VOL. XLIV.] PHILOSOPHICAL TRANSACTIONS. 331 



quick-set hedges in England, he sent some plants of the white thorn over to his 

 own country for the same purposes ; before which time he assured me there were 

 none of them in Sweden, which he mentions in support of what was said above. 



The coming of these birds to us may then pretty well be accounted for from 

 the reasons aforesaid; but the cause of their departure from hence at the time 

 they leave us, is one of those secrets in nature which are not yet discovered; 

 for, should it be suggested that they do not leave us till the haws and berries are 

 all gone, and they are under a necessity to seek for food elsewhere, this would 

 amount to little, unless it could be shown that the northern regions, to which 

 they journey, can afford them a fresh supply; which it is almost certain they 

 cannot. And therefore, when first they go from us, they must either alter 

 their diet, or be in much distress; but as it is evident that their food in the 

 summer time must be of a different kind ,from what they eat in winter, it is 

 most likely they change their diet; and then one would imagine they should find 

 subsistence here in greater plenty, and much sooner, than in the colder countries 

 to which they fly. 



In short, all that can be said to be known of the matter, ends in this obser- 

 vation, that Providence has created a great variety of birds, ando ther animals, 

 with constitutions and inclinations adapted to their difTerent degrees of heat and 

 cold in the several climates of the world, by which no country is without inha- 

 bitants, and has given them appetites for the productions of such countries, whose 

 temperature is suited to their nature, as well as knowledge and abilities to seek 

 and find them out. From which we may infer, that the birds we have been 

 mentioning could no more subsist in the sultry climes of the Molucca isles, than 

 birds of paradise could in the frigid regions of Sweden or Lapland. 



Besides the migratory birds already mentioned, which breed and remain the 

 whole summer, there are other birds that arrive periodically at certain places for 

 the sake of some sort of grain, or other food, which may be supposed their own 

 country is destitute of; these birds, after no long continuance, depart, and are 

 no more seen till that time 12 months after; at which time they return, and so 

 continue repeating these annual visits, as has been already observed of the rice- 

 bird, and blue-wing of Carolina. Though the secret ways by which instinct 

 guides birds, and other irrational creatures, are little known to us, yet the causes 

 of some of their actions are apparent. 



Analogous to the lucrative searches of man through distant regions, birds take 

 distant flights in quest of food, or what else is agreeable to their nature; and 

 when they discover some new grain, or pleasing food, they return and acquaint 

 their community, and joining in numerous flights, make annual excursions to 

 solace on this their exotic food. 



Since the discovery of America there have been introduced from Europe several 



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