RAINBOWS. 213 



which is produced by the precipitated water ; and the 

 larger the circles, the nearer the clouds, and, conse- 

 quently, the more ready to fall." 



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

 A rainbow at night is the shepherd's delight ; " 



why, of course, he cannot tell. The explanation of 

 Davy is this :- " A rainbow can only occur when the 

 clouds containing or depositing the rain are opposite 

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

 and in the morning in the west. As, therefore, 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." 



As to the old faith, that "the evening red is the sign 

 of a bright and cheery day," Dr Mitchell notes that the 

 red after sunset must have a crimson tinge, and must 

 last for some time. Davy, however, maintains that the 

 red must have a tint of purple, which tint portends fine 

 weather, for this reason : " The air, when dry, refracts 

 more red or heating rays ; and as dry air is not per- 

 fectly transparent, they are again reflected in the 

 horizon. I have generally observed a coppery or yel- 

 low sunset to foretell rain." Salmonia. 



In regard to underground prognostics such as the 

 increased flow of water in mines these are rendered 

 credible by what Arago relates in a singular chapter of 

 his l Meteorological Essays/ in which he shows that 

 where the atmosphere is tempestuous, there are simul- 

 taneously great perturbations in the interior of the 

 earth, and at or below the surface of waters. 



For instance, in the Yicentine Hills, when a thun- 

 derstorm is preparing, the fountain of Bifoccio, even 

 when it is apparently dried up, suddenly overflows its 

 basin, and fills a wide channel with muddy water. 

 Again, an Artesian well near Perpignan, which at first 



