I4S 



NA TURE 



[ December 3, 190b 



was demonstrated by the actual determination Cubing a 

 simple projection apparatus and screen) of the optical con- 

 stants, twin-law, and chemical composition of a plagioclase 

 twin. Methods of determining birefringence and the thick- 

 ness of a section were discussed, and emphasis was laid 

 on the special usefulness of the three-legged compasses in 

 rapid calculations by graphical methods. — The composition 

 of the Chandakapur meteoric stone : H. E. Clarke and 

 H. L. Bowman. This meteorite, which fell in India in 

 1838, is of chondritic type, with numerous chondrules of 

 varying- structure, and consists principally of olivine and 

 bronzite, and about 5 per cent, of nickel-iron. 



Geological Societv. N .v-i..lier 18.— Pro''. W J. Soils', 

 F.R.S., president, in the chair. — Some intrusive rocks in 

 the neighbourhood of Eskdale (Cumberland) : Dr. A. R. 

 Dwerryhouse. There appear to be five well-marked 

 groups of intrusions in this district : — (a) the andesitic 

 dykes of Allen Crags and Angle Tarn ; {Jo) the dykes of 

 the spherulitic group on Yewbarrow and High Fell ; (c) the 

 dioritic bosses of Peers Gill, Lingmell Crag, and Bursting 

 Knotts : {d) the Eskdale Granite ; (c) the dolerite-dykes'. 

 The dykes of series (a) bear a petrological resemblance 

 to the Borrowdaie volcanic rocks, into which they were 

 intruded. They appear to be of Borrowdaie age, and 

 roughly contemporaneous with the lavas and ashes into 

 which they are intruded. The spherulitic series (b) are 

 considered to be also of Borrowdaie age, though probably 

 somewhat later, and the rocks of group (c) to be the 

 holocrystalline equivalents of the Borrowdaie lavas, and 

 they also are probably of Ordovician age. The Eskdale 

 Granite id) is more acid. It is undoubtedly intrusive into 

 the Borrowdaie series, but seems to be pre-Triassic. The 

 intrusion is probably Devonian. The basic intrusions (c) 

 have been examined only where they come into proxiniitv 

 to the granite. 



Linnean Society, Niv»mbT tq.^D-. D. If. Scott. 

 F.R.S., president, in the chair. — The optical behaviour of 

 the epidermal cells of leaves (see Natl're, November iq, 

 p. 86) : H. Wagrer. — \ new species of Symphyla from 

 the Himalayas: Prof. A. D. Imms. — The freshwater 

 Crustacea of Tasmania, with remarks on their geographical 

 distribution : G. Smith. 



Royal AnthroDOlogical Institute, November 1%. — Prof. 

 W. Gowland, F.R.S., past-president, in the chair. — 

 Primitive pottery and iron-working in British East Africa : 

 W. S. Routledgre. After explaining the method of 

 obtaining fire by friction adopted by the natives, the author 

 proceeded to demonstrate the method by which pots were 

 made. No wheel is used, but the pot is most carefully 

 worked up by hand. .An interesting feature is that the 

 pot is made in two parts. .Ml pottery is made by the 

 women. The interest of the description was greatly 

 heightened by an exhibit of pottery in all the different 

 stages of manufacture. With regard to iron working, 

 the author explained the manner in which the iron is 

 washed from the sand and the way in which it was 

 smelted in a large crucible dug out of the earth. From 

 the iron thus obtained implements are made, and a large 

 selection of examples was exhibited. Iron wire is also 

 drawn, and the author gave a demonstration of the manner 

 in which this is done. 



C.\MI!RIDGE. 



Philosophical Society, October 26.— Note oti Rus so's 

 attempt to show differentiation of sex in the ovarian ova 

 of the rabbit : W. Heape. — A further note on the eggs of 

 the hermaphrodite Ans^iosiomum nigrovenosum : S. A. 

 McDowali — Plemelj's canonical form : J. Mercer. — 

 Monotone sequences of continuous functions : Dr. Young. 

 — The operator reciprocants of Sylvester's theory of 

 rociprocants : Major P. A. MacMahon. 



