January 27, 1910] 



NA TURE 



January ii. — Mr. Francis Jones, president, in the cliair. 

 — Prof. F. E. Weiss : Variability in tlie flowers of 

 Tropjeolum hybrids. A year ago a Tropaeolum was 

 observed by Prof. Weiss which showed at the same period 

 three types of flowers, some yellow, some yellow with red 

 markings, and some completely claret coloured. There 

 seemed no marked periodicity in the occurrence of these 

 flowers in 190S, though sometimes the yellow and pome- 

 times the parti-coloured flowers predominated ; but in an 

 offspring of this plant it was noticeable that the parti- 

 coloured and red flowers occurred only during the fine, 

 hot weather in the second week in August, while during 

 the cold and wet periods of July, September, and October 

 all the flowers were yellow. This indicated a determining 

 influence of temperature and light, and it is borne out by 

 experiments in self-fertilising the variously coloured 

 flowers. In the second (/2) generation a variety of 

 different plants arose by segregation, and the colour of 

 the parental flower had no determining effect, yellow 

 flowers yielding red offspring and vice versa. Incidentally, 

 the segregation of characters in the second (J2) genera- 

 tion showed that in Tropsola, dwarfness is recessive to 

 tallness, as is the case in sweet-peas, and that red sap is 

 a dominant character, though sometimes not apparent 

 owing to unpropitious externa! conditions. This potential 

 redness is, of course, different from the latent condition of 

 a recessive character, which cannot be called into evidence 

 by external conditions. 



DirauN. 



Royal Irish Academy, January 10. — Dr. F. A. Tarleton, 

 president, in the chair. — Sir Robert S. Ball : Contributions 

 to the theory of screws, viz. : — (i) on the expression for 

 the virtual coefficient of two vector-screws ; (2) on the 

 composition of twists or wrenches on vector-screws ; (3) on 

 the pitch operator, 



#1 '^A 



d/>„ 



(4) applications of quaternions to the theory of screws ; 



(5) use of quaternions in the theory of reflected screws ; 



(6) quaternion investigation of the screw reciprocal to five 

 given screws ; (7) representation of screw systems of the 

 third order by linear vector functions. The virtual co- 

 eflficient of two screws a and $ is 



il(/a+/ff) cos 9 -(/sin 61, 



where />a //j are the pitches of the two screws, and d is 

 the length of their common perpendicular. It is here 

 e.xplained how 9 can be measured without any ambiguity 

 when o and ;3 are regarded as vector-screws. The pitch 

 operator A can be applied to any general formula con- 

 necting n screws belonging to an (n— i) system, and by 

 successive application a group of new formulae can some- 

 times be derived. The application of quaternions to the 

 theory of screws is founded on Hamilton's theorem as 

 developed by Joly, that if /i be a vector moment and \ 

 a vector force, then S^/A is the pitch of the screw on 

 which the wrench lies, and V/i/X is the vector perpen- 

 dicular from the origin on the screw. One of the most 

 fundamental theorems in the theory of screws asserts the 

 existence of one screw and, in general, only one screw 

 reciprocal to five given screws. The expression is here 

 given of the vector coordinates of the screw reciprocal to 

 the five screws 



(Ml, X,) ; iii.,, \„) ; {^3, Aj) ; (mj, A4) ! (ft. ^o)- 



This is, as might be expected, a symmetrical form with 

 regard to the five screws, and leads, among many other 

 results, to a concise expression for the sexiant which 

 when equated to zero gives the condition that six screws 

 shall belong to a five-system. Joly showed that Hamilton's 

 beautiful theory of linear vector functions receives its geo- 

 metrical representation by the system of screws of the 

 third order. The fundamental properties of linear vector 

 functions can be explained as immediate consequences of 

 the theory of screws. 



NO. 2100, VOL. 82] 



Paris. 

 Academy of Sciences, lanuary 17.— M. Emile Picard 

 in the chair. — E. Bouty : The electric cohesion of neon. 

 Although the molecular weight of neon is intermediate 

 between argon, the molecular weights, and helium, its 

 dielectric cohesion is much lower than that of the latter. 

