(oZl. 3S3 
 £"w 5cL 
 
 DESCBIPTION 
 
 SIR WILLIAM THOMSON’S 
 
 SIPHON RECORDER, 
 
 AND 
 
 THOMSON AND JENKIN’S 
 
 AUTOMATIC CURB SENDER. 
 
 WITH INSTRUCTIONS FOR THEIR USE. 
 
 BY 
 
 JAMES ALFRED EWING. 
 
 EDINBURGH: 
 
 PRINTED BY NEILL AND COMPANY. 
 
 1876 . 
 
Digitized by the .Internet Archive 
 in 2018 with funding from 
 
 University of Illinois Urbana-Champaign Alternates 
 
 
 https://archive.org/details/descriptionofsirOOewin 
 
% F U 
 
 u%1. V6 2> 
 
 £ vs/ 5 (A. 
 
 THE 
 
 SIPHON RECORDER 
 
 AND 
 
 T* AUTOMATIC CURB SENDER. 
 
 THE SIPHON RECOKDER* 
 
 § 1. Preliminary.— The siphon recorder is an instrument for 
 recording on a moving paper ribbon the right and left movements 
 of a pointer acted upon by the successive positive and negative 
 currents which go to make up telegraphic signals. Its extreme 
 sensitiveness makes it especially suitable for recording the signals 
 received through long submarine lines. 
 
 A coil of fine insulated wire is delicately suspended between 
 the two poles of a powerful electro-magnet, so as to be capable of 
 moving round a vertical axis, and the current from the cable is 
 made to pass through this coil. When a current is passing 
 through the coil it tends to take up a certain position relatively 
 to the poles of the magnet, namely, the position in which the 
 plane of the coil is perpendicular to the line joining the two poles 
 of the magnet. But the coil is suspended so as to hang (when no 
 current is passing) in a position at right angles to this position. 
 Hence, when a current passes, the coil tends to turn round a 
 vertical axis. If the current is positive, the coil turns round (say) 
 in the direction of the hands of a watch, but if the current is 
 negative, the coil turns round in the reverse direction. Hanging 
 from the coil are two weights which resist the tendency to turn 
 round caused by the passage of a current through the coil, and 
 
 * A considerable part of what follows relating to the Siphon Recorder has been 
 taken, with little alteration, from Mr J. C. Cuff’s pamphlet on that instrument, 
 printed in 1873. The description of the recorder and the directions for its use 
 have been enlarged, and now include all the recent improvements. 
 
4 
 
 which serve to bring the coil back to its original position when 
 the current ceases. By means of a system of silk fibres, the 
 motion of the coil is communicated to a pointer which consists of 
 a very fine glass siphon, one end of which dips into an ink holder, 
 while the other vibrates across a paper ribbon in obedience to 
 the movements of the suspended coil. The paper ribbon is made 
 to move past the end of the siphon at a uniform rate. In order 
 to make the ink run through the siphon, the ink is electrified, 
 and the paper ribbon is connected to earth through the framework 
 of the instrument. The ink and paper consequently attract each 
 other, and the ink is spurted out of the end of the siphon on to 
 the paper in a succession of very fine drops. These drops form 
 a continuous straight line along the centre of the paper so long 
 as no current passes through the coil, but when the coil is 
 deflected by the passage of a current, the end of the siphon is 
 deflected with it, and traces a wavy line on the paper, showing 
 the successive deflections to the right or the left of the central 
 position. 
 
 The electrification of the ink is effected by means of an electro¬ 
 static induction machine called the mouse mill, which is driven 
 either by clockwork or by an electro-magnetic arrangement. The 
 same driving power serves to draw along the paper ribbon past 
 the end of the siphon. 
 
 § 2. General Description. —Figs. 1 and 2 show the front 
 and side views respectively of a complete siphon recorder, in 
 which the mouse mill is driven by an electro-magnetic arrange¬ 
 ment. Figs. 3 and 4 show on a larger scale the suspension of the 
 coil and siphon. A A A are three stout wooden pillars which 
 support the framework of the instrument. B is the mouse mill, 
 which is driven by an electro-magnet inside the box D. E (fig. 
 1) is one of the terminals of the coil of this magnet, and imme¬ 
 diately behind E is the other terminal. The drawer F contains 
 lumps of pumice stone moistened with sulphuric acid, by which 
 the atmosphere inside the mouse mill is kept dry. The electri¬ 
 city generated by the revolution of the mouse mill is conducted 
 to the brass rod P and is communicated from the point of P to 
 the plate 0 by convection of the air. The plate 0 is in connec¬ 
 tion with the ink holder K, but K is insulated from the rest of 
 the instrument by the vulcanite rod L. The electrification of K 
 
causes the ink to flow through the siphon t on to the paper 
 which passes along in front of the plate c. 
 
 The motion of the mouse mill is communicated to the paper 
 drum cl by means of the hanging shaft J J, which has a large 
 
6 
 
 wooden pulley at one end, and a lead counterpoise with a series 
 of brass pulleys at the other. A cord passes round a pulley at 
 
 the back of the mouse mill, and round the wooden pulley at the 
 back of the hanging shaft; another cord passes round one or other 
 
7 
 
 of the brass pulleys at the front of the hanging shaft, and round 
 the pulley I, which is on the same axis as the paper drum d. 
 
 M M are the electro-magnets, between the poles of which hangs 
 the signal coil S. They lie on the semicylinders of iron 1ST 1ST, 
 which form at once the bed and armature of the electro-magnets 
 M M. The electrodes of the local battery, which is used to keep 
 the electro-magnets active, are attached to the terminals V x and 
 U 3 , and a wire from the middle of the battery is attached to U 2 . 
 By means of the switch V, full, intermediate, or no battery power 
 may be applied to the electro-magnets M M (see § 7.) The con¬ 
 tacts with the ends of the coils of the electro-magnets M M are 
 made by the springs Y v Y 2 , Y 3 (see § 12.) 
 
 T x and T 2 are terminals connected to the ends of the signal 
 coil S. A quadrant slide connected to T 2 enables a shunt to be 
 inserted, so as to lessen the amount of current passing through the 
 coiL W is a small drawer for holding tools, spare siphons, &c. 
 
 § 3. Motion of the Paper Bibbon. —The paper enters from the 
 right hand side, and is passed under the spring a to keep it 
 stretched. Then over the roller b, whence it passes over a slightly 
 curved guide plate c vertically downwards past the point of the 
 siphon t, till it reaches the driving drum d. It passes a quarter 
 round this drum, and is discharged horizontally to the left. It is 
 pressed upwards against the lower edge of the driving drum d by 
 the roller e. This roller is pressed up against the driving drum 
 by its bearings, these being attached to a brass frame which is 
 pivotted on a stout horizontal pin g. A lever projecting to the 
 right is pulled down by a spiral spring, so that the roller e may be 
 pressed up against the driving drum, and so may grip the paper.. 
 This spring has its lower end drawn down by a crank which is 
 turned by the small handle /. The whole stage carrying the 
 paper rollers, &c., is supported on a triangular plate G G, which 
 can be made to move backwards or forwards only, and which is 
 secured in any position by the screw H. The speed of the paper 
 is varied by shifting the cord in front from one to another of the 
 brass pulleys on the shaft J J,—to a larger pulley if the speed is 
 to be increased, or to a smaller pulley if the speed is to be 
 diminished. The ends of the shaft J J press lightly against two 
 vertical guiding cheeks. The cords have to be of such lengths 
 that the ends of the shaft do not rest on the bottom of the guides,, 
 
8 
 
 and that the wooden pulley does not rub against any part of the 
 
 IV 
 
9 
 
 knot, which is apt to draw. A small variation in the length of 
 either hand does no harm. 
 
 Fig. 5. 
 
 § 4. Suspension of the* Signal Coil and Siphon. —The 
 signal coil and the siphon are arranged upon a framework, a 
 side view of which is shown in fig. 3. Fig. 4. shows a front view 
 of the suspension of the coil. The whole framework is secured 
 in its place between the electro-magnets by the clamping screw 
 C at the back. The coil S is suspended by a silk thread passing 
 over the pulley r. The position of r can he varied by releasing the 
 clamp w. Inside the coil is a stationary piece of soft iron s s, the 
 object of which is to increase the intensity of the magnetic field 
 in which the coil hangs. Two weights hang from the coil, and 
 can slide up and down the guides z. The cords by which these 
 weights hang pass behind a bridge x, whose distance from the 
 coil can be altered by releasing the screw y* jp and q are the 
 terminals of the coil to which wires inside the instrument leading 
 to T 2 and T 2 are fastened. At the right hand top corner of the 
 coil a fine silk fibre v is attached, which leads to a point near the 
 end of a small vertical lever u called the multiplier. Near the 
 top of u another fibre is attached, which leads to t, a projecting 
 point on the left hand side of an aluminum cradle which carries 
 the siphon. This aluminum cradle is fixed to a cross wire on 
 the bridge i i ; by turning the screw l (fig. 1) torsion can be put 
 on this wire. At the hack of the signal coil, and just behind 
 the point of attachment of the fibre v, is another fibre, the other 
 end of which is attached to a spring at o (fig. 3), the position of 
 which can be altered by turning the screw n. By turning n 
 outwards a greater strain is put on the fibre leading from o to the 
 signal coil, and by turning n inwards the strain is lessened. The 
 bridge i i which carries the siphon is secured to the plate m m by 
 
 * See also Appendix A. 
 
10 
 
 the screw j, and is capable of being moved backwards or forwards 
 when j is loosened. By pressing the plate m m up gently, the 
 plate, and with it the bridge carrying the siphon, can be lifted 
 so that the siphon rises out of the inkholder. The groove in the 
 piece of metal between L and m constrains the plate m to rise in 
 such a path that the fibres leading to the coil are not strained by 
 the raising of the plate. K is the ink box into which one end of 
 the siphon dips. 
 
 § 5. The Mouse Mill.— The mouse mill is at once an electro¬ 
 magnetic engine and an electrostatic induction machine. The 
 electro-magnetic arrangements are as follows :—In the box D is 
 a horse-shoe electro-magnet. In the glass case above are ten 
 revolving armatures, which pass the poles of the magnet at the 
 lowest point of their revolution. On the shaft which carries the 
 armatures, and revolving with it, is a cam, which is a ten-sided 
 polygon. (This cam is at the back of the mill, and is not shown 
 in the figure.) On the edge of this cam a contact spring rests, 
 and as the corners of the cam pass under the contact spring they 
 raise it, and so break contact between it and a stop underneath it. 
 When the middle portion of the straight edges of the cam passes, 
 the spring drops and contact is made. This contact determines the 
 passage of the current from a powerful local battery through the 
 coils of the electro-magnet in the box D. The cam is so set that, 
 when the mill revolves, each successive armature is attracted by 
 the electro-magnet so long as the armature is approaching the 
 magnet, but when the armature passes the poles of the magnet 
 contact is broken and the attraction ceases. This makes the axle 
 carrying the armatures revolve. To diminish friction as much as 
 possible, the ends of the axle are pivoted on the edges of friction 
 wheels, which work in cups filled with oil. By means of the 
 quadrant slide X (fig. 2) at the back, extra resistance can be 
 introduced into the circuit of the electro-magnet; this lessens the 
 strength of the current passing through the coils of the magnet, 
 and thus reduces the speed of the mill. The lowest stud of the 
 slide corresponds to the highest speed. 
 
 The electrostatic arrangements in the mouse mill will be under¬ 
 stood by reference to fig. 6. On the revolving axle are fixed ten 
 metal carriers ( c,.c , &c.), insulated from the axle and from each 
 other. They revolve inside two metal plates, I and T, bent so as 
 
11 
 
 to form parts of cylinders (called the inductors), one of which, 
 I', is in contact with the framework of the instrument, and so to 
 earth ; the other, I, is insulated and connected to the rod P (fig. 
 2). Attached to the carriers and in electrical contact with them 
 are ten pins, which, as they revolve, touch successively the four 
 contact springs a , b, a' and V. The inductors and the springs 
 are fixed ; the carriers and the contact pins revolve. The spring 
 a is connected to the inductor I, a is connected to I'; b and V are 
 connected together, but are insulated from the framework. 
 
 Suppose that the inductor I is in a state of very feeble (say) 
 positive charge to begin with, and that the carriers are set revolv¬ 
 ing. The two opposite carriers c and c' are in contact with eacli 
 other while the pins connected to them are passing the springs b 
 and V. During this time, the positive charge on I induces a 
 separation of electricities on c and c', attracting a negative charge 
 to c, and driving off positive electricity to c\ As c and c' revolve, 
 c comes in contact with a!, and its negative charge flows to earth ; 
 c comes in contact with a, and its positive charge goes to increase 
 the previously existing positive charge on the inductor I. This 
 has the effect of increasing the inductive action of I on the 
 succeeding carriers. Thus not only does the charge on I go on 
 increasing, but the rate of its increase goes on increasing too. The 
 action will take place if the potential of the inductor I differs 
 
12 
 
 ever so little from that of the inductor T. If I were negative 
 relatively to T to begin with, then a negative charge would 
 accumulate on I. It would be difficult, if not impossible, to 
 reduce I and I' so exactly to the same potential as to prevent I 
 from getting highly charged after a few turns of the mill. 
 
 The carriers and inductors are coated with paraffin wax to 
 prevent sparks from passing across the air space between 
 them. 
 
 § 6. The Local Batteries. —The batteries employed to keep 
 the electro-magnets M M and that in the mouse mill active are 
 modifications of Daniell’s battery, designed so as to have very little 
 internal resistance, and are called Tray cells. They consist of large 
 fiat wooden trays, lined with lead to make them watertight, and 
 having for the positive metal a sheet of thin copper in the bottom 
 of the tray. In the four corners of the tray four stoneware props 
 are placed, and on the top of them rests a zinc grating which 
 forms the negative metal. The tray is filled up with a solution 
 of sulphate of zinc, and sulphate of copper crystals are dropped 
 in on the bottom plate. The zinc is surrounded with a sheet of 
 stout parchment paper to prevent the diffusion of the sulphate of 
 copper solution from producing copper deposits on the zinc plate. 
 The trays are connected to each other by being piled one on the 
 top of another, so that the copper of one is connected to the zinc 
 of the one below it, by contact of the lead sheathing of the upper 
 one with the four corners of the zinc plate below on which it 
 rests. The advantage of this form of cell is its extremely low 
 internal resistance. It requires constant attention to keep it in 
 efficient order. (See § 8.) 
 
