LEVERS 



315 



it and the power, so that weight and power describe con- 

 centric arcs, the weiglit moving through the less space 

 when tlie lever moves, the lever is said to be of the 

 second order. (Fig. 96, IT.) 



And if, the fulcrum being still at one end, the power be 

 between the weight and it, so that, as in the former case, 

 the power and weight describe concentric arcs, but 



-tT 



4 



ill 



Fio. 96. 



The upper three figures represent the three kinds of levers ; the lower, 

 the foot, when it takes the character of each kind. — W, weight or resist- 

 ance ; F, fulcrum ; P, power. 



the power moves through the less space, the lever is of 

 the third order. (Fig. 96, III.) 



In the human body the following parts present ex- 

 amples of levers of the first order. 



(a) The skull in its movements upon the atlas, as 

 fidcnim. 



(6) The pelvis in its movements upon the heads of the 

 thigh-bones, as fulcrum. 



(c) The foot, when it is raised, and the toe tapped on 

 the ground, the ankle-joint heing fidcrum. (Fig. 96, I.) 



The positions of the weight and of power are not 

 given in either of these cases, because they are reversed 

 according to circumstances. Thus, when the face is being 



