Mons. SENLECQ, of Ardres, "The Telectroscope", 
Scientific American supplement, 
n° 275, April 9, 1881


    Cet article est le troisième que Scientific American publie sur le télectroscope de Senlecq, et il est cette fois signé par Senlecq lui-même.  Le texte correspond, avec quelques adaptations, à une  traduction en anglais des pages 9 et suivantes de la partie française de la brochure.


The Telectroscope

    This apparatus, which is intended to transmit to a distance through a telegraphic wire pictures taken on the plate of a camera, was invented in the early part of 1877 by M. Senlecq, of Ardres. A description of the first specification submitted by M. Senlecq to M. du Moncel, member of the Paris Academy of Sciences, appeared in all the continental and American scientific journals. Since then the apparatus has everywhere occupied the attention of prominent electricians, who have striven to improve on it. Among these we may mention MM. Ayrton, Perry, Sawyer (of New York), Sargent (of Philadelphia), Brown (of London), Carey (of Boston), Tighe (of Pittburg), and Graham Bell himself. Some experimenters have used many wires, bound together cablewise, others one wire only. The result has been, on the one hand, confusion of conductors beyond a certain distance, with the absolute impossibility of obtaining perfect insulation ; and, on the other hand, an utter want of synchronism. The unequal and slow sensitiveness of the selenium likewise obstructed the proper working of the apparatus. Now, without a relative simplicity in the arrangement of the conducting wires intended to convey to a distance the electric current with its variation of intensity, without a perfect and rapid synchronism acting concurrently with the luminous impression, so as to insure the simultaneous action of transmitter and receiver, without, in fine, an increased sensitiveness in the selenium, the idea of the telectroscope could not be realized. M. Senlecq has fortunately surmounted most of these main obstacles, and we give today a description of the latest apparatus he has contrived.


    A brass plate, A, whereon the rays of light impinge inside a camera, in their various forms and colors, from the external objects placed before the lens, the said plate being coated with selenium on the side intended to face the dark portion of the camera. This brass plate has its entire surface perforated with small holes as near to one another as practicable. These holes are filled with selenium, heated, and then cooled very slowly, so as to obtain the maximum sensitiveness. A small brass wire passes through the selenium in each hole, without, however, touching the plate, on to the rectangular and vertical ebonite plate, B, Fig. 1; from under this plate at point, C. Thus, every wire passing through plate, A, has its point of contact above the plate, B, lengthwise. With this view the wires are clustered together when leaving the camera and thence stretch to their corresponding points of contact on plate, B, along line, CC. The surface of brass, A, is in permanent contact with the positive pole of the battery (selenium). On each side of plate, B, are let in two brass rails, D and E, whereon the slide hereinafter described works.

    Rail, E, communicates with the line wire intended to conduct the various light and shade vibrations. Rail, D, is connected with the battery wire. Along F are a number of points of contact corresponding with those along CC. These contacts help to work the apparatus, and to insure the perfect isochronism of the transmitter and receiver. These points of contact, though insulated one from the other on the surface of the plate, are all connected underneath with a wire coming from the positive pole of a special battery. This apparatus requires two batteries, as, in  fact, do all autographic telegraphs - one for sending the current through the selenium, and one for working the receiver, etc. The different features of this important plate may, therefore, be summed up thus :

    FIGURE 1.

    D. Brass rail, grooved and connected with the line wire working the receiver.

    F. Contacts connected underneath with a wire permanently connected with battery.

    C. Contacts connected to insulated wires from selenium.

    E. Brass rail, grooved, etc. like D.


    A small slide, Fig. 2, having at one of its angles a very narrow piece of brass, separated in the middle by an insulating surface, used for setting the apparatus in rapid motion. This small slide has at the points, DD, a small grrove fitting into the brass rails of plate. B, Fig.1, whereby it can keep parallel on the two brass rails, D and E. Its insulator, B, Fig. 2, corresponds to the insulating interval between F and C. Fig.4.

