29 



So far, also, as tlie end of the " cross-Hue " is- 

 drawn into rotation it Tvill produce concaves under 

 its course in the continuation of the mnding line. 



Were the diagonally opi^osite lower " point of 

 application" in active working, it would produce 

 another winding hne in the opposite direction, un- 

 der similar conditions, viz : from the right side of 

 the lower plane, by the front, to the lower end of 

 the cross-hne, and thence (this cross-line end being 

 moved) completing the circuit, by the rear, to the 

 right side of the upper plane section. 



§ 24. Two other such " winding hues " may be 

 developed fi-om the other two diagonal "points 

 of apphcation." At present we only consider the 

 diagonal points as acting by pairs, alternately. 

 The consideration of the two pairs, acting simul- 

 taneously, will be taken up further on. 



§ 25. It will be observed then, that each of these 

 winding Hues consists of two sections ; the pri- 

 mary one, which passes from the point of applica- 

 cation to its end of the " cross-line ;" and a sec- 

 ondary one, formed by the traction from the cross- 

 line end, which passes to a point situated in a 

 perpendicular line fi'om the originatiQg point of 

 application. 



The twisting of a cross-line is caused by the 



2- 



