CONTENTS. 



INTRODUCTION. 



PAGE. 



I. On the Canonical Form of a System of Forces applied to a Rigid Body, xvii 



II. On the Canonical Form of the Displacement of a Rigid Body, . xviii 



CHAPTER I. 



TWISTS AND WRENCHES. 

 SECT. 



1. Definition of the word Screw, . . . -. . . . . I 



2. Definition of the word Twist, . " . . '." L .... 3 



3. Instantaneous Screws, ..'.'..'. . . . 4 



4. Definition of the word Wrench, . ' . ' ib. 



5. Notation for Twists, Wrenches, and Twisting Motions, ... 5 



6. Restriction of the Forces, ..'.'.'.'. . . . 7 

 7 The Energy of Position, . ' , ".. '.'.'. . . . ib. 



8. Theorem, .'.'...'/ 8 



9. Theorem, ib. 



10. Theorem, ..'.". . . . . . . . 10 



11. Concluding Remarks, n 



CHAPTER II. 

 THE CYLINDROID. 



12. Introduction, II 



13. On the Virtual Co-efficient of a Pair of Screws, . . . . ib. 



14. Symmetry of the Virtual Co-efficient, 13 



15. Composition of Twists and Wrenches, ib. 



16. The Cylindroid, 14 



17. General Property, I 7 



1 8. Particular Cases, 18 



19. Form of the Cylindroid, . I 9 



20. The Pitch Conic, ib - 



21. Summary, 2O 



