158 O. N. Rood on the discharge of a Leyden jar. 
(c) With fine platinum wires. The’appearance was the same 
as the last, except that the green tint was replaced by a grey 
or violet-grey hue. These observations were made with a mir- 
ror of plane glass, the rear side being blackened, which reduced 
the intensity of the light adequately for the purposes of dis- 
tinct vision. The ground glass was replaced by a polished 
plate, which supported an eye-piece magnifying five diameters. 
Appearance presented by the revolving mirror. 
(a) With brass balls as electrodes. With a “striking dis- 
tance” of one or two millimeters, the image being thrown on 
the ground glass and viewed by the naked eye, it was found 
that the spark was drawn out into a streak one and a half or 
3. two inches long, according to the rate of the mirror ; 
w the portion at W, (fig. 3) was white; this shaded 
px into a brownish yellow tint, (B Y) the latter passing 
into a pretty distinct green, (G.) It will be foun 
« comparison that this result is exactly that obtained by 
Feddersen with frictional electricity, except that in 
my case the green color of the tail seems to have been 
: much stronger, which is explained by the lower inten- 
__ sity of the illumination. 
With the unaided eye and ground glass, nothing additional 
of a remarkable character could be discerned, but on using the 
polished plate of glass and an eye-piece magnifying five diam- 
eters, a series of bright dots on each side of the streak became 
visible in the positions indicated by the dots in figure 3. 
These resemble the photographs obtained by Feddersen with 
frictional electricity. Here it is seen that the bright points be- 
ore spoken of, correspond to a series of discharges following 
the first. 
(6) With platinum points. Using the ground glass, I found 
that the form of the streak was some times identical with that 
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