An Account of Some Cases of the Production ofColours, Not Hitherto Described. Thomas Young.

                                each particle of tallow to be, at its first evaporation, of <s>the
same<\s> such dimensions as to produce the same effect as <s>with<\s> the 
thin plate of air at this point, where it is about 
1/10000 of an inch
in <s>diameter <\s> thickness, and to reflect, or perhaps rather to transmit
the mixed light produced by the incipient combustion around it,
and we shall have a light completely resembling that which 
Dr. Wollaston has observed. There appears to be also a fine 
line of strong yellow light, separate from the general spectrum,
<s>and<\s> principally derived from the most superficial combustion at the margin 
of the flame, and increasing in quantity as the flame ascends.
Similar circumstances might undoubtedly be found in other cases 
of the production or modification of light: and <s>observations <\s> experiments upon this 
subject might tend greatly  to <s>confirm <\s> establish the Newtonian opinion, that the colour 
of all <s>substances <\s> natural bodies are similar in origin to those of thin plates,
an opinion which appears to do the highest honour to the sagacity 
of its author, and indeed to form a very considerable step in our 
advances towards an acquaintance with the intimate constitution 
and arrangement of <s>natural bodies <\s> material substances.
I have lately had an opportunity of confirming my former obser-
vations on the dispersive powers of the eye. I find that, at the respective 
distances of 10 and 15 inches, the extreme red and extreme violet 
rays are similarly refracted, the difference being expressed by a focal 
length of 30 inches: now the interval between red and yellow is about
one fourth of the whole spectrum, consequently a focal length of 120 
inches expresses <s>the<\s> a power equivalent to the dispersion of the red and yellow 
and this differs but little from 132, which was the result of the <s>former <\s>
observation already described. I do not know that these experiments 
are more accurate than the former one, but I have [repeated them 
several times under different circumstances, and I have no doubt 
that the dispersion of coloured light in the human eye is nearly 
such as I have stated it. How it happens to be no greater, I cannot 
at present undertake to explain. MDCCCII 3f 397
<s>Royal Institution 26 June 1802.<\s>
Correction of a former paper. In the Philosophical Transactions for 
1800 p.146.1.12 for 83810 read 84197; 1.13 for.0011562 read .0010116. In Fig. 53 the E6(Q) is 
too near D, and the E6(Y) should be above instead of below it.