November 9. — Prof. Sedgwick, president, in the chair.— 

 The c.3rriers of the positive charge of electricitv given off 

 by hot metals : Sir J. J. Thomson. The paper contains 

 an account of measurements e/m for the carriers of the 

 positive electricity given off bv incandescent metals. The 

 method used was that described in a paper by the author 



vo. 2040, voT,. yq] 



on rays of positive electricity in the Philosophical Maga- 

 zine for October, and is an improvement on that used by 

 him to measure ejm for the particles given out by hot 

 wires some years ago. The values of t'/in given in the 

 present paper, taken in conjunction with other evidence, 

 suggest that the carriers of the positive electricity given 

 out by hot wires are mainly molecules of carbon monoxide. 

 — The weight of a corpuscle on the electrical theory of 

 gravitation : Sir J. J. Thomson. It was shown that, on 

 the theory that gravitation was due to slight differences 

 between the forces between like and unlike charges of 

 electricity, the acceleration of a corpuscle under gravity 

 might be expected to be about one thousand times 

 the acceleration of ordinary matter. — The distribution of 

 electric force along the striated discharge : Sir J. ]. 

 Thomson. A W'ehnelt hot-lime kathode was used to pro- 

 duce the discharge, as it was found that at low pressures 

 the striations produced in this wav were remarkably steady 

 and bright, and in consequence made accurate measure- 

 ments of the distribution of electric force much easier than 

 with the ordinary discharge. It was found that just iri 

 front of the bright surface of a strialion towards the 

 kathode there was a reversal of the electric force. This 

 reversal causes a great accumulation of ions in the part 

 of the striation nearest the kathode ; the re-combination 

 of the ions in this region will therefore be much greater 

 than elsewhere, and it is shown that a very simple ex- 

 planation of the formation and behaviour of striations was 

 given by the hypothesis that the re-combination of the 

 ions was the source of the luminosity in the striations. — 

 Note on the radio-activity of rubidium : N. R. Campbell. 

 Measurements on rubidium have been made similar to 

 those on potassium described in a recent communication. 

 It is shown that the rays from rubidium are less pene- 

 trating than those from potassium, but that the total 

 activity of the former metal is some seven times as great 

 as that of the latter. — The free pressure in osmosis : L. 

 Vegrard. The work contains a series of experiments 

 made in order to obtain some information regarding the 

 mechanism underlying osmotic phenomena. The experi- 

 ments consist in the determination of osmotic velocities 

 developed in a membrane of copper ferrocyanide by solu- 

 tions of cane sugar of different concentrations, together 

 with the determination of the resistance of the membrane 

 against the flow of solvent. The author concludes that in 

 osmosis the solution is restricted to a very thin layer, and 

 the motion in the rest of the membrane is caused by the 

 so-called free pressure, which is a negative hydrostatic 

 pressure inside the membrane produced by the osmotic 

 activity in the layer next to the solution. It is shown 

 that for small velocities the free pressure is equal to the 

 osmotic pressure, and that for higher concentrations the 

 free pressure corresponding to the stationary state is equal 

 to the friction pressure necessary to produce a velocity 

 equal to the osmotic velocity. — The laws of mobility and 

 diffusion of the ions formed in gaseous media : E. M. 

 Wellisch. Expressions have been deduced from the 

 kinetic theory of gases for the mobility and coefficient of 

 diffusion of an ion, allowance being made for the increase 

 in collision frequency due to the polarisation of the neutral 

 molecules by the charge associated with the ion. This 

 charge is shown to be replaceable, so far as collisions are 

 concerned, by an extension of the sphere of force of the 

 ionic nucleus. The expressions given involve only known 

 physical constants of the gas, and are therefore directly 

 comparable with the values as determined experimentally. 

 It is found that the observed values of the mobilities and 

 diffusion coefficients, as well as certain deviations from 

 the mobility-pressure law, can be approximately explainrd 

 on the supposition that the ion consists of a single moli - 

 cule of the gas with which is associated a charge pqu.il 

 to that carried by the monovalent ion in electrolysis. 



Manxiiester. 

 Literary and Philosophical Society, November 17. — 

 Prof. H. B. Dixon, F.R.S., president, in the chair. — 

 Contributions to a study of the geographical distribution 

 of birds, part i., the genus Macronyx, Swainson t F. 

 Nicholson. This paper, the first of a series embodying 

 a mass of notes on the Motacillida; (wagtails and pipits) 



