History of the Atlantic Cable & Undersea Communications
|Papers Presented at the British Association
Annual Meeting, 22-29 September 1858, Leeds
Introduction: Edward O.W. Whitehouse, “Wildman Whitehouse” as he generally styled himself, was a surgeon by profession and an electrical experimenter by avocation. In 1856 he was appointed Electrician to the Atlantic Telegraph Company and was responsible for the testing of the 1857/58 cables, and for the design and operation of the equipment which would transmit the telegraph signals between Ireland and Newfoundland.
Following the failure of the cable and his dismissal by the Atlantic Telegraph Company on August 17th 1858, Whitehouse made a series of presentations at the annual meeting of the British Association in Leeds, 22-29 September 1858. The text of those papers is reproduced here as reported in the Civil Engineer and Architect's Journal, Volume Twenty-First, 1858.
The titles are:
BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE.
Proceedings Of Various Sections.
Contributions on the Submarine Telegraph.
The instruments made use of may be classed under the following heads:—1, the batteries; 2, the induction coils; 3, the manipulator, or transmitting apparatus; 4, the relays and instruments employed to receive the signals, including a new reflecting galvanometer by Prof. Thomson; 5, and last, the apparatus for recording by electro-chemical decomposition.
The battery employed consists of platinised graphite, or retort coke, and zinc of large surface, excited in the usual way; 8 to 12 cells being used as may be required.
The coils are used in pairs, and consist of large hollow iron cores, 5 feet in length, and each wound with the following lengths of copper wire:—first, with about 11,000 yards of No. 20 gauge silk-covered copper wire, for a secondary circuit, insulated with wax paper between the layers, and hermetically enclosed in gutta-percha. And over this a primary circuit of thick wire, No. 14, consisting of 24 parallel circuits of about 100 yards.
The key or transmitting apparatus consists mainly of a large commutator, or current reverser, kept in constant motion by a train of wheels, and giving regular alternate primary currents to excite the coils; and by mechanical arrangement and simultaneous action the shocks from the secondary circuit are sent int» the line, and would thus produce a regular succession of marks or dots at the distant station.
Two ivory studs for hand manipulation and control are so mechanically arranged and connected that the tender may, without in any way interfering with the generating part of the commutator, convert these signals into dashes or pauses at will, by the mechanism connected therewith for modifying or entirely diverting or short-circuiting the secondary currents.
4. The relays, &c. The currents thus generated and controlled are received at the distant end upon a galvanometer or relay, so constructed and connected with a local printing battery as that every movement shall record itself, by means of a steel style, upon a slip of electro-chemical paper kept in constant motion.
The first signals and messages received from Newfoundland were worked off by them and received by us precisely in this manner, although even then, several days having elapsed since the laying of the cable, injury from exposure had begun to interfere with the currents.
Prof. Thomson's galvanometer being placed in circuit for the visible examination of the currents so printed, and showing their peculiarities very beautifully, I placed near the observer's hand a finger key, by which he might record the indications of this instrument by a second style on the identical strip of paper which we were using.
Satisfied with the accuracy of the instrument, and with the facility with which we could thus convert its visible signals into indelible records, on the further diminution of the strength of currents from increasing injury, I preferred it to the relay; more especially because, with feeble signals and a varying zero produced by terrestrial currents, it was capable of being more easily and more accurately used than any form of relay could possibly be. The eye could easily distinguish the alteration of the zero, and could as easily read off the signals with a constantly varying zero as with the most perfect steady one.
Since the final interruption of intercommunication they are still able to send us signals from their coils, which this instrument from its delicacy can distinctly appreciate; were this known to them at the time they might as easily send us actual words.
The fact of the fault being at this end impeded from the first to a much greater extent the transmission of our signals to them; we were very early obliged therefore to abandon the use of our special apparatus for speaking, and to rely upon voltaic currents of low tension, with contacts of long duration, in order to produce on their instruments any available signal. And even with this arrangement they were reduced to reading our despatches by movements of only half a degree upon their most sensitive detector.
Among the many difficulties experienced in the use of long submarine lines of telegraph, the process of testing for a fault constitutes not the least.
