decade later, when news of its invention crossed the 

 Channel to England, this linkage excited a flurry of 

 interest, and variations of it occupied mathematical 

 minds for several years. For at least 10 years before 

 and 20 years after the final solution of the problem, 

 Professor Chebyshev,'^ a noted mathematician of the 

 University of St. Petersburg, was interested in the 

 matter. Judging by his published works and his 



' This is tile Library of Congress spelling 



Figure 17. — Straight-line linkage (be- 

 fore 1 841) attributed to Richard 

 Roberts by Robert Willis. From 

 A. B. Kempe, How to Draw a Straight 

 Line (London, 1877, p. 10). 



,/.■ /., ./■//,■/,/,,, 



/,„„/ ./,■ /'/.u 



Figure 18. — Machine for sawing off pilings under water, about 1760, designed 

 by De Voglie. The Roberts linkage operates the bar {Q_ in detailed sketch) at 

 the rear of the machine below the operators. The significance of the linkage 

 apparently was not generally recognized. A similar machine depicted in 

 Diderot's Encyclopedic, published several years later, did not employ the straight- 

 line linkage. From Pierre Patte, Memoirs sur les objets plus importants de f architec- 

 ture (Paris, 1769, pi. 11). 



202 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



