of the Hair is much broader in proportion to the distance of the Paper
from the Hair, when the Paper is nearer the Hair, than when it is at a
great distance from it.
_Obs._ 2. The Shadows of all Bodies (Metals, Stones, Glass, Wood, Horn,
Ice, &c.) in this Light were border'd with three Parallel Fringes or
Bands of colour'd Light, whereof that which was contiguous to the Shadow
was broadest and most luminous, and that which was remotest from it was
narrowest, and so faint, as not easily to be visible. It was difficult
to distinguish the Colours, unless when the Light fell very obliquely
upon a smooth Paper, or some other smooth white Body, so as to make them
appear much broader than they would otherwise do. And then the Colours
were plainly visible in this Order: The first or innermost Fringe was
violet and deep blue next the Shadow, and then light blue, green, and
yellow in the middle, and red without. The second Fringe was almost
contiguous to the first, and the third to the second, and both were blue
within, and yellow and red without, but their Colours were very faint,
especially those of the third. The Colours therefore proceeded in this
order from the Shadow; violet, indigo, pale blue, green, yellow, red;
blue, yellow, red; pale blue, pale yellow and red. The Shadows made by
Scratches and Bubbles in polish'd Plates of Glass were border'd with the
like Fringes of colour'd Light. And if Plates of Looking-glass sloop'd
off near the edges with a Diamond-cut, be held in the same beam of
Light, the Light which passes through the parallel Planes of the Glass
will be border'd with the like Fringes of Colours where those Planes
meet with the Diamond-cut, and by this means there will sometimes appear
four or five Fringes of Colours. Let AB, CD [in _Fig._ 2.] represent the
parallel Planes of a Looking-glass, and BD the Plane of the Diamond-cut,
making at B a very obtuse Angle with the Plane AB. And let all the Light
between the Rays ENI and FBM pass directly through the parallel Planes
of the Glass, and fall upon the Paper between I and M, and all the Light
between the Rays GO and HD be refracted by the oblique Plane of the
Diamond-cut BD, and fall upon the Paper between K and L; and the Light
which passes directly through the parallel Planes of the Glass, and
falls upon the Paper between I and M, will be border'd with three or
more Fringes at M.
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
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