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720 THE PHOTOGRAPHIC NEWS. [NOvEMBER 6, 1885. J. R. Sawyer will read a paper on his new method of “ Photographic Engraving,” accompanied by a demonstration of the processes by which the auto-gravure plates are produced. Photographic Instruction at the Polytechnic.—Mr. E. Howard Farmer’s winter course of Tuesday evening lectures on photography begins in earnest next week. The introductory lecture was given last Tuesday, and was well attended. To those •—especially the young—who wish to acquire an intelligent know ledge of the principles on which our art is based, we cannot give better advice than to take a systematic course of instruction. Such a systematic course is that through which Mr. Farmer takes his hearers, and the soundness of his teaching is attested by the brilliant success of the Polytechnic students at the May exami nations. Royal Institution op Great Britain.—At the general monthly meeting held on Monday, November 2nd, Warren de la Rue, Esq., M.A., D.C.L, F.R.S., Manager, in the chair, Joseph Wilson Swan, Mrs. J. W. Swan, and General J. F. Tennant, R.E., F.R.S., were elected members. Abstract op Chairman Jones’s Lecture at the Birkbeck Institute, November 4th.—Most of the elements combine directly with oxygen ; but chlorine, bromine, iodine, gold, silver, and platinum form oxides by indirect means only. The oxides of non-metals are generally acids, while the oxides of metals are alkaline, or are analogous to the alkalies. When an acid oxide and an alkaline oxide combine, there results a “ salt,” and some such salts have still an alkaline nature, as carbonate of potash, while others retain an acid character. Hydrogen is by far the lightest and most agile substance known; a leakage in a gas bag that allows an unimportant quantity of oxygen or air to escape may let out a dangerous amount of hydrogen or coal gas, for this latter is by volumeabout half hydrogen. Water is the cause of colour in some cases ; blue vitriol, is white when thoroughly dried. Pure water is not practically attainable, though in all cases a certain degree of purity is essential. The necessary purity varies according to the purpose for which it is to be used. Removing Silver Stains.—Dr. H. W. Vogel, in the Thoto- qraphische JUittheihmgen, recommends, for removing silver stains from the hands, the same compound that has been used as a reducer, i.e. a mixture of ferricyanide of potassium and hypo sulphite of soda. A few crystals of the former substance are dissolved in a solution of hypo, or from 10 to 20 per cent, of a 20 per cent, solution of the ferricyanide may be added to the hypo solution, and applied to the stains. Dr. Vogel points out the advantages of this substance over cyanide of potassium; it is not poisonous, and does not destroy the colour of articles of clothing. Photographic Action on Ebonite.—At the back of one of the cases of lecture apparatus, facing a north window in this laboratory, there happens to have been standing for six months or more, an ebonite plate with a framed glass plate in front of it, the glass having a star-pattern, done in little spots of tin-foil all over it. The thickness of the frame, say an eighth of an inch, separated the two plates from each other. On taking them out of the case the other day I noticed the pattern on the glass clearly and sharply imprinted on the ebonite, every little circle well marked. Dust had been plentifully deposited on all parts not screened by the tin-foil spots, and the striking clearness of the impression was mainly due to this local absence of dust ; but even on wiping off some of the dust the pattern could still be detected, owing to some difference of surface between the exposed and the shaded portions.—E. E. Robinson, in Nature. Photographic Club.—The subject for discussion on Novem ber 11th will be on “ The Reversed Action of Light.” Uo Uorrespondents. *,* We cannot undertake to return rejected communications. E. S. Lauder.—Cases have been known of sore places upon the arms and hands attributed to absorption of pyro into the system. There appears to be a great difference in the suscepti bility to poisoning by the skin in different individuals. This is considered to be established in the case of bichromate poisoning, which has sometimes occurred with carbon printers. It is obviously desirable not to allow pyro solution to act upon any portion of the skin that has been abraded. E.—You can secure the copyright of your photograph at Stationers’ Hall ; but that will not affect any copyright or want of copyright in the object from which your photograph is made. F. C.