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, D D, a
small groove 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. 1.
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 symmetrically, 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 No. 5 from the
selenium will correspond identically with like contact No. 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 the 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 plate 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.
[Illustration: FIG. 2]
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, O, 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 rod
working in and out under the successive movements of the electro-magnet,
H, and of the counter spring. By means of this rod (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.
[Illustration: FIG. 3]
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 one correspond with the void between the cogs of the
others. As the catch, G, moves down it frees 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.
[Illustration: FIG. 4]
[Illustration: FIG. 5]
Having now described the several parts of the apparatus, let us see how it
works. All the contacts correspond one 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 No. 10 for instance; the selenium
current starting from No. 10 reaches contact 10 of rectangular transmitter,
half the slide bearing on this point, as also on the parallel rail,
communicates the current to said rail, thence to line, from the line to
axis of cogged wheel, from axis 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 10 cogs, and so brought the small contact, O, Fig. 5,
on No. 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 weight 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 instantaneously; 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 precisely the same way as dial telegraphs, starting always from first
contact. The slide should, therefore, never be removed from the rectangular
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.
* * * * *
[Continued from SUPPLEMENT No. 274, page 4368.]