 § 7. Directions for Setting up the Batteries.— Each of the 
 lead trays must first be carefully coated with varnish, over the 
 bottom and sides and edges. Spirit varnish made with shellac 
 or ordinary varnish will do very well. Care should be taken not 
 to varnish over the strip of copper which is soldered to the bottom 
 of each tray. The under surface of each thin copper plate is also 
 to be varnished. When the varnish is dry, place the sheet of 
 copper in the tray with the varnished side down, and, cutting a 
 slit in the centre of the copper sheet, bring through the strip of 
 copper which is soldered to the bottom of the tray; bend the strip 
 and spring it so that its end presses firmly against the upper sur- 
 
13 
 
 face of the copper plate, taking care that both are scraped clean 
 at the place where they touch. 
 
 Each lead tray should have a stout copper wire soldered to it } 
 projecting about three inches from one corner. 
 
 Each zinc is to be protected by a square of parchment paper 
 bent round below it, and folded neatly at the corners and fixed 
 with sealing wax.* Care must be taken that the edge of the paper 
 be generally f inch (and in no place less than £ inch) above the 
 upper level of the bars of the zinc grating. It must be bound 
 firmly to the zinc by twine passing under the parchment paper 
 and tied over the zinc above ; also by a long piece of twine several 
 times round the square. 
 
 To support a pile of trays, take four blocks of wood or stone, 
 each four or five inches square in horizontal dimensions and of 
 any convenient height, and place them on the floor in positions to 
 bear the four corners of a tray. The pile must be so placed as to 
 give ready access to each of its sides. Put a piece of thick sheet 
 gutta-percha, six inches square, on the top of each of the wooden 
 squares, and then lay down the first tray upon them, seeing that 
 it is properly levelled. This is most easily done by pouring a 
 small quantity of water into the cell, and seeing whether it lies 
 evenly over the bottom. Put four stoneware blocks, each about 
 1\ inch cube, in the corners of the tray, on the top of the copper 
 sheet, and put one of the zinc gratings resting with its four corners 
 on these props. Put a solution of sulphate of zinc of specific 
 gravity about IT into the tray,-f* pouring in first between the 
 edge of the tray and the parchment paper, and afterwards filling 
 up to the level of the top of the zinc grating by pouring some of 
 the solution directly on the zinc over the paper. See that the 
 top corners of the zinc, and the bottom corners of the tray to rest 
 upon it, are all properly tinned, scraped clean, and dry. Place a 
 
 * Press the paper against the zinc between finger and thumb on each side of the 
 corner, and draw the bight or bend of the paper diagonally away from the corner ; 
 then fold the bight round the vertical corner of the zinc, and press it against the 
 fiat zinc surface on one side or other of the corner. Secure with sealing wax in 
 the bight, and where one side of it is pressed against the paper on the vertical zinc 
 surface. Then tie the paper round carefully with cord in the manner described in 
 the text. 
 
 t This solution may be prepared by mixing 1 part by weight of the salt to 5 
 parts of water, or 2 lb. of salt to 1 gallon of water. See the table given in 
 Appendix 11. 
 
14 
 
 lead tray resting with its four corners on the upper projecting 
 corners of the zinc. Place four stoneware props in the corners of 
 this second tray, put a second zinc upon them, and fill with solu¬ 
 tion as before. Proceed thus until a pile of from six to ten trays, 
 one over the other, is made and filled with liquid. Solder a stout 
 copper wire to one of the corners of the top zinc, to serve as an 
 electrode. In the same way make as many piles as are required. 
 Leave a space at least one foot broad between each pile and its 
 neighbour. Connect the piles in series, the top zinc of one pile 
 to the lowest lead tray of the next one. 
 
 The crystals of sulphate of copper to be used should be broken 
 into small pieces, and weighed out in quantities of an ounce each. 
 To put the battery in action drop in four ounces to each cell; one 
 ounce separately on each side, distributing it as equally as may 
 be along the space between the stoneware props. In putting in 
 the crystals be careful not to let any fall inside the parchment 
 paper, or in contact with the zinc. As soon as the sulphate of 
 copper is put in, the battery should be allowed to work, either on 
 short circuit or on the circuit which it is intended for. 
 
 From three to six cells are required to drive the mouse mill. 
 The number to be applied to the magnets M M varies with the 
 circumstances of the case; it may be anything from one to twenty, 
 or even more. Separate sets of cells should be used for the 
 magnets and for the mill. If the same set is used for both,— 
 that is to say, if the coils of the magnets are to be looked on as 
 a shunt applied to the battery which is driving the mill (or vice 
 versa ),—then the whole number of cells in use should be applied 
 to each circuit. The practice of using part of the battery em¬ 
 ployed to work the magnets to work the mill also, is very objec¬ 
 tionable. A wire from the zinc pole of the pile or piles intended 
 for the magnets comes to the terminal (fig. 2), from the copper 
 pole to U 3 , and a wire from an intermediate tray in the series 
 to U 2 . This gives the means of applying full or intermediate 
 battery power to the magnets by means of the switch Y. 
 
 § 8. Maintenance of the Batteries. —When the tray cells are 
 in use, the sulphate of copper is decomposed, copper is deposited 
 on the copper plate, and the zinc plate is consumed; sulphate 
 of zinc is formed, which strengthens the solution at the top of 
 the cells. It is therefore necessary to supply more crystals of 
 
15 
 
 sulphate of copper, and also to draw off the sulphate of zinc solu-* 
 tion from the top of the cell when it becomes too dense, and to 
 supply its place with fresh water. When a cell is in constant use, 
 it is desirable to draw off a little of the liquid daily. The drawing 
 off is effected by means of a siphon, the shorter end of which is 
 dipped into the cell between the edge of the tray and the zinc 
 plate so as to be just below the lowest level of the zinc, while the 
 longer end stands out over a convenient vessel to receive the 
 liquid. Water is to be poured into the space above the zinc 
 grating by means of a funnel ending in a bent tube. The specific 
 gravity should be frequently tested by a hydrometer or by specific 
 gravity beads, and the quantity drawn off should be regulated so 
 as to keep the specific gravity of the liquid (taken from near the 
 surface of the cell) at about F24, or not greater than 1*3, and not 
 less than IT2. Fresh crystals of sulphate of copper are to be 
 dropped in along the four sides of the cell, one ounce at a time 
 along each side. It is easy to see when fresh sulphate is required 
 by observing when the blue colour of the liquid at the bottom of 
 the cell disappears. When cells are in active use they generally 
 require new sulphate almost daily. A cell, or pile of cells, should 
 never be left out of use for any length of time with crystals or 
 blue solution in it; before being left it should always be short- 
 circuited until the liquid becomes clear and colourless. If suffi¬ 
 cient care is not taken to remove the sulphate of zinc solution as 
 it becomes too dense, crystals of sulphate of zinc will accumulate 
 round the edges of the cell. These ought to be scraped off. 
 When the batteries are not properly attended to, these crystals 
 will often accumulate in such quantities as to connect the zinc 
 tray to the lead casing, and so to short-circuit the cell. The 
 battery should be frequently tested in the manner described farther 
 on (§§ 15, 16, and 17). 
 
 § 9. Adjustment of the Mouse Mill.— If the Mill does not run 
 fast enough. — 1st, Alter the quadrant slide X (fig. 2) if not already 
 on the stud of highest speed ; 2 d, Look well to the adjustment of 
 the contact-breaking spring at the back. 3 d, See that the cups 
 are well supplied with oil in which the friction rollers work that 
 bear the ends of the main shaft; 4:th, If it still goes too slowly 
 more battery power must be employed. 
 
 The electro-magnetic contact breaker at the back consists of 
 
16 
 
 two platinum points, one of which is fixed, whilst the other is 
 carried up and down by a steel spring which is raised at intervals 
 by the cam. If these platinum points are separated too much, 
 the electro-magnet will not act on each carrier in succession so 
 long a time as it ought, and diminished efficiency is the result. 
 Again, if the points remain in contact too long, the electro¬ 
 magnet will continue to act on each carrier after it has passed 
 its poles, and thus tend powerfully to retard its progress. Hence 
 the adjustment of this spring, by turning the screw which raises 
 or depresses the lower contact, is most important; but when once 
 set right it will remain so for a long time. 
 
 If the ink is insufficiently electrified when the mill is running 
 properly, and generating electricity—1 st, Alter the distance of 
 the rod P from the plate 0. Generally about two or three inches 
 is found to be the best distance; but this depends on the state of 
 the atmosphere, &c.; 2 d, See that the insulation is nowhere 
 impaired by dust. If the silk fibre attached to the siphon has 
 any dust upon it, a camel’s hair brush or feather will remove it. 
 The vulcanite rod L, in particular, must be kept free from dust, 
 and also the metal work near it. It is sometimes necessary to 
 clean the vulcanite rod L by washing it with warm water and a 
 little soap, and then drying it carefully.* The paraffin tube, 
 which insulates the rod leading from the insulated inductor to the 
 rod P, will also require occasional cleaning. 
 
 When the mouse mill fails to generate electricity , although other¬ 
 wise running well, it will be necessary--ls£, To take off the top 
 and carefully remove the insulated inductor, and see that its 
 insulation and that of the carriers is perfect; 2 d, Make sure that 
 the four springs make contact properly with the brass pins as 
 they come round in succession. Every provision is made for the 
 adjustment of these springs, or for the insertion of new ones, 
 which is easily effected. Several sets of spare electro-static 
 springs, and one spare electro-magnetic contact spring for the 
 driving circuit are sent with each instrument; 3d, Supply the 
 drawer F with sulphuric acid by pouring a few drops on each 
 piece of pumice. The strongest commercial sulphuric acid should 
 
 * When other means of getting L to insulate properly fail, it should be painted 
 with varnish, prepared by dissolving sealing wax in warm spirit. This varnish 
 should be laid on while hot. 
 
17 
 
 be employed for this purpose, and should be prepared by boiling 
 it for half an hour in a Florence flask along with a little sand to 
 facilitate ebullition, and a few crystals of sulphate of ammonia. 
 The flask should be supported by a retort stand over a spirit 
 lamp or other convenient source of heat, beneath which is placed 
 a pan of cold ashes or other arrangement to prevent any injury 
 being done in case the flask breaks.* 
 
 If too much electricity is generated, the siphon will not mark 
 well, and will sometimes vibrate laterally unless some is drawn 
 off by a pointer in connection with the outside of the case 
 and directed towards the rod P. If the instrument is not pro¬ 
 vided with such a pointer the want can be easily supplied by 
 attaching a piece of wire about 6 inches long to the screw handle 
 of the drawer F. The lateral vibration of the siphon may be 
 further prevented by enclosing the paper (while running) in a box 
 containing aqueous vapour, or (when necessary) by using prepared 
 paper. The paper may be prepared by soaking it in a solution of 
 two parts of nitrate of ammonia in 100 parts of water, and then 
 drying and re-rolling it. This salt, being deliquescent, keeps 
 the paper slightly damp by absorbing moisture from the 
 atmosphere, and by thus increasing the conducting power of the 
 paper, prevents the lateral vibrations of the siphon. 
 
 If sparks are seen passing between the inductors and carriers 
 at any place, they will be due to a defect in the coating of 
 paraffin wax. Such a defect can be easily repaired by a little hot 
 melted paraffin laid on with a brush. 
 
 If sparks are seen at the contact of the revolving cam at the 
 back and the spring which rests on it, they will be due to a defect 
 of insulation of the battery wire or electro-magnet coil, which 
 ought to be remedied without delay. 
 
 § 10. Adjustment of tiie Taper.— To release the paper, turn 
 the handle / in a direction opposite to the motion of the hands of 
 a watch. Thus the roller e is allowed to fall about an eighth of an 
 inch, and the paper is quite free, so that it may be slipped out 
 with ease, and, though the driving drum d revolves, the paper is 
 
 * A good plan of keeping the mouse mill dry, in a cold and damp climate, is to 
 take out the drawer F, and put in its place a coil, or bend of lead tube, through 
 which a current of hot water or steam is kept passing from a small tin boiler, kept 
 hot by a gas jet or by the llamc of a candle. 
 
 It 
 
13 
 
 not drawn along. To clutch the paper against the driving drum, 
 turn the handle f in the reverse direction. 
 
 To regulate the distance of the paper from the point of the siphon, 
 turn the milled head h. 
 
 To bring the line made by the siphon to the middle of the paper, 
 loosen the clamping screw H, when the whole paper stage G G 
 can be easily moved backwards or forwards to the desired position. 
 
 To make the paper run evenly between the rollers d and e, turn 
 the small screw k, which will either elevate or depress the nearer 
 end of the roller b until all works true. 
 
 To alter the speed of the paper, shift the band in front from one 
 pulley to another. If necessary, alter the speed of the mill. 
 
 § 11. Adjustment of the Siphon and Signal Coil.— A large 
 number of fine glass tubes for siphons is provided with each 
 
 instrument.* The siphons are made from 
 them as follows :—Take one of the small 
 pieces of tube and present it to the heated 
 atmosphere surrounding any small flame, such 
 as that of a match, in a convenient position 
 to allow one part to drop by its own weight 
 when the tube softens. The tube should be 
 brought into contact with the lower, not the 
 upper, edge of the flame. It can thus be bent 
 into the proper shape, the long limb being about 
 two and a half inches in length. The point 
 should be bent so as to make an angle of about 
 130° with the longer limb. Figure 7 shews a 
 properly made siphon, drawn to full size. In 
 making the siphon care must be taken that 
 the bends are not over-heated, so as to cause 
 the tube to collapse and diminish its bore. 
 Any narrowness in the bore at the bends is 
 easily detected by filling the siphon vfith ink. "When an ordi- 
 
 * Should these prepared tubes not he at hand, they can be easily made thus :— 
 Take a piece ol soft glass tube, about one quarter of an inch in diameter, the 
 thickness of its wall being about one-sixth of the whole diameter. Soften about 
 one iDch near the middle in an ordinary gas flame, or, better still, over a Bunsen 
 burner, slowly turning it round the whole time. When sufficiently softened, 
 remove it from the flame and pull the ends apart until the tube is so drawn out 
 that it is of the desired diameter. Break the flue tube thus produced into pieces 
 about four inches long. 
 
