Junk 3. 1909J 



NA TURE 



419 



SOCIETIES AND ACADEMIES. 



London. 

 Geological Society, May 12.— Prof. W. J. SoUas, F.R.S., 

 prcsidenl, and afterwards Dr. J. J. H. Teall, F.R.S., vice- 

 president, in the chair. — The Hartfell-Valentian succession 

 around Plynlimon and Pont Erwyd (North Cardiganshire) : 

 O. T. Jones. The stratigraphical succession and the 

 geological structure of an area lying in the hilly district 

 east of Aberystwyth are dealt with. The rocks within the 

 district are divided into three stages, which are further 

 subdivided into groups and zones. The Plynlimon stage 

 is developed in the northern part of the district, the Pont 

 Erwyd stage along the two valleys of the Rheidol and the 

 Castell, while the Ystwyth stage is developed on the 

 plateau-like tract extending from the Castell Valley to the 

 Ystwyth Valley. The palaiontological evidence is in entire 

 accord with the stratigraphical evidence. Three types of 

 structure are dealt with, (i) folding, (2) strike-faulting, 

 and (3) normal faulting, but the first is predominant. 

 Evidence is given for assigning to the " Aberystwyth 

 Grits " of earlier observers a position much higher in the 

 geological sequence than has hitherto been attributed to 

 them. The paper concludes with a tabular list of fossils, 

 correlation tables, and a description of two species of 

 graptolites of zonal importance. — ^The geology of the 

 neighbourhood of Seaford (Sussex) : J. V. Elsden. This 

 paper deals with a portion of the South Downs lying 

 between Eastbourne and Ncwhaven. The inland outcrops 

 of the uppermost zones of the Chalk are mapped. On the 

 east of the Cuckmere River, the beds examined are found 

 to be nearly horizontal. On the west side they are bent 

 into a sharp uniclinal fold, striking east and west. Sea- 

 ford Head represents a remnant of this fold. The low 

 ground between Seaford and Chyngton occupies the trough 

 of the fold. The complete disappearance of the fold on 

 crossing the Cuckmere cannot be satisfactorily explained 

 by the normal process of dying-out. It is suggested that 

 a transverse fault may exist beneath the alluvium of that 

 river. The fault, if it e.xists, seems to die away north- 

 wards, since no trace of it has been detected higher up 

 the valley. The relation of the Seaford fold to the main 

 flexures of the south coast is considered. Certain exist- 

 ing physiographical features are ascribed to the influence 

 of this flexure, which facilitated the retention of the Eocene 

 cover in the synclinal hollow thus formed. A brief com- 

 parison is made between the fossils of the inland exposures 

 and those of the rliff-soction, the most notable difference 

 being the evidence in the former of a Conulus band at the 

 top of the zone of Micraslcr cor-anguiiium. 



Physical Society, Mav 14. — Dr. C. Chree, F.R.S., presi- 

 dent, in the chair. — A bifilar vibration galvanometer : \V. 

 Duddell. The paper describes a new type of vibration 

 galvanometer and a series of tests made upon it. Vibra- 

 tion galvanometers may be divided into two types : — 

 (i) those in which the moving part consists of a piece of 

 iron or steel, and the current to be measured flows round 

 fi.xed coils, as in the case of the Thomson galvanometer ; 

 (2) those in which the current to be measured flows round 

 -a moving coil placed in a fixed magnetic field, on the 

 syphon recorder principle. The vibration galvanometers of 

 Max Wien and Rubens belong to the first class, while Mr. 

 Campbell's vibration galvanometer and the one described 

 in the paper belong to the second. In the instrument 

 described the mass of the moving parts is reduced to a 

 minimum, the moving coil being reduced to the two wires 

 forming its two sides, similar to a bifilar oscillograph, but 

 with this difference : whereas the bifilar oscillograph is 

 designed so as to make the damping aperiodic, the vibra- 

 tion galvanometer is designed so as to keep the damping 

 as small as possible. .^ series of tests made upon the 

 instrument showed that the total range of frequency was 

 very large, namely, from about 90 ~ per second up to 

 igoo •- per second. The damping is verv small, .so that 

 the resonance is very sharp. — Effect of temperature on the 

 hysteresis loss in iron in a rotating field : W. P. Fuller 

 and H. Grace. The rotating field was produced by means 

 of 'two phase currents. One phase was connected to a 

 coil of long rectangular section and of sufficient length to 

 produce a uniform field within a radius of 2 cm. from 



NO. 2066, VOL. Sol 



the centre. The second phase was connected to a similar 

 coil enclosing this one, and causing a flux at right angles 

 to it. The resultant field at the centre was uniformly 

 rotating. The results of the experiment show that the 

 effect of increasing the temperature of iron is to reduce 

 the hysteresis loss at a given induction and to cause the 

 maximum loss to occur at a lower value of the induction. 

