CHAP, ix.l ELECTRO-PLATING. 711 



the vase in Fig. 458. By the process of which we have just given an 

 outline, the modelling of the most beautiful, as well as the largest, 

 statuary works has become possible. Statues two metres high and 

 even up to 4J metres, for the new opera hall, have been moulded by 

 electricity with a perfection not to be surpassed by the ancient art of 

 casting. A statue of 9 metres weighing 3500 kilograms has been 

 made in the same way. The thickness of the copper is not less than 

 4J mm., but it took no less than two months and a half to bring this 

 operation to a close. These remarkable works have been executed by 

 a large manufacturing house in France, Messrs. Christofle and Co. M. 

 Oudry has reproduced in copper by electro- typing, the bas-reliefs com- 

 posing the column of Trajan ; these bas-reliefs, 600 in number, have 

 each on an average an area of a square metre; so we see by the impor- 

 tance of this work that the art of electro-typing, so remarkable for the 

 fidelity and perfection of its productions, has become in the hands of 

 inventors and manufacturers, an industry of truly great importance. 



III. GALVANIZING. GOLD AND SILVER PLATING. 



The principle on which gold and silver plating depends, and in 

 general the deposit of a metal in a thin adherent layer on the surface 

 of an object, is the same as that of electro-typing. It is always the 

 electrolytic property of a galvanic current, which in passing through a 

 solution of gold or silver, &c., decomposes it, and sets free the metal at 

 the negative pole. 



But, though the principle is known, there still remain practical 

 difficulties to be overcome ; the conditions of adhesion of the deposit 

 must be determined, the best composition of the bath discovered, and 

 the best method of preparation of the objects to be plated. We have 

 seen that the first really applicable processes of gold and silver plating 

 are due to Messrs. Wright and De Ruolz. 



The apparatus employed, whether simple or compound, are the 

 same as we have described under electro-typing. The preparation oi 

 the object consists principally in cleaning the surface, which ought to 

 be perfectly cleared from every foreign substance. If the object is in 

 bronze it must be brought to a red heat. If in brass it must be 

 washed with a concentrated solution of soda, but there always remains 



