554 



WING. 



for migration. That a few instances occur of their having" been found in 

 old shafts of mines, and in similar situations, we will not dispute ; though 

 it is somew T hat extraordinary that those who have stated such as facts, 

 do not mention which species of swallow was so found ; nor have we 

 been able to find a single person of good authority who ever saw the 

 fact. Why these birds should ever have been denied their migrative 

 powers, we cannot conceive, when others, much less qualified for long 

 flights, have not been doubted. That this bird, as well as the chimney 

 swallow, is now and then seen flying- about long after the general dis- 

 appearance of these birds, we have more than once had ocular proof. 

 But these instances must be attributed to some accident or individual 

 defect, which prevented them from performing- their usual autumnal 

 flig-ht. It is well known that in some animals, whose radical heat is sen- 

 sibly affected by cold, the power of action is lost when the fluids become 

 languid, and animal life is as it were suspended. The bat, the dor- 

 mouse, and hedge-hog, become torpid in winter, when the mean state 

 of the air is below 45 ° ; and their heat sems to keep pace nearly with 

 the state of the atmosphere. But even at this season, the general 

 warmth of the sun regenerates their benumbed limbs, and the bat is 

 sometimes seen flying about at mid-day, but returns again to its former 

 state for weeks, and perhaps months, if the air proves colder. 



Thus it is with the martin and swallow who have been accidentally 

 detained in this northern climate ; they are roused by a certain degree 

 of heat, and the calls of hunger induce them to fly abroad for food ; and 

 it is much to be doubted, whether this sudden return of all the animal 

 functions does not prove fatal, from not being able to find sufficient 

 food to supply the natural excretions, which in a torpid state have been 

 observed to be little or none. It cannot be supposed it was intended by 

 nature, that birds, who have the power of shifting their quarters in so 

 expeditious a manner, and with such ease, should ever repose during 

 the colder season. It is therefore most reasonable to suppose such acci- 

 dental migrative birds, who are detained in a climate unsuitable to their 

 nature, perish before the return of the warmer months. We have 

 known several instances of a single bird of this species, flying about in 

 search of food after the middle of November, but never for two days 

 together, nor after the latter end of that month. It is found in most parts 

 of Europe, and in Asia. 



WING. — * The wing of a bird consists of five principal joints, with 

 small auxiliary ones as represented in the annexed figure, and by a com- 

 parison with the human arm, or the fore leg of a quadruped, we shall 

 find there is considerable similarity. The joints a b and c answer to 



