SIXTH DAY.] INDICATIONS OF RAIN. 163 



flies, as soon as they come from the sea into rivers, 

 might depend upon a sort of imperfect memory of 

 their early food and habits ; for flies form a great 

 part of the food of the salmon fry, which, before 

 migrating to the sea, feed like young trouts ; flies are 

 their principal nourishment; and in going back to 

 fresh water, they may perhaps have their habits of 

 feeding recalled to them, and naturally search for 

 their food at the surface. 



P01ET. This appears to me very probable. But 

 it is late, and we must return and compare the crimped 

 trout and salmon ; and I hope we shall have another 

 good day to-morrow, for the clouds are red in the west. 



PHYS. I have no doubt of it, for the red has a 

 tint of purple. 



HAL. Do you know why this tint portends fine 

 weather ? 



PHYS. The air, when dry, I believe, refracts 

 more red, or heat-making, rays ; and as dry air is 

 not perfectly transparent, they are again reflected in 

 the horizon. I have generally observed a coppery or 

 yellow sunset to foretel rain ; but, as an indication of 

 wet weather approaching, nothing is more certain 

 than a halo round the moon, which is produced by 

 the precipitated water ; and the larger the circle, the 

 nearer the clouds, and consequently the more ready 

 to fall. M 2 



