June ig, 1913] 



NATURE 



4*5 



Royal Astronomical Society, June 13. — Major E. H. 

 Hills, C.M.G., F.R.S., president, in "the chair. — F. W. 

 Dyson and E. W. Maunder : Position of the sun's axis as 

 determined from photographs of the sun from 1874 

 to 1912, measured at the Royal Observatory, Green- 

 wich. In a previous paper corrections to the position 

 of the axis were deduced from observations of spots 

 crossing the sun's disc; in the present paper the 

 material employed was extended by the consideration 

 of spot groups passing across the further side of the 

 sun. A still more important addition consisted in the 

 observation of the latitudes of spots near the centre 

 of the disc. No change was observed, either with 

 sun-spot cycle or with phase. — A. S. Eddington : Pre- 

 liminary results of observations with the Cookson 

 floating zenith telescope. Mr. Cookson had photo- 

 graphed trails of the same star with reversed posi- 

 tions of the instrument; at Greenwich trails of 

 different stars were taken, a method which brings 

 the trails closer together, and near the centre of the 

 plate. This method considerably reduced the probable 

 error, but there remained discordances, the cause of 

 which was uncertain ; there seemed reason to believe 

 that they were atmospheric. — J. A. Harker : The origin 

 of solar electricitv. A simple apparatus was described 

 with which experiments were made, showing increase 

 of electrical emission in all metals with increasing 

 t< mperature. The cosmical bearing of the phenomena 

 observed was pointed out. — Prof. E. C. Pickering : 

 Some work carried on at the Harvard Observatory, 

 especially the classification of stellar spectra by Miss 

 Cannon. One thousand spectra had been classified by 

 Miss Cannon alone in three years, but with her great 

 experience and bv carefully organising the work, Miss 

 Cannon and her staff of assistants were now able to 

 classify 5000 spectra a month. The work to be done 

 was very great ; there appeared to be more than 

 150,000 spectra to be dealt with. — Miss Cannon : 

 Classification of spectra of traseous nebula?. Many 

 gaseous nebulae have precisely the character of the 

 spectra of stars of the fifth type. — S. S. Hough : Pro- 

 gress of the Cape of Good Hope share in the work of 

 the Astrographic Chart. The catalogue plates were 

 all taken and checked by comparing the overlapping 

 quadrants. Mr. Hough described briefly the other 

 work carried on at the Cape, especially mentioning 

 the high degree of stability of the system of meridian 

 marks used. — Dr. H. N. Russell : Studies of stellar 

 evolution, carried on at the Princeton Observatory. 

 Dr. Russell showed diagrams exhibiting the relation 

 between the spectra of stars and their real brightness, 

 that is the brightness which they would have if all 

 were placed at a uniform distance corresponding to a 

 parallax of ten seconds. Interesting relations between 

 colour and brightness were shown by the diagrams. 



Cambridge. 

 Philosophical Society, May iq. — Dr. Shipley, presi- 

 dent, in the chair. — Dr. G. F. C. Searle : (1) Some 

 methods of measuring the surface tension of soap 

 films. In one method the pressure excess due to a 

 curved soap film is measured by aid of what may be 

 called a "viscosity potentiometer." Air from a gaso- 

 meter flows through two tubes AB, BC in series. 

 The pressure at A is measured by a manometer ; the 

 end C is open to the air. From the junction B a 

 side tube leads to a cup with a horizontal circular rim 

 on which a soap film is placed. On account of the 

 viscosity of the air, there is a fall of pressure along 

 each tube. For a given flow of air, the fall of pressure 

 in either tube is proportional to the length of the tube, 

 and inversely proportional to the fourth power of its 

 internal radius. The excess of the pressure at B over 

 that of the atmosphere causes the film to become 

 part of a sphere. From the distance of the highest 



NO. 2277. VOL. 91I 



point of the film above the plane of the rim and from 

 the radius of the rim, the radius, r, of the film can l»- 

 computed. (2) A simple method of testing lens 

 systems for aberration. On account of spherical 

 aberration, a lens does not bring to a mathematical 

 point all the rays which have reached it from an object 

 point on its axis. When there is aberration, the 

 emergent beam has at one place a finite minimum 

 cross section called the least circle of aberration ; the 

 smaller this circle is the more nearly is the lens free 

 from spherical aberration for the given position of the 

 object point. A metal plate is pierced with three 

 equally spaced circular holes, A, B, C, each about 

 01 cm. in diameter, and the distance AC (measured 

 from centre to centre) is about 2 cm. The holes are 

 illuminated by a flame and their " images " formed 

 by the lens system under test are' received upon a very 

 fine ground-glass screen backed by a micrometer scale 

 divided to 001 cm. ; this scale is viewed by an eyepiece. 

 The examination shows whether the lens is free from 

 spherical aberration or whether it is (1) under-corrected 

 or (2) over-corrected for aberration. — R. D. Kleeman : 

 The unstable nature of the ion in a gas. The ions in 

 a gas in thermodynamical equilibrium must at any 

 instant consist of free ions and clusters of various 

 complexities (Proc. Camb. Phil. Soc, vol. xvi., pt. iy., 

 p. 285). In order to obtain some experimental in- 

 formation on the nature of the ions, the ionisation by 

 collision between a gauze and plate was studied, the 

 initial ions being formed outside the space between 

 gauze and plate in a weak field which drew the ions 

 Through the gauze. Some of the elementary ions 

 were thus able to form clusters before being seized 

 upon by the strong field producing further ions by 

 collision.— W. A. Douglas Rudge : A dust electrical 

 machine. The author has shown that clouds of dust 

 raised by the wind or by artificial means are always 

 stronglv' charged with electricity, the sign of the 

 charge depending upon the nature of the dust. By 

 a suitable arrangement of apparatus it is possible to 

 get a continuous supply of electricity, by directing a 

 current of air laden with dust through an insulated 

 tube. When the current is passing a stream of 

 sparks, sometimes 6 cm. in length, may be obtained 

 from the tube. Flour, sulphur, road dust, or fine 

 iron filings may be used. The air which escapes 

 from the exit tube of the apparatus is also strongly 

 charged, and if the apparatus is used inside a room 

 the charge may be retained by the air of _ the room 

 for more than half an hour. The origin of the 

 charge upon the apparatus is probably due to (1) the 

 actual raising of the cloud, (2) friction of the dust 

 against the 'walls of the tube.— R. Whiddington : A 

 mechanical vacuum tube regulator. One of _ the 

 devices for regulating the speed of kathode rays within 

 a discharge tube is to provide the kathode with a 

 movable glass sheath. The position of the sheath 

 determines the speed of the rays. Experiments are 

 described which show that the inside of the sliding 

 sheath concentrates the cylindrical beam of rays to 

 a fine beam, thus diminishing the effective size of the 

 kathode. 



Edinburgh. 



Royal Society, Mav 4.— Sir William Turner, K.C.B., 

 president, in the chair.— Dr. W. S. Bruce : The skulls 

 of antarctic seals (Scottish National Antarctic Expedi- 

 tion). The paper contained the measurements of the 

 skulls of the different seals found in the Antarctic, 

 with careful photographs of the skulls in various 

 aspects.— Miss Laura R. Thornley ; The Bryozoa of 

 the Scottish National Antarctic Expedition. Of the 

 eiq-hty-five species described, three were new to science 

 and six of the remainder had been found in the 

 southern seas for the first time. — W. Watson : The 



