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The photographic news
- Bandzählung
- 24.1880
- Erscheinungsdatum
- 1880
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- SLUB Dresden
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- Public Domain Mark 1.0
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- urn:nbn:de:bsz:14-db-id1780948042-188000001
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- http://digital.slub-dresden.de/id1780948042-18800000
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- oai:de:slub-dresden:db:id-1780948042-18800000
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- Exemplar unvollständig: Seite 1-82 in der Vorlage nicht vorhanden
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- Bandzählung
- No. 1151, September 24, 1880
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
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- Wahlperiode
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Zeitschrift
The photographic news
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Band
Band 24.1880
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- Register Index 631
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Band
Band 24.1880
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- Titel
- The photographic news
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September 24, 1880.] THE PHOTOGRAPHIC NEWS. 463 kept down in the process of transformation by treatment with tincture of iodine, it could not be obviated altogether. Neither did subseqent bathing of the positive in a hypo sulphite or cyanide bath effect the purpose satisfactorily ; indeed, this radical treatment frequently, as might be expected, caused the image to disappear altogether. M. Jahns next experimented with iodised collodion and an iron developer, but as no results were here obtainable, he was led to infer that the presence of ammonia was the key to the phenomenon. Ammonia was in excess upon the ex posed plate, he reasoned, and dissolved the silver film formed on development in the dark room; further, the pyrogallic acid present at the same time developed, under the action of diffused light such parts of the negative as had not been impressed in the camera. Dr. Vogel hardly thinks that the dissolving of the silver image in this way is probable ; but we may here remark that we are only quoting M. Jhns’s theory of his process. To effect the dissolution of the negative image more energetically, M. Jiihns employed strong nitric acid ; this answered the purpose completely in all cases where bromine salts were employed in the image, the positive image re maining behind on the plate clear and distinct. This posi tive had now to be exposed anew to daylight, under the action of a developer, in order to secure a plate free from fog. Our readers will find in M. Jiihns’s process much that is already familiar to them ; but we have Dr. Vogel’s word for it that it is not a mere laboratory experiment that is here detailed, but a practical process whereby transparent positive photographs may be produced directin the camera—the clear and delicate qualities of which vie with those of a thoroughly good negative. Zotes. Professor Graham Bell, the well-known inventor of the telephone, has lately succeeded, it is said, in still further improving telegraphic communication. He employs a beam of light in place of a telegraph wire, and conveys sound from station to station by the aid of this shining ray. Professor Bell has telephoned along a beam of light in this manner to a distance of 800 feet. He performed the feat by the aid of selenium, a sub stance, as we have pointed out in these columns, that undergoes considerable electrical change according as it isplacal in light or shadow. By constructing the « receiv ing instrument" of this material, and controlling the form and character of the light vibrations that fall upon the selenium, sound can be controlled, and all varieties of speech reproduced. At any rate, so says the paper which Professor Bell recently read before the American Associa tion for the Advancement of Science. A novelist of our acquaintance has copies of his MS. taken by photography. As he reads and corrects a chapter sometimes a month after it is written, the copying press is unsuitable. A friend of his, however, has no difficulty in reproducing twenty quarto pages on a twelve-inch plate, the writing, though very small, being perfectly legible to good eyes. The MS. of a three-volume novel, like Homer's Iliad, might thus be contained in a nutshell, provided it is a cocoanut, to which the story-teller of old refesred. M. Pifre has communicated to the Paris Academy of Sciences some further results which he has obtained in his endeavours to utilise heat from sunshine. When the sky is clear he has no difficulty in getting sunshine to boil water, in a boiler he has specially constructed, within the space of forty minutes. This is certainly making the sun into a useful servant. The boiler in question is comparatively large, containing no less than 50 litres of water. The solar heat is con centrated by means of a reflector upon the blackened sur face of the boiler, the reflector consisting of three truncated cones placed at an inclination of 45°. Steam can only be got up, of course, on a clear day, and is maintained so long as the sun shines. Among the officers killed in the last action at Candahar, under General Roberts, is the Superintendent of Signalling, Captain Straton, who has done such marvels with the helio graph during the campaign in Afghanistan. The service was a most hazardous one, since it consisted in placing mirrors upon lofty eminences and isolated spots whence signals could be reflected a long distance; it was when engaged upon one of these expeditions at the close of the campaign that the gallant officer met with his death. These mirrors are but ten inches in diameter, and, if placed on a high hill, signals may be flashed over the heads of an enemy to a distance of fifty or sixty miles. There is no fear of hostile calvary cutting the line of communi cation, as if it were a telegraph wire ; and, moreover, it is only those accurately placed vis-a-vis who can read the signals. These appear to the eye like tiny blight spots or stars in the landscape afar off, and, as they remain visible to the eye for a short or long time, they are termed short or long signals, and of these the signal alphabet is com posed. It is a pity the term heliograph has been given to this form of signalling, as the word has already been appro priated by photographers. But there is no reason why the camera should not be called in to write down these light signals, and thus produce a veritable heliograph. A tele scopic tube in front of the lens would be necessary to get a definite image of the point of light as it appears and dis appears ; and if the camera were fitted with a movable band of sensitive tissue (say the Warnerke tissue), we should have a very serviceable “ receiving instrument." Since the sensilive film would always be moving at a certain speed, short signals would then be written down in the shape of a short line, and long ones by a long line, exactly as in the well-known Morse code. A Paris photographer on the Boulevard des Italiens has hit upon a plan of operating and advertising at the same time. He employs electricity for taking pictures at night, and instead of hiding his light under a bushel, per mits it to shine down upon the cafes and promenaders in that populous thoroughfare.
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