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July 6, 1883.] THE PHOTOGRAPHIC NEWS. 425 have the question brought up again in connection with gelatine plates, and in the month of June, when over sensitiveness, rather than the want, is to be expected. A German engineer, Herr Schumann, has obtained some results interesting to photographers, with a newly con structed photo-spectroscopic apparatus. The prisms of the instrument are fashioned of rock-crystal and calcareous spar, and with these he has examined the action of light upon bromo-iodide of silver. Herr Schumann has found that in certain circumstances bromo-iodide of silver possesses a greater sensitiveness for colour than pure bromide of silver, and he asserts also that the two maxima of sensitiveness discovered by Abney disappear altogether when the mixed iodide and bromide of silver is subjected to digestion. Schumann is undertaking further experiments in the same direction. Auctioneers and estate agents might make a much more extensive use of photography than at present; still, they are beginning to appreciate the advantages of a very obvious means of placing reliable details before intending purchasers. Only a couple of days ago we saw the con ditions of sale of the Weybread Lodge Estate, in Suffolk, and a well-executed cabinet photograph was mounted on a place left for the purpose by the printer. A very perfect electric lighting system has been fitted up at the new Parkeston Quay Station, and Hotel of the Great Eastern Company ; arc lights are driven direct from the dynamos, while Swan’s incandescent lamps are actuated by secondary batteries which have been charged during the day time. At the time of our visit on Saturday afternoon last, the engines were still, the attendant telling us that he had run the machine for four hours that day, and stored up a sufficient charge to keep 250 Swan lamps in action for more than seven hours. As he lighted up the station and hotel by turning on a few switches, he remarked, “ I have only 39 cells of the battery in circuit now, but after three or four hours working I shall add a few more; but I do not often find it necessary to use the full set of 55.” A good deal depends upon Mr. Justice Field’s judgment in the case of Nottage v. J. H. Jackson, one of the points being of especial interest to photographers. We mean the question as to whom belongs the copyright of a portrait negative if an assistant takes it unaided in any way by the principal. The Copyright Act, it is argued, contemplates a personal authorship, for the copyright is to continue in force for a certain time after the author’s death. Although the Judge decided for the defendant, it is a matter con cerning which much may be said on both sides. The Photographic Society is bent upon following the example of the French Society in having occasional lantern demonstrations at the annual Pall Mall Exhibition. As we have witnessed the lantern demonstrations in Paris, it may be well to mention how they are managed. An announcement is put up in the exhibition gallery of the times when pictures in the lantern will be shown, and the display does not take place in the gallery itself, but in a special apartment darkened for the purpose. Thus the entertainment can be given just as well by day as by night, and does not interfere with the enjoyment of other visitors who may prefer to occupy themselves in the gallery. In Paris, the lantern display lasted a brief half-hour—the brevity of the period was a great element of success—and considerable tact was shown in the selection of good subjects and good slides. Personally, we were well pleased with the Paris lantern entertainment; but, at the same time, there is no denying the fact that, unless the affair is managed well, it may easily descend to a mediocre level. Moreover, a lantern display—unless conducted on a really grand scale—should not be permitted to interfere with the main object of the Exhibition, which is to allow the public to seethe pictures on the walls. By making it a mere aljunct, success would possibly attend it; but it must only be as an adjunct, and nothing more. At the Physical Society, which meets within the charmed circle of South Kensington, there is a growing tendency towards an almost fastidious exactness of verbal expression. Hence, when Professor Hughes referred to Ampere’s theory of magnetism as a “higgledy-piggledy” arrangement, no less than five members rose to their feet, and, in the most ingenuous manner, enquired the meaning of the expression. Still, it is scarcely worth while for us to reproduce Professor Guthrie’s fine distinction between “ higgledy ” and “ piggledy.” “ When you buy patent plate, be sure that you get it.” The advice is very good ; but those who purchase this expensive article, whether for enlarging, copying, collo type, or other special work, are often not in a position to judge until it is too late. Therefore, the ready test in general use in the trade for telling a piece of patent plate from ordinary glass, may well be borne in mind. Hold the glass plate in your hand, and look down upon it at any reflection of straight lines—the lines of a studio roof is a capital test. The lines should appear reflected on the glass surface as straight as they are in reality; if the markings are wave-like, then the glass is not patent plate. Herr Ernst Wolfram, in the Zeitung, advocates the em ployment of metallic lead for retouching instead of graphite. A lead point presents several advantages, he says, among them being that the retouching may be done more quickly, while the pencil does not crumble nor break off. Again, there are no dust particles, as in graphite, to rub away, and therefore the retouching work upon the negative is more permanent. Some preparation of the film is, however, necessary before retouching with metallic lead, such as coating the negative with hard varnish, and rubbing the surfaces to be retouched to render them matt.