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The Rain Cloud
or, An Account of the Nature, Properties, Dangers and Uses of Rain in Various Parts of the World

written by "Tomlinson, Charles, 1808-1897"
...st; and will fall upon the back of the drop in such a manner as to be reflected to the under part of the drop; on quitting which they will be again refracted, so as to be seen at E, where there will appear to the observer a prismatic spectrum with the red uppermost, and the violet undermost.  These remarks apply to those drops only which form the upper part of the bow, but it is obvious that a similar reasoning applied to the drops to the right and left of the observer, will complete the p. 143bow.  The inclination of the red ray and the violet ray to the sun’s rays, is 42° 2′ for the red, and 40° 17′ for the violet, so that the breadth of the primary bow is 1° 45′. Thus it will be seen, that the primary bow is produced by two refractions, and one intermediate reflection of the rays that fall on the upper sides of the drops of rain.  It is different with the rays which enter the drops below.  The red and violet rays will be bent or refracted in different directions; and, after being twice reflected, will be again bent towards the eye of the observer at E; but in this case the violet forms the upper part, and the red the under part of the spectrum.  The inclination of these rays to the sun’s rays at S, is 50° 58′ for the red ray, and 54° 10′ for the violet ray; so that the breadth of the bow is 3° 10′, and the distance between the primary and secondary bows is p. 1448° 15′.  Hence the secondary is formed in the outside of the primary bow, with its colours reversed, in consequence of their being produced by two reflexions and two refractions.  The colours of the secondary bow are much fainter than those of the primary, because they undergo two reflexions instead of one. There is something very wonderful in the rapidity and perfection with which these natural prisms, the falling drops of rain, produce these effects.  In the inconceivably short space...

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