vin SEASONS OF RAINBOW 33 



sun and the moon at times. Why should the circle 

 be complete in the halo, but never in the rainbow ? 

 And then again, why should the clouds that receive 

 the sunlight be always hollow ones, and not some- 

 times flat or bulging ? 



Aristotle says that rainbows are formed, after the 

 autumnal equinox, at any hour of the day, but in 

 summer only either in the early part of the day, or 

 when the sun has begun to sink. The cause of this 

 is obvious. In the first place, about midday the great 6 

 heat of the sun dispels the clouds : he cannot be 

 reflected in the clouds which he breaks up. But 

 in the early morning and as he sinks toward the west, 

 his rays have less power, and can thus be resisted 

 and reflected by the clouds. In the second place, 

 the sun is not wont to form a bow except when he 

 faces the clouds in which it is formed. When the ^ 

 days are shortening in autumn, his rays are always 

 slanting. Therefore, he has some clouds facing him 

 that he can strike, at any part of the day, even at 

 the hour at which he attains his meridian height. 

 But in the summer season he sails right overhead. 

 Therefore, in the great altitude of his midday 

 course, he looks down on the earth too directly to 

 encounter any clouds. He has them at that period 

 all beneath him. 



IX 



I MUST now go on to speak of Streaks (watergalls, i 

 sun-dogs), which are as bright and varied as the 

 rainbow, and commonly received by us as equally 

 indicative of rain. No great labour need be spent 

 in explaining them, for they are just incomplete 2 

 rainbows. They have the variegated appearance 



