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DEOEMBEE 17, 1880.] THE PHOTOGRAPHIC NEWS. 607 the combining proportions have been properly worked out, and having the bromide or bromo-iodide salts in ex cess. In order to frame trustworthy formulae, some chemi- cal knowledge is required ; but where such knowledge is wanting, and where original experiment might only fog the operator and his plates, there is a store of published formulae available for all. The next condition of success is to make a proper use of the formula when once decided upon. There need be no difficulty in procuring pure chemicals. The greatest stumbling block is gelatine. “ Coignet’s ” is excellent. It is safe not to cause fog or frilling, and it is equally sure to break out in the “ zymotic,” or chronic disease whose virus appears as “ opaque spots ”—a trouble about which we may have something to say on a future occasion. During winter, and, under proper treatment, even in summer, Nelson’s photographic gelatine answers admirably. Its fitness, however, depends, to some extent, on the con dition of the salts employed. When the emulsion has been mixed, it should show acid reaction. It should slightly redden litmus paper. Where the reaction is alka line, there is danger of developing fog by boiling. One ortwo minims of dilute aceticacid has proved advantageous in our experience when dealing with neutral solutions. The acid should just be sufficient to bring a blush to litmus paper. Alcohol in the proportion of one drachm to five ounces of emulsion is also useful as an antiseptic. Another condition to be observed in boiling is keeping at least three-fourths of the gelatine in reserve. This confers a two-fold advantage. Excess of gelatine retards the digestion of the bromide of silver. It yields a finely-grained emulsion, but not so sensitive as when the minimum of gelatine has been used. Again, it is under stood that " boiling ” gelatine for any length of time tends to diminish its power of setting. The residue of fresh material is therefore needed to replace the lost power. We have said that half an hour’s boiling is unnecessary as well as dangerous. It is safer to shorten the time, and supplement digestion by following Dr. Eder’s plan of adding ammonia to the emulsion after boiling. The whole of the gelatine should be first added, and the emulsion kept at about 90° F. for (say) two hours, after which it may be chilled, and washed in the usual way. Emulsion thus treated with ammonia adheres well to the plate, and proved, in our hands, extremely sensitive, yielding full and delicate negatives. We have touched upon some of the conditions of success, but the process is hedged round with a host of small troubles which can only be overcome by patience and experience. It is impossible to suggest remedies for all phases of failure. We can only offer a helping hand to our fellow workers in the new field. Zlotes Mr. W. J. Wilson, of Hammersmith, is a fortunate man. To him has been awarded the £50 Paget prize in the dry-plate competition, the jury.deeming the process a good one, if not of Surpassing excellence. In any case, it is a splendid prize, if it is not a splendid process. John Chinaman is to the fore in photography. In the Hue Quatre Septembre, in Paris, a native of the Flowery Land will sell you camera, lens, and stand complete for twenty-four francs. The stand which we had in our hands on Tuesday night—Mr. Whaite was good enough to show it us—was a bamboo, enclosing two hollow tubes of steel, which, put together, form a tripod. The camera is fashioned for the most part of silk, and the lens—well, the lens is less good than the rest. Mr. George Tuohy, of Richmond, has been taking his camera into the ball-room ; and some pictures which are very interesting from several points of view are the result. We do not mean to say that this adventurous operator secured drop-shutter photographs of dancers in motion ; he evidently just told the guests to step towards yonder end of the room, and then exposed to the extent of 10 or 15 seconds. Certain cross shadows, which don’t quite agree with the gas chandeliers, make us think of white fire, or some such composition, being burnt low down on each side of the camera. White fire, or no white fire, the results are extremely interesting, and prove the practicability of securing pic tures of certain phases of life and character to which the camera has not hitherto been commonly directed. Some of the figures and groups in Mr. Tuohy’s pictures might be of considerable value to an artist. A very young man and his partner standing towards the right hand side of one of the pictures form about the finest representation of ex treme “ spoondom ” which we remember to have seen — quite an artistic study. Follow up this line of work, Mr. Tuohy, and let us see the results of your future efforts! Mr. Henderson has made a most interesting experiment —indeed, it bids fair to turn out something far more valu able than an experiment—in connection with the production of .extraordinarily rapid emulsion. He has found that if phosphorescent sulphide of calcium in a fine state of division is mixed with bromide emulsion, the sensitiveness of the latter is highly exalted. Mr. Henderson triturates the sulphide in a mortar, adds a little glycerine for convenience sake, and then gradu ally mixes the same with his emulsion. The difficulty naturally is to keep this prepared emulsion from the action of light, for coloured rays of all kinds seem to act upon the calcium, and this, once phosphorescent, sets up an action upon the bromide in the emulsion. Mr. Henderson does not profess to have satisfactorily solved this last problem, but freely makes public the fact, so that those who wish, may work upon it. The number of reducing agents that have been suggested since the birth of photography as suitable for developers is rather numerous, although those of established worth are indeed few. An infusion of nutgalls, which paved the way to pyrogallic development, was, as all the world knows, suggested by Reade in 1839. The use of proto sulphate of iron is due to a suggestion of Hunt in 1811, the possibility of employing ferrous oxalate being also men tioned by him in the same year. The employment of per sulphate and ammonio-citrate of iron in photography was, however, made public by Herschel in 1810. The deve lopment of the bitumen image—Nicephore Niepce’s first process—by means of essential oil of lavender, dates from 1814.
