August 14, 19 13] 



NATURE 



627 



mittee was chiefly concerned with the needs of the 

 children. The intensity of illumination necessary in 

 schoolrooms depends on the nature of the work car- 

 ried out. It is suggested that for ordinary clerical 

 work the minimum illumination measured at any desk 

 whi re the light is required should not fall below, 

 2 foot-candles — four members of the committee say 

 2J foot-candles. For special work, such as stitching 

 with dark materials or that in art classes, a minimum 

 of 4 foot-candles is desirable; and for general illu- 

 mination in assembly-rooms one foot-candle. As re- 

 gards blackboard lighting, the committee recommends 

 an illumination on "the blackboard about 60 per cent, 

 in excess of that prevailing in the rest of the room. 

 To avoid glare it is recommended that no lamps 

 should come within the solid angle subtended at the 

 eye by the blackboard, and a space 2 ft. above it, 

 unless they are completely screened from the eye by 

 a shade impervious to light. With the same object 

 it is suggested that for text-books intended for the 

 use of young children matt paper, sensibly free from 

 prejudicial reflection, should be employed. The use 

 of light-tinted surroundings which serve to diffuse the 

 light is recommended to avoid inconvenient shadows. 



SOCIETIES AND ACADEMIES. 



Manchester. 

 Literary and Philosophical Society, July 22. — Dr. H. 

 Wilde : Some new multiple relations of the atomic 

 weights of elementary substances, and the classifica- 

 tion and transformations of neon and helium. In 

 several of the author's papers on the origin of elemen- 

 tary substances, published by the society (1878-1906), 

 special attention was directed to the seventh series of 

 his classification, on account of the magnitude .md 

 importance of its primary members in the economy of 

 nature, viz. nitrogen, silicon, iron, and gold. Silicon 

 in combination with oxygen constitutes more than 

 half the weight of the earth's crust, and is the prin- 

 cipal constituent of glass for all the purposes of 

 civilised life. The policy of several writers in doubling 

 the atomic weights of four of the gaseous members 

 of this series, viz. neon, argon, krypton, and xenon, 

 induced the author to review the multiple relations of 

 the seventh series with the important result (1) that six 

 triads are formed out of the eight principal members 

 of the series, in which the sum of the atomic weights 

 of the extreme members is double the atomic weight 

 of the means, and are all multiples of seven. Triads 

 of atomic weights have been fully recognised by 

 Dumas, Faraday, and other philosophical chemists, as 

 indubitable evidence of community of origin, of trans- 

 mutation, and important factors in the classification 

 of elementary substances. Radium i(as was indicated 

 in Dr. Wilde's tables of elements some years previous 

 to its discovery) is one of the synthetic transforma- 

 tions of helium, and is the next higher member of the 

 series to barium, as was since confirmed by Mme. 

 Curie. Helium is also shown in the author's table 

 of 1878 as the analytic transformation ultimate of 

 radium and other members of the second series of 

 elements. The positions of helium and neon, as the 

 transformation ultimates of the second and seventh 

 series respectively, are further interesting in connec- 

 tion with the recent announcements that these elements 

 have been found in glass vessels and tubes in which 

 they had no previous existence. Assuming the reality 

 of these observations, the phenomena not only admit 

 of explication from Dr. Wilde's classifications, but 

 also account for the discordant results obtained by 

 the experimenters engaged in the research. One of 

 the investigators could onlv find neon, while others, 

 working independently, found helium alone, and in 

 NO. 2285, VOL. qi] 



other cases a mixture of both gases. These results 

 were of sufficient interest to induce the author to 

 ascertain the composition of various glasses used in 

 the arts. The principal and most important consti- 

 tuent of the glasses tabulated by Dr. Wilde is silicon, 

 the transformation ultimate of which is neon. The 

 next important constituents of the glasses are barium, 

 calcium, and lead, all members of the second series 

 of elements, the transformation ultimate of which is 

 helium. The alkali methods, sodium and potassium, 

 are constituents of nearly all glasses, and their trans- 

 formation ultimates (with others of the first series) 

 will be hydrogen and neon, but without helium. All 

 the silicates of the first and second, and some of other 

 series, are easily vitrified in small quantities in labora- 

 tory crucibles. Their spectra can then be examined 

 during electrification in tubes (under suitable condi- 

 tions of temperature and pressure) for the discovery of 

 new elements and the identification of those already 

 known. 



Paris. 



Academy of Sciences, August 4. — M. F. Guyon in the 

 chair. — J. Boussinesq : The complete determination, by 

 its partial differential equations, of the problem of 

 slow regularised movement of a heavy liquid mass, in 

 the midst of another fluid mass, indefinite and at rest, 

 and equally incompressible.— G. Charpy and A. Cornu : 

 The displacement of the critical points of iron by the 

 addition of silicon. Contradictory results on this sub- 

 ject have recently been published by Vigouroux and 

 Baker. Seven " alloys have been prepared by the 

 authors from Swedish iron to which increasing quan- 

 tities of ferro-silicon were added. Complete analyses 

 are given of the seven alloys, the silicon ranging from 

 o-ii to 6-io per cent. The critical points were deter- 

 mined by the velocity of cooling method, the curves 

 being recorded automatically with the double Saladin- 

 Le Chatelier galvanometer. The point a- 3 vanishes 

 when the silicon reaches 1-5 per cent. The point a, 

 remains clear throughout, but each increase of 1 per 

 cent, of silicon lowers the temperature by about 11° C. 

 The temperature of a, is slightly raised as the propor- 

 tion of silicon increases, and tends to disappear when 

 the silicon is more than 5 per cent. — Paul Vuillemin : 

 The greening of the wood of the pear-tree. The 

 wood is rendered green by Helotium aeruginosum and 

 H. aeruginascens, the two species differing in the 

 size of the spores. The name of Chlorosplenium is 

 without systematic value, since several genera have 

 been described under this name which are not closely 

 allied. The colour of the wood is retained indefinitely 

 and has been utilised in the arts.— R. Gateaux :. Con- 

 tinued and analytical functionals.— Jules Andrade : The 

 law of similitude of circular springs.— J Rey : A 

 method of testing optical reflectors. The proposed 

 method, which is applicable to all optical systems 

 giving a real or virtual image of a luminous point 

 placed at its focus, is based on a photograph of the 

 image of square mesh wire gauze. The photograph 

 shows not onlv that there is an imperfection of the 

 surface, but gives the points of the surface the curva- 

 ture of which is incorrect. Two reproductions of 

 such photographs accompany the paper. — MM. Massol 

 and Faucon : The absorption of the ultra-violet radia- 

 tions by some mineral colouring matters in aqueous 

 solution. The various colouring matters studied 

 (potassium ferrocyanide, gold chloride, sulphate of 

 copper, potassium chromate, uranium nitrate, nickel 

 sulphate, chromium sulphate) absorb the ultra-violet 

 radiations unequally. From a quantitative point of 

 view, the absorbing power of synthetic organic colour- 

 ing matters is much greater than that of the mineral 

 colours.— Daniel Berthelot and Henry Gaudechon : The 

 rdle of uranium salts as photochemical catalysts. 



