162 Mr. Knox on some phenomena of colours , 
reflection of the rays of light, is now generally admitted ; nor 
does it appear that any other more satisfactory, has yet been 
adopted in its stead. 
This will not be thought surprising, if it shall appear by 
the following experiments, that neither Newton, nor any 
other writer that has followed him in the same line, has been 
in possession of all the phenomena connected with this curious 
and intricate subject. 
I was induced to make the following experiments in conse- 
quence of having lately read Dr. Herschel’s excellent paper 
on the same subject, published in the 95th vol. of the Philoso- 
phical Transactions, in which he has related a great number 
of experiments, explaining a variety of phenomena relative to 
prismatic rings ; and must acknowledge my obligations to 
this celebrated author, for his simple but ingenious contri- 
vance of viewing prismatic phenomena by means of the sha- 
dow of a- black card; without which, it is probable the fol- 
lowing discoveries, such as they are, would not have been 
made. 
Exp. 1. On repeating some of the experiments mentioned 
by Dr. Herschel in vol. 95 of the Philosophical Transactions, 
and having by means of the shadow of a blackened card per- 
ceived no less than eight sets of rings in some cases, and 
being very attentive in endeavouring to distinguish transmitted 
from reflected sets, I faintly saw parallel lines or streaks, 
which at first were mistaken for the threads of a piece of 
black silk which was placed under the lower glass, in order 
to see the rings more distinctly. It was not until after 
repeated examinations by the light of a lamp, in which the 
direct light is shaded from the eyes, that it was ascertained. 
