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May 28, 1880.1 THE PHOTOGRAPHIC NEWS. 263 spectroscope reveals the fact that the “ canary medium ” in question intercepts only the violet and blue rays, our faith is not strong enough to believe that the green rays (which are freely admitted through it) would be harmless —indeed, they are not so upon our plates, whatever they may be upon others. Thanking you for the courtesy of publishing our letters, we are, sir, yours faithfully, D. H. Cussons and Co. MODIFYING THE OXALATE DEVELOPER. Dear Sir,—Further experience with the ferrous oxalate, according to Dr. Eder’s formula, shows that there are several means of modifying the action of this developer on the exposed plate. The addition of methylated spirit, in the proportion of about one-fourth of the whole, seems to pre serve and accentuate the vigor of the solution in a remark able degree. I had occasion last week to develop about seventy-five 10 by 8 plates exposed by Mr. Vander- weyde with the electric light, on tableau vivant groups at Kensington, when with this alcoholic addition about 40 oz. of solution sufficed for the whole, the energy being little impaired at the end. Again, glycerine has as bene ficial an effect as with the pyrogallic, conserving the clear parts of the pictures in a remarkable manner. Both glycerine and bromide, and in a remarkable degree the two combined, seem to give a valuable control over the development, and enable one to counteract the ill-effects of over-exposure. In fact, further experience leads me to the belief that the controlling power is nearly as com plete as with pyrogallic. Some remark on a certain opalescence of the film, which seems to impair the brilliance, but this is simply in the gelatine, and gives way under the varnish. Two great points of advantage stand clearly forth in favour of this system—first, that intensifying is rarely needed, and when required is got without difficulty or fear of having an evanescent image ; and secondly, that the image is similar in appearance to wet collodion, consequently of a colour the printing value of which can be perfectly estimated. This I look upon as a most important point, and removing about the last objection to dry plates, for it cannot be denied that a serious difficulty has existed in the liability to get these yellow pictures.—Faithfully yours, Samuel Fry. PAYMENT OF ASSISTANTS. Sir,—For the past five weeks this question has been before your readers. I am sorry that the “ Operator of Six Years’ Standing ” did not put the question in some other way for the good of his reputation. I would not quite dishearten him, but, nevertheless, six years is too short a time for him to call himself an operator or assistant operator, as we all know that employers expect such to understand not only the taking of good negatives, but to thoroughly understand lighting and posing, and be well up in manipulation. I, for one, would advise him to look well into the subject before taking an engagement as an assistant operator. As regards payment as operator, I can endorse your correspondent “H. B.’s” statement; and, I think, had your former correspondents, “ Beau Nash ” and “ J. Kay,” given some practical advice in answer to the so-called operator, it would have been more to the point.—Faith fully yours, W. J. Aroceebings of Sucieties. Photographic Society of Ireland. A MBETING was held in the Royal College of Science, on Friday, May 14th, Mr. J. V. Robinson in the chair. The previous minutes having been confirmed, Mr. Conan exhibited and described a drying box for gelatine plates, which he had recently completed, also a drop shutter for rapid exposures. Mr. Thomas Mayne showed a number of lantern trans- parencies on gelatine plates, which were variously developed, and explained the different methods by which he had endea voured to get rid of the usual veiled appearance, and which was found to be altogether obviated by cementing the pro tecting glass to the positive with Canada balsam. Some good specimens ef mechanical printing were ex hibited and described by the Chairman, and which were in their line considered worthy of every admiration. The Secretary drew attention to the fact that the informa tion on the photographic power of phosphorescence, lately brought before the Photographic Society of Great Britain, at their meeting on the 11th inst., had already been communi cated to the Society by Mr. J. V. Robinson at the meeting of the 13th February last, a report of which was published in the journals of the 27th of the same month. This being the concluding meeting of the session, it was announced that the next meeting would not be held until October. The presentation print for the year was then distributed to the members present, after which the proceedings terminated. Bolton Photographic Society. The ordinary monthly meeting was held at the Baths, on the 6th inst., Mr. Thos. Parkinson in the chair. After the minutes of the previous meeting had been read and confirmed, a series of out-door meetings, to be held fort nightly, were arranged for the summer months, —the first to be at Worsley Hall, on the 29th inst. A number of instantaneous views were exhibited by Messrs. Harwood, Shipperbottom, and Grundy, of the opening ot theNew Infirmary on the 1st inst., and Mr. Shipperbottom also ex hibited an instantaneous shutter. A monthly meeting of the Council having been arranged, the proceedings were brought to a close about 9p.m. Photographic Society of Vienna. Thb following is the list of prizes which the Photographic Society of Vienna offer for competition in the course of the pre sent sessional year:— Voightlander Medals. (Open to Members of the Society only.) 1 .—A gold medal, value 140 ducats, for a method of increas ing the sensitiveness of wet plates. 2 .—A gold medal, value 140 ducats, for the most reliable and sensitive dry process. 3 .—A gold medal, value 50 ducats, for researches into the gelatine emulsion process. 4 .—Medals in gold, value from 40 to 100 ducats, in silver and in bronze, for scientific treatises, discoveries and improve ments which have been published in the official journal of the Society (the Photographische Correspondent). 5 .—Medals in silver and bronze for the achievement of valu able results in the practice of photography. Society Medals. (Open to Members or Non-Members.) 1 .—A gold medal, value 140 ducats, for the production of plates in relief for printing copies of drawings in half-tint. 2 .—A gold medal, value 140 ducats, formonograph on pyroxy- Jine and collodion. 3 .—A gold medal, value 140 ducats, for an improvement of the collotype process which will render unnecessary the constant wetting of the plate between the pulls. 4 .—A gold medal, value 50 ducats, for a vigorous investiga tion of the conditions of sensitiveness of asphalte. Further particulars of the competition are contained in a detached programme, which, together with the prospectus and rules of the Society, will be forwarded post paid on application to Dr. E. Hornig, 9, Hauptstrasse, Vienna III., to whom also should be addressed applications for admission to member ship. Ualk in the Studio. South London PhoTOGRAPMIC Society.—The last meeting of the present session will be held on Thursday next, June 3rd, at 8 p.m., in the rooms of the Society of Arte, Adelphi. Mr, J. 8. Hazard will read a paper on “ Gelatine or Collodion—which pays best ? ” and other matter of interest will be brought befora the members.