the Discharge of a Leyden Jar. 165 
tors, inclosing between them a white sector of equal breadth, 
are painted on a white circular dise of card-board, and viewed 
in a mirror through an uperture cut in the same disc, when it 
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Instead of using only two lines, the same result can far more 
easily be attained by ruling paper with a large number of fine 
black lines, equidistant, and inclosing white spaces of their own 
oth 
i d a glass plate with lamp- 
ecordingly I covered a gla oa a nebo 
like a slight cement, enabled me to rule lines on 
i i Afte trials and micro- 
magn : 
ed that the breadth of the 
zs of a millimeter. 
time required for their obliteration, with a velocity 
