DOI Page / Citation link:
https://doi.org/10.11588/diglit.62828#0255
Thus the rays BP and DP, ifiiiing from the ferpentine
figure B D, are faid to converge, becaufe they unite in a point
at P, the pupil; and, after palling through the pupil and con-
tinuing in their diredt courfe, they diverge or fpread open as at
nmrqvt, on that part of the eye called the retina by which
an object is formed fimilar to the originals BD, EC, FG, and in
magnitude according to their different diftances from the eye i.
Therefore, as the fir ft objedt BD is neareft to the pupil P, the
points n t on the retina are moil extended, becaufe the angle
DPB, under which the objedt BD is feen, is confiderably larger
than thofe under which the objedts E C and F G are feen.
And again, as the fame objedt is removed back to EC, the
rays arelefs extended on the retina as at mv* but if the objedt
be removed ftill further from the fight P to F G, the rays will
ftill diverge lefs, and confequently the objedt painted on the re-
tina will be proportionably fmaller as at r q. And thus, by. re-
moving the objedt F C ftill further and further from the fight,
it would be feen under a proportionably fmaller angle, until
* Retina, from rete, a net; becaufe this part of the eye is a fine expanded membrane,
ibmewhat open like a net, and fpread over the bottom of the eye, on which are painted the
pictures of all the objects we perceive.
t 1 he refraction of the rays of light occafioned by their paffing through the different
mediums or humours of the eye, has nothing to do with perfpedtive; it belongs to optics
only, on which Fergyfon’s Lectures may be confulted, and others on the fubjeCt,
it
figure B D, are faid to converge, becaufe they unite in a point
at P, the pupil; and, after palling through the pupil and con-
tinuing in their diredt courfe, they diverge or fpread open as at
nmrqvt, on that part of the eye called the retina by which
an object is formed fimilar to the originals BD, EC, FG, and in
magnitude according to their different diftances from the eye i.
Therefore, as the fir ft objedt BD is neareft to the pupil P, the
points n t on the retina are moil extended, becaufe the angle
DPB, under which the objedt BD is feen, is confiderably larger
than thofe under which the objedts E C and F G are feen.
And again, as the fame objedt is removed back to EC, the
rays arelefs extended on the retina as at mv* but if the objedt
be removed ftill further from the fight P to F G, the rays will
ftill diverge lefs, and confequently the objedt painted on the re-
tina will be proportionably fmaller as at r q. And thus, by. re-
moving the objedt F C ftill further and further from the fight,
it would be feen under a proportionably fmaller angle, until
* Retina, from rete, a net; becaufe this part of the eye is a fine expanded membrane,
ibmewhat open like a net, and fpread over the bottom of the eye, on which are painted the
pictures of all the objects we perceive.
t 1 he refraction of the rays of light occafioned by their paffing through the different
mediums or humours of the eye, has nothing to do with perfpedtive; it belongs to optics
only, on which Fergyfon’s Lectures may be confulted, and others on the fubjeCt,
it