H.M.S. " Agamemnon"' in Lat. 54" N., Long. 30° \V., on 21st June 1858 (sec p. 44). (After the painting by Henry Cliftbrd. ) " ' " "-Mi?^^''^- ■ T^^^^E^P Wi.- ^I^^^^^^^^^H^SlRm^^a'^tflHHSB^DB^^Ii^^^'^' ''^' ' •' ■■' .*? • ; < ¥:^!l'^i^i1HiH^^^^H^ai H^HBlv''^Mn^"!!1l \ /Hi'' lilM^-..^1^ » -- 1 , -.T'**^ '■ --^fi' \ ■""■««**«!:'■- -V. M H.M.S. "Agamemnon" entering Doulus Bay, Valentia, Ireland, at J a.m., 5lh August 1858 (see pp. 47, 48), thus completing th2 successful laying of the First Atlantic Cable. (After the painting by Henry ClifToril.) I \- m t ii.l'GRAf'IIS 1|V^ ' .tion, nm mon'iWQ vA/r/- '1/ ■'■Jr>.v .1 /. ' ^'"^ ft r <. . i I I .K.S.H. {) it)] N h S ( .) N ! ; ■ M t f" , ^'* J. ■A. \ V -r *S 1 » "*'' 'k *<4 Vv*, ' V. •i^ 6^ •>• iji Submarine Telegraphs ^heir Ibistoi^, Conatructlon, ant> Morfiina FjUXDKP IX PART O.V IVCWSCllEiVDORFF'S ^ TkAITE DE T^LjiGRAPI/lE SOU.S ■ MaK/NE' ANU '' ■• ^^•.■:- >■/.''.- Compiled from AvriioRiTATirE a.vp Exci.rsn'E Sources BY CHARLES BRICxHT, F.R.S.E. ASSOCIATE MEMHER <>P THK INSTITUTION OP CIMl. ENCilNEEKS MEMIIEK or THE INSTITUTION OR MECHANICAL KNGINKEKS .ME.MI11:k op THE INSTITI'TION Ol" ELECTRICAL ENIHNPERS t LONDON CROSBY LOCKWOOD AND SON 7, STATIONERS' HALL COURT, LUDUATP: HILL 1898 Printed at The Dakiin Prkss, Mristo Place, Edinburgh. ■^^^^ ir nirii-i- . 1- :■' .?MPf * oou .., .,.:,i:.,!^. ,.!,,, ^g^ For many a fathom gleams and moves and moans The tide that sweeps above Nor where they sleep shall moon or sunlight shine, Nor man look down for ever And over them, while death and life shall be, The light and sound and darkness of the sea. Swinburne : Tristram of Lyonnesse. PREFACE. "hinu; had its orii(in in ;i schcine {or an J-'nulish •ui \Vin'sch«'iuK)til s laijiivi'- an.i alinost classic, > rail' lelegr.iphy.* ■ !jfi, however, that — owin.i; to the lapse of time and it would be impossible ro deal vviiii the • 1 brinj^ it up to date, vvithin tlie confines of a >'!>;._ (')UrsC ! IkTv'c ;l,'!()j.)IC'!, I'ir- I lnr(>, }-i;4S 1")peTl t'J i'l'i-'p- '; i;>L— i)ai(l\ l)as(:i.l '.r. .1 j. i t,.,ii d M, Wiin- ■'chend< ■(.jx though of ec]uai, i>' net greater, length I- ! asp'jcls ot >iiijauirine 'l\.'ie;^rai)hy. tnoug;, >;; fiH'.ch us coulvi be (loiif justice to at 'jnipletel^ . ; ...loptcvi iv.rc. I he thr'; ,,)r our present tlieme are — (1) IS n- ' tri!.. -■.■■t'liiai. ■•■'■■ de , . lanoe,' by K. Wunschftulorff, M.I.E.K., ;. "oit'ur df ki Region de I'aris (IJaiuln' ef Cie, Paris, PREFACE. The present volume had its origin in a scheme for an English revision of Monsieur Wunschendorff's famous, and almost classic, work on Submarine Telegraphy.* I soon found, however, that — owing to the lapse of time and other circumstances — it would be impossible to deal with the entire treatise, and bring it up to date, within the confines of a single cover. The course I have adopted, therefore, has been to prepare a fresh treatise — partly based on a portion of M. Wiin- schendorff's. The scope — though of equal, if not greater, length — is restricted to three of the five Parts which, in touching on the fringe of the subject generally, were so admirably and systematically put together by that author, from the available literature and data — the former mainly consisting of early papers dealing with the different aspects of Submarine Telegraphy. It is thought that this is as much as could be done justice to at all completely on the lines adopted here. The three titles selected for our present theme are — (i) * "Traits de Telegraphic Sous-Marine," by E. Wiinscliendorff, M.I.E.E., Directeur-Ingenieur de Tel^graphes de la Region de Paris (Baudry et Cie, Paris, 1888). X PREFACE. History, (2) Construction, and (3) Working, of Submarine Tele- graphs. This choice was not made without reason. In the first place — strange as it may appear — notwithstanding the vast sums at present invested in Submarine Telegraphy (far more than in any other branch of electrical industry), nobody has yet attempted to present to the reader in book form an account of the various enterprises of this nature from the days of inception up to the present advanced period.* I venture to hope that this omission is, in some measure, made good in Part I. — to a great extent based on original and official documents hitherto unpublished. Here, the reader may observe that Submarine Telegraphy, like every- thing else, is the work of many hands. * Shortly before his death, the late Mr Willoughby Smith gave us an interesting narrative of his extensive experiences, under title "The Rise and Extension of Submarine Telegraphy " (London : J. S. Virtue and Co.), but this is more in the nature of an autobiography of that distinguished pioneer. Again, within the same month of the same year (1867), the late Mr Robert Sabine and Mr Edward Bright, M.Inst.C.E., brought out works on "The Electric Telegraph," treating the subject in its more general sense — the work of the latter author being a revision of one of I)r Lardner's now classic volumes entitled "The Museum of Science and Art." Both works are published from the same office as this book. Finally, Mr k. S. Culley has produced periodic editions of his excellent " Handbook of Practical Telegraphy " (London : Longmans, Clreen, and Co.) ; and Mr Cleorge Prescott's " Electricity and the Electric 'I'elegraph " (Spon) corresponds to this in the States. Preece and Sivewright's text-book of " Telegraphy " (Longmans) then completes the available book literature on the subject in its broadest phase ; but none of the latter can be said to be historical in the ordmary sense, except pevhaps " I^rdner and Bright"— and that only in a very general way up to the end of 1866. To turn to the future, it may be stated that a more detailed history of matters connected with the First Trans-Atlantic Cable than was possible here will be published very shortly in the "Life-Story of Sir Charles Tilston Bright, C.E., M.P." (London : Archibald Constable and Co.), wherein also will be found a fuller account of the Telegraph to India. PREFACE. Xi Of late it has been rather the custom to question the utility of history with reference to engineering in its various aspects ; but those who are inclined that way should remember that it is only by a study of what has been done before that the repetition of failures and wrong methods can be avoided.* In the historical digest here furnished, a reference will be found to the commercial and financial aspects of Submarine Telegraphy, as well as to the part played by those men of business who were so largely responsible for the success ultimately arrived at. It would be well if Science, Capital, and Labour were equally ready to admit each other's claims for recognition in all such great achievements. In this connection it may be stated here that there is a project afoot to commemorate the Jubilee of Submarine Telegraphy when it falls due in igoi.t In the preparation of this book, no pains have been spared to * A somewhat striking example of the way in which history is liable to repeat itself — especially when unrecorded — is the Statham and Whitehouse patent of 1856 for a return wire. Apparently this was taken out regardless of the fact that, previous to Steinheil's 1836 apparatus, all telegraphs were worked by a metallic circuit, Dr Watson's 1747 demonstration of the use of the earth having, it would seem, been forgotten. t The Executive Committee of the International Submarine Telegraph Memorial - formed in part to carry out this object, as well as to memorialise the leading part taken by the late Sir John Pender, G.C.M.G., in the cominercial development and extension of submarine telegraphy throughout the world — is composed as follows : — The Marquis of Tweeddale (Chairman), The Right Hon. Viscount Peel, Lord Kelvin, G.C.V.O., F.R.S., Lord Sackville Cecil, Sir Robert Herbert, G.C.B., Sir E re Shaw, K.C.B., Sir Albert J. Leppoc Cappel, K.C.LE., Mr J. C. Lamb, C.B., C.M.G. (H.M. Post Office), Mr W. S. Andrews, Mr W. H. Baines, Mr F. A. Bevan, Mr G. von Chauvin, Dr J. A. Fleming, F.R.S., Mr R. Kaye Gray, Dr John Hopkinson, F.R.S., Dr Alexander Muirhead, Mr John Newton, Mr F. C. C. Nielsen, Mr J. Denison Pender, Mr J. W. Swan, F.R.S., Mr J. H. Tritton, Mr E. M. Underdown, Q.C., The Editor of the Electrician, The President of the Institution of Civil Engineers (Sir J. Wolfe Barry, K.C.B., F.R.S.), xii PREFACE. give an accurate idea of the share taken by each in contributing to the foundation and perfection of this branch of electrical industry and engineering. According to my lights and to the best of my ability, strict impartiality has been studied by me in all personal matters, whether affecting the reputations and interests of private indivi- duals, or those of business firms and corporations. The same impartial attitude has been applied to nationality as to personality. This, I believe, will be admitted by any foreigner who peruses the book carefully, notwithstanding the obvious and necessary fact that it is addressed chieHy to English-speaking engineers and electricians, and deals with an industry which is at present almost entirely in the hands of British companies.* However patriotic the writer may be in his private sentiments, national prejudices are quite out of place in a work of this kind. Two of the accom- panying maps are purposely drawn up in French, partly because that is still the lingua franca of modern nations, and also as being official publications of the International Telegraph Bureau at Bern. A further point remains upon which it seems to me that I owe The President of the Institution of Electrical Engineers (Sir Henry Mance, C.I.E.), and the author. Mr (i. R. Neilson acts as Honorary Secretary. It may be mentioned here in passing that one of the Commemorative Honours conferred during the present jubilee year was the baronetcy of Sir James Pender, M.P., — in part a fitting tribute to the energies of his father. * For example, it has, of course, been impossible to include detailed descrip- tions of all the various Relay devices used on the extensive French land lines, which the English electrician in connection with submarine cable work is never likely to have occasion to use. Had space, however, permitted, it would have been interesting to describe and illustrate these at length if only on account of their entirely novel and ingenious character. They almost demand a booklet to themselves. I'REFACE. Xiil some explanation to my readers. I refer to the matter of repeti- tions in different parts of the book. Although from the purely literary standpoint these repetitions are certainly blemishes, I am inclined to think that their advantage for purposes of reference will be found more than counterbalancing. Research is con- siderably facilitated by enabling the student to readily find information on the special point he desires under various heads — possibly in one part of the book, possibly in another.* Again, an additional matter calling for explanation is the free use of the footnote system. This is partly to maintain a more easy sequence of sentences, and partly to avoid thrusting items of pure detail into the teeth of the not too inquiring reader. . No attempt is made here to give absolute recipes or up-to-date constants. Anything of the sort is purposely eschewed, the tech- nical portion of the book being only intended to give an insight into the leading principles involved in the art of submarine cable construction and working. Moreover, formulte. to be of any practical value, should be obtained at the individual factories at the time. Again, all reference tables, such as, strictly, only apply for a short period and under certain conditions, are conspicuous by their absence, on the ground of being misleading if not absolutely up-to-date, and unless they can be made to refer generally to all the materials known under the same name. A further reason for this is that there are already several pocket, and hand, books which profess to supply this class of information : appearing as they do at frequent intervals, there is some chance of the data being con- * Moreover, it is partly to meet the possible separation of these parts in any subsequent publication. Xiv I'REFACK. temporaneous, where the same could not possibly be hoped with a work of this character. For books of pure reference with tables, I commend the reader to the now somewhat classic " Clark and Sabine,"* besides " Munro and Jamieson"t of more recent date, and also Kempe's;}; " Pocket- Book." For many useful and instruc- tive articles connected with different phases of cable work, it is additionally suggested that he should peruse the early volumes of The Electrician and the Electrical Review (formerly the Tele- graphic J ournal\ as well as the Electrical Engineer of a later date. His attention is further called to the columns of the Engineer (at one time the only applied science periodical), and, moreover, to those of Engineering, more especially of a few years subsequently. Some of these are alluded to further in the body of this book. The parts of the subject which, for the present, are taken up here are those which have been less, if at all, dealt with by Mr Wilkinson and other recent authors, to whom I have referred the student for full particulars regarding the laying, § repairing, and testing of cables, with which branches of Submarine Telegraphy this volume only deals incidentally — and mainly, in Part I., from an historical standpoint — in quite a general way, as occasion requires in connection with the subjects proper of the book. I hope that the Index at the end will meet every requirement * " Electrical Tables and Formulae," by Latimer Clark and Robert Sabine (London : E. and F. N. Spon), (871. t " Electrical Rules and Tables," by John Munro and Andrew Jamieson, F.R.S.E., M.Inst.C.E. (London : Charles Grififin and Co., 12th edition, 1897). + " The Elecirical Engineer's Pocket-Book of Modern Rules, Formute, Tables, and Data," by H. R. Kempe, A.M.Inst.C.E. (Crosby Lockwood and Son, London), 2nd edition, 1892. § Besides particulars regarding submarine survey and sounding work. rUEKACE. XV for reference, no pains having been spared to render it in every sense complete and a fitting companion to a treatise of this character. Though naturally a more or less technical work, intended for the " cable-man," I have attempt ' in the course of it to present matter of general interest — i.e., of interest to a large reading public outside the confined circle of telegraph engineers and electricians. There has been no want of material to work on. The difficulty has rather been a superabundance, and the necessity of a severe sifting of evidence. The commencement and rapid development of the world's electric nerve system constitutes, without a doubt, one of the most marvellous characteristics of the Victorian Era. The laying of the first effective submarine cable (1851) was almost exactly con- temporaneous with the first great International Exhibition ; and telegraphy on Cooke and Wheatstone's electro-magnetic system dates back to the first few years of Queen Victoria's reign.* Thus the present year, in which we have been celebrating the sixtieth anniversary of Her Majesty's " Record Reign," seems to me a particularly suitable one for the appearance of a book like this. In conclusion, I desire to express my cordial thanks for the kind assistance I have received from many quarters in its prepara- tion. As already observed, a part of M. Wunschendorff's treatise — so carefully compiled and edited in French, albeit mainly from * " Introduction to the Catalogue of the Victorian Era Exhibition on Science and Engineering, 1837-97," by Charles Bright, F.R.S.E. xvi PREFACE. English sources — constitutes the original "stock" upon which I worked a large part of mine. I have, moieover, availed myself of a great many of the same blocks — some actually of French origin — for my illustrations. To M. Wunschendorft', therefore, I owe a debt of more than ordinary gratitude, and his connection with this volume is too intimate for me to include him in the ordinary catalogue of contributors of facts or ideas. Next to M. Wiinschendorff, my special thanks are due to Lieut. Anthony Thomson, R.N.R., C.B., in regard to the original scheme already referred to. The following gentlemen have been good enough to render me material assistance in various ways and in various departments of the subject: — The Right Hon. Lord Kelvin, G.C.V.O., LL.D., F.R.SS. (L. & E.); Sir Samuel Canning, M.Inst.C.E.; Mr W. H. Preece, C.B., F.R..S., M.Inst.C.E.; Mr Latimer Clark, F.R.S., M.Inst.C.E.; Mr Edward Bright, M.Inst.C.E.; Mr F. C. Webb, M.Inst.C.E.; Mr Henry Clifford, Mr H. A. C. Saunders, Prof. Andrew Jamieson, F.R.S.E., M.Inst.C.E.; Dr Alexander Muirhead, Mr Herbert Taylor, M.Inst.C.E.; Mr Alexander Siemens, M.Inst.C.E.; Mr R. Kay e Gray, M.Inst.C.E.; Mr W. Claude Johnson, M.Inst.C.E.; Mr F. R. Lucas, Mr Willoughby S. Smith, Mr Frank Jacob, Mr P. B. Delany, Mr Thomas Bolas, Mr W. R. Culley, and Mr Edward Stallibrass, Assoc.M.Inst.C.E. For information or assistance of another character 1 have also to thank: — Lord Sackville Cecil, Rear- Admiral Sir W. J. L. Wharton, K.C.B., F.R.S. (Hydrographer to the Admiralty); Sir Douglas Galton, K.C.B., D.C.L., LL.D., F.R.S. ; Sir C. L. Peel, K.C.B. ; Major-General Sir F. J. Goldsmid, K.C.S.I., C.B. ; PREFACi:. xvii Mr B. T. Ffinch, C.I.E.; Captain A. W. Stiffe. R.I.M.; Mr S. W. Silver. Mr W. S. Andrews, Mr W. Shuter, Mr J. Denison Pender, and Mr William O. Smith ; besides Mr Charlton J. Wollaston — one of the very earliest workers in the field — and Mr T. Hillas Crampton, the son of another. There are also others to whom I am indebted — mostly in connection with matters to which their names are attached in the body of the book. I desire, moreover, to express my gratitude for assistance rendered by the following Government Departments, Firms, and Companies:— H.M. Post Office, Admiralty, War Office, Foreign Office, Colonial Office. The Agents-General for the Colonies, India Office (Indo-European Telegraph Department), Patent Office, Messrs Clark, Forde, and Taylor, The Telegraph Construction and Maintenance Company, Messrs Siemens Brothers and Co., The India-rubber, Gutta-percha, and Telegraph Works Company, of Silvertown, W. T. Henley's Telegraph Works Company, Hooper's Telegraph and India-rubber Works, Messrs Dixon and Corbitt and R. S. Newall and Co., Messrs Johnson and Phillips, Messrs Easton, Anderson, and Goolden, Messrs Frost Brothers, Messrs Brown, Lenox, and Co., Messrs Elliott Brothers, and Mr James White ; also to the Anglo-American Telegraph Company, The Eastern Telegraph Company, The "Eastern-Extension" Tele- graph Company, The Eastern and South African Telegraph Company, The Direct United States Cable Company, The Western Union Telegraph Company, The Great Northern Telegraph Company, The Brazilian Submarine Telegraph Com- pany, The Western and Brazilian Telegraph Company, The Xviii rREFACE. Central and South American Telejj^raph Company, The West India and Panama Telegraph Company, and the South American Cable Company. Further, I am especially indebted to my brother, Mr J. Brailsford Bright, M.A., of the Inner Temple, for legal and general advice, assistance, etc., partly in regard to the various patents connected with th^i subject. I also take this opportunity of thanking the Publishers, and Mr R. M. Johns, of the Middle Temple, for their valuable and earnest co-operation. Last — but by no means least — I wish to record my thanks to Mr C. R. Wylie for the design on the cover of this volume. In fully acknowledging assistance rendered to me in divers ways with willing and unstinting hands, I desire to state that the entire responsibility for all defects or errors must rest with myself. CHARLES BRIGHT. 53 West Cromwell Road, London, S.W. December 1897. P.S. — It should be understood that the term "projected " in the Map facing; page 208 does not include lines which have been discussed, but which, so far, have not taken definite shape. Recent events seem, however, to point towards the principal Powers being brought into direct and independent telegraphic communication with their individual Colonies. CONTENTS. t PAGE LISTS OF ILLUSTRATIONS -.'-.-. xxvi, xxvii INTRODUCTION xxxi PART I.— THE HISTORY OF SUBMARINE TELEGRAPHS. CHAPTER I. EARLY SUBAQUEOUS TELEGRAPHY. Section i. — E.>cperimental Telegraphs across Rivers, etc., by Aldini, Sommer- ing, Schilling, and Sharpe — Accomplishments by Pasley and O'Shaughnessy — Wheatstone's Suggested Scheme — Work by Morse, Cornell, West, Arm- strong, and Werner Siemens — Walker's Experiment off Dover, 1849 - - i Section 2.— Brett's Negotiations for an Anglo-French Telegraph— The First Dover-Calais (Unprotected Core) Line, 1850 — The First Effective Submarine Cable, 185 1 — Anglo-Irish Line — Anglo-Dutch and Anglo-German Cables- Denmark to Sweden ...-..-. 5 Skction 3. — Mediterranean Cables— Black Sea Unprotected Core Line - - 16 CHAPTER n. THE DAWN OF OCEAN TELEGRAPHY. Section i.— Prospects — Experiments — New York and Newfoundland Company — Newfoundland Land Line— Gulf of St Lawrence CalSIe, 1855 and 1856 — "Telegraph Plateau" — Raising of Capital — Construction of the Cable — Ships Employed for Laying — Paying-out Machinery — Setting out on First Expedi- tion, 1857 — Landing of Shore End at Valehtia — Accidents during Laying by the "Niagara" — Return of Expedition— Storage at Keyham — Extra Length Manufactured— Improved Paying-out Gear — Improved Electrical Apparatus — Paying-out Trials in Bay of Biscay — Second Expedition — Mid-ocean Splice —Laying by Two Ships towards each Shore — Landing of Cable at Newfound- land End— Landing at Irish End — Successful Completion — First Message — Public Rejoicings m Both Countries— Gradual Failing of Insulation — High Transmitting Power Employed -Engineering Success in face of Scientific and Public Opinion — Knighthood for Mr Charles Bright — Wild Suggestions - 23 XX CONTKNTS. Section 2. -Red Sea Telegiaph, 1859 -Chatterton's Compound— Tight Laying,' Had Bottom -Successive Failure of each Section - - - 57 Section 3.- Hoard of Trade Commission on Construction of Submarine Cable, 1859-61 59 Section 4. —Formulation of Electrical Standards and Units by British Associa- tion ..------- 61 Section 5. Malta to Alexandria Line Testinjf under Pressure Spontaneous Combustion due to Alternate Wet and Dry Conditions— Laying of Sections -Successful Working- -Balearic Cables Submergence in Deep Water — Mediterranean Lines Wright's Cable Siemens' Light Type I'aying-out Dynamometer- Failures --...-- 62 Telegraph to India — Persian (iulf Cables — Segmental Conductor — Organised System of Testing at Factory -Tanned Jute Serving — Bright and Clark's Compound— Laying from Sailing Ships— Complete and Lasting Success .......--- 73 CHAPTER III. DKVELOl'MKNTS. Section i. - Renewed Attempts at Trans-Atlantic Telegraphy— Scientific Com- mittee-Electrical Qualifications for Speed — Raising of Capital— Contractors • — Type of Cable- -Electrical and Pressure Tests — Construction and Shipment — S.S "Great Eastern "Paying-out Machinery— StafT -Landing Shore End at Valentia— Laying— Misfortunes — Core Pierced by Broken Sheathing Wires— Attempts at Recovery- Return of the Expedition - - 78 Preparations for a Fresh Attempt — "Floating" of "Anglo-American" Company — New Cablp- Alterations made in the Picking-up and Paying-out Gear — Willoughby Smith's Testing System— Use of Signalling Condensers- Staff and others accompanying Expedition — Landing Shore End at Valentia — Laying — Fouls in Tank during Paying out — Arrival of "Great Eastern" in Trinity Bay, Newfoundland — Landing Shore End at Heart's Content — Successful Completion — Rejoicings - - - - - - 91 Recovery and Completion of the 1865 Cable — Plan of Campaign — Failures — Success at Last — Paying-out towards Newfoundland— Another Broken Sheathing Wire causing Fault and Foul — Completion of Line— Honours Be- stowed — Instance of Navigating Skill displayed by Captain Moriarty — Elec- trical Condition of the Two Cables — Speed of Working — Subsequent Failures 99 Section 2. — Anglo-Mediterranean (1868) Direct Cable from Malta to Alexandria — F"rench Atlantic, i869^British-Indian Line — British-Indian Extension — British-Australian — Marseilles, Algiers, and Malta — Falmouth, Gibraltar, and Malta — Indo-European Line— Great Northern System— West India and Panama Cables— Cuba Submarine — Direct Spanish— Formation of Eastern and Eastern Extension Telegraph Companies — Black Sea Line— Submarine Cables Trust — Globe Telegraph and Trust Company — Duplex Telegraphy applied to Cables — Brazilian Submarine Line — Western and Brazilian — Central American — Platino Braziliera — Amazon River Cables — D.U.S. "Atlantic" — West Coast of America — Eastern and South African— " P.Q." Atlantic — Jay Gould Cables — Mexican Cables — Central and South American — Pacific and European — Spanish National— West African — African Direct — Commercial (Mackay-Bennett) Atlantics — Italian Government Cables of Pirelli— French Cables in West Indies, North Coast of South America, and elsewhere — Halifax and Bermudas Line — South American Cable Company's Trans-Atlantic System— Azores Cable— New Caledonia (French) Line— New "Commercial" and "Anglo" Atlantics, 1894 -Atlantic Cable Systems — General Retrospect ........ 106 CONTENTS. xxi CHAPTER IV. COMMERCIAL AND MISCELLANEOUS RltSUM^. Si.CTlON I.— The Proposed Trans- Pacific Line: Engineering Problems : Financial Prospects: Tariff: Political Utility: National, Imperial, and Strategic Aspects • - - - - - - - - -146 Skction 2.— Total Length of Cable Submerged and Monefary Equiv.ilent as com- pared with Land Telegraphs of the World - - - - '53 Skction 3. — Engineers and Contractors — Bright and Clark : Gisborne and Forde : Thomson and Jenkin : Canning and Sabine : Clark, Forde, and Taylor — R. S. Newal! and Co. : Glass, Elliot, and Co. : Telegraph Construc- tion and Maintenance Comp.iny : Siemens and Halske : Siemens Brothers : S. \V. .Silver and Co.: India-rubber, Gutta-percha, and Telegraph Works Company : Mr W. T. Henley : The Hooper Company— Johnson and Phillips -Elliott Brothers - - - - - - - - 154 Section 4.— Telegmph Ships— "Silvertown" : "Faraday": "Scotia" - - 161 Section 5. — Miscellaneous Figures and Estimates — Initial Cost and Life of a C.-ible — Maintenance— Renewal Fund — Repairs and Duplications— Number of Messages Conveyed — Time occupied now ,ind previously — Code Messages —Earning Capacity — Revenue — Value as an Investment — Submarine Tele- graphs opening up a Country — "Eastern" and Allied Companies' Jubilee and Retrospect ......... 163 Skction 6.— Comparative Effects of Railways and Telegraphs on Civilisation — Revolution in Methods of Diplomacy — Strategic Standpoint — Influence on Commerce — Difference of Time limiting the Hours of Communication with Distant Points — English Financial Pioneers — Mr He...iiker Heaton's Pro- posed Reforms — Influence on the Press : Dissemination of News in times of War, etc. ..-------- 169 Section 7. — Business Systems — Codes : Effect on Number and Length of Messages — International Administr.ition : Bern Bureau — Subjects for Con- sideration : Landing Rights : Shore-End Protection — Official Telegraph Map —(}reat Safety of Cables in Deep Water - - - - - '75 Section 8. — Founders of the Society of Telegraph Engineers — Early Papers concerning .Submarine Telegraphy— Institution of Civil Engineers — Institu- tion of Mechanical Engineers — Early Articles in the Tdegraphic Journal and The Electrician - - - - - - - - - 180 Section 9.— Inductive Telegraphy— Past and Future .... 184 APPENDICES. 1. Submarine Telegraphs under H.M. Post Office - - • '93 II. Submarine Telephony ....... 201 XXll CONTENTS. PART II.— THE CONSTRUCTION OF SUBMARINE TELEGRAPHS. CHAPTER I. THE CONDUCTOR. PAGB Section i.— Copper: Electrical Conductivity: Physical Properties: Different Species: Electrical Tests : Formuhe and Data: Influence of Temperature : Suggested Substitutes - - - - - - - - 214 Section 2. — The Conducting Wire : its Form— Different Types compared Electri- cally and Mechanically : Leading Principles — Initial Tests - - - 227 Strand Manufacture : Machine for Laying up Wires : Length : Gauge : Lay- Rate of Work ..-..-..- 236 CHAPTER H. THE INSULATING ENVELOPE. Section i. — Early Methods of Insulation in the First Underground Lines : Glass Tubes, Cotton, Pitch, Tar, and Resin : India-rubber and Gutta-percha - 243 Section 2.— Gutta-percha : Where and How Obtained : Historical Data regard- ing its Discovery, (General Uses, and Electrical Application — Collection and Preparation : Classification : Importation . . - . . 248 Section 3. — Chemical, Physical, Mechanical, and Electrical Properties of Guttj^- percha : Favourable and Unfavourable Conditions — General Electrical Formuhe — Effect of Pressure : Effect of Temperature : Ageing Effect — Diameter and Weight ........ 262 Section 4. — Method of Purifying Gutta — First Stages on Collection and on Arrival at Cable Factory : Mastication : Straining : Calendering — Kate of Work - 285 Section 5. — Willoughby Smith's Gutta-percha— Nature and Effect of the Process — Data and Formuhu ........ 297 Section 6. — Manufacture of Core : Covering Conductor with Gutta-percha — Preliminary Re-Mastication — Principle of Gutta-percha Covering Machine : Gray's Machine — General Operation of Covering Wires with Gutta-percha : Cooling and Hardening Process : Examination of the Insulated Wires — Relative Advantages of Single and Multiple Coats : Siemens' Multiple-Die Machine — Weight of Insulation: Outside Diameter -Rate of Covering — Mechanical Tests : Electrical Tests — Standard Values : Records — Specifica- tion Requirements and Limits— -Siemens' Pressure Test — Localisation of Faults — Heavy Proportional Cost of Insulator . - - . - 299 Section 7. — India-rubber — Where and How Obtained — Method of Purification- Physical Characteristics — History of Electrical Application — Vulcanised Rubber — Historical Memoranda — Hooper's Core — Modern Practice of Vulcanised India-rubber Core Manufacture — Physical, Mechanical, and Electrical Data- -Deterioration ------- 332 Section 8. — Relative Merits of Gutta-percha and India-rubber - - - 348 Section 9. — Other Suggested Insulating Materials — Particulars of Alternatives : Advantages Claimed— Gutta-percha and India-rubber Combined — Failures — Main Requirements - - - - - - - - 35' CHAPTER in. JOINTING. Section i. — General Remarks and Intplements Used : Tools - - 356 CONTENTS. xxiii PAGE Skction 2.— Jointing the Conductor : Tin Soldering .... 360 Section 3.— Jointing the Insulation : Gutta-percha Cores - - - - 366 Section 4.— Jointing Vulcanised India-rubber Cores .... 375 CHAPIER IV. MECHANICAL PROTECTION AND STRENGTH. Section i.— Submarine Borers— History of Metal Tape— Present-day Applica- tion — Alternative Suggestions - - - - . . - 381 Section 2.— Inner Serving : Historical— Constitution of Jute— Tanned Jute Yarn- Routine of Inner Serving Application — Serving Machine — Lay of Inner Serving— Miscellaneous Particulars- Formulc-e, etc., for Weight of Inner Serving ---------- 391 Multiple - Conductor Cables : Where Desirable : Advantages and Dis- advantages- --------- 400 Sfxtion 3.— General Description of Ordinary Sheathing : Types - - - 403 Testing Iron Wire— Tension and Elongation Test : Torsion Test : Galvanising Test— Routine of Cable Sheathing— Rright and Clark's Com- pound— Compounding of each Iron Wire — Taping each Wire - - 413 Section 4.— Operation of Sheathing : Leading Principles Involved— Skeleton- Frame Machine : Disc Machine— Modern Improvements— Lay of Wires- Points in Construction— Formula for Weight of Iron in a Cable : Trial Specimens -------.. a-iq Sfxtion 5.— -Bright and Clark's Cold Compound— Outer Canvas Taping— Bright and Clark's Hot Compound— Cooling the Cable - Relative Merits of Outer Tape and Yarns : Outer Yarn Covering : Hemp Yarn Applied Externally : Jute Yarn Applied Externally : Outer Hemp Cords : External Canvas -Tape and Hemp Cords— Outer Covering : General Particulars- Hauling off Com- pleted Cable— Rate of Cable Manufacture - - . . . ^55 Skction 6.— External Whitewashing on Way to Cable Tank : Coiling into Tank- Testing during Manufacture- Stretch of Core during Sheathing - - 476 CHAPTER V. COMPLETED CABLE. Skction I.— Matters of Importance : Data necessary - - - . 480 Skction 2.— Mechanical Testing : Tensile Strength —Qualifications— Representa- tive Deep-sea Cable : Representative Shallow-water Cable— Specifications and Tests : Details of Construction : New Types— Cost of a Cable— Data and Records ---------- 484 Section 3.—" Light Cables "—Early Forms: Core without Sheathing: Allen's Cable : Siemens' Cable : Lucas' Cable— Requirements : Weak Features in Hemp and Iron Light Cables— Later Types of Hempen Cables— Trott and Hamilton Cable— Unlaying and Laying up of Turns in a Cable— Conditions regarding Hempen Cables— Light Sheathed Cables : Bright's Aluminium- bronze Sheathing ------... 4^4 APPENDICES. 1. Lkcal .Standard Wire Gauge - - - - . - 513 II. Si'kcification of Anglo-American Telegraph Co.'s Valentia— llKART'.s Content Cable, 1894 ------ 514 III. Post Office Specification of Anglo-German Cable, 1891 - - 516 IV. FoKMs FOR Electrical and Mechanical D.ata - - . /adn^ 522 XXIV CONTENTS. PART III.— THE WORKING OF SUBMARINE TELEGRAPHS. CHAPTER I. THEORY OF THE TRANSMISSION OF SIGNALS THROUGH CABLES. PACE Section i. — Preliminary Remarks ------- 525 Section 2. — Propagation of an Electric Impulse in a Cylindrical Conductor : " Curbed " Signals : The Application of Condensers for Signalling Purposes — Alphabets — The 1869 Atlantic Cable taken as an example - - - 528 Uearlove's Transformer for Working Cables — Mechanical Analogy of Cable Working - - - - - - - - - - 561 Section 3. — Signalling Speed ; Absolute Velocity of Electricity — Data in Tiuv-tice — Theoretical Calculations : Considerations involved : Latest Views — Further Practical Considerations and Comparisons ..... 566 CHAPTER n. SIGNALLING APPARATUS. Section i. — Introductory Remarks - - - - 581 Section 2. — Special Methods for Discharging Cables : Discharging Relays : Auxiliary Discharge Coils : Hughes' Printing Apparatus with Discharge : Brown-Allan Relay --.....- 584 Section 3 — Mirror Receiving Instrument : Suspended Coil Mirror - - 592 Station Installation : Transmitting Keys : Earth Connection : Arrangements for Re«.ording Messages at the Sending End : Saunders' Key — Crookes' Radiometer for Recording Mirror Signals as Received - - - - 596 Section 4.— Thomson Siphon Recorder : Electro- Magnet and Coil : Siphon : In- scription of Signals — Electric Mill — Vibrator — Later Patterns of Recorder 604 Installation of the Apparatus and its Connections at each End — Permanent Magnet Recorders : Direct Writers — lienjamin Smith's Switch Key and its Connections : Manual Translation : Raymond- Barker Translating Key — Dickenson's Transmitting Key and its Connections - - - - 619 Section 5. — Other similar Apparatus : Lauritzen's Undulator : The Dextrineur — Siemens' Permanent Magnet Relay : Ader Recorder - - - - 631 CONTENTS. XXV CHAPTER III. DUPLEX TELEGRAPHY. I'AGE .Skction I. — History— Differential Principle : Wheatstone Bridge Principle— Varley's Artificial Cable : Stearns' Method — De Sauty's Method - - 635 Skction 2. — Modern Practice : Muirhead's Inductive Resistance : Muirhead and Taylor's Method: "Double-Block" — Practical Examples and Installations: Duplex Directions for Short Circuits : Duplex Directions for Long Circuits- Comparison of the Principal Duplex Systems — Other Methods : Benjamin Smith's : Harwood's : Jacob's : Ailhaud's — Comparison of Varley's and Muir- head's Artificial Line — Siuiiles of Duplex Telegraphy . - - - 643 Quadruplex and Multiplex Experiments on Cables . - - - 661 CHAPTER IV. AUTOMATIC MACHINE TRANSMISSION. General Remarks — Belz-Brahic System — Taylor's Automatic Transmitter — Delany's System — Taylor and Dearlove's Automatic Curb Transmitter- VVilmot's Transmitter : Cuttriss' : Muirhead's Curb Transmitter : Muirhead and Saunders's Curb Transmitter : Price's Electrical Contact Apparatus for Transmitters — Advantages of Mechanical Transmissions — Application to Long Cables for High Speed Working ------ 662 CHAPTER V. RECENT DEVELOPMENTS. Sjxtion I. — Working-through Experiments : Delany's Relay and Sounder System : Delany's Repeating System : Long-Distance Overland Telegraphy : Muirhead's Automatic Morse Transmitter : Cable Relays : Dearlove's Auto- matic Puncher --------- 676 Section 2. — Phenomena in Long-Distance Cable Telegraphy : Leak Cable Circuits: Expe.. Opinions on "Leaks" - ----- 681 Section 3.