Llewelyn B. ATKINSON, 
"Seeing to a Distance by Electricity", 
in The Telegraphic Journal and Electrical Review
December 13, 1889.

 
Notice 

    Le premier article connu de Ll. B. Atkinson "The Telectroscope", est paru dans English Mechanic and World of Science, 5 May 1882. 

   L'article que Ll. B. Atkinson publie en décembre 1889 est une réponse à la traduction en anglais de l'article H.W., "Sur la vision à distance par l’électricité par L. Weiller", La Lumière électrique, 34, 16 nov. 1889 parue dans The Telegraphic Journal and Electrical Review le 29 novembre. Atkinson reconnaît dans la description de la "roue à miroirs" de Lazare Weiller un appareil similaire à celui qu'il indique avoir construit dès 1882.  Cet appareil a été exposé le 5 mars 1929 devant la Television Society et est à présent conservé au Science Museum de Londres. On peut en voir des photos dans un article paru dans la revue Electrician du 15 mars 1929. Si la revendication d'Atkinson d'avoir construit cet appareil en 1882 est bien exacte, on pourrait lui attribuer le mérite d'avoir conçu un mécanisme d'analyse de l'image deux ans avant le disque de Nipkow (1884) et sept ans avant l'article "De la vision à distance par l'électricité", de Lazare Weiller (1889). Malheureusement, il n'existe pas de preuve formelle concernant la date de réalisation de cet appareil.

 



L'appareil de Atkinson présenté en 1929 à la Television Society comme ayant été construit en 1882 (The Electrician, 15 mars 1929).

Atkinson a pu construire son appareil sur base de l'hypothèse développée par Weiller. Mais, comme il indique par ailleurs qu'il possède toujours ses modèles - sous entendu : leur existence est vérifiable - il n'aurait eu qu'une quinzaine de jours pour les construire après sa prise de connaissance de la proposition de Weiller.  Par ailleurs Weiller était étudiant à Oxford dans la première moitié des années 1880 et il a pu avoir connaissance sur place des travaux d'Atkinson. Sauf à découvrir de nouveaux documents, la question de la priorité est donc, à ce stade, indécidable.

A notre connaissance cet article d'Atkinson a suscité peu d'échos après sa parution. On notera cependant que William Lucas (le "W.L." auquel Atkinson répondait dans article de 1882), le cite dans sa lettre au magazine Nature, publiée le 27 juin 1936, pour revendiquer la priorité de l'idée de balayage (scanning).




  In your issue of November 29th, under the heading "Seeing to a Distance by Electricity," you publish a description of a proposed method of seeing by electricity, but I gather from the remarks on the mechanism to be employed, that no actual trial has been made.

    Some seven years ago (1882) I designed an identical apparatus and conducted a considerable number of experiments with roughly constructed models of the apparatus (which models I still possess), and it may interest some of your readers to know how far the experiments were successful, and why they failed to give the results anticipated.

    The apparatus consists essentially of the transmitter, the line and synchronisers, and the receiver. In the line and synchroniser I include the arrangement of inclined mirrors or oscillating prism or lens which may take its place.

    One reason that leads me to suppose that the apparatus, as described, exists so far only on paper, is that selenium is the medium for transforming the light variation into the electric variation, whereas all my experiments, and so far as I have been able to gather the experiments of others, show it to be unsuitable, on account of its great variation in sensitiveness with varying battery powers, and even in course of time by molecular change, whilst its high resistance makes the currents available very small.

    Coming also to the receiver, I am aware that more sensitive or louder speaking magnetic telephones are made now than when I tried my experiments but I was unable to produce, by means of the magnetic telephone, any variation in a gas flame, with the movement of the plate, producible by variation in current, such as a selenium transmitter, or even a microphone (acoustic) transmitter will give. Probably the reason of this is that the sounds are produced in a telephone more by molecular movement In the plate than by molar movement of the plate.

    Having thus mentioned how far the experiments succeeded in the form described, I will mention some further experiments made on the same lines.

    In place of selenium, I have tried as a transmitter a mixture of carbon and sulphur, In this case the luminous variation being first transformed into a heat variation, and owing to the sensitiveness of this mixture to heat, as affecting its resistance, into an electrical variation.

    The variation, however, was neither powerful enough nor rapid enough. Similar experiments with thin metal films, after the manner of Prof. Langley's "bolometer," gave much the same results.

    Coming to the receiver, and abandoning the magnetic telephone, I tried the "moto-graph" or chalk-cylinder telephone of Edison, and in this case the gas flame movement can be obtained with the variations that could be produced in a microphone (acoustic) transmitter, and I think with the variations obtainable with the selenium transmitter. (I do not now remember this with certainty.) But here the defects of the gas flame receiver are apparent. It is not sufficiently dead beat, the position of the gas flame depends not on the position of the telephone membrane, but on the rate of change of its position, which is not quite the same thing, as a little consideration will show.

    Of other magnetic forms, I tried an electro-magnet with a light stiff armature, carrying a thin plane plate, pressing against a slightly convex plate, so as to give a series of Newton's rings. Viewed by monochromatic light (sodium flame), the centre spot is black or light, by a variation in position of half a wave length of yellow light. The chief defect of this form is that the illumination is scarcely intense enough to sufficiently impress the retina for the purpose in view. I also tried forms in which a small mirror was strung on a tightlystretched wire, so as to have a very small time of oscillation, the movement of the magnetic armature being highly magnified by several different devices. They did not prove, however, to be sufficiently deat beat.

    Having shown in what way these experiments failed, and having since studied the subject further, I might suggest what appears to me to be the most probable lines for investigation now offering.

    1. The use of electro-chemical transmitters - that is, small cells in which silver bromide is formed by electrolysis-and the action of light on this salt, producing some other salt (? sub-bromide), alters the E.M.F. of the cell. Various researches on this subject have been published which appear promising.

    2. The use as a receiver of a Geissler tube, more especially a "stratified" tube, the action here being very instantaneous and the position of the strata alterable by trifling alterations in condition.

Llewelyn B. Atkinson.

Historical Note - The idea of using an integrating apparatus for producing the whole image from one element in the time during which the image will remain on the retina was first, I believe, published in the English Mechanic about 1881 or 1882, and was then, as far as publication goes, new.

 

 

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