   A, Fig. 3, circular disk, suspended vertically (made of ebonite or other insulating material). This disk is fixed. All round the inside of its circumference are contacts, connected underneath with the corresponding wires of the receiving apparatus. The wires coming from the seleniumized plate correspond symmetricaly, one after the other, with the contacts of transmitter. They are connected in the like order with those of disk, A, and with those of receiver, so that the wire bearing the N° 5 from the selenium will correspond identically with like contact N°5 of receiver.

    D, Fig. 4, gutta percha or vulcanite insulating plate, through which pass numerous very fine platinum wires, each corresponding at its point of contact with those on the circular disk, A.

    The receptive plate must be smaller than the plate whereon thon light impinges. The design being thus reduced will be the more perfect from the dots formed by the passing currents being closer together.

    B, zinc or iron or brass place connected to earth. it comes in contact with chemically prepared paper, C, where the impression is to take place. it contributes to the impression by its contact with the chemically prepared paper,

    In E, Fig.3, at the center of the above described fixed plate is a metallic axis with small handle. On this axis revolves brass wheel, F., Fig.5.

   On handle, E, presses continuously the spring, H, Fig. 3, bringing the current coming from the selenium line. The cogged wheel in Fig. 5 has at a certain point of its circumference the sliding spring, 0, Fig. 5, intended to slide as the wheel revolves over the different contacts of disk, A, Fig. 3.

    This cogged wheel, Fig. 5, is turned, as in the dial telegraphs, by a road working in and out under the successive movements of the electro-magneted, H, and of the counter's spring. By means of this rode (which must be of a non-metallic material, so as not to divert the motive current), and of an elbow lever, this alternating movement is transmitted to a catch, G, which works up and down between the cogs, and answers the same purpose as the ordinary clock anchor.

    This cogged wheel is worked by clockwork inclosed between two disks, and would rotate continuously were it not for the catch, G, working in and out of the cogs. Through this catch, G, the wheel is dependent on the movement of electro-magnet. This cogged wheel is a double one, consisting of two wheels coupled together, exactly similar one with the other, and so fixed that the cogs of the others. As the catch, G, moves down it fress a cog in first wheel, and both wheels begin to turn, but the second wheel is immediately checked by catch, G, and the movement ceases. A catch again works the two wheels, turn half a cog, and so on. Each wheel contains as many cogs as there are contacts on transmitter disk, consequently as many as on circular disk, A, fig. 3, and on brass disk within camera.

    Having now described the several parts of the apparatus, let us see how it works. All the contacts correspond one with with the other, both on the side of selenium current and that of the motive current. Let us suppose that the slide of transmitter is on contact N°.10 for instance ; the selenium current starting from N°. 10 reaches contact 10 of rectangular transmitter. Half the slide beating on this point, as also on the parallel rail, communicates the current to said rail, thenceto line, from the line to axis of cogged wheel, from axes to contact 10 of circular fixed disk, and thence to contact 10 of receiver. At each selenium contact of the rectangular disk there is a corresponding contact to the battery and electro-magnet. Now, on reaching contact 10 the intermission of the current has turned the wheel of cogs, and so brought the small contact, 0. Fig 5 of N°. 10 of the fixed circular disk.

    As may be seen, the synchronism of the apparatus could not be obtained in a more simple and complete mode - the rectangular transmitter being placed vertically, and the slide being of a certain wheight to its fall from the first point of contact sufficient to carry it rapidly over the whole length of this transmitter.

    The picture is, therefore, reproduced almost instantateously ; indeed, by using platinum wires on the receiver connected with the negative pole, by the incandescence of these wires according to the different degrees of electricity we can obtain a picture, of a fugitive kind, it is true, but yet so vivid that the impression on the retina does not fade during the relatively very brief space of time the slide occupies in traveling over all the contacts. A Ruhmkorff coil may also be employed for obtaining sparks in proportion to the current emitted. The apparatus is regulated in prevcisely the same way as dial telegraphs, starting always from first contact. The slide should, therefore, never be removed from the rectaungular disk, whereon it is held by the grooves in the brass rails, into which it fits with but slight friction, without communicating any current to the line wires when not placed on points of contact.

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