PHYSICS. 623 



connected with a platinum wire insulated in a glass tube and reaching 

 to the surface. The spiral is covered with copper sulphate solution, 

 which can be replaced by fresh solution poured in through a funnel 

 reaching to the bottom. On this solution lies a solution of zinc sulphate 

 in which the zinc cylinder is placed. A siphon whose outer leg is 

 directed from below ui)wards dips into the liquids as far as the bound- 

 ing plane, so that on pouring in fresh copper solution only the colorless 

 supernatant zinc solution flows off. The upper solution is by this means 

 kept free of copper, although after awhile some copper was found to be 

 precipitated upon the zinc cylinder, not sufficient, however, to impair 

 the constancy of the ceil. {Nature, January, 1885, xix, 308 ; Am. J. ScL, 

 March, 1885, III, xxix, 257.) 



Hayes and Trowbridge have investigated by a photographic method 

 the irregularities which occur in the action of galvanic batteries, and 

 have sought to ascertain the cause thereof. Since batteries in which 

 there is no porous partition do not show irregularities, while those con- 

 taining porous cups all give more or less mai'ked variations, the authors 

 believe that these irregularities are due, first, to a clogging of the 

 pores of the partition by some product of the action, and, second, to 

 electrical osmose ; the undulations being due to the former cause, and the 

 fluctuations, which are superposed upon the undulations, to the latter. 

 A cup of very dense earthenware gives both undulations and fluctuations, 

 while one which was very porous gave fluctuations without undulations. 

 Since, as Wiedemann has shown, a porous cup increases the amount of 

 metal transported to the negative pole and diminishes the quantity of 

 acid at the positive pole, a battery containing a small, thick cup and 

 giving a strong current will possess a maximum force tending to drive 

 the liquid and base from the i^ositive pole and to cause a corresponding 

 decrease in the current strength. Hence tlie partition should be made 

 of as large surface dimensions as possible, and should be made of very 

 porous material. {Am. J. Sci., July, 1885, III, xxx, 34.) 



It follows, as a consequence of the law of the conservation of energy, 

 as has been shown by Von Helmholtz and Thomson, that the electro-mo- 

 tive force of non-polarizing batteries is proportional to the energy of 

 the reactions developed in them by the passage of the current and may 

 be calculated from these reactions. To make this proposition incontest- 

 able it is necessary that the total chemical energy of the battery should 

 be converted necessarily into electric energy. The theoretical discus- 

 sion of this question has been recently made b;y Von Helmholtz, and 

 Czapski has undertaken to investigate experimentally the following re- 

 sults drawn from Von Helmholtz's conclusions : The batteries which do 

 not transform all the chemical energy into electrical energy are those 

 the electro-motive force of which decreases as the temperature rises, 

 and those which produce an electrical energy in excess of their calorific 

 energy are those in which the electro-motive force increases with the 

 |:emperature. Czapski's results confirm in general this theory of Vop 



