SELF-MOVING MILL. 



being due to gravity, and therefore vertical, 

 is not applied at right angles to the arms except 

 when these are horizontal. Now the weights 

 are never at the full length of the arms until 

 after these have passed the horizontal position, 

 for it is not till then that the weights overbalance 

 and unbend the arms. But when the arms are 

 oblique, as at R G, the weights, whose force is 

 vertical, cannot devote it all to a tangential 

 turning effect. It can be shown by the parallelo- 

 gram of forces, as was done in the last section, 

 that the part of their force which is devoted 

 to tangential turning is to their whole weight in 

 the proportion of G C to G R ; in other words, 

 the leverage is not the full length of the arm, 

 or the distance of the weight from the centre of 

 turning, but its distance from the vertical line 

 through this centre. And though this turning 

 leverage G C, for weights at G, is still greater 

 than L O or M P, the turning leverage for weights 

 at L and M on the other side, it is not so much 

 so as appears to the eye when we look at the 

 full length of the arm G R. 



Secondly, it has been overlooked that the 

 bending of the arms keeps a greater number of 

 the weights on the ascending side, to com- 

 pensate for their less leverage for turning. 

 The weight S, for instance, though its arm O T 

 starts on the right-hand side, is itself to the 

 left of the vertical line through R, and so its 

 weight helps to prevent the left side rising. 



"5 



