March 24, 192 1] 



NATURE 



125 



Societies and Academies. 

 London. 



Royal Society, March lo. — Prof. C. S. Sherrington, 

 president, in the chair. — Sir Joseph Larmor : Electro- 

 crystalUne properties as conditioned by atomic lattices. 

 The view that the crystal lattice is usually composed 

 of atoms is considered in relation to their ionic 

 charges. Compensating surface charges on certain 

 types of faces of a crystal are required ; and inference 

 is drawn with regard to the texture of crystal faces. 

 The alternative view that a bipolar molecule is the 

 crystal-unit would seem to encounter difficulties also 

 as regards pyroelectric effect-s. Dielectric excitation 

 can be represented as relative displacement of the 

 positive and negative component lattices under the 

 influence of an electric field.. If the compound lattice 

 has spiral features, so that the relative shifts of its 

 various components with positive and negative charges 

 are of screw tvpe, chiral optical quality will be in- 

 volved ; a coarse numerical estimate indicates that in 

 quartz and active liquids the twisting relative displace- 

 ment of the ionic configurations is comparable in 

 amount with their relative elongation. The chiral 

 quality may reside wholly in the crystalline structure, 

 disappearing on fusion or solution ; or else the process 

 of dielectric displacements of the positive and negative 

 groups of ions in the crystal-unit may be also itself 

 chiral. In either case, induced static polarity could 

 not be chiral as regards waves so long as those of 

 light ; but this process of screw displacement is opera- 

 tive kinetically in the optical rotation by involving a 

 magnetic moment of changing ionic twist induced by 

 the alternating electric field of the radiation. A face 

 of a crystal of cubic type containing both types of 

 ions equally should acquire no true pyroelectric 

 charge. Double refraction induced by strain must be 

 ascribed to bending of ionic lattice structures, or in 

 glass to fragments of such structure. — Prof. A. S. 

 Eddington : A generalisation of Weyl's theory of the 

 electromagnetic and gravitational fields. From the 

 notion of "parallel displacement" used bv Weyl in 

 his theory, it is shown that a tensor *^%„ exists 

 eiving a measure of the world-structure at each point. 

 The contracted tensor *G^„, formed bv setting p — a-, 

 breaks up into two parts : (i) a symmetrical part 

 which is the gravitational potential g^v of Einstein's 

 theory, and (2) an antisymmetrical part F^„ (proved 

 to be the curl of a vector) which is identified with the 

 electromagnetic force. The theorv explains how, not- 

 withstanding the non-integrabilitv of length in Weyl's 

 geometry, there is a natural gaug^e ; and Einstein's 

 interval is an absolute invariant independent of gauge, 

 and directlv comparable with other intervals at a 

 distance. The law of gravitation for empty space in 

 the form finally adopted by Einstein, viz. G^„ = \?"^„, 

 follows at once on this theory. All the other recog- 

 nised field-laws are found by identifying the physical 

 measures with geometrical tensors which satisfy these 

 laws identically. None of these impose any constraint 

 on the possible varieties of world-structure ; and there 

 is no reason to introduce a physical principle of 

 stationarv action, at least so long as we do not deal 

 with problerris of electron structure. Explicit expres- 

 sions for *B^,„ and *G^„ are found in terms of Ein- 

 stein's gravitational tensors and a tensor Km^v which 

 represents electric and electronic forces. Weyl's theory 

 corresponds to the particular case when K^'v,^ is of 

 the form g-^r^'.—Vroi. T. R. Merton : Spectrophoto- 

 metry in the visible and ultra-violet spectrum. The 

 application of the neutral wedge to spectrophotometric 

 measurements is extended. The method involves the 



NO. 2682, VOL. 107] 



"crossing" of the prismatic spectrum with a diffrac- 

 tion spectrum, the relative intensities of the different 

 orders in the diffraction spectrum having been experi- 

 mentally determined. The method of preparing 

 and calibrating gratings for this purpose is 

 described. The method is applicable to the 

 determination of the relative intensities of lines in 

 discontinuous spectra, but is specially adapted to the 

 study of continuous spectra, absorption spectra, and 

 the study of broadened lines. The method may have 

 a special application in celestial spectroscopy. — Prof. 

 W. A. Bone : .Researches upon brown coals and lig- 

 nites. Part i. : Heat treatment at temperatures below 

 400° C. as a possible method for enhancing their fuel 

 values. A classification of lignites is made according 

 to their external appearance : (a) Woody or fibrous 

 brown coals. (fe) Amorphous or earthy brown coals, 

 (c) Common or brown lignites, (d) Black lignites. Lig- 

 nites have a moisture content varying between 10 and 

 50 per cent. ; on air-drying they usually disintegrate 

 or crumble to powder. They are devoid of any coking 

 properties, and in the "dry ashless" state usually 

 contain less than 70 per cent, of carbon and more 

 than 20 per cent, of oxygen. Experiments were con- 

 ducted on the various types of lignites, which were 

 heated in a special form of apparatus that allowed 

 accurate measurement of temperature and amounts 

 of liquid and gaseous products. Chemical change 

 takes place, beginning- at a low temperature of about 

 130° C. and progressing to a temperature at which 

 no condensable hydrocarbons were eliminated from 

 the fuel, termed the "practicable up-grading limit.'* 

 Steam and carbon dioxide, with a small amount of 

 carbonic oxide and a negligible amount of hydrocarbons, 

 were eliminated. Practically the whole of the poten- 

 tial energv of the lignite is concentrated in the residue 

 obtained by this "up-grading" treatment. — Prof. 

 H. N. Russell : A superior limit to the age of the 

 earth's crust. The method of determining the age of 

 a mineral from the ratio of lead to uranium in its 

 composition may be extended to the earth's crust as 

 a whole. Accepting a radium content of 2-5x10-** 

 (Joly), corresponding to a uranium content of 



7x10-*, and a content of lead of 22x10-* (F. W. 

 Clarke), It follows that the age of the crust does not 

 exceed 11 x 10' years, which is reduced to 8 x 10' years, 

 if allowance is made for thorium.— H. Ohshima ; 

 Reversal of asymmetry in the plutei of Echinus 

 miliaris. In the normal Echinoderm larva the hydro- 

 coele and its associated structures develop on the left 

 side of the larval bodv. Rarely the reversal of this 

 asvmmetrv occurs. This abnormality was found in 

 more than 10 per cent, of the artificially reared larvae 

 of Echinus miliaris. It may be a result of (i) change 

 of polaritv in the eg^, or (2) twin-formation, or, most 

 probably, (3) "compensatory hypertypv," owing to the 

 arrest in development and later atrophy of the normal 

 left hvdrocoele. The right anterior coelom Is known 

 to have latent potentialities for producin-^ a hvdro- 

 coele, which can probablv be activated bv the stimulus 

 due to the arrest in development of the left hydroccele. 

 The arrest is probably associated with the obliteration 

 of the pore-canal. throu£*h which the hydroccele has 

 been communicating with the exterior. The occur- 

 rence in much lower percentage of the double-hvdro- 

 coele larvae and of those devoid of the hydroccele within 

 the same culture jars can be similarlv explained. If 

 the left hvdrocoele resjalns Its communication with the 

 exterior. It will continue to develop with the abnormal 

 right hydroccele, trivlnfj rise to the double-hvdrocoele 

 larva. If the richt hvdrocoele fails to appear while the 

 Teft hvdrocoele Is still deprived of its communication 

 with the exterior, a larva devoid of hydroccele will 

 result. 



