Although the Society of Telegraph Engineers is but five years old, having been founded in the year 1871 by Major Frank Bolton and Major Webber, R.E., it has taken a position for high scientific character and vigorous work second to no other body in London, and its conversaziones are perhaps the pleasantest and the most interesting to which men of science are invited.
The Society is a connecting link between the Institution of Civil Engineers on the one hand and the Physical Society on the other. Its papers embrace large operations which constructively belong to the domain of the civil engineer, such as the laying of cables, the working of railways, the blasting of rocks, and the improvement of manufactures, while technically they embrace principles of pure physical science depending upon the laws of magnetism and electricity, light, heat, sound, and chemical action. With three societies so intimately connected by the overlapping of their domains it is pleasant to record the cordial co-operation which exists between them, the Institution of Civil Engineers having from the first given to the new Society a home, and so much sympathy exists between the Society of Telegraph Engineers and the Physical Society that the fusion of the two into one has been several times proposed, and has been received with favour.
On Monday evening the President and Council of the Society of Telegraph Engineers entertained the members of the Society and a great number of distinguished visitors at a conversazione which was held in the ball-room at Willis’s Rooms, and it is not too much to say that owing to the energy and organisation of the acting secretary, Mr. Sivewright, and to the co-operation of men distinguished in every branch of electrical research, the collection of objects of scientific interest was as good, if not better, than those which have gone be fore, and which have made the soirées of the Society of Telegraph Engineers so proverbially attractive.
The President, Mr. Charles V. Walker, F.R.S., exhibited a most interesting series of specimens and original instruments, illustrative of the rise of the electric telegraph in connexion with the South. Eastern Railway from the year 184% to the present time. The first of this series was a set of thirty-six insulators for telegraph posts. The first telegraphs had no insulation, but were merely strung through metal eyes screwed into the posts; the next step was to wrap felt round the wire at the point of passing through the ring, This was followed by a ring of wood, through which the wire was threaded, having a groove round its circumference for binding it to the post. The next step was the employment of porcelain, which was the same shape as the last, and consequently had to be threaded from the end of the wire. This was next modified by a portion being cut away from the circumference to the centre, and this may be looked upon as the earliest type of modern insulators which have developed into many hundred forms.
Mr. Walker also exhibited the first piece of wire (No. 8 B.W.G.) covered with gutta-percha, this was in the year 1848, also the first lightning protector for telegraphs, which consists of two small brackets carrying brass balls and fixed upon a stand, so that the balls very nearly touch; each bracket is armed with a set of spikes, the points of which are directed towards, and are in close proximity to, a corresponding set of points upon the other bracket. By this arrangement, which may be taken as the type of many of the modern lightning protectors, the voltaic current has not sufficient tension to leap across the air space between the balls or the points, but has to traverse the coils of the instrument, while a spark of statical electricity leaps the air space and leaves the coils uninjured
In the same series was shown a curious recording instrument known as McCul1um’s globotype, which records signals passing through it by dropping pellets coloured black, white, or blue, corresponding to its three magnets respectively, into a zigzag groove closed in front by a sheet of glass, so that as the space enclosed between the glass and the groove becomes filled by the pellets running down, a sort of pattern is produced which records the number of signals that have passed through each magnet, and the order in which the magnets have been working. The release of the pellets from their hoppers is effected by a valve similar to that adopted in shot flasks, and which is actuated by the armature of its corresponding magnet.
Mr. Walker also exhibited the first time-signal commutator of 1852, and as a matter of popular historical interest the original time tables of the royal specials, as well as the signalling instruments employed on the occasion of the journey of the Princess Alexandra from Gravesend to London, on the 7th of March, 1863.
Passing to instruments in use at the present time upon the South-Eastern system, Mr. Walker showed in action a complete set of block-system instruments, including his beautiful “train describers” and double action repeaters, as well as the complete apparatus for electrical communication between passenger and guard and guard and engine-driver.
