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nomena ; and was thus led to discover the cause of the variations 

 and progressive decline of the power of the ordinary voltaic battery, 

 one of the principal of which is the departure of the zinc on the 

 platina plates 3 and to establish certain principles from which a 

 method of counteracting this evil may be derived. The particular 

 construction which he has devised for the attainment of this object, 

 and which he denominates the constant battery, consists of a hollow 

 copper cylinder, containing within it a membranous tube formed by 

 the gullet of an ox, in the axis of which is placed a cylindrical rod 

 of zinc. The dilute acid is poured into the membranous tube from 

 above by means of a funnel, and passes off, as occasion requires, by 

 a siphon tube at the lower part 3 while the space between the tube 

 and the sides of the copper cylinder is filled with a solution of sul- 

 phate of copper, which is preserved in a state of saturation by a 

 quantity of this substance suspended in it by a cullender, allowing 

 it to percolate in proportion as it is dissolved. Two principal objects 

 are accomplished by this arrangement ; first, the removal out of the 

 circuit of the oxide of zinc, the deposit of which is so injurious to 

 the continuance of the effect of the common battery ; and, secondly, 

 the absorption of the hydrogen evolved upon the surface of the 

 copper, without the precipitation of any substance which would lead 

 to counteract the voltaic action of that surface. The first is com- 

 pletely effected by the suspension of the zinc rod in the interior 

 membranous cell into which fresh acidulated water is allowed slowly 

 to drop, in proportion as the heavier solution of the oxide of zinc 

 is withdrawn from the bottom of the cell by the siphon tube. 

 The second object is attained by charging the exterior space sur- " 

 rounding the membrane with a saturated solution of sulphate of 

 copper, instead of diluted acid ; for, on completing the circuit, the 

 electric current passes freely through this solution, and no hydrogen 

 makes its appearance upon the conducting plate ; but a beautiful 

 pink coating of pure copper is precipitated upon it, and thus perpe- 

 tually renews its surface. 



When the whole battery is properly arranged and charged in this 

 manner, it produces a perfectly equal and steady current of electri- 

 city for many hours together. It possesses also the further advan- 

 tages of enabling us to get rid of all local action by the facility it 

 affords of applying amalgamated zinc ; of allowing the replacement 

 of the zinc rods at a very trifling expense ; of securing the total 

 absence of any wear of the copper; of requiring no employment of 

 nitric acid, but substituting in its stead materials of greater cheap- 

 ness, namely, sulphate of copper, and oil of vitriol j the total ab- 

 sence of any annoying fumes 5 and lastly, the facility and perfection 

 with which all metallic communications may be made and their ar- 

 rangements varied. 



