140 Analysis of Sciefitijic Books. 



countable, not only to the amiable author from whom the foregoing 

 passage is taken, but also to others who have written before on 

 the same subject." — Pp. 22, 23. 



These purposes, then, being accomplished, the migrators return 

 to their respective homes, and the mode of departure of the young 

 birds is one of the most singular occurrences in the history of mi- 

 gration. It may be imagined that a bird which has once crossed 

 the ocean might have something impressed upon it that should 

 prove an inducement to its return, but this cannot bean incitement 

 to the young one, and that the parent bird is not the guide is 

 proved by the cuckoo, whose offspring finds a distant shore in 

 safety, though it could never know its parent, for the old cuckoos 

 leave us in July, when many of their eggs are yet unhatched. 



The second part of Dr. Jenner's paper refers to winter birds of 

 passage, which take their leave of us about the same time that the 

 spring migrators are taking wing to pay us their annual visit. 

 That they are not, as is sometimes supposed, brought here through 

 hunger, rs quite obvious, for when the redwing and fieldfare quit 

 us, the country abounds with their favourite food, and they are 

 at this time in the finest condition. These birds never risk incu- 

 bation here, but some of the winter migrators, such as the snipe, 

 wild-duck, and woodpigeon, breed here in considerable numbers, 

 and among these the home-bred wild-ducks are easily distinguish- 

 ed by the meanness of their plumage, when compared to the bright- 

 ness of that of the foreigners ; they are also taken some weeks 

 earlier. 



Dr. Jenner remarks, that the food of redwings and fieldfares is 

 not, as is commonly supposed, the haw, which they take in scanty 

 quantities only, but that they feed on worms and insects, and that 

 when a very hard frost sets in they often leave us for a time, in 

 consequence of the scarcity of such food. Before a severe froit a 

 numerous tribe of water-birds generally make iheir appearance, 

 some of which seldom show themselves on any other occasion. 



We shall now conclude with a long quotation from Dr. Jenner's 

 paper, which is not witliout interest, and which is very creditable 

 to the moral feelings of the author ; it is certainly a digression 

 from the main subject of his communication, and yet not irrelevant 

 to it. 



" We must observe, that nature never gives one property only to 

 the same individual substance. Through every gradation, from 

 the clod we tread upon to the glorious sun which animates the 

 whole terrestrial system, we may find a vast variety of purposes 

 for which the same body was created. If we look on the simplest 

 vegetable, or the reptile it supports, how various yet how import- 

 ant in the economy of nature are the offices they are intended to 

 perform ! The bird, I have said, is directed to this island at a 



