OP GALVANIC APPAEATUS. 



179 



FIG. 2106. 



FIG. 2099. 



FIG 2103. 



2 5 

 10 

 3 5 



2090. A SET OF six CELLS, as No. 2089, in stout wooden tray . 



2092. SECOND SIZE, with iron cell, 7 inches long by 6| deep, and If wide 



2093. A SET OF six CELLS, as above, in stout wooden tray 



2094. DR. CALLAN'S MAYNOOTH BATTERY. 



For the Maynooth battery, as above, it is said that the most effective solutions are 

 a mixture of equal parts of concentrated nitric and sulphuric acids for the iron cell, 

 and a mixture of 2 parts of sulphuric and 1 of nitric acid with 18 parts of water for the 

 zinc cell. 



This battery is said to be far more powerful than Groves's, see Brooks's " Natural 

 Philosophy, 1867," page 434, price rather lower than No. 2089. 



2095. MANGANESE BATTERY. 



The porous cell that contains the plate of carbon is filled up with a pulverized 

 peroxide of manganese and water, the porous cell stands in a glass cylinder containing 

 a stout zinc rod, and a solution of sal-ammoniac in water, quart cell . 046 



This battery is said to continue in constant action for one year, having a little 

 water occasionally put to it ; it is much used for telegraphs, especially in houses, as it 

 gives off no fumes. 



Davy's Sulphate of Mercury Battery, in which the acid of the carbon cell is 

 replaced by a paste of powdered sulphate of mercury and water, and the 

 dilute acid of the zinc cell by water only ; it is very constant, and its power 

 is 1 times that of Daniell's. Much used in France for telegraphy : 



2097. SMALL SIZE, 2s. 6d. ; larger size consisting of a pint glass bottle (square) with a 

 carbon plate, zinc rod, and fittings complete . . . 056 



ELECTRO-METALLURGICAL APPARATUS. 



Electrotype apparatus, extensively used for obtaining by voltaic action exact copies 

 of medals and plaster casts, ancient and modern, as well as fac-similes of engraved 

 copper plates, wood engravings, etc. 



2098. Electrotype Apparatus, consisting of glazed earthenware jar, porous pot, zinc 



rod, and wire for mould, pint size, 2s. 6d. ; quart size . 036 



2099. SINGLE CELL APPAEATUS (Jig. 2099), very convenient in form and simple in 



operation, with porous cell, zinc plate, wire and binding screw, suitable for 

 copying medals, seals, plaster casts, etc., 5s. 6d., 7s. 6d., and . 10 6 



