evident, from the circumstance, that it is some- fins of a fish than the wings of a bird. In these, also, the feet are placed very far back, and their action must be most powerful; but in addition, the bird, in diving, uses its wings also, just as if it were flying in air; and you may readily conceive, that, by the impulse received from both wings and feet, the motion of the penguin through the water must be extremely rapid. Let me now bring to your recollection what, I suppose, you have witnessed more than oncethe cruel sport (as it is called) of duck-hunting. You will remember, that when the dog has got so near the duck the evident, from the circumstance, that it is sometimes so much surfeited as to let itself be taken by a noose cast round its neck: its gluttony, indeed, as every one knows, is proverbial. The following figure (fig. 17.) represents Fig. 17. the speckled diver; and you will remark how far backwards its legs are placed, and how well the whole conformation of the bird is fitted for diving. In the figure of the great crested grebe at the head of this letter, and in that of the puffin, or coulterneb, at the end, you will perceive a similar adaptation. But well fitted for an aquatic life as these are, there are some species still more so; as you will find in the history of the penguin tribe, in many of which the wings are so small, and covered with such scale-like feathers, that they more resemble the fins of a fish than the wings of a bird. In these, also, the feet are placed very far back, and their action must be most powerful; but in addition, the bird, in diving, uses its wings also, just as if it were flying in air; and you may readily conceive, that, by the impulse received from both wings and feet, the motion of the penguin through the water must be extremely rapid. I Let me now bring to your recollection what, suppose, you have witnessed more than oncethe cruel sport (as it is called) of duck-hunting. You will remember, that when the dog has got so near the duck that the latter is in danger of being seized, it plunges beneath the surface, and again appears, after several seconds, at a considerable distance from the place where it went down. The results of this manœuvre may be more than one: the dog may be bewildered, and consequently halt in the pursuit; or the duck may change the direction of its course, and on re-appearing may elude his eye, and thereby gain time. But I wish you to enquire whether a bird, in diving, will, by a similar impulse, move actually faster than it would in swimming. Does a cormorant, or a duck, or a grebe, move more rapidly under the surface of water than logical Dictionary, and the still more valuable Supplement to it, you will find illustrations on this point, showing that the same power will cause a much more rapid motion in diving than in swimming; and the cause is this: When a bird moves in water, or upon it, there is a movement upwards as well as forward; but in swimming, the momentum upwards is lost, and the bird derives benefit only from the forward impulse. But in diving, the pressure of the water above prevents the ascending movement, and consequently the impetus is not lost, as if the bird were on the surface, and therefore the propelling power is greater; and the bird moves faster, because, in diving, the whole moving power is effective; whereas, in swimming, a part of it is lost, and the progress is proportionally lessened. Notwithstanding the regularity of nature's works, there is at the same time scarcely any of the phenomena she presents to which there are not exceptions. Thus, although birds which swim have webbed feet, yet there are some which want that structure, and swim remarkably well; while there are others provided with web-feet, which do not swim at all. The common waterhen, which swims and dives remarkably well, is an example of the ormer (its toes, however, are |