£0 MECHANIC TOWERS. 



the arms D E and E C may also represent these 

 velocities. 



It is evident then, that an equilibrium will take 

 place, when the length of the arm A E multi- 

 plied into the power A, shall equal E B multiplied 

 into the weight B ; and consequently, that the 

 shorter E B is, the greater must be the weight B; 

 that is, the power and the weight must be to each 

 other inversely as their distances from the fulcrum. 

 Thus, suppose A E, the distance of the power from 

 the prop, to be twenty inches; and E B, the distance 

 of the weight from the prop, to be eight inches ; 

 also the weight to be raised at B to be five pounds; 

 then the power to be applied at A must be two 

 pounds ; because the distance of the weight from 

 the fulcrum eight, multiplied into the weight rive, 

 makes forty; therefore twenty, the distance of the 

 power from the prop, must be multiplied by two, to 

 get an equal product ; which will produce an equili- 

 brium. 



It is obvious, that while the distance of the power 

 from the fulcrum exceeds that of the weight from 

 the fulcrum, a power less than the weight will raise 

 it, so that then the lever affords a mechanical ad- 

 vantage: when the distance of the power is less 

 than that of the weight from the prop, the power 

 must be greater than the weight to raise it; when 

 both the arms are equal, the power and the weight 

 must be equal, to be in equilibrio. 



The second kind of lever, when the weight is be- 

 tween the fulcrum and the power, is represented by 

 Plate 1. fig 8. in which A is the fulcrum, B the 

 weight, and C the power. The advantage gained 

 by this lever, as in the first, is as great as the dis- 

 tance of the power from the prop exceeds the dis- 

 tance of the weight from it. Thus, if the point c, 



