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366 THE PHOTOGRAPHIC NEWS. [July 30, 1880. , Ule 2 gotograygir Sebs. Vol. XXIV. No. 1143.-JULY 30, 1880. 365 366 366 367 368 369 370 371 372 372 372 CONTENTS. PAGE Photography In and Out of the Studio 361 Prints from Old Negatives. By the Author of “Looking Back” 361 At H me 362 A Simple Shutter for Extra Rapid Photography. By J. Vincent Elsden 364 Substitution of the Glass Support by Flexible ones, Paper, Clo*h, &c. By J. Ferron and I. Paul New Emulsions Photographs of Motion Notes Tonics of the Day “ Never too Late to Mend.* ’ By J. E. Walker Correspondence Proceedings of Societies Talk in the Studio To Correspondents Patents. Compiled by Des Voeux and Colton NEW EMULSIONS. Complaints are just now rife as to the troublesome behaviour of gelatine emulsion. It easily decomposes in warm •weather, sets with difficulty, dries very slowly, and not unfrequently becomes totally useless. In a word, satis factory as gelatine films may be, all who work with them hope for something better, and from many sides comes the advice to render the gelatine soluble in alcohol and thus quicken the drying of the emulsion, or to return once more to collodion emulsion. Unfortunately, all endeavours to produce an alcoholic gelatine emulsion have been so far without any practical success, and, as everybody knows, we cannot impart to collodion emulsion any high degree of sensitiveness. But Professor Vogel’s new emulsion, from our short experience of it, appears to get over many of the defects which the summer weather has made so apparent. To all appearance, it is a happy and ingenious combination of gelatine and collodion emulsion, the solvent being, so far as a superficial examination can show, alcohol and acetic acid. The emulsion is at an ordinary temperature semi-fluid, and only becomes limpid when dipped into warm water. It is poured exactly like collodion upon a plate previously pre pared with india-rubber solution or a thin coating of gela tine and chrome-alum. The superfluous emulsion is readily drained oft like collodion, and the film in our hands set in afew minutes. Putaway in a perpendicular position, theplate dried within an hour. There is no necessity, therefore, for any levelling apparatus, and as the emulsion pours after the manner of oil, it is easily manipulated. The sensitiveness of Dr. Vogel’s emulsion we found to be about three-fifths that of a good commercial gelatine plate, so that in this respect the new compound may be considered satisfactory. We found both pyrogallic and ferrous oxalate development suitable. The picture appears slowly, but very rich in detail, and, unlike the ordinary run of gelatine plates, the result inclines to softness rather than hardness. The emul sion possesses the great advantage, we found, that it could be treated with a silver intensifier without showing any disposition to exhibit that detestable red fog. In other respects, we may say that its colour is a deep yellow; the film is matt, and, like collodion, is injured by contact with water when in a moist state. A dry film, however, is no more damaged by moisture than a gelatine plate. Another new emulsion is one which also comes to us from Germany, and which Dr. Wolfram has patented. To pre pare his emulsion he dissolves two grammes of pyroxyline in 150 cubic cents, of a mixture of alcohol and ether ; to one- half ot this collodion he adds a solution of from 4 to 16 grammes of nitrate of silver dissolved in from 25 to 80 cub. cents, of concentrated ammonia which has been diluted with an equal volume of alcohol. Into the second half of collo dion he puts an equivalent quantity of bromide of sodium or ammonium which has previously been dissolved in 10 or 20 cub. cents, of water. The bromide is mixed with the silver nitrate, aud the resulting emulsion is precipitated with water. With the emulsion is mixed, when re-dissolved, two per cent, of glycerine, and eventually a sensitizer is also added. The principle of the method is good, for ammonia, as our readers may know, acts upon collodion emulsion in the same way as upon gelatine. The emulsion is thereby rendered more sensitive, although not to so exalted a degree as gelatine emulsion, if collodion alone is present. At the same time Dr. Wolfram seems to us to employ rather too much ammonia, and he must find it difficult to avoid fog; a sample prepared by the patentee himself certainly gave us fogged negatives. Dr. Wolfram’s method of preparing collodion emulsion with ammonia may nevertheless have its advantages if a good sensitizer is employed : in the meantime, however, we have to report very favourably upon Dr. Vogel’s compound, of which our readers may expect to hear more shortly. PHOTOGRAPHS OF MOTION. Our Paris correspondent, M. Leon Vidal, recently des cribed in these columns an instrument termed a praxino- scope, and devised by a M. Regnaud, which is an. improvement upon our old acquaintance, the zootrope A number of pictures are shown in succession, representing men or animals in the act of leaping and running, and they pass before the retina so quickly as to create the illusion that the men or animals themselves are in motion. In M. Regnaud's instrument the figures are enlarged and shown upon a screen, so that there is less difficulty about seeing them than in the ordinary zootrope. A combination of this instrument with photography is contemplated, and M. Vidal very truly remarks that, inasmuch as Mr. Muy bridge has successfully photographed an acrobat in the act of turning a somersault in a series of fourteen views, there should be no difficulty in applying such pictures to the in strument, and rendering it, in this and other ways, of use for study and instruction. Our readers may not be aware that the late Sir Charles Wheatstone, shortly before his death, was engaged upon work of this character. Nothing was too small to engage Wheatstone’s attention, and if an idea seemed likely to bear fruit, he did not wait to consider to what use it was likely to be put. If the result of his labours proved of no value as a practical instrument for every-day use, he was not ill-satisfied if he could turn it into a scientific toy. Several of these owe their origin to Wheatstone, and it is a question whether, in their elaboration, he did not prove himself a greater teacher than many a learned professor in class-room or college, since he imbued the youthful mind with a love for science that was generally lasting. That he prided himself quite as much in the elaboration of a scientific toy as in a grave improvement of the electric telegraph is no secret, just the same as another great man devoted to photography—Sir David Brewster—occupied himself as willingly with problems of natural magic as with the most abstruse question of optics. We werepriviliged to assist Wheatstone in the experi ments to which we have alluded. It was his idea to depict a steam engine in motion, by the aid of a series of photo graphs, and an instrument of his own construction, which, by an intermittent motion, brought the pictures into view one after another. Wheatstone stipulated for a series of thirteen pict ures, and to secure these he proceeded as followsA steam engine suitable for a model was chosen, and a site selected for the camera, whence fly-wheel, governor, aud piston could be well seen, since these re quired to be the most prominent. The engine, we may premise, was not at work; it had, indeed, to be suitably treated with paint and violet powder to render it a favour able sitter. The circumference of the fly-wheel was accu rately measured, and divided into thirteen (for that was