75 



Afth April, 1882. 



The President, Robert Lloyd Patterson, Esq., in the Chair. 



Mr. Isaac J. Murphy^ read a Paper on 



LINKAGES : A RECENT MECHANICAL INVENTION, 

 BY MONSIEUR PEAUCELLIER. 



About fifteen years ago Mons. Peaucellier, a lieutenant in the 

 French army, living at Rennes, in Brittany, invented a simple 

 machine by the use of which the power is obtained of producing 

 perfectly straight lines, derived from acting on the motions of 

 radii of circles. It appears that he remained for a considerable 

 time, even some years, unaware of the magnitude of the im- 

 portance, as of the novelty, of his invention— it may be said, 

 of his discovery. About 1870, a student in the University of 

 St. Petersburgh, named Lipkine, without communication with 

 the prior inventor, made precisely the same discovery ; and 

 this at the very time when his preceptor, in all likelihood with 

 his knowledge, was engaged in trying to prove that it is not 

 possible to convert circular into correct lineal motion. 



The machine of Peaucellier (fig. I.) is very simple ; and the 

 mathematical proof of its correctness is easy to master. It has 

 since its first invention been subjected to various modifications, 

 and with these modifications it has been found capable of pro- 

 ducing circles of any radius, as well as many other curves, if 

 not of producing any and all curves in the region of plane 

 geometry. I wish to limit my present scope to the points I 

 have already examined into. I therefore quote only, without 

 following the unlimited road with all its branches which he 



