LIST OF ILLUSTRATIONS 



1. Origin of Roman Numerals 8 



2. First Proposition of Euclid 35 



3. Equilibrium Through Opposing Thrusts ... 42 



4. Centre of Gravity 44 



5. Simple Composition of Forces ..... 47 



6. Complex Composition of Forces ..... 48 



7. Parallel Forces 5 



8. Levers , 5 1 



9. The Pulley . -52 



10. The Inclined Plane 53 



11. Angles of Incidence and Eeflexion .... 58 



12. Velocity of a Falling Body 61 



13. The Pendulum 63 



14. Liquid Level Surface , . 69 



15. The Siphon . . 80 



1 6. Relation of Force to Distance ..... 97 



17. Reflexion of Energy 99 



18. Reflecting Mirrors 100 



19. Action of Convex Surfaces ...... 101 



20. Action of Concave Surfaces ...... 101 



21. Refraction 105 



22. Aerial Currents 150 



23. Two Aspects of the Earth . . . . . .156 



24. Geological Strata . . . . . . . 167 



25. Triangular Measurements 177 



26. Horse-Tail . . . . . . . -191 



27. Tunicate ......... 192 



28. Animal Cell 195 



