M, Persoz, professor of chemistry at the Conservatoire des Arts et Metiers, of Paris, says the London Engineer, has just published a most interesting discovery of his, by which photegraphy may be applied to the ornamenting of silk stuffs. The bichromate of potash is a substance commonly used in photography, being extremely sensitive to light. If a piece of silk stuff impregnated with this salt be exposed to the rays of light penetrating through the fissures of the window blinds in a closed room, the points where the stuff has received these rays of light will assume a peculiar reddish tint. Now, suppose a piece of metal, or of strong paper, to be cut out after a given pattern, and to be laid on a piece of silk prepared as before, if expoed to the sun, or, better still, to simple daylight, the pattern will be reproduced in a few seconds. The pale red which the exposed parts acted upon assume, is so permanent that nothing can destroy it ; nay, it will fix other colors, such as madder, campeachy, c., just like a mordant, and in that case it will modify the color of those substances in absorbing it. The process may be varied as follows :—Let a fern leaf be phteed upon a piece of prepared silk, and kept flat upon it by a pane of glass ; then that part of the silk which is protected by the leaf will retain its original color, while all the rest will receive the impression of light, as above described, forming the ground upon which the figure of the leaf will appear in white, grey, or other color the silk may have had before the operation. The richest patterns may be thus obtained on plain silks, and at a comparatively small expense.