Prof, von Kohell upon Gahanography. 225 



before mentioned, by a binding screw, are both led into a second 

 vessel filled with a solution of copper and placed opposite to each 

 other, without however being brought into contact, we shall see 

 that in this case too, a decomposition of the sulphate takes place. 

 Copper will be deposited upon the strip leading from the zinc, 

 while the sulphuric acid passes to the strip proceeding from the 

 copper and dissolves it, forming thereby fresh sulphate of copper, 

 and this action goes on till the strip is consumed. Here there- 

 fore, for reasons which it would take up too much iime to enter 

 upon, the galvanic condition of the strips is no longer the same 

 as that of the metals in the first vessel with which they are in 

 connection, and instead of the circuit, as was the case in the first 

 arrangement, being completed by means of a strip of metal con- 

 necting the copper and zinc, the circuit is here completed by the 

 fluid forming the metalline solution. It follows of necessity, 

 then, that the solution of sulphate of copper itself is possessed of 

 conducting power, and there are many other methods of proving 

 this fact. For instance, if we place a piece of glass on the bot- 

 tom of the copper vessel, connected as has been described above 

 with the zinc plate in the tamborine, and then lay a silver plate 

 upon the piece of glass, the metal plate will after a certain time 

 receive a coating of copper, and this though not in metallic con- 

 nection with either its sides or its bottom. Galvanic copper is in 

 like manner precipitated on the sides of the copper vessel, if a 

 piece of glass is laid on its bottom and on that a plate of copper 

 connected with the zinc plate in the tamborine, but not touching 

 the sides of the vessel.* 



By both these methods, plates and coats of galvanic copper 

 may be obtained, and the arrangement last described may be so 

 disposed as to admit of the deposition of the copper being ob- 

 served with facility. At first the copper deposited from the solu- 

 tion appears in the form of a reddish film upon the conductor, 

 and there is gradually formed a thin plate of a pale flesh color ; 

 by degrees the thickness of this plate goes on increasing, and 

 small nodules begin to form upon it which keep enlarging con- 

 tinually if they are not brought down from time to time by the 



' * I have sometimes observed that a portion of the side of a vessel becomes ia 

 some parts positive and in other parts negative, the portion thereof in the vicinity 

 of the connecting strip proceeding from the copper plate being corroded, and cop- 

 per being precipitated on the opposite portion. 



