A. W. Wright—Electrical Deposition of Metals, 175 
the plate by an interval of only one or two millimeters. This 
had the effect to cut off the lateral portion of the discharge, 
and to confine its action to a limited area immediately below 
the extremity of the wire. : 
The yellow tarnish is removed with the greatest ease by 
gently rubbing the surface with soft chamois leather and a little 
rouge, and the metal is so hard, that, when this operation is 
performed with care, the polish is not at all, or but very 
slightly, affected. Even then, however, the metal is not per- 
fectly white, having still a very faint yellow tinge. It is well 
known that silver is not a perfectly white metal, for light which 
has undergone repeated reflections from polished surfaces of 
this metal appears yellow or reddish-yellow, though this color 
is not perceptible when the light has undergone but a single 
reflection. But the real cause of the yellowish tint may possi- ’ 
bly be found in the very tenuity of the films, which when pre- 
pared in this way have a beautiful and intense blue color by 
transmitted light. When not too thick, the amount of blue 
rays which they suffer to pass, may be sufficient to cause, by 
their abstraction, a perceptible tinge of yellow, the complimen- 
tary color, in the reflected rays. If this were really the case, 
the coloration should grow weaker with an increase of thick- 
ness, and disappear when opacity is reached. Some of the 
results areas seem to favor this view, and the probability of 
its correctness is strengthened by the facts related in the next 
ragraph, but further experiments are needed to decide the 
question satisfactorily. 7 
ne result of the investigation has been to show that the 
color of the light which has passed through a layer of metal 
varies somewhat with the thickness of the film. is was 
ulated by observing the color of the transmitted light. An 
experiment made with a circular disk of flat glass was perfectly 
successful, the platinum being readily deposited upon the sil- 
ver, the yellowish tint of which it entirely removed, producing 
