An aquatint from an 1816 book called "Fragments on the theory and practice of landscape gardening: including some remarks on Grecian and Gothic architecture, collected from various manuscripts in possession of the different noblemen and gentlemen, for whose use they were originally written; the whole tending to establish fixed principles in the respective arts." The book was authored by Humphry Repton (1752-1818) and his son John Adey Repton (1775-1860). This page is "Fragment XII, Concerning Colours," and presents a "diagram to explain the harmony of colours," showing relative proportions needed to show (at bottom left) "Morning, after the Sun is risen" versus (bottom right) "Morning twilight, before Sun rise." Color theory was a popular topic in the 19th century.