19 
 
 narily fine siphon is used, the ends may be broken by the fingers 
 or otherwise, so as to be of the proper length. On short circuits, 
 where great sensitiveness is not required, a thick siphon may be 
 used, and the ink can be made to run well without electrification. 
 In this case the point of the siphon should be nicked with a 
 glass-cutter’s knife, when it will break off flush. It may then 
 be ground parallel to the paper on a small corundum grindstone, 
 and welted by being held for an instant in a flame, so as to pro¬ 
 duce a perfectly smooth point. 
 
 The siphon is readily secured in position, on the aluminium 
 cradle which carries it, by a little bees’-wax. 
 
 To attach or remove a siphon, raise the piece m m (fig. 3) 
 which carries the siphon bridge i i, and is so guided by the curved 
 V groove above as not to disturb the signal coil. When the siphon 
 is clear of the ink bottle, apply a hot wire to the back of the 
 aluminum cradle; this will melt the wax, and the new siphon can 
 at once be stuck on or the old one removed. 
 
 To adjust the siphon relatively to the signal coil. — 1st , The signal 
 coil must hang freely and evenly about the soft iron magnetic 
 inductor s s (fig. 4), and must not touch it at any point. 
 
 2 d, All the fibres must be sufficiently strained. 
 
 3d, The normal position of the siphon must be vertical. 
 
 To effect the first of these adjustments, the coil is raised or 
 lowered by turning the screw r with a square-pointed key. It is 
 moved backwards, forwards, to the right, or to the left, by easing 
 the screw w, shifting as desired, and then reclamping. 
 
 To attain the second of the above conditions in connection 
 with the first, the three screws n,j, and l (figs. 1 and 3), must be 
 manipulated. 
 
 By loosening j and sliding the bridge i i backwards or forwards, 
 the first approximation is obtained. Then the screws n and l 
 must each be turned so that the steel spring connected with n, 
 and the torsional elasticity of the wire attached to l may re-act 
 on each other, so as to make the signal coil hang in a line with 
 the poles of the magnet. 
 
 Lastly, to make the siphon hang vertically, the screw j will 
 probably require to be undone, the bridge i i slightly shifted, and 
 another touch given to l. This last adjustment is the only one 
 required in general use. 
 
20 
 
 See that the siphon does not stick on account of the shorter 
 end being too long, and touching the bottom of the ink box. 
 
 The most suitable ink for the recorder is the best soluble aniline 
 blue. Put as much of the crystals as will stand on the small 
 blade of a pen knife into a 3 or 4 oz. bottle of water, and shake 
 them up, and you- will immediately have a perfectly fluid ink of a 
 deep blue colour. This ink is superior to any ordinary kind, 
 because it does not thicken or precipitate, and, in the form of 
 crystals, is far more portable. 
 
 § 12. General Directions. —The size of the signals may be 
 varied by means of the shunt attached to T 2 (fig. 2). 
 
 The sensitiveness of the instrument may be increased in several 
 ways:— 
 
 1st, By altering the contact springs of the electro-magnets. 
 When the contact springs are arranged as shewn in Figs. 1 and 2, 
 the magnet coils are connected up in series. If the spring Y A 
 be shifted over to the stud Z, the spring Y 3 remaining dis¬ 
 connected, the right hand coil only is in circuit. This gives 
 a low degree of sensibility. But if, when Y A is connected to Z, 
 the spring Y 3 be put upon the stud to the left on which Y 2 is 
 shown as resting in fig. 2, then both coils are in circuit, and are 
 joined up in multiple arc. Except with a battery of exceptionally 
 high resistance, the last arrangement is the most sensitive of all 
 three. Each of the coils has a resistance of about 8 ohms; con¬ 
 sequently, when the first arrangement is adopted, the total resist¬ 
 ance is 16 ohms; with the second arrangement, 8 ohms ; and with 
 the third arrangement, 4 ohms. 
 
 2d, The sensibility of the instrument may be increased by 
 lowering the bridge x, fig. 3 (by loosening the clamp y ), so as to 
 lengthen the distance between it and the signal coil. 
 
 3 d, By using light weights. The only limit to this is that the 
 weights must be sufficiently heavy to bring the coil (after being 
 deflected) back to its normal position so quickly as to leave no 
 sensible interval between the cessation of the current and the 
 corresponding return of the coil. Since the first introduction of 
 the recorder it has been found that the weights may be much 
 lightened. Weights of seven-eighths of an ounce each are found 
 to give sufficient directive force. 
 
 4 tli, The sensibility may be greatly increased by bringing the 
 
21 
 
 two cords by which the weights hang from the coil close together. 
 The closer these threads are to one another the less will be the 
 directive force on the coil, and the greater will be the sensibility. 
 A good plan of bringing them very close together is to tie a thread 
 round them just below their points of attachment to the coil. 
 They may thus be brought so near each other as to touch. They 
 should then be brought equally close to one another where they 
 press on the bridge x, so that they may hang parallel between the 
 coil and the bridge. This mode of increasing the sensibility of the 
 instrument is recommended in preference to the 3 cl method given 
 above, because when the weights are much lightened the stability 
 of the coil is lessened, and it is liable to be affected by any un¬ 
 steadiness of the instrument or of the table; while by bringing 
 together the suspending cords of the weights, the directive force 
 may be reduced to any extent without taking away from the 
 stability of the coil. 
 
 5th, The leverage of the multiplier u can be increased by 
 lowering the point of attachment of the fibre leading to the coil, 
 or by raising the point of attachment of the fibre leading to the 
 siphon. 
 
 On short circuits the multiplier u can be dispensed with, and 
 the coil connected directly to the siphon by a single fibre. The 
 multiplier is removed by taking out the two screws (shown in 
 fig. 4, just below w) which secure the frame which carries the 
 multiplier. 
 
 When the instrument is to be out of use for (say) some hours, 
 the batteiy should be disconnected from the electro-magnets by 
 turning the switch V. The mouse mill should be stopped by turning 
 X (fig..2) down so as not to touch any of the studs. The siphon 
 should be lifted out of the ink bottle by raising m m, and the ink 
 should be sucked out of the siphon so as to prevent it from drying 
 in the siphon and causing it to clog. When the siphon is being 
 sucked care must be taken not to strain the fibres. 
 
 When the instrument is to be out of use for a shorter time, the 
 cord which drives the paper drum may be placed on the pulley 
 giving the lowest speed, so as to waste as little of the paper as 
 possible; or the paper may be entirely stopped by turning the 
 handle/, when the ink from the siphon will accumulate on it in 
 
22 
 
 a large drop. The mill should never be stopped without the 
 siphon being raised and sucked. 
 
 When the instrument room is on the ground floor, a brick or 
 stone pillar should be built for the recorder to stand upon. The 
 top of this should be about nine inches below the level of the table. 
 The upper part of the recorder then projects through a large 
 square hole in the table. This arrangement prevents the recorder 
 from being shaken by any movements of the table, and it brings 
 the end of the siphon dow’n to a convenient level. When a pillar 
 rising from the ground cannot be used, the recorder should stand 
 on a stout bracket projecting from a w’all (not a partition) at the 
 same distance below the level of the table. The instrument should 
 be placed so as to be well lighted from the left. 
 
 § 13. Connections for Sending and Receiving. —In order 
 that the signals sent from a station may be recorded on the re¬ 
 ceiving instrument at that station, it is necessary to send a portion 
 of the current through the coil of the recorder at the sending station. 
 The portion of the current wdiich passes through the coil of the 
 recorder at the sending station may either rejoin the remainder 
 of the current before it enters the cable, or may be allowed to 
 go to earth at the sending station. These two possible systems 
 allow of the adoption of either of tw r o arrangements of the connec¬ 
 tions. There are several plans by which each of these two 
 systems may be carried out. Fig. 8 show’s an arrangement of the 
 connections in which no portion of the sending current goes to 
 earth at the sending station. 
 
 T b To, and T 3 , are the three terminals on the left hand side of 
 tire recorder. On the uppermost of these (T 3 ) there is a quadrant 
 slide, by means of wdiich small resistances, varying from 8 ohms 
 dowmvards, can be inserted between T 3 and T 2 . T 2 and T x are 
 connected to the tw’o ends of the signal coil S. Attached to T 2 is 
 another quadrant slide, by means of wdiich resistances, varying 
 from 500 ohms upwards, can be inserted between T 2 and T 1? so as 
 to form a shunt to the coil. When the sliding piece connected to 
 T 2 is not in contact with any metallic stud, the only connection 
 between T 2 and T x is that given by the coil itself—in other words, 
 the coil is not shunted at all. T 2 is connected to the cable or to 
 the condensers, if any are used. The current from the key enters 
 the recorder at the sending station at T l and T 3 simultaneously. 
 
o 
 
 r 
 
 
 
 V 
 
 *8 
 
 (. 
 
 o 
 
 a 
 
 
 Sending Station 
 
24 
 
 By far the greater part reaches T., by way of T 3 , through the low 
 resistance in the upper quadrant slide. A small portion reaches 
 T 2 from T b passing partly through the signal coil, and partly 
 through the shunt between T l and T 2 , should there be one. The 
 joint resistance between T 1 and T 2 of the coil and shunt is very 
 much greater than the resistance between T 3 and T 2 , and hence 
 only a very small portion of the current goes to T 2 by way of T r 
 Hence only a very small portion of the current passes through the 
 coil. 
 
 The switch shown in fig. 8 consists of a metallic lever moving 
 about a horizontal axis. Its centre is connected to T x . When the 
 switch is set for sending, K is connected to S, which is connected 
 to T 3 ; therefore the key is connected both to Tj and T 3 , as described 
 above. To set the switch for receiving, the handle is raised. T 1 is 
 thus connected to earth, and S is left insulated. Then the current 
 from the distant station entering the recorder at T 2 can find no 
 outlet by way of T 3 , but must pass from T 2 to T x through the 
 coil and shunt. The contact piece D allows the cable to be dis¬ 
 charged to earth during the movement of the switch from “send” 
 to “receive.” The lever ought to make contact with D before it 
 breaks contact with S, so that the cable may be for an instant con¬ 
 nected to earth through no other resistance than the very small 
 one between T 2 and T 3 . 
 
 It will be seen that the batteries are reversed at the two 
 stations, or, what amounts to the same thing, the positions of 
 earth and line are different on the two keys. This is necessary 
 in order that the sending and receiving signals may be recorded 
 in the same direction, when the arrangement shown in fig. 8 is 
 used. 
 
 § 14. Second Method of Arranging Connections. —The 
 method shown in fig. 8 wastes none of the current at the sending 
 station. The portion of the current which passes through the 
 coil at the sending station rejoins the main body at T 2 . Fig. 9 
 shows an arrangement in which the portion of the current which 
 records the signals at the sending station is allowed to go to earth. 
 At the sending end the contacts numbered 2 and 3 are made, and 
 No. 1 is broken. At the receiving end No. 1 is made, and Nos. 2 
 and 3 broken. The current from the key enters the recorder 
 simultaneously at Tj and T 3 , which are therefore at the same 
 
25 
 
 
 potential. Between T. 2 and the earth there is a high resistance— 
 say of 5000 ohms—which, however, may be varied to suit 
 different cases. Since the very low resistance between T 3 and T., 
 is an exceedingly small fraction of the high resistance that there 
 is between T.> and earth, T 2 will be at a potential very little lower 
 than that of T s . But T 2 is at the same potential as T3, conse- 
 
 Recorder 
 
 quently T 2 is at a potential very little lower than that of T r 
 There will therefore be a feeble current from to T, through the 
 signal coil. 
 
 To receive, the contacts Nos. 2 and 3 are broken, and No. 1 is 
 made. T 2 is thus put in direct connection with the earth, and 
 the received current enters at T 1} passes through the coil, and goes 
 
26 
 
 to earth at T 2 . In this arrangement the received and sent currents, 
 when of the same name, pass through the signal coil in the same 
 direction. There is, therefore, no need to reverse the batteries at 
 the two ends as in the former arrangement. The switch must be 
 so designed that when it is turned over to “ send/’ contact No. 2 
 is first made, then No. 1 broken, and lastly, No. 3 made; and when 
 turned over to “receive,” No. 3 must first be broken, then No. 
 1 made, and lastly, No. 2 broken. This order preserves the coil 
 from receiving any violent shock by the discharge of the cable. 
 
 The sending signals recorded by means of the second of the 
 above arrangements are very much more legible than those 
 obtained by the first. The latter are much more abrupt and 
 jerky. This is especially the case when condensers are used, or 
 when the automatic transmitter is employed (see § 40). 
 
 § 15. Tests of the Batteries.— The tray cells ought to be 
 tested frequently, in order that any undue rise in internal resist¬ 
 ance or defect in electromotive force in any one of them may be 
 detected and remedied. The whole pile of cells in circuit should 
 first be tested, both for resistance and electromotive force, and 
 then each single cell should be tested. If the resistance of any 
 single cell is much greater than the total resistance of the pile 
 divided by the number of cells in the pile, or if the electromotive 
 force of any single cell is much less than the total electromotive 
 force divided by the number of cells, then the defective cell 
 should be at once short circuited or removed, because its presence 
 in the circuit interferes with the efficiency of the battery. 
 
 The tests of the battery may be very conveniently made by 
 means of a mirror galvanometer, or of a common tangent gal¬ 
 vanometer, or of a quadrant electrometer. The wires used to 
 lead from the battery to the testing table should be thick, so as to 
 have no sensible resistance. It is convenient to have a box of 
 resistance coils, the amount of which can be easily varied. A coil 
 of stout cotton or silk-covered copper wire, having a known resist¬ 
 ance of not less than one-tenth ohm, and not more than one ohm, 
 should also be prepared; this should be made of thick wire so as 
 not to get much heated by the passage of a current during the test. 
 This coil (which for brevity will be called the “battery shunt”) 
 should be provided with thick flexible electrodes, so as to be suit¬ 
 able for direct application to each cell. 
 