The Astronomer Royal contributed some interesting specimens of the photographic registers of the movements of the declination and horizontal force magnetometers, and of the earth-current galvanometers at the Royal Observatory, showing a remarkable correspondence existing between the magnetic and galvanic disturbances. The specimens were chosen so as to represent days upon which “magnetic storms” occurred as well as days of “magnetic calms.” Messrs. Siemens Brothers exhibited a splendid collection of self-recording instruments, including their registering sounders which are in use in the General Post Office.
The Western and Brazilian Telegraph Company exhibited Jamieson and King’s self-relieving grapnel for recovering and fishing up submarine cables. The special characteristic of this most ingenious invention lies in the fact that it slips a rock but holds a cable. Its form is that of an anchor of five flukes, which are hinged at their bases to its shaft, so as to be capable of doubling back when their points encounter an obstacle, such as a sunken rock; they are however kept in their normal position by a flat spiral spring acting against a plunger within the shaft, and which in its turn presses against the prolongations of the fluke arms, and keeps them in their places. If, however, a cable be hooked, it passes down to the base of the arms, as into an ordinary grapnel, and a set of supplementary spring catches make it doubly secure from slipping out again. This grapnel was illustrated on Monday evening by a working model, which could be dragged along the ground upon which were fixed obstructions of wood to represent rocks, and cords representing cables; its action was invariably satisfactory, and attracted much attention. A full size grapnel was shown, as well as large working drawings showing its construction.
Mr. Latimer Clark, who presided over the Society last year, showed his beautiful Thomson’s reflecting galvanometer, which by being fitted with very perfect optical apparatus and a perfectly plane reflecting mirror silvered on its front surface, is capable of projecting upon a screen 50ft. off a sharply defined image of the aperture of the illuminating apparatus, whether that aperture be in the form of an elaborately cut arrow, a slit, a lenticular form, or a wire stretched across a hole. For lecture purposes this fine instrument is unrivalled; the range of its scale is only limited by the size of the room, and at a distance of 50 ft. a displacement of its needle through 1 deg. of azimuth is represented by a movement of the spot of light through 10½ in. from its zero point. The coils of this galvanometer are wound with about 1150 turns of No. 22 copper wire in two parallel circuits, and has a resistance of four ohms.
Sir William Thomson exhibited his new form of mariner’s compass, with his method and appliances for adjustment. This instrument was described in these columns a short time ago. Also the very beautiful irrepressible liquid gyrostat, which he described at the meeting of the British Association, and which created much amusement by its persistence in fighting against difficulties and appearing as if animated by a living intelligence.
Mr. Robert Sabine showed his beautifully worked-out apparatus for measuring very minute intervals of time. It depends for its principle upon the law that when a charged body accumulator or condenser is discharged steadily, the rate at which its electricity is neutralised is a definite one, depending upon the resistance of the circuit through which the discharge takes place, that is to say,-that if a certain percentage of discharge or leakage take place through the circuit during one second, the same percentage of the residual charge will be neutralised during the next second, and so on, until equilibrium be established. Mr. Sabine’s apparatus, by measuring the fall of charge in a condenser after a momentary contact, renders it possible to determine intervals of time of one-thousandth part of a second. As an illustration a small anvil was connected with one side of a charged condenser, while a light hammer was connected with the other side of it through a known resistance. When the hammer was struck sharply on the anvil it necessarily rested on the anvil for a minute fraction of a second before rebounding, during which time a certain percentage of the charge in the condenser leaked away through the resistance, and the residual charge of the condenser was discharged through the galvanometer. The falling off in the charge due to the leakage during the contact of hammer and anvil enabled the duration of that contact to be determined with extraordinary precision.
Mr. Sabine also showed his apparatus and method for determining the contour and speed of waves in telegraph lines; and he exhibits a very beautiful series of experiments, due, we believe, to the late Sir Charles Wheatstone, for showing the circulation set up in mercury partly by deoxidation and partly by variations in the surface tension of the mercury when influenced by voltaic. currents varying in direction. Upon this principle is based Professor Dewar’s electrometer, which was exhibited by Messrs. Tisley and Spiller, by whom it is constructed. It consists of two glass vessels containing mercury, upon which floats sulphuric acid diluted in the proportion of 1 to 15. These vessels are connected by a horizontal siphon-tube dipping into them, and which is filled with mercury with the exception of a small globule of the same acid solution, which serves as an index, and traverses from one end of the horizontal tube to the other. Upon connecting the mercury in one vessel with one terminal of an electro-motor, and the other vessel with the other terminal, a difference of surface tension is established at the two ends of the electrolytic globule, oxygen being disengaged at one end and hydrogen at the other, and these differences each tend to move the globule in the same direction, so that it moves along the tube, which is graduated to record its displacement. If the current be reversed, the index moves in the opposite direction. This instrument is of considerable sensitiveness, and for the lecture table is especially convenient.
