502 



NATURE 



[March 26, 1896 



skulls found at Girton in 1881, by R. Horton-Smith.— On 

 some scratched stones from the Permo-Carboniferious rocks of 

 South-east Australia and the bearing of the evidence on the 

 question of recurring Ice Ages, by Prof. Hughes. Prof. Hughes 

 exhibited some specimens and photographs given to him by 

 Prof. David of the University of Sydney, pointing out that the 

 glaciation of South Australia as generally understood had been 

 entirely disproved ; that there had been no glaciers in the dis- 

 trict in question, but that the traces of glaciation were due to ice 

 floating from the south over a subsiding area, with, as he 

 inferred, a compensating elevation elsewhere. He gave a 

 risiimi of the new evidence which he had collected in favour of 

 the view that the recurrence of local glacial conditions was 

 always connected with movements of elevation and depression, 

 and appealed to physicists to explain the overthrusts and con- 

 tortions of the surface of the earth, not solely by shrinkage of 

 the nucleus nor by deformation of the whole mass, but by some 

 conditions affecting regions limited in extent and depth, with 

 perhaps a certain amount of periodicity determined by some 

 more general cosmical causes. — On some chipped flints from the 

 higher plateau gravel of Salisbury, by Prof. Hughes. Prof. 

 Hughes criticised the evidence which had been adduced in 

 favour of the discovery of man older than the Palaeolithic Age, 

 exhibiting in illustration a collection of so-called Palaeotoliths 

 from the plateau gravels near Salisbury, from the stony surface 

 between Six-Mile Bottom and Balsham, and from Kent. As far 

 as he had seen, no satisfactory evidence had been adduced in 

 favour of the higher antiquity assigned, in the case of any of the 

 flints which could be said to bear marks of design. — On the 

 leakage of electricity through dielectrics traversed by Rontgen 

 rays, by Prof. J. J. Thomson and Mr. J. A. McClelland. This 

 paper contains an account of a series of experiments made with 

 the object of investigating the laws regulating the passage of 

 electricity through dielectrics transmitting Rontgen rays. This 

 phenomenon has been discussed by one of the authors in a paper 

 read before the Philosophical Society on January 27, and also 

 in one read before the Royal Society on February 13. The 

 first experiments relate to the rate of leak through different 

 gases under similar conditions as to pressure and potential 

 gradient. The gases used were hydrogen, ammonia, carbonic 

 acid, air, coal gas, sulphuretted hydrogen, chloroform, chlorine, 

 bromine, iodine, sulphur chloride and mercury vapour. Num- 

 bers showing the rate of leakage in these gases relatively to that 

 in air are given. In general, though the rule is not without 

 exceptions, the greater the molecular weight of the gas the more 

 rapid the leakage. In hydrogen the leak was slowest, and in 

 mercury vapour fastest ; the rate in the vapour of boiling mercury 

 was about twenty-eight times as fast as hydrogen. The rapid rate 

 in mercury vapour is interesting, for this gas offers great opposi- 

 tion to the passage of an ordinary electric discharge. The rate 

 of leak in the halogens is also very rapid, and a tube containing 

 a charged plate in chlorine gas is a very sensitive and convenient 

 method of measuring the intensity of these rays. The rates of 

 leakage in air at different pressures were investigated ; it was 

 found that the rate of leak was slower at a low pressure than at a 

 high one, and was over a considerable range of pressure approxi- 

 mately proportional to the square root of the pressure. The effect 

 of temperature was also investigated, and it was found that through 

 air the rate of leak was slower at a very high temperature than 

 at the temperature of the room, but there was an intermediate 

 temperature at which the rate was a maximum. The most re- 

 markable thing about this leakage under the influence of these rays 

 is that the rate is almost independent of the potential difference. 

 Thus when the high potential plate was 5 volts above that of 

 the low, the rate of leak was appreciably greater than when the 

 potential difference was i volt, but the rate was no greater when 

 the potential difference was 500 volts than when it was 5. A 

 series of experiments were made to find how the rate of leakage 

 varied with the distance from the bulb ; the bulb was placed 

 behind a metal plate with a hole in it : it was found that in the 

 neighbourhood of the phosphorescent glass the reciprocal of the 

 rate of leakage was a linear function of the distance from the 

 phosphorescent patch, but at greater distances it diminished 

 more rapidly than is indicated by this law. The measurements 

 are not inconsistent with the view that the rate varies inversely 

 as the square of the distance from a place in the neighbourhood 

 of the negative electrode. Some experiments on the rate of 

 leakage produced by the rays after passing through a varying 

 number of strips of tinfoil seem to indicate that these rays are 

 not all of one kind. 



