662 



NATURE 



[February 19, 1920 



compounds. The electrons rotating in pairs around 

 the four carbon valencies may possess either clock- 

 wise or anti-clockwise rotation with respect to the 

 central carbon atom (Ramsay, Proc. Roy. Soc, xcii., A, 

 p. 451, 1915-16). On the assumption that two of these 

 pairs of electrons rotate in a cloclcwise and two in an 

 anti-clockwise direction, it is possible to deduce that 

 eight isomerides of cinnamic acid may exist. It has 

 long been known that four isomerides of cinnamic acid 

 exist, whereas onlv two are possible on the ordinary 

 structural formulae. 



Erlenmeyer has recently shown (Biochem. Zeitsch., 

 1919, xcvii., pp. 198-245) that ordinary cinnamic acid 

 can be obtained in two optically active isomerides. If 

 the clockwise rotation of the electron gives a north- 

 seeking character to the valency, and the anti- 

 clockwise rotation a south-seekinp character, it is 

 possible to represent eight isomeric cinnamic acids 

 as follows : 



(') 



(2) 



QHjv ^ H]H\^ -CcHr, 



N S 

 S N 



S- N 

 N S 



\/- 

 C 



(3) 



C 



,"\ 

 N S 

 S N 



\/- 

 C 



(4) 



\/ 



c„ir. 



s 



N 



•N 

 S 



COOH'^'^HiH/NGOOH H^^ COOHICOOH 



Syn-form 



Anti-form 



CM, 



(5) 

 C 



HiH 



(6) 



(7) 



N N 

 S S 

 \/ 



c 



c 



s s 



N N 

 \/ 



c 



CeHj C,H,. /M 



N 

 S 



cooa 



h;h 



Syn-form 



coon II 



N 



s 



■COOHICOOH/ ^11 



Ami-form 



(8) 



C 

 /\ 



s s 



N N 



\/ 

 C 



The formulae are grouped in pairs, and only two 

 of these pairs are mirror images, (5) being the mirror 

 image of (6), and (7) of (8). None of the isomerides 

 I to 4 are superposable, as can be readily seen from 

 the solid models. (A north-seeking valency will be 

 the mirror image of a south-seeking valency.) The 

 new type of optical activity is due not to the asym- 

 metry of the radicles, but to an asymmetric arrange- 

 ment of the pairs of rotating electrons. 



It may be that the dextro- and laevo-rotatory forms 

 of an organic compound are not structural isomerides, 

 but owe their optical activity to this asymmetric 

 arrangement of the electrons : 



K., 



R, 



N S 



\ / 



C 



/x 



S N 



•N- 



K. 



I<4 



1<4 



There is thus possible a large number of such 

 isonierides in organic chemistry which are, however, 

 stable only in ver\ few types "of organic compounds. 

 The case of the cinnamic acids is nqt an isolated one. 

 for it appears from the work of Erlenmeyer that 

 benzaldehyde is capable of occurring in the dextro- 

 and laevo-forms (Biochem. Zeitsch.. 1914, Ixiv., 

 pp. 382-92), and also, according to Marckwald, 



NO. 262s, VOL. IO4I 



methyl-ethyl-malonic acid occurs in optically active 

 forms. 



This theory differentiates between two kinds of 

 valency, according to whether the rotation of the elec- 

 trons with respect to the valency is clockwise or anti- 

 clockwise, and may explain the peculiar characteristics 

 of the physical properties of the homologous series, 

 where those compounds containing an even number 

 of carbon atoms appear to belong to one series, and 

 those with an uneven number to another series. 



.Ml the isomerides which are obtained on this 

 theorv, except the optical pairs, should possess 

 different free energies according to the arrangement 

 of the rotating electrons. W. E. Garnkr. 



I'niversity College, London, February 2. 



The Sociological Society. 



May I beg the hospitality of your columns for two 

 announcements? First, the Sociological Society is 

 moving from the London School of Economics and 

 Political Science to a house of its own at 65 Belgrave 

 Road, Westminster, S.W. i. The society hopes to get 

 installed there by the beginning of March. 



The second is that the society's new house affords 

 more accommodation than the society itself can use, 

 and we should be glad, therefore, to hear from con- 

 gruent societies or organisations which might desire 

 to rent one or more rooms. The present housing 

 pressure is, we understand, putting not a few societies 

 into n considerable diffirully as regards accommoda- 

 tion. 



.\s to the situation, the new house of the Sociological 

 Societv is about five minutes' walk south-east from 

 Victoria Station. It is just over a mile in a direct 

 line from Charing Cross, and two 'bus routes (24 and 

 24A) crosjs Belgrave Road, within a couple of minutes' 

 walk of the house. T. J. C. Eraser Davies, 



Fohruarv t6. Secretary. 



Mirage Effects. 



While a patient at the Red Cross Hospital for 

 Officers, l^righton, the phenomenon described by 

 various correspondents was observed by me on 

 numerous occasions last autumn. It was particularly 

 noticeable on hot, sunny days along the Marine 

 Parade, Kemptown. From a point opposite the Hotel 

 Bristol, the road a quarter of a mile distant, in either 

 direction, appeared as if flooded by a water-cart. 

 Indeed, the illusion was so complete that the first 

 time I witnessed it, being confined to a spinal chair, 1 

 instructed mv attendant to make a detour. 



Robert Ross. 



3 Sudclex' Termce, Brighton. 



.\n excellent place to observe mirage round our 

 coasts is Morecambe Bay on a sunny afternoon when 

 the tide is out and a fresh breeze is blowing in from 

 the sea. Viewed from the low shore bv Hes.t Bank, 

 the Furness shore is clearly reflected in detail, even 

 the steam of trains on the Furness Railwav. .Mso, 

 the bay towards Carn forth appears to Im^ full of 

 water where there is only drv sand. 



Mirage effect on an asphalted pavement m;iv be 

 seen on the North Road between Newcastle-upon-Tvne 

 and Gosforth when the sun is shining warmlv and 

 at the same time a cool wind from the north-east is 

 blowing across it. The effect is observable to anyone 

 walking uo the road and approaching a level portion 

 or slight deoression. .Ai.rert Tarn. 



Barrow Hedges, Carshalton, February 15. 



