Figures Painted on a bright and illumined Ground, will appear with a greater Relievo, than if Painted on a Ground more obscure: The reason is, that in order to give your Figure the greater force and freedom, you make that part of it, which is the furthest removed from the Light, the least illumined by it; whence it becomes obscure; so that coming to terminate on an obscure Ground, its extremes are render'd dim, and appear confused, and of a Piece with the Ground it self: Insomuch that without the assistance of some Reflex, to be conducted thither, your work will remain devoid, both of Spirit and Grace; nor will any part of it, excepting its Lights, be so much as seen, at a distance. And this is the effect of an obscure Ground; which prevents the Relievo of Figures, cutting off, and mutilating them of all their unillumined parts.