March 27, 19 13] 



NATURE 



99 



air and inking' becomes too limited. This precludes 

 the possibility of attaching the siphon directly to a 

 coil of a few turns, and means of magnifying the 

 motion of the coil and transmitting it to the siphon 

 have to be used. In this instrument (Fig. i) it is 

 accomplished by means of a fine fibre, E, which is 

 kept in tension by flat springs at each end. The fibre 

 is attached to an arm carried by the moving coil A, 

 and to a vertical fibre, F, on the siphon suspension. 



I he siphon is carried on an aluminium carrier to 

 which a single central fibre is attached at the top 

 and two parallel fibres, FF, 0-2 in. apart below. One 

 leg of the siphon (Fig. 2) lies on the axis of the 

 suspension and dips into a small opening in a pipe 

 extending from the ink-pot. This arm goes in be- 

 tween the two vertical fibres, and as the opening 

 in which the siphon dips is only a small one, the ink 

 level remains practically constant, whether the reser- 

 voir is full or not. The siphon turns round on the 

 axis in which the leg lies, and this makes the drag 

 between the moving siphon and the ink very much 

 less than if the siphon cut across the surface of the 

 ink. 



In order to produce an ink line on the paper with- 

 out introducing friction, the siphon must not touch 

 the paper even momentarily, and arrangements have 

 been made to jerk the ink in fine drops on to the 



Trials with this instrument have shown an increase 

 of speed of 30 per cent, on the largest Atlantic cables. 



Thermoelectric Magnifying Relay. 



In this instrument (Fig. 3) the power in the relay 

 circuit is generated by means of five thermo-junctions 

 at different temperatures. The heat is supplied by 

 two little flames, CC, and a very light thermopile, 

 B, is suspended so as to swing in and out of the 

 flames, and is coupled to a moving coil through which 

 the received currents pass. 



The thermopiles consist of alternate junctions of 

 platinum and platinum + 20 per cent, iridium, wires 

 being used of 1 mil diameter. The joints are made 

 by twisting the ends of the two wires together and 

 holding the junctions in a Bunsen flame for a short 

 time. In this way a perfectly good and permanent 

 joint is ensured. The wires are melted on to a fine 

 glass tube about 10 mils in diameter, and one con- 

 nection is brought down inside the tube to the first 

 junction and the other connection comes along the 

 outside of the tube. 



For moving the thermopile in the flames similar 

 arrangements to those just described for the siphon 

 recorder are employed. Under the saddle which 

 carries the thermopile the two silk fibres are stretched, 

 and on to one of these the cross fibre which transmits 



paper. To accomplish this the whole of the siphon 

 suspension is vibrated rapidly up and down between 

 the springs V and K by means of the spring V, 

 which is attached to the vibrator. As the spring V is 

 very weak in comparison with the reed, the vibrations 

 of the latter are not affected by the movements of the 

 spring. To impart a jerk to the siphon a stop, H, is 

 fixed directly under the axis of suspensions, and two 

 little dash-pots, DD, on either side prevent the spring 

 bouncing on the stop. 



The working end of the siphon is ground flat, and 

 an aniline dye with a small proportion of methylated 

 spirit or ordinary red ink is used for recording on the 

 paper. In this way a fine line of very closely spaced 

 dots can be obtained without introducing any appre- 

 ciable drag on the siphon. 



For signalling purposes, the distortion due to the 

 radius of the siphon being only J in. is not at all 

 troublesome as the velocity of the paper moving round 

 the wheel R masks this. 



When the instrument is adjusted to have a natural 

 frequency of 10-5 per second, with a 300-ohm 300-turn 

 coil, a current of 50 microamperes gives a full-sized 

 signal corresponding to a deflection of 01 in. on the 

 paper. Under these conditions the back E.M.F. of 

 the coil is only about one-quarter to one-fifth of that 

 of the ordinary recorder coil. 

 NO. 2265, VOL. 91] 



the movements of the coil to the thermopile is 

 attached. The top and bottom suspensions are of 

 fine phosphor bronze wire and serve as leading-in 

 wires to the thermopile. , 



To supply the heat two little flames are fed by 

 two or three strands of cotton wick with alcohol or 

 methylated spirit. If the wick just protrudes above 

 the opening a small steady flame is produced, and 

 the lamp is provided with adjustments to vary the 

 distance between the flames and the position of both 

 flames relative to the thermopiles. 



Instead of burning directly on the lamp wicks, a 

 simple vapour burner can be fitted which will give 

 good results even with verv impure spirit. This con- 

 sists of a brass cap which is kept hot by a copper 

 wire attached to it at one end, and is heated at the 

 other end by the flame. By altering the amount of 

 wire in the flame the size can be varied. 



An alternative arrangement which gives greater 

 sensitiveness and enables heavier thermopiles to be 

 used is to fix the thermopiles and vary the flames 

 by means of a valve or shutter actuated by the coil 

 movements. 



As the thermopile current depends on the differ- 

 ence of temperature between the junctions a certain 

 time is required to heat the wires. It is found that 

 for cable work, where the frequency seldom exceeds 