— New Proposed Methods for Rapid Cable Signalling and Long- Distance Telephony — Silvanus Thompson's Proposed Cable : Preece's Cable : Smith and Granville's Cable : Barr and Phillips' Cable— Langdon-Davies' Phonopore — Munro and Bright's Telephone Recorder - - - - 685 Section 4. — "Wireless Telegraphy" — Lodge's Investigations : Marconi's Experi- ments : Tesla's Researches ....... 695 APPENDIX. "Recorder" Signals UNDER Varying Conditions - - - - 703 INDEX - 705 ( xxvi ) LIST OF CHARTS AND MAPS ILLUSTRATING SYSTEMS OF SUBMARINE TELEGRAPH COMMUNICATION. Chart shewing the intended Telegraphic Communication between England and km^x\ca. {x^t^b) [Reproduced from Origifuil] - - - - facing 30 Map shewing the West Indian Cable System and its Connections - - - 117 General European Connections of Atlantic Cables (from the Map published by the International Telegraph Bureau, Bern, 1897) - - - . facing 142 American Ends of Atlantic Cables (from the same Map) - - -facing 144 Cable System of the Eastern Telegraph Company and its Connections - - 154 English and Anglo-Continental Government Cables .... 194 The World's Telegraphic System (1897) .... facing 208 ( xxvii ) LIST OF ILLUSTRATIONS SUBMARINE TELEGRAPHY." Extra copies of the Chart (reproduced from the Original) showing the Projected Route (1856) of the First Atlantic Cable, which appears in this volume facing p. 30, and of the large Map of the World's Telegraphic System (1897), Mcing p. 208 {^witli or without the Projected Lines), may be obtained on application to the Publishers. Price 2S. 6d. ecuh Map. The number being limited, early application (with remittance) is desirable. ^ : : " U.S. rngate •magara, useu lur uiiyiiig luc rviictiuii. \,auic m loju - j« The Starting of the First Expedition from Valentia Bay, 6th August 1857 - - 38 Landing the Shore End of the First Atlantic Cable by S.S. "Willing Mind," at IJallycarberry, Caherciveen, Valentia Harbour, 5th August 1857 - - 39 Paying-out Machinery of First Atlantic Cable, 1858- - - -facing 42 Appold Krake (three illustrations) ---..-- 43 Frame for Mid-Ocean Splice of First Atlantic Cable, 1858 - - - - 45 Landing of the First Atlantic Cable in the Bay of Bull Arm, Trinity Bay, New- foundland, sth August 1858 ....... 46 Landing of the Cable from H.M.S. "Agamemnon" by boat at Knightstown, Valentia Island, on the Sth August 1858, thus Completing the First Trans- Atlantic Telegraph ........ 48 Facsimile of First Message " cabled " across the Atlantic - - - - 49 Underrunning Irish Shore End of First Atlantic Cable, i860 - - - 5J (xxvi) ( xxvii ) LIST OF ILLUSTRATIONS (EXCLUDING MINOR AND THEORETICAL DIAGRAMS). H.M.S. "Agamemnon" engaged in Laying th'e First Atlantic Cable (two illustra- tions) --....-.- frontispiece O'Shaughnessy's Line across the River Hugli, 1839 ----- 2 Wheatstone's proposed Telegraph Line between England and France, 1840 (two illustrations) ....--.. /,icing 4 Facsimile Copy of Letter submitted to Government in July 1845, as Printed by Brett's Electric T ;Iegraph ...... facing 6 Facsimile Copy (Reduced) of Certificate of Registration of the First Proposed Submarine Telegraph Company ------ faciniz 6 Laying of the First Channel Line, 1850 - - ... - 8 House and Brett's Type- Printing Telegraph - ..... 9 Dover-Calais Cable, 1 85 1 - - - - - - - - 11 Piece of 185 1 Channel Cable picked up in 1859 ----- 13 First Effective Anglo-Irish Cable, 1853 ...... 14 Shore End of Anglo-Dutch Cable, 1853 ...... 15 Reduced Facsimile of Cartoon from Punch (14th September 1850) : " Effect of the Submarine Telegraph ; or, Peace and Good-will between England and France " 22 Reduced Facsimile of Emblematic Picture of the Union of England and America by Atlantic Telegraphy, from the ^/i'/«A HwX'Wrt/;, 1858 - -facing 22 Deck of H.M.S. "Agamemnon," shewing Paying-out Apparatus, 1858 - - 23 Original Station of New York and Newfoundland Telegraph Company, 1855 28 Infusoria at the Bed of the Atlantic Ocean, magnified 10,000 times - - 29 First Atlantic Cable, 1857-58 -------- 33 Shjre-End Type ......... 34 U.S. Frigate " Niagara," used for Laying the Atlantic Cable of 1858 - - 36 The Starting of the First Expedition from Valentia Bay, 6th August 1857 - - 38 Landing the Shore End of the First Atlantic Cable by S.S. "Willing Mind," at Ballycarberry, Caherciveen, Valentia Harbour, 5th August 1857 - - 39 Paying-out Machinery of First Atlantic Cable, 1858- - - -facing 42 Appold Brake (three illustrations) -..-.-- 43 Frame for Mid-Ocean Splice of First Atlantic Cable, 1858 - - - - 45 Landing of the First Atlantic Cable in the Bay of Bull Arm, Trinity Bay, New- foundland, 5th August 1858 ....... 46 Landing of the Cable from H.M.S. "Agamemnon" by boat at Knightstown, Valentia Island, on the sth August 1858, thus Completing the First Trans- Atlantic Telegraph ........ 48 Facsimile of First Message " cabled " across the Atlantic - - - - 49 Underrunning Irish Shore End of First Atlantic Cable, i860 ... 51 XXVllI CONTENTS. i'A<;k Proposal to Buoy the Atlantic Cable at Interval Stations, for Ships to communicate from - - - - - - - - - -55 Telegraph House at Trinity Hay, Newfoundland, 1858 - - - - 56 Malta-Alexandria Main Cable ....... 62 Paying-out Apparatus for Oran-Cartagena Cable, 1864 - - - - 69 The Indo-European Telegraph : Landing the Cable in the Mud at Fao, Persian Oulf 73 Persian Gulf Cable (Main Type) ....... 76 S.S. " Great Eastern " ........ 79 Second Atlantic Cable (1865), Main Type -..:.. 83 Shore End of the 1865 Atlantic Cable ...... 85 Paying-out Machine, Atlantic Cables, 1865-66 ..... 86 Sketch Plans of S.S. "Great Eastern," containing Cable and Machinery, 1865-66 facing 86 Landing the Shore End of 1865 Atlantic Cable in Boats from S.S. "Caroline," off Foilhommerum Bay, Valenti?. Island ..... 88 Atlantic Cable, 1866 -...-.--- 92 Shore End of Atlantic Cable, 1866 ... - ... 93 General Arrangement of Paying-out Machinery at Stern of " Great Eastern," 1866 94 Picking-up Machine aboard "Great Eastern," 1866 - - - - facinj^ 94 Buoys, etc., used on Atlantic Expeditions of 1865-66 - - - 95 S..S. " Great Eastern " Approaching Heart's Content, Trinity Bay, in Completing the Laying of the 1866 Atlantic Cable ------ 98 S.S. "Great Eastern" Picking up the 1865 Atlantic Cable - - - facinti 100 Diagram Illustrative of the Final Method Adopted for Picking up 1865 Atlantic Cable .......... 101 S.S. "Great Eastern" at Night Bumping against Mark Buoy No. i, on Predicted Line of 1865 Cable, just after hooking it ..---- 103 .Sketch Plan of S.S. "Great Eastern "when last Employed as a Telegraph i^h\^ faciitff 130 Anglo-American Atlantic Cable, 1894, Ueep-Sea Type - - - - 141 Irish Shore End of 1894 "Anglo" Atlantic Cable - - - - - I44 Specimen of Cable Torn by an Anchor - - - - - - 180 Some Enemies of the Cable ..--.--. 190 A Piece of Deep-Sea Cable Covered with .Shells, etc. .... 190 Barnacles on a Cable - - - - - - - - 190 H.M. Telegraph Ship " Monarch" ----- - facinf; 196 Do. do. in Section and Plan (four illustrations) facing 196 Cable Machine, H.M.T.S. "Monarch" ...... 197 The London Paris Telephone Cable .--.--- 207 Eastern and Brazilian-Submarine Companies' Telegraph Station at Carcavellos, Lisbon - - - - - - - - - -213 Eastern Telegraph Company's Gibraltar Station ..... 226 Siemens' Solid-Strand Conductor .....-- 230 Stranding Machine .-.--.-. facing 236 Eastern Telegraph Company's Station at Platris, Cyprus, 3,200 feet above sea-level, connecting up the Commissariat and Ordnance Depots with the whole of the Telegraphic World ...-.--- 247 Foliage, Flower, and Fruit of the /f<>«rt« ;' ANY GIVEN POINT IN THE SHORTEST POSSIBLE TIME NECESSARY FOR THEIR CONVEYANCE THESE ABF SOME OF THE ADVANTAGES, OTHERS READILY SUGGEST THEMSELVFS NAMELY, GENERAL COMMUNICATION BETWEE.V STATIONS ON THE COAST. .SUCH AS LIGHT- HOUSES CHANNEL ISLANDS ETC, SO THAT A GENERAL SUPERVISION OF THE COAST-MJGHTs.BE OBTAINED FOR THE USE OF THE NAVY. LLOYD** AND FOR THE PREVENTION OF SMUGGLING, KTC . A«t^ t,r, mr. SIGNED. , , J. AND J.W. BRET'! , NO :> . HANOVER SaUAH" OF WHlCH^I^^Tr'^^^^Ht'2^r?*^S^!:iiSv.^'''^^''«'^ PRINTING TELEGRAPH' THAT PRINTS- Xilni»Fr?^TcuI"^Kr^^II'fP-^ ■^'*" ORIGINATOR IS THE ONLY ONE ALi TH? oafECTS ^aUlRFD v T "^r'^i^-^'^Lr"! ^"*^ TIME i-V ONE WIRE ONLY. ^^ PAPER*^"^^iTI„i!^'^^;^^^". j:i.^h.t^^)«i« i^;^^^ Hi^I^.''^ PF.HMANENT,.Y Facsimile Copy (Reduced) of Original Letter. \Tofacep. 6. I [Plate IV. ^o.M4- CERTIFICATE OF PROVISIONAL REGISTRATION of t^ep'^^r.g^ /^^^^^>. ,y^y^j 4^^^/. > Company Pursuant to the Act 7 & 8 Vict., c. 110. / in 1859. bottom, strong currents, and disturbance from anchors experienced in these waters. This undertaking is mainly remarkable, on account of it being the only attempt to do without any intermediate serving between the insulated conductor (made by the Gutta-percha Company) and the sheathing. The conductor was composed of a single wire of No. 16 gauge. This was covered with gutta-percha to gauge No. 2, the completed core being closed with twelve No. 12 galvanised iron wires. A few miles from each shore the cable had larger iron wires— about No. 6— so that this was the first cable with shore ends in the ordinary sen.se as now adopted. Messrs R. S. Newall and Co. undertook the carrying out of the above work. On it was also engaged Mr Henry Woodhouse. At that time they did not test * The vitality displayed by this early line was very remarkable. The last piece in circuit was a 40-yards length on the beach at Sangatte. This was only cut out quite a short tune ago, and a new shore end laid. M s u n M A K I N I', r 1-: i , i;< ; k a r 1 1 s. the cable under xvater prior to beiiijj laid. Tims, wlien it had been siib- mcrjfed but a few days, the insulation proved to be so bad that si^^nals could not be made to pass, and all efforts to pick u|) and repair the cable were unavailinj;. .V A second attempt was made between Portpatrick and Dona^^hadee, the cable consisting of a central copper conductor, covered, first with india- rubber, then with gutta-percha, and hemp outside all. The cable, being far too light, was actually carried awaj' by the strong tidal currents and even broken into pieces during laying. The undertaking had, therefore, to be abandoned. The third ei leavour was made between the same two points for the Magnetic Telegraph Company, with a cable of a similar character to that successfully adopted by Mr Crampton in the cable he had recently laid from England to France, but containing six conductors. Unfavourable weather was ex- perienced, and the arrangements for checking and paying out .so heavy a type being inadequate, more cable was expended than had been allowed for by the engineers, so that there was not sufficient to reach the opposite coast. What the fate of submarine telegraphy would have been had these three failures pre- ceded the establishment of the line between Dover and Calais may be readily surmised. However, in 1853, a heavy cable (F"ig. 10), weighing .seven tons per mile, with six conductors, was successfully laid in upwards of 180 fathoms* across the Irish Channel, between Portpatrick (Scotland) and Donaghadee (Ireland), for the Magnetic Company, of which the late Sir Charles Hright was engineer, with permanent success, establi.shing communication with Ireland for the first time telegraphically. Only a year elapsed before it became evident that another cable was required to meet the traffic between England and the Continent, and in 1853 an additional line was laid — this time to connect us with Belgium — from Dover to 0.stend. This was a heavy multiple cable, similar to that laid between Dover and Calais in 1 851, but embracing six conductors instead of fount Fic. 10. — First Effective Anglo Irish Cal)le, 1853. * This was the deepest water in which a cable was laid for some time — i.e., up till the date of the Spezia-Corsica line in 300 fathoms and over. t In his "Museum of Science and Art," published in 1854, Dr Lardner says, with reference to this undertaking ;—" The ne.\t great enterprise of this kind, of which the accomplishment must render for ever memorable the age we have the good fortune to EAki.v suha(,)Up:()Us and suhmarink tki.kgraphy. 15 Anglo-Dutch and An^jlo-Gcrman cables followed in due course ; and in less than ten years from the commencement of its operations, the Sub- marine Telegraph ('omi)any was working at least half-a-dozcn excellent Kic. II.— Shore End of Anglo-Dutch Cal)le, 1853. cables ranging from 2$ to 117 miles in length, connecting England with live in, was the deposition in the bed of the Channel of a like cable cmnecting the coasts of England and Belgium, measuring 70 >;it'Us in one unbroken le j.,', ! This colossal rope of metal and gutta-percha was also constructed at the worki. of Messrs Newall." l6 SUBMARINE TELEGRAPHS. the Continent. That the business was highly profitable there is no doubt whatever ; and knowing what we now do about cable work the risk was inconsiderable. But it appeared to be far greater in those days, and much praise is due to the courage and energy of the directors of the company, who certainly, by these .Anglo-Continental cables, paved and led the way to the greater enterprises which have resulted in submarine telegraphy throughout the whole world. In 1853 the International Telegraph Company determined to lay cables to Holland and elsewhere. Afterwards, when amalgamated with the Electric Telegraph Company, they fitted out a ship for the first time in a permanent fashion for cable operations. This was the old " Monarch,"* 500 tons, which did much useful work, and whose early gear was designed by the late Mr Kdwin Clark and Mr F. C. Webb as engineers to the company. England and Holland were connected bj' seven small separate cables, which were bound up together at the landing ])laces (Orfordness, on the Suffolk coast, and The Hague) so as to form .shore ends (Fig. i i). The.se were repeatedly broken by anchors and trawlers, being far too light, and were replaced by a heavy cable in 1858. f Section 3. — Further Early Achievements. During the next few years submarine communication was established between Denmark and Sweden; Italy, Corsica, and Sardinia; Sardinia and Africa; and, finally, between Ireland and North America. Of the.se numerous lines we shall only concern ourselves with those which, by the importance of results obtained, or by the degree of difficult}- overcome, mark a stage in the history of submarine telegraphy. Spezia-Corsica and Sardinia-Bona Cables.* — These two cables, in * A striking picture of this vessel is given in Mr H. D. Wilkinson's recent book, "Submarine Cable Laying and Repairing" {The Electrician Printing and Publishing Company, London). + For a given amount of telegrapliic work, the relative merits of a number of separate cables of light type, each holding its own conductor, and of the same total number of conductors encased in one heavy " multiiiie " cable, may be summed up as follows; — The former are more prone to fracture or abrasion, but total interruption of traffic is less liable to occur here than by the multiple core, especiall> if in the former the separate cables are laid on different routes. With a very rough, irregular bottom subject to anchorage and stormy currents, a fairly heavy cable is, however, practically essential, and this being so, it may as well contain more than one conductor. Some form of multiple-conductor cable is, in fact, the invariable custom for short distances involving telegraphic inter-communication of the " heavy traffic " order. % This was the first undertaking with which Messrs (llass, Elliot, and Co. were concerned, as a firm, after taking over the business of Messrs W. Kiiper and Co. They had been more or less associated since 1851, when Mr Kiiper came over from Ciermany, and manufactured several of the early cables, more especially those just referred to. KARLV SUHA(iUKOUS AND SUBMARINE TELEGRAPHY. IJ conjunction with a short submarine line between Corsica and Sardinia, and the aerial lines across the two islands, were to connect France with its colony Algeria via Italy. The cable laid from Spczia, and also the one acro.ss the Strait of lionifacio, contained six conductors each, and were sheathed with twelve (ungalvanised) iron wires of No. i gauge, bringing the total weight of each to as much as eight tons per nautical mile. The depth of water between Corsica and Genoa being over 300 fathoms, Mr J. W. Hrett was provided with two drums (Fig. 12), furnished with double sets of flanges, and placed in a line, one in front of the other, and round each of which the cable was given five turns. With this description of holding-back gear, and with the assistance of .Mr John Thompson, Mr Ikett was able to lay the first of the above two cables— 100 N.M.* — in the course of the year 1854. With this, however, the cable took charge in some 300 fathoms, about midway ; running out with such velocity under the strain that it was bent nearly flat as it pas.sed round the brake drum. After anchoring by it for a day, the injured part was hauled back and made good. Flc. 12. — I'aying-out Apparatus for Mediterranean Cables, 1854. Shortly afterwards, an attem])t was made to pay out a similar type of cable between Bona and Chia, near Cagliari. ]?ut between these points — distant about 150 N.M. — there arc depths of 1,600 to 1,800 fathoms, and the cable, which they were unable to restrain, ran out at a terrific speed. Added to this, the small steamer " Tartar," towing the vessel which had the cable on board, could go no faster, so that the impo.ssibility of reaching Sardinia with the remaining cable soon became api)arent. The paying out had been suspended, as was then customary, during the night, and they were deliberating as to what should be done, when the cable suddenly parted. It was passed out through a hawse pipe, sustaining a .sharp nip as it hung down at right angles, and, being unprotected against chafing, * Throughout this work N.^l. and "naut" are the abbreviations adopted for nautical miles. Hy some the expression "knot" is used in this sense, but inaccurately so. .\ knot is a velocity, or rate, ratlicr than a measure of distance. I knot= i nautical mile (N.M.) |)cr hour; i nautical mile (N.M.)=^2,o29 yards— or apjjroximately 1,000 fathoms— for tc-ieKraph work; I statute land mile (.S.M.) = 1,760 yards. Unfortunately, such high authorities as Raper and Norric have given currency to this misnomer by speaking of "knots " for nautical miles. l8 SUBMARINE TELKGKArilS. the pitching motion of the ship had caused the wires to gradually wear away at a point. In 1858, under the direction of Mr Charles Liddell,* the "Elba" succeeded in picking up about 60 miles of this cable from Bona sea- wards, and thus the possibility of recovering and repairing a somewhat heavy cable, laid in comparatively deep water, was practically demon- strated. On .starting to make a .second attempt, the expedition steered more in the direction of Galita Island, following a line where previous .soundings shewed more moderate depths. During the night, however, they deviated considerabl)' from the proper track, thus wasting cable, and at daylight found themselves off Galita, in 400 fathoms, unable to reach the island for want cf cable. The end was passed forward outside the ship and properly secured, a ve.s.sel being immediately despatched to Bona for a buoy. At the .same time they telegraj^hed through to London asking that sufficient cable to reach the shore might be sent out. Unfortunatel)-, however, on the fifth day, the cable parted, the continuous pitching and sheering of the vessel causing it to chafe through on the rocky bottom. ]\Ir Brett having retired from the enterpri.se, Mr R. S. Newall took it up in 1857, and manufactured a cable with four conductors, each consisting of four co]jpcr wires laid up together, coxercd with two coatings of gutta- percha. These insulated conductors were embedded in hemp,+ and the whole sheathed with iron wires of No. i i B.W.G. for the deep-sea tj'pc, and with twelve iron wires of No. 6 B.W.G. for those portions of the cable which were to be laid near the land. The weight of the deep-sea cable was 1.85 tons, and that of the heavier tj'pe 3 tons, to the mile. The cable was coiled below the deck in a cj-lindrical iron tank, from the centre of which rose a sort of cone (Fig. 13), .secured to the bottom of the tank, but free all round at its up|jcr end. Four rings of iron piping were suspended by ropes in a horizontal position round the cone. These rings were of different diameters, largest at the bottom and successivel)- smaller towards the top. The cable was guided and controlled fagainst flying out by centrifugal force) by passing up between these rings and the central cone, being thus forced to uncoil uniformly and horizontally without kinking. The two lower rings — one of which is shewn — were lowered from time to time as the quantity of cable in the tank diminished, the bottom one being kept pretty close to the coil to keep the outer turns in paying out from ♦ This gentleman and Professor L.ewis Clordon were partners with Mr R. S. Newall. + In those days the description "hemp" or " ordinary hemp " seems to have been commonly applied to what, at the present time, we should term /u/e. EARLY SUKA()Ui:()US AND SUBMARINE TELEGRAPHY. 19 rising in too direct a line to the ej'C of the tank. From the preceding, it will be seen that Mr Newall was the originator of the rings, or so-called "crinolines," forming a part, in some shape or another, of the fittings of all cable tanks, provided for the purpose of regulating and directing the cable's egress from its resting-place.* The cable passed up out of the tank through a small horizontal ring placed centrally o\er the axis of the cone, and then through a casting screwed above, whence it ran along a wooden trough f which was supported on trestles. l^attens were placed across the trough at intervals, to prevent the cable jumping up when being paid out rapidlj-. The cable then passed between two flanged rollers, placed one over the other, and again between two pieces of wood shod on the inside with iron, the upper piece being hinged at one end. A long lever I'k;. 13. — Xewall's Cone ami Rings fur Calile Tank. attached to the hinged piece enabled pressure to be exerted on the cable, which could thus be held as in the jaws of a vice. Thence the cable passed over a V-wheel I to the payingout drum, round which it took .seven turns — the first turn being kept over towards the outer flange of the drum l)y pa.ssing over a conical roller, and a knife § attached to the framework forced the turns inwards and prevented them riding. After leaving the * This device had formed the subject of a patent in 1855. + The friction which the cable exerts against the sides and bottom of this open trough assists the brakes in preventing too rapid egress from the ship. + A V-whecl, or sheave, is an article peculiar to cable work, Iia\ ing a deeper groove thaii an ordinary U-puUey, so as to form an extra safe bed and guide for the cable. S The term knife, as invariably adopted, is rather misapplied here. It would be more accurate to describe it as a/,r/ or shW, the object being to " tieet " the cable on the drum-/.<., to press the cable over, so that it makes way for the fresh turn, to prevent the latter riding immediately over the previous one, as it would tend to otherwise. 20 SUHMAKINE TKLEGKAl'HS. drum, the cable passed over another V-sheave and under a jockey wheel forming a sort of dynamometer into the sea, over a cast-iron flanged pulley at the stern of the vessel. The brake, intended to check the speed of the cable when paying out, consisted of a strong stra]) of sheet-iron four inches wide, which surrounded the entire circumference of a brake wheel bolted on one side of the drum. By means of a bent lever this iron band could be tightened up or slackened at will, so as to cause more or less friction between it and the revolving drum. At the last moment, on the advice of Mr ^afterwards Dr) Werner Siemens, the above form of dynamometer was fitted up and placed between the paying-out drum and the stern of the vessel. It consisted of a flanged pulley resting on the cable and revolving at the after end of a wooden lever, the other end of which was pivoted. Noting the deflection of the cable caused by the weight of the pulley, the strain coukl be deduced by a single calculation. To prevent undue heating by friction, a stream of water was kept playing on the cable froin a tank placed above the drum and fed by a pump. On the 7th of September 1857, the end of the cable was brought ashore at Fort Genoa. Here it was firmly secured to two j)osts fi.xed in the bottom of the trench which had been previously dug out to a depth of three feet. At one of these posts the cable end was joined uji direct to the aerial line in communication with the fort. l"p to this date the necessity of lightning guards between an aerial line and a cable, to protect the latter from lightning convej-ed from the land line, docs not appear to have forcibly commended itself At - more than a third, a change of the ship's course was decided on in order to make Cape Tculada, and the speed increased to si.x knots. In s|)ite of these precautions, the cable had all run out when the ship was still 13 mile.s from the land ; but, the depth here being only 80 fathoms, the laying was continued the next day by joining on a small single conductor cable, which, however, broke, unfortunately, about two miles' distance from the shore. In the course of the following October the end of the main cable was picked up, KARLY SUBA(2UEOU.S AND SUBMARINE TKLKCRAPHY. 21 and a new piece of similar type spliced on, with which the shore was reached, near C'ape Spartivento.* Electrical apparatus had been set up on board the " I'Llba," in order to enable a constant test to be kept on the cable for continuity during the laying operations. Mr Siemens also made some apjjroximate measure- ments of the time occupied by the current in passing from one end of the cable to the other, as well as on the inductive influence of a wire on neighbouring conductors. These effects were found tcj disajj]jcar when a return wire was used .so as to effect a metallic circuit.+ By only two of the conductors were good signals ever transmitted, and these two failefl in as many years' time.* In i860 Mr Jcnkin, afterwards I'rofes.sor Flceming Jcnkin, F.R..S. (L. & E.), picked up altogether about 57 miles of this cable, half on the African and half on the Sardinian side. A portion of the recovered cable came up full of kinks, due to the e.xcess of slack paid out. He was, however, unable to reach the fault, and the work had to be abandoned. Black Sea Cable. — Following the Spezia cable in 1855, a gutta-percha covered wire, No. 16 copper covered to No. i gauge, was laid§ in the Black Sea, by Mr Charles Liddell, in engineering charge on behalf of Messrs Newall, between Varna and Balaclava, for use during the Crimean War. It was, however, sheathed with iron wires for about 10 miles out from each landing- place. It was when fitting out for this expedition that Mr Newall had first introduced the arrangement of central cone and iron rings, which has already been described. This line, some 300 miles in length, was laid with very little slack. Communication through it cea.sed a .short while after the taking of Sebastopol, and no efforts were made to restore it. * .\ land line was afterwards established from Cape .Spartivento to Cagliari, partly in order to bring this cable into direct communication with that to Malta laid stibsctiuently. t In 1856 Mr Samuel Statham and Mr Wildman Whitehouse had actually secured |)rovisional protection (specification No. 1,726 of that year) for the use of a. return wire, liioiigh this was originally the custom until .Steinheil put Dr Watson's " metallic circuit" into practice ! No doubt Messrs Statham and Whitehouse had these inductive influences and earth currents in mind when they abandoned using the earth as a "return." I Mr Siemens estimated the speed of the current in passing from Cape Spartivento to Hona as being at the rate of 0.25 seconds, t'.i:, he found it took each signal impulse that time to reach to the further end. S Crcat trouble was experienced in this owing to the length falling short, the (omparative lightness causing it to be drawn away out of its direct course. In the open sea (subject to strong currents and boisterous water), it would probably have been absolutely impossible to lay a line of this character except by using a length far beyond that represented by the distance covered. 22 SUBMARINK TKI.KGKAI'IIS. The Sardinia-Malta and Malta-Corfu Cables. — Tliesc two cables, each about 500 miles long, and weighing 18 cwt. per naiit, were laid in 1857, onlj- lasting for a verj- short time, being far too light for the locaiit)'. The Sardinia-Malta section, repaired for the first time in 1859, failed about six weeks afterwards in much the same place. l'"urther attempts were made to repair it, but when five months had elapsed the operations were abandoned. The bottom was verj- une\en, and both breakdowns were attributed to \olcanic action ; they were, however, more probabh' caused b\- fishermen's trawls. The Malta-Corfu section ceased working in 1861, during a heavy thunderstorm, although protected by a lightning guard. The tests shewed want of continuit)- in the conductor, and the fault .seemed to be about 20 miles from Corfu. Some ]jarts of the cable were afterwards picked U|i, and found to be in a good state of preservation. From Punch; or, The London Charivari, 14M .S'c//<'«;^«- 1850 (reduced yijc/m/Zf of carloon). EFFECT OK THE SUB.MAKINE TELEGRAPH ; or, PE.VCK AND GOOD-WILL BETWEEN ENGLAND AND FRANCE. ^i., ^iUr,4i'''^>^l''r,!j-rj'J TIIK ATLANTIC TELEC.RAPll CABLK WAS 5111 AUGUST 1858. SUCCESSFULLY LAID, Two mighty lands have shaken hands Across the deeii wide sea ; The world looks forward with new hope ( )f better times to he ; I'or, from our rocky headlands, Unto the distant West, Have sped the messages of love From kind ( )ld England's breast. And from America to us Hath come the glad re|ily, "We greet you from our heart of hearts, We hail the new-made tie ; We pledge again our loving troth Whicli under Heaven shall be As steadfast as Monadnoc's clifTs, And ileep as is the sea I " Henceforth the I'.ast and West are bound By a new link of love, And as to Xoah"s ark there came The olive-bearing dove. So doth this ocean telegraph, This marvel of our day, I ;ive hopeful promise that the tide or war shall ebb away. No more, as in the days of yore, Shall mountains keep apart. No longer oceans sunder wide The human heart from heart, for man hath grasped the thunderbolt, -\nd made of it a slave To do its errands o'er the land, And underneath the wave. Stretch (m, thou wonder-working wire 1 Stretch North, South, East and West, Deep down beneath the surging sea, High o'er the mountain's crest. .Stretch onwards without stop or stay, .Ml lands and oceans span. Knitting with firmer, closer lx>nds .Man to his brother man. .Stretch cm, still on, thou wondrous wire I Defying space and time. Of all the mighty works of man Thou art the most sublime. On thee, bright-eyed and joyous Peace, Her sweetest smile hath smiled, For, side l)y side, thou bring'st again The mother and the child. Stretch on '. < ) may a blessing rest Upon this wondrous deed, This conipiest where no tears are shed. In which no victims bleed ! May no rude storm disturb thy rest Nor (juench the swift-winged fire That comes and goes at our command Along thy wondrous wire. Long may'st thou bear the messages Of love from shore to shore, And aid all good men in the cause Of I lim whom we adore : For thou art truly but a gift Ity the All-bounteous given ; The minds that thought, the hands that wrought, Were all bestowed by Heaven. TAe British IVorknmn. Deck of H.M.S. " Aj;amemnon " (sec pp. 47, 48), shewing; I'aying-mit Apparatus, 1S58 (from the Itltistratcd London Ntws). CHAPTER II. THE DAWN OF OCEAN TELEGRATHY. SiX'TlON I. — I'rospects — Experiments — New York and Newfoundland Company -New- foundland Land Line — Gulf of St Lawrence Cable, 1855 and 1856 — "'rdegraph I'lateau" Raisin},^ of Capital— Construction of the Cable — .Ships Employed for Laying — I'ay- ing-out Machinery — Setting out on First Expedition, 1857 — Landing of Shore End at Wilentia - .'\ccidents during Laying by the "Niagara" — Return of f^xpedition — Storage at Keyham — Extra Length Manufactured — Improved Paying-out dear - Improved Electrical Apparatus — Paying-out Trials in Bay of Biscay — Second Expedition — Mid-ocean .Splice — Laying by Two Ships towards each Shore -Landing of Cable at Newfoundland End- Landing at Irish End — Successful Completion — First Message — Public Rejoicings in Both Countries — (iradual Failing of Insulation — High Transmi-tting Power Employed — Engineering .Success in face of .Scientific and Public Opinion — Knighthood for Mr Charles Bright — Wild Suggestions. SiXTlON 2.— Red Sea Telegraph, 1859 - Chatterton's Compound— Tight Laying— Bad Bottom — Successive Failure of each .Section. Skction 3. — Board of Trade Commission on Construction of Submarine Cable, 1S59-61. Si'.CTlON 4. — Formulation of Electrical .Standards and Units by British Association. Skction 5. — Malta to Alexandria Line— Testing under Pressure — Spontaneous Com- bustion due to Alternate Wet and Dry Conditions — Laying of Sections — Successful Working— Balearic Cables- Submergence in Deep Water- -Mediterranean Lines^ Wright's Cable -Siemens Light TyiJC- Paying-out Dynamometer -Failures. Telegraph to India— Persian Culf Cables — .Segmental Conductor — Organised System of Testing at Factory— Tanned Jute Serving — Bright and Clark's Com- pound—Laying from Sailing .Ships — Complete and Lasting Success. Section i.— Tiik J'irst Trans-Atlantic Line. IlrniEKTO the eftbrt-s of the early projectors of submarine telegraphy had boon confined to the work of connecting countries divided only by narrow seas, or establishing communication between points on the same seaboard. 24 SnniARIXK TKLKCIRAPIIS. The next step forward in the science of submarine telegraphy was a gigantic one — no less, in fact, than that of spanning the Atlantic Ocean between Europe and America. This was aptly characterised at the time, by I'rofessor Morse, as "the great feat of the century." It was the first venture in the direction of trans-oceanic telegraphy, so that there were no applicable data to go upon. The vast difference between laying comparatively short lengths of cable across rivers and bays, or in shallow water, and that of laying a long length of cable in depths of over two miles across an open ocean, will be evident alike to the sailor and the engineer.