March 23, 1876J 



NATURE 



419 



business of the Society, Dr. J. H. Gladstone rose and in a short 

 speech proposed a vote of thanks to the president for the exceed- 

 ingly enjoyable visit to tlie Royal Arsenal at Woolwich on the 

 preceding Tuesday, and for his generous hospitality on that occa- 

 sion. This was seconded by Dr. Gilbert and carried by accla- 

 mation. The following papers were then read : — On crystailosed 

 glycerin, by Dr. P. F. van Hamel Ross ; notes on the fatty acids 

 and on a suggested application of photography, by Mr. W. H. 

 Hatcher, — On stibine, by Mr. F. Jones. — On the use of platinum 

 in the ultimate analysis of carbon compounds, by Mr. F. Kopfer ; 

 — and on the action of organic acids and their anhydrides on the 

 natural alicaloids, Part v., by Mr. G. H. Beckett and Dr. C. N, 

 A. Wright. 



Royal Astronomical Society, March lo. — Mr. Huggins, 

 president, in the chair. — Since the last meeting the Society has 

 received a valuable present of rare books from the hbrary of the 

 late Mr. Sheepshanks. Lord Lindsay has also presented the 

 Society with the sun-spot manuscripts and observations of the 

 late Mr. Carrington, a very valuable series, which has been made 

 use of in determining the present received values of the elements 

 of the position of the sun's axis and the drifts of the solar photo- 

 sphere. — A paper by Dr. Royston Piggott was read on a star- 

 illuminated transit eye-piece. A sheet of glass, on which a thin 

 film of silver is deposited, is placed in the focus of the eye-lens ; 

 transparent lines are drawn on the film, instead of wires, and as 

 the star passes across the lines it is seen to flash out brightly. 

 The film of silver is made sufficiently thin to permit of the star 

 being seen when it is between the lines, but it appears that the 

 lines themselves are only visible, except in the case of very large 

 stars, when the star disc is in transit across a line. Capt. 

 Abney read a paper on photographing the least-refracted end 

 of the solar spectrum. He said that within the last two years 

 many attempts had been made to photograph the ultra-red rays. 

 Dr. Ycgei, in 1874, and more recently Capt. Waterhouse, had 

 made use of aniline dyes in the collodion. They stated that with 

 a red dye the collodion was found to be most sensitive to the red 

 end of the spectrum. He had repeated these experiments, and 

 had obtained only partial success ; he had, however, from con- 

 sidering the chemistry of the question rather than the physical 

 explanation which had been given and which he believed to be 

 a mistake, been led to try other experiments as to mixing gum 

 resins with the collodion, and had obtained a compound which 

 was very sensitive to the long wave-lengths, so that he had been 

 able to obtain distinct traces of the spectrum beyond A. He 

 hoped to continue his experiments and to give a fuller account of 

 them to the Society at a later meeting. — Two papers were read 

 on the proper motion ot the star B. A. C. 793. It appeared 

 from the remarks of the Astronomer Royal and Mr. l5unkin 

 that there is no sufficient evidence to prove that its proper motion 

 has changed during the present century. — Capt. Noble drew 

 attention to a paper by M. Normand on the occultation of stars 

 by the planets as a means of determining the solar parallax. He 

 wished the owners of large telescopes to determine with what 

 degree of accuracy they could observe the occultation of minute 

 stars at the limb of Mars. 



Entomological Society, March i. — Prof. Westwood, presi- 

 dent, in the chair. — Dr. G. Kraatz, President of the German 

 Entomological Society, Berlin, and Mr. Clemens Miiller, of Ber- 

 lin, were elected Foreign Members ; and Mr, O. E. Jansen was 

 elected an Ordinary Member. — Mr. Jenner Weir exhibited two 

 grasshoppers, in an undeveloped state, taken by himself in the 

 Rhone valley, in copula — a peculiarity which had frequently been 

 observed among the Hemiptera. He also exhibited a remarkable 

 moth from Madagascar belonging lo the UraniidcB, bearing a 

 very striking resemblance to a Fapilio, except that it had the 

 antennae of a moth, and the hind wings were destitute of tails. — 

 Mr. E. Y. Western exhibited Coleoptera taken chiefly in Switzer- 

 land. — Mr. W. Arnold Lewis exhibited a specimen of Argynnis 

 Dia taken in England by Mr. Wallace A. Smith. Mr. Smith, 

 who was present at the meeting, stated in answer to various 

 inquiries by the President, that he had taken the specimen in 

 1872 in Worcester Park, and distinctly remembered the capture, 

 as it was the first fritillary he had ever had in his possession, and 

 also that it had never been out of his possession since. — Mr. Bates 

 read a paper from Mr. Trovey Blackmore to Mr. McLachlan 

 stating that he was much interested in observing a notice in the 

 Proceedings of the Society respecting the habits of Cychrus cylin- 

 drtcollis, reported by M. Baudi to feed on snails. He had already 

 called attention (in the Entomologist' s Monthly Magazine, vol. xi. 

