report on the minera' products of Canada.- -In the tourmaline of the tourmaline granite of Striegau, Traube 25 has discovered pleochroic halos around inclusions of rutile and zircon. The color of the halos is some shade of violet, and is independent of the color of the mineral in which they lie. It disappeares upon heating. Garnet, apatite, and quartz inclusions in the same tourmaline are not surrounded by halos.——— Among the new instruments, and improvements upon old instruments, used in crystallographic and mineralogical investigations, that have been suggested during the last three months, mention may be made of an apparatus 26 for the production of pressure figures in very small mica plates; of a very simple reflection goniometer constructed by Prof. Groth 27; of an improved instrument 28 for cutting thin sections of minerals in any desired position; and an improved heating apparatus for use with the reflection goniometer, invented and constructed by the well-known mechanician Fuess.29

25 Neues Jahrb. f. Min., etc., 1890, I., p. 186.

26 Steenstrup: Geol. Fören. Förh., Stock., 1888, p. 113. Ref. Zeits. f. Kryst., XVII.,

P. 429.

27 Zeits. f. Kryst., XVII., 1890, p. 396.

28 Ib. XVII., 1890, p. 445.

29 Neues Jahrb. f. Min., etc., 1890, I., p. 161.

Published August 28th, 1890.

From the AMERICAN NATURALIST, September, 1890.

MINERALOGY AND PETROGRAPHY.'

Petrographical News.-The results of the investigation of the clastic, metamorphic, and eruptive rocks of the Coast Ranges of California, promised by Mr. Becker a few years ago, have recently3 appeared in an extended form. The principal conclusions of the study have already been referred to in these notes. The proofs which Mr. Becker offers for the correctness of the statements that many serpentines of the Coast Ranges are altered sediments will probably be accepted by most petrographers as sufficient. His conclusion that typical diabases, diorites, and gabbros are likewise derived from clastic materials will not find such ready acceptance, as there seems to be no positive evidence that such rocks were originally sediments, rather than eruptives, which squeezed themselves into fragmental beds, and so caused the formation of a graded series, with sandstone at one end and a holocrystalline rock at the other end. There is no reason to suppose that holocrystalline rocks may not have sometimes originated by metasomatic alteration of fragmentals; but the belief that a rock with the peculiar structure of diabase has originated in this way will require stronger proof for its acceptance than that offered in Mr. Becker's monograph. The presentation of a few illustrations of types. of rocks intermediate between the sandstones and the diabases (pseudodiabases of Becker, metadiabases of Dana) would have aided materially in enabling readers of the volume to draw their own conclusions as to the origin of the rocks in question. In the discussion of the massive rocks of the region, the term asperite is proposed as a general one to include all andesitic rocks with a rough trachytic habit. In this

1 Edited by Dr. W. S. Bayley, Colby University, Waterville, Me.

2 AMERICAN NATURALIST, Aug. 1886, p. 724.

3 Monographs of the U. S. Geol. Survey, Vol. XIII., pp. 56-175.

Cf. Van Hise. AMER. NATURALIST, 1886, p. 723.

portion of the volume are also described andesitic and basaltic glasses, which are inuch more acid than the holocrystalline rocks with which they are associated. The basalt glass has the composition of an obsidian, and passes into a rock with the appearance of basalt. Analyses I. and II. are of obsidian and basalt respectively:

The difference in structure of the two rocks is supposed to be due to differences in composition of the original magma.—As an introduction to his description of the minerals of the syenite-pegmatite veins of Southern Norway, Brögger gives a short account of the geology of the region in which these veins occur, and gives his reasons for regarding the lattter as eruptive in origin, as against the lateral secretion theory proposed to account for them. Since the article is itself an abstract of a monograph on the geology of the region, it is difficult to give a résumé of its contents. Among the rocks discussed are some new types, to which reference may be made. Laurvikite is a typical augite-syenite composed of anorthoclase (or cryptoperthite) diopside, ægerine, and lepidomelane, with small amounts of barkevikite, olivine, sphene, magnetite, apatite, zircon, nepheline, cancrinite, and sodalite. It is granitic in structure, except on its periphery, where it is developed as the well-known rhombic porphyry. This latter occurs also as dykes in the former and as flows. A variety of the laurvikite, in which oligoclase is present in addition to the anorthoclase, and in which the latter mineral has rectangular rather than the rhombic cross sections which characterize it in the laurvikite Brögger calls augite-mica-syenite, since it contains very little nepheline. Another rock very characteristic of the region is called laurdalite. This is a coarse-grained nepheline-syenite, with or without olivine. It contains. more nepheline and sodalite than does laurvikite, and the former mineral is porphyritically developed. It is the rock described by the author as nepheline-syenite in a former publication. The dyke rock corresponding to laurdalite is a nepheline-rhombic-porphyry, which differs from the porphyritic laurvikite in containing nepheline in its 5 Zeits. f. Kryst., etc., XVI., 1890.

'Silur. Elagen, 2 and 3, p. 273.