CONTENTS. 



PAGE 



INTRODUCTION . 1 



CHAPTER I. 



TWISTS AND WRENCHES. 



1. Definition of the word Pitch ......... 6 



2. Definition of the word Screw 7 



3. Definition of the word Twist ......... 7 



4. A Geometrical Investigation .......... 8 



5. The canonical form of a Small Displacement ...... 9 



6. Instantaneous Screws 10 



7. Definition of the word Wrench 10 



8. Restrictions . . 11 



CHAPTER II. 

 THE CYLTNDROID. 



9. Introduction 15 



10. The Virtual Coefficient 17 



11. Symmetry of the Virtual Coefficient ........ 18 



12. Composition of Twists and Wrenches 18 



13. The Cylindroid . 19 



14. General Property of the Cylindroid 21 



15. Particular Cases 22 



16. Cylindroid with One Screw of Infinite Pitch 22 



17. Form of the Cylindroid in general 24 



18. The Pitch Conic 24 



19. Summary 24 



62 



