156 



ANIMAL LOCOMOTION. 



made by their wings. They flew about fifteen yards from the 

 ground, and as their pinions were urged not much faster than 

 those of the heron,^ I had abundant leisure for studying their 

 movements. The sight was very imposing, and as novel as it 

 was grand. I had seen nothing before, and certainly have 

 seen nothing since that could convey a more elevated concep- 

 tion of the prowess and guiding power which birds may 

 exert. What particularly struck me was the perfect command 

 they seemed to have over themselves and the medium they 

 navigated. They had their wings and bodies visibly under 

 control, and the air was attacked in a manner and with an 

 energy which left little doubt in my mind that it played quite 

 a subordinate part in the great problem before me. The 

 necks of the birds were stretched out, and their bodies to a 

 great extent rigid. They advanced with a steady, stately 

 motion, and swept past with a vigour and force which greatly 

 impressed, and to a certain extent overawed, me. Their 

 flight was what one could imagine that of a flying machine 

 constructed in accordance with natural laws would be.^ 



The Natural Wing, when elevated and depxssed, must move 

 forwards. — It is a condition of natural wings, and of artificial 

 wings constructed on the principle of living wings, that when 



^ I have frequently timed the beats of the wings of the Common Heron 

 {Ardea cinerea) in a heronry at Warren Point. In March 1869 I was placed 

 under unusually favourable circumstances for obtaining trustworthy results. 

 I timed one bird high up over a lake in the vicinity of the heronry for fifty 

 seconds, and found that in that period it made fifty down and fifty up strokes ; 

 i.e. one down and one up stroke per second. I timed another one in the 

 heronry itself. It was snowing at the time (March 1869), but the birds, not- 

 withstanding the inclemency of the w^eather and the early time of the year, 

 were actively engaged in hatching, and required to be driven from their 

 nests on the top of the larch trees by knocking against the trunks thereof with 

 large sticks. One unusually anxious mother refused to leave the immediate 

 neighbourhood of the tree containing her tender charge, and circled round and 

 round it right overhead. I timed this bird for ten seconds, and found that 

 she made ten down and t.en up strokes ; i.e. one down and one up stroke 

 per second precisely as before. I have therefore no hesitation in affirming 

 that the heron, in ordinary flight, makes exactly sixty down and sixty up 

 strokes per minute. The heron, however, like all other birds when pursued 

 or agitated, has the power of greatly augmenting the number of beats made 

 by its wings. 



^ The above observation was made at Carlow on the Barrow in OcLobur 

 1867, and the account of it is taken from my note-book. 