Messrs. Cecil and Leonard Wray exhibited their new form of thermo-pile and an improved form of Reis’s telephone. The thermo-pile is an improvement upon Clamond’s, which was described in this journal some months ago. The elements are the same as those of Clamond, but the connexions are made in such a way that the fracture of a bar does not stop the current. The principal improvement, however, consists in supporting the sets of bars upon a fixed framework of porcelain fireclay, instead of upon rings as in Clamond’s, where one layer of elements has to support all above it, rendering the pile liable to tumble to pieces through either the lower bars becoming bro en, or the rings, which are composed of asbestos and silicate of potash, crumbling away.
Messrs. Wray’s improvement upon Reis’s telephone, a description of which will be found on another page,-f consists in giving to the transmitting instrument a second vibrating membrane, so as to protect the transmitting membrane from the action of the breath and other disturbing influences. The receiving instrument is also somewhat different; the soft iron bar is in two parts, each of which is surrounded by a magnetic helix and placed end to end with reversed poles, so that not only do they produce a tick or sound of doubled intensity, but by tending to pull against one another the sound is increased by a strain produced on the sounding box to which they are fixed. Any note sung into the transmitter, however feebly, was instantly repeated by the bar, and so sensitive is this apparatus that it reproduced the beats of the contact breaker of an induction coil at the further end of the great hall whenever the latter was working.
The Electric Writing Company exhibited Mr. Edison’s electric pen and specimens of the work done by it. Our readers may remember that a description of this instrument recently appeared in these columns. Near the entrance was a fine collection of instruments for the measurement of electrical resistances constructed by Messrs. Elliott Brothers, exhibiting all the scientific accuracy and beauty of workmanship for which that firm has so great a name, and to which the late Mr. Becker so largely contributed.
Mr. Apps had a brilliant display, including a fine induction coil giving 20 in. sparks in air and illuminating some fine specimens of vacuum and fluorescent tubes. Mr. Apps also showed a large block of optical glass pierced and split by spark from the great induction coil which he has recently completed for Mr. William Spottiswoode, F.R.S., and which is capable of giving a lightning flash 48 in. in length!
Faraday’s magnificent classical experiment of the rotation of the plane of a polarised beam of light under the influence of magnetism was well shown by Mr. Ladd with a fine diamagnetic apparatus.
As an example of what may be done by delicate manipulation and beautiful machinery we may cite samples of silk-covered wires exhibited by Mr. Walter Hall, some of which being not more than two-thousandths of an inch in diameter.
Mr. Spagnoletti exhibited a very interesting collection of railway signalling apparatus, including an electric semaphore signal which has been in use upon the Metropolitan Railway for upwards of twelve months, and which, although of the full size adopted on that railway, was worked with but six cells of battery.
Messrs. Montefiore showed in action their autokinetic telegraph, which may be described as a system for the laying on of electricity “from the main”—like the water or the gas in domestic houses and public institutions. By this system any private dwelling can be in instant communication with the nearest fire engine station, the police, a cab-stand, or a hospital. The transmitting instrument consists of a small plate carrying four buttons. By touching the first a signal is sent to the central station, which indicates the position of the house; a second gives an alarm of fire; by touching a third a medical man is telegraphed for, and the fourth is set apart for giving notice to the police that burglars are in the house. By combining these four signals other messages may be transmitted.
This year’s conversazione of the Society of Telegraph Engineers will long be remembered as an exceptionally brilliant one, and we must congratulate the President and Council and Mr. Sivewright upon its success.
We may add that a selection of excellent music was performed by the band of the Royal Engineers, and contributed not a little to the enjoyment of the visitors.