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The Sciences (It by a different opening)

it by a different opening, after appropriating the air. The gills, too, have a moveable The air-bladders of fish enable them to rise or sink at pleasure; and this power, and that of the fins and tail, give the largest speed-a speed many times greater than any ship. The brain of fish is small, and does not fill the skull. They have no tympanum, and no external ear. They have neither windpipe nor larynx, but breathe by gills. Their nose is not connected with respiration, and they have no urinary bladder. Only a few fishes have ribs, there being no respiratory organs to protect in the chest. Their bones are radii. Fishes have a double circulation, but their respiratory organs (the gills) are only formed to respire by the intervention of water, and their blood only receives that portion of oxygen dissolved or mixed in the water. Fishes are believed to be of equal specific gravity with water, and occasional inequalities are corrected by their air-bladder. They move by the action of their tails, and not by their fins, which are mere regulators. Fishes are from 1½ to 2 degrees warmer than water. The birds' nests that are edible are built in sunless caves, and covered by the birds with a gelatinous substance that is much esteemed by the Chinese. There are 9,000,000 nests yearly imported into Canton, of which it takes 50 to weigh 1 lb., valued at $40. The annual consumption is therefore about $7,200,000 worth. The flight of birds is as follows:-Hawk, 150 miles an hour; crow, 100 miles; eider duck, 90 miles; rook, 60 miles; pigeon, 40 miles. In November 1882 some carrier pigeons made the distance from Canton Vaud to Paris, 160 miles, in 6½ hours in the face of a gale of wind, a rate of 25 miles an hour.