388 Scientific Intelligenee. — Meteorology. 



weather is almost always approaching * ; the reason of which 

 might be thought to be that these animals, sensible of a current 

 of air approaching from the ocean, retire to the land to shelter 

 themselves from the storm. This is not the case however. The 

 storm is their element ; and the little petrel enjoys the heaviest 

 gale, because, living on the smaller sea-insects, he is sure to 

 find his food in the spray of a heavy wave, and she may be seen 

 flitting above the edge of the highest surge. The reason of 

 this migration of gulls, and other sea-birds, to the land, is their 

 security of finding food ; and they may be observed, at this 

 time, feeding greedily on the earth-worms and larvae driven out 

 of the ground by severe floods ; and the fish, on which they 

 prey in fine weather on the sea, leave the surface, and go deeper 

 in storms. The search after food is the principal cause why 

 animals change their places. The different tribes of the wading 

 birds always migrate when rain is about to take place. The 

 vulture, upon the same principle, follows armies ; and there is 

 no doubt that the augury of the ancients was a good deal found- 

 ed upon the observation of the instincts of birds. There are 

 many superstitions of the vulgar owing to the same source. For 

 anglers, in spring, it is always unlucky to see single mag- 

 pies, but two may be always regarded as a favourable omen ; 

 and the reason is, that, in cold and stormy weather, one magpie 

 alone leaves the nest in search of food, the other remaining sit- 

 ting upon the eggs or the young ones ; but if two go out toge- 

 ther, it is only when the weather is warm and mild, and favour- 

 able for fishing. — Sir H. Davy in Salmonia. 



3. Disturbance of the Magnetic Needle by Polar Lights. — 

 Various natural causes act upon the magnetic needle, so as to 

 occasion a sudden change in its position, or at least to disturb 

 the regularity of its diurnal variations. Of all these causes, the 

 aurora borealis appears to be the most energetic and infallible. 

 When this meteor rises in the northern regions, the sky is re- 

 splendent with light ; and during its whole continuance, which 

 sometimes lasts for ten or twelve hours, the magnetic needle ex- 

 periences a continued agitation^ and a considerable deviation. 

 The summit of the arch of the aurora is in general in the mag- 



• Gulls generally betake themselves to the land, not before, but after 

 storms. — M. 



