extraordinary Appearance in a Mijl. 1 6 1 
that exhibit the ordinary bow. This muft be owing to 
fomething peculiar in the mill, as to the form, fize, 8cc. 
of its particles or globules; eafier to conceive than explain. 
In the valuable Treatife of Optics by the laft named gen- 
tleman, there is an account of Dr. Pemberton’s theory 
for the llender rings of colours, which are fometimes 
feen within the rainbow, which Dr. langwith firft de- 
fcribed in the Philofophical Tranfadtions and from 
which fome idea may be formed of the caufe of the Co- 
loured part of the image. It is in fubftance this (f> . If 
the drops of rain, &x. which the fun fhines upon be ex- 
ceedingly fmall, from the irregular reflection of all fur- 
faces, and the fits of eafy tranfmiffion, which the difli- 
pated rays may undergo in their paffage through thofe 
little globules, there may naturally be formed other co- 
loured arches within the common bow for a number of 
fucceffions. Hence, with regard to the inftance in quef- 
tion, iince its rings were fo very fmall in diameter, it ap- 
pears, that on fome account or other the refradted, co- 
loured, and diffipated rays alluded to, have in their re- 
turn to the eye nearly made the fmalleft angles poffible 
with the lines of incidence. 
0 ) N® 375. 
(f) See Articles 506, 507. 
Vox.. LXX. 
Y 
After 