* During the year 1855, the North American telegraph lines had been extended as far as Newfoundland, while in lun-opc the wires of the ".Magnetic" Com])any had, .several years previously, been carried bj* their engineer, Charles Bright, to various jjoints on the west and south-west of Ireland, including Portrush, Sligo, Galway, Limerick, Tralee, and Cape Clear. The feasibility of uniting the two vast .systems of telegraphs had engaged the consideration of some of the most enterprising of those occupied in their development on both sides. It had been already proved that cables could be successfully laid in comparatively deep water; but the nearest points between the British Islands and Newfoundland are nearly 2,000 miles apart, and the greatest length of submarine line which had been successfully submerged prior to 1856 would form but an insignificant part of such an enormous distance, and that too embracing dejiths of nearly three miles. Apart from the engineering difficulties entailed by this vast distance and depth, the question was then undetermined as to the possibility of conveying electric currents through such a length in an unbroken circuit, and at a speed that would enable messages to be p.assed quickly enough in succession to prove remunerative. * The t^reutc-sf depths in which any cables had been laid previous to this were those in the Meditenanean and Black -Seas, durinj,^ 1854, 1855, and 1856. .Some of these were, temporarily speaking, partial successes, others absolute failures ; indeed, several of them had met with disaster even in the process of laying. An example of this was the cable between Sardinia and Algeria of 1854 (600 N.M.) in a maximum depth of about 800 fathoms. Again, the unprotected gutta-percha core laid from N'arna to lialaclava in 1855 failed, as already shewn, not long after being submerged. In 1855 a cable was successfully laid between .Spezia and Corsica in water running into an outside depth of 325 fathoms, the length being about 1 10 miles. The greatest leii^^th of line which had been submerged in a satisfactory manner previous to the first Atlantic cable was that between X'arna and Constantinople — 171 miles -along the more or less protected Black Sea shore in 1855, the depth being upwards of 100 fathoms. THK DAWN OK OCKAN TEI.EC.KAl'IIV. 35 In the early experiments made by Professor Wheatstone with frictional electricity on a short lenjjth of bare wire in a room, the subtle influence was shewn to pass at the rate of nearly 300,000 miles in a second of time. Later experiments with voltaic electricity [i.e., that obtained from a voltaic pile or batteryj, established the speed of transmission on bare overhead telegraph wires to be about 16,000 miles per second. When, however, the under^'round gutta-percha insulated wires laid b>- the " Ma^Mietic" Company in 1S51, which extended between London and Dublin 'i'ia Manchester and Liverpool, were tested on this point, with variously increased length, it was found that a far lower rate only was attainable. In a jjapcr read by Mr lulward Hraiisford Hright, accompanied by experiments, at the meeting of the British Association in 1X54, the velocity of ordinary' telegraphic currents* in subterranean conductors was given as not exceeding 1,000 miles per second.t and he shewed that the gutta-percha insulated wire tended to retain part of the charge i)assed into it. In fact, the similarity between the conductor and a Leyden jar was on this occasion clenrly set forth, in the sense of the induced charge on the outside of the dielectric holding back as a static charge some of the electricity flowing as current through the conductor, in the same way that the charge induced on the outside plate of a Leyden jar statically holds the primary charge on the inner plate, until either are neutralised. The doubts as to working across the Atlantic were, however, very much modified by a .series of experiments, instituted bj- Mr (afterwards Sir Charles Tilston) Bright, and also by others independently carried out I in a larger scale by Mr Edward Orange Wildman Whitehouse. J Both of these sets of experiments were upon the underground wires of the "Magnetic" Company's system, § which were so connected on various occasions as to afford a length of upwards of 2,000 miles in one con- * It soon became e\ident that the rate of working was — on broad principles and within certain limits — entirely independent of the nature of the yenerating agent or of its power— /.I'., was practically uninfluenced by the number of cells employed. However, nowadays, witli automatic transmission, a somewhat higher electro-motive force often renders signals readable which, owing to the ultra high speed at which the impulses follow one another, would not otherwise be. (■ Later on, it was demonstrated by Professor Thomson th,it electricity could not be said to possess velocity, in the ordinary sense, at all. I Previously a surgeon at Brighton. S Mr Whitehouse's conclusions were considerably more favourable than those arrived at by .Mr Uright, or any one else, for the proposed cable. C .''■'' ^ ' ' " "■. , ' 26 Sl'llMAKINK ■I'l'.I.r.dKAI'lIS. tiiuious circuit. According to Mr W'liitclKUise, "signals* were clearly aiul satisfactorily transmitted over this vast leii},'th at the rate of 2io, 241, and 270 per minute, with a facilit)- that would answer every commercial re(|uirement." + The difficulty in working; that had been found to arise from the re- tardation of the electric current, due to induction, was overcome, as it had previously been in the magneto-electric instruments of the " Magnetic " Company, J by using a succession of opposite currents. By this means the latter or retarded portion of each current was wiped out by the opposite current immediately following it ; and thus a series of electric waves could be made to traverse the wire, one after the other, several being in the act of passing onward at different points along the conductor at the same time. While prior to, and during, 1855 the essential conditions and methods of signalling through an Atlantic cable had been independently investi- gated by Mr Charles Bright and Mr Whitehouse in Kngland, the con- nection of the United States and Canada with Newfoundland had at last been brought to a successful issue. In 1852 Mr F. N. Gisborne, a very able English engineer (previously engaged in constructing the Nova Scotia telegraph lines), in concert with an American syndicate, headed by Mr Tebbcts of New York, obtained an exclusive concession for connecting St John's, Newfoundland, with Cape Ray, in the Gulf of St Lawrence, by an overhead line. The idea was to "tap" steamers coming from London at Cape Kacc, St John's, and pass messages between that point and Cape Breton, on the other side of the gulf, by carrier pigeons. A few miles of cable were made in England, and laid between Prince Edward Island and New Brunswick. Mr Gisborne then surveyed the route for the Newfoundland land line, and had erected some 40 miles of it, when the work was stopped for want of funds. When in New York in 1854, Gisborne was introduced to Mr Cyrus West Field, a retired merchant, who became enthusiastic on the subject, and formed a small but strong .syndicate. Better terms were then obtained * I.e., battery key contacts, producing single impulses. + Professor S. K. B. Morse was also present at these e.xperiinents. He, moreo'cr, accompanied the first expedition, aboard tlie "Niagara," as electrician to the New York, Newfoundland, and London Telegraph Comjjany, which was naturally largely interested in the proposed telegraphic connection between Europe and Newfoundland. Professor Morse gave the scheme his entire support and scientific approval. X Devised by Mr W. T. Henley, and improved on by Messrs Bright. Till-; DAWN ()|- (i(i;.\N TKLKCKAI'IIV. 2? iVoiii Ncwf')Uiull;iiKi,c()vciiii,L( (witli the idea of an Atlantic cable, sii^f<,'cstccl many \-ca.. before both in iMii^land antl the States) exchisive ri};hts to land cables for fifty years, which monopoly they were able to ^jet extended to New Brunswick, Cape Breton Island, Prince Kdwarcl Island, Nova Scotia, and the shores of tlie State of Maine. In the meantime, Mr John W. Hrctt* had joined Mr i-'icld's syndicate, to which he subscribed a considerable sum. A sinj,de-C()ndi.ctor cable of 85 nn'Ies was madet in Kiii^land by Messrs Glass, Klliot, and Co.,* to be laid between Cape Breton and Newfoundland, from a sailing ship 10 be towed by an American steamer, "James Adyer," with Mr Field, Professor Morse, and many friends on board. Mr (now Sir Samuel) Canning § was in engineering charge on behalf of Messrs Glass and IClliot, but after 40 miles were laid, in August I.S55, rough weather ensued, and the captain of the barque had to cut the cable to save his vessel. .\ fresh instalment was sent out in 1856, and laid successfully across the gulf, thus connecting St John's with C'anada and the American lines. It iiad one conductor, into which a great improveinent was introduced for the first time. It was made of seven small copper wires laid up in the form of a strand, with a view to preventing a flaw in one of the wires at any point cntirel}- stopping the conductivity. The insulated conductor was covered with tarred yarn, and protected by a sheathing of twelve outer iron wires. The weight was 2A tons per N.M., and it lasted a long time, being successfully repaired ten years later. * This gentleman, together with his Ijrother, Mr Jacob 15rett, had registered a company as early as 1845 for uniting Europe with ."Xnierica by telegraphic communication under the title of a "Ceneral Oceanic Telegraph Company." t This was probably the first occasion on which the cable, as manufactured, was properly coiled in specially constructed tanks at the factory previous to shipment. Hitherto, the floor had been used for this purpose, and the coiling was of a somewhat rough-and-ready order, leading sometimes to entanglements between the turns and flakes. t This firm had lately taken over the business of Messrs Kiiper and Co., one of the leading wire-rope makers (for colliery and other purposes), who had been associated with several of the previous early submarine cables. S Formerly a railway engineer under the late Mr Joseph Locke, M.P., F.R..S. I This substitution for the single solid conductor not only obviated the objection of an imperfection in the copper at any one spot having serious results, but also lessened the risk of complete discontinuity due to any mechanical tension. It, moreover, gave .greater pliability, thereby reducing the chance of breakage under an undue lateral strain, and also of injury to the insulating envelope. Since the above occasion the conductor of a submarine cable has been invariably liuiit up by several wires stranded together. This type of conductor was provisionally protected in 1854 (see specification No. 2,547 ot that year) by Professors William and John Thomson with Professor W. J. 28 SUJniARINK TKLECRAl'IIS. Mr Cyrus W. Field, the Vice-President of the New York, Newfoundland, and London Telegraph Company (formed by the above-mentioned syndi- cate), then came over to England in July 1856, empowered by his associates to deal with exclusive concessions; and on the 29th September 1S56, an agreement was entered into between Mr J. \V. Ikett, Mr Charles liright, and Mr Field,* in which, on an equal footing, they mutually agreed ( )ri^inal SliUion of ihe Xcw \'oik ami Ncwfnuiull.unl Tcltf;iaiili Cumpany, 1855, pii'vimis to crc'CtiiJi) of periiianeiU Imililir^. (as the "projectors") to evert themselves "with the view and for the purpose of forming a company for establishing and working electric telegraphic communication between Newfoundland and Ireland, to be called the ' Atlantic Telegraph Company,' or by such other name as the parties hereto shall jointly decide upon." The nature of the ocean's bed had bj' this time become ascertained by several series of soundings taken bj- Lieut. O. H. Herryman, L'.S.X., from Macquorn Kankine, thoiij^h never completed as a patint. The main object with the devisers was to enable a larj^er conductor to be used than was uossihle, for mechanical reasons, with a single wire. It sliould be remarked, liowcver, that llie nieclianical advanl,ij.jes of a strand had been previously appreciated and adopted in practice in various ilirections, including that of iightnin^' conductors, by Newall and others. * Joined later by Mr Whitehouse. TIIK DAWN OF OCKAN lELKCRArilV. 29 L'.S.S. "Arctic," and als() b)- Coininaiuler Joseph JJaymaii, R.N. (H.M.S. " Cyclojis "), shewing that a {gently undiilatintr plateau of t;rcat breadth, at a depth varying gradually from 1.700 to 2,400 fathoms, extended nearly the whole distance between Ireland and British North America. These flejjths, though great for the purjose in view, comjjared favourably with the soundings of 6,000 to 7,000 fathoms that Jiad presented themseUes further southward. The soundings were taken with the ingenious apjiaratus of Lieut. J. M. lirooke, U.S.N., by which the weight was automatically detached on reaching the bottom, while a small tube still retained by the line brought up specimens of the bottom, consisting of a .soft ooze formed bj- the tiny shells of microscopic "infusoria," borne along, while alive, by the warm water of that " ri\er in the ocean " the Gulf Stream, and flying in countless myriads on the temperature being lowered b>' contact with the more northern seas.* This table-land— thus .seemingly rai.sed ,.„., ,4. _inf„soiia at the Bel of the at the bottom of the sea — was chris- -Vtlantic Ocean: M.ignitieil io,c«o tencd "Telegraph I'lateau " + by Lieut. M. F. Maury, U.S.N., Chief of the U.S. National Ob.scrvatory. * In those clays soundings were effected by a hempen line offeriny; enormous surface resistance. Soundings by such means were unreliable on account of the slow rate rendering it difficult to ascertain when bottom was reached. For the same reason the process was a lengthy one. Sir William Thomson introduced his pianoforte wire ni.ichinc in 1872, and this has since been considerably in.provcd on in the sounding machines of Mr F. R. Lucas, Messrs Johnson and IMiillips, and the .Silvertown Company, the latter having made a speciality of submarine survey. + The specimens which were brought uj) from depths ranging between i,/00 to 2,4CH3 fathoms, in the region of the so-called " telegraph plateau,' bore a very strong resemblance to exceedingly finely powdered chalk. Their appearance at the bottom of a glass vessel was that of a light brown muddy sediment, in which were observed minute hard particles, h.irdly any of which exceeded one-fiftieth of an inch in diameter. I'o i|uote from the report made by I'rof. T. H. Huxley, F. 1<.,S., on the specimens of the houom obtained, and illustrated in Fig. 14 :- " Fully nine-tenths consist of minute animal organisms, called foruinini/cra', provided with thick skeletons composed of carbonate of lime. The species of the ' foraminifera-,' of which 85 per cent, of the specimens consist, is called i,^M'i\i;cr/mf." llic specimens shewn have been magnified aliout 250 times their natural size, and were, as may be seen, of various dimensions and shapes, yet with general points of rts-.finljlnnce. I he actual words used, in this connection, by I.ieut. Maury, in the cotirse of his report im the proposed tran j-.-\tlantic cable, were :- " The bed of the sea between 30 sui!M,\i;iNi: I i;l.i;(.ilaccs for tin; c.ililc ciuls necessarily arose, and 'I'rinity Hay, New fonnfllan'l, was coiisirlcicl cniincntlv adaptcfl for the jjurpose, l)ein;,' about tlir n<-arcst point, and havinj^ a very dccj) entry f^aiardcd by hanks on each sidi'. 'I'lius, if iceberj^s j^'ronnded on cither bank— as fre(|iicntly happened — th(;y conhl not, svliei) reducefl in their size !))• niehinj.;, toin h, wlii'-- driftinj.;, the }.;reater de|>tii of the main clianiiel, in the deepest part of uhi< li the ( abli- would be subnier!.;cd. On the Irish side, Mr lulward Mrij^ht, tiie niana(.;er of tlie " Ma^^netic: " Teh-^raph ronipaii)-, uitli some of liis staff, examined the various liarboiirs aiul licai hes betue(;n 1 )iii}.;ie and Hantry Mays, on the extreme sf)nth-\vest jMomontor)- of Ireland, the nearest land towards America. Mr i5rij.;hl (bartered ;i fishiiif^j-smack for tin- |)in|)osc ; and after considering; the <|uestion of freedom from ancliora^je, rocks, soft prot(;ct('d laiidini^', tof^ether uitii the available A'lmiralt)- sonnilint,'s, h(; pronounccfl Valentia* May as the; most suitable locdit)-. Tins seleclion has sinc(! been well jiistificfl, jiid^inj^' by the number of cables subsc(|uentl)- landed there, or in the- iuuuediate vicinit)'. The actual route dei idcd on for tlx- entire line is shi'\vn in the (hart facin;,' this jja^^je, witli the sounding's r('ferr(;d to above. iJurin^ the above preliminaries a lar[.;e niunber of specimens of t)pes of cables were made by Messrs (ilass, I'.lliot, and Co., and tested for streii}.;th, in (onnection with their weight and other ( on(|iti<)ns. On the ^rd of Oi toiier 1K5C), the results of ?klr VVhitehoiise's experi- mcMital researches cxtendin}; over sev(;ral years were slurwn to l'r()fi'ssor Samue! Morse, 1,1, I )., the el(!ctri( ian of the- New \'ork and Newfoundland Coinpan)-, at the ((.-ntral office of the "Ma;.jnetic" {'om|)anv, in l.-ndon, an(| on the .'.< i[]\ of th.it month the .\tlaiiti( Tele!;ra|)h Compan)- was re;'istered. Iiclaiiil ;iiii| Nrwfoitndhiud is :i ])l;ili;iii, ulilili scciii'. to havp lurn |ihii cd ihcir- especially fur llw |)ui jhisc nf hrildiii;; a siiliiiriiinc lilc^t;'|)li, and nf kicpiny; 11 (nil nf I 111; w;iy. ' In liit(.T years, the nc( cssily of sniindin^i licin;; taken in jjie.iici luoxiniiiy Id one aiioliier JKivinjj for' ed itself ii|)on the minds of lli()'>e en.;aKed in (aliie work, siil>sei|iieiit e\|u:rien(e lias shewn this lied not lo l)e so plateau like as was then sil()|)ose(l, tlioiiuli no very serious irregularities ncciir an this route as against what may he found .1 hundred miles or so south, where the " I'araday IlillH" wen; dis( (ivercd lai(;r on liy S.S. " laraday," when < ahU? laying for Messrs Siemens Itutlhcr*. The ahove mentioned .upiio.ed " plaleau " was ( crlainly made the most of at liie lime in various diaKrain-. ,inii ma|)-,, purjorlin^; lo shew the cxlrctiue eveiuiess of the pniposed course in ( omparison with neiKd)l)OiM in;; beds of the All.'intic. '■'' .SoinetinH.'s still spcdt V'ahMicia /'.(■., in the: same way .as the pl.i( e on the e;isi (o.isl of Spain. * HTIC TELI Orncu ; 21. OlD I /. tr "i ,ri\ «. ^-^.■^p:.J|:f t j|' 14- ,-^ 14- ^■[M •jLj- "« '^*i'^^ ■' u;^^- -— ^- ,> * ,< ii . I '■4v. ti: / '* t* ^■VJlifci ■ 1; i 4^ ! ' '•'?*• -_ _^. ■ . 4*™.:- ^C- .^4. ■ f ^ «¥•" l«*)j*i!i»nri*'j^ ""•laaatiiii i,j„„ ''M rftWj%ii iii JO TCUCCIUW LiNU ^ _ SuiMARiNcTcLEoiiAni CuKs \» Omutiom • SOON TD BE MIHCMGtO All Sounoircs tN Fatmoms raOFILC 0' TN I MTTOH or THf ftfLANTIC ■emiN VALlNClA ftAV. iMtLAID. ANO S^ JOHNS . NAWVOUMDL«ND. «l SOVMMP Bv TMK U •; &r(«HCN pnonL.c or rttt mttom v rnt Atlantic ■ctwcui TNtviTr mv «twvHiHOtAM0 and VAUmcia Wr, iMUMt.Ai MUNOto av h tt tTiAttin 'cvciofs', jtvi RICA. ATLANTIC TELEGRAPH COMPANY. OFFICES: 22. OLD BROAD STREET. LONDON. ENGINEER-IN-CHIEF. m ;:.;e'---V'vi(lc(l for llie constiiiction alone. Tin's co|)per had to be drawn out into 20,500 miles of wire fprovidinLj for the la_\- j ; and seven parts of this wire had to be laid np into a strand 2,500 miles lon_tj. l'"or the insulation, moreover, ncarl\- 300 tons of L,nitta-percha were required to be prepared, and applied to the conductor in three separate coatings. Lastl}-, and with a due allowance for lay, 367,500 miles of wire had to be drawn from l,6(S7 tons of charcoal iron, and laid up int<- about 50,000 miles of strand* for the outer sheathinfj.t Added to this, the ships had to be selected and got ready to receive the cable. Moreover, machines both for manufacturini,^ and layinij had to be constructed as well as dcsij^ned. * This race aj^ainst time was the outcome of an unfortunate engagement (in.sisted upon by Mr I'ield in comiection with his American arrangements) on the part of the compan\- towards its sliareholders and the ])ublic. Messrs Bright and W'hitehouse urged that more time should be given, to ensure greater care in manufacture, and the former advocaterl a different type of cable, with a conductor more than three times as large, and a much greater thickness of insulation. § Hut the contracts- had been given out b}- the provisional cf)mmittee before he was appointed to the i)ost of engineer. * The entire lenj,'tli of wire used in the manufacture of this cable was, in fact, enouijh to girdle the earth thirteen times. t The two firms enj^a:.,'eil in the construction of this cable unfortunately applied the sheathintr wires with opposite lays. Messrs Newall adopted the more ordinary (rij^ht- handed) lay, as had previously been the custom for telef,'raph cables as for ropes. Messrs (llass and Elliot discovered, however, that fresh turns would be put into a cable with such a lay in the act of coilinjf (rii,du-handedly) into the tank of the layin;,' \ essel. They, therefore, laid up the wires the opposite way, so that in coiling down, the turns set up in n)anufacture would be taken out aJ,^^in. They did not, however, advise the other parties concerned of this change, and thus it was not known till afterwards. The left-handed lay of Messrs Glass and Elliot is now invariably adopted in the construction of telegraph cables. I 'l"hc late Mr Willoughby Smith bore suitable and independent testimony to these abnormally hurried conditions for the amount of work to be done in his " /\'i\i//»ii' of the Earlier Days of Electric Telegraphy," delivered to the .Society of Telegraph Engineers during their meetings at Paris on the occasion of the Electrical Exhibition in 1881. {'Ace-Joi/nid/ Soc. Tel. Engrs.^ vol. x. No. 38.) S The type of core actually recommended by Sir Charles Bright was "a copper conductor composed of seven equal wires of maximum purity stranded together, of such a gauge as is equivalent to a weight of 392 lbs. (3), cwt.) per N.M. This conductor to be covered with three coatings of gutta-percha of a thickness represented by the same weight per N.M. as the conductor." II The contract price for the entire length of cable manufactured for the Eirst Atlantic Line was ^225,000, the core costing ^40, and the armour /"50, per mile. An Atlantic cable of the present day runs into about half a million sterling. Gutta- percha in those days was less scarce ; on the other hand, its manufacture was more of a novelty, and there was less competition in the whole practice of cable-making. 36 sumiAkiXK ti:lec;rai'Hs. There was not time to provide proper buildiiiijs or tanks on shore, and the cable consequently was laid dry, and exposed to the sun's heat, v, hich injured some upper la\-crs that had to be subsequently cut out. Un- fortunately no experience in these matters was at hand, or no doubt the extreme importance of such questions would have been better appreciated.* To carry through the then unjirecedentcdly heavy work devolving upon the engineering department, Charles Bright associated with him.self Messrs Samuel Canning, \V. Henry Woodhou.se,+ F. C. Webb,* and Henry Clif- ford. The three former had been prominently connected with cable-laying for some years, and the fourth was a most able mechanical engineer. The Ikitish Government placed H.M. battle-ship "Agamemnon" (ninety- one guns) at the Company's service. She had been Admiral Lyons' flag- I VjiS'.ica: ^^ J . • ' - ' j^*-^- * iHij ■ '4 ^t^^^^HJgipiMM*-^ St^'^if \]Lj^B :s»*m^' Pi] ^""^^^v^hbH n ' \m^ P'^'i^^S k. ■ i k i tpp^l ^ i jj^j ii : m U.S. Frigate " Niaj^ara," used iox laying the Allaiuic Cal)lc of 1858. .ship at the bombardment of Sebastopol, and was well suited for the purpose, her tonnage being 3,200, and her two screw engines well aft, while amidships she had a magnificent hold 45 feet square and about 20 feet deep. In this capacious receptacle nearly half the cable was stowed away, from the works at Greenwich, the balance being divided in two other small coils. She was in charge of Commander C. T. A. Noddall, R.N., and was * Iron tanks were strongly urged by Mr liright for stowing the cahlc in to permit of it being kept constantly covered with water after manufacture, and untd being sulimerged. This recommendation was, however, only followed to the extent of keeping the core in water during testing operations. + Like Mr Canning, this gentleman was originally a railway engineer. \ Mr Webb has probably had a greater experrence in all phases of cable work than any one ; moreover, he has taken prominent part in more of the early expeditions than most of the pioneers. -.:_i__-L_.™i^ THE DAWN OF OCKAN TKLKClKArin'. 37 one of the finest of the Hne of battle-ships in our navy at the time. Mr H. A. Moriarty, R.N., was to serve as navigating master. The other half of the cable, made at Birkenhead, was coiled on board the U.S. steam frigate "Niagara" (sec p. 36), Captain W. L. Hudson, lent by the United States Government. She was the finest vessel in their navj-, of 5,000 tons, and had only recently been modelled b\- Mr Steers, the great yacht builder of America. Her lines were in Hict those of a yacht ; and it cost Captain Hudson a great pang when he discovered how much she had to be chopped about to take the cable. During the brief period available, Mr Bright, in conjunction with Mr C. De Berguc, of Manchester (a mechanical engineer of .some note), and with the able assistance of Mr Clifford, devised the machinery for paying out the cable, the main principle of which is shewn in Fig. 17. It included a waiter's balance arrangement, intended to indicate the strain on the cable.* The above application of a Salter's balance as a dynamometer for cable- laving did not prove satisfactory. The vibration of the levers and rigidity Vic. 17. of the friction-brake prevented it giving a steady indication of the strain, such as could be read off with any sense of accurac}-. 'I'he same plan had, however, previousl)- been adopted with .some success when cable-laying in the comparatively shoal waters of earlier cables. Mr liright al.so had what was aptly termed a " crinoline," + or cage of iron bars, fixed round each ship's stern as an external guard to prevent the cable from fouling the screw, if necessity aro.se for backing the vessel.'^ * This machine was construct^ and set up on both ships by Messrs De Bergue and Co. It was afterwards substituted by another, in the following expedition, designed by Mr Charles Bright, with the co-operation of Mr H. Cliftbrd, and Messrs Easton and .Amos, the makers. f Nowadays known as a screw-guard, and fitted to the telegraph ship " Faradav." + This was a particularly suitable |)recaution in this instance, owing to the fact that on both ships the picking-up apparati's (as well as that for paying out) was at the stern. t)n more than one o( casion the cable was thus spared front coming into contact with the ship's propeller. The (piestion of recovering and rejiairing a cable in deep water liad not been much gone into at tiiat time. Thus, tiic picking-u|) gear, i)laced alongside that for paying out, and worked by steam, was merely intended as an auxiliary for hanging on to, or hauling inboard again, any short length in the event of a fault or any mishap occurring whilst laying the cable, the paying-out apparatus not being fated with any steam-engine. 38 SUBMARIM-; TI.LKdKArilS. In adcUtion, he cleviscd an electrical lo^-, completing and breakin_L,r tiie circuit at ever\- revolution. Here, by means of a jrutta-percha covered wire passed up the line, the log itself continuously signalled and recorded the s]5eed through the water. It had been intended to start laj-ing from mid-ocean from both ships, one towards Ireland and the other to Newfoundland, so as to ensure a quiet time for making the splice (for thus they could wait in the middle and choose their weather), and also therebj' reducing the period of laying by one-half. This course was strongly urged by Mr l^right and his experienced staff of engineers. However, the electrician, Mr Whitehou.se — The Lord-LieiUciuint of IicLuul maUiiif,' a Speocli on llie Starting of the I'iist Kxpeilition from N'alentia Bay, 6lh August 1S57. whose health did not permit him to go out on the expedition — urged starting from Ireland. Owing largely to the anxiety of the board to have continued repc, secured to the outer arms of the bent levers N. The assistant stationed at the wheel (sec illustration at head of chapter) easily followed the indications of the dynamometer, and, by turning the wheel in the required direction, could regulate the strain by lifting or lowering the weights attached to the bent levers, and so opening or closing the brakes. In Fig. i8, s is a water (or oil) cylinder with piston-rod and weights V regulating the pressure on brakes attached to paying-out drums. T is a water cylinder with piston- rod and small weight attached to brake of sheave guiding cable with one turn from the jockey lever j to the drums. This friction gear for controlling the speed of egress is usually spoken of as " Apjjold's brake." t As may be seen from the foregoing description, and still better in detail from Figs. 22 and 23, the above ingenious form * A dynamometiical arrangement of the same principle, but of a somewhat heavier character for the j;reater strains experienced, is also employed in the o])crations connected with the recovery of submarine lines. Here, in dragging for a cable, the dynamometer apparatus may be said to take the same part as the float does in fishing — by giving warning of any nibble, so to speak. In the case of cable w.^rk. a bite, during grappling, is indicated by a tug on the line to the extent of something like three tons additional strain. + The late Mr John (]eorge Appold had previously invented a brake on this principle (Patent No. 13,586 of 1851), for "regulating and ascertaining the labour performed by manual or other power." This was intended more especially for application to the work done by prisoners on the crank, by means of which the exertion of turning it could be absolutely regulated from outside the wall to meet the varying strengths of prisoners. It was also used later for measuring the power of agricultural and other portable engines. The actual brake apparatus, described in the text above, and shewn in detail, with dynamon^etric connection, in Figs. 22 and 23, was an iinproved modification of that embodied in the patents of Mr Charles IJright (Nos. 990 and 1,294 of 1857), adapted for cable operations, and referred to earlier. Fig. 24 shews the brake-drum, in section, run- ning through the tank of water. This modification was inainly due to the late Mr J. C. Amos, an engineer of great ability, of that eminent firm, Messrs Easton and Amos (now Messrs Easton, Anderson, and Goolden), who not only constructed and fitted up all the cable gear for this undertakmg, but also took an active part in the arrangements. [Plate V. Ubie ■^m^r^^'s^^swr^rmr'd^^sr'r^ji ',.^^m!(-'^j^^P2l'-^^^W'M<> .i •c Cable, 1858. [To /ace p, 42. Cf^^in for lifhnjg Brake ^^'S^^A im. ' ^ V - — '-- — > '■ N — , ffy> '^■'''''^-'^'^■^■'''^■^^(■■'''■^-'^^^ Fios. i8, 19, 20, 21.— Paying-out Machinery ol First A [Plate V. C^b/e T^^'/M'i:^^ 21.— Paying-out Machinery ol First Atlantic Cable, 1858. [To face p. 42. Tin; DAWN or OCKAN TKI.r.dKAl'IIV. 43 of brake is self-rclicvin^f— iiuiccfl, in certain senses, self-acljustinjf. Hy its means, thou^Mi the strain cnuld l)c nuiuccd at a moment's notice, it could not be imreaseti hy the man at the wliccl. This entire apparatus has since been universally adopted for submarine cable work, with the exception that a single flanged drum fitted with knives (end view of Fig. 22), takes the place (jf the grooved drums as a rule.* Knd Klcvation. Sule lUcviUiun. Fu;s. 22 and 23.— 1). tails of A|i|"il(l Friction Urako, nynaniomctcr, etc., as applied I" Calik' Work l)y Bright and Amos. Mr VV. E. Everett, U.S.N. , chief engineer of the " Niagara," who had joined Mr Hright's staff, and Mr Clifford, superintended the construction and installation of ail the cable machinery. Fk;. 24.— .\pi)old Brake running through Tank of Water to I'revent Undue Heating. In April 1858, Profe.s.sor William Thom.son (afterwards Sir William, and now Lord Kelvin) had designed his first marine galvanometer f (Letters ves introduce extra friction to the cable, there are, )referring this form of gear to any apparatus in which * Resides the fact that the ^ even nowadays, several reasons !> a knife is introduced as a guide to ' fleet " the inconiiuf,' turn t .\ higiily sensitive modification of Gauss and Weber's very heavily constructed reflect- ' ing telegraph of 1837. In virtue of its extreme sensitiveness, it had the effect of materially reducing the length of time taken by a sufficient force of electricity reaching the further 44 SUBMARINE TELEGR.M'HS. Patent No. 328), an instrument of extreme delicacy, adapted both for test- ing purposes — especially aboard ship during cable expeditions — and for receiving signals through long submarine cables* Successful Expedition of 1858. — After some preliminary trials of paying out and picking up cables in 1,800 fathoms in the Bay of Biscay during the spring of 1858, H.M.S. "Agamemnon," Captain G. W. IVeedy, R.N., and U.S.N. S. "Niagara," Captain W. L. Hudson, U.S.N. , proceeded out (after a fearful storm, during which the "Aga- memnon" nearly foundered t) into mid-ocean, between Newfoundland and Valentia. Here the splice between the two portions of cable was made; and on the 1 6th of June the .ships .separated, the "Agamemnon" laying towards Valentia, and the " Niagara" in the direction of Newfound- land. Whilst paying out, the cable parted three times in succe.ssion, and each time the operatifjn had to be commenced over again, 540 miles of cable being lost in thi.i way. After putting into Oueenstown for supplies, the expedition sailed again for mid-ocean, where once more work was begun in the same way. To effect the splice aboard the " Agamemnon " between the cable ends on the two ships, in the middle of the Atlantic, the following was the cour.se of procedure. In the first place, the end on the " Niagara" was passed to the " Agamemnon." Owing to the outer wire covering of each cable being laid in reverse directions, the ordinary splice was impossible. A special, and naturally weak, form was involved ; and pro- vision had accordingly to be made to avoid any undue .strain coming on it. Two hah es of a wooden frame, with a groove cut in each, were employed end, such as was capable of actuating the indicating apparatus This was the forerunner of what we now term the mirror-speaking instrument, and may be said to have been the means of first rendering ocean telegraphy a faU accotitpli from an electrical and com- mercial point of \ lew. The latter fact will be apiircciated, when it is stated that the best instrument, contemporaneous with the Thomson mirror gahanometer, could scarcely receive two words per minute, where the working rate of the "mirror" was ten to twelve words, and with a subsequent improvement this was increased to a capability of twenty per minute. Moreover, it required considerably less power. It v,as a matter for regret that the electricians did not avail thcmsches of this beauti- ful instrument until after the cable had been laid some time, and all other signalling apparatus had failed, following on a few weeks' use. The astatic reflecting galvanometer was not invented by Professor Thomson till some years later * This was an entirely different form of marine galvanometer to what is at present distinguished by that name, which was brouglit out by Professor Thomson in 1863 — about the same time as the astatic reflecting galvanometer. + See Frontispiece, upper portion, from an original drawing by Mr Henry ClifTord, which was reproduced at the time by the Illustrated London AVri'.c A life-like descrip- tion of this event also appeared in The Times shortly after the occasion. During this memorable storm the ship rolled to an angle of 45 at times, occupying over ten seconds. The height of some of the waves from crest to hollow was said to be over 40 feet. THE DAWN OF OCKAN TKLKGRAPHV. 