PHYSICS. 247 



to the bottom of the vessel. The electromotive force, the in- 

 terior resistance, and the constancy of this couple are quite 

 equal to the Leclanche, while there is no incrustation of zinc 

 ammonium chloride and no loss by evaporation, the zinc 

 chloride being deliquescent. Moreover, when spent, this bat- 

 tery is easily recharged. 



Jablochkoff has constructed a pyro-battery in which car- 

 bon is the substance attacked. Two plates, one of coke, the 

 other of platinum, are placed in fused potassium or sodium 

 nitrate. The electromotive force varies between two and 

 three units, exceeding, therefore, that of the Bunsen or Grove 

 batteries. The coke may be ignited and put into the nitrate, 

 which is finely powdered; or the coke in fragments may be 

 enclosed in a basket of iron wire. 



An excellent illustrated description of Plante's arrange- 

 ments for experiments with his secondary battery is given 

 in Nature. In his laboratory lie has 400 of these batteries, 

 divided into ten sections, in each of two rooms. These 800 

 cells are charged by two ordinary Bunsen cells, they being 

 united for this purpose in simple circuit by means of a com- 

 mutator. When charged a process of several hours they 

 may be united in series by the commutator, and then dis- 

 charged, producing in a few seconds the enormous power 

 which they have accumulated. He has studied the effect of 

 these discharges upon various liquids, and has applied the 

 results to the explanation of meteorological phenomena con- 

 nected with electricity, such as thunder-storms, hail, and the 

 like. In his opinion even the ovoid or pyramidal form of 

 hailstones is due to their electric origin. 



Ituhmkorf, so well known for his remarkable improve- 

 ments in the induction coil, died at Paris on the 20th of De- 

 cember, having been in poor health for several months pre- 

 viously. He was born in Hanover, Germany, in 1803, went 

 to Paris in 1819, became porter in Chevalier's laboratory, 

 began the construction of physical apparatus shortly after- 

 wards, and brought out a convenient form of thermo-battery 

 in 1844. In 1851, after long experimentation, he brought out 

 his famous "Ruhmkorf coil," which gave sparks eighteen 

 inches long, and pierced glass two inches thick. He was re- 

 warded in 1858 by the government prize of 50,000 francs for 

 his discovery. In appearance he was of medium stature, 



