The heron, a specimen of which I dissected at the same time, gave a very different result, as the subjoined particulars will show. Weight of body, 3 lbs. 3 ounces; length of body from tip of bill to tip of tail, three feet four inches; head and neck, two feet; tail, seven inches; trunk, nine inches; girth of body, twelve inches; expanse of wing from tip to tip across the body, five feet nine inches; widest portion of wing across primary and tertiary feathers, eleven inches; across secondary feathers, twelve inches. Each wing, when carefully measured and squared, gave an area of twenty-six square inches. The wings of the heron, consequently, furnish a supporting area of four feet four inches square. As the bird only weighs 3 lbs. 3 ounces, this gives something like twenty-six square inches of wing for every 25-1/2 ounces of bird, or one foot 5-1/4 inches square for every 1 lb. 1 ounce of body. In the gannet there is only one foot one square inch of wing for every 2 lbs. 4-1/3 ounces of body. The gannet has, consequently, less than half of the wing area of the heron. The gannet’s wings are, however, long narrow wings (those of the heron are broad), which extend transversely across the body; and these are found to be the most powerful--the wings of the albatross--which measure fourteen feet from tip to tip (and only one foot across), elevating 18 lbs. without difficulty. If the wings of the gannet, which have a superficial area of three feet three inches square, are capable of elevating 7 lbs., while the wings of the heron, which have a superficial area of four feet four inches, can only elevate 3 lbs., it is evident (seeing the wings of both are twisted levers, and formed upon a common type) that the gannet’s wings must be vibrated with greater energy than the heron’s wings; and this is actually the case. The heron’s wings, as I have ascertained from observation, make 60 down and 60 up strokes every minute; whereas the wings of the gannet, when the bird is flying in a straight line to or from its fishing-ground, make close upon 150 up and 150 down strokes during the same period. The wings of the divers, and other short-winged, heavy-bodied birds, are urged at a much higher speed, so that comparatively small wings can be made to elevate a comparatively heavy body, if the speed only be increased sufficiently.[74] Flight, therefore, as already indicated, is a question of power, speed, and small surfaces _versus_ weight. Elaborate measurements of wing, area, and minute calculations of speed, can consequently only determine the minimum of wing for elevating the maximum of weight--flight being attainable within a comparatively wide range. [74] The grebes among birds, and the beetles among insects, furnish examples where small wings, made to vibrate at high speeds, are capable of elevating great weights.