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Gravitational anisotropy of crystals
Jan., 1925.]
CURRENT TOPICS.
I37
Acceleration of the Decay of L i g h t from Phosphorescing Bodies. E. RuPP. (Ann. d. Physik, Vol. 75, No. 3 . ) - - F o r a long time it has been known that heating a phosphorescing substance makes its light die away more rapidly and that the same effect is caused by illuminating it with light different from that which excited it. More recently Gudden and Pohl found that the application of a strong electric field brings about the same result. In this paper it is shown that a strong magnetic field also is effective. No effect is produced by magnetic fields of strength less than 20,000 gausses. Even with the highest attainable strength, 45,000 gausses, the change was much less than that due to the application of a field of IO,OOO volts per cm. The sudden creation of the magnetic field causes the phosphorescing substance to grow brighter, after which there comes a period of decay. Moreover the light emitted by ZnS when the field is turned on is partially polarized perpendicular to the magnetic lines of force. G. F. S. Gravitational Anisotropy of Crystals. PAUL R. HEYL. (Scientific Papers, Bureau of Standards, 482.)--" Einstein's theory of gravitation is based upon a fundamental postulate which asserts that gravitation and inertia are identical in nature and hence indistinguishable. This is, if true, of the greatest theoretical importance, for gravitation has hitherto refused to show any relationship to other physical phenomena. A most delicate test of this postulate is possible in a crystal of one of the non-isotropic systems; for in such a crystal every known physical property (except inertia and, possibly, weight) varies with the axial direction in the crystal; and it is an interesting question whether, in such a crystal, gravitation will be found to align itself with inertia or will show some variability that will classify it with the great majority of physical phenomena." Doctor Heyl weighed large crystals of all the five non-isotropic systems, placing them in different axial positions. Moreover he weighed them to one part in IO9, but he could find no difference in the weights, so that his results declare in favor of Einstein's postulate. G.F.S. An Experimental Study of the Viscous Properties of W a t e r Vapor. C . J . SMITH. (Proc. Royal Soc., A 735.)--Though steam is of so great technical importance, but little attention has been paid to its viscosity. In this paper this property has been investigated at temperatures ranging from IOO° to 26o ° C. Pressures of only a few centimetres of mercury were used, but, since " t h e work produces reliable evidence that under the experimental conditions the viscosity is independent of pressure," the results attained can be applied to the higher pressures that obtain in practice. For the four temperatures, IOO °, 151.2 °, 2o7.I ° and 261.3 ° C., the coefficient of viscosity is found to equal 1.27, 1.45, 1.68 and 1.9o, all multiplied by IO-*. G. F. S. VOL. I99, No. 1189----10
CURRENT TOPICS.
I37
Acceleration of the Decay of L i g h t from Phosphorescing Bodies. E. RuPP. (Ann. d. Physik, Vol. 75, No. 3 . ) - - F o r a long time it has been known that heating a phosphorescing substance makes its light die away more rapidly and that the same effect is caused by illuminating it with light different from that which excited it. More recently Gudden and Pohl found that the application of a strong electric field brings about the same result. In this paper it is shown that a strong magnetic field also is effective. No effect is produced by magnetic fields of strength less than 20,000 gausses. Even with the highest attainable strength, 45,000 gausses, the change was much less than that due to the application of a field of IO,OOO volts per cm. The sudden creation of the magnetic field causes the phosphorescing substance to grow brighter, after which there comes a period of decay. Moreover the light emitted by ZnS when the field is turned on is partially polarized perpendicular to the magnetic lines of force. G. F. S. Gravitational Anisotropy of Crystals. PAUL R. HEYL. (Scientific Papers, Bureau of Standards, 482.)--" Einstein's theory of gravitation is based upon a fundamental postulate which asserts that gravitation and inertia are identical in nature and hence indistinguishable. This is, if true, of the greatest theoretical importance, for gravitation has hitherto refused to show any relationship to other physical phenomena. A most delicate test of this postulate is possible in a crystal of one of the non-isotropic systems; for in such a crystal every known physical property (except inertia and, possibly, weight) varies with the axial direction in the crystal; and it is an interesting question whether, in such a crystal, gravitation will be found to align itself with inertia or will show some variability that will classify it with the great majority of physical phenomena." Doctor Heyl weighed large crystals of all the five non-isotropic systems, placing them in different axial positions. Moreover he weighed them to one part in IO9, but he could find no difference in the weights, so that his results declare in favor of Einstein's postulate. G.F.S. An Experimental Study of the Viscous Properties of W a t e r Vapor. C . J . SMITH. (Proc. Royal Soc., A 735.)--Though steam is of so great technical importance, but little attention has been paid to its viscosity. In this paper this property has been investigated at temperatures ranging from IOO° to 26o ° C. Pressures of only a few centimetres of mercury were used, but, since " t h e work produces reliable evidence that under the experimental conditions the viscosity is independent of pressure," the results attained can be applied to the higher pressures that obtain in practice. For the four temperatures, IOO °, 151.2 °, 2o7.I ° and 261.3 ° C., the coefficient of viscosity is found to equal 1.27, 1.45, 1.68 and 1.9o, all multiplied by IO-*. G. F. S. VOL. I99, No. 1189----10