of Natural Philosophy. 143 
pai the respect of the student for its illustrious author. 
he hypothesis of fits, however it may seem fitted to excite 
ridicule as exhibited in this scholium, is now justly regarded 
as one of the most striking displays which Newton ever 
made of his transcendant genius. In the hands of Biot 
and his companions in the career of discovery, it has ac- 
quired an importance of which Newton himself could have 
had no adequate conception.—Whether the principles of 
this now highly interesting and important department of Op- 
tics can be reduced to the level of a system of elementary 
instruction, is deserving of serious inquiry. A digest of the 
phenomena and laws of polarization, involving no difficul- 
ties which would render it inaccessible, or me ae it of its 
interest. with those who aim. at nothing more than gene 
viene of neha: appears at Teast to be as yet a desidera- 
tu 
‘Pose: 58. In all mirrors, plane or. spherical, ges” 
This proposition, in regard to spherical mirrors, is true only — 
of those pencils of cme light which are indefinitely 
near the perpendicu 
Prop. 69. In sh: iencieiuenien it is stated that “ by 
prop. 31, Hpeodinenctos of the image, when the object is" 
given, is inversely as distance of the object.” This is 
t said, in ; yohjeee 
cumstances analogous to that produced on the retina of ‘the 
eye; for the lens has no provision for preserving the image 
distinct, for different distances of the object, without vary- 
ing the distance of the plane surface which receives it. 
*rop. 73. ‘* When equal objects in the same Set i 
are seen obliquely, their apparent lengths are inversely as_ 
the squares. of their distances from the eye.” ‘The imita~ 
} J oe 
originally had as given by Rutherforth; dint 4 is, When 
equal } oben te ate very obliquely,” &e. When the ob- 
finite magnitude, the genres must be very gre 
in order that the proposition may hold true,—unless indeed _ 
the object itself be very small; in which case it holds true _ 
for every degree of obliquity. But under this last modifi- _ 
cation, it requires a different demonstration; and is more’ 
