204 W. B. Rogers on Binocular Vision 
Art. XX.—Observations on Binocular Vision ; by Professor 
Wituiam B. Rocers. 
PART SECOND. 
Conditions under which two or more right lines are optically 
. united. 
form a simple binocular resultant, and I have shewn that this 
is not confined to experiments like those with the sliding-stage 
apparatus, but occurs, although to a less extent in the use of the 
common stereoscopes. The observations which I am about to de- 
scribe have been made chiefly with the former instrument because 
of the facility it affords for multiplying and varying the experi- 
ments and because after a little practice it enables us to obtain the 
Brewster and on which they have published differing views. The 
nt 
combination of pairs of corresponding points’ in the two draw- 
the interpretation. While these enquiries have in many respects 
satisfied me of the correctness of the views of these philosophers, 
they have led me to regard in a different and somewhat new as- 
pect certain parts of the process of binocular vision involved it, 
the questions above alluded to. 
6. Of the combination of parallel right lines either vertical of 
oblique. ' 
‘Two equal parallels (fig. 9 or fig. 10), when placed on the 
Upper stage of the stereoscope may be united in a position far- 
ther from the eyes than their true place, or when adjusted on the 
