Page:A Treatise on Painting.djvu/257



 a darkish body terminates upon a light ground, it will appear detached from that ground; because all opake bodies of a curved surface are not only dark on that side which receives no light, and consequently very different from the ground; but even that side of the curved surface which is enlightened, will not carry its principal light to the extremities, but have between the ground and the principal light a certain demi-tint, darker than either the ground or that light.   thing white will appear whiter, by being opposed to a dark ground; and, on the contrary, darker upon a light ground. This we learn from observing snow as it falls; while it is descending it appears darker against the sky, than when we see it against an open window, which (owing to the darkness of the inside of the house) makes it appear very white. Observe also, that snow appears to fall very quick and in a great quantity when near the eye; but when at some distance, it seems to come down slowly, and in a smaller quantity . 2