Almost of equal value with the pictures of this immortal artist, are his writings, part of which, unfortunately, have been lost, and others have remained in manuscript. His _Trattato della Pittura_, &c., appeared for the first time in 1651. It was translated into English, and published by John Senex, London, 1721. The most complete edition was published by Manzi, in Italian, in 1817. The learned connoisseur, Count Algarotti, esteemed this work so highly, that he regarded it the only work necessary to be put into the hands of the student. “With a deep insight into nature,” says Fiorillo, “Lionardo has treated in this book, of light, shades, reflections, and particularly of backgrounds. He perfectly understood, and has explained in the best way, that natural bodies being bounded mostly by curved lines, which have a natural softness, it is important to give this softness to the outlines; that this can be done only by means of the ground on which the object is represented; that the inner line of the surrounding ground, and the outer line of the object, are one and the same; nay, that the figure of the object becomes visible only by means of that which surrounds it; that even the colors depend upon the surrounding objects, and mutually weaken and heighten each other; that when objects of the same color are to be represented, one before the other, different degrees of light must be used to separate them from each other, since the mass of air between the eye and the object lessens and softens the color in proportion to the distance.” Among the works of Da Vinci, were Treatises on Hydraulics, Anatomy, Perspective, Light and Shadow, and the Anatomy of the Horse. The Ambrosian Library of Milan originally possessed sixteen volumes of his manuscripts. The French, during their occupancy of Milan, carried off twelve of these, (probably all there were then remaining) but only three of them reached Paris, one of which was published under the title of _Fragment d’un Traité sur les Mouvements du corps humain_. Only one volume was returned to Milan by the Allies in 1815. What abominable sacrilege! It is said that seven volumes more of his manuscripts were in the collection of the King of Spain. DA VINCI’S SKETCH BOOKS.