December 3, 1908] 



NATURE 



147 



By means of platinum wires sealed through the glass tube, 

 a contact is made respectively with the platinum plate and 

 the liquid alloy. When the surface of the alloy is illu- 

 minated by a powerful beam of light, and the galvano- 

 meter connected to the platinum plate and alloy, it is 

 found that a current is produced in this circuit merely by 

 the action of the light, and by balancing this current 

 against a variable electromotive force it was shown that an 

 electromotive force varying from 0^4 to o-S of a volt is pro- 

 duced in the photoelectric cell due to the action of the light. 

 This photoelectric effect was greatly dependent on the 

 colour of the light, and especially upon light absorbed by 

 the alloy. It is greatly diminished by making even a feeble 

 magnetic field parallel to the surface of the alloy. .Some 

 questions were discussed tending to show that the source 

 of the photoelectromotive force cannot be identical with 

 the volta-contact electromotive force in the circuit, but is 

 due to the absorption of light by the sensitive surface. In 

 all cases of such photoelectric action, the rays which are 

 effective in producing it are those given out by the substance 

 if heated or otherwise made radiant. Thus, zinc is photo- 

 electric under the action of ultra-violet light, and ultra-violet 

 light is largely radiated when an electric spark is taken 

 between the zinc balls, or an electric arc between zinc 

 poles. The photoelectric effects in the case of potassium 

 are probably due to the absorption of the violet ray emitted 

 by potassium when heated. — Electric splashes on photo- 

 graphic plates : A. W. Porter. The author showed, by 

 means of transparencies, the effect of a normal magnetic 

 field upon the patterns which appear in developing a photo- 

 graphic plate which is placed between two terminals between 

 which a sudden discharge passes. This effect is confined 

 to the main line of discharge, and consists in this line 

 being broadened into a band of nearly constant width ; a 

 very similar result is obtained if a blast of air sweeps 

 across the plate instead of the magnetic field being em- 

 ployed. This broad band is produced by the glowing gas 

 which surrounds the spark itself. The palm-like figures 

 and the ramifications leading up to them do not seem to 

 be modified by the magnetic field, and the author concludes 

 that these figures are, therefore, determined by events 

 independent of the motion of the changes conveyed along 

 them, or else that the moving charges have a very large 

 mass associated with them.^^.An anomaly in the lagging of 

 thin wires and narrow pipes : .'\. W. Porter. When thin 

 wires and narrow pipes are covered with a lagging material, 

 it is not possible at once to say whether the covering will 

 keep heat in or assist it to escape. There is a critical 

 radius equal to the ratio of the conductivity of the material 

 to the emissivity from its surface which the outer cover- 

 ing must exceed before it begins to act as a lagger. 

 .Mthough this seems to have been recognised by Prof. 

 Bottonili»y and others, the results of experiments which 

 have previously been made would seem to indicate that 

 the effect in practice is very small indeed. The author 

 showed a simple lecture experiment in which a large effect 

 is obtained. — The rate of growth of viscosity in con- 

 gealing solutions : A. O. Rankine. The author exhibited 

 apparatus and described experiments for the determination 

 of the time variation at constant temperature of the vis- 

 cosity of gelatin solutions of high concentration. — Note on 

 the re-combi'nation of ions in air : Dr. Phillips. 



Royal Astronomical Society, November 13. — Mr. H. F. 



Newall, president, in the chair. — Photographs of comet c 

 (Moreliousi), taken at the Royal Observatory, Greenwich : 

 Astronomer Royal. The first photograph was obtained 

 on September 4, and subsequent plates showed such re- 

 markable changes that it was arranged that the comet 

 should l>e' photographed at very short intervals. Mr. 

 Davidson and Mr. Melotte had obtained a long series of 

 negatives, often at intervals of an hour or less, and lantern 

 slides from these were shown on the screen. They were 

 mostly taken with the 30-inch reflector, a shorter series 

 being obtained with a 3j-inch p>ortrait lens. The tail exhibits 

 a recurring series of phases, and the phase seems to bear 

 a relation to the condition of the nucleus, which passes 

 through cycles of alternating activity and quiescence. A 

 series of photographs taken by Prof. Barnard with various 

 lenses at the Yerkes Observatory was shown on the 



NO. 2040, VOL. 79] 



