ON THE DIVING OF AQUATIC BIRDS. 169 
of gravity for a purpose which shall be noticed here- 
after; the thighs quite at the podex, in order to 
facilitate diving ; and the legs are flat, and as sharp 
backwards almost as the edge of a knife, that in 
striking they may easily cut the water; while the 
feet are palmated and broad for swimming, yet so 
folded up when advanced forward to take a fresh 
stroke, as to be full as narrow as the shank. The 
two exterior toes of the feet are longest; the nails 
flat and broad, resembling the human, which give 
strength and increase the power of swimming. The 
foot, when expanded, is not at right angles to the 
leg or body of the bird; but the exterior part in- 
clining towards the head forms an acute angle with 
the body, the intention being not to give motion in 
the line of the legs themselves, but, by the combined 
impulse of both, in an intermediate line, the line of 
the body. 
“Most people know, that have observed at all, 
that the swimming of birds is nothing more than 
a walking in the water, where one foot succeeds the 
other as on the land; yet no one, as far as I am 
aware, has remarked that Diving Fowls, while under 
water, impel and row themselves forward by a motion 
of their wings as well as by the impulse of their 
feet; but such is really the case, as any person 
may easily be convinced who will observe Ducks 
when hunted by dogs in a clear pond. Nor do I 
know that any one has given a reason why the 
