_Swimming_.—Notwithstanding his enormous size, we find that the sperm whale has the power of moving through the water with the greatest ease, and with considerable velocity. When undisturbed, he passes tranquilly along, just below the surface of the water, at the rate of about two to four miles per hour, which progress he effects by a gentle oblique motion from side to side of the “flukes.” When proceeding at his common rate, his body lies horizontally, his “hump” projecting above the surface, with the water a little disturbed around it, and more or less according to his velocity. This disturbed water is called by whalemen “white water,” and from the greater or less quantity of it an experienced whaleman can judge very accurately of the rate at which the whale is going from the distance of three or four miles. In this mode of swimming the whale is able to attain a velocity of about eight or nine miles per hour; but when desirous of proceeding at a more rapid rate, the action of the tail is materially altered. Instead of being moved laterally and obliquely, it strikes the water with the broad flat surface of the flukes in a direct manner, upward and downward, and each time the blow is made with the inferior surface the head of the whale sinks down to the depth of eight or ten feet, but when the blow is reversed it rises out of the water, presenting then to it only the sharp, cutwater-like inferior portion. The blow with the upper surface of the flukes appears to be by far the most powerful, and as, at the same time, the resistance of the broad anterior surface of the head is removed, it is the principal means of progression. This mode of swimming with the head alternately in and out of the water is called by whalemen “going head out;” and in this way the whale can attain a speed of ten or fifteen miles an hour, and this latter is believed to be his greatest velocity. The tail is thus seen to be the great means of progression, and the fins are not much used for that purpose; but occasionally, when suddenly disturbed, the whale has the power of sinking suddenly and directly downward in the horizontal position, which he effects by striking upward with the fins and tail.