27 
 
 § 16. To find the Resistance of a Cell or Pile of Cells.— 
 Make a circuit consisting of the cell, the (tangent or mirror) gal¬ 
 vanometer, and a high resistance,—such that the resistance of the 
 cell itself is insignificant compared with the resistance in the circuit 
 external to the cell. If the galvanometer has a high resistance, say 
 of at least 3000 ohms, it is unnecessary to insert any additional 
 resistance, for the resistance of the galvanometer alone will then he 
 such that the circuit will fulfil the condition of having the resist¬ 
 ance external to the cell immensely greater than the resistance in 
 the cell itself. Observe the deflection given by the galvanometer, 
 and let it be called D. Next shunt the cell, by connecting directly 
 to its two terminals the terminals of the battery shunt coil men¬ 
 tioned in the preceding paragraph, and allow the rest of the circuit 
 to remain unchanged. Observe the deflection now obtained, and 
 call it d. If we call the resistance of the battery shunt S, then 
 R, the resistance of the cell, will be found by the following 
 formula:— 
 
 R = S 
 
 I) - d 
 
 d 
 
 This formula holds good only when the resistance external to the 
 cell is very great compared with that of the cell itself. It is 
 therefore necessary, when the external resistance is that of the 
 galvanometer alone, that the galvanometer should not be shunted— 
 the deflection may be brought within reasonable limits by apply¬ 
 ing strong directing magnets. If, however, a sufficient extra 
 resistance be put into the circuit, there is no objection to the use 
 of a shunt on the galvanometer. It should, however, be borne in 
 mind that the above formula is never more than approximately 
 true, and that it is more and more nearly true the nearer the 
 ratio of the external to the internal resistance approaches to 
 infinity. Hence the higher the external resistance is, the more 
 near will the result given by this formula be to the truth. This 
 test is not applicable to a battery of high resistance, but it is 
 by far the best test for tray cells, or even for some of the more 
 ordinary forms of batteries. When a quadrant electrometer can 
 be used, the test is exceedingly simple. Observe D, the deflection 
 obtained when the two poles of the battery are connected to the 
 two electrodes of the electrometer. Next observe d, the deflection 
 obtained by connecting the poles of the battery to the electro- 
 
28 
 
 meter, the battery being shunted through the coil whose resistance 
 is S. Then as before— 
 
 When the electrometer is used this formula is rigidly accurate,* 
 and the test is applicable to a battery of any resistance whatever. 
 
 A convenient modification of this test is to use a box of adjust¬ 
 able resistance coils as the battery shunt, and so alter S until the 
 second deflection d is exactly half the first deflection D. Then It 
 will be equal to S. 
 
 In observing d care must be taken not to allow the current to 
 run through the shunt coil for any considerable length of time, as 
 the coil becomes rapidly heated and so alters in resistance. In 
 order that the rate of heating should be as small as possible, the 
 shunt coil should be made of thick wire. If the deflections I) 
 and d are so nearly equal that the difference between them is 
 small compared with either, then the resistance of the shunt is too 
 great, and a shunt of less resistance ought to be used. 
 
 The resistance of the tray cells depends, of course, upon their 
 size. They have seldom less internal resistance than OT ohm, and 
 should never have more than 0 5 ohm. It is very important that 
 all the cells in a circuit should have approximately the same 
 resistance. 
 
 § 17. To Test the Electromotive Force of a Battery.— The 
 electromotive force of each of the tray cells should be tested occa¬ 
 sionally by comparing it with the electromotive force of a standard 
 cell of a constant kind. The standard cell may be a Minotti’s or 
 any other form of Daniell’s element, and it should be set apart and 
 not used for any purpose except for testing, so that its electro¬ 
 motive force may remain fairly constant. The method of testing 
 is as follows :—Join up the battery to be tested in circuit with a 
 high resistance and a galvanometer, and note the deflection D, 
 just as in the previous test. If the resistance of the galvanometer 
 is of itself so great that the resistance of the cell is insignificant 
 as compared with it, then it will be unnecessary to introduce any 
 other resistance into the circuit. Next substitute the standard 
 cell for the battery to be tested, keeping the rest of the circuit 
 
 * Except for a slight change in the electromotive force of the cell during the test, 
 due to polarization. 
 
29 
 
 unchanged, and note the deflection D' given by it. In this case 
 also the resistance external to the cell should be exceedingly 
 large as compared with that of the cell itself. Then 
 
 EMF of battery = EMF of standard cell x 
 
 In this way the electromotive force of any given battery can be 
 expressed in terms of that of the standard cell, and it is not neces¬ 
 sary for practical purposes to know what the electromotive force 
 of the standard cell is in absolute units, so long as it can be relied 
 on to remain constant. If it is a Daniell’s cell in good condition, 
 its electromotive force will be almost exactly one volt. 
 
 In the above formula it is assumed that the resistances both of 
 the battery to be tested and of the standard cell are insignificant 
 as compared with the other resistances in the circuit which remain 
 unchanged during the experiment. If, however, the resistances of 
 the battery and standard cell were relatively considerable, the 
 formula would require to be modified as follows : Let R 0 be the 
 sum of the external resistances in the circuit, which is the same 
 both for D and D'. Let r be the resistance of the battery to be 
 tested, and let r' be the resistance of the standard cell. Then 
 
 EMF of battery = EMF of standard cell x 
 
 If the quadrant electrometer is used, the test becomes exceedingly 
 simple. Let the deflection D be observed when the poles of the 
 given battery are applied to the terminals of the electrometer, and 
 let the deflection D' be observed when the standard cell is applied, 
 no resistance being used in either case. Then 
 
 EMF of battery = EMF of standard cell x 
 
 If the electromotive force of any one cell is observed to fall 
 below the average, or much below that of a Daniell’s cell in good 
 condition, the cell either requires to be refreshed with crystals of 
 sulphate of copper, or has become foul by the deposit of copper 
 upon the zinc plate. When the last happens, the cell should be 
 taken down and cleaned. When only one cell in an otherwise 
 good pile becomes foul, and it is desired to avoid taking down the 
 pile, the foul cell should be short-circuited, and so put out of 
 action. 
 
30 
 
 THE AUTOMATIC CURB SENDER. 
 
 § 18. The object of the automatic curb sender is to diminish the 
 retardation of signals in long cables caused by inductive embar¬ 
 rassment. This is effected by making each signal be produced, 
 not simply by one current, as in ordinary sending, but by two 
 currents, the second of which is opposite in name to and of some¬ 
 what shorter duration than the first. The number of currents is 
 not necessarily limited to two, but for the present purpose it will 
 suffice to consider the case of a signal produced by two currents 
 only. 
 
 § 19. In the Proceedings of the Royal Society for 1855, Sir 
 William Thomson showed how the effect at the distant end 
 
 of a cable, caused by the application of a battery at one end, 
 could be calculated and represented graphically in what is 
 called, the “ curve of arrival.” After contact is first made at 
 the sending end between the cable and one pole of the battery 
 (the other pole being to earth), a certain interval of time elapses 
 before any effect is felt at the distant end. This interval of time 
 is denoted by the letter a* After the interval of time a has 
 passed, a current begins to issue from the cable at the receiving 
 end, and increases in strength very rapidly. After a further 
 interval of 4a or after a period of 5a from the first application of 
 the battery, it attains about half its maximum strength, and there 
 
 * Sir William Thomson shows that the value of a in seconds is 
 
 where 
 
 £and c are the values in electrostatic units of the resistance and capacity per unit 
 of length, and l is the length. A consideration of the dimensions of the two 
 systems of units shows that the formula remains unchanged when k and c are 
 expressed in electromagnetic units. Since 1 ohm = 10 9 electromagnetic units of 
 resistance, and 1 microfarad = 10 —15 electromagnetic units of capacity, we have 
 
 a = 
 
 RCZ 2 
 
 10Sr 2 
 
 where R is the resistance per knot in ohms, C the capacity per knot in microfarads, 
 and l the length in knots. Thus a in seconds = '000000029 RCZ 2 . If R' and C' be 
 the total resistance and capacity respectively, a ~ '000000029 R / C / . For the Direct 
 United States Cable of 1875 (2420 knots), whose total resistance is 6980 ohms, and 
 capacity 991 microfarads, a would be '202 seconds ; for the artificial cable in the Phy¬ 
 sical Laboratory of Glasgow University, a = '144 seconds ; for the French Atlantic 
 Cable, a = *245 seconds ; for the Suez-Aden Cable, a = '233 seconds. Sir William 
 Thomson’s theoretical results were experimentally verified by Professor Fleeming 
 Jenkin (Phil. Trans. 1862). For fuller information on the speed of signalling, see 
 Jenkin’s Electricity and Magnetism , pp. 327-333, and Phil. Mag., June 1865. 
 
31 
 
 is very little sensible increase in strength after a time equal to 
 10 a has elapsed. The curve of arrival is drawn by taking dis¬ 
 tances along ox (fig. 10) to represent intervals of time, and 
 distances along oy to represent strengths of current. Curve 
 
 No. I. shows the gradual increase in strength of the received 
 current at one end of a cable when the battery is applied to and 
 kept in contact with the other end. For a distance correspond¬ 
 ing to the interval of time a the curve does not sensibly deviate 
 from the straight line o x; in other words, no effect is observ¬ 
 able at the receiving end during this time. 
 
 If now, instead of being continuously applied to the battery at 
 the sending end, the cable had been applied to it during a short 
 interval of time, and then disconnected from the battery and con¬ 
 nected to earth, the curve of arrival would be of the form shown 
 by curve No. II.* Curve No. II. shows the effect of applying the 
 
 * The falling curve is of exactly the same form as the curve of arrival, and the 
 actual curve, showing the arrival of an impulse, is obtained by superposing tlie 
 one upon the other. Thus the distances between Curves I. and II. are equal to the 
 ordinates of Curve I., if the former are taken as far from the point A as the latter 
 are taken from the point at which Curve I. leaves the line o x. 
 
battery during a length of time equal to 4a, and then putting the 
 cable to earth. It will be seen that a current gradually dimin¬ 
 ishing in strength continues to flow out of the cable at the 
 distant end for a considerable time after the battery has been 
 disconnected. This continued discharge is what gives rise to the 
 difficulty experienced in reading the signals sent through long 
 cables. 
 
 § 20. The principle of “ curb ” sending is to check this discharge 
 by sending into the cable a second current which will neutralise 
 the bad effects of the first. Thus let the cable, instead of being 
 put to earth after having been in contact with one pole of the 
 battery during the time 4a, be put in contact with the opposite pole 
 of the same battery for an interval of time equal to 3 a, and then 
 be put to earth. The second contact would, if it had taken place 
 alone, have produced a current at the distant end represented by 
 Curve No. III. The joint effect of the two opposite currents— 
 the first for an interval of time 4 a, and the second immediately 
 following it, and lasting for an interval of time 3 a —will be to 
 produce a received current represented by Curve No. IV., whose 
 ordinates are the algebraic sums of the ordinates of II. and III. 
 Curve No. IV. thus represents the curve of arrival given by a 
 signal current of duration 4a, followed by an opposite or curb 
 current of duration 3a. 
 
 § 21. The curve of arrival for any current or combination of 
 currents is actually traced on paper by the siphon recorder. Since 
 the deflection of the siphon is sensibly proportional to the strength 
 of the current at any instant, its deflection will correspond to the 
 distances measured in the direction of o Y, and since the paper 
 moves at a uniform speed, and in a direction at right angles to 
 the direction in which the siphon is deflected, the distances it runs 
 will measure intervals of time, and will correspond to distances 
 measured along o x. Hence the curve traced by the point of the 
 siphon will represent the curve of arrival, and all theoretical con¬ 
 siderations respecting the curve of arrival will apply equally to 
 the practical form of the curve drawn on the paper slip. 
 
 The curve of arrival, traced according to the considerations in 
 §19 and § 20, is the curve of arrival in the case where the line is 
 worked directly, without condensers at either end. The effect of 
 introducing condensers is to convert what was formerly a con- 
 
33 
 
 tinuous current into an impulse. The curve produced at the 
 receiving end by the application and continued contact of a 
 battery at the sending end, would no longer be of the form of 
 Curve I. fig. 10, but would soon reach a maximum, after which it 
 would fall back towards the zero line. It will be readily seen 
 that this would of itself cause something of a curbing effect on 
 signals, since the curve due to a short application of the battery 
 would now come faster back to the zero line than formerly. This 
 effect of condensers is partly the reason why signals are so much 
 sharper and more legible when condensers are used than when a 
 line is worked direct. Of course, the application of a reversed 
 current to curb the signals is advantageous when condensers are 
 used as well as when they are not. 
 
 Fig. 12 . 
 
 § 22. The advantage of curb sending, in giving a sharp outline 
 to the signals, and in bringing the siphon of the recorder or the spot 
 of light from the mirror back (wholly or partly) to zero between 
 
 successive signals, will be seen by a comparison of figs. 11 and 12- 
 
 c 
 
34 
 
 Fig. 11 shows the theoretical form of the letter H (four deflec¬ 
 tions above the zero line) when each deflection is produced by a 
 signal current of a duration equal to 4 a, followed by a curb ( [i.e ., 
 a reversed) current of a duration equal to 3 a. This proportion of 
 curb is unnecessarily large for so low a speed, as is shown by the 
 fact that the curve is brought back past the zero line between the 
 signals. 
 
 Fig. 13. 
 
 Fm. 12 shows the form of the same letter, sent at the same 
 
 o 
 
 speed and under the same conditions, except that the signals are 
 uncurbed. In this case each of the applications of the battery 
 lasts for a time equal to 4 a, and the cable is put to earth at the 
 sending end between the signals for a time equal to 3 a, instead of 
 having a reversed current sent into it during that time. Thus in 
 
35 
 
 both cases the total interval of time used in making each signal 
 is 7 a. 
 
 § 23. Such a speed as this (one signal per 7 a) would be very 
 slow in the case of a long cable. The actual rate of transatlantic 
 signalling is about one signal per T5&. At this speed the uncurbed 
 curve shown in fig. 12 becomes indistinct, and the successive 
 impulses are barely distinguishable. The curbed signals, on the 
 other hand, give a curve somewhat resembling that in fig. 12, 
 where the return towards the centre or zero line between the 
 signals is only partial, and not complete, as in fig. 11, but is 
 immensely greater than what is observed when uncurbed signals 
 are sent at the same speed. This greater degree of legibility pro¬ 
 duced by curbing enables the speed to be increased. Experiments 
 with the artificial cable in the physical laboratory at Glasgow 
 appear to show that by using curbed signals, and transmitting 
 them automatically, as high a speed as one signal per a can easily 
 be attained on a long line. In other words, the gain in speed due 
 to the use of the automatic curb sender appears to be at least fifty 
 per cent. 
 