NO. 1378, VOL. 53] 



Dublin. 



Royal Dublin Society, January 24.— Prof. George F. 

 Fitzgerald, F.R.S., in the chair. — The following papers were 

 read : — On carborundum, a substitute for emery, by Dr. Charles 

 E. Fitzgerald ; some remarks on difficulties of meridian circle 

 work, by Mr. Arthur E. Lyster ; a method of using common 

 petroleum as the illuminant for beacons and buoys, by which a 

 continuous light for weeks or months may be maintaine<l day and 

 night, without the necessity for the attendance of a light-keeper, 

 by Mr. John R. Wigham At this meeting. Prof. D. J. 

 Cunningham, F.R.S., exhibited and described puppies of the 

 Cape hunting dog {Lycaon pictiis), preserved in spirit. The 

 animals were born in the Royal Zoological Gardens, Dublin. — 

 Mr. Richard J. Moss described acetylene, the new illuminant. 



February 19.— Prof. G. F. Fitzgerald in the chair.— The fol- 

 lowing two papers were read : — On Hamilton's singular points 

 and planes on Fresnel's wave-surface, by Prof. William Booth, of 

 Hoogley College, Bengal, communicated by Prof. Thomas 

 Preston ; on the continuity of transformation from the liquid to 

 the gaseous state, by Prof. Thomas Preston. — There were 

 exhibited at this meeting the Lenard-Rontgen X-rays, and their 

 properties were described by Dr. J. Joly, F.R.S., photographic 

 results being exhibited by Dr. Joly, Mr. W. E. Wilson, and 

 Mr. Richard J. Moss. 



Philadelphia. 



Academy of Natural Sciences, February 25.— Papers 

 under the following titles were presented for publication : "The 

 Colouring Matter of the Axil of Celastrus scaiidens,'" by Ida A. 

 Killer; "The Crystallisation of Molybdenite," by Amos P. 

 Brown. The Anthropological Section having precedence. Dr. 

 D. G. Brinton made a communication on the use of the cranio- 

 facial line in determining racial and individual characters on the 

 living subject. The relation of the diameters of the cranium 

 formerly relied on had been found unsatisfactory. He specially 

 recommended a line closely resembling that suggested by the 

 sculptor Charles Rochet. It connects the two auditory foramina, 

 forming a slight curve, the superior border of which connects 

 the internal commissures of the eyes. This line, it is claimed, 

 divides the ideal, normal head into two perfectly equal parts, 

 although in nature, of course, this proportion is not maintained, 

 but varies as a racial character and in individuals. The relations 

 of the lines may also indicate the cranial capacity, as the plane 

 of the curve continued posteriorly is approximately the base of 

 the skull. He further pointed out that the distance between the 

 distal extremities of the curve gives the width of the head and 

 the face ; and that a series of curves, described from the 

 fixed points indicated, offers, probably, the simplest and most 

 accurate method of obtaining significant head-measures on the 

 living subject.— -Dr. Harrison Allen commented on the difficulty 

 of obtaining satisfactory cranial measurements, and referred 

 to Oldfield Thomas's, taken from the outer margin of the orbits 

 to determine the projection of the nose. He did not think the 

 true horizontal plane of the skull could be fixed. The so-called 

 Frankfurt plane is the one most commonly accepted. — Dr. 

 Seneca Egbert stated that he had demonstrated the action of the 

 X-rays through plates of platinum from ordinary sunlight. 

 Illustrative pictures were exhibited, and the published results of 

 other experimenters were discussed. — Prof. Maxwell Summer- 

 ville exhibited beautiful specimens of chipped arrow-heads made 

 from common green bottle-glass by the natives of North-western 

 Australia. He also called attention to a stone carved to resemble 

 a miniature grotesque head, from the valley of the Delaware, 

 opposite Milford, and an object used in phallic worship by the 

 natives of Poonah, India. — Dr. D. G. Brinton called attention 

 to the importance of obtaining systematic data for the study of 

 American anthropology, and suggested the wide distribution, 

 under the auspices of the Anthropological Section of the Academy, 

 of circulars of inquiry, similar to those in use by the Committee 

 appointed by the British Association for the Advancement of 

 Science for the study of the ethnography of Great Britain. 



March 3. — Messrs. Morris E. Leeds and J. S. Stokes, on 

 behalf of Messrs. Queen and Co., made communications 

 on the historical development of studies in connection with 

 Rontgen photography, presented the most advanced views 

 as to the nature of the X-rays as published by various 

 investigators. They also exhibited a .series of fine pictures 

 illustrating the application of the process to the study of 

 biology, and the results obtained by the use of quick and slow 

 plates and various developers. Dr. Egbert having alluded to 



