[guest] mechanism FOR DESCRIBING CONIC SECTIONS 27 



thut the joints are of the 8im))]ost type. The point P on the line ,S'.S' is 

 connected to the point on the Hart cell l)y a pin projecting from the link 

 of the cell and passing through the point P. The inverse point R then 

 descrihes the conic. 



If the same principles were used to describe the conic sections with- 

 out making use of the sliding pair, the following would be the mechanisms : 



Fig, 6 corresponding to Fig. 1. "^ 

 '•7 " ^ ■ ^ ^ 3. I 



a 8 u A 5 J 



In the figures the circles represent the turning pairs, and when they 

 are tilled up the element represented is fixed. When two lines are con- 

 nected by several arcs of circles where they meet, they represent one link 

 bent at that point. 



The mechanism-S in Figures 6, 7 and 8 are combinations of those of 

 Figures 1, 3 and 5 and of the straight line motions of Peaucellier and 

 Hart. 



