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A brief review of established methods shows that only with the Berthelot technique is it possible to see a finite volume of liquid in sustained mechanical tension. A short discussion of the practice and theory reveals two uncertainties with the conventional technique : that of the determination of a true filling temperature, and the influence of compliance by the glass on the tension developed. A description is then given of a modified apparatus with which these difficulties do not arise. The tube is formed into a coil which deflects sufficiently to indicate internal pressure or tension, and by monitoring these deflections with a distance meter a record of pressure/ tension against temperature can be made. The course of a typical run is shown from which the excess pressure, filling temperature and limiting tension may all be estimated with much greater precision than befoie. The orders of magnitude of the results obtained are indicated, and a possible influence of non-uniform gaseous supersaturation is suggested.

The quality of the output beam from a CO2 electron beam laser may be seriously affected by density perturbations within the laser cavity. For the first time in open literature publications, results are given from numerical modelling which indicate that the heating differential between lasing and non-lasing regimes is sufficient to account for these density perturbations. Our numerical results are in good agreement with results from experiment for the case of the stable resonator. We have extended our model to predict the degradation of the output beam from an unstable resonator.

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In a previous paper, we discussed the use of multiaxial magnetic structures in rareearth compounds as test systems for x-ray scattering by orbital non-collinear 4f structures. We here present an experiment using synchrotron radiation, which, meanwhile, has given encouraging results regarding this use of x-ray diffraction: the scattering of x-rays by NdMg within its multiaxial magnetic phase yields tiny Bragg reflections which are very likely to be of quadrupolar origin. Indeed, these peaks have been found at the positions and with the intensities expected for such a charge scattering.