 p. 214) to the fact that the Carabus sienocepkaltts, Fairm., fed on 



snails, which in Morocco were so very abundant as to form a 

 marked feature in the landscape by covering the bushes so thickly 

 as to resemble, at a distance, clusters of blossom. lie had cap- 

 tured in all eighteen specimens of this rare Carabus, and of tlaeac 

 fifteen were obtained either feeding on snails or climbing up 

 bushes of Retama, which were covered with snails, especially 

 with Helix planata. The Carabus having an unusually long 

 head, and the piothorax being narrowed anteriorly enabled it to 

 thrust its head and prothorax a considerable distance into the 

 shell in search of its food. Mr. Blackmore referred to some 

 other North African species of Carabi, which he thought might 

 be found to have similar habits to those of C. stenocephalus. — 

 The President read a paper entitled " A Dipterological|Note from 

 Pompeii," containing remarks on the habits of \!\x&g^VLMS>Bombylius. 

 The President also presented descriptions of some new species 

 of TipulidcE in the British Museum, accompanied by drawings, 

 showing them to be furnished with hind legs of unusiial length. — 

 Mr. John Scott contributed a monograph of the British species 

 belonging to the Htmipiera-Homoptera (family Psyllidai), together 

 with a description of a genus which might be expected, to occur 

 in Britain. 



Physical Society, March 11. — The president, Prof. G. C. 

 Foster, F.R.S., in the chair. — The following candidates were 

 elected members of the society : — W. H. Coffin, T. D. Hum- 

 pidge, and Rev. G. H. Hoj^kins. — Prof. W'. G. Adams gave an 

 account of some researches on which he has been engaged in 

 connection with the influence of light and heat on the electric 

 conductivity of selenium, and exhibited numerous experiments 

 in illtistration. The subject has also been studied by Lieut. 

 Sale and Dr. W. Siemens of Berlin, and as a general result it is 

 found that after it has been kept in the dark, the resistance of 

 the metal is diminished by exposure to light. The effect, how- 

 ever, both of heat and light, is different in the several states 

 through which the metal passes. Thus when a piece ot amor- 

 phous selenium is gradually heated to about 100° C. kept at this 

 temperature and slowly cooled, its resistance at first is so great 

 that it cannot be measured by the ordinary arrangement, but as 

 its temperature increases, the resistance diminishes and increases 

 again more slowly when the metal is allowed to cool. The resist- 

 ance of several pieces which at the higher temperature were firom 

 one to three megohms were found to be from 100 to 130 at the 

 ordinary temperature. If this selenium be placed in a paraffin 

 bath and heated, its resistance diminishes, and when the tempe- 

 rature is kept constant above 140° C. for some hours and the 

 metal is then slowly cooled, it assimaes a crystalline structure, 

 and its resistance diminishes as it cools. The resistaMce of such 

 selenium at ordinary temperatures increases with the temperature. 

 The effect is more marked as the temperature of the paraffin 

 bath is increased. In studying the effect of light, the metal 

 which had been heated to 140" C. was exposed to a candle at 

 distances of I, \, and ^ metre ; the initial resistance being 

 115,500 ohms. The readings in these three cases were 112,000, 

 108,700, and 101,500. Deducting each Irom the initial number 

 we have 3,500, 6,800, and 4,000 ohms as the changes of resist- 

 ance due to exposure at these distances. Hence the effect of 

 light varies inversely as the distance or, what amounts to the 

 same thing, directly as the square root of the illuminating power. 

 These considerations have led Profl Adams to suggest the use of 

 selenium for comparing the iUuminatmg powers of different 

 sources of light, and he exhibited the arrangement which he 

 proposes to use for this purpose. The action of light of different 

 degrees of refrangibihty was then exhibited, by allowing the 

 light from several parts of a spectrum of the electric lamp 

 produced by a bisulphide of carbon prism to fall on the 

 metal, the remainder being cut off by means of a screea, 

 in which there was a narrow slit. Ihe violet light gave a 

 deflection of about two divisions on the screen, the greenish 

 yellow four, the orange red five and a half, and the deep red 

 nine divisions. The effects produced by the greenish yellow 

 and the deep red are at times nearly equal. It may easily 

 be shown by raising the temperature of the metal that the effect 

 of light on its conductivity is essentially the same in kind at a 

 low and moderately high temperature. The tact that light and 

 not dark heat produces the observed effect has been shown by 

 sending the beam through solutions ol iodine in bisulphide of 

 carbon. A very small effect on the metal was always observed, 

 but this may be assumed, to have been due to light, as in all 

 cases it was possible to see the form of the carbon pomts througli 

 the solution. This fact may also be strikingly shown by cxpo::^- 

 ing selenium through which a current is passing to the flame o. 



