so numerous, for the most part exceeded not the third Part of a Circle.
If the Refraction was very great, or the Prism very distant from the
Object-glasses, the middle Part of those Arcs became also confused, so
as to disappear and constitute an even Whiteness, whilst on either side
their Ends, as also the whole Arcs farthest from the Center, became
distincter than before, appearing in the Form as you see them design'd
in the fifth Figure.
The Arcs, where they seem'd distinctest, were only white and black
successively, without any other Colours intermix'd. But in other Places
there appeared Colours, whose Order was inverted by the refraction in
such manner, that if I first held the Prism very near the
Object-glasses, and then gradually removed it farther off towards my
Eye, the Colours of the 2d, 3d, 4th, and following Rings, shrunk towards
the white that emerged between them, until they wholly vanish'd into it
at the middle of the Arcs, and afterwards emerged again in a contrary
Order. But at the Ends of the Arcs they retain'd their Order unchanged.
I have sometimes so lay'd one Object-glass upon the other, that to the
naked Eye they have all over seem'd uniformly white, without the least
Appearance of any of the colour'd Rings; and yet by viewing them through
a Prism, great Multitudes of those Rings have discover'd themselves. And
in like manner Plates of _Muscovy_ Glass, and Bubbles of Glass blown at
a Lamp-Furnace, which were not so thin as to exhibit any Colours to the
naked Eye, have through the Prism exhibited a great Variety of them
ranged irregularly up and down in the Form of Waves. And so Bubbles of
Water, before they began to exhibit their Colours to the naked Eye of a
Bystander, have appeared through a Prism, girded about with many
parallel and horizontal Rings; to produce which Effect, it was necessary
to hold the Prism parallel, or very nearly parallel to the Horizon, and
to dispose it so that the Rays might be refracted upwards.
THE
SECOND BOOK
OF
125