To ascertain the actual amount of loss of current upon any given length of cable, as compared with the whole battery force employed, is an easy process; but to determine by any examination made at one end, first, the existence of a fault; secondly, its degree or nature; and lastly, its position or distance from the operator, may be at times one of the most difficult problems in electro-telegraphic research.
The length of the line under examination of course must materially influence the question; for it must be obvious, that anything short of absolute perfection in each mile length, or at each joint, when multiplied by 2000 or 2500, would give in the aggregate a most striking and almost startling amount of loss.
It is this, perhaps, which introduces one of the most embarrassing features; for you are searching for a fault, the evidences of which are surrounded and masked by the aggregate effect of myriads of minute microscopic and unavoidable imperfections in the material of which the insulating medium consists.
This unavoidable loss necessarily enters as a disturbing element into all the results, and its amount varies with the temperature to which the cable is exposed.
The occurrence of a slight fault at a considerable distance will hardly make an appreciable difference in the amount of loss, while the same amount of injury close at hand may most readily be mistaken for a serious fault at a distance, to which indeed some of the evidences bear the strongest possible resemblance.
It admits, indeed, of demonstration experimentally, that upon a single mile of cable a variable fault, capable of accurate graduation by water resistance, can be made to assume all the features of a serious fault at any required distance—the features, that is, as recognised in the more usual methods of testing by resistance.
I would not be supposed to underrate for a moment the real value of this mode of research and examination, but there are conditions when I believe that the indications derived from it may lead to the formation of most erroneous opinions, which might wisely be guided and corrected by an appeal to another standard.
Suppose we have a cable of 100 miles in length; test it, and you find its insulation as perfect as may be; now, connect the distant end to earth—test again, and we have earth, with a resistance equal to 100 miles, taking the mile if you will as unity. Change once again, by disconnecting the further end from the earth, and by inserting instead at every mile a very minute fault, say a wetted thread, or very fine resisting wire of less than one-hundredth the conducting power of the cable; anything, in fact, so that the aggregate of their resistances or conductivity, together with the cable itself, equal the resistance in the previous experiment,—you again have earth, with a resistance equal to 100 miles.
It will be found impossible by the use of the mere resistance tests to distinguish between these two conditions of experiment.
It is under such circumstances that appeal may with advantage be made to another mode of testing, less frequently used, and of course known and introduced only since the discovery of gutta- percha. I mean the mode of ascertaining the state of insulation, by examining the capabilities of the cable to retain and give back a charge communicated to it, viewing it in fact in its special inductive function.
It will be found that the many minute points of defect spread over the line diminish the Leyden jar effect materially, by affording so many points of escape for the current. The defect at the distant end, on the other hand, allows the whole length of 100 miles to be charged up to a certain degree, and on disconnecting the home end from the battery, and instantly passing the discharge through any suitable instrument to earth, you receive and may measure the amount thus drawn from one half the length of cable, the remainder having discharged itself through the fault at the other end.
On the occurrence of the accident to the Atlantic cable last year, when nearly 400 miles were lost, I tested my resistance experiments by an appeal to this mode of examination, before I ventured to state my opinion that the end was either lost or its insulation entirely destroyed at that distance.
The unfortunate casualty to our cable of the present year was examined by me in this way, though necessarily very hastily; sufficient evidence, however, presented itself to satisfy me of the existence of loss upon the cable close at home, at the very time that the resistance experiments had determined its site at 600 miles distance. The matter was put to the test practically, by raising the end of the cable in the harbour, and upon little more than half a mile of it there was found to be more loss than I allowed to pass, if detected by the use of equal battery power, in 100 miles, at the Gutta-percha Works, during the process of its manufacture. On that occasion I expressed the opinion that the fault was but partially removed, and that "there was still more to come out." I have seen no reason to alter that opinion. I need not say more than to commend this subject to the attention of the practical telegraphists connected with submarine telegraphy.
The trial of a new form of alphabet proposed by Prof. Thomson for use on the Atlantic line, introduced me to the most striking and most embarrassing instance which I have seen of variations in the velocity of the same form of current, under circumstances which would appear at first sight to present like conditions.