 The dielectric cohesion of neon is lower than that of any 

 known gas ; from the point of view of the obstacle opposed 

 to the electric discharge, 57 cm. of neon are equivalent to 

 a layer of i cm. of air. — W. Kilian : A new example of 

 phenomena of convergence in ammonites : the origins of 

 the group .immonitcs bicurvatus. — A. de Gramont : The 

 distribution of the ultimate lines in stellar spectra. — 

 A. Demouiin : The K systems and congruences. — M. 

 Cisotti : An application of the method of Jacobi. — Ludovic 

 Zoretti : Ensembles of points. — L. Decombe : The 

 elimination of directing electric couples, and effects due to 

 asymmetry, to the absence of regulation and to contact 

 electromotive forces in quadrant electrometers. — Edmond 

 Bauer and Marcel Moulin : The constant in Stefan's law 

 and the radiation of platinum. In a recent paper the 

 authors described a method of determining the constant 

 a in Stefan's equation E=(rT' by the comparison of the 

 radiation of a black body at 1064° C. with the radiation 

 of a platinum sheet, known, in absolute measure, by 

 experiments in a vacuum. It was assumed that the 

 radiation of platinum followed Lambert's law up to large 

 angles of emission ; the latter assumption has now been 

 proved by experiment to be inaccurate, and the introduc- 

 tion of the resulting correction reduces the original value 

 of <r from 6oxio-'^ to 5-3x10-'-, a figure in good agree- 

 ment with the 5-32x10-'- of Kurlbaum. — .\. Colson : The 

 difficulties of chemical bibliography. .\ reply to some 

 criticisms of M. Baubigny. — E. Kohn-Abrest : The action 

 of heat upon aluminium in a vacuum. Aluminium is 

 volatilised appreciably at 1100° C. in a vacuum, setting 

 free silicon from the walls of the tube if the latter con- 

 tains a silicate.^G. Charpy and S. Bonnerot : The 

 cementation of iron by solid carbon. In these experiments 

 both the iron and the carbon were submitted separately 

 to a prolonged heating in a vacuum until no trace of gas 

 was given off. The iron and carbon were then heated in 

 contact at 1000° C, in a high vacuum, for several hours. 

 No trace of carbon was absorbed by the metal under these 

 conditions, although cementation was produced if traces 

 of air were present. — Pierre Camboulines : The actioa of 

 the vapours of carbon tetrachloride on anhydrides and 

 oxides. The action of carbon tetrachloride vapour upon 

 thirty-three oxides was studied. Silica and boric anhydride 

 were not attacked ; in the other cases a reaction took place 

 at temperatures between 215° C. (niobic anhydride) and 

 580° C. (chromium oxide), the pure chloride of the rnetal 

 being formed, excepting with niobic anhydride, thorium, 

 and uranium oxides. With these a mixture of chloride 

 and oxvchloride was formed. This reaction furnishes a 

 good general method for the preparation of anhydrous 

 metallic chlorides. — R. Fosse : The transformation of 

 some aromatic alcohols into phosphinic acids by hypo- 

 phosphorous acid. — Gabriel Bertrand and G. Weis- 

 weiller : Vicianose, a new reducing C,, sugar. By the 

 action of a diastatic preparation extracted from^ T'lVia 

 angiistifolia upon the cyanhydric glucoside^ vicianine de- 

 scribed in a previous paper, a new reducing sugar has 

 been isolated. It has the composition C,,H,„0,„, and is 

 the first definite biose prepared by the diastatic hydrolysis 

 of a glucoside. — Marcel Guerbet : The condensation of 

 secondary butyl alcohol with its sodium derivative ; 

 3-methyl-s-heptanol and an alcohol, C,,H.,0, result from 

 this condensation. — A. Verneuil : The synthetic reproduc- 

 tion of the sapphire by the method of fusion. _ Blue 

 sapphires, possessing the colour and optical properties _ of 

 the natural stone, have been prepared by heating alumina 

 containing 1-5 per cent, of magnetic oxide of iron and 

 0-5 per cent, of titanic acid in the oxyhydrogen blow- 

 pipe. — A. Conte : Anomalies and spontaneous variations in 

 the domestic birds.— Louis Masson : The tolerance of 

 bacteria to antiseptics. Three species, B. pyocyaneus, 

 B. suhtiUs, and B. anthracis, were grown in cultures_ con- 

 taining small amounts of antiseptics (resorcinol, salicylic 

 acid, copper sulphate, and mercuric chloride), and the 



