NATURE 



;6i 



THURSDAY, FEBRUARY i8, 1892. 



A COLLECTION OF MEMOIRS ON PHYSICS. 

 Collection de Memoires relatifs a la Physique. Publics 



par La Soci^td Frangaise de Physique, tome 1-5. 



(Paris, Gauthier-Villars.) 



LA Socidte Frangaise de Physique in the volumes 

 before us have initiated a movement which cannot 

 fail to be of the greatest service to students of physics. 

 They are publishing collections of memoirs on one sub- 

 ject written by several authors, instead of following the 

 more usual plan of collecting the papers of one author 

 on a variety of subjects. There can, we think, be no 

 question as to which plan is of most service to the 

 student. The collected papers of one author must 

 from the nature of the case be chiefly used as a work of 

 reference, while the study of a collection of the most 

 important memoirs ought to form an essential part of the 

 reading of every advanced student of the subject. Now 

 that the memoirs in which the foundations of the sciences 

 of electrostatic or electromagnetism, and of investigations 

 with the pendulum, are by the enterprise of the French 

 Society so readily accessible, it is to be hoped that there 

 will be a much greater development of the systematic 

 study of the original memoirs than we are afraid prevails 

 at present. 



Science, as Maxwell said, is most easily assimilated 

 when it is in the " nascent " condition, and, moreover, it 

 is to be expected that when a long paper by a master of 

 his subject has been condensed in a text-book to a 

 twentieth of its original length, something of importance 

 must be lost. In a text-book there is as a rule but little 

 room for anything beyond the description of the method 

 which ultimately proved successful, all reference to the 

 difficulties met with, and the way they were overcome, has 

 to be omitted, though these are precisely the points most 

 calculated to induce the student to endeavour to make 

 investigations for himself. 



The volumes before us are also of especial interest to 

 the student of science, as they contain papers such as 

 those by Coulomb on electrostatics and magnetism, and 

 by Ampere on electromagnetism, which raised the subject 

 with which they dealt from chaos to order. 



The first volume of these collected memoirs is edited 

 by M. Potier, and differs somewhat in character from 

 those which follow, inasmuch as it is entirely devoted to 

 papers by Coulomb. It contains the classical memoirs 

 in which he established by the aid of the torsion-balance 

 the fundamental laws of electrostatics, and of the action 

 between permanent magnets. It also contains a memoir 

 on the loss of electricity by an insulated charged body, 

 in which he comes to the conclusion that there is a 

 leakage of electricity through the air ; subsequent experi- 

 ments have, however, shown that this is erroneous, and 

 that there is no such loss when the air is free from dust 

 and the charged body not under the action of ultra-violet 

 light. 



Itis remarkable,consideringthe importance of Coulomb's 

 contributions to electricity and magnetism, that his most 

 important memoirs on these subjects were all published 

 NO. I I 64, VOL. 45] 



within five years, 1785-1789, when he was between 49 

 and 53 years of age. 



The editor gives as an appendix a very clear account 

 of Poisson's and Sir W. Thomson's investigations of the 

 problem of two electrified spheres. Poisson's papers on 

 this subject are not very accessible, and we wish that 

 they had been included in this volume, as his investiga- 

 tion of this problem is surely one of the most elegant 

 pieces of analysis ever written. It is possible, however, 

 that it was deemed to be too exclusively mathematical to 

 be included in this collection of physical memoirs. 



The second and third volumes, edited by M. Joubert, 

 are devoted to electromagnetism. They include CErsted's 

 paper, published in France in 1820, announcing the dis- 

 covery of the deflection of a magnet by a current, and 

 the marvellous series of papers published almost weekly 

 by Ampere, in which, in a few months after the publica- 

 tion of Oersted's discovery, the " Newton of Electricity" 

 established the action of a magnet on a current, and of 

 one current on another, and of the identity of magnets 

 and electric currents. In his earlier papers, those pre- 

 vious to 1822, Ampere seems to have been hampered by 

 the erroneous idea that the force between two small 

 elements of current at right angles to the line joining them 

 was indefinitely small compared with that between the 

 same element at the same distance when forming parts of 

 the same straight line. Instead of being infinitely smaller, 

 it is in reality, as he showed later, just twice as great. 

 He soon, however, corrected this mistake, and in 1822 

 gave to the world a complete theory of the mechanical 

 forces between currents in a memoir which is reprinted in 

 these volumes, and which was described by Maxwell as 

 "perfect in form and unassailable in accuracy." 



In addition to the papers we have mentioned, there are 

 many others dealing with points of the greatest interest : 

 thus we find Olrsted, in his paper on the action of a current 

 on a magnet, suggesting that light may be an electrical 

 phenomenon, and Ampere writing in favour of this sug- 

 gestion. In the second volume we have a paper by 

 Faraday on electromagnetic solution ; two papers by 

 Davy, in one of which he describes a curious heaping up of 

 a layer of mercury over the places where a strong current 

 enters and leaves the mercury. This pretty effect is due 

 to the mechanical force between the current in the leads 

 and the current through the layer of mercury. This 

 paper also contains Barlow's description of his electro- 

 magnetic wheel, and two papers, not hitherto published, 

 by Fresnel, on Ampere's theory of magnets. Fresnel 

 appears to have been the author of the suggestion that the 

 currents by which Amp5re explained the magnetic pro- 

 perties flowed round the molecules of the iron. In the 

 third volume Weber's great paper on electrodynamic 

 measurements appropriately completes the series of 

 papers on electromagnetism, as the measurements made 

 by the methods it develops afford a complete verifica- 

 tion of the theory given in the preceding pages by 

 Ampere. 



The fourth and fifth volumes, edited by M. Wolf, 

 contain memoirs on pendulum experiments. They com- 

 mence vrith a well-written historical account of such ex- 

 periments. Next we have a bibliography extending over 

 216 pages, and then follows a series of admirably selected 

 papers of which the names speak for themselves. On 



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