142 



NA TURE 



[June 8, 1905 



ment except at a verv few observatories, the author thinks 

 it is desirable to be able to estimate, even empirically, the 

 probable amounts of each. By using the meteorological 

 data published for the Royal Observatory, Greenwich he 

 has calculated the probable evaporation for the year 1898, 

 which agrees verv closelv with the observed evaporation 

 at Camden Square and also at Croydon.— On a 

 logarithmic slide-rule for reducing readings of the baro- 

 meter to sea-level : J. Ball. This has been devised for 

 the purpose of saving the time and labour usually occupied 

 in working out the corrections from the international 

 meteorological tables. 



Royal Microscopical Society, May 17.— Dr. Dukinfield 

 H. Scott, F.R.S., president, in the chair.— The movements 

 of diatoms and other microscopic plants ; D. D. Jackson. 

 The author describes the observations and experiments 

 made by him, some with artificial diatoms, which have 

 led him' to the conclusion that the movements referred to 

 are caused by the escape of oxygen gas evolved in these 

 organisms. 



Faraday Society, May 18.— Dt F. MoUwo Perkin. 

 treasurer, in the chair.— An application to electrolytes of 

 the hvdrate theory of solutions : Dr. T. Martin Lowry. 

 The object of the paper is to consider the possibility of 

 extending the hydrate theory to electrolytes in such a way 

 as to take account of the observations which form the 

 experimental basis of the theory of electrolytic dissociation. 

 The hydrate theorv postulates that an aqueous salt solution 

 consists of a mixture of hydrates in equilibrium with the 

 solvent and with one another. But it must be supposed 

 that even in solution there is a limit to the possibility of 

 hvdrate formation, so that ultimately a stage will be 

 reached at which the molecule as such will be unable to 

 combine with any further quantity of water. The ionisa- 

 tion of an aqueous electrolyte consists essentially in a 

 further process of hydration whereby the fully hydrated 

 molecule combines with an additional quantity of water to 

 form two or more hydrated ions. The hydration of the ions 

 is thus conceived to be the primary cause of the ionisation 

 of aqueous electrolytes. It is believed that this extension 

 of the hydrate theory to the phenomena of electrolysis may 

 help to remove the fundamental difficulty of .Arrhenius's 

 theory, namely, the absence of a motive for electrolytic 

 dissociation. 



Physical Society, May 26. — Meeting at ihe National 

 Physical Laboratory by invitation of the director, Dr. 

 Glazebrook. — The following special demonstrations were 

 made : — The specific heat of iron at high temperatures : 

 Dr. J. A. Harker. .\ knowledge of the specific heat of 

 iron is important in the determination of high temperatures 

 by calorimetric methods. Dr. Harker has determined the 

 total heat of iron up to temperatures of 900° C. by heating 

 the specimen in an electric furnace, the temperature of 

 which was determined by a resistance thermometer, and 

 dropping the iron into a water calorimeter. Dr. Harker 

 also exhibited some new types of electric furnace for the 

 attainment in absence of noxious gases of temperatures 

 between 800° C. and 2200° C. The conductor conveying 

 the electric current is a tube of solid electrolytes similar in 

 composition to the filament of a Nernst lamp. .An essential 

 feature is that, for many purposes, the usefulness and life 

 of a furnace constructed in this way may be much increased 

 by adopting a " cascade " system of heating. — Apparatus 

 for the measurement of small inductances : A. Campbell. 

 The method of measurement is that adopted by Max 

 Wien, and described by him in a paper on " Magnetisation 

 by .■\lternating Currents " (Wied. Ann., xiii., .August, 1898). 

 It is a modification of Maxwell's method of comparing 

 two self-inductances, the source of voltage being alter- 

 nating, and the indicating instrument a tuned optical 

 telephone cr vibration galvanometer. — Two new optical 

 benches constructed for the laboratory by Messrs. R. and 

 J. Beck : J. Selby. One of these is specially designed for 

 the rapid testing of spherical and cylindrical lenses, such 

 Hs are found in oculists' trial cases. The second bench is 

 designed for the determination of the loss of light by 

 absorption and reflecticn in telescopes and binoculars. 



NO. if^sS, VOX. 72I 



Cambridge. 



