276 THE SWALLOW. 
“But how now stands the wind ? 
Into what corner peers my halcyon’s bill ?” 
For brightness and beauty of plumage, the kingfisher 
has no equal amongst our British birds, and so straight 
and rapid withal is its line of flight, that when the sun- 
light falls upon its bright blue back, it seems as if an 
azure bolt from a crossbow had been suddenly shot across 
our path. 
It is difficult to calculate or limit the speed which can 
be produced by the effort of a wing’s vibration. We may, 
nevertheless, ascertain with tolerable accuracy the rate of 
a bird’s flight, as follows:—If we note the number of 
seconds which are occupied by a bird in passing between 
two fixed points in its line of flight, and measure the 
distance between these points, we resolve the question to 
a simple “rule-of-three” sum; inasmuch as, knowing the 
number of yards flown in a certain number of seconds, we 
can ascertain the distance traversed in 3,600 seconds, or an 
hour, and thus obtain the rate of speed per hour; sup- 
posing, of course, the speed to be uniform. In this way 
the flight of the common Swallow (Hirundo rustica) has 
been computed at ninety miles,— 
“As swift as swallow flies.” 
Titus Andronicus, Act iv. Sc. 2; 
while that of the swift has been conjectured to be nearly 
one hundred and eighty miles per hour. 
