202 TEANSACTIOXS OF THE SOCIETY OP 



so that tliis color becomes a characteristic indication of each metal. In experi- 

 menting on metallic alloys, he found that there is a decomposition of their ele- 

 ments in metallic vapors, such as results from the deposit of particles on the 

 electrodes. 



M. de la Rive has further, occupied the attention of the society on several 

 occasions with researches directed to the study of the relations existing between 

 the variations indicated by magnetic instrumefits, variations of the atmospheric 

 condition and the telluric currents which are manifested by putting in communica- 

 tion, through a telegraphic wire, two pLites sunk in the earth at a great distance 

 from each other. {BibJlotheq. Unirerse/le, Archives des Set., Ph>/s. ct Nat., vol. 

 xxii.) These communications were made either on the occasion of letters 

 addressed to our colleague by Father Secchi and read to the society, or of me- 

 moirs published by the latter. It was to researches on the same subject that 

 the note presented by M. de la Rive to the Helvetic Society of Natural Sciences, 

 during its last session at Zurich, related, which note concluded with the pro- 

 position that the society should nominate a commission charged with making 

 experiments on terrestrial currents, analogous to those which Father Secchi has 

 executed in two directions in the environs of Rome. The proposition having 

 been accepted and the commission named, authority has been obtained from the 

 fedei'al directory of telegraphs, which has manifested herein the utmost com- 

 plaisance and interest, for making use, during a certain number of hours, of the 

 direct wire connecting two distant stations, whether in the direction of the 

 magnetic meridian or in the perpendicular direction Experiments were first 

 made this spring by Professor de la Rive and Louis Dufour on the line between 

 Berne and Lausanne, and are to be continued. If we are authorized in assuming, 

 in conformity with the opinion of those physicists who have been most occupied 

 with the subject, that the regular magnetic variations consist of two periodical 

 variations superposed on one another, having different laws and due to diff'ereut 

 immediate causes, it is evident that the efforts of science should be directed to 

 a means of isolating the effect produced by one of the causes whose combined 

 action is manifested on the magnetized bars. It is in the sun, according to M. 

 de la Rive, that we must seek the origin of these two different modes of action 

 on the terrestrial magnetism ; one of them is due to the direct influence of the 

 sun, which varies according to the distance of that body and the nature of its 

 surface, as is proved by the correlation between the period of the magnetic 

 variations and that of the spots of the sun; the other would seem due to the 

 currents produced by the positive electricity of the atmosphere and the negative 

 electricity of the earth, which tend constantly to neutralize one another in the 

 polar regions, while the cause, which operates also constantly to separate the 

 two electricities, resides in the sun. Now, as M. de la Rive states, it would 

 appear most easy to isolate the terrestrial currents in order to study their varia- 

 tions and the phenomena to which they give rise, and it is with this vie^y that 

 be has proposed to make in Switzerland also, experiments on the currents 

 derived from the great terrestrial current. 



M. Louis Soret read a memoir* on researches undertaken to verify the electro- 

 lytic law in a particular case, and which completes previous labors of the same 

 savant. This memoir was directed to a comparison of the intensity of discontinu- 

 ous currents (particularly when the RuhmkorfT apparatus is introduced into the 

 circuit) with the chemical action of those currents measured by the weight of 

 the deposit of copper Avhich is produced. M. Soret also called the attention of 

 the society at different times to the more recent labors of M. Tyndall, and, among 

 others, to the researches of the English physicist on the relations which exist 

 between calorific and luminous radiations, and on the singular property of a 



*■ Rccherches sur la correlation da rdcctricitc dijnamique ct dcs autrcs forces physiques. 

 Memoires de la tSociet6 de Physique et dliistoire Xatuieile, tome XVIII. 



