Again: Mr. Wall is surely not prepared to advance the dictum that no one can know anything about art but a professional artist. If so, how does he reconcile that opinion with the fact of his great and oft-quoted authority, Ruskin, not being an artist, but simply, in his public character, a voluminous writer on art, not always right, as many artists and photographers very well know. Mr. Wall objects to my use of the word "artist," but he seems to have overlooked the fact that I used the quotation marks to show that I meant to apply it to the class of self-styled artists, or men who arrogate to themselves a title they do not merit--not such men as Landseer, Maclise, Faed, Philips, Millais, and others of, and not of, the "Forty." Mr. Wall may be an artist. I do not say he is not. He also is, or was, a painter of backgrounds. So he can apply to himself whichever title he likes best; but whether he deserves either one or the other, depends on what he has done to merit the appellative. Mr. Wall questions the accuracy of the principles I advocated in my paper. I contend that I am perfectly correct, and am the more astonished at Mr. Wall when I refer to vol. v., page 123, of the _Photographic News_. There I find, in an article bearing his own name, and entitled "The Technology of Art as Applied to Photography," that he says:-- "If you make use of a painted cloth to represent an interior or out-door view, the horizontal line must be at somewhere about the height which your lens is most generally placed at, and the vanishing point nearly opposite the spot occupied by the camera. * * * * I have just said that the horizon of a landscape background and the vanishing point should be opposite the lens; I may, perhaps, for the sake of such operators as are not acquainted with perspective, explain why. The figure and the background are supposed to be taken at one and the same time, and the camera has the place of the spectator by whom they are taken. Now, suppose we have a real figure before a real landscape: if I look up at a figure I obtain one view of it, but if I look down on it, I get another and quite a different view, and the horizon of the natural landscape behind the figure is always exactly the height of _my_ eye. To prove this, you may sit down before a window, and mark on the glass the height of the horizon; then rise, and, as you do so, you will find the horizon also rises, and is again exactly opposite your eye. A picture, then, in which the horizontal line of the background represents the spectator as looking up at the figure from a position near the base line, while the figure itself indicates that the same spectator is at that identical time standing with his eyes on a level with the figure's breast or chin--such productions are evidently false to art, and untrue to nature. * * * * The general fault in the painted screens we see behind photographs arises from introducing too many objects."