296 Capt. F. W. Button on some of the 



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 

 haviog 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 had 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 Albatros. 

 Moreover, the statement that he cannot sail against the wind is 

 incorrect, as Dr. Bennett himself said in his first book, ' Wander- 

 ings 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 for- 

 mer direction 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 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 de- 

 creased 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, Albatroses 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 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 Albatros 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 upward 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 