45 for the two spliced eiuls to lay in, as illustrated in Fig. 25. The union of the ends — by what is sometimes described as a "ball splice" — was the first operation. This merely consisted of the wires overlapping each other bent backwards and forwards — the only possible form for two cables with opposite lays. This splice was then laid in the lower half of the frame, the cable on each side resting in the groove. The arrangement of each end in the frame is shewn here. The part forming the loops (served with spun yarn and fitted securely in the groove) tended to prevent any strain coming upon the splice, intermediate between them, by them.selves taking all the stress. The two halves of the frame (covered over with iron boiler plate) were then bolted together, and thus formed a solid protec- Wire Rope to Take Strain off Splice Frame Secured to Cable Counteracting Weight Vir.. 25.— Frame for Mid-Ocean .Splice of Firsl Atlantic Cable, 1858. tion to the siilice. A wire-rope stay was secured to the cable, and this prevented any undue strain coming on the splice fraine. The weight attached to the frame was to prevent the frame and splice turning o\er under tension. The whole arrangement has been characterised generally as extremely ingenious. The " Agamemnon " started pa)'ing out as soon as the splice was lowered into the sea. After paying out a certain length a signal was made to the "Niagara" to do likewise. Then both ships continued to pay out until '.he splice was supposed to have reached the bottoin, when each vessel proceeded on her course at I P.M. on 29th July ISS.S. paying out cable in lat. 53' 9' N. and long. 33' 27' W. The "Niagara" steered towards America, with Mr Brighfs assistants, Me.ssrs Woodhouse and Everett, in charge respectively of the cable and machinery, 46 SUBMARINE TKLKGKAI'HS. whilst Mr C. V. de Sauty * was in control of the electrical department.^ Mr Cyrus Field was also on board ;^ and H.M.S. "Gorgon," CoiTimander Joseph Dayman, R.N., escorted the " Niagara." She had an uneventful voyage, in fine weather, and was met by H.M.S. " Porcupine," Captain Henry Otter, at the entrance to Trinity Bay, to pilot her to the landing- Landing of the First Atlantic Cable in the Bay of Bull Arm, Trinity Ray, Newfoundland, 5th August 1S5S. place. Except for cutting out a fault in the wardroom coil on the 2nd August, all went well, and the cable was landed (as shewn above) in a little * After the expedition Mr De Sauty became superintendent at the Newfoundland station t liesides Mr De Sauty, there were also on board either the " Niagara" or the " Agamemnon," as assistant electricians representing Mr Whitehouse and working for Professor Thomson, Mr J. C. Laws, Mr Whitehouse's chief; Mr E. (i. Hartholoinew, representing Professor Thomson on the "Againcmnon'" ; Mr F. Lambert, who afterwards became a prominent electrician and member of Messrs Hrij^ht and Clark's stafT, and later attached to Messrs Clark, P'orde, and Taylor ; Mr H. A. C. Saunders ; Mr Henjamin .Smith, now an authority on all electrical matters connected with cables, and superintendent at the Eastern Com|)ain's Alexandria st.ition ; Mr Richard Collett ; and Mr Charles Gerhardi. Mr Whitehouse himself was not able to go on eithei expeditions on account of his health. Mr Samuel Phillips, sen., was closely associated with Mr Whitehouse in most of his early researches ashore. Mr Saunders has since taken a prominent part in the extension of submarine telegraphs in the capacity of chief electrician to the Eastern and Eastern Extension Companies, besides acting as consulting electrician to other of the allied companies. Mr Cicrh.irdi has for many years re|)resented the Direct Spanish Company as its manager; and Mr Collett is the secretary of the Brazilian Submarine Coinpany. I The expedition was ailditionally accompanied by Mr Nicholas Woods, representing 77/(' Tt'wfs newspaper. Mr Woods wrote a number of articles for T/tc Times during the THE DAWN OK OCEAN TELEGRAPHY. 47 bay, Bull Arm,* at the head of Trinity Bay, Newfoundland, at 5.15 a.m. on the 5th Augu.st, when they " received verj' .strong current.s of electricty through the whole cable from the other side of the Atlantic."t The tele- graph house at the Newfoundland end (see illustration at foot of this section, p. 56), was some two miles from the beach, and connected to the cable end by a land line, as shewn. The voyage of the "Agamemnon," laying the cable towards Ireland, piloted by H.M.S. "Valorous," was by no means so prosperous, as she experienced very rough weather and heavy head winds nearly all the waj-. It was only by the constant watchfulness of Mr Bright and Messrs Canning and Clifford that accident was avoided during the violent pitching of the ship. On one occasion a fault was discovered onlj' a very short distance from the paying-out machine. Professor Thomson reporting that continuity had ceased. " The ship was stopped, and the splice was worked at as men only could who felt that the life and death of the expedition depended upon their rapidity. All their zeal was, however, to no purpose. As a last and desperate resource the cable was stopped altogether, and for a few minutes the ship hung on by the cable. The strain was continually rising above two tc.is, and it would not hold out much longer. Fortunately it was onl)- for a few minutes ; so as soon as the splice was finished, the signal was made to loose the stopper, and the cable pas.sed overboard safely enough." * The rough weather continued until the " Agamemnon " got into shoaler water (off Doulus Head) on the 4th August ; and on the following morning, the " Agamemnon," ably guided (see Frontispiece, lower portion) b\' Mr H. A. Moriarty, the navigating master, entered Doulus Bay, Valentia, and anchored at 6 A.M.§ She had been under the escort of H.M.S. " Valorous," Captain W. C. Aldham, R.N. The total length submerged by both ships was 2,050 N.M., the average slack paid out being about 17 per cent. The end was landed expedition, which were mucli appreciated by its readers, yivinjf detailed accounts of the expedition as it progressed, somewhat in the form of a narrative. .Similarly, Mr John Mulialy was aboard the U.S..S. "Niai,'ara," reporting on behalf of the Nco York Herald. This gentleman afterwards produced a book on the subject, treated from an American stand[)oint. * This spot was selected on account of its seclusion from prevailing winds, and owing to its shelter from drifting icebergs. + Engineer's log, U.S.N. S. "Niagara." X Engineer's log, H.M.S. "Agamemnon." S The successful laying of the first Atlantic cable being completed on 5lh .August 1858, it was exactly one hundred and eleven years after Dr (later Sir William) Watson had astonished the scientific world by sending an electric current through a wire over two miles long, using the earth as the return part of the circuit. 48 SUBMARINK TELEGRArHS. (see illustration below) at Knightstovvn,* where Mr Bright, Professor Thomson, and the other greatly tried members of the expedition were heartil)- welcomed by the Knight of Kerry, Mr (afterwards Sir Peter) Fitzgerald. It was at once taken into the cabie-rooms by Mr White- house, the electrician, and attached to a galvanometer, when the first message was received through the entire length. Thus was this remarkable achievement carried out by Mr Hright and his able assistants, the success being attained in the face of the greatest difficulties, and after such disappointments and failures as might have daunted many. All the world was taken by surprise, and applauded not only the triumph of such determined perseverance, but also the engineering Landing the Ciible from H.M.S. "Agamemnon " l>y boat at Knightstown, Valentia I.sland, on sth August 1858, thus C<>nii)leting the First Trans-Atlantic Telegra])h. and nautical skill displayed in this triumph over the elements. In the course of a leading article on the successful completion of the work, The Times remarked that, " since the discovery of Columbus, nothing has been done in any degree comparable to the vast enlargement which has thus been given to the sphere of human activity." The Atlantic telegraph had been justly characterised by Professor Morse, the American electrician, * Partly by the desire of the Knight of Kerry, and partly owing to the local import- ance of the place, it was decided ultimately that Knightstown was to be the main station. Communication was, however, temporarily established by the main cable being laid by boats from the " .Agamemnon '' to the newly selected terminus. A branch cable (shore-end type) was then laid across the harbour, between liallycarberry and Knightstown. A few days later this was underrun out to the buoyed shore end from liallycarberry of the year before, where it was cut, and a splice effected between the seaward side and the heavy shore end. TIIK DAWN OK OCEAN TKLKGRAPIIY. 49 as "the great feat of the century," and this was re-echoed by all the press on its realisation. A knighthood honoured Charles Bright, when only twenty-six years old, being the youngest man who had received the distinction for genera- tions past. It was the first title conferred in the telegraph profession, and remained so for many years. Captains G. VV. Preedy and VV. C. Aldham were both made Companions of the Bath, and other officers received promotion, In America, Mr Cyrus Field and Captain W. L. Hudson, with Messrs Everett and Woodhouse, and Messrs De Sauty and ^tlantir Slftgi-ajh Ofompmij. . SUtlon. fleceived per the A tlantic Telegraph Company, the fitlmving Meyiage, this / X'^ day of ComlMncwi /^r -^ ^ ^eJ^ /^ Facsimile of First Message " cabled '' across the Atlantic. Laws, of the engineering and electrical staffs, received a perfect ovation both in Newfoundland and the States. In England there was much enthusiasm, and a great banquet w.is given to Sir Charles Bright and his coadjutors in Dublin ; but in the United States the excitement was almost without bounds. Congratulatory messages were exchanged between the Queen of Eng- land and the President of the United States. Noisy rejoicings, accompanied by illuminations, torchlight processions (which in New York caused the Town Hall to be set on fire), and salvoes of artillery, were universal throughout America. England was also about to celebrate in turn the so SUBMARINE TKLKGKAl'lIS. realisation of her proud dream of union between two worlds, when the signals became confused. A new and very serious fault of insulation was found to exist, which appeared to be located about 300 miles from Valentia. For a few inore days communication was maintained, with the help of Professor Thomson's new mirror receiving instruments; but on the 1st of September 1858 signals became unintelligible. A few more words were transmitted at intervals up to the 20th October, when a total of 732 messages (some of great length) had been conveyed by this cable.* The Whitehousc induction coils had onl)- been u.sed at Valentia for a few days, Daniell's cells being afterwards employed at this station, where the mirror instruments were al.so installed almost as .soon as the line was opened. At Newfoundland, on the other hand, electro-magnetic instru- ments and a relay were adopted, and here the signals were always more difficult to read than at V^alentia. For reasons which remain unexplained, the sending instruments at Newfoundland were not ready for working till the lOth of August, so that communication actually lasted only twenty da)-s, and the line was never opened for public traffic at this end. Nevertheless, the English Govern- ment had time to countermand the departure of two regiments about to leave Canada for England, which resulted in a .saving of about ^"50,ooo.t This circumstance served to demonstrate the advantages to be derived from telegraphic communication between distant lands, and largely helped the starting of other kindred undertakings. In i860 attempts were set afoot to repair the cable, but were soon abandoned, owing to the bad condition of the sheathing wires, the shore end only being recovered.* The immediate cause of the interruption * Amongst other services accomplished by this cable during the short time it was in operation, may be mentioned a message of peace and congratulation between Her Majesty and the President of the United States, besides similar messages between the corporations of London and New York. Through its instrumentality, intelligence was also conveyed (see illustration on p. 49) of the collision of two steamers of the Cunard Line — the "Europa" and the "Arabia"; and the same information transmitted to the relatives of all passengers, with an assurance of the safety of all on board. t "The Electric Telegraph" (1867), by E. 15. Bright, F.R.A.S., p. 115. I Efforts were made to recover and make good the \'alentia shore end, which, as the result of tests by Mr C. Bright, Professor Thomson, and .Mr C. F. Varlcy, had been supposed to be especially faulty. It was underrun from a catamaran raft (see illustration, next page) for a distance of some three miles, but, on being cut, no fault could he found. The idea of repairs had, therefore, to be put aside, and the cable was spliced up again. .'Vgain, in i860, an attempt was made to renew a portion of the cable near the Newfoundland end. Five miles were underrun before the cable got jammed, the bottom being very rocky. Beyond this, the e.xpedition only revealed how enormously the gutta had improved by submersion. TIIK DAWN OK OCEAN TF.I.KORArHV. SI could not, therefore, be precisely ascertained. Rlame has sometimes been attached to the electricians for applying to the cable, for sij^nalling purposes, after it was laid, a |)otentiai equivalent to 500 volts, as well as alternating magneto-electric currents, actuated by a potential even five times greater — from induction coils five feet in length ! The maximum working speed gave 105 impulses per minute with alternating currents, implying by imjjulses a succession of equidistant dots. This speed would give about 1.85 (five-letter) words ]jer minute.* With the Thomson galvanometer, however, a speed of quite three words per minute was obtained. Notwithstanding the final failure of the undertaking, three facts were conclusively demonstrated — first, the possibility of laying 2,050 nauts of cable in ocean depths of two to three miles ; secondly, that by means of an electric current, distinct and regular signals could be transmitted ■^SP^'. ' I . ■ "^fflBi m. \ '.■'",' >-■'.•,.*] Bti'tS&ailtl' ■ ■■■■ m pr^-- Hb^ f"i^,' • " i^BBH ■* ■" "„» ^^V. '■■ •^'''- Itt||ll ..IV. »• - " ■• ■ . T - ■'' ■^•■^M;-:,."^m^ ,.«« V'-HJ" ng».c. ■ t^^'m ..j,^^-«%j^^Hj^ga fct ■ •-^^ Kii.'--. -■ '^"> ^.^. "P'.UfP'iii. Unilurrunning Irish Shore End of First .Atlanlic Cable, lS6o. and received through an insulated conductor, even "hen extended beneath the sea, across this vast distance separating Ireland and America; and thirdly, that the paying-out ships could be hove to in deep water without nece.ssarily parting the cable. Thus, regarded as an engineering work, it maj- be said that the great project (about the possibility of which so man)' eminent engineers and scientists had e.xjjressed their absolute disbelief t) was successfully accom- plished as soon as the cable was laid ; and it has never been suggested * More than thirty hours were rcquireil to transmit President Buchanan's telejjram. + That eminent scientist, Professor C H. Airy, F.K.S. (.Astronomer- Royai\ liad very forcibly stated that it would be impossible to deposit the cable at so great a depth ; and that in any case it was mathematically out of the ciuestion to transmit electrical signals through such a length. 52 SUHMAKINE TELEGRAPHS. that it actually broke after submergence, the cessation of sij^nals being too gradual for this.* It is true that there occurred, during the laying, two interruptions of signals between the ships. These were much commented upon, and generally assigned to faults left by the electricians in the cable already paid out, which shortly afterwards unaccountabl)' corrected them- selves at the bottom of the sea ! When the cable passed out of the hands of Charles Ikight and his assistant engineers, and from Professor Thomson and the electricians on board, to Mr Whitehouse on shore, it was in excellent order — far better (on account of the low temperature and pressure at the bottom) than before laying. It had only been subjected to battery currents, derived from about .seventy ordinary Daniell's cells, by which all the signals were interchanged between the ships. Unfortunately for the life of the cable, Mr Whitehouse, the chief electrician — a man highly respected for his scientific attainments — was imbued with a belief that currents of very high intensity {i.e., a high potential) were the best for signalling ; and he had enormous induction coils constructed, five feet long, excited by a series of very large cells of the potent Smee type, and yielding currents estimated at about 2,000 volts ]jotential.t Instead of being satisfied with the comparatively mild and innocuous currents from the cells used on board the ships, he brought these induction coils into operation, with the result that faults were developed. The insulation was, in fact, unable to bear the electrical strain, and thus the signals began to fail gradually. Ordinary battery power was resumed, but too late, for then the number of Daniell's cells had to be continually increased, till they actually numbered 480 ! On this, the cable soon cea.sed to speak; even when using Professor Thomson's mirror galvanometer. \ . As a proof of the intense and destructive power of the induction coil currents employed by Mr Whitehouse, the following experiment maj- be * In reference to the above line, the late Mr Robert .Sabine said (in his work on "The Electric Telegraph," Crosby Lockwood and Son) :— " At the date of the first Atlantic cable, the mechanical department was far ahead of the electrical. The cable was successfully laid — mechanically good, but electrically bad." t Some of the apparatus employed by Mr Whitehouse for working this line may be seen at Messrs Elliott Brothers, the famous, and now classic, instrument makers of St Martin's Lane, London. Amongst other things, are some large condensers used in con- nection with the earth-plate carried out into the harbour at each terminus, for establishing efficient earth connection. + An unusually violent lightning storm occurred shortly after the cable had been laid. This has been spoken of as a possible part-cause of the gradual failure of the line ; also a supposed "factory fault," masked by the tar in the hemp. TIIK DAWN OK OCEAN TELIXIKAI'HV. 53 mentioned. It was carried out by Mr E. H. Iki^ht and Mr C. l-". Varley,* at Valentia, shortly after the cable broke down. A very fine prick was made with a needle in a spare length of the core of the cable, siifiR- ciently deep just to touch the conductor, which was then placed in a large earthenware jar filled with water and connected to earth, as was one end of the great induction coil. On the other end of the .secondary coil being joined to the conductor of the piece of cable, and the current applied, the interior of the jar was immediately lit up as if it were a lantern ; and on withdrawing the specimen of core, the gutta-percha was found to be melted away to about half an inch around the tiny needle puncture. The consensus of opinion was, that the fearful electric charges applied were the cau.se of the failure ; and, notwi<^hstanding the enormous improve- ments made in insulation (especially as regards the joints) up to the present time, it is doubtful whether any cable now in existence would long stand a trial with currents generated from such apparatus. Professor Thomson subsequently expressed his belief that if proper methods of handling the cable electrically had been in use from the beginning, its performance would have been lasting — and, in the main, satisfactorj'. It may be added that Professor Thomson, in 1856, previously f suggested what proved to be the more accurate requirements for working an Atlantic cable, in the course of a somewhat protracted correspondence in the columns of the Atheticeuvi. Mr C. F. Varley gave expression to similar opinions, when giving evidence before the Board of Trade Commission of i860 on the Construction of Submarine Telegraph Cables ; as did also Professor D. E. Hughes, F.R.S., who had made numerous experiments on the cable with his type-printing telegraph instrument. Profes.sor Hughes, indeed, ex- pressed the firm conviction, that a current of that intensity from induction coils was quite sufficient to burst through the gutta-percha. No doubt the primary cau.se of the failure of the first Atlantic cable was the fact of the * Mr Varley became electrician to the Atlantic Telegraph Company in succession to Mr Whitehouse, besides being associated with Professor W. Thomson. + Mr E. O. W. Whitehouse had read a paper at the ISritish Association Meeting of 1856 on the "Atlantic Telegraph." F"urther, commenting on this in a letter to the Athcmeum of ist November of that year, Professor W. Thomson pointed out, in opposi- tion to Mr Whitehouse, that the number of words which could be sent through a long submarine cable varied inversely as the square of the length of that cable ; and thus that, when the length of that cable was doubled, only one quarter the number of messages per diem could be sent through it. At another time (see Part III.), in a paper published in the Proceedings of the Royal Society and in the Philosophical Mat^azine, he gave the complete theory, shewing that on all telegraph lines a limit existed to the speed of transmission. This important paper brought to light, in fact, the now famous KR law, which has ever since prevailed. 54 SUHMARINE TELKGRArHS. core, especially the conductor, being insufficiently large,* coujjlecl with its low sijccific conductivity.f When scientifically criticising the first Atlaritic cable, regard should be had to the fact that it was made at the beginning of 1S57 — only about five years after the laying of the first Dover-Calais line. The next Atlantic cable was not constructed till a further eight years had passed, during which electrical knowledge and invention, especially in the manufacture and testing of the insulation, had advanced by leaps and bounds — not to mention the exhaustive evidence taken on the subject throughout a whole year (i860) at the afore-mentioned Hoard of Trade Commission. Any comparison, therefore, of these two enterprises is really out of the question, beyond that of passing in review the very different conditions under which the two were undertaken — the first being without any previous experience of the sort in deep water, the second after the actual laying was known to be a possibility, provided the required engineering skill were at hand. * As already stated, the type of core (besides its protective aniioui) was settled by contract before Mr Charles Bright became the engineer, and though he strongly urged the adoption of a larger conductor with thicker insulating covering, the change was not considered practicable, involving, as it would, the raising of a considerable amount of further capital. It may be remarked, however, that Mr VVhitehouse's mistaken views of a low capacity being of much greater moment than a low conductor resistance, for signalling purposes, received the entire support of Michael F"araday, the greatest electrical smui/it of the age. In any case, it was a core of far larger proportions than had ever previously been adopted, with the result that the difficulties of manufacture were correspondingly increased. Moreover, we must remember that the enormously increased depth tended to bring to light faults which might otherwise have remained dormant. li is not improbable that weak joints were the real cause of ultimate failure. A bad metallic joint— i.e., a case of the two ends of the conductor not being properly united — was not a very uncommon occurrence in those days, when no method of joint-testing was in vogue beyond a comparison of the leakage from the cable (of, perhaps, several hundred miles) before and after the union had been made. A carelessly effected metallic joint is liable to draw apart on being subjected to a strain during the operation of laying. On the strain being taken off, the ends may join together again temporarily ; but, under such circumstances, the points of contact soon become oxidised, and, thus, all communi- cation gradually ceases. This — together with a gradual percolation of water is, perhaps, more likely what took place in the case of the first Atlantic line than any other of the explanations for the subsequent cessation of signals. Faults of insulation are scarcely ever of such a character as to account for signals being entirely stopped, and it is never suggested that the cable actually broke. t The purity of copper in those days was so low that an electrical conductivity of 40 per cent, was as much as was ordinarily obtained for telegraphic purposes. However, between the expedition of 1857 and 1858, Professor Thomson drew attention to the importance of this matter, whilst pointing out (for the first time) that all copper had not the same conducting power. He also established a system of testing samples such as had T beneficial effect in the direction of increasing the electrical value of the wire obtained, by the last 400 N.M. being composed of copper of a higher degree of purity. Tin; DAWN OF OCEAN TKLECKArHY. 55 The first Atlantic cable has been dealt with here in a complete form, not only in the li^ht of an engineering feat and the first successful attempt of its sort, but also as a great commercial undertaking, which it might be well supposed— considering the doubts expressed by various eminent engineers— would be a tremendous task to obtain supporters for. This work paved the way, by demonstrating the possibility of trans-Atlantic telegraphy, an idea almost universally scouted at the time. Ju.st as the notion of an .\tlantic cable had met with great opposition from the incredulous, so also it formed the subject of much enthusiasm at the hands of the amateur engineer. No sooner was the project started than would-be inventors were all agate airing their various — more or less fantastic — notions. One suggested suspending the cable from the bottom (a little below the surface) by buoys or floats at regular intervals, so that ships might telegraj^h from them en passant* Another gravely proposed to festoon it across to America by balloons. Not a few of these schemes were based on a somewhat prevalent belief of that time— ;>., that no cable would properly sink to the bottom, and that it would in consequence be liable to impede the passage of ships ! Then, one enthusiast wished to see parachutes attached to the cable during paying out " to avoid too rapid sinking through the water." A naval officer of eminence (now Admiral J. H. Selwyn, C.B.) devised a huge iron cylinder, around which 2,500 tons * Hy this plan, the buoys were to be held entirely under water (Fig. 26) by moorings from the bottom, their position being indicated by small "watch-buoys" at the surface, fitted with flag, night light, and telegraph apparatus. The idea was fascinating, but its Fig. 26. — Proposal to buoy the Atlantic Cable at Interval Stations, for Ships to communicate from. realisation impracticable. Putting aside the enormous difficulties which would have attended the laying and working of such a cable, the buoys (as experience has since amply shewn) would soon have got adrift. Moreover, the cable would not take long in I liafing away at the points of suspension. " Monsters of the deep " would also probably find a line of this character more irksome to them than one lying continuously at the bottom. 56 SUMMARINE TKLKGKAI'IIS. of cable were to be coiled. It was then to be towed across tlie ocean, payinj^ out the cable as it went. Some, a^ain (several times over), absolutely went so far as to patent the conversion of the laying; vessel into a huge factory, so as to make the cable on board in a continuous length, and submerge it during the process ! * These were the kind of " wild notions " (as we now naturally characterise them) which the responsible engineers of that period had to deal with — and deferentially too. ■"■ The main object Ncre was to avoid joints, as well as to obviate tlie risk of damage between tlie operations of maniifarture anil layinj^. Telegraph House at Trinity Bay, Newfoundland, 1858. HIE DAWN OF OCKAN TELKGRAI'IIY. $7 Skction 2.— liiK Ri.D Ska ami Kast Indian Tkliuikai'Ii. Ill 1.S5- Mr Lionel (iisborne, havinj; obtained lowers from the Turkish ("lovcriuncnt to carry a teloi,n-aph line across h'-^')'!)! aiul lay a cable in the Red Sea, promoted the fonnation of the " Red Sea and India Telc^rraph Company," with a view to establishing communication between Kngland and her Kast Indi.u. possessions. The importance of this line, and the reverses which the Atlantic Telegraph Company at first met with in this same j-ear, weighed with the British (Government, which now decided to give its assistance. In 1 858 a somewhat similar guarantee* of dividends was "ranted to the new association as had been (in the form of a subsidy) for the " Atlantic " Company. The proposed line, 3,043 miles in length, between Suez and Kurrachee, was divided into two i)arts. The first portion, from Suez to Aden (1,358 N.M.), with intermediate landings at Kosseir and Suakin, was laid in 1859. The different sections of this cable broke down one after the other. They were all laid very taut, the slack in some cases being of less than unit value.t This though the bottom was, in certain parts, extremely uneven ; moreover, the type of cable adopted was of a distinctly fragile character for some of its rough resting-places. The Suakin-Aden section was first repaired in i860; but another interruption occurred a few days afterwards. A portion of the cable picked up was found to be covered with shells and marine growths* which, in some instances, had preserved the iron from rust ; in many other cases the outer sheathing was completely worn through by the rocks on which the cable had rested. The second portion of the line, from Aden to Kurrachee (1,685 miles), with intermediate landings at Hallania Island and at Mu.scat, was laid during the year i860, at certain points in depths of 2,000 fathoms, the slack working out at o. I per cent, over the entire length. Faults developed very quickly in all three .sections ; and the company, having neither specially * Eventually a subsidy was granted, which cost British taxpayers ^36,000 per annum. t ]iy the agreement of this undertaking, the surplus cable belonged to the contractors : no wonder that faults soon developed which it was impossible to repair 1 In some places, owing to the tightness and high speed of laying, the elongation of the iron wires had "nipped" the gutta-percha; and, in others, the sheathing was much stretched and "broken. t See illustrations at foot of page 190. These figures may be taken also as repre- senting the state in which cables are very generally found after submergence for a certain length of time in those localities which are pervaded by marine growths of various descriptions. 58 SUHMARINE TKLEGKAPHS. qualified men, nor the necessary materials, for carryinjf out repairs, was obliged to abandon the line, before any commercial use had been made of it* The cable was manufactured and laid b)' Messrs Newall, the conductor being a strand of seven copper wires equivalent to 180 lbs. per N'.M. IHie insulation consisted of two layers of gutta-percha, alternating with two coatings of Chatterton's compound,f a substance (of high insulating qualities) more plastic than gutta itself, and intended to ensure better adherence between the gutta and the copper, as well as between the la)'ers of gutta-percha themselves. The total weight of dielectric was represented by 212 lbs. per N.M. The core was encased in tarred hemp and eighteen iron sheathing wires of No. 16 gauge. The outer sheathing of the shore end was composed of nine iron wires of No. 2 gauge. The working speed — during the thirty days' trial J — between Aden and Hallania, the longest section (718 N.M.), was five words ]jer minute. Messrs Gisborne and Forde were the engineers,§ and Messrs Siemens and Halske the electricians of this enterprise,;; Mr Werner Siemens being out on the expedition.li * This was a most unfortunate line in every way. Report has it that a complete message was never got through the entire length, but only through each section separately. It ultimately failed altogether. + This compound was the result of exhaustive experiments by Mr Willoughby Smith. Coal-tar naphtha had been previously used for adhering the successive coats of gutta- percha, with prejudicial effects owing to being a rapid solvent of that inaterial. This compound, which has been almost invariably employed in all successive cables, is com- posed of certain proportions of Stockholm tar, resin, and gutta-percha. I This was the first instance of a stipulated length of time for testing the cable after submergence, previous to taking it over from the contractors. This particular perii- were allowed to pass. The length of cable laid between Port Vendres and Minorca was 226 miles, and that of the cable laid the year before between Minorca and Algiers 230 mile.^. Signals were sent through the whole length with the help of Siemens' polarised relay, setting into action a local battery for influencing the Morse recording coils. The working speed was eight words per minute, and on "trials" thirteen words. This cable broke down, between Minorca and Algiers, on the 25th of September 1862, on the occasion of a violent storm. V few attempts with insufficient appliances were made to raise it, but were soon given up. Cable from Oran to Cartagena. — Nothing daunted by the failures of the cables to Corsica and Algeria, the French Government persisted '■ -. .- , ■', ..■.■..'