A Manual Of Photography

98 GRIFFIN’S SCIENTIFIC CIRCULAR. [March, As the Articles in this Catalogue commence with No. 2683, it is necessary to mention, that the Articles Nos. 1 to 2682 are contained in our General Descrip- tive Catalogue of Chemical and Philosophical Apparatus, the last edition or which, including the first Six Parts of the Scientific Circular, was published in December, 1851, in octavo, illustrated by 1200 woodcuts, price 2s., or post tiee, 2s.6d. PHOTOGRAPHIC APPARATUS. The Cameras No. 2689, 2691, 2695, are intended for taking views landscapes, copying pictures, and other inanimate objects, the lens with which each is fitted being mounted so that a portion of the external rays is cut off by a stop placed in front of the lens This corrects the aberration of the rays of light passing through those partsi of ’the lens nearest the edge. This stop gives a degree of sharpness to the pictures which cannot e produced by the double combination of lenses, and hence its general adoption for taking inanimate objects. For portraits taken from life, however, where rapidity of action is a «■reat desideratum, the single lens is nearly useless; as the amount of light admitted by the stop is so limited that a long time is required to take a portrait, and it ^LeuNt keep a sitter in the same position for the necessary period. Consequently, if a Camera for portraits is required, it is necessary to select it from Nos. 2690, 2692, or 2696, or if a Camera for both portraits and views is required, then the choice must be made from Nos 2690 2692, or 2696; but in the latter case, the double combination of lenses must be altered for views as follows :-The posterior cell, or that nearest the ground-glass plate of the Camera containing two lenses must be removed from the mounting, and the anter cell må be unscrewed from the mounting, and have the lens taken out of its cell and reversed so that its plane side shall be placed nearest the object that is to be copied. A tube containing a Diaphragm with three stops,No. 2706, must now be put over the mounting in the same position as that occupied by the brass cap of the double combination, and one of the stops must be brought into action. The use of the diaphragm is easily udersol from inspection, but which of the three stops is best adapted for an object intended to be taken, is more difficult to determine. It may be given as a general i ule that the smallest stop is to be used for pictures to be taken from objects m sunshme-the next during suiishine if the object is in the shade, and the largest when the light is limited. When for the above, or any other purpose, the lenses have been removed from thei cells it is essential that they be replaced in their original position, and that the sides be not reversed As a guide, we may mention that, in the double combination of lenses, Nos 2703 2704 and 2705, the least convex side of the posterior lens (or that which passes into’the Camera), the concave side of the second lens, and the plane side of the anterior lens, must be all turned towards the ground-glass plate of the Camera, as must also the convex side of the single achromatic lens, Nos. 26.18 2700, or 2/0^ The Camera and Lenses of the Sets of Apparatus for Calotype Processes, Nos. 2683 and 2684 are also adapted for taking pictures on silver, but for that purpose the articles ÏÂ à description J the Camera in the set The same remark applies to the Daguerreotype sets, Nos. 2686, 2687, and 2688, which can be used for the Calotype and Collodion Processes, when the articles enumerated after the Camera in the set No. 2683 are added. SETS OF CALOTYPE APPARATUS. 2683. Complete Set of Apparatus for the Calotype and Collodion Pro- cesses, for taking pictures measuring 7 inches by 6 inches, including a Camera, No. 2691, with achromatic lens, 2| inches diameter mounted in brass with rack and pinion adjustment (No. 2700), focusing glass, and frame for the sensitive paper ; shallow porcelain dish for pre- paring the sensitive paper, and fixing the picture ; two camel s-han brushes ; one quire photographic paper; one quire blotting paper ; pressuie frame for producing positive pictures ; oil lamp, with yellow glass shade ; balance, with a set of weights, and two glass capsules to contain the substance to be weighed ; glass measure, and the following chemicals in stoppered bottles : acetic acid, gallic acid, ammonia, iodide of petas-