io NATURE-STUDY REVIEW 



drops that are high- 

 er than those from which the 

 violet rays come, so the red 

 part of the bow appears on 

 the outside. 



Reverting now to those 

 spoke-like rays of the 

 sun previously mention- 

 ed, formed when the sun 

 is shining through broken 



Thus the red rays emerge from the drops cloud masses, Mr. Burroughs 

 lower than the violet rays, the eye wrote that he had never 



sees the red on top. i j ±.- r 1 



heard a satisfactory explana- 

 tion of their radiating character. When a sunbeam enters 

 a darkened room through an aperture its rays do not 

 diverge, i. e., according to Mr. Burroughs but are parallel, while 

 the rays passing through a cloud opening spread out like a fan. 

 The first of these statements is obviously incorrect, as can be 

 proven by anyone who will take the trouble to measure the 

 opening and then measure a cross-section of the beam a few feet 

 from the opening. Without going into any more difficult physical 

 explanation, the fact that the sun is not a point of light but a 

 disc of appreciable size, being roughly one one-hundredths in 

 diameter of its distance from us, is sufficient to account for the 

 spreading of the rays that are commonly spoken of as parallel. 

 Thus the rays from different parts of the sun's disc do not strike 

 the aperture at the same angle and the so-called beam diverges 

 slightly. But the light streamers seen in the cloudy sky do not 

 diverge only slightly but like spokes of a wheel with the sun at 

 the hub. Mr. Burrough's failure to explain this phenomenon is 

 evidently due to insufficient observation, for, writing elsewhere, 

 he made the statement that these rays are never seen except 

 between the observer and the sun. Now, one of our most striking 

 and beautiful sky displays is just the opposite of this. As the 

 sun is sinking low in the west, sometimes its rays will break through 

 clouds overhead and send long horizontal streamers across the 

 lake, making a huge fan-like illumination in the eastern sky, 

 and the rays converge not toward but away from the sun. The 

 explanation that this suggests is that the apparent direction of 



