The photographic news

• Bandzählung: 7.1863
• Erscheinungsdatum: 1863
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186300004
• PURL: http://digital.slub-dresden.de/id1780948042-18630000
• OAI: oai:de:slub-dresden:db:id-1780948042-18630000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

the water flowing from between them towards their ends, and thus prevents any tendency to float the prints down their inclined surfaces. If the shelves are not perforated, the prints have a slight tendency to cling to their under surfaces. But when dia phragms of perforated zinc are used, the papers rise and fall with the water, and float about in the little space between the shelves with perfect freedom, leaving apparently nothing to be desired. Unfortunately, however, zinc acts on the pictures and cannot he used. Probably, ebonite similarly perforated will be found to answer. Should it prove expensive, or otherwise unfit, a material perfectly suited for these dia phragms will be a desideratum. If we now imagine Mr. Ponting’s experiment with the ink to be repeated with the arrangements here recommended, we shall see at once that the first change would empty out the ink, the second would rinse the trough, and the third Would show no trace of it; and thus a few pints of water and a few minutes in time would effect what he found to require in a stationary tray 80 gallons of water and 3} hours. But it is worth while to consider a little more closely how the removal of soluble salts from the tissue of paper is really effected. If we could cause streams of water to permeate every pore and to carry with them by mechanical force all the matter which could be either dissolved or suspended, then the pro cess of washing would be definite, absolute and perfect, and the duration of the operation would only depend on the rapidity of the streams. But we possess no such power. In the first place, a stream of water but very slowly removes water which is already adhering to a solid. Every chemist knows how surprisingly insufficient even the repeated rinsing of a test-tube often proves. In the circulation of the blood through the capillaries, and in the flow of any fluid through a small tube, the liquid immediately in contact with the pipe appears to be stationary, and is known to physiologists and physicists as the still layer. The phenomenon is no doubt due to the fact that particles of water arc more power fully attracted by those of most solid bodies than by each other, as is shown by the concave surface assumed by water in all ordinary vessels. These considerations show how easily the particles of water in actual contact with a picture may allow others to flow over them without becoming themselves detached. By draining, however, a large portion of this adhering water is removed; and hence every experiment shows a much larger proportion of hyposulphite in the last drainings than in the bulk of the water discharged at each change. But for the removal of the hyposulphites from the tissue of a picture we are wholly de pendent upon the property which soluble salts possess of Effusing themselves through the solvent which surrounds them; and thus it is that the process of washing becomes indefinite, comparative, and, in theory, only approximately perfect. All we can do is to secure the conditions most favourable for diffusion. What these conditions are is thus stated by Professor Graham, whose beautiful researches almost created this im portant branch of chemical physics. He says, “ The general law of diffusion appears to be this:—The velocity with which a soluble salt diffuses from a stronger into a weaker solution is proportioned to the difference of concentration between two con tiguous strata’’ (Graham's Elem. of Chern, ii. C08). The arrangements just described appear to secure these conditions with the least possible labour ; but I am anxious that it should be clearly understood that time must ever remain an important element in any process depending on diffusion. Each change of water subdivides the quantity of the salts in solution, and at first greatly weakens the solution left in the paper; but for the very reason, in accordance with the law just stated, diffusion goes on more and more slowly, the difference between the solution in the paper and the contiguous stratum of pure water becoming less and less. Hence the great practical importance of using a moderately small stream of water, and of continuing the process for a considerable time after all appreciable traces of the salts have disappeared. The principle of applying water in the most efficient manner to some primary purpose by making use incidentally of its own mechanical power, on some plan analogous to the one I have adopted, may probably admit of application in other processes. But if, by lessening the labour of the con scientious and the temptation of the unscrupulous, the sug gestions here made should promote the better washing of photographs, and thereby the reputation of the art, my hopes and intentions will be fully realized. Aroreedigs of Societies. London PHOTOGRAPIIC Society. The usual monthly meeting of this Society was held in King’s College on the evening of Tuesday the 1st inst. Col. Stuabt WORTLEY in the chair. The minutes of a former meeting were read and confirmed. The Chairman said, in accordance with the 7th rule of the society, the names of retiring officers would now be read together with those nominated by the council to fill their places. The rule was as follows:—All officers of the society shall be annually elected, with the exception of the Secretary and such members of the council as may not go out of office by rotation or otherwise. The mode of their election shall be by ballot. The council at the ordinary meeting in December in each year shall declare the names of the members of council whom they recommend to retire, and (lay before the society the names of those whom they have selected to supply their places. They shall also declare the names of the other officers they recommend for re-election, and cause a list to be suspended in the meeting room. In the event of any member of the society being desirous of proposing other names than those recommended by the council, a written list of the same shall be delivered to the Secretary at or before the ordinary meeting in January; and the same shall be read from the chair, and publicly suspended in the society’s room, with the list recommended by the council; and no member shall be eligible for election into the council unless he shall have been proposed in the manner and form above specified. The names of retiring officers and those proposed, were the Lord Chief Baron, President, who was proposed for re-election. Mr. Vignoles, Vice-President, Col. Stuart Wortley being pro posed in his place. Mr. Hamilton, Hon. Treasurer was pro posed for re-election. Tire retiring members of the council were Messrs. Vernon Heath, Peter Le Neve Foster, H. Pollock, Hennah, Col. Stuart Wortley, and Lord Henry Lennox. In their place were proposed for (election or re-election, Messrs. Elphinston Underwood, J. P. Gassiott, Josiah Slade, Sebastian Davis, H. Pollock, and the Hon. Warren Vernon. Any members of the society desiring to nominate other officers, must do so at the January meeting. The Secretary called attention to some charming figure studies and examples of double printing, by Mr. H. Cooper, Junr., taken in the open air, chiefly by Dallmeyer’s No. 1 triple lens, which were much admired ; also to some of Mr. England’s beautiful views of Swiss scenery, taken during the past sum mer. Mr. Spiller then read his paper on “ Photography in its Application to Military Purposes,” which was profusely illus trated with examples which were examined with great interest. No discussion followed. The Chairman, in proposing a vote of thanks, remarked, that, as Englishmen, they were all deeply interested, and him self pre-eminently so, in the subject Mr. Spiller had described so ably. He had to announce that, at the next meeting, Mr. S. P. Smith would bring before the members some further par ticulars regarding the alleged photographs of the Eighteenth Century. He trusted that all the members would interest themselves in gathering together any evidence bearing upon the subject, and enable the society to pronounce definitely upon the subject, whether this country could claim the origin of photography at the early date claimed, or whether hitherto received claims remained undisturbed. The following gentlemen were elected members of the so ciety:—Messrs. Howe, Goslett, 11. II. Michell, W. Rowland