Instructions and Specimens in every Branch of the Art. GEORGE KNIGHT & SONS, Foster Lane, London. * * * * * PHOTOGRAPHIC APPARATUS MANUFACTORY, Charlotte Terrace, Barnsbury Road, Islington. T. OTTEWILL (from Horne & Co.'s) begs most respectfully to call the attention of Gentlemen, Tourists, and Photographers, to the superiority of his newly registered DOUBLE-BODIED FOLDING CAMERAS, possessing the efficiency and ready adjustment of the Sliding Camera, with the portability and convenience of the Folding Ditto. Every description of Apparatus to order. * * * * * SPECTACLES.--WM. ACKLAND applies his medical knowledge as a Licentiate of the Apothecaries' Company, London, his theory as a Mathematician, and his practice as a Working Optician, aided by Smee's Optometer, in the selection of Spectacles suitable to every derangement of vision, so as to preserve the sight to extreme old age. ACHROMATIC TELESCOPES, with the New Vetzlar Eye-pieces, as exhibited at the Academy of Sciences in Paris. The Lenses of these Eye-pieces are so constructed that the rays of Light fall nearly perpendicular to the surface of the various lenses, by which the aberration is completely removed, and a telescope so fitted gives one-third more magnifying power and light than could be obtained by the old Eye-pieces. Prices of the various sizes on application to WM. ACKLAND, Optician, 93. Hatton Garden, London. * * * * * {67} HAMILTON'S MODERN INSTRUCTIONS for the PIANOFORTE. Thirty-eighth Edition Price 4s. "So simple and clear are the directions laid down that any one with a moderate degree of application would have no difficulty in overcoming the intricacies of the instrument. The lessons are progressive, and the treatise is popular," &c.--Tallis's _London Weekly Paper_. ROBERT COCKS & CO.'s CHORISTER'S HAND-BOOK. Edited by JOSEPH WARREN. 1 vol. 4to., white cloth boards, price 8s. or in 52 Numbers, each 2d. "Valuable contribution to choral melody; contains no fewer than fifty-two anthems, arranged for two, three, or four voices (with piano or organ accompaniment), in a very effective style. The work is marvellously cheap, and should find a place in every parochial choir."--Tallis's _London Weekly Paper_, March 12. HAMILTON'S MODERN INSTRUCTIONS IN SINGING. Large music folio, 5s. ROBERT COCKS & CO. "One of the most useful of the many works which the Messrs. Cocks have published. We cordially recommend this volume; like the Author's 'Modern Instructions for the Pianoforte,' it will become one of the most popular works of the day."--_Scottish Press_, March 16.