202 Natural and Artificial Flight. (April, 
folding of one or both wings,—nay more, the slight tremor 
or quiver of the individual feathers of part of the wings so 
rapid that only an experienced eye can detect it,—all confirm 
the belief that the living wing has not only the power 
of directing, controlling, and utilising natural currents, but 
of creating and utilising artificial ones, which is not less 
important. But for this power, what would enable the bat 
and bird to rise and fly in a calm or steer their course in a 
gale? It is erroneous to suppose that anything is left to 
chance where living organisms are concerned, or that 
animals endowed with volition and travelling surfaces 
should be denied the privilege of controlling the movements 
of those surfaces quite independently of the medium on or 
in which they are destined to operate. What would we say 
of that quadruped or that fish which depended for the major 
portion of its movements on the ground it trod, or the water 
it navigated? I will never forget the gratification afforded 
me on one occasion at Carlow (Ireland) by the flight of a 
pair of magnificent swans. The birds flew towards and 
past me, and I had my attention directed to their presence 
by a peculiarly loud whistling noise 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 never seen anything before, and certainly have seen 
nothing since, that could in any way convey a more adequate 
idea of the prowess and guiding power which a bird may 
exert. What particularly struck me was the perfect mastery 
which they seemed to possess over everything. They had 
their wings and bodies visibly under control, and the air 
*T have frequently timed the beats of the wings of the common heron 
(Ardea cinerea) at Warren Point (Ireland). In March, 1869, I was placed 
under unusually favourable circumstances for obtaining reliable results. I 
timed one bird high up over a lake for fifty seconds, and found that in that period 
it made fifty down and fifty up strokes; z.e., one down and one up stroke per 
second. I timed another one in a heronry belonging to Major Hall. It was 
snowing at the time (March, 1869), but the birds, notwithstanding the inclemency 
of the weather and the early time of the year, were actively engaged in hatching, 
and required to be driven from theirnests 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 ten up strokes; i.¢., 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 exa¢tly 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 its beats. 
