IMPROVEMENT IN COLLODION.--J. B. HOCKIN & CO., Chemists, 289. Strand, have, by an improved mode of Iodizing, succeeded in producing a Collodion equal, they may say superior, in sensitiveness and density of Negative, to any other hitherto published; without diminishing the keeping properties and appreciation of half tint for which their manufacture has been esteemed. Apparatus, pure Chemicals, and all the requirements for the practice of Photography. Instruction in the Art. * * * * * PHOTOGRAPHIC CAMERAS.--OTTEWILL'S REGISTERED DOUBLE-BODIED FOLDING CAMERA, is superior to every other form of Camera, for the Photographic Tourist, from its capability of Elongation or Contraction to any Focal Adjustment, its Portability, and its adaptation for taking either Views or Portraits.--The Trade supplied. Every Description of Camera, or Slides, Tripod Stands, Printing Frames, &c., may be obtained at his MANUFACTORY, Charlotte Terrace, Barnsbury Road, Islington. New Inventions, Models, &c., made to order or from Drawings. * * * * * PHOTOGRAPHIC APPARATUS, MATERIALS, and PURE CHEMICAL PREPARATIONS. KNIGHT & SONS' Illustrated Catalogue, containing Description and Price of the best forms of Cameras and other Apparatus. Voightlander and Son's Lenses for Portraits and Views, together with the various Materials, and pure Chemical Preparations required in practising the Photographic Art. Forwarded free on receipt of Six Postage Stamps. Instructions given in every branch of the Art. An extensive Collection of Stereoscopic and other Photographic Specimens. GEORGE KNIGHT & SONS, Foster Lane, London. * * * * * CYANOGEN SOAP for removing all kinds of Photographic Stains. Beware of purchasing spurious and worthless imitations of this valuable detergent. The genuine is made only by the inventor, and is secured with a red label pasted round each pot, bearing this signature and address:-- RICHARD W. THOMAS, Chemist, Manufacturer of pure Photographic Chemicals, 10. Pall Mall, and may be procured of all respectable Chemists in pots at 1_s._, 2_s._, and 3_s._ 6_d._ each, through MESSRS. EDWARDS, 67. St. Paul's Churchyard, and MESSRS. BARCLAY & CO., Farringdon Street, Wholesale Agents. * * * * * PHOTOGRAPHIC INSTITUTION.--An EXHIBITION of PICTURES, by the most celebrated French, Italian, and English Photographers, embracing Views of the principal Countries and Cities of Europe, is now OPEN. Admission 6_d._ A Portrait taken by MR. TALBOT'S Patent Process, One Guinea; Three extra Copies for 10_s._ PHOTOGRAPHIC INSTITUTION, 168. NEW BOND STREET. * * * * * PHOTOGRAPHIC PAPER.--Negative and Positive Papers of Whatman's, Turner's, Sanford's, and Canson Freres' make. Waxed-Paper for Le Gray's Process. Iodized and Sensitive Paper for every kind of Photography.