 § 24. In order that curb sending should be* successful, it is 
 indispensable that the contacts which give rise to signal and curb 
 currents should be made and broken at perfectly definite instants; 
 in other words, perfectly correct spacing is required. It has 
 hitherto been found to be impossible to obtain this by the use of 
 hand keys, but it is possible to have perfectly correct spacing by 
 the aid of automatic machinery. 
 
 The principle on which the automatic curb sender works is as 
 follows:— 
 
 The message to be transmitted is punched on a slip of paper in 
 right and left holes corresponding to the dash and dot of the tele¬ 
 graphic alphabet. A line of central holes is also punched to facilitate 
 the drawing along of the paper. The punched slip is put into the 
 sender, and carried along at a uniform rate by clockwork. When 
 either a right or a left hole passes under one of two prickers, the 
 corresponding pricker descends into the hole, and by doing so lifts 
 the end of a spring into the rim of a wheel, which revolves once 
 during the time occupied in the passage of one space in the punched 
 paper. The spring so caught remains in the rim of the wheel 
 during a complete revolution, and while it remains there makes 
 
36 
 
 an electrical connection between the battery and another set of 
 springs. The latter set are acted on by a double cam, which 
 revolves in the same time with the above-mentioned wheel, and 
 by the contacts made during its revolution sends first the current 
 from one pole of the battery, and then that from the other pole, 
 during a somewhat shorter time, into the cable. If the spring 
 acted on by the pricker on the left hand is raised, the first 
 current is that from the copper pole, and the second current that 
 
 Fig 14. 
 
 from the zinc pole; if it is the pricker on the right that has entered 
 a hole in the paper, the sequence of currents is opposite to that 
 just given. Thus an operation of reversal of currents takes place 
 during the passage of every space in the paper, but whether the 
 signal current is to be “ copper ” and the curb current “ zinc,” or 
 vice versa , is determined by whether the pricker has fallen into a 
 hole on the left side of the paper or on the right. 
 
 Figs. 13,14, and 15, which are engraved from photographs, give 
 three general views of the instrument. In figs. 14 and 15, the 
 
37 
 
 glass case and the standards which carry it have been removed, 
 in order to allow the works to be better seen. 
 
 § 25. The Driving Power —The motion is kept up by the 
 descent of a weight, which has occasionally to be wound up by 
 hand. In order that the driving power may continue during the 
 
 Fig. 15. 
 
 time taken to wind up the w r eight, the power is communicated 
 to the machinery not directly from the drum on which the cord 
 of the weight is wound, but indirectly through a spring which is 
 kept in a partially wound up state during the descent of the 
 
38 
 
 weight, and which gives out the energy so stored up in it during 
 the time that the weight is being wound up. This secures an 
 approximately uniform driving power even during the winding 
 up of the weight. 
 
 The arrangement will be understood by reference to fig. 16. 
 
 The axle A A' which carries the spring box S and the drum D 
 on which the cord attached to the weight is wound, is divided at 
 p into two parts capable of revolving independently of one another. 
 A ratchet wheel R' is so arranged that when the drum D is turned 
 by means of the handle so as to wind up the weight, the part A' p 
 moves independently of A p, and during that time the machinery 
 is driven by the spring in S. When the weight descends, however, 
 causing A' p to revolve in the opposite direction to that of the 
 winding up, the ratchet wheel R' no longer allows the motion of 
 A' p to take place alone, but makes A p be carried round with 
 A' p . This winds up the spring until the force exerted by the 
 tension of the spring exceeds the resistance of the machinery to 
 motion. When this happens the spring box S also revolves, 
 driving the machinery. Thus before the weight can begin to 
 produce motion of the machinery, it must first wind up the spring 
 in S to a certain extent, and the store of energy thus accumulated 
 suffices to drive the machine at an approximately uniform rate 
 while the weight is being wound up. A second ratchet wheel R 
 prevents the spring from running down without driving the 
 machinery while the weight is being wound up. 
 
 § 26. The Governor. —The speed of the machinery, and con¬ 
 sequently the speed of transmission of signals, is regulated by 
 means of a friction governor (figs. 13 and 14.) In the form of 
 governor shown there is a vertical revolving spindle, to which 
 motion is communicated by means of a pair of bevel wheels. To 
 the spindle is fixed a cross bar t (fig 14), from each end of which a 
 weight w hangs by flexible springs. As the spindle revolves 
 these weights are carried round with it, and their centrifugal 
 tendency causes them to press against the inside surface of a 
 ring or cylindrical box V. This pressure causes friction, and 
 checks the motion of the machine. The centrifugal tendency of 
 the weights is resisted by a couple of springs, which pull them 
 inwards towards the axis. So long as the centrifugal force of 
 the revolving weights is insufficient to overcome the tension 
 
 * 
 
39 
 
 of the springs and to force the weights against the ring, the 
 governor does not oppose the motion of the machinery, which there¬ 
 fore becomes accelerated, until the centrifugal force of the weights 
 becomes sufficient to bend or extend the springs to such an extent 
 that the weights rub against the ring. The friction so produced 
 prevents any further increase of speed from taking place. If now 
 the tension on the springs be by any means increased, the amount 
 of centrifugal force required to produce the distension necessary 
 to allow the weights to press against the ring is increased also. 
 Hence the speed will be increased. Similarly by lessening the 
 
 tension on the springs, the amount of centrifugal force required to 
 distend them is diminished, and the speed is consequently reduced. 
 This affords a means of altering the speed, which is effected in 
 the following manner. The ends of the springs which tend to 
 pull in the weights are fixed to a collar u which slides up and down 
 on the spindle. This collar is connected by means of levers to the 
 handle T, the movement of which causes the collar to slide up 
 and down. When the collar u is raised, the tension on the 
 springs is increased, and therefore the speed is increased also. 
 When the collar is lowered, the tension on the springs, and there¬ 
 fore the speed, is lessened. 
 
 In another form of friction governor, the motion of the 
 machinery is communicated to the vertical spindle by means of 
 the rolling contact of two discs at right angles to one another, and 
 the whole framework of the governor is supported by means of a 
 
40 
 
 contrivance called a geometrical slide,* which enables it to move 
 freely vertically up and down, but in no other direction. The 
 revolving spindle carries the weights as in the former case. When 
 the framework is moved up, the horizontal disc attached to the 
 revolving spindle of the governor approaches the centre of the 
 vertical disc attached to the machinery. Consequently the latter 
 rotates faster relatively to the former, and the machinery will 
 revolve very fast before the spindle revolves fast enough to cause 
 the weights to press outwards against the ring. In this form 
 of governor the tension of the springs which hold in the weights 
 is kept unchanged, so that the rate of revolution of the spindle 
 of the governor remains constant; but the rate of revolution of 
 the machinery relatively to that of the spindle is changed by 
 altering the height of the whole framework of the governor. This 
 is effected by means of a suitable handle on the right hand side of 
 the instrument. In this form of governor a further provision is 
 made for increasing the range of possible speed, by altering the 
 tension on the spiral springs which hold in the weights. This is 
 done by means of screws inside the governor, and attached to 
 these spiral springs. 
 
 § 27. The Starting and Stopping is effected by means of the 
 screw Y, fig 14, on the left-hand side of the instrument, which, 
 when turned in the direction of the hands of a watch, advances 
 so that its end presses against the back of the vertical bevel 
 wheel, which communicates motion to the governor. This jams 
 the wheel, and prevents the machinery from moving. When the 
 screw is turned through about half a turn in the other direction, 
 the wheel is freed, and the machinery is free to run. 
 
 § 28. The revolution of the machinery effects two objects. 
 It carries on the paper by means of a toothed roller or spur wheel, 
 working into a central row of holes in the punched paper, and it 
 
 * The geometrical slide has five bearing points, each of which is free to move upon 
 the surface on which it rests. The sixth point, which keeps the framework of the 
 governor in equilibrium, is the point in which the vertical disc is touched by the 
 horizontal disc. This mode of support gives rise to a couple tending to cause the 
 whole framework of the governor to revolve about a horizontal axis, and this 
 couple is balanced by the moment of the pressure between the two discs about the 
 same axis. Thus the pressure between the discs is kept at a constant amount 
 for all different positions into which the framework of the governor may be brought 
 for different adjustments. 
 
41 
 
 causes a spindle to rotate on which cams are fixed, which make 
 certain electrical contacts. The toothed roller which carries on 
 the paper ribbon has sixty teeth, and it revolves once for every 
 sixty revolutions of the axle which carries the cams. Hence the 
 cams make one complete revolution for every space in the paper. 
 The paper has the message punched on it in the form of side holes 
 corresponding to the dot and dash of the alphabet, with a con¬ 
 tinuous row of central holes or indentations which answer the 
 purpose of holes. The central holes or indentations are required 
 to carry the paper on ; the electrical effects are produced by the 
 
 oooo o ooo oo oooooo o 
 
 ooooo o o oooo oo o ooooooooooo ooooooooo 
 O OO OOO OOO 
 
 Fig. 17. 
 
 side holes only. Fig. 17 shows the appearance of a piece of the 
 punched paper ribbon. A space between two letters is formed 
 by one central hole, and a space between two words by two 
 centra] holes. (The spaces may also be made in another way, 
 see § 31.) 
 
 § 29. The Paper Wheel, or toothed roller which carries along 
 the paper, has two grooves on its circumference, one on each side 
 of the central row of spurs, and over these 
 the side holes in the paper pass. Fig. 18 
 shows a front elevation of the paper wheel. 
 
 Above the grooves stand two prickers, one 
 on each side, which descend through the 
 side holes as they pass under them, but 
 which cannot descend except when side 
 holes are passing. One end of a lever is 
 attached to each pricker, the other end of 
 which lifts up a small steel spring when 
 the pricker descends. 
 
 In fig. 19, B is the toothed roller which 
 carries along the paper. P is one of the Fj 
 
 prickers, which is set so as to stand over 
 
 one of the two rows of side holes. Bigidly attached to P, and 
 pivotted at li, is the forked lever F, upon the lower end of which, 
 i, the end of the above-mentioned spring rests (this spring is not 
 
42 
 
 shown in fig. 19; it is marked a in fig. 20, below); the other end, k, 
 presses up against the rim of the cam G. The spring j tends to 
 force P down; but the rim of G prevents k from rising, and there¬ 
 fore P from descending. The cam wheel 0, of which G is a part, 
 makes one complete revolution in the time taken by the paper to 
 move on through one space. When a side hole in the paper 
 passes under P, P would descend into it if k were able to 
 rise. As the cam wheel revolves, a recess, m n, in the rim of G 
 
 Fig. 19. 
 
 passes over k. At this point, k is free to rise. Simultaneously 
 an opening l in the rim of 0 passes over the end of the spring 
 which rests on i. Then, if a hole in the paper is passing under P, 
 P descends, i rises, and lifts the end of the spring through the 
 opening l into the projecting rim of the wheel 0. When n passes 
 over k , k is depressed, and P rises out of the hole in the paper. 
 The spring a (fig. 20) remains caught in the rim of 0 until a 
 revolution is completed, v T hen the opening l comes round again, 
 
43 
 
 and allows the spring to fall out. By this time the series of 
 operations which makes up the signal is completed. The cam 
 wheel has two sides precisely alike, 0 and O', the one correspond¬ 
 ing to the pricker which stands over the dot holes, the other to 
 the pricker which stands over the dash holes. The electrical 
 effects produced by the raising of the springs by means of the 
 descent of the prickers will be described further on. 
 
 In order that either pricker should descend and raise its cor¬ 
 responding spring into the rim of the cam w 7 heel 0, three 
 conditions must be fulfilled. 1st, The opening l in the rim of 
 0 must be over the end of the spring which rests on i. 2d, 
 The recess m n in the cam G must be over the end of the 
 lever k. 3d, A hole in the paper must be passing under the 
 pricker in question. By the construction of the machine, the 
 first two of these conditions necessarily happen together; for the 
 cams 0 and G are rigidly fixed relatively to one another, and the 
 opening in the one and the recess in the other pass the lowest 
 point at the same time in the revolution. The third condition 
 must be made to happen at the same time with the other two by 
 adjusting the cam wheel 0 relatively to the paper wheel B, which 
 is done by turning the former round upon its axle, and clamping 
 it in any desired position. When the instrument is properly 
 adjusted, the recess m n will pass over k just when the centre of 
 one of the side holes in the paper is passing under P. Then the 
 descent of the pricker, w T hich begins when m passes, and its ascent, 
 which is completed v T hen n passes, will both take place during the 
 passage of a hole under P, and the pricker will not touch the edges 
 of the hole either in falling or in rising. This prevents the holes 
 in the paper from becoming torn or dragged at the edges, and 
 admits of the same slip of paper being used many times over. 
 
 § 30. The axle which carries the cam wheel 0 is shown in front 
 elevation in fig. 20. This axle, as we have seen, makes one com¬ 
 plete revolution for every space in the paper. 0 and O' are the 
 two sides of the cam wheel. This cam wheel, 0 O', is called the 
 determining cam. The two sides of it are insulated from the axle 
 and from one another by vulcanite, a and a' are the two springs 
 which are lifted by the lower ends of the forked levers i i' into 
 the rim of 0 O'through the openings IT when the correspond¬ 
 ing prickers descend into the holes in the paper. The springs a 
 
44 
 
 and a' carry small pointers projecting above and below, and 
 tipped with platinum. When a dash, or right-hand side hole, 
 passes, the spring a is raised into the rim of 0, and remains there 
 during a complete revolution. In the figure it is represented as 
 being held up in this position. When held up in the rim of 0 
 a is kept in contact with the upper contact spring d, while the 
 spring a' remains in contact with the lower contact spring c'. 
 Similarly, if a dot hole had passed, a would have remained down, 
 and in contact with c ; while a would have been caught up, and 
 held up in contact with cV. So long as no hole in the paper 
 
 n'_n 
 
 Fig. 20. 
 
 passes, both the springs a and cd remain down in contact with the 
 lower contact springs c and c. 
 
