Abstract
American Journal of Science, August.—On hitherto unrecognised wave-lengths, by S. P. Langley. The object of the laborious and delicate operations here fully described has been, not so much to settle the theoretical questions involved in determining the relation between dispersion and wave-length, as to enable future observers to determine the visible or invisible wave-lengths of any heat, whether from a celestial or terrestrial source, observed in any prism. A knowledge will thus be gained of the intimate constitution of radiant bodies, which an acquaintance with the vibratory period of their molecules can usually alone afford. These researches into the whole unexplored region of infra-red energy both from celestial and terrestrial sources have led to the certain determination of wavelengths greater than 0.005 mm. Radiations have also been recognised whose wave-length exceeds 0.03 mm., so that, while the wave-length known to Newton has been directly measured to nearly eight times, there is probable indication of wave-lengths far greater. The gulf between the shortest vibration of sound and the longest known vibration of the ether has thus in some measure been already bridged over.—On the chemical composition of herderite and beryl, with note on the precipitation of aluminium and separation of beryllium and aluminium, by S. L. Penfield and D. N. Harper. The composition of herderite is shown to be an isomorphous mixture of CaBeFPO4 with CaBe(OH)PO4, which may be written CaBe(FOH)PO4, or a salt of phosphoric acid, two of whose hydrogen atoms have been replaced by a bivalent element, and the third also by a bivalent element whose other free affinity has been satisfied by a fluorine atom or hydroxyl. Chemically it is closely related to wagnerite, triplite, and triploidite, these minerals offering the best illustration of the isomorphism of F and OH. In crystallisation, herderite is orthorhombic, with a prismatic angle of nearly 120°. Regarding water as an essential constituent of beryl, the authors add 1/2 2O to its usually accepted formula, writing it H3Be6Al4Si12O37. Its theoretical composition, according to this formula, becomes SiO2 65.81; Al2O3 18.83; BeO 13.71; H2O 1.65. Specific gravity, 2.706.—Communications from the U.S. Geological Survey, Division of the Rocky Mountains, by Whitman Cross and L. G. Eakins. The present paper deals with ptilolite, a new mineral occurring in cavities of a more or less vesicular augite-andesite, which is found in fragments in the Tertiary conglomerate beds of Green and Table Mountains, Jefferson County, Colorado. It is described as a white substance in extremely delicate tufts and spongy masses composed of short hair-like needles loosely grouped together; hence its proposed name of ptilolite, from the Greek πτίλ o ν = down, in reference to the light downy nature of its aggregates. Its empirical formula is RO, Al2O3, 10SiO2 + 5H2O, R representing Ca, K2, and Na2; it is thus an alumino silicate of which no previously described hydrate contains so high a percentage of silica. In this respect it may compare with the rare mineral milarite.—Notes on the peridotite of Elliot County, Kentucky, by J. S. Diller. This formation, described as a dark greenish rock with specific gravity 2.781, appears to be undoubtedly of eruptive origin, traversing many thousand feet of palæozoic strata to reach the surface. Its mineralogical composition shows 40 per cent, of olivine, 30.7 serpentine, 14 dolomite, 8 pyrope, 2.2 ilmenite, 2 magnetite, with smaller quantities of biotite, enstatite, octa-hedrite, and apatite.—Temperature observations at the Lake Superior Copper-Mines, by H. A. Wheeler. The unusually low thermal gradients recorded in these mines—about 1° F. to 100 feet as compared with the normal of 1° F. to 50 or “55 feet in vertical descent, is attributed to the proximity of the cold waters of Lake Superior. The nearer the mines are to this great cooling influence, the lower the thermal gradient will be found to be.—An application of the copper reduction test to the quantitative determination of arsenic, by Henry Carmichael. Using a standard square of copper as an indicator, the author has been led to adopt the method here described, which, for the estimation of small quantities of arsenic in the human system or elsewhere, he believes to be quicker, simpler, more delicate, and, in the hands of toxicologists, less exposed to fallacy, than any other. A copper square I millimetre on a side detects.00000025 grmarsenious oxide, a quantity 400 times less than that necessary for turning the beam of the ordinary chemical balance.—On the crystallisation of gold, by Edward S. Dana. The paper deals more especially with the delicate crystalline threads and arborescent forms from the White Bull Mine, Oregon, and the specimens of finely crystallised gold from the Californian mines. The crystals are illustrated and fully described.—Classification of the Cambrian system of North America, by Charles D. Walcott. The formations here treated are those characterised by the predominance of the types of Barrande's “First Fauna,” and such additional strata, not characterised by the presence of fossils, as are stratigraphically and structurally connected with the Cambrian strata identified by organic remains. These formations, showing a total thickness of over 18,000 feet, with a known fauna of 92 genera and 393 species, are regarded, not as a subdivision of the Silurian, but rather as a well-defined geological system underlying the Lower Silurian (Ordovician) on the North American continent.—Note on the spectrum of Comet c, 1886, by O. T. Sherman. When observed with the equatorial of Yale Observatory in May and June, this comet presented no less than seven loci of light where three only are usually seen. These showed approximate wavelengths 618.4, 600.6, 567.6, 553.7, 517.1, 468.3, and 433.2, besides strongly suspected loci at 545.4, 535.0, 412.9, and 378.6. These are compared with the low temperature spectrum of carbohydrogen, and it is suggested that a chart should be prepared for the carbon compounds at successive heat-levels, after the manner of that drawn up by Lockyer for the photographed spectra of some carbon compounds (Prof. Roy. Soc., xxx. p. 463).
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Scientific Serials . Nature 34, 402–403 (1886). https://doi.org/10.1038/034402a0
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DOI: https://doi.org/10.1038/034402a0