362 



NATURE 



[November ii, 1920 



course of meteorology and navigation for students 

 principally concerned with aerodynamics is being 

 given by Sir Napier Shaw, while in the latter half 

 of the "session Wing-Comdr. Cave-Brown-Cave will 

 lecture on airships. The full-time course on meteoro- 

 logy and navigation comprises a very detailed study of 

 meteorology with special attention to its bearing on aero- 

 nautics. The work is under the control of Sir Napier 

 Shaw, the late director of the Meteorological Oflice, 

 with the assistance of Squadron-Leader Wimperis as 

 lecturer on navigation. The whole programme for 

 both courses is very well arranged, and as the ser- 

 vices of such excellent lecturers have been obtained 

 it is to be hoped that a sufficient number of students 

 will be forthcoming to make the courses a success 

 and to establish firmly this new department of the 

 Imperial College. 



Societies and Academies. 



London. 

 Royal Society, November 4. — Sir J. J. Thomson, 

 president, in the chair.- — Prof. H. Lamb : The vibra- 

 tions of an elastic plate in contact with water. The 

 chief problem considered is that of determining the 

 gravest frequency of a thin elastic diaphragm filling 

 an aperture in a plane rigid wall which is in contact 

 on one side with an unlimited mass of water. This 

 had an interest in connection with submarine signal- 

 ling. An exact solution is not attempted, but a suffi- 

 cient approximation for practical purposes is obtained 

 by Rayieigh's method of an assumed type, which gives 

 good results if the type be suitably chosen. — Prof. 

 H. M. Macdonald : The transmission of electric waves 

 around the earth's surface. — Lord Rayleigh : A re- 

 examination of the light scattered by gases in respect 

 of polarisation. II. : Experiments on helium and 

 argon. The light scattered by helium and by argon 

 is investigated. It is found in the case of helium 

 that the total light scattered is in accordance with 

 what would be expected from its refractivity. The 

 polarisation in helium, contrary to what was found 

 in 19 18, is approximately complete. No intensity was 

 detected in twenty-four hours of exposure in the com- 

 ponent vibrating parallel to the exciting beam, and 

 certainly this component was less than 6-5 per cent. 

 of the other. Argon polarises much more completely 

 than any other gas examined (with the possible ex- 

 ception of helium), the weak component being only 

 0-4 per cent, of the other. — Prof. C. F. Jenkin': 

 Dilatation and compressibility of liquid carbonic acid. 

 The paper describes the measurement of the dilatation 

 and compressibility of -carbonic acid between tem- 

 peratures of -37° C. and -t-3o° C. and up to pres- 

 sures of 1400 lb. per square inch. The measurements 

 were made to supply accurate data for determining 

 the starting point for drawing the B<^ and I^ diagrams 

 and to replace the approximate results (known to be 

 inaccurate) given in a former paper (Phil. Trans., A, 

 vol.ccxiii., p. 76). — VV. T. David: Radiation in ex- 

 plosions of hydrogen and air. This paper contains 

 a_ record of the results of experiments on the emis- 

 sion of radiation during the explosion and later 

 cooling of mixtures of hydrogen and air contained in 

 a closed vessel. The results of experiments on the 

 transparency of the exploded mixtures are also 

 recorded. Some of the main conclusions arrived at 

 are as follows : (i) The rate of emission is approxi- 

 mately proportional to the fourth power of the abso- 

 lute mean gas temperature. ■ (2) The maximum rate 

 of emission occurs at the point of maximum tempera- 

 ture. (3) The exploded mixtures are very transparent 

 throughout cooling to radiation of the same kind as 



NO. 2663, VOL. 106] 



they emit. (4) The intrinsic radiance increases both 

 with the lateral dimensions and with the thickness of 

 the radiating layer of gas. (5) The 28 /u band of 

 steam ceases to be emitted when the gas temperature 

 has fallen to about 700° C— Dr. R. E. Slade and 

 G. I. Higson : Photochemical investigations of the 

 photographic plate, (i) It has been shown that the 

 silver halide grain is the photochemical unit in the 

 photographic plate., (2) A method has been devised 

 whereby the law of photochemical behaviour of these 

 grains can be investigated free from the disturbing 

 effects of development, etc., which occur in the photo- 

 graphic plate itself. (3) From experimental results 

 obtained a formula has been deduced which shows 

 the relation between the behaviour of the silver halide 

 grains, the light intensity to which they have been 

 exposed, and the time of exposure. (4) The results 

 show that it is impossible for the mechanism, of the 

 process to be the absorption of light in discrete 

 quanta, and that a given amount of light energv has 

 a greater effect photographically when concentrated 

 into a short range of wave-lengths than when it is dis. 

 tributed over a large range. — Dr. E. H. Chapman : The 

 relationship between pressure and temperature at the 

 same level in the free atmosphere. The paper deals 

 with the exceptionally high values contained in the 

 table of coefficients of correlation between changes of 

 pressure and changes of temperature at different levels 

 in the atmosphere included in Geophysical Memoir 13 

 of the Meteorological Office, by W. H. Dines. The 

 coefficients are computed for observations taken at 

 random, and arranged in four groups for the year of 

 three months each. For the layers between 4 km. 

 and 8 km. these coefficients range from 0-75 to o-g2. 

 It is assumed that if the observations were freed 

 entirely from errors of measurement the coefficients 

 would be still higher. .V method is therefore worked 

 out for correction of coefficients of correlation for 

 probable errors of observation in measurement. — Prof. 

 J. C. McLennan : Note on vacuum grating spectro- 

 scopy. 



Paris. 

 Academy of Sciences, October 18. — M. Henri 

 Deslandres in the chair. — M. Mesnager : The ap- 

 plications of the Pitot tube. Remarks on the note 

 in the last issue of the Comptes retidus by the late 

 Yves Delage. It is pointed out that the three 

 problems stated by him — transmission to a distance, 

 independence of the experimental indications and of 

 the support, and registration of the velocities — have 

 already been solved, and the first two in a simpler 

 manner. An account is given of the methods hitherto 

 proposed, all of which would be difficult to use at 

 sea. — M. Hamy : The photography of stars in full 

 daylight. An account of some experiments carried 

 out at the Observatoire des Bosses (altitude 4350 

 metres) on Mont Blanc— H. and F. Le Chatelier : 

 The mechanical properties of plastic bodies : the 

 importance of reactivity. From a study of the tor- 

 sion of glass kept at 550° C. and of steel at 825° C, 

 it is shown that there are three kinds of deforma- 

 tion : an instantaneous elastic strain, w-hich dis- 

 appears on removal of the stress ; a sub-permanent 

 deformation, produced slowly and disappearing equally 

 slowly; and, finally, a viscous deformation, produced 

 with a constant velocity and not vanishing after 

 release from stress. — M. Le Prienr : A route cor- 

 rector : a new method of aerial navigation by estima- 

 tion.- — J. L. de Olivar : Correction of the lunar co- 

 ordinates deduced from observations made at Monte- 

 video of the annular eclipse of the sun of Decem- 

 ber 3, iqi8. — E. Belot : The law of distribution of 

 masses in the solar svstem, and the origin of the 

 smaller planets. — A. Vironnet : Time and temperature 



