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American Journal of Science, June.—Othniel Charles Marsh—portrait and obituary notice.—The Camden Chert of Tennessee and its Lower Oriskany Fauna, by J. M. Safford and C. Schuchert. The latter describes in detail a peculiar chert formation discovered by the former.—Recent discovery of rocks of the age 01 the Trenton formation at Akpabok Island, Ungava, by J. F. Whiteaves. Describes the fossils collected by Dr. R. Bell, of the Canadian Geological Survey, on Akpabok Island, between Ashe Inlet and Fort Chimo, and concludes that they belong to a lower geological horizon than the Hudson River formation as at first supposed.—Studies in the Cyperaceæ, No. 10, by T. Holm. Describes the North American species of Fimbristylis, Vahl.—On Roscœlite, by W. F. Hillebrand and H. W. Turner. Roscoelite is a vanadium mica, some specimens of which show a tendency to crystallise in little rosettes. It occurs most frequently embedded in quartz at Placerville, California. It contains 45 per cent. SiO2, 24 per cent. V2O3, 11 per cent, alumina, 10 per cent, potash, 4 per cent, water, and traces of magnesia and ferrous oxide.—Gravitation in gaseous nebulæ, by F. E. Nipher. If R be the radius of a spherical mass of gas of cosmical dimensions, and T its temperature, the product TR is constant. The heat capacity of such a gravitating mass is negative. If heat leaves the gas, it contracts and becomes warmer. The physical condition to be satisfied in order that a central mass or core, having a radius equal to that of the sun, should contain a mass equal to that of the sun, is that its temperature is 20 million degrees Centigrade. The pressure at the surface of this sphere is 366 million atmospheres. The average density of the spherical mass, which is three times the density at the surface of the hydrogen sun, is about 7 per cent, less than the average density of the sun itself, but the nature of the gas is immaterial. In the sun as it is, the rarefied external parts of the solar nebula have parted with their heat, and the temperature throughout the mass has ceased to be uniform. But the abolition of cosmical pressure has almost wholly compensated the fall in temperature of the sun from 20 millions at least to perhaps 10,000 degrees.
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Scientific Serials. Nature 60, 212 (1899). https://doi.org/10.1038/060212a0
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DOI: https://doi.org/10.1038/060212a0