390 Prof. W. B. Rogers on Binocular Vision. 
momentary illumination of the electric flash, furnish a further 
d most powerful argument against the theory of successive 
binocular combination here referred to. 
In repeating these I have found great advantage in using one 
of Ritchie’s improved Ruhmkorff coils having a coated j 
included in the outer circuit, the intensely brilliant spark of 
which can be made to throw its light upon the object viewed in 
any direction or at any interval that may be desired. 
When a twin-diagram of any simple geometrical solid was 
placed in the stereoscope and viewed by this momentary light it 
was found to exhibit the perspective resultant in most cases with 
a single spark, and it never failed to present it in perfection with 
. succession of sparks even when they followed each other 
slowly. 
corresponding points j;—and second, that for the singleness pile 
dso p 
as to be identical with the pictures which the real object would 
€ at a given distance and in a given altitude before the ey 
