of the patterns of their predecessors. Professors Woods 

 and Stahl, at the Universities of IlUnois and Purdue, 

 respectively, who published their Elementary Mechanism 

 in 1885, said in their preface what has been said by 

 many other American authors and what should have 

 been said by many more. "We make little claim to 

 originality of the subject-matter," wrote Woods and 

 Stahl, "free use having been made of all available 

 matter on the subject .... Our claim to considera- 

 tion is based almost entirely on the manner in which 

 the subject has been presented."' Not content with 

 this disclaimer, they continued: "There is, in fact, 

 very little room for such originality, the ground having 

 been almost completely covered by previous 

 writers." ''' 



The similarity and aridity of kinematics textbooks 

 in this country from around 1910 are most striking. 

 The generation of textbook writers following 

 MacCord, Woods and Stahl, Barr of Cornell, Robin- 

 son of Ohio State, and Schwamb and Merrill managed 

 to squeeze out any remaining juice in the subject, and 

 the dessication and sterilization of textbooks was 

 nearly complete when my generation used them in 

 the 1930's. Kinematics was then, in more than one 

 school, very nearly as it was characterized by an 

 observer in 1942 — "on an intellectual par with 

 mechanical drafting." "^ I can recall my own naive 

 belief that a textbook contained all that was known of 

 the subject; and I was not disabused of my belief by 

 my own textbook or by my teacher. I think I detect 

 in several recent books a fresh, less final, and less tidy 

 treatment of the kinematics of mechanisms, but I 

 would yet recommend that anyone who thinks of 

 writing a textbook take time to review, carefully and 

 at first hand, not only the desk copies of books that 

 he has accumulated but a score or more of earlier 

 works, covering the last century at least. Such a 

 study should result in a better appreciation of what 

 constitutes a contribution to knowledge and what 

 constitutes merely the ringing of another change. 



The author of the contentious article that appeared 

 in Mechanical Engineering in 1942 under the title 

 "What is Wrong with Kinematics and Mechanisms?" 

 made several pronouncements that were questioned 

 by various readers, but his remarks on the meagerness 

 of the college courses of kinematics and the "curious 



fact" that the textbooks "are all strangely similar in 

 their incompleteness" went unchallenged and were, 

 in fact, quite timely.'^' 



It appears that in the early 1940's the general class- 

 room treatment of accelerations was at a level well 

 below the existing knowledge of the subject, for in a 

 series of articles by two teachers at Purdue attention 

 was called to the serious consequences of errors in 

 acceleration analysis occasioned by omitting the 

 Coriolis component."'' These authors were reversing 

 a trend that had been given impetus by an article 

 written in 1920 by one of their predecessors, Henry 

 N. Bonis. The earlier article, appearing in a prac- 

 tical-and-proud-of-it technical magazine, demon- 

 strated how the acceleration of a point on a flywheel 

 governor might be determined "without the use of the 

 fictitious acceleration of Coriolis." The author's 

 analysis was right enough, and he closed his article 

 with the unimpeachable statement that "it is better 

 psychologically for the student and practically for the 

 engineer to understand the fundamentals thoroughly 

 than to use a complex formula that may be mis- 

 applied." However, many readers undoubtedly read 

 only the lead paragraph, sagely nodded their heads 

 when they reached the word "fictitious," which con- 

 firmed their half-formed conviction that anything as 

 abstruse as the Coriolis component could have no 

 bearing upon a practical problem, and turned the 

 page to the "practical kinks" section."" 



Less than 20 years ago one might have read in 

 Mechanical Engineering that "Practical machinery does 

 not originate in mathematical formulas nor in 

 beautiful vector diagrams." While this remark 

 was in a letter evoked by aii article, and was not a 

 reflection of editorial policy, it was nevertheless 

 representative of an element in the American tradition 

 of engineering. The unconscious arrogance that 

 is displayed in this statement of the "practical" 

 designer's creed is giving way to recognition of the 

 value of scholarly work. Lest the scholar develop 

 arrogance of another sort, however, it is well to 



i'3 Arthur T. Woods and Albert W. Stahl, Elementary Mecha- 

 nism, New York, 1885. 



"■• Mechanical Engineering, October 1942, vol. 64, p. 745. 



"^ De Jonge, op. cit. (footnote 78). 



"8 A. S. Hall and E. S. Ault, "How Acceleration Analysis 

 Can Be Improved," Machine Design, February 1943, vol. 15, 

 pp. 100-102, 162, 164; and March 1943, vol. 15, pp. 90-92, 

 168, 170. See also A. S. Hall, "Teaching Coriolis' Law," 

 Journal oj Engineering Education, June 1948, vol. 38, pp. 757-765. 



"' Henry N. Bonis, "The Law of Coriolis," American Machin- 

 ist, November 18, 1920, vol. 53, pp. 928-930. See also "Accel- 

 eration Determinations," American Machinist, November 25 and 

 December 2, 1920, vol. 53, pp. 977-981 and 1027-1029. 



PAPER 27: KINEMATICS FROM THE TIME OF WATT 



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