Societies and Academies

    Abstract

    LONDON. Royal Society, January 22.—H. C. H. Carpenter and Miss C. F. Elam: Experiments on the distortion of single-crystal test-pieces of aluminium. Single crystal test-pieces of aluminium can be extended up to 7-per cent, without recrystallising on heating to 600° C. They will recrystallise to form either another single crystal of a different orientation or several crystals, according to the degree of strain. When a large crystal grows from a number of small ones, it has no particular orientation or relation to the direction of mechanical strain. Unless the metal recrystallises, the distortion of the crystal is not removed by heating, and unless the metal recrystallises, the heating does not remove the whole of the hardness acquired through mechanical strain. Hardening by mechanical deformation can take place independently of change of orientation. The proportional increase in hardening is greatest during the early stages of extension, but in the case of single crystals a stage is reached when the increase in hardness is approximately proportional to the amount of plastic deformation.-W. S. Farren and G. I. Taylor: The heat developed during plastic extension of metals. Hollow bars of certain metals were subjected to plastic stretching. The work done on a measured length in the middle of the specimen was measured, and at the same time the rise in temperature at the centre of the bar was recorded. The heat generated varied from 86-5 per cent, of the heat equivalent of the work done, in the case of annealed steel, to 95 per cent, in the case of single-crystal specimens of aluminium. This ratio remained constant for one material during the whole range of the extension, which in the case of aluminium amounted to more than 50 per cent, of the initial length. - J. V. Howard and S. L. Smith: Recent developments in tensile testing.-R. L. Smith-Rose and R. H. Barfield: On the determination of the directions of the forces in wireless waves at the earth's surface. The propagation of wireless waves over the earth's surface implies the reception of two or more distinct waves at an appreciable distance from the transmitting station. One of these is assumed to arrive at the earth's surface after reflection or refraction from the upper portions of the atmosphere, and an attempt is made to detect it by measuring the inclination of the wave-front of the arriving wave. Such a down-coming wave would give rise to a reflected wave which, at the earth's surface, will interfere with the incident wave in such a way as to tend to eliminate the horizontal component of the electric force and the vertical component of the magnetic force. The conductivity of the earth at wireless frequencies was determined experimentally by measuring the "for-word tilt "of the waves arriving from neighbouring transmitters for a number of sites in South England. A moderately consistent value of about io8 (e.s.u.) was obtained, and calculations from this value show that the directions of the resultant forces at the surface will always be sensibly the same as those of a horizontally propagated wave.-D'Arcy Thompson: On the thirteen semi-regular solids of Archimedes, and on their development by the transformation of certain plane configurations. The thirteen isogonal non - isohedral solids attributed to Archimedes stand in close relation to the ten regular plane repeating patterns or "nets "first described by Kepler, which consist of regular and identical sets of congruent polygons. If, in the table of indices giving the number of triangles, squares, etc., found at each junction (or node), the order of an index be successively reduced, we pass accordingly from the plane polygonal assemblage to some one, and then to another, and so on, of the indices which characterise the several polyhedra. This transformation may be performed mechanically, by constructing a hinged net, removing (i.e. replacing by fenestrae) the polygons of a certain order, and allowing those which remain to slide over and so overlap one another.—F. G. Mann and Sir William Pope: 1:2: 3-Triamino-propane and its complex metallic compounds.—D. L. Chapman, J. E. Ramsbottom, and C. G. Trotman: The union of hydrogen and oxygen in presence of silver and gold. The catalytic activity of silver is considerably reduced by heating to dull redness in oxygen, independently of the pressure of the oxygen in which it has been heated, provided that this pressure exceeds 0.005 rnm. of mercury. As the pressure of the oxygen is diminished further, the activity of the treated metal falls rapidly, reaching a ma.ximum when the oxygen pressure is 0-0013 rnm. After silver has been heated to dull redness in oxygen at a pressure higher than 0-005 mm., it would seem to be covered with a thin film of silver oxide, which is a less powerful catalyst than the metal itself. Gold furnished similar but less pronounced results. In the presence of the film of silver which was formed on the surface of the glass during the experiments, hydrogen and oxygen will combine at the temperature of the laboratory.-U. R. Evans: The colours due to thin films on metals. Mallock has objected to the interference-theory of the colours on the grounds that he had failed to alter the colours of tempered iron by polishing the metal. It has now been shown that the colovtrs can be changed when the thickness of the film is uniformly reduced by cathodic treatment in dilute hydrochloric acid. Raman has proposed that the colours are due to a granular structure; but the colours on molten lead can be obtained as easily when the oxide-film is molten as when it is solid, and thus the "granular theory "fails. The oxide-films have been lifted off molten lead, and examined, supported on glass; the colours by transmitted light are complementary to those by reflected light, as is to be expected on the interference view.-A. Campbell: On the determination of resistance in terms of mutual inductance. A new method of balancing mutual inductance against resistance is described, in which one of the conditions of balance is independent of frequency and can be set once for all, while the second condition gives a very simple relation between the frequency, two resistances and two mutual inductances.-S. Butter-worth: On the alternating-current resistance of solenoidal coils. The general theory of eddy-current losses in cylindrical conductors is employed to establish formulae for computing the alternating-current resistance of single-layer solenoidal coils. Two formulas are obtained which are shown to be in reasonable agreement with observation, except when the frequency is extremely high. The formulae should be applicable so long as the current may be regarded as having uniform distribution, throughout the coil.-A. J. Allmand and V. S. Puri: The effect of superposed alternating current on the polarisable primary cell zinc-sulphuric acid-carbon. Part I.: Low-frequency current. Ten years ago Brown showed that, if an alternating current of either 100 or 12,000 periods and of suitable intensity were passed through the above primary cell, the polarisation of the latter was reduced and its current output increased. The experiments were repeated and extended, using alternating-current frequencies of 20 to 400 cycles per second, the potentials of the two electrodes being 'measured whilst the currents were running. The results showed conclusively that, with such frequencies, the carbon electrode is chiefly responsible for the decreased polarisation and increased cell current. The lower the frequency, the greater the effect. At the same time there were certain indications that, with higher frequencies, an effect would be produced at the zinc electrode, as observed by Brown.-R. W. Lunt: The interaction of carbon dioxide and hydrogen in the corona due to alternating currents of high frequency. Alternating electric fields of frequency 1-5 x 10' have been used. An equimolecular mixture interacts, giving a water-gas equilibrium, which is also attained by exposing mixtures of carbon monoxide and water vapour to the discharge. In no case has it been possible to detect the formation of formic acid or formaldehyde. T. Royds: The apparent tripling of certain lines in arc spectra. As many spectra as possible were searched through the visible region for instances of lines becoming complex when the amount of material in the arc was increased. Only seven cases were found, all of which apparently become triple with a sufficient quantity of material. The Tl line 5350 passes through five successive phases, namely, broad simple reversal, triplet, doublet, a second triplet form, and a final doublet, as the amount of material in the arc burns out. This line is essentially a doublet, and all the different phases can be explained as different stages in the self-reversal of the two lines of the doublet. A similar explanation was adopted for the six remaining instances of apparent tripling, as all except two were found to assume a doublet form as the final phase.-E. Newbery: Over-voltage and transfer resistance.

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    Societies and Academies. Nature 115, 177–179 (1925). https://doi.org/10.1038/115177a0

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