LONDON. Royal Society, November 10.—Sir Archibald Geikie, K.C.B., president, in the chair.—Sir George Darwin: (1) The tidal observations of the British Antarctic Expedition, 1907; (2) a mistake in the instructions for a certain apparatus in tidal reductions.—F. Soddy and A. J. Sorry: Conduction of heat through rarefied gases.—II. The thermal conductivities of argon, helium, and hydrogen at very low pressure have been examined in greater detail; with new and improved apparatus. The hypothesis provisionally put forward (Roy. Soc. Proc., A, vol. Ixxxiii., 1910, p. 254), that the interchange of energy on impact:is imperfect in the lighter gases, has been tested and found not to account for the smallriess of the ratio (K/Q) of the found to the calculated conductivities. The conoductivity of hydrogen using a palladium hot wire is the same as that with a platinum wire. Change of tempera—ture of the hot surface, that of the cold surface remaining constant at room temperature, does not exert"so much influence on the value of K as was anticipated. The value of K/Q tended to diminish as the difference of temperature increased, especially at high temperatures. At low temperatures, attained by immersing the apparatus in liquid air and in solid carbon dioxide and ether, the ratio K/Q is diminished, whereas on the hypothesis of imperfect interchange of energy an increase was expected. Jacketing the apparatus with vapours up to 264° caused an increase in the value of K/Q. It appears that, most probably, increase in the difference of temperature between the surfaces tends to decrease the value of K/Q, whereas inocrease in the temperature of both surfaces increases it. Argon under some of the new conditions tried conforms to the theory hardly better than the other gases, and the agreement found previously was probably fortuitous. The general conclusion is that the conductivity at low pressures varies less with the nature of the gas and with the temperature of the experiment than is to be expected from kinetic considerations. The extreme values found for the conoductivities of the three gases over a range of about 450° lay between 0.8 and 3.4, whereas the calculated values lie between 0.95 and 16.2 (X 10-5 calorie, per sq, cm. of hot surface, per 1° difference of temperature, per 1-01 mm. pressure of gas).—W. H. Hatfleld: The chemical physics involved in the precipitation of free carbon from the alloys of the iron-carbon system. The intention of the author is to examine the conditions under which free carbon is produced in iron and steel. Whereas it has been an open question as to whether or not free carbon could be produced direct from the solid solution, the paper is intended to prove the truth of the theory that free carbon can only be produced by the dissociation of the free carbide. It is hoped to demonstrate that this theory holds good through the whole range of the alloys in which free carbon, whether as graphite or annealing carbon, is found. After the presentation of evidence in support of this view of the production of graphite in and near the freezing range, experiments, performed to determine the chemical physics underlying the liberation of annealing carbon in white cast iron, are described. By the electrolytic method of analysis the cementite carbide was obtained from such Vons of varying composition, and it is shown how, by Varying the percentage of silicon, manganese, or sulphur in the iron, the composition of the cementite is modied and its degree of stability at varying temperatures determined. It is also shown that the size and structure of the precipitated annealing carbon is largely due to the size and structure of the original cementite. Experiments performed to produce annealing carbon in blister steel during the cementation process are then described, after which an explanation of the phenomena of "black "steel is discussed; it is shown that the free carbon found in such steels may present one of two formations, each produced under different conditions. The author further endeavours to demonstrate that whilst the free cementite Carbide is dissociated at high temperatures through the whole range of the alloys, the carbide remaining in solid solution does not dissociate until the resolution of the solid solution into the carbide and iron of the pearlite, at the carbon change point.—Dr. F. Horton: A spectroscopic investigation of the nature of the carriers of positive electricky from heated aluminium phosphate. The emission of positive ions from substances heated in a vacuum;has been investigated by several experimenters, and it has been found that the ratio of the charge to the mass of the ions is the same for all the substances so far experimented on. Assuming that the charge is equal to that carried by the hydrogen ion in electrolysis, the mass of the carriers of positive electricity from heated substances, must be about, twenty-six times that of the hydrogen atom. The object of this research was to obtain the spectrum of these ions. Aluminium phosphate was chosen for investigation, because of the very large positive ionisation produced on heating this substance. A calculation showed that, with the apparatus used, it might be expected to collect a sufficient quantity of the carriers to obtain their spectrum in a small vacuum tube. The vessel used to collect the carriers was cooled in liquid air during the passage of the thermionic current from a strip of platinum covered with aluminium phosphate to a surrounding platinum cylinder. The material collected was then allowed to vaporise, and its spectrum was obtained by rendering it luminous with an electrodeless ring discharge. The spectrum of carbon monoxide was always obtained, although precautions had been taken to exclude this gas, or materials which might give rise to it, from the apparatus. It is concluded, therefore, that the positive ions consist of carbon monoxide, the molecular weight of which agrees fairly well with that required by the results of the e/m determinations. It is considered improbable that this gas is evolved on heating every substance which has been experimented on in the determinations of the specific charge, but from the nature of the apparatus used it must always have been present during these determinations. In the paper reasons are given for believing that molecules of carbon monoxide readily act as carriers of positive electricity, and this gas probably diffuses into the hot metal or other substance and is evolved in an ionised state.—N. Bohr: The determination of the tension of a recently formed water-surface. Arguments in further support of the author's previous conclusion, that the surface tension does not change sensibly with the time that has elapsed since the surface was formed.—Lord Rayleigh: Aërial plane waves of finite amplitude.—J. J. Manley: Observations on the anomalous behaviour of delicate balances, and an account of devices for increasing accuracy in weighings.—Prof. F. W. Dyson: The improbability of a random distribution of the stars in space.—G. I. Taylor: The conditions necessary for discontinuous motion in gases.—The Hon. R. J. 'strutt: (1) The radium content of basalt; (2) measurements of the rate at which helium is produced in thorianite and pitchblende, with a minimum estimate of their antiquity.