212 NATURAL HISTORY. 



The bird, therefore, could not raise the temperature of the air taken into these cells more than 60 Fahr. 

 This would increase its volume not quite one-eighth; and taking 100 cubic inches of air to weigh 31 

 grains, and the average weight of an Albatross to be 17 Ibs., as given by Gould, it would be necessary, 

 in order that the specific gravity of the bird might be brought to that of the atmosphere, that these 

 cells should contain 1,820 cubic feet of air; or, in other words, they must be more than 1,200 times 

 the size of the body itself of the bird, which, to say the least, would give it when flying an aldermanic 

 appearance which I have never observed. In fact, it would require a sphere of more than fifteen feet 

 in diameter to contain the necessaiy quantity of air. Even if it could thus buoy itself up, it would entirely 

 defeat its own object ; for it would at once destroy the whole of its momentum, and unless propelled 

 forward by its wings, would drift helplessly to leeward. However, I do not wish it to be inferred that 

 I consider the air-cells of no use. The gi*eater portion of them are situated round the neck, wings, 

 and fore part of the body of the bird, and I believe that by their means he is enabled to shift slightly 

 he position of his centre of gravity and thus, with very slight muscular exertion, to vary the inclina- 

 tion of his body to his horizon according to the rate at which he is moving through the air. 



" Dr. Bennett, in his ' Gatheiings of a Natm-alist ' (p. 78), gives a diagram explanatory of the 

 flight of the Albatross," continues Captain Hutton ; "and if I understand him rightly, says that 'it 

 cannot sail directly against the wind, but only in the way which sailors call 'close hauled.' This 

 diagram represents a square rigged ship sailing six points from the wind, a cutter sailing four and a 

 half points, and an Albatross flying two points from the wind, from which I infer, although he does not 

 expressly say so, that he considers that the wind helps forward the Albatross in the same way it does 

 the ships. But that this is erroneous is apparent at a glance. A ship can sail at an acute angle with 

 the wind because the pressure of the wind against its sails being met by the resistance of the water, is 

 resolved into pressures having other directions. A dvantage of this being taken by trimming the sails, it 

 ultimately results that the ship is moved in the direction of least resistance, viz., forwards. If, however, 

 the pressure of the wind had not been met by the resistance of the water, no resolution of it in other direc- 

 tions could have taken place. For this reason a balloon can only drift with the wind, and the same would 

 be the case with the Albatross. Moreover, the statement that he cannot sail against the wind is incorrect, 

 as Dr. Bennett himself said in his first book, ' Wanderings in New South Wales,' the truth being that 

 he is more often seen sailing in this direction than in any other, for the simple reason that as he moves 

 slower against the wind than with it, he is obliged to keep going for a longer time in the former direc- 

 tion than in the latter, in order to retain his position near the stern of the ship. However, when 

 sailing against the wind, the position of his wings, body, and tail, slanting a little downwards, is some- 

 what analogous to the sails of a ship close hauled, or, still better, to the position of a kite in the air, 

 the momentum of the bird taking the place of the resistance of the water, or the string of the kite. 

 This momentum is entirely owing to impulses previously given to the air by means of his wings, and 

 when, owing to the resistance of the air, it has decreased so much that he is no longer abJe to move 

 with sufficient rapidity to prevent his falling, fresh impulses have to be given. For this reason 

 Albatrosses sail much longer in fine weather, rain especially soon destroying their momentum, and fre- 

 quently obliging them to use their wings for propulsion. 



" It is by combining, according to the laws of mechanics, this pressure of the air against his 

 wings with the force of gravity, and by using his head and tail as bow and stern rudders, that the 

 Albatross is enabled to sail in any direction he pleases so long as the momentum lasts. If, when sailing 

 against the wind the inclination of his body is such that the upward pressure of the wind against his 

 dngs and body just balances the force of gravity, his momentum alone acts, and he sails straight in 

 the ' 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 Albatross 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. 



