Dated 1860-1875. From Working papers and experimental observations relating to optics including polarisation, photometry, spectra and the characteristics of light, [1840-1875].

Observations on the consistency of various colours, notably including the isolation of colours by chemical means; colours of gold alloys; the colours of solid bodies; alterations in the colour of various liquids under different lighting conditions; brief reflections on the theoretical explanation for solar absorption spectra and experiments to determine the absorption spectra of numerous compounds; commonplaces and extracts from published works on the subject of colour.