APPLICATION OF GRAPHIC METHODS 



297 



them. They, in fact, with the links of the quadrilateral, con- 

 stitute a machine working a machine such as will be discussed 

 when treating of compound machines ; similarly, when we re- 



present the driving and resisting element by springs, as in the 

 foregoing cases, we might have observed that in an actual 

 spring the stress would not be strictly axial. In most practical 

 cases, however, the stress will be so nearly axial that for the 



