56 DD. Alter on Physical Properties of Light in Metals. 
Thus in the silver, there is in the orange a very bright band, 
one of yellow and one of green—two faint bands in the blue 
which are not always seen, and are probably caused by an im- 
purity in the metal. The light which is not resolved into these 
- bands is very faint except in the red. 
‘The copper has two in the orange and three in the green—the 
other light appearing most distinct in the red and yellow. In 
the zinc there is a strong band of red, two of orange and three 
of blue with a faint yellow. The lead has two bright orange, 
‘ and two in the yellow, nearer the orange than appears in the 
silver, then faint green bands and one bright violet, at the ex- 
tremity of the spectrum 
Tin has a faint red, two of orange, three faint yellow, anda 
very faint green band, and also one of blue, indigo and violet. 
[ron exhibits a bright orange, four faint green, and sometimes 
two faint blue bands. 
Bismuth a bright orange, a very faint yellow, two faint green, 
and a bright indigo. 
Antimony some bright orange, and faint appearances in the yel- 
low, green and blue. 
Brass, a compound of copper and zinc, exhibits all the bands 
that are exhibited by these metals separately, i. e. one of red, one 
of orange, three of green, three of blue, one yellow and one indig®- 
The preceding table presents these results, with some faint 
bands not above alluded to . 
To. illustrate better the manner of 
producing the sparks by the magneto- 
electric machine, I have annexed the 
following figure of the break. AandB 
represent two half circulardiscs of the 
metal intended to be used. One of 
these is connected with one end of the 
helix, and the other with the other end. 
‘They are fixed on the spindle of the re- 
volving armature, and revolve with it. jae 
They are so placed, that the extremity ¢ of the wire ¢ed—which 1s 
stationary and rubs on them—is passed from the one to the other at 
the same time that the armature is passing the poles of the magnets: 
In order to produce sparks, the end d of the wire is caused to rub 
on the discs, nearly opposite C—which causes a bright spark at — 
each half revolution of the armature. Ae 
When the discs are of zinc, and the extremity d of the wire — 
is of copper, the bands are the same as in also if the 
discs are of copper, and the wire zinc. When the discs and wire 
are both of copper, after having used a wire of zihc on the discs — 
—they will still exhibit the same colored bands as the brass, u0- 
til all the zinc left by the friction is removed, when the charac: 

teristic bands of the copper alone appear. 

