370 Progress of European Science. [Aug. 



like the letter V. He fills the curved part of it with kaolin, (porcelain clay,) 

 previously boiled in acid ; he then fills one branch of the syphon, with a solution 

 of chloride of sodium — the other with one of nitrate of copper ; lastly, a bit of cop- 

 per-wire is put into each, and the openings are closed with mastic. 



The two solutions upon their gradual mixture acquire different states of electri- 

 city: the wire plunged in the nitrate becomes negative, while that in the chloride 

 remains positive ; the nitrate of copper is decomposed, and its metal deposited 

 upon the wire which is plunged into it, whilst the oxigen of the base transports 

 itself to the positive wire plunged in the chloride and thus produces a double chlo- 

 ride, because a portion of this chlorine unites with the metallic wire, and the 

 chloride of copper resulting combines with the chloride of sodium. The greater 

 part of the nitric acid remains free in the branch where the copper is deposited. — 

 Journal des Savans, Jan. 1831. 



In the proceedings of the Royal Institution of February last, we also find the fol- 

 lowing notice of some experiments made by Dr. Richie, on the laws of action in 

 an elementary galvanic battery, and their application to the laws of a compound 

 battery. 



" Dr. Richie's experiments proved, that Volta's electro-motive theory was in- 

 correct, and that decided voltaic effects could be produced by one metal and one 

 fluid. He attempted to account for the deflection of the needle and the decompos- 

 ing powers of an elementary battery, without supposing any actual transfer of the 

 electric fluid from the zinc through the fluid to the copper plate, by the definite 

 arrangement of the molecules of water. He shewed that the electro-magnetic ef- 

 fects are nearly inversely as the square roots of the distance between the plates : 

 and that the effects of two unequal batteries were nearly as the square roots of 

 their lengths. When their lengths were much extended, as is the case in an ele- 

 mentary battery, the increase of power begins to deviate from this law, and to 

 verge to a limit beyond which any increase in the number of plates would dimi- 

 nish their powers." 



II. — Electro- Magnetism. 



In the Philosophical Transactions for 1831, is an essay by Mr. Barlow on the 

 Probable Electric Origin of all the Phenomena of Terrestrial Magnetism, which 

 gives so clear a view of the progress of researches on this most interesting branch 

 of electricity, that we regret our limits do not allow us to present it to our readers 

 at length: the following is a summary of its contents. 



The facts relative to terrestrial magnetism collected during the scientific travels 

 of M. Humboldt were the first to awaken inquiry as to the laws of terrestrial 

 magnetism. The difficult task of reducing that eminent traveller's results to cal- 

 culation fell to the lot of M. Biot. 



" Considering the earth as a magnet, he assumed an indeterminate distance to 

 represent the distance of its two poles ; and then, supposing their power to vary 

 inversely as the square of their distance from the point on which they acted (a 

 law which had been already established,) he obtained a general expression for the 

 direction of a magnetic needle ; he then made his indeterminate distance varv • 

 and comparing at every step his results with those observed, it was found that 

 the nearer the poles were made to approach, the nearer the computed and observ- 

 ed results corresponded ; and finally, that the errors were reduced to a minimum 

 when the two poles were coincident, or indefinitely near to each other." This 



