Part III. Magnetism: 1. Elementary theory of magnetism; 2. Magnetic force and magnetic induction; 3. Particular forms of magnets; 4. Induced magnetization; 5. Magnetic problems; 6. Weber's theory of magnetic induction; 7. Magnetic measurements; 8. Terrestrial magnetism; Part IV. Electromagnetism: 1. Electromagnetic force; 2. Mutual action of electric currents; 3. Induction of electric currents; 4. Induction of a current on itself; 5. General equations of dynamics; 6. Application of dynamics to electromagnetism; 7. Electrokinetics; 8. Exploration of the field by means of the secondary circuit; 9. General equations; 10. Dimensions of electric units; 11. Energy and stress; 12. Current-sheets; 13. Parallel currents; 14. Circular currents; 15. Electromagnetic instruments; 16. Electromagnetic observations; 17. Electrical measurement of coefficients of induction; 18. Determination of resistance in electromagnetic measure; 19. Comparison of electrostatic with electromagnetic units; 20. Electromagnetic theory of light; 21. Magnetic action on light; 22. Electric theory of magnetism; 23. Theories of action at a distance; Index.