Published in 1780, this was the first work to suggest that specific receptors were responsible for communicating auditory and optical sensation.

Preface; Part I. Observations on the Senses: 1. Of vision; 2. Of taste, smell and feeling; 3. Of hearing; 4. Other phenomena of hearing; 5. An appendix to the foregoing essay; Part II. A Treatise on Harmonic Sounds: Introduction; The theory of harmonic sounds; Part III. An Inquiry into Combustion: 1. The principal phenomena of incombustible bodies; 2. The phenomena of combustible bodies; 3. Of the principle on which combustion depends; 4. Of the phlogiston; 5. Of the heat and light attending combustion; 6. Of the continuance of combustion; 7. A speculation; 8. Of the origin of heat in combustion; 9. Of the light and colours which arise on the ignition, and combustion of bodies; 10. Of respiration, and animal heat; 11. Of the vital and other motions of the body; 12. Of the action of the fibres, or muscular motion; Appendix.