The proposed form of alphabet required that every letter should consist of three, and but three currents, these being alternately of opposite polarities. The successive signals were to differ from each other in length or duration, as 2, 3, and 4 interchangeably,—those units representing half-seconds. The signals were to be recorded by relay printing every current on electrochemical paper; and from an arbitrary signal the whole were to be divided into triplets to denote the letters. There was found to be from the first no little difficulty in reading those signals, even upon so short a length as 1200 miles, though the manipulation might be perfectly accurate, and in true time with the beats of a metronome, and there was no certainty that the dispatch could be deciphered. This arose not from any difficulty about the form of alphabet, but from the indefinite length of many of the signals: they did not come out accurately as the hand had sent them.
A longer length of cable was tried, and the result was such as to lead to the utmost confusion of signals. When the symbols 2 3 4, 2 3 4, 2 3 4, were sent, the signals would be received as 3 2 4, 3 2 4, 3 2 4. This transposition of numbers perplexed me sorely for some time, and it was accompanied by a different error in almost every combination.
I was enabled at length to trace it to the different velocities with which similar currents will travel under conditions differing only as regards the previous state of the wire. Thus a current thrown into an uncharged wire travels with its normal velocity; while a current in all respects similar, if thrown into a wire just previously charged with the opposite force, is notably retarded, and travels with an appreciably lessened speed.
Now the brief magneto-electric current employed, when used to indicate the prolonged 4-signal, had of course double the time allowed in which to discharge itself that the shorter 2-signal had; any signal therefore next immediately following a 2, found a relatively full wire, while that following a 4 came into a relatively empty wire, and the instant of arrival of such signal was altered accordingly.
Another fact conspired to make this apparent anomaly even greater; it was that the duration of the contact with the primary battery used to excite the induction coils being variable, produced varying amounts of magnetisation in the iron of the coils, and of course generated secondary currents of varying force: thus during the long contact maintained for the 4-signal, while the cable was getting more fully discharged, the iron of the induction coils was becoming more highly excited, and generated of course at the next reversal a stronger current ready for the more rapid traversing the empty wire. The converse of this took place with the shorter contacts, and thus the confusion was complete.
The same phenomenon manifested itself to a certain degree in the use of the form of alphabet at present adopted, though in this instance it was hardly of consequence, because the primary contacts are always of equal duration, and the relative lengths of dot and dash being as 1 to 3, is such as to prevent their ever being mistaken for each other.
It did manifest itself however, and in a very curious way. Whenever the manipulation was approaching the limit of highest speed the cable would admit of, the first dot in an A would be blended with the dash, while the first of the three dots in a B would be absent altogether, and with similar imperfections in other letters. This was traceable entirely to the varying velocities of successive currents, conditions being in all other respects alike, save that of the immediately antecedent state of the cable.
This difficulty was removed at once upon adopting a system of antecedent compensation, by sending into the cable after every long signal, be it dash or pause, a small amount of current immediately in anticipation of the succeeding signal, sufficient to assimilate the charged condition of the cable to that which obtains after the use of the other short signals.
This system of antecedent compensation, which admits of graduation to any required degree, has removed every trace of the embarrassment before alluded to; and it has been most gratifying to me to see the waves of electric force, after traversing the Atlantic from Newfoundland, represented so beautifully by reflection from the mirror of Prof. Thomson's galvanometer, and to be able to recognise as it were the very features of my friends, these antecedent wavelets depicted by a ray of light, and to read off as I did by its aid those glorious words—" Peace on earth: good-will towards men," passing each way through the wire from end to end, and repeated back to us from the distant station, without error literal or instrumental.
I take it as indisputable that for overground telegraphs the size of the conductor stretched from post to post need be limited only by considerations of convenience and expense,—it cannot well, electrically speaking, be too large.
In submarine circuits other questions arise,—the difficulty of perfectly insulating a conductor is of course increased in proportion to the extent of surface to be covered, while the augmentation of the internal surface of gutta-percha increases the dimensions of the Leyden jar to be charged.
