( 173 ) 
is fcarce fo at alU yfhexthythc:tml\ht three pms ti 
me move in the diftance of the pupil of the right EyefrcMii 
the external Canthus (zs maybe judged ty the proportion 
of the l^hiie that appears) then there will be in the other ^ 
fo that the pofition ©f the right Eye in refpcd of the left 
isasiaFig. 5. 
a. TheObjeB. 
^ b. The left Eye. 
C. The right. 
-^.d. The Pupils. 
C. e. Two internal'lateraJ Fibres^ 
f . f. Two eocternal'laterah 
g. g. The optis Nerves^ 
Hereby it appears that if the Objeflbe fo placet that ir 
Is feen with both Eyes^ the r^^fe-Ey^ accommodates it felf 
to the pofition of the left^ thztthevaysfirikefoyre^onclen^ 
Fibres^ and the percuffion or Vibration being toward the 
bottom ox Papilla of the Eye (or near its Jxis) where I 
before obferv'd Fifion to be chiefly perforrifd, a fmall turning 
©f one Eye to another will make that acconunodation. 
Moreover as this accommodation is made in an oblique 
pofition of the objeflt, fo is it more readily done in a direH 
pe/ttonoiihe fzmey and this we may perceive in an Objed's 
retiring in z/lraight line from ti\e Eyes ^ whereby the Pum 
pils gradually devaricdte \ as on the contrary^ they converge 
when the Objeft is feen very near them, and that fo for- 
cibly that *tis a pain to hold them long in that pofture. 
Now by this various incidence of the rays fometimes on 
the internal and fometimes external Fibres (^according as the 
OhjtOt approaches or recedes fromm) its varyi?^ pojitionin 
refpeO: of diftance from us , is perceived> tho it recedes 
from U5 in a (Iraight Une.^ and at the fame time be equi-diftmt 
firom 
