(EXTRACTED FROM THE AMERIcan NaturalisT, JUNE, 1887.) MINERALOGY AND PETROGRAPHY.' Petrographical News.-The second paper devoted to the study of the massive rocks belonging to the "Cortland series" on the Hudson River, near Peekskill, has recently appeared in the American Journal of Science.3 In this paper the author, Dr. G. H. Williams, describes the norites and related rocks, which make up by far the greater part of the entire Cortlandt series. These norites are divided into norites proper, hornblende norites, mica norites, hyperites or augite norites, and pyroxenites. The norite proper is very rare, almost all sections showing the presence in small quantity of minerals which would, in accordance with a strict classification, require the rock to be placed in one of the other four groups. The most interesting facts brought out in the examination of these rocks are (1) the occurrence of orthoclase in several specimens, and (2) the existence of numerous inclusions in this orthoclase and in the more prevalent andesine. The orthoclase is in porphyritic crystals, in which are sometimes imbedded smaller crystals of plagioclase. Under the microscope the former is seen to possess a "shagreen" surface, due to numerous oval indentations. All the feldspar of the norites is filled with little inclusions of plates, rods, and dots. These seem not to be arranged in any definite position with regard to crystallographic Edited by Dr. W. S. BAYLEY, Madison, Wisconsin. 2 Cf. American Naturalist, March, 1886, p. 275. 3 Amer. Jour. Seience, xxxiii., February, p. 135; March, p. 191. planes, as demanded by Judd's shillerization theory, but are grouped in zones. They are regarded by Dr. Williams as original and representing the forms in which the iron first separated from the magma, this separation occurring contemporaneously with the crystallization of the feldspar. Many of the mica norites possess a well-marked schistose structure, a fact which led Professor Dana' to ascribe to them a metamorphic origin from sedimentary deposits. A study of their thin sections, however, shows this schistosity to be but another instance of the secondary development of this structure by pressure. The iron ore and emery deposits of this region were also examined. This ore is composed essentially of octahedral crystals of magnetite imbedded in a dark green mineral with the composition and optical characteristics of hercynite (or pleonaste, with a very low percentage of magnesium). This mineral is also found disseminated in small octahedral crystals in the rock adjoining the ore veins. Associated with the magnetite and hercynite of the ore occur also fibrolite and corundum. The same author, in a communication in Science, declares, as the result of microscopical examination, that the serpentine occurring at Syracuse, N. Y., must be regarded merely as an altered peridotite. The remains of bronzite crystals can still be detected in the rock, and consequently the view of Professor Sterry Hunt, that it must be looked upon as an altered sediment because of its intimate association with sedimentary beds of gypsum, can no longer be maintained. In a preliminary "Note on the Volcanic and Associated Rocks of the Neighborhood of Nuneaton," England, T. H. Waller 3 mentions the occurrence there of ashes (tufa) composed of pieces of feldspar, a little quartz, and grains of some basic rock; a felsite with porphyritic crystals of quartz, in which lines of secondary fluid inclusions are well exhibited; a diabase porphyrite with augite twinned according to both twinning laws,-viz., parallel to op and ∞P; and, finally, indurated quartzites with the individual quartz grains enlarged by the addition of new quartz material whose optical orientation is identical with that of the original grains. In connection with the statement of Dr. Williams in regard to the serpentine of Syracuse, it may be of interest to call attention to an article in which J. H. Collins cites several examples to prove that "some beds of a common series have been changed into serpentine, while others (pass over) into hornblende schist." He thinks that many of the serpentines of Cornwall, which have heretofore been regarded as having originated by the alteration of intrusive sheets of picrite, may as well be considered as having originated in some other manner. Meteorites.-Very recently the name giovanite has been proposed by Meunier1 for a brecciated meteoric stone which fell at San Giovanni d'Asso, near Siène, in Italy, in 1794. Specimens of this same fall have been described previously, but the individual pieces were so small that the interesting facts which Meunier has discovered upon the examination of a larger specimen were overlooked. Meunier finds that this giovanite is made up of fragments of the rock limerickite cemented together by a substance with all the characteristics of leucite,-i.e., the relations of these two substances are inversely what they are in mesminite, in which fragments of leucite are imbedded in limerickite. After briefly discussing the subject of the origin of this structure, Meunier concludes that there must be a community of origin for various meteoric rocks, and that in this common place of origin geological action (as we understand it) must exist. He further states that the analogy which it is sought to establish between meteors and comets (and shooting-stars) cannot be maintained.