Scientific Serials

Abstract

American Journal of Science, April.—Glacial Lakes Newberry, Warren, and Dana in Central New York, by H. L. Fairchild. The ice sheet of the last glacial epoch covered all the area of the Great Lakes. When the receding front of the glacier had passed to northward of the southern boundary of the Laurentian basin, the glacial and meteoric waters were impounded between the ice front and the north-sloping land surface. These glacial lakes had their outlets southward across the divide, and they expanded northward as the barrier of ice receded. The author describes the succession of events in the life and extinction of the later and broader glacial waters in the critical district of the Finger Lakes.—Rapid method for the determination of the amount of soluble mineral matter in a soil, by T. H. Means. This method is an electrical one. The sample is treated with distilled water and the specific resistance of the solution is determined. Two men can thus examine from sixty to one hundred samples of soil in a day, and salt maps of irrigated and other districts may be rapidly constructed.—New type of telescope objective specially adapted for spectroscopic use, by C. S. Hastings. The author has constructed an objective consisting of a quadruple combination of silicate flint, borosilicate flint, silicate crown, and barium crown which is absolutely colour-free, and equally adapted to photographic and to eye observations. From the lines A to K, the focal plane for all rays is rigidly the same. There are only two free surfaces, the four lenses being cemented together.—On the phenocrysts of intrusive igneous rocks, by L. V. Pirsson. Not all phenocrysts are intratelluric in the sense that they have been formed at much greater depths than they now occur in. On the contrary, in many cases they have been formed in place, and are of contemporaneous origin with the other constituents of the rocks.—The occurrence, origin, and chemical composition of chromite, by J. H. Pratt. The author has been led to adopt the theory that the chromite occurring in the peridotite rocks of North Carolina was formed at the same time as the peridotite, i.e. was held in solution by the molten mass of the peridotite and crystallised out among the first minerals as the mass began to cool.—Two species of Saurocephalus, by O. P. Hay. One of the species described, S. lanciformis, is little known. The other species is new. It has a slenderer head and a larger mouth than S. dentatus. The author names it S. pamphagus.