In circuits of moderate length these are matters of little moment, as the shortest contact practically used in telegraphing fills the wire from end to end with a continuous current, ana the special embarrassment arising from induction is inconsiderable and unnoticed.
When however the length of the cable is much greater, the amount of dynamic electricity assuming the static form, and thus consumed on the way, is much larger; and this loss takes place increasingly along the whole line, so that if the sectional area of the wire hid been fairly proportioned to the amount of current entering, it must, before the wave of force reach the other end, become largely disproportioned thereto.
In an ordinary non-inductive conductor this would give rise to no embarrassment or loss; but when the already enfeebled current has still to continue at every mile charging the surface of an unnecessarily large conductor, it is conceivable—it is even, I believe, demonstrable—that an unnecessary waste of power ensues, and increased retardation is observed. I have records of some experiments where such an effect was noticed in a remarkable degree, though allowance moat be made for some of the conditions which were anomalous.
A cable of given length, containing six insulated wires, afforded the opportunity of making so many variations in the size, and equally in the surface of the conductor employed; of course, as long as this was made to convey a continuous current, the conducting power of the arrangement was simply proportioned to the sectional area; but when signals at brief intervals were employed with intermissions and reversals, the loss in amount of current received, and the retardation observed, augmented largely with the use of additional conducting wires.
These observations arrested my attention most forcibly at the time, and from having let fall an opinion that I thought it possible that a submarine conductor might be too large for practical use, it has been erroneously supposed and stated that I held the converse opinion.
I have not seen the subject fairly worked out by any one under this aspect, and I merely suggest that the induction to which submarine conductors are necessarily subjected removes the question from the sole operation of those simple laws which regulate the usages of other conductors, and introduces a new element into the calculation, the value and force of which I do not find fully recognised.
My assistant, Mr. Samuel Phillips, suggested to me at that time the idea of a conductor (working one way only), being tapered so as to accurately represent the sectional area of the current, if I may so express myself, in every stage of its progress; an idea which is I think well worthy of attentive consideration.
I have had some lengths of cable made, the sizes of whose conductors for extreme experiment are related as one to a hundred: present leisure from the engrossing details of official duties will, hope, afford me the opportunity of examining this subject experimentally.
A particular juncture in the manufacture of the Atlantic cable at Greenwich afforded the opportunity of making some observations on the effect of temperature, in a very satisfactory manner.
Being early in May, the days were bright, with clear still sunshine, while the nights were cold and almost frosty. A new length of cable was begun at this time, and as it passed through the composition, which strongly blackened its surface, was laid out in the open air, and raised from the earth by thick deal boards.
It was therefore in a condition, during the manufacture of the first layer, the most favourable for observation of the effect of any change of temperature which the weather might offer.
For several days this was made the subject of very close observation, and for thirty-six hours, during which the conditions seemed the most favourable, it was observed, and the results recorded every few minutes.
The company did not at that time possess a Daniel's battery of sufficient number of cells to produce any apparent loss in so short a length of perfectly insulated cable. I therefore used the ordinary zinc and copper couples, filled with sand or sawdust, moistened with dilute acid, in the usual way in number 500. Care was taken to maintain its greatest uniformity of action.
The loss was read off in degrees upon a horizontal galvanometer of great sensibility, and the degrees of deflection marked off on a vertical scale. The amount of force represented by those degrees can be determined and similarly laid out when the galvanometer shall have been properly examined and graduated for that purpose.
The temperature is also laid down on the same vertical scale, in degrees of Fahrenheit.
The effect even of a passing cloud upon the insulation could be noticed on the instrument. An obscuration of the sun for some minutes produced a fall of several degrees, while a few drops of rain, falling about noon, reduced the deflection from 70½ to 54½; and the deflections ranged altogether from 71 to 1½, with a temperature ranging between 74° in the sun, and 39½° at night
These observations were followed up by some experiments at the Gutta-percha Works, upon a length of 2000 yards of Atlantic cable, immersed in water of varying temperatures; the results were read off upon the same instrument, and fully confirmed this remarkable influence of temperature on the insulating power of gutta-percha.
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Last revised: 11 September, 2014