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FEBRUARY 27, 1885. THE PHOTOGRAPHIC NEWS. 133 frame (D) is drawn out at the left side, the sitter is about A‘ and the camera on the line marked by dots. By varying the Place of the sitter, a large variety of effects of most beautiful lighting are produced. Here a grey reflector is wanted for the off-side. Those who have worked at figures near a window in a sitting-room, the spectator being in the darkened end of the room, and watching the play of light on a face, and the lovely gradations, and the immense variety at command, will know what I mean. I had often felt this in a room in my own house, and determined to make in my new studio such a window. The effects obtained are just what was wanted, and the alteration of the lighting is done in half a minute. Just double the exposure is required, but if you think this objectionable, or the plan [too troublesome, do not try it, for if you once begin to supply your sitters with pictures taken with this light, they will take care you are obliged to continue them. “ Another kind of shadow picture, requiring no more than the usual exposure, is taken, as shown on ground-plan No. 1. The dotted screen is shown in the centre, and the sitter at R, the camera at B K. During exposure the lens must be carefully shielded, being opposite the light. The pictures produced here admit of fuller faced shadow pictures, with the details of the darker side more decided than in the other system, and without the strange outline illumination. It is suited for the nez re- troutse and celestial, for round, plum-pudding faces, frequently giving them a grace and distinction of look that surprises none more than the possessor of the useful countenance aforesaid. “ To be able to make plain people look well in a picture, and to light up an ordinary face with animation, should be the aim of photography in good hands. Nothing does more to advance a man in the estimation of those who want pictures done than to see pictures of people they know who are shown to advantage in photographs. How can you do this, unless you possesss the means to do it by having the best possible lighting in your studio ? “In plan No. 1, as shown at A A, the sitter can be taken at either end of the room; the camera simply requires turning round. A very important point is, that in this studio there is no glare of light; thus fair complexions and blue eyes are ex ceedingly well given. It is rare to see in photographs the Saxon complexion adequately represented,” Heighuay's Miniature Studio.—Of the foregoing illus tration Mr. Heighway gives the following details:— “ A, B, C, D, represent the dimensions of the side light, five feet high by ten feet in length; A, B, G, II, being the entire side of the structure, including the three feet boarded up below the light. E, F, A, B, is the top light, having a ‘pitch ’ of thirty-five degrees. This is designed to permit of the rain readily running off. At certain seasons of the year, when the sun attains a high elevation, its rays may intrude through the top light, and to prevent this to a certain extent, the poles E, I, and F, J, are built, on which are fitted movable seats resembling Venetian blinds, under control from within the skylight. As a substitute, a canvas may be fitted with rings running on the poles, which canvas may be hoisted or let down at the pleasure from within by means of ropes.” 8 Bictionarg of Photography. BACKING OF PLATES. {See Halation). BACTERIA.—Certain bacteria—as, for instance, the putre faction bacteria—only move, according to Engelmann, in the presence of free oxygen. If these bacteria are under water in contact with plant cells containing chlorophyll, they will not move so long as they are in darkness and no oxygen is given off. On the other hand, as soon as light falls, the chlorophyll at once begins to generate oxygen, and the bacteria get into motion. Other bacteria there are, Engelmann tells us, called bacterium photometricum, which get into motion under no other circum stances but when light falls upon them. The animating power of the light is not instantaneous, but proceeds only after an inter val, so that a certain preliminary action is necessary, as in certain photographic processes; to wit, in the case of a mixture of chlorine and hydrogen, which combines under the action of light. The animating action of the light in this case is not due to any deve lopment of oxygen. Light in great quantity, and of a constant nature, acts as a sedative. On sudden darkening, the bacteria are frightened back. An illuminated ball introduced into the fluid impels the bacteria forwards, while a brightly-lit spot in an otherwise dark drop of liquid becomes a perfect trap to the little creatures ; they can get in, but they cannot get out. By directing a luminous ray into a liquid in this way, Engelmann has succeeded within a few minutes in bringing together within the space of 0-1 of a millimetre several thousand bacteria. The ultra-red rays seem to have the greatest power of animating bacteria in this way, although the tiny organisms are also sensitive to violet rays. As regards staining bacteria for photographing, Mr. Edgar Thurston says:— ‘ 1 As examples of bacteria occurring in a free state, or in fluids, I may take, from among many, the various coloured species of which colonies grow on the surface of eggs, meat, bread or potatoes ; the putrefactive bacteria in decaying meat or vegetable infusions ; the sputum from the lungs of a pneumonic or tuber culous person ; or the blood of an animal suffering from splenic fever. “ To stain such bacteria the following mode of procedure will be found the best:—Place a minute portion of the bacterial fluid, or of a bacterial colony, by means of a previously heated platinum needle, on the centre of two cover-glasses (004-005), and, laying one cover-glass over the other, squeeze them gently together between the fingers, so that the bacteria are diffused over their surfaces in a uniform layer. Then slip them apart and leave them to dry. After a few minutes, pass the cover-glasses rapidly through the flame of a spirit lamp, so as to fix the bacteria on the glass. Cover-glasses so charged may be kept for an indefinite time ; and if an interesting growth of bacteria is met with it is always well to reserve some specimens in this way for future reference. “ Bacteria of which micro-photographs are to be taken must be stained with a red or brown dye, and by far the best medium is a saturated watery solution of vesuvine or Bismarck brown, which should be filtered before use. It is always best to use a freshly-made solution. " The cover-glass, with the bacterial surface downwards, should be floated on the top of the solution, and allowed to remain there for approximately an hour, though experience will show that the time required will vary according to the specimen of dye which is
