LONDON. Royal Society, June 3.—Sir William Crookes, president, in the chair.—Prof. C. H. Lees: The shapes of the equipotential surfaces in the air near long buildings or walls, and their effect on the measurement of atmospheric potential gradients. The shapes of the equipotential surfaces are determined, and the equipotential lines drawn to scale in the following cases:—(1) A thin vertical wall; (2) a retaining wall separating a lower from a higher horizontal plane; (3) a series of equidistant parallel vertical walls. In each case the normal vertical potential gradient may be calculated from observations of the potential at any point. A point on each wall is indicated at which the horizontal potential gradient is identical with the normal vertical gradient.—Prof. O. W. Richardson: The influence of gases on the emission of electrons and ions from hot metals. As is well known, the thermionic saturation current i is expressed accurately and quite generally over wide ranges of temperature by the equation i = ATie-/T. In the case of metals, in particular, the equation is satisfied when the metals are contaminated by the presence of a gaseous atmosphere, as well as when the surfaces of the pure metals are tested. In general, however, the effect of the contaminating gas is to cause large changes in the. values of the constants A and b. The changes which are thus brought about in these constants are considered in the present paper. So far as it may be considered trustworthy, the available evidence shows that A and b for a given metal always change together in such a way that the change in log A is proportional to the change in b. This linear relation is very closely satisfied by the results of all Langmuir's observations with tungsten, for which substance different gases change A by as large a factor as 1012. A similar relation, with an almost equal coefficient of proportionality, is required by the best observations on the negative emission from platinum. In the case of tungsten, contaminants cause an increase in A and b, whereas with platinum a diminution occurs. All the known data point to the existence of a similar law governing the steady emission of positive ions from platinum. By applying thermo-dynamic considerations to the emission of electrons from contaminated surfaces, it is shown to follow from the linear relation between log A and b, tjiat the contact potential difference between the pure and the contaminated metal, is of the form a0(i - aT), where the constant a0 has opposite signs for tungsten and platinum, and a has approximately the same value for both metals. T is the absolute temperature.—Prof. J. W. Nicholson: The band spectrum associated with helium. Fowler has concluded recently that the heads of the bands in the new spectrum associated with, and perhaps due to, helium follow laws of the type hitherto peculiar to line-series. A further examination of some points which were in doubt has been made with the, following results:—(1) The paper supports the conclusion that the heads of the bands in the spectrum of Goldstein and Curtis follow ordinary series laws by showing that the doublet separations actually tend to zero at the limits of the series; (2) both the doublet series isola ted by Fowler are strictly analogous to principal series in line-spectra; (3) the generalised Rydberg formula, in which the wave number is a function of m +, gives the most suitable representation of these series as well as of line-series.—C. Dobell and A. P. Jameson: The chromosome cycle in Coccidia and Gregarines. The authors have investigated the chromosomes of a coccidian (Aggregata eberthi) and a gregarine (Diplocystis schneideri). They have found that the chromosomes are present in the haploid (“reduced”). number-six in Aggregata, three in Diplocystis-at every nuclear division in the life-history except that of the zygote nucleus. This nucleus contains the diploid number of chromosomes-twelve in Aggregata, six in Diplocystis-and its division is a reduction division which halves the chromosome number. Reduction thus occurs in these organisms immediately after fertilisation, and not during gameto-genesis.