June i6, 192 i] 



NATURE 



495 



inquiries respecting the identity of chemical, elec- 

 trical, and magnetic forces "was well rewarded 

 in the winter of 1819 by the discovery of a fact 

 of which not a single person besides himself had 

 the slightest suspicion, but which when once known 

 instantly drew the attention of all those who were 

 at all able to appreciate its importance and value." 



From the autumn of 1822 to the summer of 

 1823 Oersted was in Germany, France, and Eng- 

 land. He is less enthusiastic than in the past 

 about the German men of science whom he met. 

 " Schweigger at Halle has brains, but is a 

 reed shaken with the wind. His experiments are 

 not of much importance. Kastner at Erlangen 

 writes thick volumes compiled with much toil but 

 without all judgment. Yelin at Munich makes 

 indifferent experiments and lies much. But I 

 have found much that was instructive with 

 Fraunhofer at Munich, so that I have been able 

 to occupy myself with benefit there for about a 

 fortnight." 



To the Frenchmen he is more kindly. "My 

 stay here grows more and more interesting to me 

 every day. The acquaintances I have made grow 

 every day more cordial and intimate," he 

 writes to his wife from Paris in February, 1823. 

 He saw Biot, Fresnel, Pouillet, Ampere, Arago, 

 Fourier, Dulong, and many others : such was the 

 brilliant list of physicists then at work in Paris. 

 With Ampere he had many discussions as to their 

 rival theories ; at one time he thought he had dis- 

 proved the existence of the molecular currents 

 which in Ampere's view constitute a magnet. 

 Mrs. Meyer quotes from another letter an amusing 

 account of a three hours' discussion which took 

 place after a dinner given by Ampere. Among 

 the guests were two of the host's pupils, and of 

 them Oersted writes: " Even Ampere's two dis- 

 ciples declared that my theory was able to explain 

 all his phenomena. They declare that so will 

 Ampere's, and as his theory is nothing but the 

 reverse of mine, he having removed the circuits 

 of forces discovered by me from the conductor to 

 the magnet, it will no doubt be diflficult to find an 

 entirely decisive objection to his theory." 



The experiments which Ampere arranged for 

 his benefit were not successful. " On the loth I 

 was at Ampere's by appointment to see his ex- 

 periments. He had invited not a few. . . . He 

 had three considerable galvanic apparatus ready ; 

 his instruments for showing his experiments are 

 very complex ; but what happened ? Hardly any 



of his experiments succeeded. He is dreadfully 

 confused, and is equally unskilful as an experi- 

 menter and as a debater." Somehow this is hard 

 to believe; some at least of the confusion existed, 

 we may suspect, in the mind of the narrator. 

 Ampere's own descriptions of his work are 

 models of clearness; his formula remains, as has 

 been said above, ' ' the cardinal formula of electro- 

 dynamics." 



Oersted lived for some thirty years after the dis- 

 covery of 1820, engaged almost to the last in 

 physical work. During part of the time he was 

 greatly interested in measurements of the com- 

 pressibility of liquids. Details of some of these 

 are given in a letter to Brewster dated December 

 30, 1826. He was one of the first to realise the 

 necessity of allowing for the expansion of the 

 vessel containing the liquid, and a piezometer 

 which he described in the Proceedings of the 

 Danish Society of Sciences for 182 1 has been 

 frequently employed for measurements of the 

 kind, though Oersted was mistaken in thinking 

 that it avoided all the difficulties arising from the 

 expansion of the containing vessel. 



Under date 1845 we have the following sug- 

 gestion for a moving coil galvanometer : "A 

 metal wire bent as a multiplier and able to revolve 

 easily round two points is placed opposite the 

 poles of a strong magnet in such a way that it 

 will be deflected as soon as it is traversed by 

 electricity." 



In 1848 Denmark was at war, and in a 

 letter of that date Oersted alludes to the fact that 

 thirty years earlier he had experimented on the 

 use of electricity for firing mines, and makes the 

 suggestion of " burying in a road to be taken by 

 an attacking enemy, under a comparatively thin 

 layer of earth, small reservoirs filled with gun- 

 powder and earth or small fragments of stones 

 which could be fired by a communicating wire on 

 a given signal and that in a shorter time than 

 one second after the signal." 



More will be found in Mrs. Meyer's excellent 

 volume about the activities of a remarkable man ; 

 she has done her work admirably, and we are 

 indebted to her for her labours in producing this 

 most interesting work. The book, which is 

 printed in English, has been published in Copen- 

 hagen under the editorship of the Royal Danish 

 Society of Sciences, and is in every wav a worthy 

 memorial of perhaps the most distinguished 

 member of that societv. R. T. G. 



Native Life in the Loyalty Islands and Southern Nigeria.^ 

 Bv Henry Balfour. 



(i) V/f RS. HADFIELD'S book on the Loyalty 

 ^'^' Islands is the outcome of a long resid- 

 ence in this group, in connection with the work of 



1 (i) " Among the Natives of the Lovaltv Group." By E. Hadfield. Pp. 

 xix + 3i5 (London: Macmillan and Co., Ltd., 1920.) 12J. 6^. net. 



(2) " \mone: the Ibos of Nigeria : An Account of the Curious an-i 

 Interesting Habits, Customs, and Beliefs of a Little Known African People 

 by One who has for Many Years Lived amongst Them on Close and 

 Intimate Terms." By G. T. Basden. Pp. 315. (London : Seeley, Service, 

 and Co., Ltd., igii.) 25^-. net. 



NO. 2694, VOL. 107] 



the London Missionary Society. The greater part of 

 the time was spent on Lifu Island, but eight years 

 were spent on the smaller island of Uvea. The 

 account which she gives of the natives is unpre- 

 tentious and straightforward, written in an easy 

 and attractive style and with a vein of humour. 

 She reveals her sympathy with the natives, with 

 whom she became on excellent terms, and much 



