Societies and Academies

    Abstract

    LONDON. Mineralogical Society, January 29.—Prof. H. A. Miers, F.R.S., president, in the chair.—Experiments bearing on the order of crystallisation of rock-constituents: Prof. H. A. Miers. The general results of experiments made by Miss F. Isaac and Prof. Miers with mixtures of salol and betol in all proportions were described; the experiments have established the supersolubility curves even beyopd the points where they cross below the eutectic temperature. Owing to the fact that the main separation of crystals in the cooling mixtures takes place only when the liquids have been supercooled to temperatures given by the supersolubility curves, it has been found (i) that in general the mixtures do not solidify as a eutectic mixture; (2) that, according to the conditions of supercooling, either substance could' be made to crystallise before the other in mixtures approaching the eutectic in composition. It was suggested that these results are applicable to the solidification of many rocks and alloys.—Serpentine rock from the Tarnthaler Köpfe, Tyrol: Dr. A. P. Young. The minerals found in the serpentine are diopside, tremolite, clinochiore, picotite, magnetite, iron pyrites, and a fibrous mineral referred to antigorite. The latter mineral is regarded as holding a place between the micas and chiorites. On the surface of the serpentine are projecting bastite pseudomorphs coated with films of silvery lustre. The serpentine is a non-foliated intrusive core which on the borders is highly foliated and passes into talc-bearing phyllites.—A simple tabular arrangement of the thirty-two crystallographic classes: Dr. J. W. Evans. The table is based on the character of the symmetry of the principal zone axis or zone axes. Each column contains classes with the same rotational symmetry round the axis, and each row thoe which agree in the other symmetrical characters of the axis.—A new model of crystal refractometer: Dr. G. F. 1-lerbert Smith. This instrument is identical in principle with that previously described, and is intended for use with large mineral specimens and mounted gem-stones. No part extends above the level of the plate holding the dense glass hemisphere. Further, the optical combination has double the focal length of the earlier form, and provides, consequently, greater refinement.—Isomorphism as illustrated by certain varieties of magnetite: Prof. B. J. Harrington. Analyses are given of specimens of magnetite from St. Joseph du Lac, Canada, and from Magnet Cove, Arkansas, both showing the unusual combination of octahedron and trapezohedron {311}. The Canadian specimen contained about 5 per cent. of TiO2, 8 per cent. of MnO, and 3 per cent. of MgO, and the specimen from Arkansas about 10 per cent. of Al2O3, 2 per cent. of TiO2, 2 per cent. of MnO, and 9 per cent. of MgO.—Mr. Fleischmann exhibited a collection of olites from Japan, Dr. Evans an objective giving a flat field with convergent light, and Prof. Miers a goniometer to be used for the measurement of the refractive indices of cooling solutions, for which purpose it is provided with means for maintaining a constant temperature for any desired period.

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    Societies and Academies . Nature 75, 405–408 (1907). https://doi.org/10.1038/075405a0

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