i 9 2 THE POPULAR SCIENCE MONTHLY. 



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. Con- 

 sequently, 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 re- 

 garding the left hand as the fulcrum of motion, he gives an impulse, 

 and this impelling force is continued until an involuntarily conscious- 

 ness 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. 



Fig. 6. 



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 en- 

 trance into the head it may be double what it is at the other extrem- 

 ity. 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, 





