312 M. Nobili on New Electro-Chemical Phenomena. 



was of a clearer tint. These colours are those of the copper 

 in the state of oxide, and in the metallic state. A stratum of 

 nitric acid passed slightly over the disc, attacked these differ- 

 ent circles. Those formed by the oxide of copper disappear- 

 ed almost entirely, and that which was formed by the copper 

 remained. Four or Jive circles were sometimes formed instead 

 of three, and the tints alternated as in the preceding case. 



Upon a disc of Brass Positive, (that is communicating with 

 the positive end of the pile,) there are several different concen- 

 tric figures, which, when they are wiped with linen, leave upon 

 it traces oi five concentric circles of a clear brass yellow co- 

 lour, Some are clearer than others, and alternate with them. 



Upon Brass Negative there is a deposit of copper, and 

 circles of two alternating shades, as in silver. 



No distinct effects were obtained either with discs of platina, 

 tin, or bismuth. 



Sulphate of Zinc. — Upon Silver Positive there was a 

 spot dark at the centre ; then a clear yellow circle ; then a 

 circle of light blue ; and then a fine zone, approaching to yel- 

 low. 



Upon Brass Positive there were four small circles proceed- 

 ing from the copper. They have two tints, one clearer than 

 the other, and alternating. These tints seem to be those 

 which distinguish copper in the state of oxide from copper in 

 the metallic state. 



Sulphate of Manganese. — Upon Silver Positive there ap- 

 pear five concentric circles, alternately bright and dark. The 

 fifth is more distinct than the rest, and is surrounded with an 

 area of a pale yellow, which terminates in a violet tint. 



Upon Brass Positive there are five small circles, alternate- 

 ly bright and dark. 



On Bismuth Positive there are four circles. The smallest 

 is white, the second darker, the third a pale yellow, and the 

 fourth black. 



Nitrate of Bismuth. — On Gold and Silver Negative 

 there are four or five concentric circles differently coloured, but 

 not distinct. The tints of these circles appear to be those through 

 which the bismuth passes in its oxidation. 



Acetate of Lead. — On Gold and Platina Positive. In 



