66 Mr. A. Cayley on a BicycUc Chuck. 



Then, the chucks being connected and Q being attached to Y — 

 moving X^ this moves Y, which moves Q, which (through the 



pentagraph) moves P; that is, we have the chuck-table X and 

 the pencil P both of them in motion, and P traces out on X a 

 curve compounded of these two motions. 



In my own roughly constructed apparatus, X is a bicyclic (or 

 an oval) chuck, Y a mere circular chuck rotating through an 

 angle of about 40 °; and a point M of the chuck-table X can be so 

 connected as to be at a given distance from a point N of the chuck- 

 table Y ; the complete rotation of X thus gives to Y a recipro- 

 cating circular motion. The connexion is made by an excentric 

 working below the chuck-table X; viz. we have rigidly con- 

 nected with the chuck ^X a cylindrical axis of about 3 inches 

 radius and i inch high, carrying rigidly connected therewith 

 the chuck-table X ; and the excentric works round this axis (the 

 centre of the axis being thus the point M), and its other extre- 

 mity round an axis on the upper surface of chuck-table Y : the 

 pencil Q can be connected (within limits) with any point of the 

 chuck-table Y. 



The result is that, the chucks being disconnected, the fixed 

 pencil P traces out on chuck-table X the curves determined by 

 the construction of this (bicyclic or oval) chuck ; but when the 

 connexion is estabhshed, the complete rotation of X gives to Y 

 a reciprocating circular motion, which Y communicates to Q, and 

 Q to P; that is, the pencil P, instead of being fixed, has a reci- 

 procating circular motion. I obtain hereby, among other forms, 

 elegant three-looped curves. 



