PHILOSOPHICAL 
TRANSACTIONS. 
X. On some phenomena of colours , exhibited by thin plates. By 
John Knox, Esq. Communicated by the Right Hon. Sir Joseph 
Banks, Bart. G. C. B. P. R. S. 
Read April 6, 1815. 
It is not without reason that the phenomena of light have 
been subjects of speculative enquiry from the earliest ages of 
philosophy ; since perhaps no study can be more interesting 
to the inquisitive mind, than the contemplation of that medium 
through which it receives its most exalted enjoyments. 
There are probably no appearances in physical optics that 
have excited more attention, and that have been less satisfac- 
torily accounted for, than those prismatic concentric rings 
which appear between lenses, or between a flat glass and a 
lens, when laid together. And, notwithstanding some of the 
most eminent philosophers and opticians have given explana- 
tions thereof, particularly Sir Isaac Newton and Dr. Her- 
schel, it will appear from what follows, that the subject is 
far from being exhausted. 
The insufficiency of Newton’s theory for the solution of 
this problem, by the supposed fits of easy transmission and 
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