 The zinc pole of the battery is permanently connected to the 
 lower contacts c and c the copper pole to the upper contacts d 
 and 6 !; when, therefore, a dash hole passes, copper is connected 
 to a, and zinc to a ; and when a dot hole passes, copper is con¬ 
 nected to ci, and zinc to a . 
 
 On the same axle with the determining cam wheel, and 
 revolving along with it, are two other cams—I' and I—called 
 respectively the signal and curb cams. They are insulated from 
 one another by a disc of vulcanite, and are insulated from the 
 axle and from the determining cam by the vulcanite tube J. 
 They are fixed relatively to one another by a small vulcanite 
 screw. Fig. 21 gives a side-view of the signal and curb cams. 
 The signal cam I' has a projecting edge extending for rather 
 more than half the circumference; the curb cam I has a pro¬ 
 jecting edge which begins where the projection on I' leaves off, 
 
45 
 
 and which leaves off where that on I' begins. Underneath these 
 cams are the springs e and e' (fig. 20). During rather more than 
 half the revolution the projecting edge of I' depresses the spring 
 e, and causes it to make contact with 
 the lower contact spring /', while 
 the spring e remains up and in con¬ 
 tact with the upper stud g. When 
 the projecting edge of I' has passed 
 e rises, and makes contact with g, 
 while simultaneously the projecting 
 edge of I depresses e, and holds it in 
 contact with / during the remainder 
 of the revolution. Thus during 
 rather more than half the revolution, 
 e' is in contact with /', and e with g, 
 and during rather less than half the revolution e is in contact 
 with / and e with g. These actions depend simply upon the re¬ 
 volution of the axle, and are not affected by the punched paper or 
 by the positions of the springs a and a , but the electrical effects 
 which these actions produce do depend upon the position of a 
 and a\ and are therefore determined by the holes in the 
 paper. 
 
 § 31. Electrical Action. —The spring a is permanently in con¬ 
 nection with the lower contact springs / and /'. The spring a' is 
 permanently in connection with the upper contact studs g and g\ 
 The spring e! is permanently connected to earth, and the spring e to 
 line. The electrical changes which take place during a revolution 
 of the axle will be understood by reference to the diagram, fig. 22, 
 in which the letters refer to the same parts as in fig. 20. In the 
 diagram the spring a is represented as having been raised into the 
 rim of the determining cam by the descent of the right-hand pricker 
 into a hole in the paper. At the instant that a rises, the projecting 
 rim of the signal cam I' comes round and depresses e\ Thus the 
 copper pole of the battery is connected by way of d, a, f ', and d to 
 earth, while the zinc pole is connected by way of c , a', g , and e 
 to line; and a negative current enters the cable to produce the 
 “ dash ” signal. This state of things lasts for rather more than half 
 the revolution, until the projecting rim of the signal cam Y has 
 passed and that of the curb cam 1 has come round. Then e rises 
 
 
 Fig. 21. 
 
46 
 
 and e is depressed, no change, however, taking place in the position 
 of a and a. The zinc pole is now connected by way of c, a', g', and 
 e' to earth, while the copper pole is connected by way of d, a , /, 
 and e to line. This sends a positive current into the cable to pro¬ 
 duce the curb to the “ dash ” signal, which lasts as long as the 
 spring e is depressed by the curb cam. The joint effect of the 
 two currents is, as we have already seen (§ 20), to produce a 
 clearly defined “ dash ” signal. When the revolution is completed, 
 a falls out of the determining cam through the opening l, and, 
 unless another signal immediately follows that which w T e have been 
 considering, the copper pole of the battery is disconnected both 
 from line and from earth. 
 
 If, instead of a dash hole, a dot hole in the paper had passed, 
 the pricker on the left side would have descended, and the spring 
 a would have been raised into the rim of O', while a remained 
 down. The reversal of the springs c and e' operated on by the 
 signal and curb cams would have gone on as before. Thus during 
 the passage of I' the zinc pole of the battery would have been con¬ 
 nected by way of e, a,/', and e' to earth, while copper would have 
 been connected by way of d\ a, g, and e to line. Similarly, 
 during the passage of I, copper would have been connected by 
 way of d\ a ', g', and e' to earth, while zinc would have been con¬ 
 nected by way of c, a , /, and e to line. There would thus have 
 been a 'positive signal current followed by a negative curb current 
 of shorter duration, the joint effect of which would have been to 
 produce a “ dot ” signal. 
 
 The relative lengths of the signal and curb currents depend 
 upon the relative lengths of the projecting rims of the cams I' 
 
47 
 
 and I. * Whether the longer current shall be positive and the 
 shorter negative, or vice versa, is determined by the position of 
 the springs a or a in the rim of the wheel 0 O', which is therefore 
 called the determining cam wheel. If a succession of holes 
 passes under either of the prickers, the corresponding spring is 
 held up continuously in the rim of the determining cam wheel 
 until all have passed, because, while the space l is passing, 
 the descent of the pricker into the hole causes the end i of the 
 forked lever to rise, and so prevents the spring from falling out of 
 the rim. If a dot and a dash hole pass simultaneously under 
 the prickers, both the springs a and a' will be raised, and no 
 electrical effects will be produced, for the zinc pole of the battery 
 will be disconnected. Hence two side holes opposite to each other 
 may be used to produce a space, instead of no side hole. 
 
 § 32. The Contact Plate. —The several contact springs, with 
 
 their contact pieces and connections, are all fixed on a slab of 
 
 vulcanite called the contact plate W (figs. 14 and 15). The con-; 
 
 - — -—- - —— 
 
 tact plate is secured in position by means of fe e screw H, which 
 causes three projecting points in the frnmawffHr~7yr~T^ instru¬ 
 ment to prpgg flg^jnsl ii Imln i V TmnvA in line with the hole, 
 a**d arpTancTiii a piece of metal connected to the contact plate (see 
 fig r -20). This mode of support is called a geometrical clamp; it has 
 this advantage, that the plate cannot take up any other than one 
 certain position, and a single screw is sufficient to keep it fixed. 
 
 The springs c, c\ d, d' , / and /' are provided with brass guard, 
 bars or stops, which limit their range of motion, and prevent them 
 from vibrating when the instrument is running fast, or from 
 sticking to and following the moving springs a, a', e, and e. 
 
 The two halves of the determining cam are insulated from one 
 another and from the axle by vulcanite. Each of the forked 
 levers connected to the prickers is completely insulated. The 
 signal and curb cams are also insulated from one another and 
 from the axle—lienee no electrical contacts take place except 
 those which have been considered. The mode in which the signal, 
 
 * With regard to the proportion which the length of the signal cam ought to 
 hear to that of the curb cam, it should be understood that the greater the speed of 
 signalling is relatively to the retardation, or value of a (§ 19), for any cable, the 
 more nearly equal should the signal and curb cams be. If the speed of signalling 
 on different cables be varied so as to be the same relatively to a for each cable, the 
 same pair of cams will be suitable for all. 
 
48 
 
 curb, and determining cams are fixed to the axle will be under¬ 
 stood by reference to fig. 20. J is a vulcanite tube to which the 
 determining cam 00' is rigidly fixed. The brass screw K on the 
 right of the determining cam clamps it and the tube J on to the 
 axle by jamming them against the shoulder M. The vulcanite screw 
 Q on the left of the signal cam clamps it and the curb cam on to 
 this tube, and therefore to the axle also. 
 
 § 33. Single and Double Curb. —In the foregoing description 
 of the electrical action, it has been assumed that the spring e 
 was depressed by the signal cam at the same instant that the 
 spring a or a' rose into the rim of the determining cam. This 
 arrangement would give the whole of the signal current first, 
 followed by the whole of the curb current, and the revolution 
 would begin with the beginning of the former and end with the 
 end of the latter. A signal may, however, be produced by the 
 joint action of more than two currents, and may represent 
 the resultant effect of three or any number of currents following 
 each other in alternate directions, and being of different lengths. 
 
 So long, however, as the form of signal and curb cams described 
 above remains unaltered, there are only two other combinations 
 possible, and these are easily obtained by changing the position 
 of the signal and curb cams relatively to the determining cam. 
 
 The arrangement which has hitherto been assumed to exist is 
 called single curb. In it the spring d is depressed at the instant 
 that a or a rises, and the beginning of the passage of the rim of 
 the signal cam coincides with the beginning of the signal. 
 
 If the signal and curb cams are turned round on the axle so as 
 to be slightly in advance of the determining cam, it is evident that 
 when either a or a' rises, the spring d will already have been 
 depressed for some time, and the first current sent will be shorter 
 than formerly, by an amount represented by the distance through 
 which the cams II' have been turned forward. The second or curb 
 signal will, however, be as long as before, for the spring a or a! will 
 continue up during the whole time of the passage of the rim of 
 the curb cam. But since the signal and curb cams are in advance 
 of the determining cam, the rim of the curb cam will all have 
 passed before the spring a or a! has fallen out of the rim of the 
 determining cam. Hence, before the signal is ended the rim of 
 the signal cam again depresses the spring d and sends a current into 
 
49 
 
 the cable of the same name as that first sent. This is, however, of 
 short duration, for as soon as that fraction of the signal cam’s rim 
 has passed which represents the distance by which the signal and 
 curb cams are in advance of the determining cam, the revolution will 
 be complete, the spring a or a' will drop out of the rim of the latter, 
 and no farther contacts will occur in that signal. There will thus 
 have been three currents produced, the first and third being of the 
 same name, and the second of the opposite name. The second 
 curbs the first, and the third curbs the surplus curbing effect of 
 the second on the first. Of course the sum of the first and third 
 bears the same relation to the second as the length of the signal 
 cam bears to the length of the curb cam. This arrangement is 
 called double curb. Fig. 23 shows the theoretical form of the 
 letter E sent with double curb, the first current being of a duration 
 equal to 3 a, the second of an equal duration, and the third of a 
 duration equal to la, the total time being 7 a, as in the examples 
 previously given. The full line IY. is the resultant signal, of 
 which the dotted lines I., II., and III. are the components. 
 
 § 34. Preparatory Curb —If the signal and curb cams are 
 turned back so as to be slightly behind the determining cam, then 
 when a or a rises, e is already depressed, and continues so for a 
 short time, and thus a short curb current is sent first, then the 
 whole of the signal current follows, and lastly the remainder of 
 the curb. This arrangement is called preparatory curb. Fig. 24 
 shows the theoretical form of the letter E given by it. The period 
 
 D 
 
50 
 
 of the preliminary curb current is la, that of the signal current 
 4 a, and that of the second curb 2a, the total period being la as 
 before. 
 
 § 35.—We are thus able with a given pair of signal and curb 
 cams to produce three different arrangements of the currents which 
 go to make up a signal. A perfectly curbed signal,—that is to say, 
 a signal in which the curve of arrival comes rapidly down to the 
 zero line, and never crosses or leaves it,—could only be produced 
 by using an infinite series of curbing currents alternate in direc¬ 
 tion, and each somewhat shorter than its predecessor. Of course 
 such an arrangement is practically impossible. When the curbing 
 is necessarily imperfect, as it always is in practice, it appears that 
 the arrangement described above as single curb is the best of the 
 three. This is a question which will best be decided by actual 
 trial. It appears likely, however (independently of any considera¬ 
 tion of the form of the curve of arrival), that the best means to 
 produce a sharply defined signal would be to make use of the 
 single curb arrangement, thereby bringing, in the first place, the 
 maximum influence at command to bear upon the indicator (the 
 needle or coil, as the case may be) to deflect it, and then, in the 
 second place, the maximum influence at command to cause it to 
 return to its normal position—always provided that within the 
 limits of a single signal the second influence is insufficient to cause 
 a return much past the zero position. This last condition can 
 
51 
 
 always be made to hold good by limiting the length of duration of 
 the curbing current relatively to the speed of the signalling. 
 
 § 36. Adjustment of the Contact Plate. —To put in the 
 Contact Plate .—Lift off the top of the case and remove the front 
 glass plate. Introduce a piece of the paper ribbon. Start the 
 machinery, and stop it when a piece of the paper in which there 
 are no side holes punched is passing under the prickers. This will 
 cause the ends i i of the forked levers to lie in their most depressed 
 position. Then slip in the plate, taking care that the springs e e' 
 are not bent by being pressed against the sides of the signal and 
 curb cams, and that the ends of the springs a a take up their 
 proper positions on the top of the lower ends i i' of the forked 
 levers^^' Whcn one of the three small feot on - tho side of the fram e- 
 work enters the hole, the other the groove, anfijdie-^ 
 on the plane surface on thepiu£fi^f-ffl^TaT*onthe right hand side 
 of the contactjiLaterd^Ie^late will be in its proper position, and is 
 to-hu r Securcd there by - tightening up therscrcwIL - 
 
 In removing the contact plate the same precautions have to be 
 observed. The ends i % of the forked levers should be depressed 
 by having a piece of unpunched paper under the prickers. 
 
 The platinized contacts on the various springs should be cleaned 
 frequently. They must be kept free from all traces of oil, and 
 should be frequently dusted with a cameTs-hair brush. If 
 the contacts made are defective or fail, the points of contact should 
 be cleaned with a very fine file. 
 
 Care must be taken that when the springs a, a , e, or e rise or 
 fall, they do not make contact with both their upper and their 
 lower contact springs simultaneously. If they did so the battery 
 would be short-circuited and sparks would pass which would burn 
 the contacts. If any one of the springs a, a, e, or e is observed, 
 when rising or falling, to make one contact before it breaks the 
 other, the guard bars which limit the play of the contact springs 
 must be gently bent until this no longer occurs. Two contact 
 plates are provided with each instrument. When the instrument 
 is in constant use the contact plates should be changed every 
 second day, and the one not in use should be carefully cleaned 
 before being replaced. 
 
 § 37. Adjustment of the Determining Cam. —Start the 
 machine with a piece of punched slip in it, and stop it at the 
 
52 
 
 instant a side hole is passing under one or other of the two 
 prickers. Then taking hold firmly of the vulcanite tube J (fig. 
 20), loosen the brass screw K on the right. Be careful not to 
 apply so much force as to bend or twist the axle. The cams 0 O' 
 and vulcanite tube J (as well as the cams I I') will then be free 
 to move round on the axle. Turn them round until the centre of 
 the openings l V in the rim of the determining cam wheel are just 
 over the springs a a'. The pricker under which there is a hole 
 in the paper will then be able to descend into the hole, and to 
 raise its corresponding spring into the rim of the determining cam. 
 The centre of the hole in the paper should just be passing under 
 the pricker at the instant that the centre of the opening l is pass¬ 
 ing over the spring a. When the cams are turned round into 
 such a position that this happens, secure them and the tube J in 
 that position by screwing up K. 
 
