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.
Please login to transcribe
An Account of Some Cases of the Production ofColours, Not Hitherto Described. Thomas Young., 1800. From The Royal Society, L&P/12/32
Please login to comment