164 SALMONIA. [SIXTH DAY. 



HAL. I have often observed, that the old proverb 

 is correct 



A rainbow in the morning is the shepherd's warning : 

 A rainbow at night is the shepherd's delight. 



Can you explain this omen ? 



PHYS. A rainbow can only occur when the clouds 

 containing, or depositing, the rain are opposite to the 

 sun, and in the evening the rainbow is in the east, 

 and in the morning in the west ; and as our heavy 

 rains, in this climate, are usually brought by the 

 westerly wind, a rainbow in the west indicates, that 

 the bad weather is on the road, by the wind, to us ; 

 whereas the rainbow in the east proves, that the rain 

 in these clouds is passing from us. 



POIET. I have often observed, that when the 

 swallows fly high, fine weather is to be expected or 

 continued ; but when they fly low, and close to the 

 ground, rain is almost surely approaching. Can you 

 account for this ? 



HAL. Swallows follow the flies and gnats, and 

 flies and gnats usually delight in warm strata of air -, 

 and as warm air is lighter, and usually moister, than 

 cold air, when the warm strata of air are high, there 

 is less chance of moisture being thrown down from 

 them by the mixture with cold air ; but when the 

 warm and moist air is close to the surface, it is 



