Prof. Daniell 07i the Coiistant Voltaic Battery. 303 



which I first employed, and which is described by M. E. Bec- 

 querel, in the omissionof the siphons; which are not necessary 

 except in cases where the action is required to be maintained 

 for more than ten or twelve hours at a time. 



abed h a copper cylinder, iri whicli is placed a smaller cylinder e / of 

 porous earthenware ; upon the upper part of the copper cylinder rests a 

 perforated colander i h, through which the earthenware cylinder passes : 

 Im is a cast rod of amalgamated zinc, resting upon the top of the interior 

 cylinder by a cross piece of wood, and forming the axis of the arrangement. 

 The cell is charged by pouring into the earthenware cylinder water acidu- 

 lated with one-eighth part of its bulk of oil of vitriol, the space between 

 the earthenware tube and the copper being filled with the same acidulated 

 water saturated with sulphate of copper, and solid sulphate of copper being 

 placed in the colander. 



But, of course, the principles of the construction are inde- 

 pendent of form and materials, and are capable of application 

 to flat, square and equal surfaces of the two metals as well as 

 to concentric arrangements. They admit also of the employ- 

 ment of different metals and of different electrolytes. They 

 are not changed by placing the zinc on the outside instead of 

 the inside of the copper, nor even by altering the name of 

 " the constant battery " to that of the " sustaining battery." 



I will embrace this opportunity of observing that M. Bec- 

 querei, in his Truite de I' Electricite (tome v. livre xiv. p. 195), 

 has inadvertently committed an error affecting the history of 

 " the constant battery," in giving priority to Professor Grove's 

 experiments with the nitric acid battery over mine. He de- 

 scribes that gentleman's construction, and then proceeds, ^^Les 

 c/ioses en etaieiit Id lorsque M. Daniell a repris la question, 

 qu'il a analyse avec sagacitc. Ses recherches I'ont mis a 



