_Sect._ I. _Prerogatives of Sight._ _Art._ 2. Position. 3. Distance. {xv} _Sect._ II. _Prerogatives of Hearing._ _Art._ 4. Musical Intervals. 5. Chords. 6. Rhythm. _Sect._ III. _The Paradoxes of Vision._ _Art._ 7. First Paradox. 8. Second Paradox. 9. The same for near Objects. 10. Objections answered. _Sect._ IV. _The Perception of Visible Figures._ _Art._ 11. Brown's Opinion. CHAP. III. SUCCESSIVE ATTEMPTS AT THE SCIENTIFIC APPLICATION OF THE IDEA OF A MEDIUM 322 _Art._ 1. Introduction. 2. Sound. 3. Light. 4. Heat. CHAP. IV. OF THE MEASURE OF SECONDARY QUALITIES 333 _Sect._ I. _Scales of Qualities in General._ _Art._ 1. Intensity. 2. Quantity and Quality. _Sect._ II. _The Musical Scale._ _Art._ 3. Musical Relations. 4. Musical Standard. _Sect._ III. _Scales of Colour._ _Art._ 5. The Prismatic Scale. 6. Newton's Scale. 7. Scales of Impure Colours. 8. Chromatometer. _Sect._ IV. _Scales of Light._ _Art._ 9. Photometer. 10. Cyanometer. _Sect._ V. _Scales of Heat._ _Art._ 11. Thermometers. 12. Their progress. 13. Fixed Points. 14. Concordance of Thermometers. 15. Natural Measure. 16. Law of Cooling. {xvi} 17. Theory of Exchanges. 18. Air Thermometer. 19. Theory of Heat. 20. Other Instruments. _Sect._ VI. _Scales of other Quantities._ _Art._ 21. Tastes and Smells. 22. Quality of Sounds. 23. Articulate Sounds. 24. Transition. BOOK V. OF THE PHILOSOPHY OF THE MECHANICO-CHEMICAL SCIENCES. CHAP. I. ATTEMPTS AT THE SCIENTIFIC APPLICATION OF THE IDEA OF POLARITY 359 _Art._ 1. Introduction of the Idea. 2. Magnetism. 3. Electricity. 4. Voltaic Electricity. 5. Light. 6. Crystallization. 7. Chemical Affinity. 8. General Remarks. 9. Like _repels_ like. CHAP. II. OF THE CONNEXION OF POLARITIES 371 _Art._ 1. Different Polar Phenomena from one Cause. 2. Connexion of Magnetic and Electric Polarity. 3. Ampère's Theory. 4. Faraday's views. 5. Connexion of Electrical and Chemical Polarity. 6. Davy's and Faraday's views 7. Depend upon Ideas as well as Experiments. 8. Faraday's Anticipations. 9. Connexion of Chemical and Crystalline Polarities. 10. Connexion of Crystalline and Optical Polarities. 11. Connexion of Polarities in general. 12. Schelling's Speculations. 13. Hegel's vague notions. 14. Ideas must guide Experiment. {{1}} THE PHILOSOPHY OF THE INDUCTIVE SCIENCES.