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48 THE PHOTOGRAPHIC NEWS. [January 22, 1869. ■with an air-pump, and when the smaller cask has been filled with gasoline, and the atmospheric air is injected through the pipes, it rises through the gasoline in the form of bubbles; in other words, the atmospheric air, being forced through gaso line, assumes the nature of gas, and that gas burns as brilliantly as that produced from bituminous coal. It is obvious that the cost of lighting a house is reduced to a minimum when all that is needed is a barrel of gasoline and an air-pump. This inven tion will be of inestimable service to country villagers and in dividual proprietors, as the cost of lighting premises will be less than entailed by candles, coal oil, or coal gas, and the the risk of explosion must be very much diminished in consequence of the mode of manufacture. We believe that gas made in the man ner we have described is inodorous. This may be considered an objection, as an escape cannot be noticed with the same certainty as with the odorous gas coal. We have thus almost a certainty of cheap light at a cost much below what that essential article now entails upon us.—Montreal paper. Wo Corresyouents. Senrab Egroeg.—In the article by Mr. Hughes in our Year- Book, to which you refer, where he states that he has frequently kept a plate three hours between sensitizing and developing, he clearly means that the plate has been kept three hours after it has left the bath of distilled water. If you read the preceding sentence you will see this, for he remarks that it is surprising how long a plate will remain “ uniformly moist ” “when it is wet with little but plain water.” The plates can, of course, be carried to a distance if, as Mr. Hughes further adds, “ the usual means of preventing evaporation be adopted, such as putting a thick pad of wet blotting-paper behind the plate, and a sheet of oiled silk, or other waterproof material, as well.” One of the chief difficulties, ordinarily, of keeping a plate long between exciting and developing is the concentration of the free silver on the surface of the plate, causing stains. When the free silver has been removed by washing, no such danger exists, and if care be taken to prevent the film actually drying, the plate may be kept a long time, as you will doubtless see. W. H. J.—We have not heard of any one who has tried the pro cess. 2. Equivalent to glacial acetic acid, we believe; but it is a commercial term, descriptive of a quality commonly used. G. E.—There is no work in print devoted to enlarging. It would bo impossible in this column to give you instructions how to construct enlarging apparatus, and how to use it. There are various modes of enlarging described in our back volumes and in our YEAR-Books. If you select a method and proceed with it, we can answer any special question relating to it in this column. First determine the method you wish to use, and then wo may give you hints how to proceed. An Amateur.—You may safely use the bath after the treatment you describe. 2. The lenses of the maker you name are gene rally pretty good. 3. You may keep bromo-iodized collodion for many months, of course keeping it properly stoppered and tied down. As a rule, it is best to keep it in the dark. 4. Pin holes arise from very many causes, but the most common cause is the saturation of the bath with iodide of silver. To get rid of this, add the silver bath to an equal bulk of distilled water, and filter out the precipitate formed. Then add sufficient nitrate of silver to make up to the proper strength. H. R. (Openshaw).—There is no mode in which the spots on the half-plate picture can be removed from the negative; but, with care, they may be touched out of each print so as to scarcely show. The spots have the appearance of having been caused by drops of water standing on the plate and condensing the light. 2. There are various modes of vignetting. One of the best, because it admits of the greatest variety of effect, and produces the least formality of shape, consists in the use of a piece of card with the aperture graduated by means of cotton wool. The vignetted print is pretty good. Perhaps the shade is a little heavy for a vignette, which usually requires to bo more delicate in effect than a fully printed out impression. For vignettes a lighter background is desirable. The tones generally are pretty good. Those you have marked "acetatebath" are best; but the negatives are also probably the best. Much depends on circumstances as to the number of prints which can be toned with a given quantity of gold. From one to three sheets of paper may be toned with a grain of chloride of gold. 4. Of the makers you name we prefer No. 1. Bromo.