Abstract
THE latest issue of the Memoirs (Trudy) of the Society of Naturalists at the St. Petersburg University, Section of Geology and Mineralogy (vol. xxvii., fasc. 5, 1899), will be found most interesting for mineralogists and petrologists—the more so as each paper, in Russian, is followed by a full, detailed summing up in German. The volume is edited by K. von Vogdt, and contains three important papers. The first, by M. Boris Popoff, is upon the elipsoidal inclusions contained in that most interesting granite, the Rappa-kivi (“rotten stone”) of East Finland. It is an excellent, very well-written analysis of the different porphyr-like inclusions which are found in the granite—some of them surrounded by an oligoclase-envelopment and with defined outlines, while the others are devoid of that envelope, and in this case have an undefined or a wave-like surface. To explain the appearance of the different sorts of inclusions being mixed together in this granite, the author resorts to the hypothesis of a slow motion of the crystallised ovoids, formed in different parts of the mass, but consequently moving about within it during the cooling of the mass. The second paper is a note on a variolite found on the left bank of the Lower Yenisei. The third paper is a detailed work (353 pp. in Russian, and 37 pp. of German résumé), by B. Polenov, on the massive rocks of the northern parts of the Vitim plateau of East Siberia. The author has most carefully worked out the beautiful collection of samples of rocks which was brought in, in 1865, by the mining engineer, I. A. Lopatin. A most elaborate descriptive catalogue of this collection has already been published a couple of years ago by B. Polenov. Now he gives a summary of the geological conclusions which may be drawn out of this collection. He begins his work by a most valuable sketch of the geological structure of the plateau, based on Lopatin's, Kropotkin's and Tchersky's explorations; this sketch (28 pp.), unfortunately, is not summed up at all in German. The remainder of B. Polenov's work (325 pp.) is given to a careful discussion of the various rocks entering into the composition of the plateau—namely, the oldest granites with their subordinate syenites and gabbro-norites; the younger group of plagioclase rocks—syenites, diorites, and diabase rocks; and the youngest group of basalts which cover the plateau on immense stretches; and, finally, the metamorphism phenomena which have been going on in all these rocks. A number of plates accompany the papers.
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Scientific Serial . Nature 61, 285 (1900). https://doi.org/10.1038/061285a0
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DOI: https://doi.org/10.1038/061285a0