aa 3 
306 T. W. Backhouse—Physiological Optics. 
learned if based on some anatomical or mathematical fact than 
if there were no such basis to go upon; and therefore it seems 
to me that there must be such a basis, and that it is conse- 
quently very improbable that the theory of corresponding 
points can be incorrect. Nevertheless, the facts he gives in 
volume xxiv, page 241, etc., and page 331, etc., perhaps point 
tance pretty well 
not otherwise. ‘ 
that there must always be th 
