86 GRAMME. 



little action as an organ of flight, would otherwise be much 

 more difficult. 



In alighting, these birds have some difficulties to overcome 

 which are not felt by those orders which are better furnished 

 with tails, or do not use their feet as a balance and a rudder 

 in their flight. When the legs are brought downwards, the 

 anterior part of the bird becomes heaviest, and there is, in so 

 far as gravitation is concerned, a tendency to come down 

 head foremost. But the wings are so formed as to counter- 

 act that tendency. They are hollow on their under sides, 

 especially towards the anterior parts, where all wings are 

 stifiest ; and thus they both take a much more buoyant hold 

 on the air as a resisting medium, and produce a reaction to 

 their stroke obliquely upwards and backwards, in consequence 

 of which the bird is enabled to alight with the axis of its 

 body in a more upright position than those birds which have 

 not their wings so formed. In that way the birds can let 

 themselves down veiy gradually, so as to feel no shock when 

 they alight upon hard surfaces, and not to sink when they 

 descend, even with their greatest rapidity, upon surfaces that 

 are moist and soft. 



In all cases, a concave wing takes a better hold of the 

 air than a flat one ; and some of the grallse can, by means 

 of their wings, work the body into a vertical position, in the 

 same way as some of the swimming birds can do when they 

 elevate themselves out of the water ; while others can convert 

 the partially expanded wings into very efficient auxiliaries 

 when they run rapidly. 



These habits vary much in different species, but they 

 belong in a greater or less degree to all the birds of the 

 order. 



HAUNTS OF THE ORALLY. 



Several foreign species of this order not only inhabit near 



