"The upper part of the mortice in the shank, which receives the hinge of the wither, is here removed to show the lockings from which the joint derives its strength. Thus in figure 4, the wither A when expanded, locks against the fore part of the mortice, and at b against the septum in the back of the mortice, and at c against the other wither B; while in addition to these lockings, the withers are kept in their place by a strong screw pin d: the upper surface of the wither B, and the lower surface of A are filed down at the joint part, to exactly one half of their original thickness, so as together to coincide to the thickness of the withers externally, and to form a single equal plane when closed. In figure 5 are two springs by which the withers are forced asunder; in striking this harpoon the withers collapse, and only make an opening three inches wide, but the moment a strain is applied to withdraw it, the points become inserted in the blubber of the whale, and by means of the inclined planes at A and B, (Fig. 4) together with the efforts of the springs, they are separated, as the instrument withdraws, to the width of 7 inches. In this harpoon, I conceive, that the joint, which in all other harpoons of the kind has been the failing part, is as perfect, and as strong as could be wished. Comprising less breadth than the common harpoon, it must be more easily thrust into the fish; and making an opening only one half the size of the expanded withers, it will have less chance of retracting. The
upon the pins; for were the pins to be displaced, the harpoon, once fixed in the fish, would retain its hold by the withers being morticed.