PHILADELPHIA ACADEMY OF FINE ARTS.—The spring exhibition of this society promises to be unusually attractive. The liberal prizes offered by the managers to induce competition, have awakened the spirit of not only our own, but foreign artists. We shall next month have an opportunity to notice these works in detail, and hope to find some home productions which will compare favorably with those received from abroad. Among the latter is a magnificent piece of coloring by VAN SCHENDEL of Brussels, representing Ahasuerus king of the Persians and Medes, in the midst of his gorgeous court, as described in the Book of Esther. SCHOTEL of Medembled, Holland, has sent out two marine views, a department in which he is justly celebrated. One of these, entitled “Wrecking and Succor,” possesses much energy, and the other, “The Schelde by a fresh gale,” will be highly prized by all the lovers of art. There are also two works by Carl Hubner of Dusseldorf, called “The Recovery,” and “The Happy Moment,” which evince high artistic excellence. G. F. DIDAY of Bremen, has sent over two beautiful views of the High Alps in Switzerland, and J. SCHOPPE of Berlin, a scene descriptive of a Spanish comedy by Moneto, which he entitles Amphitrite and Donna Diana. All these, and others of minor excellence, will be noticed more fully hereafter. * * * * * THE AMERICAN ART UNION.—The walls of the new gallery of this institution already present many beautiful specimens of art. A picture by LEUTZE, called the “Knight of Sayn and the Gnomes,” is particularly admired. The story, as described by G. G. FOSTER, Esq. in his spicy little paper, the Merchants’ Day Book, is of a knight who fell in love with a beautiful damsel, whose father would consent to the match only on condition that the lover would ride up the steep rocks on which his castle was built. This was clearly an impossible feat; but the king of the Gnomes came secretly and offered, if the knight of Sayn would fill up a silver mine that had been opened on his domain, to assist him in crossing safely the bridge of love. The action of the picture is at the moment that the knight rides over the last frightful fissure, upon a bridge composed of rocks, supported and held in their places beneath his charger’s hoofs, by the sturdy gnomes, while the king of the earth elfins stands proudly on the other side with his royal sceptre in his hand, to welcome his _protégé_ safely over. Far above is the father’s castle, with the lady and her attendants, watching the dauntless rider and waving their scarfs over his head. The whole of this picturesque and charming scene is handled in the most admirable manner. The gnomes couching like little atlases, under the heavy rocks across which the knight is passing—the irresistible comicry of the burly gnome king—the fiery prancing war-horse—the knight himself, waving his cap gallantly to his mistress, while he sits his steed with the air of a perfect