■,. . Fui. 29. : : ■ ■ " in the idea of telegraphically connecting, by a submarine line, their great African colony with the mother country. In order to lessen the expense, the advantage of direct and independent communication was given up, and it was decided to land the cable on the southern coast of Spain. After soundings had been taken during July 1863, Oran in Algeria, and Cartagena in Spain, were chosen as the terminal points of the new cable, the distance between them being only about 113 N.M. Outwards from both shores the depths increased rapidly to about 1,000 fathoms, after which the soundings kept tolerably regular, the greatest depth met with on the proposed track being about 1,400 fathoms. At this depth there was found to be an excellent bottom of soft ooze. The French Government entered into negotiations with Messrs Siemens and Halske to manufacture* and lay between the places mentioned a cable of a type made and ex- hibited by them in London in 1862. The core (Fig. 29) was a strand of three copper wires, No. 16 gauge, covered with two layers of gutta- * This was the first cable made at the newly-established factory of Messrs Siemens Brothers on behalf of Messrs Siemens and Halske. THE PAWN OF OflCAN TKLKGKAl'HY. 69 pcrcha to No. 2 gaiijjc. The deep-sea portion of this cable was constituted by the core being surrcjundcd with two coverings of stout hemp line wound in opposite directions, with a very long lay, almost |jarallel to the axis of the cable ; round the whole, flexible strips of copper were laid, the spirals of which overlapped like the scales of a fish. For this metal taping, copper containing phosphorus was used, which has the aflvantage of not being prejudicially attacked by sea-water. The total diameter of the cable was only 0.43. For the shallow-water portions, the hempen covering was increased in thickness, .so as to bring the diameter up to a little over half an inch. In the case of the shore ends, the copper ribbon was replaced by the ordinary iron wire sheathing. It should be mentioned here that (although Messrs Siemens were probably unaware of it at the time) this method of protecting submarine Viu. 30.— I 'aying-out Apparatus for Oran-Cartagena Cable, 1864. cables by wrapping them spirally with overlapping strips or ribands of metal was invented and patented by Messrs E. B. and C. T. Bright eleven years before— No. 14,331, 2ist October 1852— with full de.scriptions and draw- ing, coupled with a claim for the use of such spiral overlapping metallic ribands, and further improved by the addition of a washer to give flexibility.* * This fact was referred to subsequently at page 282 of M. Wunschendorff s " Traite de T^Mgraphie Sous-Marine," on which this work is partly based. M. Wiinschendorflf gave credit to the Messrs Bright as the actual inventors of this system, which has been, and is, so extensively used, though Messrs Siemens were the first to apply it, in the above case, as the sole protective armour, forming, with the hemp bedding, a light cable for deep-water recovery purposes. It may also be mentioned that subsequently Mr Henry ClifTord adapted a form of metal riband (or tape) outside the core of cables to the special purpose of protecting the JO SUIIMARINK TKLKCIRAI'IIS. The cable was shipped on board the " I)ix-I)cccinbre " * a small steamship, bought by the French Government the year before, and fitteil up in ICnjfland for submarine cable work. Her deck machinery {\'\^. 30) consisted of a lar^fe drum A keyed on to a shaft which also carried two brake wheels It ; each of these wheels was surrounded by a series of wooden blocks, kept in place by encircling' bands of iron, which could be tightened or eased up by hand with a double-threaded screw c. These bands were supjiorted below by an arm pivoted at one end to a strong block, and hung at the top by a powerful spring K which could be made to lift the blocks off the drum, allowing it to revolve frtcly when the brake straps were slackened. P'orward by the drum was the V-whecl i', surmounted by a jockey wheel which was loaded with a detachable weight II. The cable coming out of the tanks in the fore part of the vessel was guided, where necessary, by sheaves and rollers, and passed through the space left ! w KiO. 31. — Sailer's Balance Dynamometer. between the V-wheel and the jockey ; the weighted jockey wheel acted as a brake, and straightened out the cable before it reached the drum, ^o that the turns could not ride one on the top of the other. A knife arrange- ment, fitted flush to the drum on the fore side, continually forced the turns towards the centre of the drum, thus making room for the new turn coming on. Abaft the drum came the dynamometer (Fig. 31), of a special design, due to Sir Charles Bright, and fitted for the first time, in 1867-68. by Mr F. C. Webb, M.Inst.C.E., on board the " Narva." It consisted of a flanged same from the ravages of the teredo and other marine insects in their attacks on the jute or hemp serving. This precaution has met with complete success, and is universally resorted to for cables in waters frequented by boring insects of any description, the first example being the Penang-Malacca cable laid in 1879. * This vessel, still employed in repairing cables in the Channel, and along the western seaboard of France, was renamed the " Amp6re " in 1870. TIIK DAWN OF O' KAN Ti;Li:(;KAri I V. 71 frillin^r A, turning on an axis supported by i inch of a braced lever (witli lattici-d franic\vori<) pivoted at li. The other end of the lever was connected to a Salter's balance, suspended from a frame W. The length of the lever arm It c was five times that of a m, and the apparatus was adjusted so as to remain horizontal when in normal equilibrium. At equal heights and distances, before and abaft, two fixed wheels with flanges ^vere fitted, I) and I, ; the cable passed over each of these, and under the dynamometer wheel A, between them. TIk; wheels I) and L were so placed that the cable made p an angle with the horizontal of about 14 31', the sine of which being \ when the dynamometer was in its _ _ normal position (Fig. 32). Resolving . „ • ■ > ' " , Ik;. 32.— Dynnmometnc Principle, by parallelogram of forces, the ten- sions OM and ON, equal and oppositely inclined at the point O, the length of the resultant was found as follows : — . *^^ = OM X sin. MOH = OM x JOP = AOM. 2 Therefore, the vertical force tending to lift the dynamometer wheel was always exactly half the strain on the cable. The length of the lever arms A li and n C being as i to 5, the weight shewn on the Salter's scale was only a fifth of the upward thrust, which it balanced at the other end of the lever, and consequently only a tenth jf the strain on the cable.* The sheave L (Fig. 31) guided the cable over the ship's stern, and was furnished (as nowadays) with two check pieces, to prevent injury by the sharp edges of the sheave when the cable left the ship in a direction not parallel to the fore-and-aft line. Another similar sheave was placed on the same platform, immediately above the stern of the vessel, and was used for picking-up purposes. The cable — carried aft over portable sheaves suspended from the rigging — took three turns round the drums, and then went to one or other of the tanks, following the same leads, but in reverse order, as the cable when paying out. By means of a connecting clutch, a pinion wheel, driven by a small deck steam-engine, could be geared into a large toothed wheel keyed on the .same .shaft as the drum, the paying-out machinery being thus trans- formed into a kind of huge steam winch. The cable was hauled away from the drum to the tanks by manual labour. Whilst paying out, the steam- * The principle of the dynamometer used at the present time in cable operations is the same as here stated, and the form of it is, practically speaking, also the same. 72 SUBMARINE TELEGUAl'HS. engine was disconnected, and used to work a pump for the purpose of throwing a continuous stream of water over the cable and the brakes. In order to obviate as far as possible the formation of kinks, and the difficulties experienced in the tanks when the cable passes rajjidly from the outer turn of one flake to the smaller inside coils of the next, Mr C. VV. Siemens wound his cable on a large drum with a vertical axis, having a plat- form at each end.* The drum revolved on cast-iron rollers placed between two circular rails, one of which was bolted to the lower platform under- neath, and the other secured to the hull of the vessel. The upper end of the vertical shaft carried a toothed wheel, which was turned by the deck engine, the power being transmitted by a system of cogs and chain pulleys. The laying commenced on the I2th of January 1864. After proceeding a few hours the cable broke, on the occasion of a stoppage caused by a derangement of the great reel. The tremendous weight of the reel soon bore down the rollers, which became flattened in places, offering great resistance to turning. Mr Siemens then gave up this method of paying out, and the cable was coiled in a tank.f On the 28th of January a second start was made, paying out at first very slowly ; afterwards the speed wds increased, little by little, till it reached six knots, and even more. When twelve hours had elapsed the cable parted in deep water, and was abandoned. At the moment of the accident the dynamometer shewed a strain of only 6J cwt. .A third attempt took place in the following September. All the deep- sea cable was successfully laid, but a break occurred about ten miles from Cartagena just when the end was being landed. It appears that, in order to avoid running short of cable, too little .slack had been paid out on approaching the Spanish coast, where the water ".shallows" very rapidly. Thus a considerable portion of the cable may have been suspended over sharp ledges of rock, which would account for the sudden breakage. More probably, however, this was due to too great a strain being applied in tautening what was an exceedingly weak cable to start with. Some miles were picked up, but without reaching the break, for the cable again parted in goo fathoms. After twenty days or so had been pas.sed in unsuccessful dragging, further operations were abandoned. * Similar measures had previously been taken, with the same end in view, over the first (1850) Dover-Calais cable. + It is for the above reason that cables are now invariably stowed in tanks, instead of on drums, aboard a cable-layinj; ship, as well as on account of the obvious economy of space, where any considerable length is in question. TilK DAWN OF OCKAN TKI.KCRAI'IIV, 73 Thk TeleCxRaph to India. [From the " lllustraud LoHiion A'cTi'i." The Indii-lAiiopcaii Tclej;raph : Landing the Calile in the Mud at Kao, Persian Cliilf. The cables laid by Messrs Newall and Co. in the Red Sea, in 1859, and remaining unrepaired and abandoned,* the Indian Government, in 1863, determined to undertake on its own account the establishment of telegraphic communication with Europe.+ However, with a view to make the submarine portion as short as possible, and to avoid deep water, they decided to h'mit themselves to laying a cable in the Persian Gulf, along the coast of lieloochistan, thus guarding the line of cominunication from the vandalism of the barbarous and unconquercd natives of these parts. The landing- places selected were Kurrachce, on the frontier between India and Mekran, and Fao, at the mouth of the Shatt-el-Arab River, formed by the union of the Tigris and Euphrates. The cable, with a total length of 1,450 miles,* was divided up into four sections, the intermediate landing-places being Gwadur, Mus.sendoin, and Hushirc. A land line, passing through Bussorah, Baghdad, Mosul, and Diarbekr, would convey the messages from I'Tio to Constantinople,^ and thence to the already established Turkish land-line * In spite of the efforts of a company formed to put the line through. + The late, and hif,'lily esteemed, Colonel Patrick .Stewart, R.K., C.B., was the Director- General of Indian Telegrajilis at the time. He was assisted by Colonel (ioldsmid, now Major-Cieneral Sir K. J. (ioldsmid, C.15., K.C.S.I., and by Major (afterwards Sir J. U.) Hateman-Chanipain, R.E. Si«' Frederick Goldsmid wrote an interesting book on this subject, entitled " Telegraph and Travel " (Macmillan and Co.). + Weighing no less than 5,028 tons, and representing by far the heaviest length previously despatched on one expedition. S This cable system being only connected w ith Europe by land lines through I'ersia on the one hand and Arabia and Turkey on the other, the traffic was at tirst very slow, but better than taking a month to communicate with India by steamer. 74 SUBMARINE TELEGRAPHS. system, as well as of the respective Kuroj)eaii Governments. The form of cable decided on by Sir Charles Bright and Mr Latimer Clark (as engineers to the Government), and manufactured by Mr W. T. Henley, differed in certain important and novel particulars from all previous types. With a view to combining the mechanical properties of a strand with the electrical advantages of a single solid wire,* the copper conductor was formed of four segments or segmental bars — i.e., a quadrant of a circle in section (Fig. 33) — fitted into one another and drawn into a copper tube, to hold them together. The whole was then rolled and drawn down to a straight and absolutely circular wire (or rod) of the requisite size — apparently solid but in reality multiple in construction, and consisting of five (.'.istinct pieces. Sir Charles Bright had previoush* devised a wormed conductor to meet the same ends ; but Mr Clark's, here described, was at that time considered preferable.+ The weight of the conductor so formed was 225 lbs. per naut. The copper was specially tested, and the mean conductivity was as high as 1S9. 14 per cent, whereas the maximum conductivity at the time of the first Atlantic cable was only 45 per cent. The conductor was then taken in hand by the Gutta- percha Company, who covered it with four coatings of gutta-percha, alternated by the application of Chat- Fir.. 33.— Diagram to tcrton's compound, weighing 275 lbs. per N.M. The shew Building-up of finished core was tested in three-mile lengths, under t'^^"i86^' onii'c- water, at 75' F. ; and also under pressure of 600 lbs. to the square inch. Mr Latimer Clark's well-known " accumulation method " * was used for the first time in electrically testing the joints. Not only is this the only joint test of any value, but it was the first occasion on which the joints in the core of a cable were tested at all. Indeed, the joints themselves had hitherto been of .so rough a character that they would scarcely bear testing, and had the effect of seriously lo. ering the insulation resistance of the early cables, which would otherwise — owing to the excellence of the manufacture of gutta-percha at that time — have been abnormally high. For the covering of tarred hemp, which had been found to temporarily and partially conceal defects of insula- tion, Mr Willoughby Smith's plan was adopted of substituting tanned hemp. * By the smaller surface, etc., for a given quantity. of copper, of a truly circular conductor. t The wormed conductor of .Sir C. Bright consisted of several wires stranded together, some of which were of a small gauge for the purpose of fitting into the interstices of the larger wires, the whole being tirawn down to a tubular form. X .See "The Telegraph to India, and its Extension to Australia and China," by Sir Charles Tilston Bright, C.E., M.F. THE DAWN Ol' OCKAN TKLIXlRArilV. 75 which would retain moisture, and thus, being a ready conductor, would tend to show up any incipient faults at an early static during manufacture.* This was the first occasion, moreover, on which the ser\ed core was kept con- tinuously in water-tanks until required for sheathing ; thus securing, by frequent electrical tests taken under proper conditions, the detection of any faults up to the last moment before the application of the armour. The outer sheathing consisted of twelve galvanised iron wires of No. 2 B.W.G. To help to preserve the wires from rust, and to prevent the accidents so frequently occasioned by broken wires when passing through the paying-out machinery, the sheathing was covered wilh two servings of hempen j-arn, wound on in reverse ways. This outer co\ering was impregnated with a bituminous preservative compound,+ just previously introduced by Sir Charles Bright and Mr Latimer Clark,* which was applied warm whilst thoroughly plastic, and was a mixture § of certain proportions — to be varied according to circumstances — of mineral pitch, tar, and powdered silica, the last ingredient being incorporated as an e.xtra safeguard against teredoes and such like. Finally, the cable was led through semicircular rollers, by which the coating of compound was thoroughly pressed into all the interstices of the wires. Fig. 34 represents the deep-sea type of the finished cable. To prevent the adjacent turns and flakes in the tanks sticking together, ' the cable was "whitewashed."* Among other advantages derived from this outer j-arn '* This process consisted of impregnating the jute (or hemp) with a solution of catechu (or " cutch," as it is often termed), a bark containing; a large quantity of tannin ; hence the jute so prepared, by immersion in "cutch" solution, is nowadays very often described briefly as tanned jute. Though an excellent antiseptic and preservative against decay under some conditions, the tarring of the yarn had been found also to have the effect of lowering the insulation, besides sometimes having a detrimental action in the case of jointing. + The outer yarn serving may be also regarded as a vehicle for the compound, some mixtures of which (under certain conditions) would not "take ' on the iron wire direct. I This was under a patent of Sir C. Bright — No. 538 of 1862 — as a further preservative of the sheathing wires beyond that secured by previously galvanising them; and a full reference to this caLiC compound, and the method of applying it, will be found in Part II. of this work. Its first application to the above cable was dwelt on at length by the present writer, in the course of some remarks in \\\>t Journal of the Society of Arts iox i6th February and 9th March 1894. (.See also "The Telegraph to India," by Sir Charles Bright, vol. xxv., Proceciiiiii^s of the Institution ofCii'il Engineers.) S Being to some extent waterproof—and partially air-tight— a compound such as this is supposed to prevent the free circulation of water, with the result that but little oxygen is present : the iron wires cannot, therefore, be materially exposed to oxidation. II Thus causing a foul during paying out. II This external coat of litne— or chalk— and water was involved by the introduction of the compounded yarn (or canvas) outer covering. Previously, where the external wires had received an outer coat of tar, the turns had no inclination to stick— indeed, for paying-out purposes, the cable was too slippery rather than too sticky. 1^ SUItMAKIM-: teli:grai'h.s. serving, the cable was found to be more flexible and to coil better in the tanks, facilitating the pa\ing out in laying. The total weight of the cable was 4 tons per naut. For the shore-end portions the sheathing wires were materiall)' increased in thickness, bringing the weight uj) to 8 tons per X.M. The cable when finished was coiled in tanks filled with water, and a series of electrical tests made for conductivity, insulation, and electro-static capacity. Finally it was placed in water-tight tanks fitted on board five large ships, and taken round the Cape to India bj' Sir Charles Bright, with his able staff, including Messrs J. C. Laws, F. C. Webb, F. Lambert, and others.* This cable was very successful!)' laid, but not without difficulties. At Khor Abdullah, for instance, at the mouth of the Shatt-el-Arab, the flotilla was anchored with six to eight miles of mud banks between the ship and the shore. As the cable could only be landed in a flat-bottomed vessel, a small craft named the "Comet" was requisitioned, belonging to the Bombay Marine Service, and emploj-ed in running between Bussorah and Bombay. In order to make room for the cable, she had to disembark her guns and coal, the o|)eration occupying as much as fourteen daj's. On the banks of the Shatt-el-Arab the mud was .so soft that Sir Charles Bright and his men had to dr?.g the cable to the shore partly crawling on their stomachs (see illustration on page 73). Kven when the solid part f)f the bank was reached which separates Khor Abdullah from hao, the cable required to be cut into mile and a half lengths, carried on the backs of several hundred Arabs engaged for the pur|)ose, and then joined up again. The.se difficulties of landing the cable had scared}' been overcome when a fault occurred in the Fao-lUishire t section. The necessary repairs were, however, quickly executed. Fk;. 3.1. — rcrsiiUi Gulf Cable (.Main T) pt). * Mr F. C. Webb (who subsequently remained to carry out deviations and com- pletions as well as station arrangements) was Sir C. Hright's chief assistant engineer. Mr J. C. Laws acted as chief electrician, Mr F". Lambert being his principal assistant. Dr Essclbach was also engaged on the electrical staff up to the time of his lamented death. t At the latter a specially heavy shore end was subsequently laid containing two cores (each jointed to that in the cable on each side), so as to make one cable do service THE DAWN OK OCKAN TELEGKAl'IIV. 77 This was the first cable expedition in which Morse flag and lamp signalling were made use of by day and night respectively.* On no section of the cable was the insulation after immersion less than 300,000,000 ohms (300 megohms) per naut, and the conductor resistance nowhere exceeded seven units per naut. Such satisfactory results were .solely due to the exercise of minute and incessant care and testing during construction and laying of the cable; indeed, it may be said that a systematic course of electrical testing whilst in water-tight tanks originated with this undertaking.f The whole of this work was carried out by Sir Charles Bright personally. ;J: This was the first instance of any great length of cable being a complete and lasting success; and it was certainly due, in a large measure, to the many novel and improved methods introduced in its manufacture, and to the complete system of electrical and mechanical testing here applied. liy the (late of laying the above cable — forming the first telegraphic connection between the United Kingdom, Europe, and India — the science of constructing and L'U'ing submarine telegraphs was pretty definitely worked out, and no very striking departure in general principles has since been introduced ; indeed, the pioneer stage may be said at this juncture to ha\e reached its termination. It has been thought well, however, to continue the history up to the present date. for the circuit in each direction, thus reducing the chances of interruption due to anchorage. This was eventually siiifted to Jask, but this form of T-piece (compared with that of more recent practice) could never he regarded as very satisfactory, for in the event of a breakdown, and during the necessary repairs, it involved the interruption of tratific on the two sections immediately on each side, instead of on one only. * Captain (now Vice-.-Vdmiral) 1'. H. Colomb, K.N., had a short time previously suggested the aoplication of the Morse code of telegraphy to flag and lamp signalling for the navy. + 1 his was, no doubt, largely due to the fact that the perfected reflecting galvanometer for testing purposes had only just been devised by Professor 'I'homson, also his marine galvanometer with cast-iron magnetic screen. 15oth of these— now in everyday use — were employed on this occasion for the first time in practice. I See "Bright on the Tclegrai)h to India," i/nW., and "Old Cable Stories Retold," in The Electrician^ 1896, by F. C. Webb. CHAPTER III. DEVKLOl'NrENTS. Section i. — Renewed Attempts at Trans-Atlantic Telegiapliy — Scientific Committee — Electrical Qualifications for Speed — Raising of Capital — Contractors — Type of Cable —Electrical and Pressure Tests — Construction and Shipment — S.S. "(Ireat Eastern" — I'ayinK-out Machinery — Staff — Landinj^ Shore End at X'alentia — Laying— Mis- fortunes — Core Pierced by Broken Sheathing Wires — Attempts at Recovery — Return of the Expedition. Preparations for a Fresh Attempt —" Floating" of "Anglo-.-Vmerican" Company — New Cable — Alterations made in the Picking-up and Paying-out dear — Willoughby Smith's Testing System— Use of Signalling Condensers— Staff and others accom- panying E.xpedition — Landing Shore End at \'alentia — Laying — Fouls in Tank during Paying out — Arrival of "("ircat Eastern" in Trinity Hay, Newfoundland — Landing Shore End at Heart's Content — Successful Completion — Rejoicings. Recovery and Completion of the 1865 Cable— Plan of Campaign — Failures — Success at Last - Paying-out towards Newfoundland — Another Broken Sheathing Wire causing Fault and Foul — Completion of Line— Honours Bestowed— Instance of Na\igating Skill tlisplayed by Captain Moriarty — Electrical Condition of the Two Cables- Speed of Working — SubseL|uent Failures. Section 2. — .Anglo-Mediterranean (1868) Direct Cable from Malta to Alexandria — French .Atlantic, 1869 — British-Indian Line — British-Indian Extension — l>ritish- Australian — Marseilles, .Algiers, and Malta — P'almouth, Ciibraltar, and Malta— Indo- European Line — (ireat Northern System — West India and Panama Cables — Culja Submarine — Direct .Spanish— Formation of Eastern and Eastern Flxtension Telegraph Companies — Black Sea Line — Submarine Cables Trust — (llobe Telegraph and Trust Company — Duplex Telegraphy applied to Cables — Brazilian Submarine Line- Western and Brazilian — Central American — Platino Brazilicra — .Amazon River Cables — D.U.S. "Atlantic" — West Coast of America — Eastern and South African — " P.Q." .Atlantic— Jay ("lould Cables— Mexican Cables — Central and South American — Pacific and European— Spanish National — West African — African Direct— Com- mercial (Mackay-Bennettj Atlantics — Italian Ciovernment Cables of Pirelli — French Cables in West Indies, North Coast of South America, and elsewhere— Halifax and Bermudas Line — South .American Cable Company's Trans-Atlantic System — Azores Cable— New Caledonia (French) Line — New "Commercial" and ".Anglo" Atlantics, 1894— .Atlantic Cable Systems— (leneral Retrospect. Section i.— The Second and Third Atlantic Cables OK 1865 AND 1866.. 1 ■ Since the 1858 cable ceased to work, the promoters of Atlantic tele- graphy, with Cyru.s Field at their head, had never for an instant relin- DEVELOl'MKNTS. 19 quished hopes of establishiiii^f a more permanent line.* The Atlantic Telegraph Compan>-,+ whilst biis>- endeavouring; to raise fresh capital, had S.S. "(Ileal Kasteni." prc\ai!ed on the British Government to despatch two vessels to further examine the ocean flf)or 300 miles out from the coasts of Ireland and * After the failing of the 1858 cable, several schemes for fresh lines on new routes were brought forward. One of these was known in i860 as the " drancl North Atlantic Telegraph," its object being to reduce the continuous length by laying a cable in four sections, bringing into use the inhos])itable regions of Iceland and Greenland. The cable was to go from the extreme north of Scotland to the Faroe Islands, hence to Ice- land, from there to Greenland, and so to Labrador. A project of this character had been originally brought to the notice of the Danish Government by Mr Wyld, the geographer, some years previously, and again, in a ditferent form, by Colonel T. P. Shaftner, an .■\merican electrician of some note. This received fa\ourable sup|)ort from Admiral Sir Leo])old M'Clintock, K.C.B. ; Captain (now Sir Allen) Young, C.H. ; Captain (afterwards Rear-Admiral) Sherard Osborn, R.N., C.B. ; Dr John Rae, Dr VVallich, and others of Arctic expedition fame, who had explored the route ; as well as partially by Sir Charles Bright, who drew up a report on the subject. In 1861 various papers were read at the Royal Geographical Society, calling further attention to the matter, and bringing m light the result of additional investigations. Ultimately— from the result of surveys, etc. — it appeared that the prevalence of ice, and the unsuitability of the proposed landing-places as habitable stations for the operative clerks, were sufficiently serious objections to render the scheme impracticable. Another project which attracted some attention about the same time was described as the South .Atlantic Telegraph. This was for a cable between the south of Spain and the coast of Brazil and British Guiana, touching at various islands on the way, and stretching on to the West Indies and the United States. Being, however, to a great extent foreign in its scope, this scheme found little favour with those who promoted such enterprises ; and this remark equally applies to similar projects — apart from other reasons. t This company had been kept alive mainly by the eftbrts of Mr (afterwards Sir Curtis; Lampson, the vice-chairman, aided by the secretary, Mr George Saward, as well as by Mr Field (the general manager) in both countries. 80 SUHMAKINK TELEGKAl'lIS. Newfoundlaiul respectively. The expedition of H.M.S. " I'orcupinc," in 1862, to explore the western end of the Atlantic, in about the same latitude as Ireland, is still famous. It was found that the sea-bottom in this vicinity, instead of forming a precipice, as had been supposed by many, had in reality a \ery ^^cntlc slope. It took, however, a considerable time to raise the full amount of capital required for another Atlantic cable, and this could only be done j,fradually. The great Civil War in America stimulated capitalists to renew the attempt. Mr Cyrus Field, who compassed land and sea incessantly,* pressed his friends on both sides of the Atlantic for aid, and constantly agitated the question in London and New York.+ When it was estimated that a sufficient advance had been made, the directors of the " Atlantic " Company (Chairman, the Right Honourable James Stuart Wortley) .sought the a.ssistance of certain independent scientific gentlemen as a consultative committee to advise them upon the electrical and mechanical questions involved in the proposed unilertaking, with especial reference to the form of cable to be adopted. This committee (partly drawn from the members of the Government Commission already alluded to) was composed as follows : — Captain Douglas Galton, R.E., F.R.S. ; William Fairbairn, I\R.S. ; Professor W. Thomson, F.R.S. ; Pro- fessor C. Whcatstone, I'.R.S. ; and Joseph Whitworth, F.R.S. These gentlemen had under their consideration a number of proposals, and in the end the somewhat considerable experience of Messrs Glass, Elliot, and Co. was thought to be a strong point in their favour as proposed contractors, especially as they had tendered a very large number of samples for the benefit of the committee's consideration of the subject. The previous Atlantic cable had forwarded the possibility of communi- cating intelligence at a great distance and at a fair rate of sjjeed by di.sclosing, in a practical way, the laws of resistance and electro-static capacity as affecting the speed of transmission in working submarine cables of great length. It also suggested the best means of reducing to a minimum the effect of retardation of signals due to those laws by a mathematical adjustment of the conducting and insulating con.stituents * Mr Field is said, indeed, to have crossed the Atlantic sixty-four times -suffering from sea-sickness on each occasion— in connection with the various Atlantic cable enter- prises in which he formed so prominent a figure. t One of the main advant.iges pointed to on this occasirn was the avoidance of mis- understandings between the two countries. Another (intended as a special attraction to Americans) was the improvement of the agricultural position of the United States, by e.xtending to it the facilities, already enjoyed by France, of commanding the foreign grain markets. On this latter account, the project was warmly supported by the late Right Hon. John Bright, M.P., and other eminent Free Traders. DKVELOI'MENTS. 8 1 of .1 cable, both in ii f^ivcn ratio to themselves and relatively to the length of the line to be constructed. Again, Professor Thomson had pointed out in the columns of 7"//t' Atheiueuin the mistaken notion which had |)reviously found favour (sup- ported by F'araday, amongst others) regarding the requirements for obtaining a given working speed for submarine cables of certain length. It was partly, however, left for Mr S. A. Varley to put the matter correctly in a complete, yet non-mathematical, form ; and this he had very ably done in the course of a paper read before the Institution of Civil Engineers,* and also in another before the Society of Arts,t .some years previous to this i)roject. The main point of Mr Varley 's paper (as well as of Professor Thomson's contributions) was to shew that the signalling speed attained on a cable depended not only on the electro-static inductive capacity (as seemed to have l)een imagined by many), but also equallj- on its conductor resistance. * It was now ab.solutcly manifest that the circumference of the conductor and the thickness of the dielectric should not only bear a certain relation to one another for purjioses of low capacity, but also that — in order to put a limit on its resistance — tiic conductor must not be smaller than a given diameter according to the length. Mr Cromwell Varley had also spoken before the Government Commission § to the same effect; and Professor Thomson eventually laid down definitely the well-known law for speed through a cable as depending, on the one hand, inversely on the conductor resistance, and also inversely on the electro-.static capacity of the system. ![ Thus it came about that the type of core recommended by the Telegraph Construction and Maintenance Company (formerly Messrs Gla.ss, Elliot, and * "On the Electrical Qualifications requisite in Long Submarine Telegraph Cables," Minutes of Procccdint^s, Iiistiiulion of Ch'il En^^ineers, \ol. .wii. '^ Journal of the Society of Arts, vol. vii. X Mr Varley went further than this, indeed. He shewed that by doubling the diameter of a wire, whereas the conductor resistance became a fourth of what it had been (by the sectional area being quadrupled), the circumference being only doubled, the electro-static capacity would be but twice what it was before. The result is that, as these two are equal factors in the speed, by doubling the diameter of the conductor and providing for the same thickness of dielectric, the working speed admissible on a given cable is twice as ini":h as previously. S This Commission had been arranged more especially with a view to considering the best type of cable for Atlantic telegraphy. II Stated in a complete mathematical form in Part III. ^ Signs of this fact being appreciated occurred previously, when .Mr (afterwards Sir Charles) Hright, on becoming engineer to the Atlantic Telegraph Company in 1857, immediately recommended a much heavier core— 392 lbs. copper to the same weight of gutta-percha— than had been arranged for the first Atlantic cable. It was, however, for financial and technical reasons, found impossible to efiect the change. 82 SUIiMARINK TKLEf.KAI'HS. Co,),* and adopted by the Scientific Committee for the new cable,t was to consist of a strand of seven copper wires, each of No. 1., for purposes of durability -such a type is ccmsidered nowadays most undesirable. .Any preservation of the iron wires by the hemp laid up round each is at the best of very short duration, even when the latter has been saturated with a tar compound. The real strength for repairs is in the iron wires, and the hemp serving seldom lasts long enough to save these appreciably. Moreover, much trouble is frecjuently exjierienced with this type owing to any given wire breaking away and getting jammed into the core, an event which can scarcely happen with an ordinary close-sheathed cable, having a more or less complete arch, or tube, of wires. The cable above described is often aptly referred to as the " open-jawed " type, being a ready prey to the teredo — e/ hoc i^ciitis omite — which can the more readily burrow into it, and, in so doing, damage the core. Again, having a low specific gravity, and offering a great deal of friction (both on account of its large circumference and rough surface), though comparatively easy to lay in some fashion without mishap, it is liable not to sink properly into all the irregularities, and, in fact, to be paid out with too little slack. .Similarly — owing to skin friction and resistance— a cable with an e.vterior of these dimensions and character is undesirable for purposes of recovery. OKVKLOI'MENTS. with reference to the Malta-Alexandria cable — the first to be so tested. The (letirec of pressure adopted was the same in this instance, i.e.y equivalent to 640 lbs. per square inch, this being the limit of pressure which was considered at that time necessary or desirable as the nearest safe approximation to the pressure to be experienced by the cable on sub- mersion. Such a i)rcssure was, of cour \ a very long way from that which this cable subseciucntly had to contend with, though pcrhai^s sufficiently representative in the ca.se of the previous cables to which this .sj-stcm had been applicii.