ON THE DIVING OF AQUATIC BIRDS. 171 
greater than that with which they move on its sur- 
face, where the legs are usually employed alternately, 
and the moving force cannot be so advantageously 
applied ; and that the velocity is frequently accelerated 
still further by the instrumentality of the wings, has 
been already noticed. 
Thus, in controverting the erroneous opinions of 
Montagu relative to the diving of Water-fowl, I have 
endeavoured to substitute for them an unobjection- 
able theory of this remarkable phenomenon. 
