This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 Excerpt: ...is the most bent of all, and therefore has its position farthest off from the straight line. The remaining colours, such as orange, yellow, green, blue, have each one a particular position between, dictated by the degree in which it is bent out of the direct line. So we say that violet is 'the most refrangible, ' and ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 Excerpt: ...is the most bent of all, and therefore has its position farthest off from the straight line. The remaining colours, such as orange, yellow, green, blue, have each one a particular position between, dictated by the degree in which it is bent out of the direct line. So we say that violet is 'the most refrangible, ' and that red is ' the least refrangible.' This breaking up of a ray of light may be done in another and somewhat different mode from that just described. Instead of using a prism, the ray of light may be allowed to fall, slanting, upon a number of very fine lines, drawn so close together that the distance between any two of the lines is small compared with a light-wave. A beam of light, allowed to pass through or reflected from the surface, will again be broken up and spread about, as after passing through a prism. Lines are ruled on glass or metal for this purpose, so fine and so close together as to be only the twentythousandeth part of an inch apart. Thus, 20,000 lines can be crowded upon a square inch, --no easy matter to accomplish, even with all modern appliances for delicate work. Months may be spent in the making of a screw for the ruling-engine; and a year may pass in fruitless searching for a diamond point which will exactly do for such a task. Then, at the best, when all is prepared, five days and nights are occupied in the actual ruling of a six-inch grating, with 20,000 lines to the inch. To rule only 14,000 lines to the inch is, by comparison, an easy matter. Moreover, a glass grating is much harder to rule than a metal one, for in that case the diamond point is given to perpetually breaking down. Verily, the pursuit of knowledge in Astronomy has to be made in the face of obstacles. A ruled glass or metal of this description is known as.
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Add this copy of Radiant Suns: a Sequel to Sun, Moon and Stars (1895 ) to cart. $47.11, new condition, Sold by Revaluation Books rated 4.0 out of 5 stars, ships from Exeter, DEVON, UNITED KINGDOM, published 2009 by Cornell University Library.
