Birds inhabiting the Southern Ocean. 297 



" wind's eye/' If he wishes to ascend he inclines his body more 

 to the horizon by means of his head and tail. If he wishes to 

 turn to the right he bends his head and tail slightly upwards, at 

 the same time raising his left side and wing, and lowering the 

 right in proportion to the sharpness of the curve he wishes to 

 make, the wings being kept quite rigid the whole time. To 

 such an extent does he do this that, in sweeping round, his 

 wings are often pointed in a direction nearly perpendicular to 

 the sea ; and this position of the wings, more or less inclined to 

 the horizon, is seen always, and only when the bird is turning. 

 It will be observed that, on this principle, an Albatros sailing 

 down wind must necessarily be descending, unless his pace is 

 much greater than that of the air, and such I have found to be 

 invariably the case. 



It may be objected that the resistance of the air must soon 

 destroy his momentum ; but the fact is that it does not do so. 

 A good illustration of this is seen in an experiment, common in 

 lecture-rooms a few years ago, by which the rotation of the earth 

 was demonstrated by means of a pendulum, composed of a metal 

 ball suspended by a long string from the ceiling of the lecture- 

 hall. The impetus obtained by causing the metal ball to fall 

 through the space of a few feet only was sufficient to keep the 

 pendulum swinging, with a velocity but little diminished, for 

 the greater part of an hour, notwithstanding the resistance of 

 the sand, which the point of the pendulum had to cut through 

 twice during each vibration. The resistance of the air is well 

 known to depend on the shape and velocity of the moving body, 

 and to increase in proportion much more rapidly than the velo- 

 city increases. For this reason a properly shaped body and a 

 low velocity are required to reduce it to a minimum. A certain 

 amount of weight is also necessary to give a bird momentum 

 sufficient to overcome the resistance for a certain time, and 

 wings are required of sufficient expanse to support it as it sails 

 slowly through the air. These conditions are admirably carried 

 out in the Albatros; its expanse of wing is perhaps greater 

 than that of any other bird, and its weight, 15 lbs. and upwards, 

 is very large. Its shape, also, when the neck is stretched out, 

 as in flying, approaches very nearly to that of Newton's solid of 