—We have not seen any description of the form of tent used in the Abyssinnian Expedition. Probably the maker, Mr. Meagher, can inform you. Citric Acid.—If the spots in question arise with one bath, and not with another, it seems tolerably clear that they are due to the bath; and this is the more probable seeing that pinholes are also produced by the same solution. These, and the sandy-looking deposit, suggest that the bath is supersaturated with iodide of silver. Dilute the solution with an equal bulk of water, filter, and add nitrate of silver to make up the strength. 2. The annual subscription to the North London Society is 10s. 6d. There is no entrance fee. B. Atkins.—The engravings you mention—"Eistward Ho!" and “ Home Again ”—are copyright. Pica.—If you place a negative in the place of the ground glass, and turn it towards a strong light, you ought to be able to get a good and sharp image on a screen placed at the proper distance. The negative should be turned towards the northern sky. not to direct sunlight, and care, of course, is required in adjusting the distance of the lens from the negative and from the screen. There is no work on enlarging. Amateur.—No. 1, of six inches focus, will probably answer your purpose best. You will see that on the amount of washing the degree of sensitiveness depends, and that the shorter the immer- sion in the nitrate bath the longer the washing needed, and vice versa. "Loox-BEFORE-YOU-LEAP."—We have not yet had an oppor- tunity of examining the albumen colours, but intend to do SO shortly. 2. The Carrier paper is exceedingly useful for very vigorous negatives. Its tendency is to give less vigour than ordinary albuminized paper, and therefore, with soft negatives, the prints are a little feeble. With very vigorous negatives il gives good results, and it is very useful to have in stock, as we find no deterioration on keeping. James Maycock.—-The prints you forward are excellent example’ of the oxymel process. The print on the wrong side of albu* minized paper is very good; but if printed a little more, and toned a little less, it would have been better still. The ten dency of albuminate of silver under the action of light is tn assume a brown tint; that of the chloride of silver to assume a violet tint; hence the treatment which would give a warm print with albuminized paper will give a cold effect with plain paper. To get a warm tone, use a weak or old toning bath, and be care ful not to over-tone. 2. It is difficult to speak of the peculiacity of Adam-Salomon’s pictures as due to any one thing. They are especially distinguished by fine light and shade, good posing and composition, fine modelling and great relief, combined witl much delicacy. They are also exceedingly rich in colour. 3. Copyright in books extends for forty years, or during the life of the author, and for seven years after his death. J. H. Johnson,—In the double chloride of gold and sodium, chlo rine, gold, and sodium are combined in their equivalent propor tions ; in a solution of gold in nitric and hydrochloric acid mad neutral by the addition of carbonate of soda, you have the sam thing, plus nitrate of soda and excess of chloride of sodiun Such a solution, however, generally answers very well W toning. J. H. Jewell.—We do not know of any views of Great Marlo* inexistence. 2. You will find incur Year-Book just issued some hints on the testing of cards for hypo. Oe (Truro).—The soft crayons supplied by any respectable artist 5 colourman, such as Newman, of Soho Square, will answer best Schuttz.—The Photo-relief Printing Establishment is at Hero- ford Lodge, Brompton. We have no doubt that you will obtatl permission to visit the works if you write to Mr. WoodburJ- Cards are issued admitting on certain days, we believe. George Hooper, Fred. Kirby, J. Roberts, and several othef Correspondents in our next. J Several Reviews and Articles in type are again compelled to stap‘ over until our next. Photographs Regstered. Mr. G. Barber, Derby, Photograph of the late Mias L. A. Pickering. Messrs. Galbraith, Jennings, & Co., Belfast, Two Photographs of Miss L. Willmore, as the Peerless Statt in “ Pygmalion.” *.* All photographs forwarded to the Publisher for registration recei attention at once ; but the pressure on our space sometimes compel 8 ., to defer the acknowledgment in this column. It should be borneN mind, therefore, that non-acknowledgment at once does not necessa" imply non-receipt or non-registration.
