Elements of natural philosophy (Volume 2-3) . nding to the color seen alongthe line EC\ AKC may be regarded as a right angledtriangle, and the angle C A K as equal to the angleA EC, which is the angular distance of the particularcolor in question from the luminous source. And de-noting the sum of the widths of a single transparentand furrowed part by $, and the angle A E C by D,we find X = S. sin D. Same indifferent terras. And because the angle D is exceedingly small, its arcwill be sensibly equal to its sine, and the above may be written \= (85) ELEMENTS OF OPTICS. 273 From which it appea
Elements of natural philosophy (Volume 2-3) . nding to the color seen alongthe line EC\ AKC may be regarded as a right angledtriangle, and the angle C A K as equal to the angleA EC, which is the angular distance of the particularcolor in question from the luminous source. And de-noting the sum of the widths of a single transparentand furrowed part by $, and the angle A E C by D,we find X = S. sin D. Same indifferent terras. And because the angle D is exceedingly small, its arcwill be sensibly equal to its sine, and the above may be written \= (85) ELEMENTS OF OPTICS. 273 From which it appears that D will be greater in pro- colorsportion as X is greater; and that the colors of each ZlZZZl *fringe which correspond to the longest waves will, there- furthest fromfore, be found at the greatest distance from the lumin-luminous s°urceous source. To find X, we have only to find S and D. The for-mer is known from the cutting of the furrows, and has given a very simple method for determin-ing the latter. It is as To find Xexperimentally; Explanation ofapparatus; § 95. Let A and B be twocandles, or still better, two nar-row openings in a plate of metalheld before a window, the one, B,a little more elevated than theother; Pp, a perpendicular toA B at its middle point i3, andRR\ the furrowed glass placedsomewhere upon Pj>, and held sothat the furrows shall be per-pendicular to A B. On placingthe eye at E, and looking throughthe glass, we shall see the twocandles or openings by directview, and each of them flanked on either side by a series of fringes, those about B be-ing higher than those about A. By moving the glassIi Rf, to or from the candles, the red, or any other co-lor of the fringes on the left of B, may be broughtaccurately over the same color of the fringes to theright of A. These coincidences, however numerous, may coincidences ofbe established because of the law of the angular and samf colr © ^ produced; true distances of the fringes from
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