January 12, 1922] 



NATURE 



49 



other. A number of special cases are worked out 

 tor both positive and neg^ative rays, and the lumin- 

 osity at different heights is considered. 



Chap. 5, pp. 213-222, comparing- theory with 

 observation, gives a brief analysis of the observed 

 heights and contains some historical matter. The 

 a-ray theory of aurora is credited to Prof. 

 X'cgard, who has now, however, abandoned it. 

 ihe author's own conclusions seem, on the whole, 

 iji general accord with those now held by Vegard. 

 lie considers that the luminosity phenomena of 

 aurora cannot be explained on the a-ray hypo- 

 thesis except for what he calls "plaques pulsa- 

 toires." The most likely sources of all other 

 auroras, he thinks, are cathode rays. 



On pp. 221-22 is an interesting statement of 

 what Prof. Stormer takes to be the auroral prob- 

 lems now calling for attention. The observational 

 problems include height measurements in the 

 Arctic and Antarctic, and the investigation of the 

 auroral spectrum at different levels. The first theo- 

 retical problem remaining is to take account of the 

 mutual electro-magnetic actions of the corpuscular 

 currents, as well as of the action of the magnetic 

 fields of the earth and sun. "On pourra alors . . . 

 etudier jusqu'a quel point les objections de Shuster 

 (Schuster) relatives a des faisceaux cathodiques 

 dans I'espace sont bien fondees ou non." A second 

 theoretical problem is to apply the knowledge we 

 may gain of the auroral corpuscles to the study 

 of solar physics. 



The second paper by Prof. Stormer relates to 

 auroral measurements made during a great mag- 

 netic storm on March 22-23, 1920. Use was made 

 on that occasion of seven stations giving bases 



varying in length from 26 to 250 krrt. Of the 

 heights measured, six exceeded 500 km., one 

 being 607 km. The plates attached to the paper 

 are enlarged negatives of the photographs ob- 

 tained. The photogfaph reproduced here (Fig. 4) 



Fig. 4.— Aurora during the magnetic storm of March 22-23, 1920. 



is a positive, which we owe to the kindness of 

 Prof. Stormer. The demonstration of the exist- 

 ence of a sensible atmosphere at heights exceeding 

 500 km. is a notable event. 



The Meldola 



RAPHAEL MELDOLA was a man of remark- 

 able versatility, eminent to an unusual degree 

 in several sciences— chemistry, biology, entymology, 

 astronomy — a n d of u n - 

 l)Ounded energy. How broad 

 his sympathies and interests, 

 were,' and how distinguished 

 liis services, should be suffici- 

 ently apparent from the fact 

 That' he was elected to the 

 lesidential chairs of the 

 Issex Field Club, the Ento- 

 mological Society, the Chem- 

 ical Society, the Society of 

 Dyers and Colorists, the 

 Society of Chemical In- 

 dustry, and the Institute of 

 riiemistry. Apart from the 

 distinctions connected with 

 his scientific pursuits. Mel- 

 dola was held in high honour 

 among his own people as 

 president of the Maccabxans, 

 a society in London con- 

 sisting mainly of Jewish 

 [uofessional men devoted 

 to the promotion of the 

 interests of the Jewish race. 



NO. 2724, VOL. 109] 



Medal. 



That society has instituted a medal in 

 perpetuate his memory, and has arranged 

 council of -the Institute of Chemistry 



order to 

 with the 

 that the 



The Meldola Medal. 