 This adjustment is of the utmost importance. When signals 
 fail, the cause is almost always bad adjustment of the determining 
 cam. It is difficult to judge by eye whether the pricker is exactly 
 over the centre of the hole in the paper. When the adjustment 
 has been made, turn the axle slowly round by hand backwards 
 and forwards, and observe whether the prickers tear either the 
 back or front edges of the holes. If the adjustment is perfect, 
 they will fall into and rise out of each hole when the axle is 
 turned either backwards oj* forwards without touching the paper 
 at either edge of the hole. 
 
 § .38. Adjustment of the Signal and Curb Cams. 
 
 1°. For Single Curb .—Take hold of the vulcanite tube J firmly 
 with the right hand, and loosen the screw Q with the left. The 
 signal and curb cams I' and I will then be free to slip round upon 
 the tube J. Put in a piece of punched paper, start the machine 
 and stop it just when one of the prickers is descending into a hole* 
 and is raising its corresponding spring into the rim of the deter¬ 
 mining cam. Turn the signal and curb cams round until the pro¬ 
 jecting edge of the signal cam I' is just depressing the spring e 
 Then secure the cams in this position by tightening up the screw 
 Q. This adjustment is perfect when the depression of the spring 
 e is exactly simultaneous with the rise of the spring a or a. The 
 axle should be allowed to revolve very slowly, by checking its 
 motion with the hand, so that it may be seen whether this adjust- 
 
53 
 
 ment is right; and if not, the cams I and I' must be shifted round 
 until a state of perfect adjustment is reached. 
 
 2°. For Double Curb .—Adjust as above for single curb, and then, 
 loosening the screw Q, turn the cams 11' slightly round on the 
 axle, moving their upper sides away from you as you stand in 
 front of the instrument. In other words, turn the cams round so 
 as to he slightly in advance of their previous position, so that (say) 
 half an inch of the projecting rim of the signal cam I' has already 
 passed over the spring e' before the spring a or a' rises up into the 
 opening in the rim of the determining cam. Secure the cams in 
 this new position by screwing up Q. The depression of e', which 
 has now occurred before a or a rises, will produce the second 
 curb of the previous signal (see § 33). 
 
 3°. For Preparatory Curb .—Adjust as above for single curb, and 
 then, loosening the screw Q, turn the cams I T slightly round upon 
 the axle, moving their ■ upper sides towards you as you face the 
 instrument. That is, turn the cams round so as to be slightly 
 behind their position when adjusted for single curb. Then tighten 
 up Q. The spring e' is now not depressed until some time after 
 the spring a or a has risen, but the spring e is depressed during 
 that time, and thus a short curb current is applied to the cable at 
 the beginning of the signal (see § 34). The distance by which the 
 cams are put back from their position for single curb should not 
 exceed about half an inch measured along the rim. 
 
 § 39. Speed of tiie Machinery. —The means by which the 
 speed is altered have been described already (§ 26). In the first 
 form of governor there mentioned, which is the one shown in 
 figs. 13 and 14, the speed is altered by sliding backwards or for¬ 
 wards the handle T (fig. 14), which has the effect of raising or 
 lowering the collar u on the spindle of the governor. This 
 increases or diminishes the tension on the springs, which pull in 
 the weights w vi. When the tension on the springs is increased, 
 a greater speed is required to give centrifugal force enough to the 
 weights to cause them to diverge and press against the ring or 
 box Y. It is not until they press against the box that they 
 cause any check to the motion of the machine, but as soon as 
 they do press against the box, the friction so produced prevents 
 any further increase of speed. Hence the more tension there is 
 on the springs, the faster will the machine go. 
 
54 
 
 In the second form, the tension on the springs which prevent 
 the weights from diverging is not altered during adjustment, and 
 consequently the maximum rate of revolution of the governor 
 remains constant; but the whole framework of the governor is 
 moved up or down so that the relative rates of revolution of the 
 machinery and of the governor is altered (§ 26). In this form 
 the speed can be still farther altered by varying the tension on 
 the springs which hold back the weights. This can only be done, 
 however, when the machine is standing still. Care must be taken 
 that both weights are held back with equal force, so that when 
 they are caused to diverge by the revolution of the governor, they 
 may both touch the ring at the same time, and press against it 
 equally. 
 
 The box of the governor must be kept clear of dust and oil. 
 The weights must not be allowed to scrape against the bottom of 
 the box. They can be raised by loosening the screws which 
 clamp the two pieces of straight spring by which each weight is 
 suspended. These screws must be firmly secured before the 
 machine is started. 
 
 No attempt should be made to vary the speed of the machine 
 by altering the driving weights. A weight of about 14 lbs. will 
 generally be found to do well. 
 
 All the bearings of the axles must be kept well oiled. If the 
 bearings are too tight, they may be loosened by means of the 
 bearing screws q q (fig. 20). After loosening the nuts pp the 
 screws can be turned either out or in; and when the desired 
 adjustment is arrived at, all change will be prevented by tighten¬ 
 ing up p and p'. These and the similar screw bearings on the 
 other axles also afford the means of moving any one of the axles 
 along for a short distance in the direction of its length. 
 
 The inner cams of the determining cam wheel (G and G') must he 
 kept well oiled, for otherwise the friction on them of the levers k 
 and k ' (fig. 19) will check the running. 
 
 § 40. Electkical Connections. —The battery power required 
 for the automatic sender is considerably greater than that required 
 in working by hand, not only because the curbing reduces the size 
 of the signals, but also because the speed of sending with the auto 
 is much greater than with the hand key, and consequently the 
 
55 
 
 maximum deflection of the coil or needle at the receiving end is a 
 smaller fraction of the whole possible deflection. 
 
 When the automatic sender is used, it is of course necessary to 
 provide a hand key, which may be easily thrown into circuit; 
 and for the reasons just given, a separate battery should be used 
 on the hand key of a much smaller number of cells than that 
 used on the auto. No rule can be laid down as to the amounts 
 of battery power. For long cables it will probably be found that 
 twice as many cells are required on the auto as on the hand key. 
 
 In order to join up the automatic sender in circuit with the 
 recorder, the connections shown in figs. 8 and 9 have, one or other 
 of them, to be set up. A switch of the form shown in fig. 25 has 
 next to be provided. By means of the lever 
 handle of this switch, the terminal C can be 
 connected at will either to A or to B. The 
 wire which leads from the sending key to the 
 recorder switch has then to be disattached 
 from the sending key, and attached instead 
 to the terminal C of this second switch. Then 
 from B a wire must lead to the hand key, 
 which is to be provided with a suitable send¬ 
 ing battery, and from A to the terminal 
 marked L in the automatic sender. The ter¬ 
 minal E of the auto is connected to earth, and the terminals C 
 and Z of the auto are connected to the copper and zinc poles of 
 another (and larger) sending battery. Then by simply turning 
 this switch over to the right the hand key will be thrown into 
 circuit, while by turning it to the left the auto will be joined 
 up instead. 
 
 The arrangement of the recorder connections shown in fig. 9 is 
 the most suitable for use with the automatic sender. The auto¬ 
 matic signals recorded at the sending station when that arrange¬ 
 
 B 
 
 ment is made use of are very much more easily read than they 
 are when the system shown in fig. 8 is adopted. In the latter 
 case the curb, or second and reversed part of the signal, comes out 
 nearly or quite as prominently as the first part or signal proper. 
 Thus the letter e will appear on the recorder slip at the sending 
 station as two deflections, one above and one below the line, 
 almost exactly equal in amplitude, in form like the letter a on 
 
56 
 
 the receiving slip, and the letter a on the sending slip will appear 
 like an on the receiving slip. This makes the sent signals difficult 
 to read; but no such difficulty is felt when the part of the current 
 which records the signals at the sending station is allowed to go 
 to earth there, as it is in the arrangement of connections shown in 
 fig. 9. (See § 14.) 
 
 § 41. Failure of Signals. —If complaints are made that signals 
 sent by the auto occasionally fail to be recorded at the receiving 
 end, that dots and dashes are now T and then missed, it will be 
 necessary,— 
 
 1st, To look at your recorder slip, and see whether the signals 
 which are reported to have failed at the other end appear there. 
 If they do, then the fault must be at the other end, but if they 
 do not, 
 
 2d, Eead your perforated slip, and see whether the holes corres¬ 
 ponding to the signals which have failed have not been missed in 
 the punching. 
 
 3 d, If the failures are still not accounted for, they must be 
 due to the imperfect adjustment of the auto, or to bad spacing in 
 the punched paper. 
 
 Stop the machine when a hole is passing under one of the 
 prickers, and just when the opening l in the rim of the determin¬ 
 ing cam is passing over the springs. If now the pricker is fairly 
 over the centre of the hole (see § 37), the adjustment is perfect 
 for that hole, and, if the spacing of the holes in the punched slip 
 is regular, the adjustment must be perfect for all holes. In some 
 of the forms of punchers about to be described, the spacing in the 
 paper must be perfect, but in another of the forms it is possible 
 that the side holes may sometimes vary slightly in position rela¬ 
 tively to the centre holes. Suppose that one of the side holes is 
 slightly behind its proper position. Then at the instant that the 
 opening l is passing over the springs, the hole in the paper will 
 not be under the pricker as it should be, and consequently the 
 pricker will not be able to descend, and the signal will be missed. 
 It will generally be found possible in this case to avoid having 
 any signals missed by using an imperfect adjustment of the auto 
 as follows:—Take a slip of the badly spaced paper, on which 
 some words which you know are punched, and run it through 
 the machine very slowly, checking the revolution by hand. 
 
57 
 
 Watch the springs, and read the words by their movements, 
 and notice carefully what signals fail. See whether the fail¬ 
 ures are caused by the corresponding holes being behind their 
 proper positions, or in advance of their proper positions. If you 
 find that the failures are due to the former cause, then loosen the 
 screw K (fig. 20) and turn the cams slightly backwards, so that 
 when a properly spaced hole is passing, the pricker may descend, 
 not into the centre of it, but near its back edge. Then when one 
 of the holes passes which has been punched slightly behind its 
 proper position, it is almost certain that some part of it,—probably 
 a part near the forward edge,—will be passing under the pricker 
 at the right instant, so that the pricker will descend and the signal 
 be transmitted. Of course if the faulty holes had been in advance 
 of their proper position, it would have been necessary to turn the 
 cams slightly forward. 
 
 \ih. When signals are reported to fail, although the prickers 
 enter the corresponding holes, all the contact springs, &c., must 
 be cleaned. 
 
 A good plan for seeing whether the prickers are entering the 
 holes is to take a piece of the punched paper and smoke it over 
 by drawing it through the flame of a lamp or candle; then run 
 it through the machine. Every time the recess m n in the cam 
 G (fig. 19) comes round, the prickers will* descend, and if a solid 
 part of the paper is passing under them, they will leave marks on 
 the smoked paper at the points where they touch it. If these 
 marks are seen close to the edge of the side holes, the prickers 
 have evidently not entered the holes, and the adjustment must be 
 looked to. 
 
 § 42. General Directions. —When the outer case of the instru¬ 
 ment has to be removed, it should be taken off bodily by taking 
 out the screws at the four feet z zzz (fig. 15.) The various brass 
 pieces of the case should not be separated from one another, 
 as a difficulty would probably be experienced in putting them 
 together again. 
 
 If it is desired for any reason to remove the paper trough U 
 (figs. 14 and 15), or the prickers, the contact plate must be first 
 removed; then the axle which carries the cams should always be 
 taken off. This is done by taking out the screw r (fig. 15), which 
 secures a standard which carries the bearings for the right hand 
 
58 
 
 end of the axle. When the screw r is taken out, this standard 
 comes off, and the axle is thus easily removed without having its 
 bearings interfered with. The paper trough and prickers can 
 then he removed bodily by taking out the screws xy xy on the 
 right hand side-plate of the instrument, which secure the angle- 
 pieces carrying the trough. In this way the trough and prickers 
 can be taken off together without any of the small screws being 
 touched which fix together the supports of the prickers. 
 
 Care must be taken that the successive turns of the string 
 wound upon the driving drum D do not overlap each other, for if 
 they do they are liable to come in the way of the projecting spurs 
 on the toothed wheel which carries the paper along. 
 
 The string which suspends the driving weight must hang freely, 
 and not chafe against the sides of the hole in which it passes 
 through the table. 
 
 PUNCHERS. 
 
 § 43.-—The machines for perforating the paper ribbon used in 
 the automatic sender are of several forms. One puncher is adapted 
 for punching side holes only, and the paper used for it may be 
 prepared beforehand by having a properly spaced row of central 
 holes punched in it. This puncher has three finger keys. When 
 any one of the three keys is depressed, the paper is carried along 
 a step. When the central key is depressed nothing further hap¬ 
 pens, but when either of the side keys is depressed a side hole is 
 perforated in addition to the paper being moved forward. It is 
 essential that the paper should be at rest when the punch enters 
 it, and should continue at rest so long as the punch is in it. The 
 machine is therefore arranged so that the movement of the paper 
 happens early during the stroke or depression of the key, and the 
 punch is not forced through the paper until the end of the stroke. 
 The manner in which this is effected will be readily understood 
 by an inspection of the machine. The feed motion, by which the 
 paper is carried along, may not, however, be so readily understood 
 without explanation. The paper is carried along by the revolution 
 of a toothed roller, the teeth of which enter the previously pre¬ 
 pared central holes. On the same axle with this toothed roller is 
 a ratchet wheel, having the same number of teeth as there are in 
 
59 
 
 the roller, so that the paper advances one space when the ratchet 
 wheel is pushed forward one tooth. The ratchet w T heel is caused 
 to advance by the following means:—The depression of any of 
 the three keys is made, by means of a spring, to communicate 
 horizontal motion to the pivotted end of a long horizontal paul, 
 the other end of which gears into the upper side of the ratchet wheel. 
 When the key is depressed, this paul is pressed along, and the 
 ratchet wheel advances. The end of the paul which gears into it is 
 thus carried upwards as well as along, and by the time that the 
 ratchet w T heel has advanced through the space corresponding to one 
 tooth, the end of the paul has risen so far that the back of the paul 
 presses upwards against a firm stop fixed above it. This prevents 
 any further advance of the ratchet wheel during the remainder of 
 the stroke. The horizontal pressure on the pivotted end of the 
 paul continues, however, and consequently the ratchet wheel (and 
 therefore the toothed roller and the paper) is held firm during the 
 descent of the punch. When the key is allowed to rise, the hori¬ 
 zontal pressure on the paul ceases; it is pulled backwards by a 
 suitable spring, and its weight causes the unpivotted end to fall 
 down into gear with the next tooth of the ratchet wheel. The 
 ratchet wheel is prevented from following the horizontal paul 
 backwards by a second paul or click. 
 
