A Transparent Colour being laid on another Colour of different kind, forms a third, partaking of each of the two simples that compose it. This is observable in Smoke, which meeting with Soot in its Passage through the Chimney, becomes Blue; but being mounted into the Air, which is Azure it self, appears Brown or Reddish; thus Purple laid upon Blue forms a Violet, and Blue mingled with Yellow, becomes Green; Saffron Colour laid upon White, turns Yellow, and White upon Black, produces Azure; which last will be brighter, as the White and Black are more excellent.