Abstract
Sillimait's Journal, September 1870.—The opening article of this number is by Prof. E. Loomis, and is entitled “Comparison of the mean daily range of the Magnetic Declination, with the number of Auroras observed each year, and the extent of the black spots on the surface of the Sun.” The author first discusses the observations of sun-spots, and points out some corrections that should be made in the numbers obtained by astronomers in the last century; he points out that the period is one of ten years, and is influenced by the heliocentric conjunctions of Jupiter and Saturn, but affected by the conjunctions of the Earth and Venus. By a series of tables and curves the coincidences of periods of the maximum number of sun-spots with the maxima of magnetic disturbance and auroral display are elucidated, from which it appears that the present year is a period of maximum.—In a letter to the editors, Mr. J. W. FYench proposes a new period in chronology called the Precession Period, of 25,782 years, being the time for the precession of the equinoxes. The author prefers this period, since it is founded solely on astronomical facts.—The third article is by F. W. Clarke, “On the atomic volumes of solid compounds,” in which are discussed the relations of the volumes of analogous and similarly constituted bodies.—The next article, “Considerations on the apparent inequalities of long periods in the mean morion of the Moon,” is by Simon Newcomb, and, after a long discussion on the observations on this subject, and the theories proposed to explain them, the author attributes the phenomenon to an irregularity in the rotation of the crust of the earth, caused by the motion of its fluid contents.—The following is a very interesting article by Dr. A. M. Mayer on “Researches in Electro-magnetism. “The author has devised a very accurate method of determining the relative values of electro-magnets to replace the one usually employed, which consists of measuring the deflection of a magnetic needle which is produced by the action of the electro-magnet. The author found that this process was liable to error in consequence of the difficulty of keeping the current absolutely constant, resulting in a continual motion of the needle. These difficulties were obviated in the following manner: A line eight feet long and divided into fractions of inches was drawn on a table, the latter being so placed that the line was at right angles to the magnetic meridian; a compass, with a needle nearly six inches long, was placed on this line, and a helix was fixed at each extremity of the line. These helices were traversed by the same current, a tangent galvanometer being placed in the circuit. In this way the needle was influenced by two magnets acting in opposite directions and excited by the same current, and if any deflection of the needle was observed, it must have been due to a difference of power of the magnets. If this occurred the needle might be brought to 0° by moving it from the stronger magnet. A series of experiments was made to determine the variation of the intensity of the force with a change of distance, by placing the needle opposite an electromagnet and noting the deflection produced when the instruments were at different distances from one another: it was found that in the apparatus employed the intensity varied inversely as the 27404 power of the distance from the core. Dr. Mayer has determined the power of cores made of insulated and of non-insulated soft iron wires, and finds that the insulated core is slightly.the weaker. He has also measured what thickness of tube is equal to a solid core of the same diameter, and has found that a solid cylinder ten inches long and 1168 in diameter may be replaced by a tube of the same length and of a thickness of the diameter. This relative size does not appear to be constant for cores of all dimensions. A longitudinal slit in the tube does not diminish its power; in fact, Dr. Mayer seems inclined to think that it facilitates its magnetisation. By placing a helix inside a soft iron tube a magnet is produced with poles the reverse of those of the coil, or of a bar placed within the helix; this supports Ampere's theory of magnetic currents. Numerous other experiments are detailed in this paper, and the author promises to employ his apparatus for the determination of the force of magnets of different sizes.—Mr. G. F. Barker contributes an abstract of the second series of Professor Meissner's researches on electrised oxygen, in which are detailed the author's experiments on the substance formed simultaneously with ozone which possesses the property of producing a white mist in contact with water. The original paper was published by the Gottingen Royal Society of Sciences.—Mr. A. E. Verrill describes a new species of Entozoon from the Hog. This is followed by some notes on the structure of the Crinoidea, Cystidea, and Blastoidea, by E. Billings, F.G.S.—The next article consists of contributions to chemistry from the laboratory of the Lawrence Scientific School, the first paper of which is by W. G. Leison, on the precipitation and determination of the metals of the magnesium group in the form of oxalates. For this purpose the solutions containing the metals are mixed with oxalic acid and alcohol, the precipitated oxalates washed, dried, and dissolved in hydrochloric or sulphuric acid, and the quantity of oxalic acid present estimated by means of a standard solution of potassic permanganate. A number of examples show the accuracy of the process.—J. H. Talbott describes the precipitation of zinc and manganese as sulphides, and the quantitative separation of tin and tungsten by fusing with potassic cyanide, by which the tin is reduced to the metallic state.—A new mode of treating gelatinous precipitates is suggested by M. Chatard, which consists in evaporating the liquid containing the precipitate to dryness, and stirring until the mass becomes a dry powder, which is then readily washed on a filter.—S. P. Sharpies points out that antimonious sulphide precipitated by sulphuretted hydrogen in boiling solutions is granular and easily washed. Arsenious sulphide does not behave in a similar mannsr.—In the fifth section B. Godwin advises the repetition of quantitative analyses with the same quantity of material, the mean of the results being taken.—The next article is by Professor W. A. Morton on the corona seen in total eclipses. He calls the attention of astronomers to the importance of determining the positions of the more prominent portions of the corona with reference to the equator of the sun.—Dr. Finlay contributes observations on prehistoric archaeology in Greece.—The remainder of the journal consists of extracts from other journals principally European.
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Scientific Serials . Nature 3, 156–157 (1870). https://doi.org/10.1038/003156a0
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DOI: https://doi.org/10.1038/003156a0