Page:Popular Science Monthly Volume 9.djvu/212

192 the power exerted to raise a body is in the inverse ratio of the spaces passed through by the body, and the point of application of the power, it may thus be obvious how great a strain will be on the muscles if the axe-head be raised by the hands at the opposite extremity of the handle. Reverse the problem. Take the axe-head as raised to such an elevation as to cause the handle to be vertical (we are dealing with ordinary axes, the handles being in the plane of the axe-blade). Now, the left hand is at the extremity of the handle, the right hand is very near to the axe-head the blow is about to be given. The requirement in this case is that there should be concentrated at the axe-head all the force or power possible; hence to ease the descent would be as injudicious as to intensify the weight of the lift. Consequently, while with the hand nearest to the head (as it is when the axe reaches its highest elevation) the workman momentarily forces forward the axe, availing himself of the leverage now formed by regarding the left hand as the fulcrum of motion, he gives an impulse, and this impelling force is continued until an involuntarily consciousness assures him that the descending speed of the axe is in excess of any velocity that muscular efforts can maintain. To permit gravity to have free play, the workman withdraws the hand nearest to the head, and, sliding it along the handle, brings it close to the left hand, which is at the extremity of the handle; thus the head comes down upon the work with all the energy which a combination of muscular action and gravity can effect. The process is repeated by the right hand sliding along the handle, and releasing as well as raising the head.



The form of the axe-handle deserves notice, differing: as it does from that of the sledge-hammer. In the latter it is round or nearly so, in the axe it is oval, the narrow end of the oval being on the side toward the edge of the axe, and, more than this, the longer axis of the oval increases as the handle approaches the head, till at its entrance into the head it may be double what it is at the other extremity. It often has also a projection at the extremity of the handle. The increasing thickness near the head not only gives strength where needed, as the axe is being driven in, but it also supplies that for which our ancestors employed the thongs as illustrated in Figs. 4 and 5. There is, too, this further difference—in a sledge-hammer more or less recoil has to be provided for, and the handle does this; in the axe no recoil ought to take place. The entrance of the axe-edge is,