( 3046 ) 
enters into Glafs, is about a third part of the Angle of the 
laelination of the ray paffing into the Air : But thac the fame 
Inelination not exceeding 30 degrees^ the Angle of the re- 
fraction of the ray iffuing out of the Glafs into the Air j 
is about the half of the ^Angle of its Inclination in the 
Glafs. 
Examining, what the Diffeftion of an Eye may conduce to 
the knowledge of the Refractions of its Humors, he noteth, 
That the Extiu<3:ion of the vital fpirits in a dead Animal doth 
extreamly alter the confiftence of the Humors of his Eye, 
which contributed much to the perfed vifion in the living 
animal ; And that all the Experiments, that can be made by 
diffeCling of Eyes , to come to the knowledge of the Re* 
fractions of the Humors , and of the other parti that con* 
duced to Vifion, cannot give the true knowledge thereof > 
Experience proving, that the Chriftallin and Vitreous humors 
do reciproqually change their confiftence* 
^ He obferveth alfo, that not only the different Diaphanei- 
ties of the Humors of the Eye do contribute to the refraClion 
of the vifualrayspa{Engthorowthem5 but alfo the Figures^ 
of their Surfaces^ on which thofe rays fall unequally inclined. 
He noteth likewife , that the vifual rays^ having penetrated 
the Corneous tunique and the Aqueous humor of the Eye, 
do not fuffer any great refraCtions upon the Anterior (urfsiCQ 
of the Chryftallin, though it be finer than the Aqueous hu^ 
mor^ becaufe that its Spherical convexity is con-centrique 
to that of the Cornea ana of the Aqueous humor 5 which are 
likewife fpherical : But that they receive their greateft re- 
fractions , when they pafs through the Pofierior furfacc of 
the Chryftallin , which is oppofite to them , and of a 
very fmall Sphere, and upon which they are found much 
inclined. 
He taketh further notice, That the furfaces of the Chry- 
ftallin humor are not Hyperbolical but perfeCtly Spherical $ 
and that the exadnefs 3 which by that means is pretended 
for VifioHj is contrary to Experience, by which he afferts it 
to be undeniable^ that, though by Glaffes of an hyperboli* 