—Two meteors of considerable ethnological interest are described by Mr. G. F. Kunz3 in the American Journal of Science for March. The first is a meteoric stone composed of rounded and angular pieces of olivine in a ground-mass consisting of iron. Analyses of the two constituents yielded Mr. Mackintosh the following figures: Olivine: SiO,=37.90; MgO=41.65; FeO=19.66; MnO,CoO=0.42. The author regards this meteor, which was found in Carroll County, Kentucky, as part of the same mass from which the iron was obtained for making the iron ornaments found in the Turner and the Liberty groups of mounds in the Little Miami Valley, Ohio. The second mass was found near Catorze, San Luis Potosi, Mexico, in 1885. It weighs ninety-two pounds. Its composition (analysis by Mackintosh) is: Fe=90.09; Ni,Co= 9.07; P=0.24; schreibersite=0.60. It resembles in character the irons of Augusta County, Va., of Glorieta Mountain, and others of the class caillite (Meunier). In a cylindrical cavity in this meteor can still be seen the broken end of a copper chisel. -The ninth meteoric iron which has actually been seen to fall has recently come into the possession of Mr. W. E. Hidden.5 The mass weighed before polishing three thousand nine hundred and fifty grammes. It was seen to fall on the evening of the 27th of November, 1885, during the periodic star shower of the "Bielids." The location of the fall is near Mazapil, in the state of Zacatecas, Mexico. According to the belief of Professor I Comptes Rendus, civ., Jan. 1887, p. 193. 2 Cf. American Naturalist, Jan. 1887, p. 73; and Dec. 1885, p. 1213. 3 Amer. Jour. Sci., xxxiii. p. 228. 4 Cf. American Naturalist, Jan. 1887, p. 73. 5 Amer. Jour. Sci., xxxiii., 1887, p. 221. José A. y Bouilla, Director of the Astronomical Observatory at Zacatecas, this meteor represents part of the comet Biela-Gambert, lost since 1852. It is characterized by the freshness of its surface, which shows very perfectly the flow of the melted crust, and by the presence of unusually large nodules of a very compact graphite. For some time after its fall it remained red-hot. Its analysis yielded Mr. Mackintosh 91.26 per cent. of iron, 7.845 per cent. of nickel, 0.653 per cent. of cobalt, and 0.30 per cent. of phosphorus. Carbon is distributed all through the mass between the crystalline plates. Mr. Huntington' calls attention to the fact that the Maverick County, Texas, meteorite possesses many of the characteristics of the Coahuila irons, described by the late J. L. Smith, and from the similarity of the two concludes that the former must be classed as one of the latter, and should not be regarded as an independent fall.In connection with meteorites it may be of interest to note the discovery by Meunier3 of little globules of a stony matter in the ashes of Krakatau. Upon examination they are found to be made up of little crystals of augite and plagioclase in a vitreous ground-mass. The author calls attention to the similarity between these bodies and the chondra of certain meteorites. Recent Publications. It is unfortunate.that a treatise written expressly for the use of students should contain so many inaccuracies as are noted in the recent "Elements of Geology" by Professor A. Winchell. Whatever may be said of the rest of the book, that portion which treats of petrography and the optical properties of minerals will not serve to give the beginner any definite idea of the fundamental principles upon which all rock classification is now based. Many of the statements made are, to say the least, misleading, and the definitions of the various rock types are unsatisfactory. An excellent text-book of Mineralogy, by Max Bauer,5 appeared about a year ago. It is by far the best book for general use in the class-room that has yet been published. The chapters on the development of the principles of crystallography are to be recommended as especially well adapted to the use of those beginning the study of the subject. Ferdinand Henrich's" text-book of Mathematical Crystallography will fill a long-felt want of those who desire to gain some knowledge of the methods in use for the measurement and calculation of crystal forms, crystallographic constants, twinning planes, etc. The work is well written, and the directions given in it are all clearly and concisely expressed. Wherever it can aid the explanation of a difficult point examples 4 Geological Studies, or Elements of Geology. Chicago: Griggs, 1886. 5 Lehrbuch der Mineralogie. Berlin und Leipzig, 1886. J. Guttentag (D. Collin). ❝ Lehrbuch der Krystallberechnung. Stuttgart, 1886. Euke. are introduced and calculations are made in full, just as in ordinary practice. Miller's system of indices is used throughout, and the rules for making spherical projections are developed at some length. This is the only elementary text-book in which the subject of spherical projection is given the attention it naturally merits as being the method which is now almost universally used by the most eminent crystallographers. Among the publications of the last few months which contain more or less of interest in mineralogy and petrography may be mentioned Professor A. Kenngott, M.D.-Handwörterbuch der Mineralogie, Geologie und Palaeontologie, III. Breslau, 1887. Eduard Trewendt. Dr. C. Rieman.-Taschenbuch für Mineralogen. Berlin, 1887. Julius Springer. F. Toula.-Mineralogische und petrographische Tabellen. Leipzig. Freytag. J.D. Dana.-Manual of Mineralogy and Petrography.' 4th ed., 1887. New York: John Wiley & Sons. Professor W. O. Crosby.-Tables for the Determination of Common Minerals, chiefly by the Physical Properties, with confirmatory Chemical Tests. Boston, 1887. A. Crosby. Professor A. H. Chester.—Catalogue of Minerals Alphabetically Arranged, with their Chemical Composition and Synonyms.2 New York, 1886. John Wiley & Sons. T. Sterry Hunt.-Mineral Physiology and Physiography." Boston, 1886. S. E. Cassino. Professor W. O. Crosby.-Geological Collections. Mineralogy. Boston Soc. Nat. History, 1886. A. C. Lawson.-Report on the Geology of the Lake of the Woods Region. Part CC. Annual Report of the Geological and Natural History Survey of Canada. Montreal, 1885. C. D. Lawton.-Mineral Resources of Michigan for 1885. By authority. Lansing, 1886. Thorp & Godfrey. Mineral Resources of the United States for 1885. Washington, 1886. Government Printing Office. Dr. P. Groth.-Grundriss der Edelsteinkunde. Leipzig, 1887. Engelmann. June 29, 1887. Reviewed in Science, 1887, p. 304. 2 Reviewed in Science, February, 1887, p. 142. |