see their several opinions at large set forth and confuted, not without
some surprize at the gross blunders that ingenious men have been forced
into by endeavouring to reconcile this appearance with the ordinary
Principles of optics. Since the writing of which there hath been published
in the TRANSACTIONS [Numb. 187. P. 323] another paper relating to the same
affair by the celebrated Dr. Wallis, wherein he attempts to account for
that phenomenon which, though it seems not to contain anything new or
different from what had been said before by others, I shall nevertheless
consider in this place.

76. His opinion, in short, is this; we judge not of the magnitude of an
object by the visual angle alone, but by the visual angle in conjunction
with the distance. Hence, though the angle remain the same, or even
become less, yet if withal the distance seem to have been increased, the
object shall appear greater. Now, one way whereby we estimate the
distance of anything is by the number and extent of the intermediate
objects: when therefore the moon is seen in the horizon, the variety of
fields, houses, etc., together with the large prospect of the wide
extended land or sea that lies between the eye and the utmost limb of the
horizon, suggest unto the mind the idea of greater distance, and
consequently magnify the appearance. And this, according to Dr. Wallis,
is the true account of the extraordinary largeness attributed by the mind
to the horizontal moon at a time when the angle subtended by its diameter
is not one jot greater than it used to be.

77. With reference to this opinion, not to repeat what hath been already
said concerning distance, I shall only observe, FIRST, that if the
prospect of interjacent objects be that which suggests the idea of
farther distance, and this idea of farther distance be the cause that
brings into the mind the idea of greater magnitude, it should hence