470 



next placed in contact with the zinc, while the exterior compart- 

 ments of the cells were filled with a saturated aqueous solution of 

 sulphate of copper ; but the effects were much diminished. It thus 

 appeared that the substitution of solutions of the muriates for dilute 

 sulphuric acid was in every way disadvantageous ; and it was more- 

 over found that, when the circuit was broken, the copper became 

 seriously injured by their action, and by the formation of a sub- 

 muriate of that metal. 



Finding that the membranous tubes were unable to resist the 

 action of the acid under the influence of high temperatures, the au- 

 thor substituted for them tubes of porous earthenware, of the same 

 texture as that of which wine-coolers are commonly made, closed 

 at their lower ends, and of the same height as the copper cells. 

 The bottoms of the latter were fitted with sockets, for the reception 

 of the tubes, and for confining them in their proper places 3 the 

 perforated copper plates, or colanders, which held the solid 

 sulphate of copper, passing over their upper ends. The tubes can 

 be easily removed, and instantly replaced ; and the facility of 

 emptying and refilling them renders the addition of siphon-tubes 

 unnecessary, except in very particular circumstances. A cir- 

 cular steam-vessel of tin plate was then provided, around which 

 the cells could be placed upon blocks of wood, and closed in with 

 a cover, containing a socket, which could, at pleasure, be connected 

 with the steam pipe of a boiler. Two other sockets were also con- 

 veniently placed, provided with cork stoppers, through which the 

 electrodes of the battery could pass, when the proper connexions 

 were made. By using this apparatus the author determined that the 

 increase of effect consequent on an augmentation of temperature is 

 but in a slight degree dependent on an increase of conducting power 

 in the electrolyte, but arises principally from its increased energy of 

 affinity, producing a greater electromotive force. 



In heating the battery by the steamer, it frequently happened that, 

 when the thermometer had nearly reached the boiling point, and 

 the action of the battery was at its maximum, a sudden cessation of 

 its action would take place ; and this suspension of power would 

 continue for hours, provided the high temperature were maintained. 

 On turning off the steam, and quickly cooling the apparatus, the 

 action would return as suddenly as it had ceased, though, generally, 

 not to the full amount. On closely examining the voltameter, on 

 these occasions, it was found that the current was not wholly stopped ; 

 but that there existed a small residual current. This residual cur- 

 rent was observed to be often directed in a course opposite to that 

 which had before prevailed ; and it was, in that case, the excess of 

 a counter current, arising from a force which was acting in the 

 contrary direction. The author found that variable currents might 

 be produced, under ordinary circumstances, from the separate single 

 cells of the battery when the whole series is connected by short 

 wires. He proved by a series of experiments that the deoxidation 

 of the oxide of copper by the hydrogen is not the exciting cause of 

 the secondary currents j but that when the course of the main cur- 



