A Manual Of Photography

270 PRACTICE OF PHOTOGRAPHY. and dissolved in 20 grains of alcohol by means of an alkaline iodide. M. Adolphe Martin prefers iodide of ammonium. The plate is next plunged into a hath of 1part distilled vater, 1^th nitrate of silver, and 1^th nitric acid. The image is deve- loped by proto-sulphate of iron, and he effects the change from negative to positive by a batli of double cyanide of silver and potash consisting of about 2 quarts of water, in which are dissolved 375 grains of cyanide of potassium, and 60 grains of nitrate of silver. The pictures thus produced are remarkable for their intense whiteness. , ..„ We must allow Mr. Archer to give his own description of a very ingeniously constructed camera, which he has devised for working out of doors. Description of tlie Camera for tlie Collodion. I will proceed to nive a general description of the camera I have constructed, premising that it admits of being made as a very light folding camera, if thought necessary.. “ It is a wooden box, 18 inches long, 12 inches wide, and 12 inches deep, and is capable of taking a picture 10 inches square. Externally it may be thus described:—In front it has a shding door, with a circular opening in it, to admit the lens: this sliding door enables the operator to lower, or raise, the lens, and consequently the image formed by it, on the ground glass, as the view may require. The two sides of the camera have openings cut in^them, into which sleeves of India rubber cloth are fixed to admit the hands of the operator ; and are furnished with India rubber bands at the lower ends, which press against the wrists, and prevent the admission of light. “ The back of the camera has a hinged door fitted at its upper part with an opening of just sufficient size for the eyes, and shaped so as to fit close to the face. A black cloth is tied round this end of the camera, to prevent any ray of light penetrating at this opening. In the top of the camera near the front is inserted a piece of yellow glass, to admit a small quantity of yellow light, and is closed with a hinged door, to regulate the quantity of light required. “The interior of the box is furnished with a sliding frame, to support the ground glass or the bath and the prepared plate ; and it has a stop, by means of which any focus from 3 inches to 15 inches can easily be obtained. “ The bottom of the camera is furnished with a gutta percha tray, about 1 inch deep, to hold the washings, Le., when the camera is in operation. “ Also, the bottom of the camera at the back has an opening