Instructions and Specimens in every Branch of the Art. * * * * * PHOTOGRAPHY.--XYLO-IODIDE OF SILVER, prepared solely by R. W. THOMAS, has now obtained an European fame; it supersedes the use of all other preparations of Collodion. Witness the subjoined Testimonial. "122. Regent Street "Dear Sir,--In answer to your inquiry of this morning, I have no hesitation in saying that your preparation of Collodion is incomparably better and more sensitive than all the advertised Collodio-Iodides, which, for my professional purposes, are quite useless when compared to yours. "I remain, dear Sir, "Yours faithfully, "N. HENNEMAN. Aug. 30. 1852. to Mr. R.W. Thomas." MR. R. W. THOMAS begs most earnestly to caution photographers against purchasing impure chemicals, which are now too frequently sold at very low prices. It is to this cause nearly always that their labours are unattended with success. Chemicals of absolute purity, especially prepared for this art, may be obtained from R. W. THOMAS, Chemist and Professor of Photography, 10. Pall Mall. N.B.--The name of Mr. T.'s preparation, Xylo-Iodide of Silver, is made use of by unprincipled persons. To prevent imposition each bottle is stamped with a red label bearing the maker's signature. * * * * * TO PHOTOGRAPHERS.--Pure Chemicals, with every requisite for the practice of Photography, according to the instructions of Hunt, Le Gray, Brébisson, &c. &c., may be obtained of WILLIAM BOLTON, Manufacturer of pure chemicals for Photographic and other purposes. Lists of Prices to be had on application. 146. Holborn Bars. * * * * * 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. * * * * * TO PHOTOGRAPHERS.--MR. PHILIP DELAMOTTE begs to announce that he has now made arrangements for printing Calotypes in large or small quantities, either from Paper or Glass Negatives. Gentlemen who are desirous of having good impressions of their works, may see specimens of Mr. Delamotte's Printing at his own residence, 38. Chepstow Place, Bayswater, or at MR. GEORGE BELL'S, 186. Fleet Street. * * * * *