The elementary spirits (continued the Prefect) are not so able painters as naturalists; thou shalt judge by their way of working. Thou knowest that the rays of light, reflected from different bodies, make a picture and paint the bodies upon all polished surfaces, on the retina of the eye, for instance, on water, on glass. The elementary spirits have studied to fix these transient images: they have composed a most subtile matter, very viscous, and proper to harden and dry, by the help of which a picture is made in the twinkle of an eye. They do over with this matter a piece of canvas, and hold it before the objects they have a mind to paint. The first effect of the canvas is that of a mirrour; there are seen upon it all the bodies far and near, whose image the light can transmit. But what the glass cannot do, the canvas, by means of the viscous matter, retains the images. The mirrour shows the objects exactly, but keeps none; our canvases show them with the same exactness, and retains them all. This impression of the images is made the first instant they are received on the canvas, which is immediately carried away into some dark place; an hour after, the subtile matter dries, and you have a picture so much the more valuable, as it cannot be imitated by art nor damaged by time. We take, in their purest source, in the luminous bodies, the colours which painters extract from different materials, and which time never fails to alter. The justness of the design, the truth of the expression, the gradation of the shades, the stronger or weaker strokes, the rules of perspective, all these we leave to nature, who, with a sure and never-erring hand, draws upon our canvases images which deceive the eye and make reason to doubt, whether, what are called real objects, are not phantoms which impose upon the sight, the hearing, the feeling, and all the senses at once. The Prefect then entered into some physical discussions, first, on the nature of the glutinous substance which intercepted and retained the rays; secondly, upon the difficulties of preparing and using it; thirdly, upon the struggle between the rays of light and the dried substance; three problems, which I propose to the naturalists of our days, and leave to their sagacity. Mean while, I could not take off my eyes from the picture. A sensible spectator, who from the shore beholds a tempestuous sea, feels not more lively impressions: such images are equivalent to the things themselves. The Prefect interrupted my extasy. I keep you too long (says he) upon this storm, by which the elementary spirits designed to represent allegorically the troublesome state of this world, and mankind’s stormy passage through the same: turn thy eyes, and behold what will feed thy curiosity and increase thy admiration. CHAP. XVIII. THE GALLERY OR THE FORTUNE OF MANKIND.