May 30, 19 1 8] 



NATURE 



259 



SOCIETIES AND ACADEMIES. 

 London. 

 Optical Society, May 9.— Mr. S. D. Chalmers in 

 the chair.— T. Y. Baker and Major L. N. G. 

 FUon : Spherical aberration. The authors had con- 

 sidered the subject from the point of view of an optical 

 design for a system of co-axial thin lenses (separated 

 by air) in which the focal lengths and separations of 

 lenses are determined from general consideration of 

 the functions that the instrument has to perform, and 

 from the necessity for correcting for colour. A design 

 carried out in this manner leaves available for the 

 correction of spherical aberration the forms of the 

 various lenses. For a thin lens of definite focal 

 length made of a definite variety of glass the differ- 

 ence of curvature of the two faces of the lens is fixed, 

 but the mean of these two curvatures is arbitrary! 

 I When aberrations of the second order have to be 

 I included, the semi-cubical parabola is no longer a 

 ' sufficiently close approximation to the caustic, which, 

 in general, develops two new cusps off the axis. The 

 general appearance of such a caustic was examined, 

 as well as the possibility of deriving the two para- 

 meters from trigonometrically calculated rays. The 

 authors urged that the full import of the higher-order 

 aberrations could best be understood by an actual 

 construction of the caustic in the several media, from 

 which the trained optical calculator would be able to 

 tell from the shapes of the successive curves how the 

 aberrations of different orders would affect the final 

 image formation, and also to form an idea as to 

 which lenses were having most serious effect, and 

 how changes in the forms of the lenses would enable 

 him to diminish the spherical aberration of the final 

 image. 



Pi\RIS. 



Academy of Sciences, May 13.— M. Leon Guignard 

 in the chair.— G. Humbert : The indefinite quadratic 

 forms of Hermite.— J. Boussinesq : Further studies on 

 the rupture of a sandy terrc-plein. — H. Le Chatelier and 

 B. Bogitch : The action of oxide of iron on silica. 

 An experimental study of the penetration of silica 

 bricks b\' oxide of iron. The iron penetrates more 

 easily in a reducing atmosphere, the portions reached 

 by the iron oxide contain less lime than the original 

 brick, whereas the part of the brick not attacked bv 

 the iron oxide contains more lime than originally, the 

 lime being expelled by the ferrous silicate and driven 

 into the upper part of the brick. Four reproductions 

 of photomicrographs are given, showing the condition 

 of various zones of silica brick impregnated bv oxide 

 of iron. — G. Julia: Limiting values of Poisson's 

 integral relating to the sphere and a point of dis- 

 continuity of the data.— E. Belot : The role of the 

 forces dominating the attraction in the architecture 

 of the earth and other worlds. Mechanical model of 

 the formation of the solar system. — M. Bied : The 

 function of the oxide of iron and lime employed as 

 agglomerants in the manufacture of silica bricks. In 

 studying the effect of different agglomerating materials 

 in the manufacture of silica bricks an unexpected fact 

 was elicited that appreciable quantities of oxide of 

 iron, even in the presence of lime, do not appreciably 

 lower the meeting point of the brick. Further ex- 

 periments on this question are now given in confirma- 

 tion. In one case the addition of 3 per cent, of 

 oxide of iron and i oer cent, of lirne lowered the 

 fusion point only by 5^ C., an amount not exceeding 

 the experimental error. — E. Rengade : The composi- 

 tion of silica bricks taken from a Martin furnace.— 

 Ed. Clianvenet and Mile. L. Nicolle : The neutral 

 zirconyl nitrate. There is no evidence of the existence 

 of anhydrous or hydrated neutral zirconium nitrate. 

 NO. 2535, VOL. JOl] 



The hydrated zirconyl nitrate, ZrO(N03)j,2HjO, can 

 be obtained as a crystalline product, but the anhydrous 

 zirconyl nitrate could not be prepared from this. — 

 M. de Ciiardonnet : Treatment of the wash waters in 

 the manufacture of artificial silk. There are about 

 4 cubic metres of washing water (containing sulphuric 

 and nitric acids, lime, and sulphur) per kilogram of 

 silk produced, and it is necessary to neutralise this 

 liquid before it can be run into drains or rivers. An 

 arrangement is described for neutralisation .with lime 

 and removal of the precipitated sulphur. The liquors 

 after neutralisation have marked manurial properties. 

 — M. M. Ydlenko: Results of studies on the earth- 

 quake of August and September, 1912, on the Sea of 

 Marmora.— C. Sauvageau : The plantules of Phyllaria 

 reniformis.—E. Voisenet : Is the Adamkiewicz reaction 

 due to glyoxylic acid or to formaldehyde? Hopkins 

 and Cole showed that the use of acetic acid in the 

 Adamkiewicz reaction introduced a substance neces- 

 sary to the production of the violet colour, and con- 

 sidered this to be glyoxylic acid. They considered the 

 possibility of formaldehyde as the necessary reagent 

 and rejected it. The author takes the opposite view, 

 and regards formaldehyde, and not glyoxylic acid, as 

 the -essential reagent. 



Calcutta. 

 Asiatic Society of Bengal, April 3. — Dr. T. Kaburaki : 



Zoological results of a tour in the Far East. Brackish- 

 water Polyclads. The Polyclads described in this 

 paper were obtained in biackish water in the north- 

 eastern part of the Malay Peninsula. They belong to 

 the genus Shelfordia, which has hitherto been known 

 only from Borneo. It is the only genus of Polyclads 

 that has been found in fresh water. Two new species 

 are described. — Dr. N. Annandale : Zoological results 

 of a tour in the Far East. MoUu-sca of the Tai-Hu. 

 The Tai-Hu is a large, shallow body of fresh water 

 occupying a depression in the alluvium of the Yangtse 

 delta. Seventeen species of molluscs, of which three 

 (all belonging to the family Hydrobiidae) are now 

 described as new, are recorded from it. One of the 

 new forms belongs to the genus Hypsobia, Heude 

 (which has recently been re-des'cribed by Robson under 

 the name Katayama), another to Stenothyra, Benson, 

 and a third to a remarkable new genus hitherto ap- 

 parently confused with Vivipara, though actually 

 belonging to a different family. The Tai-Hu mol- 

 luscan fauna as a whole is remarkable for the small 

 size of the individual and for the existence of an 

 estuarine element in its composition. — Dr. N. Annan- 

 dale : Zoological results of a tour in the Far East. 

 Sponges, (i) Two marine sponges {Reniera iinplexa 

 and a new variety of Amorphinopsis excavans) were 

 found on the piers of a landing-stage some distance 

 up a creek on the coast of Perak. They lived in very 

 muddy water, and were exposed daily at the fall of 

 the tide. The structural peculiarities which enabled 

 them to exist in these conditions are discussed in 

 detail. (2) Specimens of fresh-water sponges collected 

 in Japan, China, and the Malay Peninsula are dis- 

 cussed and described. Thev include new species of 

 Spongilla and TrochospongiUa.— Capt. F. de Mello and 

 Dr. J. F. St. \. Fernandes : Revision des champignons 

 appartenant au genre Nocardia. In this paper the 

 authors give a synoptical account of the numerous 

 species of parasitic fungi belonging to the genus 

 Nocardia. Our knowledge of these forms is at present ' 

 in an extremely chaotic state, and the authors have 

 attempted to introduce oider and precision into the 

 classification.— C. Fischer : Preliminary note on the 

 flora of the Anaimalais. (i) General description of the 

 tract ; (ii) faunistic notes ; (iii) jungle tribes and their 

 cultivations ; (iv) division of the vegttation into five 



