On Electric Phenomena. 19 



^'avant la lettre" are so much in request. But now tlie plates 

 Avliich have been engraved by the artist can be several times 

 galvanically imitated, and a great number of impressions taken 

 from them, while the original plate remains quite uninjured, 

 whereby naturally the number of the good impressions is in- 

 creased, and their price becomes much more reasonable. In 

 the same manner we deal with forms cut in wood for wood- 

 engravings.^ or other purposes, in short, with all objects which 

 are used in great numbers, in the same form, for example, 

 government seals, forms to press decorations in leather etc. 



Another phase of electro-metaUurgy consists in furnishing 

 objects with a metallic coating in a galvanic manner. Thus 



\ ^e can electro-plate all objects by connecting them with the 



; -chain of the negative pole, and putting them into a solution 

 of muriate of gold, silver, or sulphate of iron, and then ex- 



\ posing them to the influence of the electric current. Galvanic 

 steeling is sometimes undertaken with copper-plates, to give 

 them a greater hardness, and thereby greater power to resist 

 the pressure of the printing-press. A very thin precipitation 

 of a metal, which changes into different colours through the 

 reflection of the hght, is used to decorate bells for the table 



\ and other metallic objects. 



If we conduct the current of the chain through the above 

 described vessel, in which the water is decomposed through 

 two metal plates, while the developed inflammable gas is trans- 

 ported through a covered glass-tube into a bell, we can mea- 

 sure the quantity of inflammable gas, which is developed in a 

 given time. If we put at the same time the multiplicator in 

 the circuit of the chain, we shaU find, that the quantity of 

 inflammable gas, which is developed, is so much larger or 

 smaller, according to the deviation of the magnetic needle. 



(141) 



