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PRACTICAL PHOTO-MICROGRAPHY. 
Next to sunlight in intensity and in actinicity comes 
the electric arc lamp. This light has the advantages 
named, but it is somewhat awkward to use unless a 
“ bull’s eye ” or paralleliser be placed between the 
radiant and the condenser, as otherwise we shall get an 
unpleasant image of the arc on our negative when the 
condenser is properly focussed. Moreover, this light is 
apt to be very irregular in its intensity, the carbons 
never being really homogeneous throughout their length. 
The writer has had very slight experience with arc 
lamps in this connection, and such experience as he 
