March 23, 1922] 



NATURE 



397 



traction of a minute. Crystal growth and re- j 

 rystallisation in metals probably depend on a dif- 

 rence in vapour pressure between neighbouring 

 v^rystal grains. This explains the known phenomena 

 in relation to the effect of strain, grain-size, and 

 temperature in regulating recrystallisation and grain- 

 growth on anneahng. — H. Moore and S. Beckinsale : 

 Further studies in season-cracking and its prevention : 

 condenser tubes. The properties of various con- 

 denser tubes were determined before and after 

 annealing at temperatures in the range 250°-325° C. 

 By annealing experiments on fiat strips of condenser- 

 tube brass elastically bent to an arc of a circle and 

 thus initially stressed to a known amount the effects 

 of initial hardness, initial stress, time, and tempera- 

 ture, on the reduction of initial stress by low - 

 temperature annealing were determined quantita- 

 tively. The rate of reduction of stress at the lower 

 temperatures is rapid, but slows down when the 

 stress has been considerably reduced. The higher 

 the initial stress the higher is the remaining stress 

 in brass of the same hardness, and the higher the 

 hardness the lower is the remaining stress for a 

 given initial stress. A temperature of 250°-275° 

 C. is very effective irr restoring elasticity in the 

 overstrained material. Treatment at 280° - 300° C. 

 for 30 mins. reduces initial stress to a safe limit 

 without injury to, and in some cases with marked 

 improvement in, the strength of the tube. 



March 9. — W. Rosenhain : Some cases of failure 

 in " aluminium alloys." Some " aluminium alloys " 

 ndergo distortion and disintegration; they usually 

 nsist mainly of zinc and are not properly described 

 s aluminium alloys. Such alloys, consisting largely 

 of zinc and also containing aluminium and copper, 

 are unstable at ordinary temperatures and liable to 

 changes of dimension and disintegration. True Ught 

 alloys of aluminium (consisting mainly of aluminium), 

 if properly prepared are free from any risk of serious 

 growth or disintegration. — F. C. Thompson and E. 

 Whitehead : Some mechanical properties of the 

 nickel-silvers. The effect of annealing at different 

 temperatures, and the different rates of cooling after 

 annealing, upon the tensile properties, the Arnold 

 alternating stress values, and the Erichsen values of 

 hard-rolled alloys containing lo, 15, and 20 per cent, 

 nickel were examined. Changes occur at about 

 300° C. and 550° C. Annealing at 300° C.-400° C. 

 results in a material of very low ductility. The best 

 annealing range for the 10 per cent, nickel alloy is 

 725° C.-825° C. ; for the 15 per cent, nickel, 700° C- 

 Soo° C. ; and for the 20 per cent, nickel alloy, about 

 'o" C. As the nickel content is raised the tensile 

 length is raised, while the maximum ductihty is 

 ■nsiderably reduced. As regards Brinell hardness 

 almost the whole of the softening takes place in the 

 lirst two hours. The greatest ductility and the 

 ' 'c:hest Erichsen values are obtained after anneaUng 

 1 i| hours for small samples. There is Uttle to 

 (jose between anneahng for a short time at a high 

 temperature and for a longer time at a low tempera- 

 ture. The alloys can be heated to a high temperature 

 without deterioration, especially when the sample is 

 protected from oxidation. The Erichsen tests show 

 good results even after anneahng at 850° C. — D. 

 Hanson and Miss M. L. V. Gayler : A further study 

 of the alloys of aluminium and zinc. Alloys contain- 

 ing 70, 60, 50 per cent, of zinc when slowly cooled to 

 284° C, after prolonged annealing at 420° C. and 

 quenched are duplex in structure. A redetermination 

 of the solidus from 81-20 per cent, zinc showed that 

 the hne representing the peritectic reaction extends 

 to a composition of 70 per cent, zinc as against 40 per 

 cent, zinc in previous diagrams. Microscopic examina- 



NO. 2734, VOL. 109] 



tion of alloys, following special heat-treatment, dis- 

 proved the existence of the compound AljZns, and 

 showed that the nature of the change in the alloys 

 at 256° C. in Rosenhain and Archbutt's diagram is 

 identical with an ordinary eutectoid transformation, 

 the decomposition of the j3-phase leading to the 

 " pearlitic " structure commonly found in the 

 alloys. Below 256° C. the solubility of the a- 

 constituent in the 7-constituent decreases with the 

 temperature. Alloys containing the ^-constituent 

 harden spontaneously at room temperature after 

 being quenched from above 256° C. ; those containing 

 the 7-constituent showed the same property in a 

 much less marked degree. — A. Westwood : The 

 assay of gold bullion. The assay sample is not 

 cupelled but is melted and balled up under steam 

 or an inert gas. For the usual inquartation copper 

 is recommended in place of silver. — C. A. Edwards 

 and A. J. Murphy : The rate of combination of 

 copper and phosphorus at various temperatures. 

 When using J-inch copper rod the maximum rate of 

 increase of phosphorisation in phosphorus vapour for 

 a given rise of temperature occurred at 640° C. 

 Phosphorisation at this temperature is quick and 

 safe, and the operation can be controlled so as to 

 prevent the formation of any liquid, while it is im- 

 possible to obtain an alloy containing more than 

 the percentage of phosphorus which is required 

 commercially. 



Cambridge. 



Philosophical Society, February 27. — Mr. C. T. R. 

 Wilson, vice-president, in the chair. — G. F. C. Searle : 

 (i) An experiment illustrating the conservation of 

 angular momentum. A horizontal board is suspended 

 by a practically torsionless silk thread. Attached to 

 the board is -a vertical pivot about which an inertia 

 bar turns balanced by a suitable counterweight. 

 The inertia bar is held by a thread in a definite 

 position against the action of a spring and then the 

 thread is burned. The spring turns the bar until 

 its motion relative to the board is arrested by a stop 

 and the board turns in the opposite direction. The 

 ratio of the angles turned through by board and bar 

 is equal to the ratio of the moments of inertia of the 

 bar about its pivot and of the whole system about its 

 axis. This ratio is found by means of a torsion wire. 

 (2) A focal hne method of determining the elastic 

 constants of glass. Light from a collimator, with 

 cross-wires in one focal plane, falls on the surface 

 of a bar of glass. The reflected beam falls on a con- 

 verging lens system which is adjusted so that the 

 origin point on the surface is in one focal plane. 

 A ground-glass screen on an optical bench is adjusted 

 to be in the other focal plane. Wlien the bar is bent, 

 the cross-wires are set horizontal and vertical and 

 the position of the focal lines of the reflected beam 

 is determined. Wlien the bar is tAvisted, the cross- 

 wires are set at ±45° to the horizontal and similar 

 measurements made. The glass bar is replaced by 

 a concave spherical mirror and the measurements 

 repeated. Young's modules, Poisson's ratio and the 

 rigidity can be calculated. — G. Stead and E. C. 

 Stoner : Low voltage glows in mercury vapour. 

 The effect of varying pressures and filament tempera- 

 tures on the glow potential of mercury vapour, and 

 on the current changes accompanying the appearance 

 and disappearance of the glow were investigated. 

 The glow could be obtained in a dome-shaped form 

 of variable length. At higher pressures the glow 

 point occurred below the ionisation potential. — E. V. 

 Appleton : An electric wave detector. The ther- 

 mionic current of a diode vacuum tube in which the 

 electrons move with very small velocity is deflected 

 by the direct action of electromagnetic radiation. 



