226 
Proceedings of the Royal Society of Edinburgh. [Sess. 
that and the card all is dark. The rays from the + (spherical) electrode 
have the peculiarity of lying entirely in one horizontal plane : they, too, 
after bridging about one-half the gap between card and electrode, vanish 
abruptly, the end of the discharge being perfectly straight and regular. If 
now the card be moved slowly towards the anode, a change takes place in 
the character of the brush. Fig. viii. is a side view showing that change. 
At a certain stage in the motion, the horizontal brush suddenly splits into 
two brushes, each uniplanar ; and as the card continues to approach, these 
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continue to diverge, each making at any time the same angle as the other 
with the plane of the electrodes. 
Many varieties of these experiments can be designed by making holes 
at various points in the plates between or outside the electrodes, or by 
bending the plate itself into various shapes. An instance of this last is 