* The sheathing was uiidcr- taUen at the Telegraph Con- struction Company's Works at Morden Wharf, Greenwich, under the personal direction and superintendence of Mr (aftcr- wartls Sir Richard Atwood) Glass. The reels of core were kept under water, in locked receptacle.s, until required, and the cable when finished was coiled into light iron tanks. These tanks were kept con- stantly filled with water, and the cable tested daily, both by the contractors and by the "Atlantic" Compan\''s electrician, Mr C. F. Varley. The " Great Eastern," an enormous vessel of 22,500 tons burden.f which Kio. j6.— Shore End of the 1865 .Allamic Cable. * Nowadays a pressure of this amount would be considered utterly inadec|uate. Wliere any such test is applied at all, a degree of pressure is used which is fully eciuiva- lent to that at the bottom of the ocean where the cable is to be laid. Messrs .Siemens Brothers are the only contractors who adopt this jilan. At their factory verv elaborate apparatus is used, and this is referred to in Part II. As the result of experience, other authornies consider that the pressure test system, whilst distinctly costly, is as liable to temporarily seal up anil screen small faults of manufacture as to bring them to light. t On account of her dimensions, originally christened the " Leviathan," and the conception of that distinguished engineer, Isambard Kingdom Brunei, F.R .S. (sec p 79) This vessel (built by the late Mr .Scott Kussell) was but a bit before her time. In the present day, with improved engines, she could be usefully and profitably employed, had she not been broken up. At the time referred to above, she could not get a suitable cargo, and laymg the Atlantic cable was the first piece of work she did which was at all worthy of her, after lying more or less idle for nearly ten years. Mr Brunei drew attention to her as being the only vessel that could do the work. This was a few years after the "Eastern Ste.mi Navigation Company' had failed over her, and a new company formed by Mr Gooch (afterwards Sir Daniel Gooch, Bart., M.I'.;, under the title of the Great Ship Company," subsequently (in 1864) converted into the "(ireat 86 SUHMARINK TELECKAl'IlS. had been Ij'ing up idle for sonic j-ears, was secured for the work, she being the only ship that could take the entire length of cable. As it was not practicable to moor her off the works at East Greenwich, the cable had to be cut into lengtlis and coiled on two pontoons, and thence transferred to the big ship (see Fig. 37 opposite, and also Fig. 48, p. 108).* It was coiled into three large water-tight iron tanks built up in the hold of the vessel. The main tank measured 75 feet across; the after tank, 58 feet; and the fore tank, 52 feet. The cable machinerj' was fitted to the " Great Eastern " under the guidance of Mr Henry Clifford (to the design of Messrs Canning and Clif- !3SS^<^^?MBi ^4^4 -^tmi .-^BW^^^^^--* • -^^".l^^^^^^^^^^^^^l ^^^^^^Ktfm^" I'li;. j8. — i'a)in;^-Oiil Machine, Atlantic Cables, 1865-66. ford), assisted by Mr S. Griffith. Mr Appold's type of brake formed a part of the paying-out apparatus — in fact the general character of the gear (Fig. 38) did not differ largely from that adopted in the second (1858) expedition of the " Agameinnon " and ''Niagara." The main point of difference was the further ap])lication of "jockeys"! (Fig. 39)— of a much more corn- Eastern Steamship Company." .As the chairman of tlie latter company, Mr (ilooch was an active spirit in arran^inji for the charter of tiie " Great Eastern " over this work. In this way he became an ardent supporter of the enterprise, and occupied a seat on the board of the Tclejjiaph Construction Company -assuming,' tlie chair later on — up to the time of his lamented deatli in 1889. * Taken from tiic original drauin^fs of Mr .S. Oriffith on Iichalf of the Telegraph Construction Company. t So-called because they ride on the cable. _.,.::_.,„ „ ., .' _ [Plate VI. § ^ -I--I- \,Tofa(cp. 86. DEVELOPMENTS. 87 plete form — ^to the " Great Eastern " gear, which was entirely constructed and set up by that famous firm of engineers, Messrs Penn, of Greenwich.* The cable, in coming up from the tank in the hold of the vessel, passed along a conducting trough to the first of the six leading V-wheels of the machine (Fig. 39). It did not take a turn round this wheel is, but merely passed over the top of it and the five, other wheels consecutively, being pressed down into their grooved rims by a small weighted roller or jockey pulley A, around the circumference of which there was a band of india-rubber so as to produce a reiarding effect upon the cable when necessary. Each of the wheels over which the cable passed had a light brake fitted, so as to introduce a slight retardation for giving the cable a straightened lead to the drum. For the sake of clearness this brake is not shewn in the figure. The "jockey" turned upon an axle at the end of ar. arm centred at a, and the weights of the "jockeys" could be released at once by turning a hand- wheel. After leaving the last of these pulleys, the cable /^^_/!]j^ took several turns round a large drum, the axle of which was connected to a brake arrangement similar to that of 1858, by means of which the speed of the drum with a given strain was checked or accelerated, according to !•■■'=• 39.-Diacra„, of One of 0,e Six Le^^^^ ' " of the 1865-66 Allantic Cable Machinery. the increase or reduction of a series of hand-weights, that could be attached or taken off as required. The cable was then led through the dynamometer s)-stem and hence outboard. As may be seen in 1^'ig. 37 (and still better in Fig. 42 further on), there was a second brake drum in tandem with the former, but this was onl>' intended as a reserve in case of accident. The shore-end cable was manufactured by Mr W. T. Henley, of North Woolwich, it was some 30 miles in length, of which 26 N.M. were put on board S.S. "Caroline," fitted up for the purpose. This part was laid by her (.see illu.stration on next page) from Foilhommerum Bay, Valentia I-sland, on the 22nd of July 1865.! a,' * The late Mr John Penn used also to act as referee in the aflfairs of the Telegraph Construction Company. t The cable was landed here at the lower end of the island, and about six miles from Knitjhtstown, instead of at Ballycarberry Strand, where the previous (1858) cable had been landed, partly because it was the more direct point, and partly to avoid the line of the old cable. It was, however, afterwards found to be more exposed, and to involve a 88 SUH.MARIXE TKLKCJRAl'US. The next day the "Great Eastern," under the command of Captain (afterwards Sir James) Anderson,* with a total dead weight of 21,000 tons, joined up her cable to the shore end, and started paying out towards America, at a speed of six knots. She was escorted by two British men- of-war, the "Terrible" (Captain Napier) and the "Sphinx" (Captain Hamilton). On behalf of the contractors, the Telegraph Construction and Mainte- nance Company, Mr (now Sir Samuel) Canning was the engineer in charge of the expedition, with Mr Henry Clifford as his chief assistant.f Both Atlantic Cable of 1865. I.andlnf; tlio .SIkiic Eiul in lio:\ts fnmi S.S. " Caroline,'' off Foilhomnieruni Bay, \'alenlia Island. these gentlemen had been engaged with Sir Charles Bright on the first Atlantic expedition, and had had much experience alike in cable work rough bottom, besides the disadvantage of it not being on the mainland. This spot has therefore since been given up as a landing-place for Atlantic cables. Nowadays they are invariably taken direct to the mainland, so as to avoid dependence on a branch cable. * Mr R. C. Halpin being ilie chief officer, iioth these gentlemen had the reputa- tion of possessing great skill in the handling of a ship. Captain Anderson was at the time captain in the Cunard Steamship Coinpany's service, by whose permission, there- fore, he accompanied the expedition. + Since the first Atlantic expedition Messrs Glass, Elliot, and Co. had gathered together a full and ])ermanent staff of engineers and electricians (of which Mr Canning became the chief and Mr Clifford the second engineer) in such a way as enabled them to undertake direct contracts for laying — as well as manufacturing — submarine telegraph cables. When this firm, in 1864, merged itself into the Telegraph Construction Com- pany (as already described), position in the above respect was still further established. DKVKLOPMENTS. 89 and mechanical engineering. There were also on the engineering staff of the contractors, Mr John Temple and Mr Robert London. Mr C. V. de Sauty acted for them as chief electrician, assisted by Mr H. A. C. Saunders, and .several others. Mr Willoughby Smith, the electrician to the Gutta-percha Company,* was also out on the expedition at the request of the contractors, though holding no exact official position. By arrangement with the Admiralty, Staff-Commander H. A. Moriarty, R.N., acted as the navigator of the expedition. This officer was well known to be possessed of great skill in this direction, and had previously served in a like position on the first Atlantic cable expedition, when his services were similarly lent by the Admiralty. The Atlantic Telegraph Company was represented on board by Professor William Thomson (now Lord Kelvin), LL.D., F.R.S., and Mr C. F. Varley, as electricians, the former acting mainly as .scientific expert in a consultative .sense. Both Mr Field and Mr Gooch accompanied the expedition, the former as the chief promoter of the enterprise, and the latter on behalf of the " Great Fastern " Company. Representing the Press, there were also on board Dr W. H. Rus.sell, the well-known journalist, of The Times, acting as the historian of the enterpri.se; f and Mr Robert Dudley, a famous artist, who produced several excellent pictures of the work in its different stages, as well as articles for the Illustrated London News, and for Ur Russell's book, " The Atlantic Telegrajjh," now very scarce. * Unfortunately trouble soon arose. The first fault declared itself on the 24th, when 84 miles had been paid out. It was decided to pick up back to tlie fault, which was found after loA miles of cable had been brought on board. A piece of iron wire was found to have pierced the cable diametrically, so as to make contact between the .sea and the con- * Commercially speaking, incorporated with the newly-formed Telegraph Construction Company ; Mr John Chatterton then becoming manager of the Ciuita-percha Company's works in succession to the late Mr Samuel Statham, who had just died. + This famous war correspondent, author, and general nc\vspa])er writer, has since h?r- aie .Sir William Howard Russell, LL.U. \ Detailed and stirring accounts of the events of this expedition also appeared suhse- ([uently in lUnckivood's Miii^nsiih; in Corn/it'tt, antl in Macmil/uns. The former was written by Mr Henry O'Neil, .^.R.A., and the latter by Mr John C. Deane, both of whom were eye-witnesses aboard the " Grtiit Eastern." Mr O'Neil also brought out an illus- trated comic journal during this and the following expedition, issued at periodic intervals, which was a source of much amusement to those who had time for perusing it. Still more was an " cxtiavaganza " - written by Nicholas Woods and J. C. Parkinson — on the subject. |)crformed on board on the completion of all the work in 1866. lloth these were afterwards published in booklet form, and are much treasured by the parties caricatured therein. 90 SUIiMAKINi: TKLKGRAPHS. ductor. The faulty portion Weis cut out, and the paying out resumed as soon as the cable was spliced up again. On 29th Jul)-, when 716 miles had been laid, another and more serious fault appeared. The arduous opera- tion of picking up again commenced, and after nine hours' work the fault was safe inboard, and the necessary repair effected. On stripping the cable another jiiece of iron wire was discovered, sticking riglit through the core. Anxiet}' and misgi\ings were now felt hy ;i\\ on board, for it seemed that such reverses could onlj- be attributed to malevolence. On the 2nd of August a further fault was reported ; they were now two-thirds of the way across, 1,186 miles of cable being already laid. Again they had to pick up, and this time in a depth of 2,000 fathoms. One mile only had been recovered, when an accident of some kind happened to the picking-up machiner\'.* The great ship, having stopped, was at the mercy of the wind and swell, and heavy strains were brought on the cable, which consequently suffered badl}- in two places. Before the two injured portions could be secured on board, the cable parted and sank. Mr Canning at once decided to endeavour to recover the cable, notwithstanding the fact that it lay in 2,000 fathoms. An iron grajjnel was lowered by means of a wire rope which had been brought in case a mark buo)' had to be put down, or the cable had to be cut, owing to some unforeseen accident, and temporarilj- buoj'ed.f This rope was in lengths of 100 fathoms, and measured in all about 5,000 fathoms. The vessel then proceeded to make a scries of short runs crossing and recrossing the suppo.sed line of cable. After mana;uvring in this way for about fifteen hours, picking up was started on the supposition of the cable having been hooked by the grapnel ; 700 fathoms of rope had been hove in, when one of the connecting links gave way, and all beyond it sank to the bottom. The work was recommenced with hempen ropes, two miles further west, in a depth of 2,300 fathoms, and on the 8th of August the cable was again hooked ; but when raised to within 1,500 fathoms of the surface another connecting link parted, the strain being about nine tons. Two more attempts were made. The first time the grapnel fouled the rope, and had to be hove up again ; the second time the ro{x; parted close to the capstan when thcj- had picked up 765 fathoms with a gradually increasing strain. The store of grappling rope being now quite exhausted, the work had to be given up, and on nth August 1865 the fleet of .ships parted company — shattered in hopes as well as in ropes. * This constantly failed for want of sufficient strength and an adequate supply of steam. t But with no special idea at the time of recovery work in such deep water. DEVELOl'MENTS. 91 Second and Successful Attempt, 1866. The results of tlie last expedition, disastrous as they were from a financial point of view, in no wise abated the courage of the promoters of the enterprise, but onlj- served to increase their energy by demonstrating the probability, if not the certainty, of an early and complete success. During the heaviest weather the " Great Eastern " had shewn exceptional " stiffness," whilst her great size and her mancjeuvring power (afforded by the screw and paddles combined) seemed to shew her to be the very type of vessel for this kind of work. The picking-up gear, it was true, had proved insufficient,* but with the paying-out machinery no serious fault was to be found. The feasibility of grappling in mid-Atlantic had been demon- strated, and they had gone far towards proving the possibilitj' of recovering the cable from similar depths.f Last, but b\' no means least, it was proved that the low temperature and enormous pressure at ocean depths greatly increases the insulating power of gutta-percha, whilst the conductivit)- of the copper was substantiall)' increased by the low temperature, but apparently unaffected by the pressure. To overcome financial difficulties, the Atlantic Telegraph Company was, practically speaking, amalgamated with a new concern, the Anc.lO- American Telec;rai'I1 Co.MrANV, which was formed, mainly by those interested in the old business, with the object of raising fresh capital for the new and double ventures of iiS66. The ultimate cai)ital of this company amounted (as before) to ;^6oo,ooo. I * Tills was specially pointed to by the rejjresentatives of the "Atlantic" Company when considering the canyinj,' out of the agreement by the contractors. + It may be mentioned in passing also that Professor \V. Thomson had in the interval delivered an address before the Royal Society of Edinburgh on " The Forces concerned in the Laying and Lifting of Deep .Sea Cables" (see Frdc. Roy. Spc, December 1865). He had previously contributed an article to 7"//<' F.iii^ineer relative to the catenary tonncd by a submarine cable between the ship and the bottom, during submergence — under the influence of gravity, fluid friction, and pressure. In this communication Pro- fessor Thomson pointed out that the curve becomes a straight line in the case of no tension at the bottom — the normal condition, in fact, when paying out. X In raising this, Mr Field first secured the support of Mr (afterwards Sir Daniel) ('■ooch, C.E., M. P., then ch.iirman, and previously locomotive superintendent, of the Clreat Western Railway Company, who, after what he had seen on the previous expedition, promised, if necessary, to subscribe as much as ^20,000. On the same conditions, Mr Hrassey expressed his willingness to bear one-tenth of the total cost of the undertaking. Ultimately, the Telegraph Construction Company led off with /ioo,ooo, this amount being followed by the signatures of ten directors (as guarantors) at /io,ooo a-jiiece, viz. ;— Henry Ford Barclay, Henry Ilewley, Thomas lirasscy, A. H. Campbell, George Elliot, Cyrus \V. Field, Richard .\twood (Jlass, Daniel (iooch, John Pender, and John Smith. Then there were four subscriptions of ^^5,000, and some of ^2,500 to ^1,000, principally from firms participating in one shape or another in the sub-contracts. These 92 SUHMAkINK TKLKC.RAI'HS. It was now proposed not onlj' to lay a new cable between Ireland and Newfoundland, but also to repair and complete the one lyin^ at the bottom of the sea. A length of 1.600 miles of cable was ordered from the Tele- {^raph Construction and Maintenance Company. Thus, with ihe unex- pended cable from the last expedition, the total length available when the expedition started would be 2,730 miles, of which i,|)6o miles were allotted to the new cable, and 697 to complete the old one, leaving 113 miles as a reserve. The slack, or difference between the total length of cable paid out and the distance overground covered by the ship, having been only 8 per cent, on the jjrevious expedition, the length now provided a]jpcared to be sufficient. The core of the new cable was j^recisely similar to that of the old one of the j'ear before, but the testing of the core under pressure was abandoned, finding that tliis practice, in several instances, instead of revealing the weak places, had a tendency .sometimes to conceal tlicni. The sheathing wires 1m(;. 40.--Allanlic Cable (1866). in this cable were galvani.sed (besides being of softer iron to start with), and again separatelj' covered with five strands of Manilla j'arn, which in this case were left imtarred.* The cable (Fig. 40) weighed i ton II cwt. per N.M. in air,+ and 14^ cwt. in water. Its total diameter was sums were all subscribed before even the prospectus was issued, or the books opened to the public. The remaining capital then quickly followed. The Telegraph Construction Company, in undertakinjr the entire work, were to receive ^500,000 for the new cable in any case, and if it succeeded an extra ;{^ 100,000. If both cables came into successful operation the total amount payable to them was to be £737, \4o. * The tar compound which had been used for the Manilla yarn outside the wires had given much trouble in the handling of the previous cable during coiling and laying operations. It was, in fact, the occasion of several exciting scenes, from the layers of cable in the tanks sticking together and becoming entangled, thus causing " foul flakes," as they are termed. It would have been better, probably, if the compound had been changed instead of being abolished altogether, both on account of its tendency to make the finished cable less " lively," and owing to its preservative character. Some considered, however, that a tar compound tended to have an injurious effect on Manilla and all hemp yarns, and to screen faults of insulation. + That is to say, nearly 5 cwt. less than the previous line, which was considered an advantage, its specific gravity being correspondingly lower. DKVELOI'MENTS. 93 I.I inch, ami its brcakiiiK^ strain S tons 2 cut., being thus a Httlc higher than that of the previous cable, due, no doubt, to the general improvements in manufacture as regards the iron wire and the class of hemi) used. The iron wire, besides being stronger, was also less hard and brittle— in fact more pliable. The shore-end cable (Fig. 41) determined on in this ca.se was of an entirely different description.* It had only one sheathing, consisting of twelve contiguous iron wires of great indiviflual surface and weight ; and outside all a covering of tarred hemi) and comijound. The part of this cable which was intended for .shallow depths was made in three different t)pes. Starting from the coast of Ireland, 8 miles of the heaviest was to be laid, then 8 miles of the intermediate, and lastly 14 miles of the lightest t)-i)e, making 30 miles of shoal- water cable on the Irish side, {"'ixe miles of shallow -water cable, of the different types named, were considered suffi- cient on the Newfoundland coast. The jjrcxious pa\ing-(iut machineryon board the "Great I'^astern " was altered to some extent by Messrs Penn to the instructionsof Messrs Canning andClifford. Itagainconsisted of six vertical sheaves placed in a line one after the other, each supporting a jockey puUe)' with bevelled edges, narrow enough to fit between the flanges of the sheaves below. The bearings in which the spindles of the jockey pulleys revolved were mounted on frame levers pivoted at one end, so that the pressure of the jockeys riding on the V-sheaves, and on the cable passing between, could be regulated by weights attached to the opposite extremities of the lever arms. A small straj) brake, worked by hand, was fitted round the shaft of each V-vvheel. The cable on leaving the tank (l""ig. 42) led in a straight line through the free space between the V-wheels G, and their riding jockeys, and then over a roller to a large drum P, six feet in diameter, round k;. 41. re ICnd,l866. * The Electric Telegraph Company had found over the Anglo-Dutch cable that a stranded sheathing was less durable than the previously used solid wires as above. 94 SUHMAKINE TKLKCRAniS. which it tdok four turns,* thciicc, tliroiit^h ^Hii(h'ii^ rollers, uiuIlt the dyiiamo- inotcr pulley D, ami finally over the stern sheave A, into the sea. Two Al)i)olcl brakes, working in trou^Mis filled with water, were fitted on the shafts of both drums, similar to those controlling the V-sheaves ; and, to avoid heating, water was ke|)t |)ouring on the cable whilst passing ini- that the jwying-out machinery could be used to pick up cable during the laying if necessary,* and thus avoid the risk incurred by changing the cable from the stern to the bows. This addition Km. 42. — CctiLTal .Xrranfjcment of r.iyinfj-oiit Machinery at Stern of "(Iroat Kastern " (lS66). of Penn "trunk" engines — as well as the general strengthening of the entire machinery — was made in accordance with the designs of Mr Henry Clifford. The picking-up machinery forward (Figs. 43, 44), after the previous expedition, was considerably strengthened and improved with spur * The duplicate ilrum and brakes p' were merely an auxiliary foi emergencies- /.('., in the event of the others being disabled, or for hauling back. Upon the overhanging ends of the drum shafts driving pulleys were tilted, which could be connected by a leather belt for the purpose of bringing into use the duplicate brakes, if the working brakes should get out of order. t I'he general similarity between the paying-out gear aboard the "Oreat Eastern" and that fitted to H.M.S. "Agamemnon" and U.S.N.S. "Niagara," is referred to in the complete account of the 1866 machinery given by Mr Elliot (afterwards Sir (ieorge Elliot, Hart., M.l'.) in tl.c course of a paper on the subject read before the Institution of Mechanical Engineers the following year. See /'roitwfi/ij^s Inst. M.E. This gentleman was a partner in the firm of Messrs Glass, Elliot, and Co., and afterwards director of the Telegraph Construction Company, ultimately becoming chairman and remaining so up to the time of his death in 1893. \ It is a little remarkable that no steam gear had been applied to the paying-out apparatus of 1865 for this purpose, seeing that the corresponding machinery of 1858 was so furnished. Ll'l.ATK Vil, Kic. 43. — rian and IMivalicm of l'ickin(j-up Machine alxiard S.S. "(!reat Eastern," as used for lecoverinj" tlie 1S65 Atlanlir Calile. I'u;. 44. — (Jeneral \ie\v of I'lcking-u]) Machine aljoaid " Clreal Eastern," 1S66. \_Tofa(f p. 94. DEVKI.OI'MKNTS. 95 wheels aiul pinion ^reariii^f. It had Uvo drums 5 feet 7 inches in diameter, worked by a similar pair of 70 horse-power trunl< en},'ines. This formed an cxceedinjrij- jjowerful maclune, and much credit is (hic to those who devised and constructed it. Similar ^ear was fitted up on board the two vessels — S.S. " Medway " and S.S. " Albany "—chartered to assist the "Great ICastcrn." For the purpose of grappling the 1865 cable, _o miles of rope were manufactured, which was constituted by forty nine iron wires of No. 14 ^auge, separately covered with Manilla hemj). Six wires so served were Kic. 45.— Buoys, etc., used on Atlantic Expeditions of 1865-66. laid up strand-wise round a seventh, which formed the heart or core of the rope. The breaking strain of this rope was about 30 tons.* In addition, five miles of buoy rope were provided, besides buoys of different shapes and sizes, the largest of which (see Fig. 45) would support 20 tons. As on the previous expedition, several kinds of grapnels were put on board, some of the ordinary sort, and some with springs * The comparatively short length (six or seven miles) of grappling rope provided for the expedition of the previous year was said to possess a corresponding breaking strain of only 8J tons— being, in reality, buoy rope, though used also for grappling. 96 SUBMARINK TKLECiRAl'IIS. to prevent the cable surgintj, and thus escaping whilst the grajjnel was still tlraggingon the bottom (Fig. 46) ; others, again, were fashioned like pincers, to hold (or jamb) the cable when raised to a required height,* or else to cut it only, and so take off a large proportion of the strain previous to picking up.f The propelling machinery of the "Great Eastern" had similarly received alteration and improvement in the intervals of the two expeditions. The paddle wheels were reduced in diameter (.six knots being the maximum speed required J), and made to work indeijendcntly, to enable the ship to turn rapidly without headway. The screw propeller was surrounded with an iron cage, to keep the cable and ropes from fouling it, as had been provided by Sir Charles Bright for the "Agamemnon" and "Niagara" in 1857. The testing arrangements were perfected by Mr Willoughby Smith, in such a way that insulation readings could be continuously taken, even whilst measuring the copper resistance, or while exchanging Fig. 46.— TypL> .if Grapnel signals with Valentia.§ Thus there was no longer mainlv used for Recovery , r r < \ ■ ■ i i i • i of ihe'iS65 Atlantic Cable ^ny danger of a fault bemg paid overboard without iliirini; Kxpeditionof 1S66: instant detection. On the 30th June 1866, the "Great Eastern," from the Thames, followed by the "Medway" and " Albany," arrived at Valentia, where H.M.SS. "Terrible" and "Racoon" were found, under orders to accompany the expedition. The "Medway" the Cable is shewn hooked on one pronj;. * Most of this apparatus was furnished by Messrs Brown, Leno.\, and Co., the famous chain, cable, anchor, and buoy engineers, several of tlie gra|)ncls being to their design, as well as the "connections.'' + This was a grapnel with a cutting edge in the bed between the flukes, or prongs, and the shank, whicli tended to cut through tlie cable under a gixen raising strain rather sooner tlian would be the case by ordinary methods of breaking. This, however, was not a cutting grajjuel, as at present understood, for cutting the cable at the bottom Mr Latimer Clark had just devised an alternative holding or cutting grapnel (:he two operations being also combined, if desired), but this was not adopted for the expedition. It was the first attempt in the above direction, and was of a somewhat elaborate character, modified subsecpiently by the late Mr Frank Lambert. J This limitation of the ship's speed was matle a special point of on this occasion, partly to provide for the ship being brought to a standstill quickly in the case of mishap during paying-out operations, and also to ensure the cable being laid in such a way that it |)roperly acconunodated itself to the irregularities of the bottom. The ordinary speed ultimately adhered to was five knots for the ship and six knots for the cable. S Professor Thomson's reflecting apparatus, for testing or signalling, had been con- siderably improved since the previous .Xtlantic cable of 1858. Again, this was the first cable expedition on which the above, now famous, ship and shore system of combined DKVKLOr.MENTS. 97 had on board 45 miles of deep-sea cable in addition to the American shore end. The ])rincipal members of the staff actin^^ on behalf of the contractors in this expedition were the same as in that of the previous year, Mr Cannin^r bciu'^ again in charge, with Mr Clifford and Mr Temple as his chief assistants. In the electrical department, however, the Telegraph Construction Company had since secured the services of Mr VVilloughby Smith as their chief electrician, whilst he still acted in that capacity for the Gutta-percha Company. Mr Smith, therefore, accompanied the expedition as chief electrician to the contractors, his chief assistant being Mr J. May. Captain James Anderson and Staff-Commander H. A. Moriarty, R.N., were once more to be seen on board the great ship, the tormer as her captain, and the latter as navigating officer. Professor Thomson was on board as consulting electrical adviser to the Atlantic Telegraph Com])any, whilst Mr C. F. Varley was ashore at Valcntia as their electrician. Mr Latimer Clark was also at Valentia, representing Messrs Bright and Clark as consulting engineers to the Anglo- American Telegraph Company,* Mr J. C. Laws and Mr Richard Collettf being respective!)- aboard and ashore at the Newfoundland end representing the same firm. Mr Glass was ashore at Valentia for the purpose of giving any instructions to his (the contractor's) staff on board, whilst Mr Gooch and Mr Field were on board the " Great Eastern " as onlookers, and as watchers of their individual interests. * On the 7th July, the "William Cory" landed the shore end in Foilhommerum Bay, and afterwards laid out 27 miles of the intermediate testing and signalling was put into practice. Both Mr Cromwell \'ariey and Professor Thomson are said to have devised similar methods to that of Mr Willoughby .Smith. On this occasion, also, condensers were apphed by Mr NV. Smith to the receiving end of the cable, having the eftcct of very materially increasing — indeed, sometimes almost doubling — the working speed. Though Mr Smith was the first lo do this in a practical way, it transpired afterwards that Mr Varley had taken out a patent in 1862 embodying such a principle for working long cables. Mr Varley was a man of many patents. * Sir Charles Hiight, M.P., was engaged elsewhere at the time of the expedition. + At a later period, after both the 1865 and 1866 cables were in working order, Mr Collett actually sent a message from Newfoundland to X'alentia with a battery composed of a copper percussion cap, and a small strip of zinc, which were e.xcited by a drop of iicidulatcd water - the bulk of a tear only ! This was during some experiments carried out by Dr (iould on behalf of the Astronomer- Royal (in concert with the Magnetic Telegraph Company), between (Ireenw-ch and Newfoundland, via the Atlantic cables, for the verification of longitudes in the United .States. \ There was also on board Mr J. C. Ueane, the secretary of the Anglo-American Telegraph Company, whose diary proved of much use to IJic limes and other newspapers in the absence of Dr Russell, who had so vividly and thrillingly described the events of the previous expedition. 98 SUBMARINE TKl.KdRAl'IIS. cable. On the I3tli, the "Great Eastern" took the end on board, and, havin<^ spHccd on to the remaining; three miles of similar cable coiled on the top of the deep-sea section, started payin;^ out. The track followed was parallel to that followed the year before, but about 27 miles furtlier north. There were two instances of fouls in the tank, due to broken wires catching' neiL:jhbourin^ turns and flakes, and thus clrawincj up a whole bundle of cable quite close (formint; an ajjparently inextricable mass of kinks and twists) to the brake drum. In each ca.se the ship was promptly got to a standstill, and all hands set to unravelling the tangle. With a certain amount of luck, therefore, coupled with much care, neither accidents ended fatally ; and, after straii^htenint;- out the wire as far as possible, paying out was resumed. Fourteen days after starting, the " Great Eastern " arrived (sec below) off Heart's Content,* Trinit)' Bciy, where the "Medway" joined (U and landed the .shcjre end partl\- b\- boats, thus bringing to a successful conclusion this jiart of the expedition. The total length of cable laid was 1,852 N.M., average depth 1,400 fathoms. After much rejoicings+ during the coaling of the " (ireat luistern,"^ the Telegra])h Fleet once more set out to .sea. * This is situated on tliu opposite side of Trinity l>:iy to Hull Arm, where the 1858 cable had been landed, and not so far up. It was supposed to be even move protected than lUill .Arm, from which it is some 18 miles. t These were at first somewhat dampened by the fact that the cable between New- foundland and Cape Hreton (Nova Scotia) still remained interrupted, and that conse- (juently the entire telegraphic system was not e\en now complete. However, in the course of a few days this line was repaired, and New ^'ork and the rest of the I'nited States and Canada put into telcgra])hic communication with Europe. I Six steamers, laden with coal, had set out from Cardiff some weeks in advance to feed the " C".reat Eastern " on her arrival on the other side of the Atlantic. {/•'fviit tht: raintint^ hy Ilenty Cliffon '. S.S. " Great Easlern " approaching Heart's Content, Trinity Bay, in Comiiloting die Laying of the 1866 AUamic Ciible. dkmcuji'.mknts. 