THE LEVER. 



SECTION II. 



THE LEVER 



The simplest of all machines is the lever. It con- 

 sists of a rod or bar, one end resting upon a prop ox ful- 

 crum, F {Fig. 41), near which is the weight, W, moved 



Fig. 41. 



Lever of the second kind. 



by the hand at P. The stone may weigh 1000 pounds ; 

 yet, if it is ten times as near the fulcrum as the man's 

 hand is, a force of 100 pounds will lift it ; but it will 

 be moved only a tenth part as high as the hand has 

 been moved, as shown by the dotted lines. By placing 

 the stone stiU nearer the fulcrum, still less will be the 

 power required to raise it, but then the distance ele- 

 vated would be also still less. By sufficiently increas- 

 ing the disproportion between the two parts of the le- 

 ver, the strength of a child merely might be made to 

 move more than many horses could draw. 



These performances of the lever often excite aston- 

 ishment at what appears to be out of the common 

 course of things ; yet, when examined by the princi- 

 ples of mechanics, instead of appearing matters of as- 

 tonishment, they are formd to be only the natm-al and 

 necessary results of the laws of force. In the case of 

 the lever just described, it is often incorrectly supposed 

 that the power itself sustains the weight. But this is 



