maneuvering to unload its charge of gentlemen and 

 their ladies at the door of the venerable hall of the 

 Royal Institution. Amidst a "mightly rustling of 

 silks," the elegant crowd made its way to the audi- 

 torium for one of the famous weekly lectures. The 

 speaker on this occasion was James Joseph Sylvester, 

 a small intense man with an enormous head, sometime 

 professor of mathematics at the University of Virginia, 

 in America, and more recently at the Royal Military 

 Academy in Woolwich. He spoke from the same 

 rostrum that had been occupied by Davy, Faraday, 

 Tyndall, Ma.xwell, and many other notable scientists. 

 Professor Sylvester's subject was "Recent Discoveries 

 in Mechanical Conversion of Motion. "''^ 



Remarking upon the popular appeal of most of the 

 lectures, a contemporary observer noted that while 

 many listeners might prefer to hear Professor Tyndall 

 expound on the acoustic opacity of the atmosphere, 

 "those of a higher and drier turn of mind experience 

 ineffable delight when Professor Sylvester holds forth 

 on the conversion of circular into parallel motion."** 



Sylvester's aim was to bring the Peaucellier linkage 

 to the notice of the English-speaking world, as it had 

 been brought to his attention by Chebyshev — during 

 a recent visit of the Russian to England — and to give 

 his listeners some insight into the vastness of the field 

 that he saw opened by the discovery of the French 

 soldier.*^ 



"The perfect parallel motion of Peaucellier looks 

 so simple," he observed, "and moves so easily that 

 people who see it at work almost universally express 

 astonishment that it waited so long to be discovered." 

 But that was not his reaction at all. The more one 

 reflects upon the problem, Sylvester continued, he 

 "wonders the more that it was ever found out, and 



" Sylvester, op. cit. (footnote 41), pp. 179-198. It appears 

 from a comment in this lecture that Sylvester was responsible 

 for the word "linkage." According to Sylvester, a linkage 

 consists of an even number of links, a "link-work" of an odd 

 number. Since the fixed member was not considered as a link 

 by .Sylvester, this distinction became utterly confusing when 

 Reuleaux's work was published in 1876. Although "link" 

 was used by Watt in a patent specification, it is not probable 

 that he ever used the term "link-work" — at any rate, my search 

 for his use of it has been fruitless. "Link work" is used by 

 Willis {op. cit. footnote 21), but the term most likely did not 

 originate with him. I have not found the word "linkage" used 

 earlier than Sylvester. 



^* Bernard H. Becker, Scietilific Londor,, London, 1874, pp. 45, 

 50, 51. 



*' Sylvester, op. cil. (footnote 41), p. 183; Nature, November 1 3, 

 1873, vol. 9, p. 33. 



can see no reason why it should have been discovered 

 for a hundred years to come. Viewed a priori there 

 was nothing to lead up to it. It bears not the remotest 

 analogy (except in the fact of a double centring) to 

 Watt's parallel motion or any of its progeny.'"" 



It must be pointed out, parenthetically at least, 

 that James Watt had not only had to solve the prob- 

 lem as best he could, but that he had no inkling, so 

 far as experience was concerned, that a solvable 

 problem existed. 



Sylvester interrupted his panegyric long enough to 

 enumerate some of the practical results of the Peau- 

 cellier linkage. He said that Mr. Penrose, the 

 eminent architect and surveyor to St. Paul's Cathe- 

 dral, had "put up a house-pump worked by a negative 

 Peaucellier cell, to the great wonderment of the 

 plumber employed, who could hardly believe his 

 senses when he saw the sling attached to the piston- 

 rod moving in a true vertical line, instead of wobbling 

 as usual from side to side.'' Sylvester could see no 

 reason "why the perfect parallel motion should not 

 be employed with equal advantage in the construc- 

 tion of ordinary water-closets." The linkage was to 

 be employed by "a gentleman of fortune" in a marine 

 engine for his yacht, and there was talk of using it to 

 guide a piston rod "in certain machinery connected 

 with sonre new apparatus for the ventilation and 

 filtration of the air of the Houses of Parliament." In 

 due course, Mr. Prim, "engineer to the Houses," was 

 pleased to show his adaptation of the Peaucellier 

 linkage to his new blowing engines, which proved to 

 be e.xceptionally quiet in their operation (fig. 25).'"^ 

 A bit on the ludicrous side, also, was Sylvester's 78-bar 

 linkage that traced a straight line along the line con- 

 necting the two fixed centers of the linkage.*' 



Before dismissing with a smile the quaint ideas of 

 our Victorian forbears, however, it is well to ask, 88 

 years later, whether some rather elaborate work re- 

 ported recently on the synthesis of straight-line mecha- 

 nisms is more to the point, when the principal objective 

 appears to be the moving of an indicator on a "pleas- 

 ing, expanded" (i.e., squashed flat) radio dial.*' 



But Professor Sylvester was more interested, really, 

 in the mathematical possibilities of the Peaucellier 

 linkage, as no doubt our modern investigators are. 

 Through a compounding of Peaucellier mechanisms, 



■"5 Sylvester, op. cit. (footnote 41), p. 181. 



" Ihid., pp. 182, 183, 188, 193. 



*' Kempe, op. cit. (footnote 21), p. 17. 



*' Machine Design, December 1954, vol. 26, p. 210. 



206 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



