THE VICTORIAN NATURALIST. 13 



stiff breeze — indeed, the stronger the wind the more motionless 

 are the wings, and the less necessity for resorting to flapping. 

 Two theories based on the movements of the wind have been 

 propounded — the first that a soaring bird is supported by upward 

 currents, that is, that the wind is not horizontal ; the second that 

 the wind is not uniform in velocity, so that a bird can by 

 manoeuvring take advantage of this want of uniformity, and it 

 was to test which of these theories is supported by the actual 

 movements of soaring albatrosses that my observations were 

 made. The first is championed by no less an authority than Mr. 

 Hiram Maxim, and therefore deserves some notice. In an 

 article in the North American Review for October, 1895, he 

 states that Professor Froude, the mathematician, observed the 

 flight of that greatest of all flyers, the albatross, and admitted 

 that no existing mathematical formula could account for the 

 soaring of these birds, and proceeds as follows : — " Air near the 

 surface of the earth becomes heated and ascends in columns. 

 The velocity with which these vertical currents move is, say, from 

 1 to 6 miles an hour, and they are quite independent of any 

 other horizontal current that the air may have as relates to 

 the earth at the same time. Suppose the velocity of a bird 

 to be 30 miles per hour, this would account for the whole 

 phenomenon of soaring on an upward current of only 1^ 

 miles an hour." Now, do these vertical currents exist ? I 

 think not. The smoke of steamships exhibits practical uni- 

 formity in a vertical direction, while Mr. Maxim supposes the air 

 divided into alternatively ascending and descending columns ; 

 and to account for the birds not being caught in the latter 

 currents, he advances an ingenious but unproven theory that 

 birds have some very delicate sense of feeling and touch to 

 ascertain whether they are falling or rising in the air, just 

 as deep-sea fish can tell by the pressure on the bladder 

 whether they are approaching the surface. Mr. Maxim goes on 

 to say : — "Albatrosses and seagulls find a resting place, and follow 

 the ship for days at a time without any apparent exertion, but 

 whenever they find themselves in front of the ship or at one side 

 they have to work their passage very much as other birds do." 

 This statement is incorrect as far as albatrosses are concerned ; 

 they never move continually in a straight line, but are always 

 circling and sweeping up and down the wind, alternately rising 

 and falling. This fact is the strongest argument against the 

 theory, for these continual movements between the upper and 

 the lower strata of the air would have no object. I do not deny 

 that upward currents exist, but Mr. Maxim has undoubtedly 

 given the principle a too extended application. I have noticed 

 albatrosses keeping to the leeward of the crest of a large 

 wave, where the wind is undoubtedly deflected upwards. Herr 

 Lilianthal, who has used an aeroplane to soar several hundred 



