Now, as I advanced neither more nor less in my paper, why does Mr. Wall turn round and caution your readers not to receive such simple truths uttered by me? I was not aware that Mr. Wall had forestalled me in laying down such rules; for at that date I was in America, and did not see the _News_; but, on turning over the volume for 1861 the other day, since this discussion began, I there saw and read, with surprise, the above in his article on backgrounds. I am perfectly aware that I did not say all that I might have said on perspective in my paper; but the little I did say was true in principle, and answered my purpose. When Mr. Wall (in the second paragraph of his last letter) speaks of the "principal visual ray going from the point of distance to the point of sight, and forming a right angle to the perspective plane," it seems to me that he is not quite sure of the difference between the points of _sight_, _distance_, and _observation_, or of the relation and application of one to the other. However, his coming articles on perspective will settle that. It also appears to me that he has overlooked the fact that my diagrams were _sections_, showing the perspective inclination and declination of the lines of a parallelogram towards the point of sight. In my paper I said nothing about the _point of distance_; with that I had nothing to do, as it was not my purpose to go into all the dry details of perspective. But I emphatically deny that anything like a "bird's eye view" of the figure could possibly be obtained by following any of the rules I laid down. In my paper I contended for the camera being placed on a level with the head of the sitter, and that would bring the line of the horizon in a pictorial background also as high as the head of the sitter. And if the horizon of the pictorial background were placed anywhere else, it would cause the apparent overlapping of _two_ conditions of perspective in the resulting photograph. These were the errors I endeavoured to point out. I maintain that my views are perfectly correct, and can be proved by geometrical demonstration, and the highest artistic and scientific testimony. I wish it to be clearly understood that I do not advocate the use of pictorial backgrounds, and think I pretty strongly denounced them; but if they _must_ be used by photographers, either to please themselves or their customers, let them, for the credit of our profession, be as true to nature as possible. I think I have now answered all the points worth considering in Mr. Wall's letter, and with this I beg to decline any further correspondence on the subject.--I am, yours, &c., J. Werge. _March 5th, 1866._ NOTES ON PICTURES IN THE NATIONAL GALLERY.