Abstract
American journal of Science, September.—From experiments here described, Messrs. A. A. Michelson and E. W. Morlev infer the possibility of establishing a material standard a metre long, whose length in light-waves is known to within one part in one million, and perhaps one in ten millions. — Mr. H. Crew has measured spectroscopically the solar rotation for a zone some 6o° wider than any before observed, getting the equatorial value 26˙23 days, and finding no certain variation of period with latitude by this method. A comparison of the results from various methods appears to suggest a decrease of angular velocity outwards.—Stretching suddenly soft annealed wires by descent of weights through a trap door, and measuring thermo-electrically the heat evolved, Mr. C. Birus finds that as much as one-half the work done in stretching up to the limit of rupture may be stored up permanently. The work thermally dissipated varies (e.g. 75 per cent, for copper, 60 for brass, and 50 for iron); and with a given metal, there is large potentializing in the first stages of strain, and large dissipation in the final stages.—Mr. J. Trow-obridge shows reason for thinking that short waves of electrical energy are not absorbed by an approximately perfect dielectric. —A determination of the value of the B.A. unit of resistance in absolute measure by the method of Lorenz, by Messrs. Dancan, Wilkes, and Hutchinson, yields the value 0˙9863 ohms.—The Carboniferous Echinodermata of the Mississippi basin are studied by Mr. C. R. Keyes. Crinoidea greatly predominated in the first part, and Blastoidea in the later part, of the period. Abrupt differentiation and extinction of genera towards the end of the Keokuk formation, point to decided changes in the environment.—Mr. M. Carey Lea continues his interesting account of the properties of allotropic silver. No other metal seem; capable of such a variety of appearances. Inter alia, he notes the remarkable beauty of colouring in rings produced by a small crystal of iodine placed on paper that has been coated with allotropic silver in its moist and plastic state.—There are also papers on the “Grand Gulf” formation of the United States (Mr. L. C. Johnson); paragenesis of allanite and epidote as rock-forming minerals (Mr. W. H. Hobbs); a fossil spider.(Mr. C. E. Beecher), &c.
Article PDF
Rights and permissions
About this article
Cite this article
Scientific Serials. Nature 40, 562 (1889). https://doi.org/10.1038/040562a0
Issue Date:
DOI: https://doi.org/10.1038/040562a0