on the Mechanism of the Eye. 
% 
lity of such persons to change the refractive state of the organ. 
Eighthly, to deduce, from the aberration of the lateral rays, 
a decisive argument in favour of a change in the figure of the 
crystalline; to ascertain, from the quantity of this aberration, 
the form into which the lens appears to be thrown in my own 
eye, and the mode by which the change must be produced in 
that of every other person. And I flatter myself, that I shall 
not be deemed too precipitate, in denominating this series of 
experiments satisfactorily demonstrative. 
Page 28, line 11, Prop. III. after e, insert the base being unity. 
Page 30, line 8, Cor. 10. for n t u, read ntt ; line 9, for product Sec. read square 
of the cosine of incidence. 
Page 3 1, line 5, Cor. 1 1 . for 1 + w 2 — 2 a*, read 2 mu u. 
Page 31. Prop. V. Cor. See the note in p. 60. 
Page 33 - Prop. VIII. By a mistake of a sign, the eighth proposition is rendered 
erroneous ; no use having been made of that proposition, it has been inserted without 
proper revision. It ought to stand thus, with its demonstration : 
To find the path of a ray of light falling obliquely on a sphere, of a refractive 
density varying as any power of the distance from the centre. 
The refractive density, in the sense of these propositions, varies as the ratio of the 
sines, and as the velocity of light in the medium. (Schol. 2. Prop. I.) Let the velo- 
1 
city at the distance „r be x r ; then, considering the refractive force as a species of 
1 
attraction, we have, in Prop. 41. 1 . 1. Princip. ^/ABFD=ar r , s, the sine 
of incidence, the radius being unity, Z = s x , Dc = — - — 
CORRECTIONS. 
Proposition VIII. Problem 
, and the fluxion of the area described by the radius 
Let the sine of the inclination to the radius 
M 2 