99 Recovery and Comtletion of 1865 Cahle. It now remained to find the end of the cable lost on the 2nd August 1865, situated about 604 miles from Newfoundland, to pick it up, splice on to the cable remaining on board, and finish the work so unfortunately inter- rupted the year before. The difficulties to be overcome can be readily imagined, the cable lyin^j; 2,000 fathoms deep without mark of any kind to indicate its |)osition. The buoys put down after the accident had lonj; since disappeared, either their moorings having dragged during various gales of wind, or the wire ropes which held them having chafed through, owing to incessant rise and fall at the bottom. The position of the lost end had to be determined by astronomical observations, which necessitate clear weather, and can then only give appro.ximate results, unless frequently repeated, on account of the variable ocean currents, which sometimes flow at the rate of three knots — /.c, three nautical miles per hour. Moreover, for grappling and raising the cable to the bows, the sea must be tolerably smooth, and in that part where the work lay a succession of fine days is rare, even in the month of August. H(n\ever, they still had on board Captain Moriarty, one of the ablest navigators in the world. .Added to this, the greater portion of the cable in deep water had been paid out with ab(jut 1 5 per cent, slack. The chiefs of the expedition, fully confident of success, hastened their preparations, and on the 9th of August 1866 the " Great Eastern " again put to sea, accompanied by S.S. " Med way." On the 12th, the vessels arrived on the scene of action, and joined company with H.M.S. "Terrible" (Cai)tain Commerell*) and S..S. " Alban)-," these vessels having left Heart's Content Bay a week in advance to buoy the line of the 1865 cable and commence grappling. Mr Canning's plan was to drag for the cable near the end with all three ships at once. The cable, when raised to a certain height, was to be cut by the " Medway," stationed to the westward of the " Great Eastern," .so as to enable the latter vessel to lift the Valentia end on board.f When the " Great Eastern " arrived on the grappling ground, the "Albany" (with Mr Temple in engineering charge) had already hooked * Now .Admiral of the Fleet .Sir J. E. Commerell, V'.C, Ci.C.H. + This iieiiiR, of course, before the ilays of cutting and holding grapnels as we now have them. These render it possible for a single ship to effect repairs, even where it is out of the question to recover the cable in one bight. .Mr Claude Johnson, Mi F. R. Lucas, Mr W. F. King, F.R.S.E., Mr H. Benest, and Professor Andrew Jamieson, F.R.S.E., have— amongst others— devised special grapnels of this character. lOO SUIiMARINK TICLKCKAl'HS. and buo}-cd the cable ; but the biun- cliaiii havinij been carried a\\a\-, they not only lost the cable, but 2,000 fathoms of wire ro|)e besides. On the 13th of August, the " Great Eastern " made her first drag, about 15 miles from the end; and, after sexeral \ain attemjits, the cable was final!}' hooked and lifted about 1,300 fathoms, Diu'ing the operation of buoj'ing the grappling rope, a mistake occurred which resulted in the rope slipping overboard and going to the bottom. The " Great luistern " now proceeded six miles to the eastward, and commenced a new drag, for raking tlie ocean bed with 2,400 fathoms of wire ro]je. About eleven o'clock at night the grapnel came to the surface with the cable caught on two of the prongs. The cable thus successful!)' brought up was parti-coloured like a snake — half a niudd\' white with the ooze of microscopic .shells on which it had rested, and half as black and shin\' as when it left the factor)' — affording positive proof that hereabouts, at all events, the coni|)osition of the bottom was such that the cable had not sunk entire!)- into it. J-^oats were quick!)' in position alongside tlie grapnel. Shortl)' afterwards the)- were endeavouring to .secure the cable to the strong wire rope, by means of a nii)per, when the grapnel canted, allowing it to slip away from the prongs — like a great eel — and disappear into the sea. On the 19th, the cable was once more hooked, and rai.sed about a mile from the bottom, but the sea was too rough for buo)'ing it. During the following week all three vessels dragged for the cable at different points, according to the plan previous!)' arranged, but tlie weather was unfavourable, and the cable was not hooked, or, if hooked, had managed to slip awa)- from the grapnels. The ship's compan\' about this time became discouraged — in fact, more and more convinced of the futility of their efforts. On the 27th, the " .\lban)-" signalled* that the)- had got the cable on board with a strain of on!)- tlnee tons, and had buoyed the end ; but it was soon discovered that her buo\' was 13 miles from the track of the cable, and that she had recovered a length of three miles which had been purposely paid overboard a few days before. Shifting ground to the eastward about 15 miles, the vessels were now working in a depth of 2,500 fathoms. As the store of grappling rope was dimim"shing day by day, and the fine .season rapidly coming to an end, Mr Canning decided to proceed at ■* During this expedition niucli use was made of the invaluable system of day and nigiit visual telegraphy introduced to the \a\y l)y Captain Colomb, R.X., and already referred to with regard to the Persian tjulf cable, during the laying of which it was first employed in connection with cable expeditions. ■A ■A ■J: ■■r. — o w -J a I -2 o o DEVELOPMENTS, lOI once langer, of Paris, and Julius Reuter, of London. S Afterwards, in 1873, merged, with its cable, into the .Anglo-.Anierican Telegraph Company and its system. I! This forms the greatest length of cable which has ever been laid in one continuous length up to the present time. The length of the section is now, after various repairs, 2,717 N.M. i lOS SUKMARINE TELEGRAPHS. mistake ; altliou;4h at that time it was considered by many to be the be.it possible for deep water, not only with view to the process of laj'iny it, but also to its durability and the facility of its rcco\er}'.* Another long and important length of cable manufactured and laid by the Telcgrajjh Construction Company, from S.S. " Great Eastern," in the same year (1869), was a direct line for the Bkitisu-Ixdian SuisMAKINE Telec.uaph Company + between Egypt (Suez) and India (Bombay). I'his passed, of course, down the Red Sea, touching at Aden, and then crossing ti:c Arabian Sea.* The armour in the above cable was composed of the same iron and hemp combination which was adopted for the 1S65 and 1866 Atlantic lines, as well as for that of 1869, etc. In this instance, however, a hempen whipping was tightly ajjplied round the completed cable with a lay equiva- lent to about :,' inch between each turn, so as to prevent any broken wires becoming disengaged. § I*"ollowing this came the extensions carried out by the same firm (Tele- graph Construction and Maintenance Company) on behalf of the JU-ilTIsil- INDIAN E.KTENSION and ClIINA SUH.MARINE TELEGRAPH COMPANIES respectively, in which .Sir C. Bright acted as engineer for the companies ; also, in 1872, a cable from India (Madras) to Australia, for the BklTIsil- AUSTRALLVN TELEGRAPH COMPANY, via the .Straits Settlements. * This cable, which has been " down " -electrically speakin;,' -for some years, has proved a costly line in repairs. One expedition alone is said to have run into as much as ^95,000, but this (in 1894) was a record case. + This was the outcome of the Anci.oIndian Tki.f.cjh.M'H Conh'anv, formed for the purpose of establishing^ direct telegraphic communication to India by means of submarine cables, instead of relying upon land lines to the Persian (Uilf, and a cable thence as heretofore. The Anglo-Indian Company, however (which had acc|uired the Egyptian landing rights previously granted to the Red Sea Company, and had secured as their engineers .Sir Charles Bright, M.P., a"d Mr Latimer t lark), failed to raise the capital required for carrying out their enterprise. Mr H. C. Fordc acted as engineer to the expedition ultimately undertaken by their successors, the British-Indian Company. I Mr J. C. Parkinson has described this expedition in an interesting narrative, entitled " The Ocean Telegraph to India " (Wni. Blackwood and Sons, Edinburgh). S Considerable trouble of this nature had been experienced with the preceding cables of this type, as has already been shewn. Wires breaking at a weld, for instance, would get loose, and the broken ends become entangled with, or actually pierce, the next turn or tlake in the tank under pressure. Thus, not only was paying out rendered most hazardous, with serious prospects of a "foul," but the - which the proceedings of the Parliamentary Commission, appointed in connection with the Go\ernment Purchase Scheme, gave to the lucrative nature of telcgrajjhic cntcrpri.ses generally, together with the recent success of the Atlantic cable in deep water, emboldened financiers and capitalists to create fresh investments of the same character by pro- moting and supporting new companies for the further extension of submarine telegraphic enterprise.* Various schemes were promulgated from time to time for different forms of light cables, i.e., cables without any of the (ordinary iron wire sheathing. \one of these, however, came to anything. It would seem that nobod\- cared at that period — any more than thej' do now — to risk so considerable a |)art of the capital of a submarine telegraph comjjany as is employed (and, in the most literal sense, sank] in the cable itself, by staking its success * Former shareholders in llic " .Ma),'nelic " Company were especially pieclisposed to take a pecuniary interest in submarine telegraphy, in virtue of tlieir connection with the early Atlantic lines. DEVELOr.MENTS. Ill upuii an experimental — i.e., untried — change in its structure. Everybody preferred to wait for somebody else to make the experiment first. Iron- sheathed cables having been proved to be fairly satisfactory, the telegraph "orld generally thought it best to " leave well alone." It was uncertain, indeed, in the first place, whether an unsheathed cable could be laid at all ; in the second, whether, if laid, it could ever subsequently be recovered. Thus, practically speaking, the original type of submarine cable has been adhered to throughout, with certain modifications and improvements to meet various practical recjuirements. Nevertheless, in several concerns which were started, light cables, to be laid between certain points, formed the salient feature of their programme, whether for the manufacture and laying, or for the owning and working of submarine telegraphs. Quite a number of companies were " floated " about the same time for effecting telegraphic communication with the East, with America, and other parts of the world ; but those mentioned here were the schemes actually carried out. It will be observed that these successful enterprises were almost all set on foot by the .same financial group — men of shrewd business capacity, tas has been clearly proved in the .sequel. In 1868 the iNDO-EuuorKAN Tki^KGRAPH Companv was formed for establishing a more speedy and reliable line of communication between England and India than that hitherto afforded by the Turkish State land lines from Fao to Constantinople via Baghdad. [The latter had been erected about the same time as the Persian Gulf cables were laid to India. Their communication with luigland was by the Continental European system of telegraphs, through Austria to Paris and hence on to Calais.*] The linet was constructed for this compan)- b)- Messrs Siemens Brothers, who indeed had been the originators of the scheme, t which was completed by them in January 1870. It pa.ssed through German)- and Lower * The section from Constantinople to Baghdad had been open for traffic as early as 1 86 1, but the extension to Fao, for bringing Turkish Arabia (77W the Persian (".ulf cables and Indian land lines) into communication with Hombay and the rest of Inilia, was not eflfected until eight months after the layiny of the dulf cables. t In the course of this i)ook, whenever an important land line of any length is in question, it should be understood that the " line " consists of at least two conductors erected along the same route and on the same poles, or not, as tlie c.isc may be. t More connnonly than not in telegraph and cable matters, the contractors of an undertaking will also be found to have taken the fust steps in its original promotion— their objects being, in the first place, to keep their plant antl statT remuneratively employed, and in the second, to obtain a good profit from each such ancillary (or alimentary) enterprise. 112 SUKMARINE TELECK.M'IIS. Russia, a gt)()cl traffic bcini^ picked up as far as Teheran in Persia, uiiere it joins the system of the Indo-l-'uropean relcgra])h Department* of tlie Indian Government Tcle,t;raphs. 'I"his system extends, via Ispahan and Bushire (and includint;' the i'ersian Gulf cables already alhided to), to Karachi (or Kurrachee, as it used to be spelt), where it meets the rest of the Indian Government telccjraph systems. For British communication with the Continent of luirope, the I ndo- European Company lease two Government cables, or rather two conductors, each in separate cables. The line across the Continent is entirely aerial, with the exception of a few miles under a part of the Black Sea. In 1869 the Great N'ortiikkn TELKciRArii Company was estab- lishctl for the purpose of telegraphic communication between Europe, China, and Japan, by means of the Russian State lines through the Russian Empire, connecting up their cables in Europe with those in the Chino-Jajjanese waters. This company was the result of an amalgamation of the "Danish, Norwegian, and English," the " Danish-Russian," and the " Norwegian-ICnglish," Telegraph Companies. The first of these were owners of a cable between Denmark and Norway, laid by Messrs Newall in 1867, and of one between England and Denmark, laid by this firm in 1868, Messrs Hooper having supplied india-rubber core for the same. The second-named company were owners of a cable between Sweden and Russia, laid by Mes.srs Henley in 1869. The third company (namely, the " Norwegian-English ") had owned a cable between Noru a>' and Scot- land, which was laid in 1869. Messrs Henley were concerned in its construc- tion and submergence, the core being Hooper's. A few years later — namely, in 1872 — the Great Northern China and Japan Extension Telegraph Company (formed in 1870 and owning cables and land lines round about China and Japan) was also amalgamated with the Great Northern Telegraph Company. Thus, at the present time, the Great Northern Company owns 3,518 N.M. of submarine cable in European * This system was erected by Major (afterwards Sir) J. U. Hateman-Clianipain, K.E., and a staflf of "Sappers." The object of the Indian Government in constructing it was partly to bring Teheran, the capital of Persia, into telegraphic connection with India and Europe, and partly to establish more certain communication between these two great sections of the world than tlie old Turkish route aflbrded, or, at least, to create an additional line of coninuinication in case of the latter's failure. This last-mentioned event was by no means rare, the Maghdad-Fao section of the line having constantly been tampered with by the uncivilised Arabs of those parts. Another advantage anticipated from the new line was that it would be worked by educated and disciplined operative clerks instead of by tiie inirelialjle I'urkish underlings of their (Government lines. The politic;'.! importance also of no longer trusting all our telegraphic eggs to one basket— and thnt a Turkish one -was sufficicnt'v obvious. DEVELOPMENTS. II3 waters, and 3,511 X.M. in those of the I-'ar ICast — a very equal division. This company, partly on account of the tropical climate of the southern portion of the China Seas, have adopted india-rubber core, as made by Messrs Hooper, for some of their cables ; in fact, their system is made u]) of about equal ienfTths of india-rubber and ^nitta-percha cores — the two cores meeting, in some cases, in the same leni^th of cable. Their ex- perience as to the relative merits of each under similar circumstances must, therefore, bo most valuable. No signs of the teredo have, however, been met with in any of these cables, in the China Sea or el.scwhere ; and, as a matter of fact, some of the gutta-percha cores are not even protected bj' brass tape. As regards the l^uroucan .system of this company — ^just as in the case of the " Eastern " Company's luiropean system — a breakdown of one or two cables would hardly be felt, as the work can immediately be divided between other lines of communication, so ingeniously is the sj-stem dis- tributed, besides being connected by Government land wires through Denmark, Norway, and Sweden. The way in which the Great Northern Compan)''s system came to extend itself in the Far East is as follows : — As early as 1854, in view of the (at that time) apparent impossibility of spanning the Atlantic by a sub- marine cable, a project was mooted for establishing telegraphic communi- cation between Europe and America by means of land wires through Siberia on the one hand, and through North America terminating at Alaska (which was then Ru.ssian territory) on the other; these two systems were to be joined by what would be only a comparatively short length of cable — less than 100 miles — in the shallow water (maximum about 300 fathoms) of the Hehring Strait.* This project, of course, had to receive the a.s.sent and support of the Russian Government before it could be put into practical effect, and it was not until i^'65 that the Western Union Telegraph Company obtained a concession lor carrying it out. The Russian Government undertook to build the line through Siberia to the Echring Strait, whilst the American Companj' were to construct one across the North American Continent to the nearest ])oint on the opjjositc side, and to connect the two up by submarine cable. When both the land lines had been erected for some distance, the success of the Atlantic cables of 1S65 and 1866 caused the Americans to abandon the above projected * This route would have been quite impracticable owing to tiie const.mt snow :uul ice at the approaches. Further south a cable might have been laid across tlie Heliring Sea ''ill the numerous Aleutian Islands, the distance here being some 750 miles Ijetween the two continents, and the nviximum depth— avoiding certain parts— about 800 fathoms. I 14 SUBMARINE TKLEGRAPHS. connection with the Old World. The Russians then became anxious to turn their land line — already partly constructed — to some useful account ; and thus they conceived the idea of utilising them for overland communi- cation with China and Japan, to be completed by submarine cable. Kventually the concession for the latter was granted to the Great Northern Company, who had, in fact, already worked in the interests of Russia and its Government by establishing communication between that country and Denmark, and thence on to England./ These cables between the Russian Empire, Japan, and China (Posietta Bay, Naga.saki, Shanghai, and Hong Kong), were not actually laid until 1871.* The Hooper Compan)- contracted for their construction. Hooper's india-rubber core being used, whilst the sheathing was carried out by Messrs Siemens Brothers. They were laid by the staff of the Great Northern Company, from their new telegraph steamer " H. C. Or.sted,"t Mr C. L. Matheson being the engineer in charge, assisted by Captain (afterwards Colonel) V. Hoskic-er of the Royal Danish ICngineers, who subsequently succeeded him.* It was afterwards thought desirable to include Amoy in this far-eastern n'seaii. Instead of taking the cable into Amoy from one direction and out of it again in another, it was determined to " tap " the line between Hong Kong and Shanghai with a double-core branch cable to Amoy ; by this means a considerable saving was effected in a heavy and expensive type of shallow-water cable. This T-piece method was ado])ted at the sugges- tion of Mr J. R. France, following the example set at Bushire in the case * It may be remarked that neither the Chinese nor the Japanese had expressed any anxiety for this telegraphic connection with Europe. Permission, indeed, was not obtained from them until after the work had been executed, the shore ends being secretly landed in drain-pipes. The Chinese, when the cable had been laid, displayed a complete scepticism as to its uses, and refused to have anything to do with it. They were soon convinced and converted, however, by various practical demonstrations. t This was the first case of a cable-repairing ship built expressly for a cable-working company. The "H. C. Orsted" was christened after the famous Danish electrical j^tr^j;// of that name. Other ships fitted out for cable work and employed for the same kind of work were the " William Cory " and the " Chiltern," engaged for the "British-Indian" Company in 1870 (both of which had jjreviously done Atlantic cable work in 1866 and 1867), and the " Hawk," engaged for the Falmouth-Gibraltar Company. The " Chiltern " still does satisfactory duty for the "Eastern" Company. In the early days of submarine telegraphy very few such boats were fitted out at all, and still fewer specially built for cable-owning companies, as it was originally intended that the Telegraph Constrtiction and Maintenance Company should mainlai 1 in repair all the cables which they laid— hence the full title of that firm. \ Captain Hoski;vr was the author of two useful little volumes relating to submarine telegraphy, one from the engineer's point of \iew, and the other fiom that of the electrician. DEVELOl'MENTS. 115 of the Persian (iulf line. The required bi-cored cable was made for the Great Northern C"om|jany by Messrs W. T. Henle\-, and successfully laid for them by Mr France in 1873, the length bcin^ about 40 N.M., with the T-piece in 30 fathoms of water. This latter device was a complete success, and has gi\cn no trouble whatever down tf) the present da)'. The Kastcrn ICxtension Tele^^raph Company's system reaches as far north on the coast of China as Shanghai. There is thus a d(juble telegraphic communication between this place and Hong Kong — namely, one by the Great Northern Company's cable, and the other by the Eastern I'^xtension's ; the latter touching, en route, at a point near Foochow, instead of at Amoy. These two lines are, however, worked together by both companies under a "pooling" arrangement for their common benefit, so that the whole telegfaphic system of each is placed in communication with all these important towns and seaports.* Moreover, an additional wtjrking arrangement exists between these two comjianies, by which both .sj-stems may be said to receive individual extension. All the Great Northern Company's other cables have subsequently been duplicated (A.D. 1883, 1884, and 1891). Unlike similar cable-owning companies, they have usually laid their own cables from their repairing .ship, but in 1891 the Telegraph Construction Company laid (as well as made) their duplicate cables, together with some extensions. The " Great Northern " was the first instance of an entirely non-Hritish ccMiipany promoting submarine telegraphy purelj' on its own account, and the Danes deserve every credit for this their — far from inconsiderable — share in the work of building up the vast and magnificent system of ocean telegra]jhs which now encompass almost the whole world.f The same company has also been entrusted with the laying of an independent cable for the German and Danish Governments between those two countries, the manufacturers of which — at any rate of the sheathing — were the eminent German firm, Messrs Felten and Guilleaume. The (ireat Northern Companj-, it may be remarked, have always had the reputation of drawing up ver}- detailed specificatit)ns for their cables, as well as for \ery carcfull)- overlooking and indeed controlling the manufacture of them. \ * The F.astein Extension Company's original cables to China were laid the same year as those of the Great Northern Company's Eastern system -/>., i87i--ancl previously referred to. t Tlie only other foreign nation that has since taken any important part in the extension of submarine telegraphy is the French, who have recently made and laid a considerable length of cable. \ It should be noted, before leaving the subject of the Great Northern Company, that they were the first to succeed (in 1 881) in establishing land lines in China, in the teeth of a very strong native opposition. Since then the Chinese have built lines for themselves— Il6 SUKMAKMNK TKLIXiKAl'IlS. The coiiipanj's cnL;iiici.M-iii-cliicf, Mr 1'. (". Drcsing, origiiii.tcd a special form of cable suitable for shore ends on \ery rock)- coasts. It is of the ordinar)- shore-end t\'pe, but tlie outer sheathinj,' wiies are laid up with a ver)- short iaj', so as to ^et a maximum wei^^ht in a ;^M'\en circumference, and thus obtain a more pliable cable than would be the case if the same weight were obtained b}- means of larger wires laid in the ordinary wa)-. A shore end was made according to l)resi"g's s|)ecification by the lelegrapii Construction and Maintenance Company, and laid on the Chinese coast (at Hong Kong) to a distant lighthouse station in i.Sy^ ; its weight was 28 tons to the mile. This type having lately been ado])ted by the Anglo- American Company, for their Atlantic cable of 1S94, was fully described in the course of an able article concerning that enterprise bj- Mr Arthur Dearlove, in The Electrician of 12th October of the same year. In 1869 the Wkst India and Panama Tklixiuai'II Comtanv was formed, with the objects, first, of uniting telegraphically the West India Islands theinselves, and the Spanish Main ; and, second, of bringing them (as well as Brazil. Colombia, etc.), through the Western Union land lines at Florida,* into communication with the whole of North America and Europe. In connection with the same system, and under the same financial auspices, another similar enterprise, viz., the CUBA SUHMARINE Tklkckai'H Coni- I'AN^' was floated for the purpose of laying a cable along the coast of Cuba, thereby avoiding the necessity of using the Spanish Government land lines through that island. This completedf the suumarinc n'scnii from Florida (U.S.A.) and the Gulf of Mexico in the north, by the Greater and Lesser Antilles to Georgetown, Dcmerara, on the one hand, and to Colon, and thus on by an aerial line to Panama, on the other. P'rom the employing Danish engineers for the purpose — anc! have been working them witli the assistance of Danish operators, who have gradually trained a large staff of Chinamen in all branches of the service. In 1894 the length of the lines in China consisted of 15,000 miles of wire to about 21,000 miles of country. There were upwards of two hundred stations, worked by a staff of eight hundred clerks. ■* As a first part of this scheme, caJiles had been laid the \ear before between Florida and Key West (an island), and between Key West and Havana, Cuba. These cables were the property of the International Ocean Telegraph Company of New York, .'.ml are now worked for them by the Western Union Company as a part of the latter's system — by far the largest tclegra|)hic system in the United States, indeed the largest land system in the world. The Western Union was founded in 1S52 to work the " House '' type-printing telegraphs, but in 1854 the competing Morse system amalgamated with it. Since then the Western Union Company have absorbed nearly all the other telegraphs throuc^hout the United States, its principal rival being the Postal Telegraph Cable Company. t With the help of a short wire across the narrowest jiart of Cuba. DEVl'l.ol'MKNTS. 117 latter it was already contemplated to run another cable to the West Coast of South America.* In connection with this West Indian enterprise, some 4,100 N.IM. of submarine cable were manufactured and laid. l)einfj the greatest length ever dealt with, so far, in any single concern of the kind. The system (see ma]) below) comprised no less than twenty .separate sections between the islands from IMorida to the north coast of Central and South America. The cable was made by the India-rubber, Gutta-percha, and Telegraph Works Company, of Silvertownf (this being the first important cable contract which this now well-known and flourishing firm had undertaken), and was laid by Sir Charles Bright. No less than five steamers were ^ J/Ko^ i^-^-.^P^ -•"-^^<;^ 4 ■^J^ *'^]^r'*">--53^ \ k %, w •f^ ^Xi^'»^ ""-.^'"•J^ y' .' i ■$ \ /I ^W ai!S^ MtM ■ i '^■^, ^ / I ♦•yw.j^ % A*' •< / *'^A ^w I p X L*^ s*4 <> V ^jMii*"'^^ -^^p,^ K,r'9»'^ y \ "^"p **""'^ >' * ^3 / 1 r^'*OU*r « ifl * ^u« / 1 ^•tVc'^y^^^Sv \ > / 1 *' l^/ncVntjLs**'^^'''" A\ *"** / jffj ^t^Coracjo \ i^''"*^'" \ SanJu»n rf#/ iumJ*^ ^ / j^^y '"^^^fer^ ^ \f \ (vr"*""^ / ^^ \X ASpSB^brr/mrftfrf \ WviNte ^^d w\ , .^,>^ "^^^^^^^N. \ y\^^25 -Am ^■^«»MSiV4M^^«l Map shewing tlic West Indian Calilc Sy.slcm and its Connections (1S97). required for the work, including H.M.S. "Vestal" (Captain J. K. Hunter R.\.) as consort, besides three large sailing ships. These cables had to be laid on what is undoubtedly the \ery worst bottom that any submarine cable has ever been deposited on, for, in order * This was the scheme of the I'anama and South Pacific Telefjraph Company, which was formed to connect tip the chief towns of South America with Central America and the rest of the world, by submarine cables joininj; the previously existing land lines tluouf^h Peru (of the National Tclet,naph Company), and tiius conimunicatin,i;, throuj^h other land lines, with every centre of civilisation in the South American Continent. This scheme, however, was never carried out by the above-named company, thou},di, as will be seen, it formed a part of another undertakinjr later on. + For brevity's sake, to be henceforth referred to in this work as " the Silvertown Company"— a title by which it has become familiarly and generally known in the telegraphic world. _ ^.:._ • I Il8 SUHMARINK TI'.I.KCUAl'IIS, to reach most of the ishuuls, it has to j)ass over a cliaiii of coral.* In tlie manufacture of this ijreat length of cable, the core-com pound emploj'cd was different from that known as C"hatterton's mixture. I'iiis new dei)arture did not, however, prove such a successful experiment as had been antici|)ated ; its failure, indeed, was sufficiently conclusive not to warrant repetition, and since these West Indian lines, C'hattcrton's com- jjound has always been rigidly adhered to.f Mechanically, the above cables were all that could be desired, constitutinJ,^ in fact, the first return to the ordinary close-sheathed type for deep water.* Hri^dit's Bells used to be employed as the si^niallin^^ instrument on some of the.se lines ; and this is now the only system of cables in which the " mirror " instrument is exclusively employed. Following the above group of great enterprises in oceanic telegraphy, there was a slight lull in their further extension. Meanwhile its scientific facilities were brought to a greater state of ])erfection, for in 1870, Sir William Thomson had successfuUj' completed his invention of the "siphon recorder" for working long cables.^ It was immediately applied to all the great lengths in place of his " mirror " instrument ; 1 for it was found that it could be worked at ])ractically the same speed, and under practically * It is usually thought that the teredo worm did not pervade these waters at that time though traces of it have since been found. This ap|)arent aiioinaiy may be accounted fo- as follows : -Cables are nowadays frequently brought home from teredo-ridden waters and relaid elsewhere - sometimes after being ro-sheathed, sometimes in their previous con- dition. In all such cases the germs of tiic teredo are liable to be conununicated at the factory, quite apart from being afforded a free passage to various oceans and seas. + The patent expired in US73. J A portion of tlie second .Malta-Alexandria cal)lc had also, under the same engineer- ship, a close armour. S The first patent for an early form of this instrument had been taken out as early as 1867. II The mirror is now entirely replaced by the siphon recorder, except on the cables of the " West India and I'anama" and "Cuba .Submarine" Companies, as above mentioned, and on some of the northern sections of the Western and liiazilian Company. The l''rench company, while employing the siphon recorder on their long sections use the Morse with Siemens' permanent magnet recorder (similar to the Brown-Allan relay) for workinii some of their shorter lengths in the West Indies. Tlie Creat Northern Company, however, are in the habit of using for signalling purposes an instrument known as '^auritzen's " undulator,'' invented in 1876 by a former member of their staff. This based upon electro-magnetic principles, and, as regards the recording arrangemr cs, presents points of resemblance to the siphon recorder. This instrument (describ d fully in Part III.) is capable of being worked through very great lengths of cable .- ,id land line joined up together with translating apparatus between. This, moreover, it a high-working s|)eed, such as 65 words per minute through 1,000 N.M., and in another case go words a minute sititplcx\ and 60 duplex, through 550 X.M. Previous to this, the "Creat Northern" Company had used Wheatstone's receiver in connection with his transmitter. nEVEI.OPMKNTS. 119 tlic same conditions of Iciij^th aiul battery-power as tlie latter, Ijut uitli tlie advanta^fc of yieldin^^ an actual record of tlie si^nials as received, thus enabling; the source of error to be traced— besides other important advanta^'cs.* linth these instruments will be found dealt with at some len^'th in Tart III. of this work.t In iS-i the Silvertown Company made a cable for the l-'rench Government to be laid between Marseilles and Aligners. This cable was laid for the compaii)- by Sir Samuel fanning. In 1S72 the DlKlXT Si'.wisii Tklkcr.M'II C'omp.vny was formed, principally by tho.sc inter- ested in the Silvertown firm. Its object was to connect ICiii^land and Spain In- a direct submarine line, and thus avoid the delays and errors to which traffic, passing' over riovcrninent lines in foreign countries, is always liable. Accordingly, in the same year, a cable was laid for this company by the newly-formed Silvertown staff, headed by Mr F. C. Webb as engincer-in-chief * This line extended from a point near the Land's ImkI, Cornwall, to the north coast of Spain, in the neighbourhood of Bilbao.