(2046) 
ht Ray of the Eye was obferved to pafi not through the 
Movedhlehm the Fixed Image j thereby being conformable 
to the Rules of VJual Refraftion, as ftriking the Eye unre- 
fraiSled, fo thattheEye, the Image, arid the Objeft, were 
feen in the fame Line. But,when in the fame fcite of the Eye, 
th^ Objeft A, did alfo exhibit the other Image X, at no fmail 
diftance from the former 5 I took notice, that this Objeft A, 
was not feen unrefrafted by the means of the image X,though 
the Eye remained perpendicular over the plains and that 
confequently thisX^/f /^/«^^/Refraftionis not fubjeft to the re- 
ceived Axiome of D/^^f/r/V^r, which imports, That a Rayfal- 
Img^tt^Qudimldixly ontie fuperficks of A Di^phanoHs Body^ if 
not refra&ed^but pJjJethunr^frdUed, 
Next, I fo placed the Eye in O, that the Ray from the Obs 
arriving to the Eye, might be parallel to the lineg 
RT and CL B, of the plane R, Q^, T, B, &c. then it ap- 
pear*d, that the Rays were trajefted from the Ob jed A,witb* 
out Refradtion^ through the i^ipz/e^i/e image the Objeft 
A, the moveable image Z, and the Eye being in the fame 
line 5 and that the fame Objefl: A, did tranfmit to the Eye O, 
remaining in the fame pofition, yet another /pedes Y , through 
the Refra<9:ed Ray AYO Whence it was manifeft to 
me, that this Z^«-»/5^^/Refrafl:ion had for its Rule the Paral- 
lel of the^S'/We/of thisDouble-refraftingChryftal, while the 
Vjnal Refradion was dircded according to the Perpendknlar 
ot' the Superficies^ 
But conhdering that the place of" the point, appearing 
through our Diaphanous Body^ cannoteafily be determmd, 
as being only obvious in the uppermcft part 5 we (hall add 
the way, whereby we have found its diveriixy, by diawiog, 
on the fubjacent table.a ftraight lirif thrpngh that point 5 the. 
place of which lin^ will bw determined by the omiiye through 
this Chryftal j and by the other Eye mthout the ChryftaK 
For, in theiame if/^j^r^, let through the Ob jed: A., be drawn 
upon the Tablcja ftrait line BC* The Eye being in M, that 
double line H D, and I E, will appear, the J^eciess being 
caft O0the upperiferface : And if you attend wellj you will 
in.', obferve 