 In using this instrument, it is not essential to have paper in 
 which a central row of holes has previously been punched. If a 
 slip of plain paper be used, the toothed roller will make a series 
 of central embossed marks or indentations, which will be found 
 to answer the purpose of central holes sufficiently well, for the 
 paper so prepared will run through the automatic sender, the teeth 
 in the spur wheel of which will enter the successive central inden¬ 
 tations in the paper. It will be found necessary, when embossed 
 paper is used, to apply a strong retarding force to the paper as it 
 enters the auto, so as to prevent it from riding on the top of the 
 spurs, instead of being pierced by them. This retarding force is 
 easily applied, in exactly the same way as it is applied in the 
 siphon recorder, by passing the paper under a spring guide, the 
 pressure of which upon the paper will cause friction and hold 
 back the paper. (See a fig. 1.) 
 
 The depression of the keys of this puncher is most easily effected 
 by the help of light wooden mallets, on the end of which india- 
 
60 
 
 rubber is fixed, or, better still, by putting fingerstalls tipped with 
 india-rubber over two fingers of each hand. Care must be taken 
 not to strike a sharp or violent blow, but rather to make the blow as 
 much like a shove as possible. If the blow be too sharp, the paper 
 will not have time to advance through a complete space before the 
 punch enters it, and a misplaced or torn hole will be produced. 
 Violent blows are also very apt to break the springs by which the 
 feed motion is worked. To avoid breakage, multiple springs are 
 used for the dot and dash keys. If the single spring under the 
 centre key should break, it is not necessary to interrupt the work 
 to put on a new spring, for the spaces may be made by depressing 
 both side keys simultaneously. 
 
 The bridge which forms a back stop for the keys should be 
 adjusted so as just to touch the backs of the levers, without press¬ 
 ing on them, when they are in their raised position. 
 
 § 44.—The Power-Puncher. —In this form of puncher the 
 heavy work is done by power stored up in the form of a wound-up 
 spring or raised weight, and the operator, by depressing the finger 
 keys, releases a detent, and so allows the stored up power to take 
 effect. Hence the name, in which the prefix “ power ” has the 
 same significance as it has in the term “ power-loom.” 
 
 In the power-puncher there are three finger keys—for the dot, 
 dash, and space. When any one of these is depressed, a detent 
 allows one tooth of an escapement wheel to pass. There are 
 twelve teeth on the wheel, so that the axle which carries it 
 revolves through one-twelfth of a whole revolution for every 
 depression of a key. On the same axle is fixed a cam wheel 
 called the paper cam, with twelve projections on it, which act 
 (as they pass) upon one end of a lever, the other end of which 
 carries forward a ratchet wheel tooth by tooth. On the same axle 
 with the ratchet wheel is a toothed roller which gears into the 
 central row of holes in the paper. The paper is thus moved for¬ 
 ward one space whenever any one of the three keys is depressed. 
 The projections on the cam are so designed as to make the paper 
 start and stop slowly at each movement, so as to secure uniform 
 spacing at different speeds. There is a second ratchet wheel fixed 
 on the same axle with the one just mentioned, into which a paul 
 is made to gear just as the punch is entering the paper. In this 
 way the paper is held perfectly steady during the descent of the 
 
61 
 
 punches. The feed motion of the power-puncher is identical with 
 that of the single lever puncher, which is described at greater 
 length in § 45. 
 
 There are three punches, corresponding to the centre hole and 
 the two side holes.' The manner in which they are forced down 
 into the paper is as follows:—On the axle, which carries the 
 escapement wheel and paper cam, there is a second cam wheel 
 fixed, called the* punching cam, on whose rim there are twelve 
 wedge-shaped projections. One of these passes over the central 
 punch and depresses it every time that the axle revolves partially 
 owing to the depression of any one of the three keys. If the 
 centre key is depressed, then nothing occurs except the release 
 of the detent, and the consequent partial revolution of the axle, 
 which causes the paper to advance one space, and causes one 
 central hole to be punched. Neither of the side punches is 
 affected, because they are somewhat shorter than the central 
 punch, and so allow the revolving wedges of the punching cam to 
 pass without depressing them. But if one of the side keys is 
 depressed, a packing piece slides in over the top of the corre¬ 
 sponding side punch, and, the detent being released as before, the 
 revolving wedge of the punching cam cannot now pass without 
 depressing both the centre and the side punch, which has been 
 (so to speak) lengthened by the introduction of the packing piece. 
 If both side keys are simultaneously depressed, both packing pieces 
 are slipped in over the punches, and all three holes are punched. 
 The effect of this would he (as we have seen in § 31) to produce 
 a space in the sending. 
 
 The spring or weight has to be w T ound up from time to time. 
 With an ordinary Morse spring, the power-puncher will punch 
 about twenty words without needing to he wound up afresh. 
 
 Great care must be taken to keep the fingers clear of the keys 
 which are intended not to be depressed, otherwise the packing 
 pieces may be slipped in accidentally, and false signals he pro¬ 
 duced. 
 
 The best way to put in the paper is to double it over the end 
 of a piece of steel spring about six inches long, and push the 
 spring and paper in together,—care being taken to draw hack the 
 spring before beginning to punch. 
 
62 
 
 § 45, The Single Lever Puncher. —In this puncher the prin¬ 
 ciple of packing pieces is used, and the feed motion is the same as 
 that of the power-puncher, but the work is entirely done by 
 hand. There is a long horizontal lever, on the end of which 
 nearest to the operator there are three finger keys. When any one 
 of these keys is depressed, the near end of the lever is depressed 
 with it. Fixed to the lever is a projection A (fig. 26), with a 
 cam-shaped surface, and as the lever is depressed this cam slides 
 along the surface of another piece B in contact with it, and 
 gives a reciprocating motion to B. The piece B actuates the feed 
 in the manner described below. When the centre key is depressed 
 the lever descends, works the feed, and a centre hole is punched. 
 When either of the two side keys is depressed, a packing piece 
 slides in over the top of the corresponding side punch; then the 
 lever descends, works the feed, and punches both a side and a 
 centre hole. A spiral spring, fixed to the distant end of the lever, 
 pulls it back when the pressure of the fingers is removed. 
 
 Fig. 26. 
 
 The feed mechanism is shown in fig. 26. The paper is carried 
 along by a toothed roller C, whose teeth enter the central holes. 
 
03 
 
 This roller is placed immediately behind the punches. Fixed on 
 the same axle as the roller are two ratchet wheels, D and E, 
 whose teeth face opposite ways. D is the one by means of which 
 the paper is drawn along; the other one, E, is required in order 
 that the paper may be held so as to be perfectly incapable of 
 moving during the time that the punches are entering and leaving 
 it. During the early part of the descent of the lever, the piece B 
 descends, and carries with it a spring paul F, fixed on the side of 
 it nearest to the centre of the instrument, and gearing into the 
 upper side of the ratchet wheel D. This paul pulls the ratchet 
 wheel round one tooth, and consequently causes the paper to 
 advance through one space. When the advance is complete, a 
 click G, working on the lower side of the same ratchet wheel, falls 
 into gear, and so prevents the wheel from turning the wrong way 
 during the backstroke. Just before the punch or punches enter 
 the paper, a paul H on the outer side comes into gear with the 
 ratchet wheel E on its lower side. This paul has been gradually 
 rising during the descent of the lever, but it only comes into gear 
 when the paper is just about to be punched. It remains in during 
 the whole time that the punch or punches are in the paper, and 
 insures that the paper does not move during that time. As the 
 lever is allowed to rise, this paul falls out of gear; the paul F 
 rises so as to catch hold of the next succeeding tooth of D, while 
 the click G prevents the roller from turning backwards. The 
 paul H is actuated by a pin I projecting from the outer side of 
 B. There is a spring K pressing on the back of the paul H, in 
 order to disengage it from the ratchet wheel E when the lever 
 rises. There is also a spring L pressing on the back of B, to 
 make it rise when the lever rises. The two springs K and L are 
 fastened by screws under the sole-plate of the instrument. 
 
 The surface of the cam A is so shaped as to start the paper 
 gradually, and also so as not to bring any force to bear upon B 
 during the actual punching of the paper. The feed motion is 
 completely over before the punch enters the paper. 
 
 The springs and pauls for the feed motion are usually provided 
 in duplicate. Before attempting to take the machine to pieces, 
 the operator ought to make sure that he understands what the 
 conditions of perfect working are. The paul F must begin to pull 
 round the ratchet D the instant that the lever begins to descend. 
 
64 
 
 It must cease to pull as soon as the paper has advanced one 
 space, and before the punch begins to enter the paper. At the 
 instant that it ceases to pull, the click G must fall into gear, and 
 at the same instant the paul H must come into action. During the 
 remainder of the descent of the lever, no force must be brought to 
 bear upon B by the cam A, although A continues moving. 
 
05 
 
 APPENDIX. 
 
 A 
 
 New suspension for weights in Recorder . 
 
 In the recorders, as hitherto made, and as shown in figs. 3 and 
 4, the strings which suspend the weights pass behind a bridge x, 
 and the weights hang pressing on an inclined plane. 
 
 The object of this is to get the strings to press 
 against the bridge x, so that by varying the height 
 of the bridge the period of vibration of the coil may 
 be altered. The same object may, however, be more 
 simply obtained by the arrangement shown in fig. 
 
 27, which is likely to be adopted in future. There 
 the bridge is made double and consists of two pins, 
 x x and x 2 fixed relatively to one another, but capable 
 of being raised or lowered jointly. The strings pass 
 in front of x x and behind x 2 , and the inclined plane 
 and guides are done away with altogether, the 
 weights being allowed to hang free. 
 
 B 
 
 The following tables, giving the specific gravity 
 and electrical conductivity of solutions of sulphate of 
 zinc and sulphate of copper, are taken from a paper in the Trans¬ 
 actions of the Royal Society of Edinburgh for 1873, by Dr J. G. 
 MacGregor and the writer. 
 
 The “ Specific resistance ” means the resistance to conduction 
 between opposite faces of a cubic centimetre of the solution. 
 
 When solutions of sulphate of zinc and sulphate of copper are 
 mixed in equal volumes, the resistance of the mixture is always 
 less than the mean resistance of the components, being in many 
 cases less than that of either. 
 
 I 
 
 A 
 
 v 
 
 x, 
 
 X, 
 
 X 
 
 ur 
 
 Fig. 27. 
 
 E 
 
66 
 
 Sulphate of Zinc (ZnS0 4 , 7H.>0.) 
 
 Ratio of Salt to Water 
 in Solution. 
 
 Specific Gravity 
 at 10° C. 
 
 Specific Resistance 
 at 10° C., 
 
 Ohms. 
 
 1 
 
 to 40 
 
 • 
 
 1-0140 
 
 182-9 
 
 1 
 
 »> 
 
 30 
 
 1-0187 
 
 140-5 
 
 1 
 
 
 20 
 
 1-0278 
 
 111*1 
 
 1 
 
 a 
 
 10 
 
 1-0540 
 
 63*8 
 
 1 
 
 
 7 
 
 1-0760 
 
 50-8 
 
 1 
 
 
 5 
 
 1-1019 
 
 42-1 
 
 1 
 
 
 3 ‘ 
 
 1-1582 
 
 33-7 
 
 1 
 
 
 2-5 
 
 1-1845 
 
 32-1 
 
 1 
 
 » 
 
 2 
 
 1*2186 
 
 30-3 
 
 1 
 
 
 1*626 
 
 1*2562 
 
 29-2 
 
 1 
 
 
 1*5 
 
 1-2709 
 
 28*5 
 
 1 
 
 )> 
 
 1-37 
 
 1*2891 
 
 f 28-3 
 \ Minimum 
 
 1 
 
 a 
 
 1-361 
 
 1-2895 
 
 28*5 
 
 1 
 
 ff 
 
 1*3 
 
 1-2987 
 
 28-7 
 
 1 
 
 ff 
 
 1-124 
 
 1*3288 
 
 29*2 
 
 1 
 
 
 1 
 
 1*3530 
 
 31-0 
 
 1 
 
 ff 
 
 0-8 
 
 1*4053 
 
 32*1 
 
 1 
 
 ff 
 
 0-763 
 
 1-4174 
 
 33*4 
 
 1 
 
 „ 0-752 1 
 
 Saturated j" 
 
 1-4220 
 
 i 
 
 33-7 
 
 Sulphate of Copper (CuS0 4 , 5H 2 0.) 
 
 Ratio of Salt to Water 
 in Solution. 
 
 Specific Gravity 
 at 10° C. 
 
 Specific Resistance 
 at 10° C., 
 
 Ohms. 
 
 1 to 40 
 
 1*0167 
 
 I 
 
 164-4 
 
 1 „ 30 
 
 1-0216 
 
 134-8 
 
 1 „ 20 
 
 1-0318 
 
 98-7 
 
 1 „ 10 
 
 1*0622 
 
 59-0 
 
 1 „ 7 
 
 1-0858 
 
 473 
 
 1 „ 5 
 
 1-1174 
 
 38*1 
 
 1 „ 4-146 
 
 1-1386 
 
 35*0 
 
 1 „ * 
 
 1-1432 
 
 34*1 
 
 1 „ 3-297 
 
 1-1679 
 
 31*7 
 
 1 „ 3 
 
 1-1823 
 
 30-6 
 
 1 „ 2-597 1 
 
 Saturated j 
 
 1-2051 
 
 29-3 
 
 1