ORDER PASSERES. 84f 



pie, that a bird to whose being, air in abundance is so essen- 

 tial, could exist even by suspended animation, in the medium 

 of water which would prevent the access of all air to the lungs- 



Another hypothesis to account for the disappearance of 

 swallows has been invented, which is, that they retire to 

 caverns and holes in the ground, and there remain torpid, 

 like some of the mammalia, during the winter. This has 

 been insisted on principally from the story published by 

 Achard, who states, that while travelling down the Rhine about 

 the end of March, in the year 1791, he saw children pulling 

 birds out of holes on the banks, and having purchased some of 

 them, which he found to be dormant, and, as it were, inani- 

 mate, he put one in his bosom, which, in about half an hour, 

 awaked and flew away. 



Montbeillard, and especially Spallanzani, who was never 

 stayed in the pursuit of natural knowledge by any feeling for 

 the victims of his experiments, have examined the probability, 

 or rather possibility, of these birds falling into a torpid state. 

 The latter has ascertained, by the use of artificial cold, that 

 swallows do not appear to suffer by cold at thp freezing point ; 

 that at 8° or 9° below it, they are sensibly affected but not 

 killed, and that at 13° or 14° they speedily die. 



To ascertain the effect of a continuance of low tempera- 

 ture, Spallanzani enclosed some swallows in wicker baskets, 

 covered with waxed silk to preserve them from humidity, and 

 buried them in snow, through which he made a hole for the 

 admission of fresh air. At the end of thirty-five hours some 

 of them were dead, and others were greatly debilitated, but 

 shewed no signs of lethargy ; ten hours after they had all 

 died : and this experiment, first practised in the month of 

 May, was repeated in the following July with the same 

 effect. To assure himself that the death of these birds was 

 not caused by want of food, the experimentalist placed other 

 swallows in his own room, and without food ; some of them 

 resisted death till the fifth day, and none died till after three 



