The photographic news

• Bandzählung: 6.1862
• Erscheinungsdatum: 1862
• 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-id1780948042-186200003
• PURL: http://digital.slub-dresden.de/id1780948042-18620000
• OAI: oai:de:slub-dresden:db:id-1780948042-18620000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Seite 1-72 fehlen in der Vorlage. Vorlagebedingter Textverlust.
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

FEB: 14, 1862.] THE PHOTOGRAPHIC NEWS. humour. A large artificial eye was then built up of a glass globe filled with water, having a black paper iris with an an opening in it, for the pupil, in front of this a lens, and at the back a tissue paper retina. Objects were held in front of this large eye, and upon being illuminated by the electric light, they were'seen by the audience to be distinctly projected on the tissue paper retina at the back, but in an inverted position. This was explained to be the case with the human eye, the image on the retina of all objects which are looked at being in an inverted position. For distinct vision, it was shown to be necessary that the rays from every point of an object should come to a focus upon the retina. Some eyes, however, refract too much and bring the rays to a focus too soon; to remedy this defect a divergent lens was shown to be necessary to be placed before the eye ; this was explained to be short sight. Other eyes, on the contrary, do not refract enough, and to help them, a convergent lens is placed before the eye; this is long sight. Different spectacles were then taken and exhibited in the beams of the electric light. The action which they exercised on the rays was clearly visible. In conclusion a few words were said upon the action of light upon the eye. The effect does not subside the moment the light ceases, but endures about a quarter of a second after the light has ceased to shine. A succession of sparks, therefore, which follow each other at intervals of a quarter of a second would, appear as a continuous line, and if the end of a burn ing stick were taken and moved round in a circle in about the fifth of a second, the circle would appear as a continuous line of light. Instead of a burning stick a beam of light was reflected, by means of a looking glass, to the ceiling, when upon rotating the mirror, the fine luminous index travelled round and gave the appearance of a continuous ring of light, because every revolution was accomplished within the time that the image took to subside. ON A NEW PROCESS OF PHOTOGRAPHY WITH OUT SILVER. BY DR. T. L. PHTPSOX, F.C.S. Member of the Chemical Society of Paris, &c., &c. This process, which is founded upon the use of oxalate of iron, was discovered by me about a year ago. I gave a slight sketch of it in the Moniteur de la Photo- graphie of Paris, for October 1st 1861, and I did not intend to say anything more about it until I had made further experiments, with a view of testing its value in comparison with the use of salts of silver. But a few weeks ago, to my surprise, I perceived that Mr. Reynolds had brought it before the Dublin Chemical Society as a novelty, and more over as a discovery of his own. But this author has had recourse to nitrate of silver to finish his proof, whereas in my process, no silver is used at all. It is well known that light has a peculiar action (a reductive action) upon many organic salts of iron, more especially upon the oxalate of peroxide of iron, which it reduces to the state of oxalate of protoxide. The first of these salts forms beautiful emerald green, prismatic crystals, extremely soluble in water, and decomposable by light; the hitter salt is yellow, insoluble in water, and not influenced by light. The first thing to be done, is to prepare a concentrated solution of oxalate of peroxide of iron. For this purpose I a e a solution of chloride of iron, and having precipitated e pel oxide of iron by ammonia, I collect it upon a filter an wash it with boilin water, after which this acid is dis- 80 vedin a warm on. .. ted solution of oxalic acid. A peautifu emerald g oen. solution is thus obtained, which mus ! e concentrat ed i little by evaporation, and then set aside in a dark placoforuse 1 If this solution be exposed to the sunlight, microscopic yellow crys a s o loxal ite qi protoxide of iron are deposited, more or ess rapic y, tin 1 the solution contains no more iron, and has become erfeotly colourless. Upon this remarkable decompose H ,. fot ided the process of which I speak. The paper destined to receive the photographic image is floated for about ten minutes upon the green solu tion of oxalate of peroxide in a flat dish or capsule, to which a certain quantity of oxalate of ammonia has been added; the whole of course being kept away from the daylight, and at the expiration of that time, the paper is taken out of the solution and hung up by one of its corners to dry. Let us suppose, for example, that a positive proof is required; the paper thus prepared is placed behind th s negative and exposed to the light for ten or twenty minutes, according to the weather. It is then well washed with distilled water or with rain water (spring water will not answer, on account of the lime it contains which decomposes the image by forming oxalate of lime). All the non-decom- posed oxalate of peroxide of iron is thus washed from the proof, and a feeble yellow image of oxalate of protoxide, scarcely visible, is left upon the paper. The best means I have hitherto discovered of developing the image and obtaining proofs equal in tone, colour, and vigour, to those obtained with salts of silver is as follows :— The faint yellow proof is plunged for a little while into a solution of permanganate of potash, to which a few drops of ammonia have been added. In this bath the image soon becomes brown and distinctly visible ; it is then withdrawn, washed, and plunged into a solution of pyrogallic acid, where it is allowed to remain for half-an-hour, after which it is taken out, washed, and dried. The image thus developed is a very dark brown, and can be distinguished with difficulty, by inexperienced eyes, from proofs obtained with silver, the tones are peculiarly soft and permanent in the proofs I have made. This process is, therefore, extremely simple, and as the use of silver is quite excluded, I imagine it will prove econo mical. A few experiments I have made without a camera seem to indicate that oxalate of iron may be used in the camera for producing negatives, which must be afterwards developed, as above, with permanganate of potash and pyro gallic acid. But I should much like to hear the results this process, or some modification of it, would furnish in the hands of a practised photographer. THE PHOTOGRAPHIC PLANE TABLE OF M. AUGUSTUS CHEVALLIER* BY LIEUT. PATE. These statements are all the results of operations made by ourselves for the purpose of testing the apparatus. Upon being invited, M. Chevallier did not hesitate to come to Arras to put his instrument to the proof. Neither the officers who took part in the experiments nor myself are ex pert photographers, so that our sweeps of the horizon are not so sharp as might be obtained with more experience and with better materials ; but this question of sharpness of image in the pictures obtained by a continuous rotary motion so successfully solved by MM. Martens, Garella, Baldus, and many others, is a decided progress accom plished in photography and cannot form an objection in this place. We have operated :—1st. With fixed sectors of 5° each. 2nd. By a continuous motion. The two methods have not only given identical results, but the plan of the front of the citadel of Arras, executed during these operations has fur nished a result completely in harmony with the very exact plans deposited with the regimental school of engineers. We can, therefore, attest the great excellence of this instrument, which Colonel Valdes, in his report to General Zara del Valle, describes in the following terms :— “ The ingenious photographic process devised by M. Chevallier is entirely free from error, very rapid in execu tion, and requires, in the triangulator, no other special knowledge than that of photography.” Beside its applications to ordinary topography, this instrument is susceptible of a great many others, which are * Concluded from p. 64.