sciences can lend him, and in this light must approach the hidden mysteries locked up in the depths of rock-masses, and must examine them with the critical eyes not merely of the geologist, but of the chemist and physicist as well. We may then, he thinks, Edited by DR. W. S. BAYLEY, Madison, Wisconsin. 2 Miner. u. Petrog. Mitth., viii., 1887, p. 422. |