Philosophical Society, May i.— Prof. Liveing, vice- 

 president, in the chair.— On the striation of the positive 

 column ih electric discharges : Prof. Thomson. The 

 author considered the ionisation in a discharge tube by the 

 collision of charged ions as well as of corpuscles against the 

 molecules of a gas, and showed that if the pressure in the 

 tube and the electric current through it had values situated 

 between certain limits, there would be periodic alternations 

 in the positive column analogous to striations.— On the 

 calculation of the coefBcient of re-combination of the ions 

 and the size of the ions : Prof. Thomson. The re-combin- 

 ation of ions is due to oppositely charged ions attracting 

 each other and forming a single system. When the ions, 

 are at a distance r apart the work required to separate 

 them to an infinite distance is e'/r, hence two ions start- 

 ing from a distance r apart will not describe closed orbits 

 about each other, i.e. will not combine if their kinetic 

 energy is greater than e-jt. Since the ions behave like 

 the molecules of a gas, their kinetic energy will depend 

 only upon the temperature, and can be calculated when 

 that is known. If T is this kinetic energy, then for com- 

 bination to take place e'lr must be greater than T, or r 

 less than c=/T. Hence to find the number of re-combin- 

 ations in any time, all we have to do is to find the 

 number of pairs of ions which within that time get within 

 a distance e=/T of each other. This number, and hence 

 the coefficient of re-combination, is easily calculated. If 

 we assume that the ions in hydrogen are charged molecules 

 of hydrogen, the coefficient of re-combination at 0° C. 

 would be 1-5x10-'; the value found by experiment is 

 about 10-', "hence we conclude that the hydrogen ion is 

 more complex than the hydrogen molecule. The kinetic 

 energy due to temperature is shown to prevent the ions 

 getting very much larger than the molecules ; thus if the 

 radius of the molecule were 10-* cm., the radius of the 

 ion could not exceed 3x10-'.— Some physical properties 

 of sodium vapour : P. V. Sevan. The experiments de- 

 scribed in this paper were made to investigate the pheno- 

 mena of the cloud of sodium -vapour formed by healing 

 a piece of metallic sodium in vacuo or in an atmosphere 

 of hydrogen. In certain circumstances the sodium vapour 

 forms a verv sharply defined cloud with apparently a 

 definite surface across which diffusion does not take place. 

 The formation of this cloud, which was discovered by 

 Prof. R. W. Wood, was found to be conditioned by the 

 presence of water vapour in the atmosphere in which 

 the sodium was heated. In vacuo the sodium vapour 

 behaves like any other vapour, and in perfectly dry 

 hydrogen there is no definite surface to the vapour observ- 

 able when the sodium is heated. It was also shown that 

 in vacuo the sodium begins to form vapour at the tempera- 

 ture of boiling water. The view is put forward that when 

 the sodium cloud is seen on heating sodium in a vacuum 

 tube the effect is due to the formation of an atmosphere 

 of hydrogen occluded by the sodium and formed by the 

 action of the sodium on sodium hydroxide. — A null method 

 of measuring small ionisations : N. R. Campbell. 

 Measurements have been made of spontaneous ionisations 

 by adjusting the pressure of the air in a closed vessel con- 

 taining a constant amount of uranium until the current 

 through that vessel was equal and opposite to that through 

 the spontaneously ionised gas. By this device certain 

 difficulties connected with the measurement of capacity and 

 the preservation of insulation are avoided. — The reflexion 

 of sound at a paraboloid : Rev. H. J. Sharpe. 



Dublin. 



Royal I uhlin Society, April 18. — Pri-.f. J. A. McCI.-llanc) 

 in the chair. — Notes on the constitution of nitric acid and 

 its hydrates : W. Noel Hartley. The author referred to a 

 paper by him published in 1903 in the Client. Soc. Trans. 

 on the absorption spectra of nitric acid in various states 

 of concentration. He had assigned the formula H,NO, 

 to normal nitric acid, and suggested that the several 

 hydrates described were hydrates of this acid ; but H. 

 Erdmann, also in 1903, having isolated and described five 

 nitric acids, the author was led to revise the formulae of 

 the hydrates in accordance with the constitution of these 