 In one specimen the ma.ximum value of the loss at 220° C. 

 was 12,300 ergs per cu. cm. per cycle at an induction 

 of 16,000 C.G.S. units.. At 580° C. the maximum loss was 

 2600 ergs at an induction of 10,700. The frequency of 

 the experiments was 42 cycles per sec. — A method of 

 testing photographic shutters : A. Campbell and T. 

 Smith. The authors described a simple and rapid method 

 of testing the speeds and efficiencies of photographic 

 shutters, with a maximum error of ooooi second at the 

 highest speeds. A vibrating beam of light falling through 

 a narrow slit on to a moving plate serves to measure the 

 time. This beam is obtained by reflecting the light of a 

 Nernst lamp from the mirror (area 50 sq. mm.) of a 

 vibration galvanometer actuated by a current of fixed fre- 

 quency (say 100 or 500 -^ per sec.) obtained from a micro- 

 phone hummer. The use of the vibration galvanometer, 

 in which the amplitude is enormously increased by reson- 

 ance, greatly facilitates the measurements. When the 

 total duration of exposure only is required, the vibrating 

 beam of light is passed through the shutter, tracing a sine 

 curve on the moving plate. The duration of exposure is 

 immediately found by counting the number of ripples re- 

 corded on the plate. Ten records of the various speeds of 

 a shutter can be taken side by side on one 5X4 in. plate in 

 one minute. When the efficiency in addition to the dura- 

 tion of exposure is required, the method adopted is 

 essentially that of Sir Wm. Abney, but the time measure- 

 ments are made with the vibrating beam of light instead 

 of a screen. 



Zoological Society. May 25. — Dr. S. F. Harmer, 

 F.R.S., vice-president, in the chair. — The anatomy of the 

 olfactory organ of teleostean fishes : R. H. Burne. The 

 chief structural variations were described in some fifty 

 genera,, mostly of common British species, the anatomical 

 facts being illustrated by a series of coloured diagrams. — 

 Description of a new species of the decapod crust.icean 

 genus .Mpheus, Fabr., from the Bay of Batavia : 

 Dr. J. G. de Man. 



C.-VMBRIDGE. 



Philosophical Society. May 3. — Mr. H. F. Newall in 

 the chair. — A specimen of the cone Calamostachys binne- 

 yana, Carruthers : H. H. Thomas. — Note on two -new 

 ieeches from Ceylon : W. A. Harding:. The leeches 

 described in this paper were collected in Ceylon by Miss 

 Muriel Robertson. The material comprised examples of 

 two species hitherto unrecorded, of which a brief descrip- 

 tion is given. — Note on an abnormal pair of appendages in 

 Lithobius : L. Doncaster. — A property of summable func- 

 tions : Dr. A. C. Dixon. 



May 17. — Sir J. J. Thomson, vice-president, in the 

 chair. — Phenomena of X-ray transmission : C. G. 

 Barkla. By the use of homogeneous beams of X-rays 

 the author 'investigated the variations in the relative 

 ionisations in different gases due to changes in the 

 penetrating power of the primary beams used. It was 

 found that as the primary radiation passing through a 

 gas was made more penetrating, within well-defined limits, 

 the ionisation in that gas was approxiinately proportional 

 to the ionisation produced by the same beam in air. 

 ^Vhen, however, the primary beam became just more 

 penetrating than the secondary homogeneous radiation 

 characteristic of one of the elements in the gas, the 

 ionisation in that gas increased rapidly. The connection 

 between ionisation in the gas, intensity of secondary radia- 

 tion from the elements in the gas, and the absorption of 

 the primary rays in those elements was exhibited. It was 

 shown that the apparent irregularities recorded by many 

 investigators in the various phenomena of X-ray trans- 

 mission — absorption, secondary radiation, ionisation — may 

 be explained in terms of a few simple laws. — Phenomena 

 of the kathode discharge : J. A. Orangre. The paper 

 deals with the phenomena of the Crookes's dark space. 



