458 Transactions. — Miscellaneous. 



For in all cases the appearance to the observer must be 

 that of a circle or an arc of a circle, whether the raindrops 

 emitting the rays which reach his eye be arranged on the 

 surface of the rain-sheet circularly or elliptically, because they 

 must, from the nature of the case, reach the eye from all 

 directions at the same invariable angles to the sun's rays, and 

 form their picture on the retina of the eye, which is practically 

 a plane to which the direction of the sun's rays is perpen- 

 dicular, and thus the ellipse is projected as a circle in the 

 eye. 



This invariableness of the direction of the rays explains 

 also why it is that we see, as an even arc of a circle, rays 

 coming from an uneven surface of rain-sheet, for doubtless the 

 rain-sheet producing the rainbow is almost always undulating 

 in broken curves corresponding with the irregular edge of the 

 rain-cloud from whence the rain is falling, and some of the 

 drops emitting their cones of brilliant light must be farther off 

 than others in an irregular manner. The eye is only capable 

 of giving information as to the direction and the brilliancy or 

 force of light, just like a theodolite or other optical instrument, 

 and we do observe variations in brilliancy in different parts of 

 a rainbow, which no doubt result from the greater or less 

 distance from us of the raindrops emitting the light. Such 

 variations in brightness are noted on figs. 9, 10, Plate LI. 



THE BIRTH OF A RAINBOW. 

 The sun-born waves of heat stirred with tumultuous force 

 The liquid water ; atom from atom moved apart 

 In active vaporous rhythmic clance, mingling with air 

 And gravitation's mighty balance bore them up. 

 Hither and thither, upwards, downwards they were swayed, 

 Until a colder and less active air was met, 



In warming which themselves lost heat and shrank to water back. 

 By gravitation urged the liquid drops were formed, 

 Each one a globe, and all to earth attracted fell. 

 Now light-waves struck the falling globes, and, ruled by law, 

 Were bent and sifted, and streamed back, cone within cone 

 Of brilliant-coloured light from all these tiny globes. 

 Perchance a human eye beheld the falling rain, 

 And from those countless cones of coloured rays some strike 

 His eye, from this side, and from that, and from above, 

 But all at the self-same angle of self-same hue ; 

 And thus was pictured in his eye the coloured arch 

 (It may be two), and he perceived the glorious thing. 

 A human mind,* a seeing eye, matter and light, 

 Heat, gravitation, all combined to bring it forth. 

 But trace it one step farther back. Whence came all these ? 

 Who formed and ordered them together so to work 

 In perfect harmony ? In the beginning God — 

 His mighty will, the energizing power still. 



* Has any one ever observed an animal (other than man) looking at, 

 or taking notice of, a rainbow ? 



