HTTTT0N ON THE. BIKDS OF THE SOUTHERN OCEAN. 241 



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 doe3 not expressly say so, that he considers that the wind helps for- 

 ward the Albatross in the same way that 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. Advantage 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 has not been met by the resistance of the water, no resolution of 

 it into other directions 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 ; the truth being that he is more often seen sailing in this direc- 

 tion 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 direction than in the latter, in order to retain hia 

 position near the stern of the ship. However; when sailing against the 

 wind, the position of his wings, body, and tail, slanting a little down- 

 wards, is somewhat 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 able to move with 

 sufficient rapidity to prevent his falling, fresh impulses have to be 

 given. For this reason Albatrosses sail much longer in fine than in 

 stormy weather ; rain, especially, soon destroying their momentum, and 

 frequently obliging them to use their wings for propulsion. It is by com- 

 bining, 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 his momentum lasts. If, when 

 sailing against the wind, the inclination of his body is such that the up- 

 ward pressure of the wind against his wings 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 



" Wanderings in New South Wales." 



