And that the Ray ef which gives a _Blue_, has
its outward part, namely, that which is contiguous to the dark side
precedent to the pulse from the innermost, which borders on the bright
_area_ of the luminous body.
We may observe further, that the cause of the _diluting_ of the colours
towards the middle, proceeds partly from the wideness of the hole through
which the Rays pass, whereby the Rays from several parts of the luminous
body, fall upon many of the same parts between c and f as is more manifest
by the Figure: And partly also from the nature of the refraction it self,
for the vividness or strength of the two terminating colours, arising
chiefly as we have seen, from the very great difference that is betwixt the
outsides of those _oblique undulations_ & the dark Rays circumambient, and
that disparity betwixt the _approximate_ Rays, decaying gradually: the
further inward toward the middle of the luminous body they are remov'd, the
more must the colour approach to a white or an undisturbed light.
Upon the calculation of the refraction and reflection from a Ball of Water
or Glass, we have much the same _Phaenomena_, namely, an _obliquity_ of the
undulation in the same manner as we have found it here. Which, because it
is very much to our present purpose, and affords such an _Instancia
crucis_, as no one that I know has hitherto taken notice of, I shall
further examine.
Pages:
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179