for its adoption. Many of the remarks of Aristotle138 and Theophrastus139 on the production of black, are derived from the observation of the action of fire, and on one occasion, the former distinctly alludes to the terracotta kiln. That the above opinion as to the nature of black was prevalent in the sixteenth century, may be inferred from Lomazzo, who observes,—"Quanto all' origine e generazione de' colori, la frigidità è la madre della bianchezza: il calore è padre del nero."140 The positive coldness of black may be said to begin when it approaches grey. When Leonardo da Vinci says that black is most beautiful in shade, he probably means to define its most intense and transparent state, when it is furthest removed from grey.
NOTE V.—Par. 555.
The nature of vehicles or liquid mediums to combine with the substance of colours, has been frequently discussed by modern writers on art, and may perhaps be said to have received as much attention as it deserves. Reynolds smiles at the notion of our not having materials equal to those of former times, and indeed, although the methods of individuals will always differ, there seems no reason to suppose that any great technical secret has been lost. In these inquiries, however, which relate merely to the mechanical causes of bright and durable colouring, the skill of the painter in the adequate employment of the higher resources of his art is, as if by common consent, left out of the account, and without departing from this mode of considering the question,