PHOTOGRAPHIC CHEMICALS of absolute Purity, especially prepared for this Art, may be procured from R. W. THOMAS, Operative Chemist, 10. Pall Mall, whose well-known Preparation of Xylo-Iodide of Silver is pronounced by the most eminent scientific men of the day to excel every other Photographic Compound in sensitiveness, and in the marvellous vigour uniformly preserved in the middle tints of pictures produced by it. MR. R. W. THOMAS cautions Photographers against unprincipled persons who (from the fact of Xyloidin and Collodion being synonymous terms) would lead them to imagine that the inferior compound sold by them at half the price is identical with his preparation. In some cases, even the name of MR. T.'s Xylo-Iodide of Silver has been assumed. In order to prevent such dishonourable practice, each bottle sent from his Establishment is stamped with a red label bearing his signature, to counterfeit which is felony. Prepared solely by R. W. THOMAS, Chemist, &c., 10. Pall Mall. * * * * * PHOTOGRAPHY.--Collodion (Iodized with the Ammonio-Iodide of Silver).--J. B. HOCKIN & CO., Chemists, 289. Strand, were the first in England who published the application of this agent (see _Athenæum_, Aug. 14th). Their Collodion (price 9d. per oz.) retains its extraordinary sensitiveness, tenacity, and colour unimpaired for months: it may be exported to any climate, and the Iodizing Compound mixed as required. J. B. HOCKIN & CO. manufacture PURE CHEMICALS and all APPARATUS with the latest Improvements adapted for all the Photographic and Daguerreotype processes. Cameras for Developing in the open Country. GLASS BATHS adapted to any Camera. Lenses from the best Makers. Waxed and Iodized Papers, &c. * * * * * THE GENTLEMAN'S MAGAZINE for JANUARY 1853, which is the First Number of a New Volume, contains the following articles:-- 1. King Charles I. in the Isle of Wight. 2. Original Letters of Benjamin Franklin. 3. Farinelli and Pompadour. 4. Henry Newcome, the Manchester Puritan. 5. A Journey to Paris in 1736. 6. The Cloister Life of Charles V. 7. The Hill Intrenchments on the Borders of Wales, by T. Wright, F.S.A. (with Engravings). 8. Report of the Cambridge University Commission. 9. Correspondence of Sylvanus Urban:--1. Pictures of the Immaculate Conception. 2. The Relic of St. Mary Axe. 3. Harley Church, Salop. 4. Etymology of the word Many. With Notes of the Month, Reviews of New Publications, Historical Chronicle, and OBITUARY, including Memoirs of the Earl of Shrewsbury, Countess of Lovelace, Sir J. J. Guest, Miss Berry, Professor Empson, Mr. Serjeant Halcomb, &c. &c. A Specimen Number sent on the receipt of 2s. 6d. in Postage Stamps. NICOLS & SON, 25. Parliament Street. * * * * *