134 Chronicles of Science. [Jan.. 



which different parts of the electric stratification present. 

 He compares these phenomena to those observed when a voltaic 

 current of a certain strength is passed through a chain composed 

 of alternate links of platinum and silver. The author proves, in 

 an ingenious manner, that the dark spaces of the stratifications 

 conduct electricity better than the luminous portions. He also 

 shows, by thermometric observations, that the temperature of the 

 luminous is more elevated than that of the dark portions. 



An improvement has been made by M. Bertsch on the some- 

 what celebrated electric machine of Holtz. The machine is too 

 complicated to allow of description in abstract. With a disc of 

 vulcanite, 50 centimetres diameter, sparks of about 15 centimetres 

 long can be obtained at the rate of from five to ten a second, and 

 having sufficient tension to pierce a glass one centimetre thick, and 

 to illuminate continuously a tube of rarefied gas one metre long. 

 In thirty or forty seconds it will charge a battery having an 

 interior surface of two square metres, which will burn up a thick 

 iron wire one metre in length. 



The subject of thermo-electricity has lately attracted much 

 attention. Our knowledge has now been considerably enriched 

 by an elaborate memoir by M. Becquerel on the thermo-electric 

 powers of different alloys, and the construction of thenno-electric 

 batteries. For thermo-piles for low temperature, he recommends an 

 alloy consisting of equal equivalents of antimony and cadmium 

 with one-tenth the weight of bismuth, for the positive metal, and 

 an alloy of ten of bismuth and one of antimony for the negative 

 metal. For piles of a high tension the negative metal should be 

 German silver, and the positive may be either the above antimony, 

 cadmium, and bismuth mixture, or fused and annealed sulphide of 

 copper • the latter stands the greatest heat, but gives also the 

 highest resistance. As sulphide of copper is a very bad conductor 

 of heat, it will scarcely be found necessary to cool the other ends ; 

 but this should be done when a metal is used, and the length of 

 the bar should, in that case, be increased. Thermo-electric 

 piles, on account of their low tension, cannot yet replace hydro- 

 electric batteries ; but, for special purposes, and particularly for 

 the study of radiant heat, the piles here described offer new facili- 

 ties, and are, therefore, worthy of attention. 



M. Zaliwski-Mikorski has introduced an improvement in the 

 method of filling and emptying the troughs of galvanic batteries 

 of two liquids, such as Groves's or Bunsen's. The permanent part 

 consists of an alternate succession of porous diaphragms and isolated 

 carbons. By means of tubes in the lower part, a liquid, poured 

 into one compartment immediately flows into all the analogous 



