AN APPARENT NEW POLARITY IN LIGHT. 
243 
wanting in every part ; and some of them, depending, as they must, on the variable 
state of the eye as to focal adjustment during the observation, cannot be obtained 
with ease or certainty. 
The train of phenomena and their related theory may be considered remarkable : 
in the first place for the apparent obscurity of the explanation, which was sufficient 
to induce an experienced philosopher to ascribe the appearances to a new property of 
light ; in the next place for the unexpected simplicity of the relation between the 
numbers which occur in the investigation, which relation contributes materially to 
facilitate the understanding of the results deduced from them ; and lastly, I may 
perhaps add, for the completeness of the explanation which the phenomenon receives 
from the undulatory theory. « 
Royal Observatory, Greenwich, 
May 30, 1 840. 
2 i 2 
