24 



elements is more particularly drawn, and these are 

 the first ones to become stretched. It is along 

 these elongated lines that the convex aspects of 

 the turns occur, while the other parts are com,pressed 

 into concaves. 



§ 16. If for the wliip-lash there be substituted 

 a firm but elastic cylindrical rod, the two diagonal 

 forces of rotary counter-traction, supplied by the 

 thumbs and fingers, may be replaced by two forces 

 of diagonal GownteY-'pressiire, the points of applica- 

 tion of which will be situated at opposite edges of 

 terminal horizontal planes at the ends of the rod. 



Replacing then the piece of whip-lash by an 

 elastic cylindrical rod, terminated at each end by 

 plane surfaces cut perpendicularly to its length, the 

 rod being held perpendicularly before the face ; 

 replacing also the action of the fingers by two 

 compound forces, consisting each of a force of 

 pressure in the perpendicular plane and a force of 

 rotation, around the axis of the cylinder, in the 

 horizontal, the latter drawing the substance of the 

 cylinder with it ; let these forces be applied, one 

 on each terminal plane near the circumference, and 

 at diagonally opposite points, and while the forces 

 of pressure act in contrary directions, let the forces 

 of rotation act also in opposition to each other. 



