54 THE FLIGHT OF BIRDS 
evidently doing, the fggt of an almost vertical 
ascent. 
The big and bulky birds then, such as the Gannet 
and the Condor, having a much slower wing-stroke 
than the light-weights, must make it their first 
object to attain momentum, otherwise they will 
lose altitude between the strokes. When they 
have got way on, they can rise, but the line of their 
ascent is a gentle slope. For a steeper ascent the 
set of their wings unfits them. But there are birds 
of medium size, such as the Duck and the Pheasant, 
which, striking with very great rapidity and rotating 
their wings as freely as any small bird, are capable 
of raising themselves almost vertically through 
the air. 
Aeroplanes. 
In a country like England, with trees and hedges 
almost everywhere, an aeroplane capable of a 
steep ascent is a great desideratum. Captain 
Brooke-Popham, writing on military aviation, says 
that “‘ with no wind a fully-loaded machine, with 
observer, could get off a hard level field in a length 
of 120 yards and clear a fair hunting hedge at the 
end. Our Air Battalion “Farman” can do this 
in 90 to 100 yards without any difficulty.”* Thus 
even the ‘‘ Farman” requires a great deal more 
space than a Condor or a Comorant, birds noted 
as slow, lumbering starters, and though aeroplanes 
are constantly being improved it may well be 
doubted whether a steep ascent will ever be 
achieved. 
* The Army Review, January, 1912, p. 89. 
