I02 



NATURE 



\Nov. 30, 1876 



mistakes in transmission can be traced to the station and 

 person where they occur. 



The Recorder consists of a powerful electro-magnet, 

 between the poles of which a coil of fine insulated wire is 

 delicately suspended, so as to be able to move round a 

 vertical axis. The current from the cable is made to pass 

 through this coil of wire. When a current passes through 

 a coil suspended between the poles of a magnet, the 

 coil tends to take up a position with its plane at right 



Fig. 3. 



angles to the line joining the poles. There are two 

 weights suspended from the bottom of the coil, which, 

 wheii no current is passing, keep the plane of the coil in 

 the line joining; the poles of the magnet. When a posi- 

 tive current is passing, the coil tends to turn round a 

 vertical axis in one direction, and when a negative cur- 

 rent is passing, it tends to turn round in the opposite 

 direction. 



The coil is connected by means of silk fibres with a 

 very fine glass siphon, suspended so that one end dips 



into a metal box containing ink, and the other end hangs 

 down nearly touching a paper ribbon. The motion of the 

 coil is thus transmitted to the glass siphon. The metal 

 box containing the ink is insulated and is electrified by 

 means of an electrostatic induction machine while the 

 paper is connected with the earth. The ink being elec- 

 trified, is drawn from the point of the siphon and spurted 

 out in small drops on the paper. When no current is 

 passing they form a straight line on the paper as it is 

 drawn past the end of the siphon ; but 

 when a current passes through the coil, 

 it being deflected, draws the siphon to 

 one side, and the line on the paper is 

 no longer straight, but indicates the de- 

 flections of the coil. The well-known 

 Morse alphabet is used with the recorder. 

 A deflection of the siphon-point to one 

 side corresponds to a dot, and one to 

 the opposite side to a dash. 



Fig. I shows a front view of the 

 Recorder. B is the electrostatic induc- 

 tion machine, called the mouse-mill, 

 which is driven by an electro-magnet 

 inside the box D. The mouse-mill 

 serves two purposes. It generates elec- 

 tricity, which is communicated to the 

 box K, containing the ink, by means of 

 the rod P, and it draws the paper along, 

 past the siphon point. M M are the 

 electro-magnets and s is the coil of wire 

 suspended between them ; / is the 

 siphon, one end of which dips into the 

 ink-box K, and the other end is almost 

 touching the paper c. The paper 

 passes under the spring a which keeps 

 it stretched, over the roller b, then ver- 

 tically down, past the siphon point, to 

 the driving drum d. The battery used 

 for the electro-magnet M M and for the 

 mouse-mill is of the form of Daniell's bat- 

 tery known as the Tray battery. It is 

 fully described in Nature, vol. vi. p. 32. 

 Fig. 2 is an enlarged view of the sig- 

 nal coil and siphon. Fig. 3 shows a 

 front view of the suspension of the coiL 

 s is the coil suspended by a silk fibre 

 passing round the pulley r. From the 

 coil hang two weights, which can slide 

 up and down the guides z. The coil 

 surrounds a stationary piece of soft iron 

 placed there for the purpose of increas- 

 ing the intensity of the magnetic field. 

 A silk fibre v connects one corner of 

 the coil with one end of a vertical lever 

 u. The other end of the lever is con- 

 nected to the siphon / by means of 

 another silk fibre, and the motion of the 

 coil is thus communicated to the siphon. 

 In consequence of the electrostatic 

 capacity of submarine cables, a retar- 

 dation occurs in the transmission of 

 signals, so that when a current enters 

 at one end of a cable, a certain time 

 elapses before any effect can be de- 

 tected by the most delicate instrument at the other 

 end. Fig. 4, Curve I., represents the strength of the 

 current, received at the remote end of a cable, as it 

 gradually increases, when the end operated upon is con- 

 nected to one pole of a battery and kept permanently so. 

 The vertical ordinates represent the strength of the cur- 

 rent. The horizontal ordinates represent intervals of 

 time reckoned from the first application of the battery in 

 terms of an arbitrary unit, a. This unit of time, a, may 

 be defined as follows ; — Suppose a cable electrified so that 



