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Nature volume 13, pages 497498 | Download Citation

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American Journal of Science and Arts, March.—In this number Mr. Trouvelot directs attention to the phenomenon of what he calls “veiled solar spots.” During last year, the chromosphere has been notably thinner than usual, and the granulations smaller and less numerous, rendering more conspicuous the light-grey coloured back-ground between the granules. The veiled spots are seen through the chromosphere that is spread over them like a veil; they are, like ordinary spots, true openings of the photosphere; they are scattered throughout all latitudes, though more complicated in regions where the ordinary spots make their appearance. Mr. Trouvelot has observed spots at least within 10 degrees of the north pole of the sun (very few of the ordinary spots have hitherto been observed beyond 40).—Prof. Kirnball describes an ingenious arrangement by which lie demonstrates that the law affirming the coefficient of friction on an inclined plane to be constant for all velocities, is not strictly true. The sliding box had a cover 6 feet long, with strips cf smoked glass upon it, on which a tuning fork, fixed above to an independent support, traced a wave-line as the box slid down, thus giving a perfect autographic register of the experiment.—A new method of measuring the velocity of electricity is described by Prof. Lovering. He avails himself of Lissajous' method of compounding the rectangular vibrations of two tuning forks, the reflected beam entering a telescope. The forks being maintained in vibration by electro-magnets and brought into unison, the resultant orbit seen in the telescope is invariable. A length of resistance coil is introduced sufficient to change the orbit to some other in the series, and this change reveals the amount of retardation of the one fork's vibrations, due to the inserted resistance.—Prof. Mallet discusses the constitutional formula of urea, uric acid, and their derivatives.—A new trilobite, Dalmanitis dentata is described by Dr. Barrett, and Prof. Marsh gives (in an appendix) the principal characters of Tillodontia, a new order of extinct mammals found in the Eocene deposits of North America.—Mr. Wallace gives an account of some flint implements found in the stratified drift in the vicinity of Richmond, Virginia, and there are one or two notes on points in American geology.

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https://doi.org/10.1038/013497a0

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