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FACULTIES OF THE MIND. 295 
wards. It would, however, be a hopeless task, to enume- 
rate the endless variety of gesture employed by other qua- 
drupeds and by birds, since each species uses gestures 
which are peculiar to itself, and suited to the organs with 
which it is furnished. The practical naturalist, indeed, 
studies these with care, as constituting one of the most de- 
lightful employments of his science. 
In using these gestures, animals, in general, employ 
sounds at the same time. If a crow is alarmed, and wishes 
to communicate its fears to the flock, it not only assumes 
a particular flight, but utters a cry which renders its feel- 
ings intelligible, not only to those of its own kind, but even 
to other birds and to quadrupeds. It may often be observ- 
ed that ducks in a pond, upon a particular motion of diving 
being performed as a signal, and a cry uttered by one, be- 
gin to dive and swim about in the water as if urged by one 
common impulse, and execute the most complicated and ra- 
pid evolutions in all the apparent giddiness of joy. But the 
motions of the flocks of Purrs (Tringa alpina), indicate a 
still more perfect system of signals. When flying, they keep 
their backs for a time ail in one direction ; and as suddenly, 
by achange of position, exhibit their bellies to the spectator. 
The change of position is very obvious, as their dusky 
backs, when directed to the observer, exhibit the flock as a 
dark cloud, which is changed to white, by the exhibition of 
the light-coloured feathers of the under side. Linnets, and 
several congregating birds, act in a similar manner. 
I have said, that. man comprehends the natural expres- 
sions of the lower animals, and even hinted that they in 
part. understand the gestures of one another. The dog 
and eat, however, are, perhaps, the only animals which can 
discern in the face of their master, the expressions of ap- 
probation or displeasure; and, by their behaviour, testify 
that they feel their influence. 
