
4 When the hair approached so near to the direction of the mar- gin of a candle that the <s>light reflected from or very obliquely <\s> inflected light was sufficiently. <s>and therefore expressly [?], could reach the eye <\s> copious to produce a sensible effect, the fringes began to appear, and it was easy to estimate the proportion of their breadth to <s>that of <\s> the apparent breadth of the hair, across the image of which they extended. I found that six of the brightest red fringes, nearly at equal distances, occupied the whole of that image. The breadth of the aperture was 66/1000, and its distance from the hair, 8/10 of an inch; the diameter of the hair was less than 1/500 of an inch; as nearly as I could ascertain, it was 1/600. Hence we have [11/1000 for the deviation of the first red fringe at the distance 8/10, and as 8/10:11/1000::1/600:11/480000, or] 1/43636 for the difference of the routes of the <s>redlight <\s> red light where it was most intense. The measure deduced from Newtons experiments is 1/39200. I thought this coincidence, with only an error of one ninth of so minute a quantity, sufficiently perfect to warrant com- pletely the explanation of the phenomenon, and even to render a repetition of the experiment unnecessary: for there are several circumstances which make it difficult to calculate much more precisely what ought to be the result of the <s>admeasurement <\s> measurement. When a number of fibres of the same kind, as, for instance, a uniform lock of wool, are held near to the eye, we see an appearance of halos surrounding a distant candle; but their brilliancy, and even their existence
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Manuscript details
- Author
- Thomas Young
- Reference
- L&P/12/32
- Series
- L&P
- Date
- 1800
- IIIF
-
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Cite as
An Account of Some Cases of the Production ofColours, Not Hitherto Described. Thomas Young., 1800. From The Royal Society, L&P/12/32
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