_Mr. Archer's Services to Photography._--In Vol. vii., p. 163., MR. HORNE seems very indignant at the idea that MR. ARCHER taught him to take pictures, and says MR. ARCHER'S published account will not succeed. Now I know that MR. ARCHER and myself did take pictures by his process as published. I also assert that neither MR. HORNE nor Mr. Fry made any collodion pictures before MR. ARCHER published his account in _The Chemist_, and, with the ordinary camera, that process must be the one now to give any chance of success, for without washing the plate the collodion will not keep five or six hours without staining. But as that process was not sufficiently quick, MR. ARCHER proposed to take the pictures in the bath itself; and I have one which I took in that way on the 16th of May, 1851. MR. HORNE, I think ungenerously, wishes to detract from MR. ARCHER'S merit, and to exalt himself and Mr. Fry at MR. ARCHER'S expense. I have a letter of Mr. Fry's, dated March 23, 1852, in which he says, "I with much pleasure accord to MR. ARCHER the credit he is fairly entitled to, of being the sole inventor of the collodion process." And another letter, wherein he says he "never sanctioned the insertion in any work of any article connected with the collodion process." I also know that MR. ARCHER prepared collodion for Messrs. Horne; that Messrs. Horne advertised it as prepared by MR. ARCHER; and that they were glad, when the thing was new, to avail themselves of MR. ARCHER'S assistance. W. BROWN. Ewell. _Mr. Weld Taylor's Iodizing Process._--The process I generally adopt in iodizing paper by the {219} ammonio-nitrate of silver, I have found to be the most certain of all, and I here give a formula for the benefit of your readers. They will find it admirably adapted for any objects in the shade, or any not lit by the sun's rays; it also has an excellent quality, of not darkening by exposure in the camera, as most other papers do. I have taken negatives with it all the winter, even at Christmas. It is rather slow, but certain; and as your readers try it and improve it, I hope they will communicate the results.