82 
BIRD-LIFE. 
wing, and thus lifts the bird; while, with a fair wind 
the wings are pressed down. This explains to ns how 
birds can continue to circle at a high level without 
moving the wings or even ascending higher. The act of 
starting to fly, which is mostly preceded by one or two 
springs, can only take place, by many birds, with the head 
to windward. The velocity of flight is a question which has 
as yet received hut little attention ; though we know that 
it is the fastest of all animal movements. It is estimated 
that a salmon will run 86,000 feet in the space of one 
hour: if it were to continue swimming at this rate 
it would circumnavigate the globe in a few weeks.* 
These suppositions are merely based on a calculation of 
probability, and not on actual observation; so it is pos¬ 
sible that this statement is somewhat exaggerated. Even 
were the sum thus given correct, this scale of rapidity is 
still far behind that of flight. An express train runs at 
the rate of seven f German miles pier hour; and a 
distance of ten has been attained in a like time: this, 
however, is only an average rate of flight for a bird. 
The pace of the Crow exceeds that of ordinary trains, 
although this bird does not belong to the class of rapid 
flyers; and with every effort the locomotive lags far 
behind the domestic Pigeon. Carrier Pigeons have 
been known to traverse a distance of fifty-six German 
miles in five hours and forty-four minutes; and 
flights of thirty-five German miles have been covered 
in less than three hours. This represents a rate 
of 280,000 feet per hour, which surpasses the speed 
of the salmon in the proportion of three and a half 
* From Hartwig’s ‘ Leben des Meeres,’ 4 Aufl. S. 174.— Dr. Brehm. 
t It may be well to observe that this moderate rate of travelling is confined to 
foreign lines.— W. J. 
