I 



B ON GRAPHIC METHODS IN MECHANICAL SCIENCE. 427 



^Bcale appears to have been the first sliding rule ever made, and has since 



^B>een followed by a very large number of others.' 



Bp Writers on graphic statics recognise the slide rule as an example of 

 the graphical method of calculation. Culmann, in the second edition of 

 his book, gives a treatment of the subject (which he did not do in his first 

 edition), and states in the preface that ' the chapter on sliding calculation 

 was added to that on graphical calculation. It consists really of many 

 treatises on sliding calculation. Addition of logarithms is not considered as 

 a consequent row of lines, but rules are given on independent figures 

 placed opposite each other, by whose means the number of rules is 

 immensely increased. Moreover, this very useful little instrument is 

 much too little used, and I thought to add to its extension by introducing 

 its theory in graphical calculation, to which it properly belonged.' 



The use and theory of the slide rule are fully described in the English 

 treatises mentioned in the footnote below,^ and need not be further dealt 

 with. 



It is also treated, in addition to Culmann, by various other foreign 

 writers, in works on graphic statics. Favaro, amongst others, states that 

 Sedlaczek ^ mentions sixteen different kinds of instruments using log- 

 arithmic division, as follows : — 



1. The ordinary sliding rule. 



2. Rule of d'Aesterle. 



3. The calculating-rule of Lenoir. 



4. The rule of Schwind. 



5. Engineer's sliding rule, 



6. The rule of L. C. Schulz. 



7. The inverted slide rule. 



8. The rule of Higgison. 



9. The improved calculating-rule. 



10. A rule for millwrights. 



11. A rule for marine use. 



12. Sliding rule for timber measurements. 



13. Dr. Roget's sliding: rule. 



14. A sliding rule for calculating prices. 



15. Chemical sliding rule. Wollaston's (' Phil. Trans. U.S.,' 1814). 



16. Sedlacrek's slide rule for interpolation. 



The following slide rules are mentioned by Mr. Heather : — 



1. The Routledge. 



2. Bayley's slide rule. 



3. The Kentish slide rule. 



' According to de Morgan {see his valuable article on the Slide Kule in the English 

 Cyeloptedid), the slide rule was invented by Oughtred. 



^ The Slide Rttle, and Horn to Use It, by Charles Hoare, C.E. (Weale Series.) 

 Crosby, Lockwood, & Co. 



Tnstri/ctions for the use of Carpenter's Improved Slide Rule, by Edward Preston. 

 Josiah Allen, Birmingham. 



Handhnok of the Slide Rule, by W. H. Bayley. Bell, London. 



Handbook of the Boiihle Slide Ride, by W. H. Bayley. Bell, London. 



The Theory and Practice of the Slide Rule, by Lieut. -Col. J. E. Campbell. E. & F. 

 N. Spon, London. 



And the following American books : — The Slide Rule Practically Considered, 

 by W. H. Burgh ; and The Slide Rule Simplified, by R. Biddell, Philadelphia. 



' Le<ions de Statique graphique, Antonio Favaro. Paris, 1885. 