—The prints are examples of imperfect fixation. If a petroleum tub was used for washing the prints previous to toning, a little of the liquid, coming in contact with the paper, would protect the silver compound from the action of the hypo, and so cause the effect seen in the print sent us. A. D. H.—The shutter you have used is not quite quick enough for instantaneous work. There are several in the market which act much more rapidly, but we cannot make invidious dis tinctions between them. The same applies to your question as to whose plates to select for the work. Consult our adver tising columns. The result you send us is very promising, although not quite up to the mark for rapidity of exposure. Fred Turner.—We are afraid that you will not succeed in entirely removing the red silver stain from your unvarnished gelatine negative. Cyanide of potassium solution might do something for it. Night Photo.—Pyrotechnic compounds, suitable for photo graphic use, can be procured at the firework manufacturers. You had better not try to make it yourself, being, as we infer, entirely unused to such manipulations. Burton’s “Modern Photography,” published by Piper and Carter, Castle Street, Holborn—a new edition of which has just been published—will prove the best guide for you, as “a new amateur,” to follow. II. Geary.—Bromide of silver is reduced by direct action of light without a developer, but the action is slow. It is very common to find an impression visible to the eye on a plate after exposure of a portion of it to light. Sometimes—as when there is a light window photographed simultaneously with a dark interior—a visible image is produced in the camera. B. G. Lennon.—The address you ask for is Poplar Walk, Herne Hill, S.E. A, K.—We regret that we cannot assist you in the matter. Criticism upon a matter of courtesy is not within our scope. J. M.—We do not undertake to give legal advice, but we should think that you have a remedy in the County Court. We cannot publish a caution against dealing with any particular house. If the matter came before a judge, and were decided in your favour, a publication of the report of the case would probably be sufficient as a “ caution.” W. S. Fothergill.—1. Such excellent transparencies for the lantern have been made, both by superposition from a negative of the same size, and by reduction in the camera from larger plates, that it is impossible to say that either method will give better results than the other. 2. The use of a luminous tablet as the source of light for printing upon gelatine plates is, doubtless, favourable to uniformity of exposure; but this may be attained with sufficient exactness by less troublesome methods. 3. The change which is spoken of in gelatino-chloride plates refers to what takes place by keeping in an atmosphere not perfectly pure, whilst the chloride of silver is in the film. After fixing, the pic ture has been observed to change when the hypo has not been thoroughly removed. 4. If you varnish your transparencies, you can use a rather dilute lac varnish and dry by heat, as when varnishing a negative. Perspective.—For plates which show weakness and fog under the usual pyro developer, try the following Pyrogallic acid 3 grains Bromide of potass „ Water 2 ounces Liq. amm. fort 1 minim As the development progresses, a little more ammonia may bo added. 2 hotographs Gegistered. J. Bamforth (10lmfirth)—1 Photo, each of Eyam Church (Derbyshire), Eyam Village (Derbyshire), House at Eyam where the plague broK out, The Lovers’ Leap (Stony Middleton), Middleton Dale, Eyam Dale, Saxon Cross (Eyam Churchyard), Mompresson'sTomb (Eyam Chureh Mompresson’s Well (Eyam), Sun Dial (Eyam Church); 2 Photos. Cucket Church (Eyam). A. Donald (Dundee)—Photo, entitled “ The Ravelled Hank.” . F. Whaley (Lincoln)—2 Photos, entitled “Fortune Teller and her Vic - tims” ; Photo, entitled “ Only for my Ears.” Uhe Ahotographit Hehs. SUBSCRIPTIONS. Including Postage to any part of the United Kingdom:— Yearly ... 15s. Od | Half-Yearly ... 7s. 8d. | Quarterly ... 3s. - To the United States, the Continent, and the Colonies:— , Yearly ... 17s. 4d. I Half-Yearly ... 8s. 8d. | Quarterly ... 4s. * To India (Yearly) 19s. 6d. For Advertisement Scale y see page v. Advertisements should be forwarded (prepaid) to' Piper and Car ' 5, Castle Street, Holborn, E.C., to reach the office not later than no -re Thursday. A fee of 6d. must be forwarded when the P ubl ishen they expected to receive and forward replies to Advertisements ; and "ename undertake the receipt of replies, they must be entrusted with the may and address of advertiser, for revelation to applicants, in case they deem it necessary.