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2 THE PHOTOGRAPHIC NEWS. [January 2, 1891. The powerful influence of developing at different distances from the lamp may be illustrated by fig. 2, a cut which we used for another purpose in the Year-Book, and which cut is reproduced from the standard work on “Chemistry,” written by the late Professor W. Allen Miller. Let the candle in this cut represent the source of light, and 2 repre sent a sensitive plate one foot square, placed at two feet from the flame ; now move the vertical plate to a distance of six feet, and it will be seen that it receives one-ninth the previous amount of light, so that the chance of fogging is greatly reduced by working with the plate at that distance. By careful attention to such principles as these, it is possible to develop plates without fog, by the aid of a naked candle, without any dark room lamp at all, a plan which, if our memory be not at fault, was first published by Captain Abney; at all events, we read it somewhere, and have on rare occasions employed the method in the bedrooms of mountain hotels, with the actual plates of the late Dr. Van Monckhoven, which were slow. The plan is to put a candle down on the floor in one corner of a large bedroom, and to hang a towel over a clothes-horse placed imme diately in front of the light; then go to the farther corner of the bedroom, and with the back to the lighted corner, and the developing dish immediately in front of the body, take out the plate, and pour on the developing solution, preferably a yellow one or one which quickly turns yellow. This will bring out the image, and by care not to infringe various principles herein laid down, an unfogged image can be brought out, and then washed and fixed. In this instance the candle illuminates its own corner of the room and the ceiling close to that corner, whence some is reflected to the opposite corner, but not to the plate, because of the interposition of the body of the operator; next some of the residual light is reflected to the developing dish. In telegraphy certain excellent instruments cannot be used, because their working needs intelligent know ledge of electricity on the part of the operator, who is thus made virtually a part of the apparatus; such a worker, however, can command more salary, hence it in some cases is more profitable to use an inferior machine, worked by a less educated man, such, per haps, as a railway policeman, who is usually helpless directly the instrument gets out of order; he cannot put it right. So is it in developing. The brightest light can only be used constantly with safety when the intelligence of the operator virtually forms a part of the developing room lantern. Another influence should be borne in mind in deve loping room work. The plate is much safer than before when covered by the developer, even when the developer itself is colourless, for the surface of liquid reflects a portion of the light which falls upon it, and that reflected light cannot reach the plate. Of every 100 rays of light falling at an angle of 50 degrees, water reflects 72, glass 54, marble 60, mercury and speculum metal 70. Dark coloured substances reflect little light. At a small or grazing angle, much light is reflected, so much so that even a sheet of white paper can be made to act as a mirror. If a sheet of white paper be held horizontally between the eye and a candle-flame, and almost at the level of the eye, the observer will see an image of the flame reflected by the paper. When the total effect of all the influences mentioned is considered, it becomes evident what a vast gain in safety there is by developing at the position EF, fig. 1, instead of at the position BD. That any plate should be developed at one particular distance from the lantern to get the best results with the maximum of light, is neither necessary nor desir able. The operator can have illumination enough to comfortably take a very sensitive plate out of the slide at a distance of six or ten feet from the lantern, to put it in the developing dish, and to cover it with the solu tion, after which, in accordance with the principles just enunciated, it will bear moving much nearer to a bright yellow light than would otherwise have been the case. As development goes on, it will bear bring ing still nearer to a bright light, and towards the close —in those instances in which the plate has been under exposed—it is actually advantageous to open the coloured window of the lantern, and to allow the white light from the flame to shine upon the plate in the developer. This may produce a slight veil, but it will bring up some detail which otherwise would have been lost, as Mr. Cowan has recently proved by sensi tometer experiments, and in practical photography it is scarcely possible to have a safer guide than Mr. Alex ander Co wan, who is the manager of the works of Messrs. Marion and Co. at Southgate. It is well for a photo grapher to get into the regular habit of taking the plate out of the slide, and covering it with the developer at a good distance from the lantern. As to the advantages set forth in the last YEAR-BooK, of yellow over red light in the developing room, when orthochromatic plates are not employed, Mr. Deben- ham deserves the thanks of photographers for his letter in another column for the correction of an historical error as to the date and origin of the first publication of the explanation of the cardinal mistake about the proper colour of the light to use with gelatine plates, which had previously existed in all text-books. We were not aware of the existence of that paragraph when drawing attention to an article from another source, in which diagrammatic and tabular evidence was given of the truth of the principle enunciated. Since then, more accurate measurements than Fraunhofer’s of the rela tive luminous intensities of the different parts of the spectrum have become available; for instance, the following more modern table on the subject has been