screen, and Mr. Percy .Morris showed another series taken 

 by himself. Father Cortie said that his measures of the 

 plates show-ed that matter ejected from the nucleus moved 

 with an accelerating velocity. The .\stronomer Royal and 

 the president directed attention to dark rays in some of 

 the photographs. — Note on the number of faint stars with 

 large proper motions : H. H. Turner. The number of 

 faint stars with motions of more than 20" per century was 

 singularly small. — The absorption of light in its passage 

 through interstellar space: H. H. Turner. If the universe 

 is infinite, the number of stars would theoretically be four 

 limes greater for each fainter magnitude, but, as observed, 

 it was only three times greater. The hypothesis that light 

 is absorbed by scattered material particles would appar- 

 ently explain the discrepancy, and photography with 

 coloured screens was suggested as a crucial test. — Mr. 

 Cookson showed . Prof. Hale's spectroheliographs, ex- 

 hibiting vortex motion on the solar surface, especially con- 

 nected with sun-spots. Vortices north and south of the 

 solar equator appeared to move in opposite directions. — 

 The calendar dates in Aramaic papyri from .\ssuan : J. K. 

 Fotheringham. — Note on the regnal years in the .-\ramaic 

 papyri from .'\ssuan : E. B. Knobel. 



Zoological Society, November 17. — I'lof. E. A. Minchin, 

 vice-president, in the chair. — A new genus and species of 

 slow-lemurs from the Lushai Hills, .Assam : Dr. N. 

 Annandale. The animal is known only from a photo- 

 graph of two individuals taken in 1889 by Mr. T. D. La 

 Touche, and resembles Nycticebus in appearance, but has 

 a long, bushy tail, which distinguishes it from all known 

 Oriental lemurs. — Contributions to the morphology of the 

 group Neritacea of aspidobranch gastropods, part i., the 

 Neritidse : Prof. G. C. Bourne. .As a result of the com- 

 parative study of the anatomy of several species of marine, 

 estuarine, and freshwater Neritidte, the author found that 

 the forms hitherto classed in the genera Nerita, Neritina, 

 and Septaria fall into three well-known groups of sub- 

 generic value, the chief distinctive characters relating to 

 the accessory genital organs. The investigation had been 

 pursued by the study of sections as well as by dissections, 

 and a number of important anatomical results were set 

 forth. — An account of the expedition organised to collect 

 in the Ruwenzori range of mountains in Equatorial Africa : 

 W. R. Ogilvie-Grant. The results were extremely suc- 

 cessful, amongst the specimens obtained being 404 Mam- 

 malia, 2470 Aves, 135 Reptiles and Batrachia, 31 Pisces, 

 and a very large number of invertebrates. .-\ number of 

 memoirs on the zoological results of the expedition were 

 presented to the meeting, and will be published in the 

 Scientific Transactions of the society. 



Mineralogical Society, November 17.— Prof HA. Miers, 

 F.R.S., president, in the chair.— Mica from North Wales 

 and chlorite from Connemara : A. Hutchinson and 

 W. Campbell Smith. A mica from Tan-y-bwlch, North 

 Wales, is found in pale green scales in quartz veins, and 

 approximates closely in composition to the variety of 

 muscovite known as sericite. A chloritic mineral from 

 Recess occurs in transparent hexagonal plates in the 

 quarry whence the Connemara marble is obtained. It is 

 nearly uniaxial and positive, and was found on analysis 

 to have the composition of penninite. — The occurrence of 

 the rare mineral carminite in Cornwall : k. Russell. 

 This mineral, an arsenate of iron and lead, first found at 

 Horhausen, Rhenish Prussia, and described by F. Sand- 

 berger in 1850, was discovered in Cornwall by the author 

 in 1906. It occurs as carmine-red or brown needles on 

 crystallised scorodite, mimetite, &c., from Hingston Down 

 mine. This adds one more species to the already long list 

 of rare minerals yielded bv Cornwall.— Russian universal 

 instruments and methods : T. V. Barker. Several of the 

 universal instruments devised, and kindly lent, by Prof. 

 E. Fedoroff were exhibited, and the method of working 

 explained. Among the instruments described were the 

 hemisphere and graduated rotatory quartz compensator of 

 Prof. V. Nikitin, the stereographic rule, circle-ruler, 

 graduated mica and quartz compensators, universal crystal 

 mirror-models and globes, the microdichroscope, and the 

 universal microscope'^stage. The great utility of the latter 



