200 TROWBRIDGE. — HIGH ELECTROMOTIVE FORCE. 
process of printing by transmitted light. In many cases one can rest content with 
under exposures, feeling confident that good reproductions can be obtained by this 
method. Of course there is a certain amount of distortion on account of the an^le 
of reflection, but this can be reduced to a minimum along certain lines which contain 
the part of the image which is the chief characteristic one seeks to show. 
By suitably staining the plate with a yellow dye one can also place the negative 
such a position in intense sunlight that the silver deposit, instead of reflecting 
brighter image than the background or rest of the plate which contains no foo- 
image, reflects less light, and therefore appears black in sunlight. In this case 
one obtains in the camera a positive. This positive often reveals details which are 
not seen by transmitted light, and moreover gives them in strong contrast with the 
background or remainder of the plate. 
Figure 8, Plate XXVI, shows two striking phenomena. The first is this : at every 
fork or zigzag along the path of the discharge there is a side discharge. These side 
discharges are directed toward the cathode. Moreover, each of these side discharges 
forks or bifurcates in the same manner; that is, they arise at the forks. 
In the case of very long sparks, six feet or more, the bifurcations are generally 
directed to neighboring conducting masses, and are not directed to the cathode. In 
the case of lightning, masses of clouds at a low potential, not lying along the main 
direction of discharge, are indicated bv these side forking discharges. 
^ The second marked phenomenon is a brush discharge, exactly similar to the brush 
discharge at the anode before the disruptive spark occurs, at every fork or chai 
of direction of this disruptive discharge. 
Thus the peculiarities of the positive pole or anode are seen at every point of 
i 
o 
disruptive discharge, especially wh 
between many cathodes. This 
choice can occur when the anode is a point and the cathode is an arc of 
from the point of the anode as a centre, the arc beino- provided 
points. This bifur 
observer to 
with several spurs 
g discharge, and it leads 
direction of the lightning discharge 
disruptiv 
stretching out as it does like the fingers of a poin 
Since the characteristics of the positive pole a 
discharge, one cannot help thinking that these c 
superior momentum of the positive electron Tn «., „ i ,u -J> " V 7 'i 
o m . M „ •„ ,_ A . electron, in general the positive electron play 
1 phenomena ; but in the disruptive spark there is someth 
to speak 
of the positive pol 
positive electron ? — which 
pletely overshadows the manifestation nP+k^ ~ 
IesUtlon of the negative electron. We can consid 
th 
