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. * * * * * PHOTOGRAPHIC PICTURES.--A Selection of the above beautiful Productions may be seen at BLAND & LONG'S, 153. Fleet Street, where may also be procured Apparatus of every Description, and pure Chemicals for the practice of Photography in all its Branches. Calotype, Daguerreotype, and Glass Pictures for the Stereoscope. BLAND & LONG, Opticians, Philosophical and Photographical Instrument Makers, and Operative Chemists, 153. Fleet Street. * * * * * PHOTOGRAPHIC PORTRAITS and VIEWS by the Collodion and Waxed Paper Process. Apparatus, Materials, and Pure Chemical Preparation for the above processes, Superior Iodized Collodion, known by the name of Collodio-iodide or Xylo-iodide of Silver, 9d. per oz. Pyro-gallic Acid, 4s. per drachm. Acetic Acid, suited for Collodion Pictures, 8d. per oz. Crystallizable and perfectly pure, on which the success of the Calo-typist so much depends, 1s. per oz. Canson Frère's Negative Paper, 3s.; Positive do., 4s. 6d.; La Croix, 3s.; Turner, 3s. Whatman's Negative and Positive, 3s. per quire. Iodized Waxed Paper, 10s. 6d. per quire. Sensitive Paper ready for the Camera, and warranted to keep from fourteen to twenty days, with directions for use, 11 x 9, 9s. per doz.; Iodized, only 6s. per doz. GEORGE KNIGHT & SONS (sole Agents for Voightlander & Sons' celebrated Lenses), Foster Lane, London. * * * * * 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. * * * * *