Jan. 24, 1878] 



NATURE 



245 



currents caused by heating both a single metal and two 

 metals in contact, and formulated the well-known thermo- 

 electric series, bismuth, platinum, lead, tin, gold, silver, cop- 

 per, zinc, iron, and antimony. In his studies on atmospheric 

 electricity he proved that the water of the ocean and the 

 solid crust of the earth are in opposite electrical con- 

 ditions, a fact which explains the positive state of the air 

 immediately above the sea, while at a distance from the 

 ocean the positive change is noticeable only at a certain 

 height above the earth. The physiological effects of the 

 electric current formed likewise the subject of numerous 

 observations, and by means of delicate apparatus he was 

 able to demonstrate the development of minute currents 

 by the various operations of life, the movement of the 

 muscles, &c. In view of the purely chemical character of 

 these operations these observations harmonised perfectly 

 with the theory which he advanced that electric currents 

 were produced by all chemical unions and decompositions. 

 The effects of electricity on the colours of flowers, he 

 showed to consist chiefly in a mechanical bursting of the 

 cells containing colouring matter, and not in a chemical 

 change. The conductive powers of a number of elements 

 and compounds for the electric current, as well as the 

 thermal phenomena in bad conductors, formed likewise 

 the subject of numerous investigations. In magnetism 

 Becquerel's researches were confined chiefly to the demon- 

 stration of the ability of all bodies to be magnetised, and 

 to the phenomena of terrestrial magnetism. His favourite 

 field of discovery, and that in which he obtained the most 

 brilliant results, was electro-chemical action ; in the 

 variety and value of his contributions in this department 

 he is certainly surpassed by no other physicist, while he was 

 the first to grasp and sum together the scattered observa- 

 tions, and fairly mould them into a science. In 1834 he 

 observed the deposition of metal on the negative elec- 

 trode when the two poles of a pile were introduced into 

 solutions of the salts of various metals. Shortly after he 

 discovered that by using feeble currents the metal could be 

 deposited very evenly and equally on the surface of the 

 electrode, and that the two solutions required for the 

 purpose could be kept from mingling by the use of gold- 

 beater's skin or animal membranes, without hindering the 

 current. These facts were at once made use of by De la 

 Rive, of Geneva, who based on them his technical process of 

 gilding in 1840. Although not the first to make the prac- 

 tical application of his discoveries, Becquerel rapidly im- 

 proved the methods derived from them, and contributed in 

 swift succession an enormous number of facts which serve 

 as the fundamental principles of the art of galvano-plastic. 

 These are to be found in a compact state in Smee's 

 Elements of Electro-metallurgy. Becquerel's famous 

 Oxys^en- circuit, discovered at this time, made his name 

 known at once to a large circle, on account of its simple, 

 practical quantities. It consists of a glass tube covered at 

 one end with linen, which supports a layer of kaolin, and 

 designed for the solution of the metallic salt to be 

 reduced. This is placed in a vessel containing a dilute 

 acid, and the object to be electro-plated is immersed in 

 the solution after being connected by a wire with a 

 platinum plate in the acid. The action begins instan- 

 taneously, and is both rapid and regular. Another well- 

 known apparatus is his depolariser, an arrangement 

 designed to obviate the reverse currents produced by the 

 gaseous deposits on platinum electrodes, and consisting 

 essentially in a continuous shifting of each of the plates 

 to the liquid of the other, so that they have no opportunity 

 to become polarised. The oxygen-circuit, with its gentle 

 regular current, was used by Becquerel for the decomposi- 

 tion of a large variety of chemical compounds. Among 

 the more noteworthy preparations by its action can be men- 

 tioned aluminium, silicium, beryllium, sulphur, and the 

 various earthy and metallic phosphates. Equally extensive 

 were the preparations of crystalline salts, notably those oc- 

 curring in nature, by the action of the electric current on 



mixed solutions or on solutions of soluble salts in con- 

 tact with insoluble substances. Daring the past ten years 

 his attention has been almost exclusively devoted to the 

 novel and remarkable electro-capillary phenomena first 

 observed by him in 1867. These can be observed in their 

 simplest form when a cracked test-tube containing a 

 solution of cupric sulphate, for example, is immersed in a 

 solution of sodic sulphide. A deposition of metallic 

 copper takes place at once on the crack. Tnis elementary 

 fact has been elaborated in a variety of directions with 

 numerous solutions, and the laws regulating the develop- 

 ment of electric currents by capillary action partially 

 enunciated. The study of these phenomena is, however, 

 still in its infancy. Becquerel regarded them as explana- 

 tory of the deposition of metals in veins in the rocks and 

 of many physiological reactions taking place in the vege- 

 table and animal tissues. A very detailed account of 

 the experiments is to be fDund in vol. xxxvi. of the 

 Memoires de V Imtittit. 



Desp te his manifold experimental investigations, Bec- 

 querel was an indefatigable author, and contributed a 

 most valuable series of standard works to the physical 

 literature of the past forty years. ^ In the seven volumes 

 of his " Traitd experimental de I'Electricit^ et du Mag- 

 ndtisme, et de leurs Phdnomfenes naturels," 1834-40, he 

 presented these two sciences with a completeness and 

 systematic arrangement which has been hitherto wanting 

 in physical Hterature. This work was followed by 

 " El^iTients d'Electro-Chimie appliqu^e aux Sciences natu- 

 relles et aux Arts," 1843; " Trait^ de Physique consi- 

 d.ix€i dans ses Rapports avec la Chimie," 1844, 2 vols. ; 

 " Elements de Physique terrestre et de M^tdorologie," 

 1847; " Trait^ de TElectricitd et du Magn^tisme ; leurs 

 Applications aux Sciences physiques, aux Arts, et k 

 I'Industrie," 1856, 3 vols. ; R^sumd de I'Histoire de 

 rjfelectricitd et du Magndtisme," 1858 ; and " Des Forces 

 physico-chimiques et de leur Interpretation dans la Pro- 

 duction des Phenom^nes naturels," 1875. 



In 1829 Becquerel was elected a member of the French 

 Academy, and received in 1874 the Medaille Cinquante- 

 naire, although he had been but forty-five years a 

 member. His scientific communications are to be found 

 in the Comptes Rendus of the Academy and in the Annales 

 de Chimie et Physique. The Royal Society elected him 

 as a corresponding member a number of years ago, and 

 he was one of the three French savants who have been 

 recipients of the Copley Medal. In 1865 Napoleon III. 

 decorated him with the Cross of Commander of the 

 Legion of Honour. 



Prof. Becquerel leaves behind him a son, Edmond 

 Becquerel, Professor of Physics in the Conservatoire des 

 Arts et Metiers, who has assisted his father for a long 

 series of years in the compilation of his numerous works, 

 and whose researches in electricity fairly rival those of 

 the latter. The funeral ceremonies took place on 

 Monday in the church of St. Medard, at Paris. 



DAVYUM^ 



ABOUT the middle of this year (1877) I succeeded in 

 isolating a new metal belonging to the platinum 

 group. I named it Davyum, in honour of Sir Humphry 

 Davy, the eminent English chemist. 

 The platiniferous sand from which it has been extracted * 



I From an article by Sergius Kern in La Nature. 

 * The sand treated had the following composition :— 



Platinum 



Irid'um 



Rhodium 



O-mium 



Palladium 



Iron 



Ruthenium 



Copper 



