Abstract
LONDON. Royal Society, November 12.—Sir William Bragg and R. E. Gibbs: The structure of α and β quartz. The original investigations upon α quartz left four unknown parameters, namely, the distance of the silicon atoms from the trigonal axis and the spatial relations of the oxygen to the silicon atoms. One parameter could be estimated from the results of intensity measurements, but more data were required. At 573°, α quartz undergoes a transition to the β hexagonal variety, probably with little structural change. If, therefore, the β structure could be determined, that of the α would become nearer solution. The evidence of theoretical calculations and of X-ray rotation photographs of quartz above its transition point shows that in the β structure the oxygens surround the silicon atoms tetrahedrally, and that the spirals parallel to the principal axis are formed by alternate atoms of silicon and oxygen. Atomic dimensions are consistent with the normal values, and the structure agrees with requirements. The structure is consistent with the development of pyro- and piezoelectricity and compatible with the theory of electrical conductivity.—Lord Rayleigh: The light of the night sky: its intensity variations when analysed by colour filters (ii.). The observations now extend over nearly 2/12 years. The intensities of the various chromatic components of the light undergo important variations when measured against a fixed terrestrial standard, and the components also undergo considerable relative variations when measured against one another. Attention is primarily concentrated on the spectral region transmitted by a screen designed to isolate the green auroral line as nearly as possible. Notwithstanding the definite relative variations, this auroral intensity is highly correlated with the intensity in the orange-red region, not so highly with the blue region, and still less with the photographic region centred near λ4300. The values found for the correlation coefficients are: Aurora-red, 0.70; Aurora-blue, 0.66; Aurora-photographic, 0.44. On the other hand, the auroral intensity is not correlated appreciably with the degree of magnetic disturbance or the height of the barometer. The connexion with the sun-spots, if any, is not yet apparent. The intensity does not vary measurably with the sun's distance below the horizon, within the limits, evening and morning, when twilight is excluded. Parallel observations of the auroral intensity at Pasadena, and at Mt. Wilson, California, are, in the mean, more than double those prevailing in England.—W. A. Bone and G. W. Andrew: Studies upon catalytic combustion. Pt. i. The rate of combination of a (moist) theoretical mixture of carbon monoxide and oxygen (2CO +O2) in contact with a gold surface in a “normal” state of activity at 300° C. or thereabouts is always proportional to its pressure. The “normal” catalysing power of the surface at such a temperature can be (a) greatly diminished by either keeping it at the room temperature for some days or prolonged evacuation of it at 300° C., or (b) highly stimulated by previous exposure to either of the two reacting gases at 300° C. Whenever, starting with the surface in a state of “normal” activity, either one or other of the two reacting gases is present in excess, the subsequent rate of combination, which rapidly becomes “supernormal,” is always proportional to the partial pressure of the carbon monoxide. It is considered that an “activation” occurs of both of the combining gases of the surface, which is not confined to superficially “adsorbed” gas-films of monomolecular thickness, but extends also to more deeply occluded gases.—O. W. Richardson. and F. C. Chalklin: The excitation of soft X-rays. When the curves between efficiency of X-ray emission and primary voltage using a photo-electric method are plotted, a number of abrupt changes of slope are observed. Within the range 40–600 volts, four such discontinuities, of which the lowest one is complex, have been observed for carbon, 13 for tungsten, 10 to 13 for nickel, and 15 for iron. Some of these discontinuities are due to the excitation of characteristic X-rays and allied phenomena. The total X-radiation per electron impact is approximately proportional to the square root of the atomic number, for the target elements tested, and to the square of the energy of the impinging electrons.—R. Campbell Thompson: On the chemistry of the ancient Assyrians. Ashur-banipal's library of clay tablets inscribed in cuneiform in the seventh century B.C., excavated at Nineveh and now preserved in the British Museum, included tablets now in 24 fragments, giving the native Assyrian receipts for making glazes, glass, and their colours. The first section of these chemical texts describes the furnace for the glass, the magical formulae necessary, and the fuel of *Styrax-logs. The next few sections detail the ingredients for making the celebrated blue glaze, first with a frit of 10 parts sand, 15 alkali, and 1/23 *Styrax-gum, followed by copper-scale, prepared by heating, and the subsequent directions for its admixture. Glasses were of three kinds: sirçu (60 parts sand, 180 alkali, 5 salt(petre), 2 chalk); dushū (crystal) (60 sand, 180 alkali, 6 salt(petre), /12 chalk, 3 oxide of tin (?), 3/10 oyster shell (?)); and zukū (components mutilated). The most interesting receipt is to make ‘bahrē’-stone (red coral (?)), approximately 7200 parts of zukū-glass, 32 oxide of tin (?), 20 antimony, some salt(petre), and i part of go(ld), which suggests the well-known Purple of Cassius.—J. E. Lennard-Jones: On the forces between atoms and ions. The repulsive fields of 20 atoms and ions have been determined. Applications of the results are made to evaluate the interatomic distances of 32 crystals, including 16 alkaline halogens. In the case of the latter, the calculated values are found to lie, with one exception, within 1 or 2 per cent. of the observed distances.—F. G. Mann and Sir William Pope: ft β, β′,β″ triaminotri-ethylamine and its complex metallic derivatives. The preparation of triaminotriethylamine hydrochloride from bromethylphthalimide has been improved. This amine acts as a tetracidic base, according as the tertiary nitrogen atom exerts or fails to exert its basicity. Consequently, two distinct series of aurichlorides, platinichlorides, and rhodiochlorides have been prepared. Co-ordinated derivatives of the base with divalent and tetravalent metals have been prepared: in all these compounds the amine acts as a tetracidic base, and satisfies four co-ordination valencies of the metallic complex.—K. R. Ramana-than: The structure of molecules in relation to their optical anisotropy. Pt. ii.—E. V. Appleton and M. A. F. Barnett: On some direct evidence for downward atmospheric reflection of electric rays. In a study of signal variations at short distances (18-100 miles) from a short-wave transmitter, by changing the wave-length of the transmitter continuously through a small range, interference phenomena were observed, indicating the existence of two or more rays. Experiments made at Cambridge on the signals from London (2LO) have shown that the signal variations are greater on a loop antenna than on a vertical aerial, the ratio of the variations indicating that the direction of propagation of the down-coming waves makes an angle of 65°-7o° with the ground. The existence of down-coming waves has been demonstrated at distances of 18 miles from a transmitter, which indicates that the ionised layer reflects waves at almost normal incidence. The rays returned from the upper atmosphere are of complex polarisation, as is to be expected according to the magneto-ionic theory of wave propagation, and are of sufficient intensity to be responsible for the directional errors experienced in short-distance transmission. An inferior limit for the number of electrons per cubic centimetre in the ionised layer is 105.
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Societies and Academies. Nature 116, 768–771 (1925). https://doi.org/10.1038/116768b0
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DOI: https://doi.org/10.1038/116768b0