208 CLASS AVF.S. 



supposed indispensable The first-mentioned writer has, more- 

 over, added to the characters of the rowing birds a dentelated 

 beak and a black eye, while the beak of the sailers is without 

 indention, and the eye is clear. Among the rowers he classes 

 the gerfalcon, the common falcon, the hobby, the merlin, but 

 not the kestrel ; and among the sailers, the gosshawk and the 

 hawk. 



The birds which are not rapacious may be considered, accord- 

 ing to the nature of their flight, either as rowers or sailers. 

 But it would be impossible to establish a marked division in 

 this Avay. The birds of prey, however, whether from instinct 

 or experience, are at no loss to distinguish these characters 

 •where they exist, and to direct their plan of attack and pursuit 

 accordingly. The raptorial sailer will suffer a bird eminently 

 endowed with the rowing capacity to pass without attempting 

 to put himself in motion, well knowing that he would be unable 

 to overtake him. Not so the raptorial rower, Avho shoots upon 

 his victim without such discrimination, equally capable of 

 assailing him on high, or pouncing upon him below\ 



If we united the considerations of anatomical structure to 

 the inductions of M. Huber from external characters, we might 

 institute a comparison between the motive forces of these two 

 different raptorial groups, to which, in imitation of him, we have 

 given the denominations of rowers and sailers : those, for in- 

 stance, which actuate their talons ; the texture and insertion 

 of the muscles which put the levers in action ; the disposition 

 of the tendons, and the augmentation of force, produced by the 

 re-acting pullies round which they circle. This comparison 

 might be even extended to the organs of respiration, to the 

 degrees of natural heat in those beings, some of which sustain 

 the rigorous cold of the more elevated atm.ospheric air without 

 detriment to health or respiration, while the others, though to 

 all appearance similarly constituted, rise but seldom, and for a 

 short period, above the lower regions. 