^ Subsc(]uently, in 1S.S5, this comi^any's system came under different direction, and it now forms a part of the "ICastern" group, or network of cable systems. In 1872 the four companies owning the cables on the direct route to India were amalgamated into the now world-femous I'.ASTKRN TkleckaI'II Com I'.WV, which was registered in June of that year. These companies and their cables (already referred to) were the so-called " Falmouth, Gibraltar, and Malta " ; the " Marseilles, Algiers, and Malta " ; the " Anglo- Mediterranean," and the " British-Indian." Their amalgamator and successor, the " Kastcrn " Company, now pos.sesscs by far the largest and. * Another strong point in favour of the recorder is that the c>'esight is not so liable to he damaged by reading the slip as it is by the strain of following the movements of a " shivering '' beam of light from one side to the other. Thus, a constant supply of good operative clerks is more readily oblainatile for working the recorder than for the mirror. + It is not unusual for a company to start with the mirror instrument and then to substitute for it the siphon recorder as soon as all the traffic arrangements are in thorough working order. This ])ian is especially convenient when the contractors work the cable for private ('• service ") work during the month's guarantee, in the course of which the ))ro])rietary company have a good opjjortunity of ]Hitting their system into V orking order, the recorder clerks getting the new instruments, etc., set up ready for regular public traffic. The mirror instrument, moreover, is always useful as a reserve at each station in ca=;e of anything going wrong with the recorder. I Succeeded in that capacity in later years by Mr Robert Kaye CJray. S This cable w.is originally laid over what proved to be a very remarkable hole about 30 miles north of Bilbao. Here, within a distance of about one N.M., the depth \aries from i,cxx) to 2,000 fathoms. In the laying of the present cable liy the Telegraph Construction and Maintenance Company in 1884 this hole was avoided. 120 SUBMARINK TELEGRAPHS. from a national point of view, the most important telegraphic system in the world. It was promoted under the chairmanship of Mr Pender (afterwards Sir John Pender, G.C.M.G., M.P.), with Lord William Hay (now Marquis of Twecddale) as vice - chairman. Sir James Anderson * became the general manager (afterwards managing director), and Mr George Draper the secretary. This consolidation having been accompli.shed, in the following year (1873) the Ea.stern Extension, Australa.sia and China Telegraph Company was formed for absorbing those companies which owned the extension lines to the further side of India, the Straits Settlements, China, and Australia, already referred to. The companies thus incorporated were the " British-Indian Extension," the " China Submarine," and the " British- Australian." The board of this amalgamating companj' was an equally strong combination to that of the " Eastern" Company, being, in fact, very similarly composed, and presided over by the same chairman, with the Right Hon. \V. N. Massey, M.P., as vice-chairman.f It may be mentioned here that an important extension of this com- pany's system was carried out in 1876, b>' the submersion of a cable for them (acting in concert with Sir Julius Vogcl, K.C.M.G., who represented the Government of \cw Zealand), by the Telegraph Construction Company, between Australia and New Zealand Within recent years telegraphic communication with the P^ast, by the Eastern Telegraph Compati)', has been further strengthened through the leasing of a line for their service between London and Marseilles, and thence by cable to Bona and Malta. The principal portion of the traffic between Great Britain and the ICast now passes over this line, in prefeience to the more oceanic and circuitous route via Lisbon, Gibraltar, and Malta. As a part of the " l^a.stern " Company's system, in 1874 the Hlack Sk.v Telegraph Company was formed for the purpo.se of working a cable across the Black Sea from Constantinople to Odessa At the latter point it was to meet the Russian State lines, communicating with the Great Northern Company's system at Moscow, and thus to connect Constantinople, * .Succeeded, since his death in 1893, by Mr John Dcnison I'endcr, tlio present m.ina^'ing director. + It is perhaps Iiardly necessary to add tliat the directorate of tiiesc two great companies represents a similarity very nearly approaching to identity between the fin.mcial groups which control each of them anil which used to control the original seven companies from which they sjirang. These enterprising capitalists — some of whom from the very beginnings of ocean telegraphy had staken'ANY was formed, to connect up the Western and Brazilian Company's system with that of the West India and Panama Company, thus placing the former comjjany in a doubly-.secure position as regards its communications with Europe. These cables were laid in 1874, forming an object of the * The latter was the outcome of the (jreat Westcin Telegraph Company, promoted by the same capitalists, which had for its object the laying of a cable from England to liermuda, and thence to the United States on the one side, and to the West Indies on the other, thus estaljlishing a more direct communication than heretofore with the latter. Though a large portion of the cable destined for this pvrpose was manufactured, and a ship specially designed for the work, the original scheme v/is never carried out ; but the "Western and Brazilian" was financially substituted for it. + This firm, indeed, had been largely interested in the promotion of the enterprise, as well as in the original (ireat Western scheme, referred to in the last note. I Most of these cables were of the light type, each iron wire being enveloped in hemp, and originally intended for use in deep water in connection with the (ireat W^estern scheme. They subsequently proved to be peculiarly unsuitable for the Brazilian coast, partly on account of the attacks from fish which they were subjected to in the shallow water therc prevailing. This "open-jawed'" pattern is always liable to be victimised in that way. In this particular instance, however, it is only fair to remark that the close-sheathed type of cable, laid in the same fish-ridden waters at the mouths of rivers, appears to have experienced no more immunity from these attacks than the other. Indeed, in the close- sheathed cable more faults could be actually traced to that cause, owing to bits of fish Iviviiij^ been broken ofi' inside ; whereas, in the case of the open type, the fish ap|)ear to have succeeded in entirely extricating themselves from the wires, after effecting their mischievous [)urpose. It has also been suggested that the core of the old opcn-shcathed type had an in- sufficient thickness of intlia-rubber. Although sword and saw fishes seemed to be dis- agreeably plentiful on the north coast of South America, yet, contrary to expectation, there were no definite signs of the teraio either there or in the West Indies. Notwithstand- ing the many faults that have been experienced and repaired, the teredo was never given as their cause. 126 SUBMARINK TELEGRAPHS. same expedition — being, in fact, manufactured and laid by the same hands as the Western and Hrazihan. The len<^'th was about 1,000 \.M., from Para, the most northern pcjint of the " Western and Brazihan " system, to Demerara, the most southern point of that of the " West India and Panama." The main cable had a T-piece running into Cayenne about midway between Para and Demerara. This was the first T-piecc of its kind,- that is to say, where the branch is composed of a single conductor serving for both circuits in either direction. In this case the T-joint — about 50 miles from shore, in about 50 fathoms of water — was made in the conductor (and insulator) itself at the point where the branch from Cayenne met the main conductor stretched between Para and Demerara. This T-joint was protected by a corresponding T-splice.* These "Central American" cablesf subsequently, and after several repeated repairs at different points in their course, failed altogether. In 1876 they were abandoned, and the company wound up, thus leax'ing no connecting link between the Western and Brazilian and the West India and Panama systems.* * Here we have the way in which all T-pieces are effected nowadays, and there have been at least three made since — one at Hathurst in the West African Company's system, one at Panama (Central and South American Company's), and one at Mole S. Nicholas in the French Company's West Indian system, not to mention another at Cayenne in the same trsciiu. All of these have been deposited in quite shallow water — i.e., under 100 fathoms. I5y this plan, when it is worth while, the greatest economic advantage can be secured ; for whenever it happens that the branch cable only is damaged, the break of com- munication is confined to that. By the original system, on the other !iand ((•..;'., of carrying the main line in and then out of the station in question), if the branch happened to get broken — being in this case really part of the main, the whole c ibk-, between the two stations on each side, was rendered useless until the branch was repaired. The old method is, in fact, not truly a T-piece method at all, for there is no T-joint. The two conductors of two ordinary shore ends are simply enclosed in a single cable, the so-called T-splice being effected where each conductor is jointed to its corresponding end of the main cable. The new plan has proved perfectly successful in all instances, and, with improvements in T-joints, and increased skill in jointing work, it is found to be just as reliable. It is true that it involves a little more trouble in test-calculations (as may easily be understood), so that it is liable to render the localising of faults somewhat irksome. This, however, is a comparatively small matter. Outside the entire T-piece the two halves of an iron bo\ are now often placed round each side and fixed on firmly, thus giving the T-piece increased security. This addition, by taking the strain off the joint, renders a finished splice — a somewhat lengthy, troublesome, and, at the best, unsatisfactory operation at sea -quite unnecessary. Such a plan was first devised by Mr ^T. H. (iray for the Bathurst T-piece. t Not to be confounded with the true Central American system of the Central and South -Imerican Company, hereinafter referred to. I Telegraphic communication between the West Indies and IJrazil was restored, however, in 1891 (rvV; Brazilian land lines) by La Compacnho FranCjAISf, dks Tti.t GRAPHES Solts-Marins, the scope of whose system will be described later on. . DEVELOPMENTS. 12/ Iii 1874 ;i scries of cables were laid in southerly extension of the Brazilian Company's system down the coast of Hrazil and Uruguay, from Rio de Janeiro to Montevideo, calling at three points en route. These cables — running into some 1,200 \.M. — were laid for the Co.MPAXHIA Ti:le(;kakica PLATINO-IiKASlLIERA,* and were constructed and laid by Messrs Siemens Brothers. Under an agreement, the Western and Jirazilian Company were to work these cables for the local company ; and subse- quently (in 1879) they too'; them over altogether, under the title of the " London-Platino-Br^zilian Telegraph Companv." At Montevideo this .sy.stem connect.s up with that of the RiVER I'LATE Telecjkaph Ccj.MPANY, t reaching to Buenos Ayres and a short way up the Rio de la Plata. A few years before the Platino-Brazilian cables were laid, namely, in 1872-73, another company — the MONTEVIDEAN AND BRAZILIAN TELE- GRAPH Company — had been formed to establish a direct cable between Montevideo and Chuy. This cable was made and laid by Mr W. T. Henley. It was subsequently bought up by the Western and Brazilian Company (into which the Montevidean Company was " absorbed "), and now forms part of their system — a continuation, in fact, of the " Platino " cables — together with the other duplicate line laid by the Telegraph Construction and Maintenance Company in 1892 between Chuy and Santos. In connection with the River Plate cables a land line runs across the South American Continent to Valparaiso, a distance of some 700 miles, thus putting the Western and Brazilian s)'stem in communication with the cables running along the West Coast of South America. In 1895 the Western and Brazilian Company promoted an extension of their system up the Amazon River, and a company called the Am.vZON Telegraph Company was formed with this object. The cables for this new company were laid last year by Messrs Siemens Brothers. The line extends from Para to Manaos, nearly half-way up the great river, in the heart of Brazil and the plains of the Amazon. There are sixteen stations on the line altogether, its total length being over 1,300 N.M. This cable is expected to further develop a large india-rubber, coffee, and sugar trade. All previous attempts at telegraphic communication by means of land lines * Entirely promoted in Brazil, but somecimes known as the " River i'late and Hrazil Telegraph Company." + A company of completely local orign, with which the Western and Brazilian have a working arrangement. The construction and laying of this line was carried out by Mr \V. T. Henley as early as 1866, the length being 30 N.M. only. 128 SUHMARINE TKLEGRAPHS. had prc.-cd unsuccessful, owing to the rapidity and density of forest growtiis in tiiis o.r t of the world.* The cables of the Brazilian Submarine Telegraph Company, although this concern was launched a few months previous to the Western and Brazilian, were not laid until the following year, 1874, by the Telegraph Construction Company. These cables extend from CarcaVellos fLisbon) to Madeira,! thence to St Vincent (Cape Verde Islands), and thence to Pernambuco, in Brazil;* the system being placed in communication with Great Britain by means of the "Eastern" Company's line from Porthcurno to Lisbon. The latter forms part of their Anglo-Spanish-Portuguese system. The "Brazilian Submarine" Company, it may here be remarked, is (finpncially and in \\.^ personnel) clo.sely allied with the " Eastern." In 1873 the Direct United States Cable Company was formed, * Indeed, in the case of the cable, the new experience of laying one up an immv. se river whose bed is subject to very considerable and frequent changes, has in itself turned out a formidable business ever since the line was completed. Notwithstanding that Messrs Siemens Brothers and Co., the contractors, and Messrs Clark, Forde, and Taylor, the consulting engineers, took precautions in the way of preliminary survey, soundings, and selection of route, several of the sections have in turn been interrupted — more or less continuously — subsequent to their submergence. The greater part of the trouble has been in the upper w.\ters, where numerous subsidiary rivers flow into the Amazon, and where, in the rainy season, enormous masses of debris, in the shape of trees, etc., are carried down by the extremely strong prevailing currents, which latter have also the effect of scouring out the bottom, thus leaving the cable unburied in places. Elsewhere the cable has sunk so deeply into this unusually soft mud that much difficulty is met with in recovery. Rocks which had not been discovered in the survey have since been found to be an additional source of breakdown. This line was laid in the middle of the stream with the idea that here there would be the least prospect of any vessel anchoring and destroying it. With the knowledge since obtained, it would seem that the cable might have had a better chance if laid more on the bank of the river, where it would soon become deeply buried in the sjft bottom, and be less liable to disturbance at the hands of moving matter. Recovery-work here must, in any case, be a subject of immense labour. For further particulars regarding this line, see lecture recently delivered by Mr A. Siemens, M.Inst.C.E., at the Royal Institution. t A very curious circumstance occurred in regard to this Lisbon-Madeira section in 1891. The cable was found to have broken in 1,500 fathoms, not far from Madeira, on the very day that an immense tidal wave was observed. It was concluded accordingly that the latter must have had something to do with the rupture of the cable, although beyond the strange coincidence there was no proof of any connection between the two occurrences. On the other hiind, during the laying of the above, the T.S. "Seine" discovered a bank in latitude 33" 47' N., and longitude 14' 1' \V., the depth being about 100 fathoms, with 2,400 fathoms in its immediate neighbourhood. In those days soundings were not taken as closely as has since been found to be necessary, the result being probably that the cable became suspended in a festoon when submerged. \ This last section lasted nine years before any sort of repairs were necessary — or even before any fault proclaimed itself— a record case, in fact. DEVELOPMENTS. 1^9 being the first competitor with the " Anglo-American " Company * so far as concerns direct submarine communication between Great Britain and the United States. This cable was originally intended to have been taken direct to the shores of the United States, without any intermediate land line over New- foundland or any other part of British North American territory— hence the term " Direct"' in the title of the comjiany. Ultimately, however, it was decided that if the cable were laid thus, in a single length, the working speed attainable (with the core provided) would be too low to compete with the different lines of the exi.sting company. Accordingly, attempts were made during the expedition to land at Newfoundland,+ but landing rights being withheld there, the end was eventually taken ashore at Halifax, Nova Scotia (where several other Atlantic lines have since been landed), and from there another was laid to the United States. Messrs Siemens Brothers, who had taken an active part in the pro- motion of the compan)', were the contractors, both for manufacture and for submersion. + It was, indeed, the first really important length with which this firm had been concerned as manufacturers. Mr Carl Siemens was placed in charge of the expedition for laying it, which was attended with complete success, and the line was opened to the public in 1875. Later on, in 1877, the direction of the Direct United States Company passed into other hands — indeed, the company was reconstructed — and their system entered into the " pool " or "joint purse," established shortly after the 1869 Atlantic had been laid.§ * This company had just had two fresh cables laid for them (1873 and 1874) by the Telegraph Construction Company with some of their usual staff. The laying of the 1874 Atlantic line was the last piece of telegraph-work performed by the "Great Eastern." A sectional view of this leviathan vessel, as disposed for cable operations on this occasion, is given in Fig. 48 overleaf. She has since been broken up, after being employed (amongst other things) as a sort of floating " variety show " I New cables were first rendered necessary — according to the joint-purse agreement pre- viously referred to — by the final breakdown (after several repairs) of the 1866 cable in 1872. Later on (in 1877) the 1865 also succumbed, and another " Anglo" cable was laid by the same contractors in 1880. In this latter cable the shore ends of the old i866 were turned to good account, but all the deep-sea type was new. With the exception, therefore, of the shore ends, all the old cable remains abandoned, and it is most inaccurate to describe the two cables (1866 and 1880) as one, as some have done. The Telegraph Construction and Maintenance Company laid this 1880 cable without any hitch or stoppage within the surprisingly short space of twelve days — the " record " up to date in Atlantic cable-laying. + A suggestion of this may be gleaned from the chr.rt by the circuitous route which the cable makes. + This cable was of the same hemp and iron combination then still in vogue with soine authorities for e.xtreme depths. Here the hemp was again compounded before application to each wire. A whipping with about h inch or so between the turns was applied finally. S This plan originated as follows :— After working in opposition to the " Anglo- 130 suhmarini-: tp:lix;raphs. In the same year (1874) the Silvertown Company laid a cable for the Direct Spanish Telegraph Company between Marseilles and l^arcelona, thus extending their system to France, ind thereby constituting a kind of Anglo-Spanish connection with the " Eastern " systems, of which now, since 1885, it forms a supplementary offshoot. The telegraphic communi- cation of Spain with the l"'.ast, as well as with the rest of the Kuropean Continent, was now doubly secured. In 1876 the original Wkst Coast of America TELEGKArii Company was incorporated, whose objects were to purchase and work cables on the coasts of Chili and Peru, between their capitals Valparaiso and Lima, as well as to put the latter into communication with the Western and Brazilian Company's system, and thus with Kurope, b)' means of the land line of the Transandine Telecraph CO-MPANV,* and the "River Plate " and " Platino-Brazilian " cables. This West Coast of America Company's cables had been made by the Silvertown Company, and were laid by the .same firm, in .seven sections, during 1875 and 1876. The greater part was submerged previous to the actual formation of the " West Coast " Company.f The company itself was originally constituted almost entirely of, and by shareholders in, the Silvertown (or India-rubber, Gutta-percha, and Telegraph Worivs) Company. American" for about a couple of months, the French Atlantic Company accepted their rival's invitation to form a pool or "joint purine," made up from the nett eaii^ings of both their cable systems, the revenue accruing to each company therefrom .0 be fixed in proportion to its respective contributions to the said pool. Subsequently all the Atlantic cables, with two exceptions, have come into this arrangement, and now constitute — for practical purposes — one great financial comljination. A somewhat similar working arrangement now exists also — so far as regards the Indo-European traffic receipts — between the Eastern Telegraph Company, the Indo- European Telegraph Company, and the Indo-European Department of the Indian Government Telegraphs. This originated at t'.i2 insta.ice of the Indian Government, who (by their initial agreement with the British-Indian Su'miarine Telegraph Comjjany) granted landing rights to the latter for the Snez-.\den cable in 1869. Another instance of the "joint-purse" arrangement is that which exists between the "Eastern Extension" and "Great Northern" Companies regarding the traffic by their respective cables between Hong Kong and Shanghai. * This local (Chilian) company — Comi'AN'ia dki. Tki.kok.m-o Tk.ans.wdixo— had obtained authorisation from their Government in 1870 to work a land line between Valpa- raiso and Villa Maria, Chili. This line was subsequently carried across the Argentine frontier, and right on to Iluenos Ayres, with intermediate stations. The whole system was ultimately purchasttl (in 1891) by the Central and South ."Xmcrican Telegraph Company, whose lines are hereafter referred to. The origin of the title " Transandine " is sufficiently obvious ; but it is interesting to remark that in certain very high Andine altitudes the line has not been carried, strictly speaking, 07'cr the mountains, Ijut rather under them— at any rate under t/ic soil, subterranean cable having been perforce employed for 70 miles, where no aerial line could be expected to withstand the prevailing snow and wind. + Probably the only case of its kind. .. , [Platk VI II. \t [=1 1>^ c rj ■s O ■3. E I u 'J vO \0 vo u, S < u x il U ^1 ■a » ■3 [ To face p. 1 30. IJEVELor^rl•:NTS. iS' But subsequently, in 1877, it underwent a reconstruction, and has become closely identified with the " Eastern " and its allied companies.* Another period of calm or inactivity in the further extension of marine telegraphy now supervened, lasting until 1879. In that year i.'ye Kastern AND South African Telegraph Company was launched, under the financial auspices of the "Eastern" group. Its purpose was to establish and maintain telegraphic communication between Aden (where it would connect up with the " Eastern " Company's system) and the Cape of Good Hope, by means of a series of cables down the East Coast of Africa, joining, at Port Natal, a Government land line to Cape Town, which had been completed in i878.t These cables were all manufactured by the Telegraph Construction Company, and laid by them in 1879. Their combined length was as much as 3,900 N.M., one section alone — that from Aden to Zanzibar — measuring 1,915 N.M. The same (Eastern and South African) company have since placed one of the Seychelles Islands, as well as the important colony and naval station of Mauritius, in telegraphic communication with the rest of the world. This extension, joining their main system at Zanzibar, was carried out for them (by the Telegraph Construction and Maintenance Company again) in 1893. Another extension of theirs, down the lower part of the West Coast of Africa to the Cape — being, in other respects, a continuation of the West African Company's system — will be found referred to in .^.i proper place. In 1879 another French company was formed, to establish independent communication between France and the rest of the European Continent on the one hand, and the United States of America on the other. The — to English ears and lips — somewhat cumbersome title of this concern was La Compagnie Fkan<^:ai.se du TelEgraphe de Paris a New York, 'out it soon became styled in England as the " Paris and New York Telegraph Company," or, more commonly still, as the " Pouyer-Qucrtier Company," M. Pouyer-Quertier being its presiding genius. The cable, generally known as the " P.O.," was made and laid in the .same year by Messrs Siemens Hrothers, Mr Ludwig Ei-efiflcr being in charge of the ,1 * The West Coast of America Company's system lias since been extended by the establishment of land-line communications with fresh points in the interior, the most important town so connected up being Santiago in 1889. + The sea-bottom rountl the Cape is not at all favourable for a cable. Moreover, the land lines, complctcil and harmonised in one "system"' the previous year, as worked by the Cape and Natal Government Telegraph Departments, had proved thoroughly efficient and reliable. 132 SUBMARINE TELEGRAPHS. expedition.* This cable runs almost between the same points as the original "French Atlantic " cable of 1869 (subsequently absorbed by the "Anglo" Company), although the positions of its terminal stations on the American side are not quite similar. It was laid, however, along a different route.t The " P.O." Company afterwards joined the " Pool." Quite recently, however (in 1894), it was amalgamated with La Socii'':Tfi tRAN(;AlsE DES TklEGRAPHES Sous-Marins, under the title of La ComI'AGMK P'ran<;aise dks C.xulks Tklkgraphiques. Since this amalgamation it has withdrawn from the Joint-Purse. In 1881 an American company was formed, under the guidance of the late Mr Jay Gould, entitled the AMERICAN Telegrai'M AND Caisle Com- PANV, with a view to partaking in the profits of trans- Atlantic telegraphy by establishing another line of communication between the United States and Great Britain, and thence to the rest of Europe. This cable was also con- structed and laid (in the course of that year) by Messrs Siemens Brothers, ^ who were part promoters of the enterprise, as well as another cable for the same system in the following year, i882.§ This company's cables work in connection with — are, in fact, leased by — the Western Union Telegraph Co.mpanv, which was practically Jay Gould's property, and remained so up to close on the time of his death a few years ago. In 1883 the above system entered the " Pool" — the happy destination for which, may be, it was originally launched into e.xistcnce. * This scheme had taken three years to " mature " before it reached contract point. It was in the first instance promoted and financed by several large Parisian banking-houses and French merchants, and further aided by Messrs Siemens. + Both this cable and that of the "Anglo'' Company's 1869 French .Atlantic are connected with Great Britain by means of cables between IJreot and I'orthcurno. I The reason why such an enterprising people as the Americans come to England for their cables is that no factory for the purpose exists in the United .States. The same explanation applies to the two French Atlantics (of 1869 and 1879), both of which were made in England. Since then, however, submarine cable works have been established at Calais. A cable factory was also established at Milan in 1886 by Messrs Pirelli and Co., an Italian india-rubber and gutta-percha firm, and there are several factories for making core of various descriptions in France, the United States, and elsewhere, besides those in England. The absence of any submarine cable factory in the United States is probably due to the fact that they possess no colonies over sea to whicli to lay cables. S Notwithstanding the distance between the parties here concerned, the preliminary negotiations appear to have been remarkably t|uickly transacted. Report has it that an estimate was asked for and supplied by "wire"— exceeding a million sterling— on which the following message was sent with a view to concluding the business : " Make and lav two cables. Fifty thousand pounds at yourbankcrs." In connection with tiiis story, it must be remembered that Mr Von Chauvin— then associated with Messrs Siemens Brothers- was in New York at the time. Apart from this, however, the ra|)i(lity with which a con- clusion was arrived at is a great compliment to the high position enjoyed by the house of Siemens, and to the renown attached to that name. DEVELOPMKNTS. 133 In 1880 the Mexican Telegraph Company was formed by a body of American capitalists, and»in the following year the CENTRAL AND South American Tele(;raph Company was floated by similar hands. The object of these two schemes was to bring Mexico and the West Coast of South and Central America into direct communication with the United States {i.e., independent of the West Indian lines), thus also diverting through the States part of the aforesaid traffic with Europe. The cables across the Gulf of Mexico were laid between 1880 and 1882, and tho.se for the Central and South American Company, along the West Coast, in 1882. The latter started from Peru, at the spot where the system of the West Coast of ^\merica Company ended ; touching at Panama and various points of communication with other systems, they extended to the Gulf of Tehuantepec. By means of a land line across the isthmus of the same name, and a short cable on the other side, they there met with the Mexican Company's cables at Vera Cruz. The Silvertown Company were the contractors for the manufacture and submersion of all these cables,* those on the West Coast comprising eight sections, and having a tf)tal length of 3,200 N.M. The Central and South American Company have within recent years (in 1891) extended their .system to Valparaiso, and thence by land line to Santiago, thus entering into com]jetition with the West Coast of America Company. They purchased at the same time the Transandine Telegraph Company's land line from Valparaiso and Santiago to Huenos Ayres (with its four intermediate stations), thus securing an independent connection of their own with the great Argentine and Uruguaj-an capitals, Buenos Ayres and Mcjiitevideo. By other land lines through Brazil they also reach Rio. This (Central and South American) company's connection with Europe is, however, as previously mentioned, exclusively bj- \\a.y of the Mexican Company's .system, the Western Union land lines, and the Atlantic cables to England and France. In respon.se to this move on the part of the American group, the West Coast of America, the Western and Brazilian, and the Brazilian Submarine Companies joined forces to promote another company in the following year for erecting a new land line acrcss the Continent in their own interests. It is entitled the P.VCIKIC AND EUROPEAN TeleC.RAI'II ComPANV. The construction of the required line followed .soon after, along a route rather to the north of the Central and South American Compan)''s, but connecting the same points with one intermediate station. This line was open for traffic in March 1894. ■• Since this Messrs Siemens Brothers have also laid a cable across the Gulf of Mexico for the Mexican Telegraph Company. K 134 SUBMARINE TELEGRAPHS. In 1883 the Spanish National Telegraph Co>H'Anv came into existence. This company (with subsidies from the Spanish Government) was founded to create and maintain telegraphic communication between Sjjain and her possessions, the Canary Islands, as well as to effect — by the help of another subsidy from the French Government — an extension from the Canaries, thus connecting the luiropean Continent with the French colony of Senegal, West Coast of Africa. The first part of the enterjjrise was carried out in the same year, and the second in 1884. The Silvertown Company, who had practically floated the " Spanish National," were the contractors for the manufacture and laying of these cables.* The first part of this company's system, connecting Spain with the various Canary Islands, was taken over in 1893, after ten years' working (accordi ig to the original agreement), by the Spanish Government. The system in its entirety now forms a connecting link with continental Europe and England for the South American Cable Company's system — to be hereafter referred to — which it joins at St Louis, Senegal. Two more African cable companies were registered in the latter part of 1885, namely, the West African Telegraph Company in September, and the Al-RICAN Direct Telegraph Co.mpanv in December. The former was promoted by the Silvertown Company, and was to work in connection with the Spanish National Company's system ; the latter was an offspring of the " Eastern " Company group. These two companies had each obtained subsidies or guarantees from the various I^uropean Govern- ments — French, Portuguese, and British — to whom the different colonies belonged,! at which it was proposed the cables should touch, going along the West Coast and including St Jago and St Vincent. * Before starting cable-laying, the T.SS. " Dacia" and " International," employed for the work, sounded from Cadiz towards the Canaries on two separate zig-zag routes — the virtue of which will be obvious. No less than 552 soundings were taken in t'lis way at distances of 10 miles apart. In the course of this survey the " Dacia" discovered a bank in latitude 31" 9' 30" N., and longitude 13 34' 30" W., the depth being 58 fathoms in the immediate vicinity of 2,ooe fathoms - analogous to the relative heights of St Paul's Cathedral and some of the tallest Swiss mountains. These soundings were in what might otherwise have been taken as the line for the Canaries cable. Later on another vessel took over 1,000 soundings down the West Coast of Africa as a preparation for the cables to be laid there. These surveys have been described in detail in the ( nurse of two interesting papers by Mr J. V. Buchanan, E.R.SS. (Lond. and Edin.), before the Royal Society of Edinburgh and the Royal Geographical Society respectively, witli full details regarding the extremely stong currents from the rivers on the "\Vest Coast." Mr Buchanan was a member of the famous "Challenger" Expedition, and took a special part in the above highly scientific submarine researches for which the Silvertown Company are now famous as a matter of ordinary routine antl jjrccaution pre\ious to laying a cable. + The West .-Xfrican Company had secured agreements with most of the forbign possessions and protectorates, while the ".African Direct" had arranged with the British, and, in the case of the cable up the Cameroon Kiver, with the Germans. DEVELOPMENTS. 1 35 The West African Company's cables were made and laid for them by the Silvertown people in the course of two expeditions, during 1885 and 1886* Starting from the southern terminus of the Spanish National at St Louis, Senegal, this system extends to St Paul de Loanda, serving eleven stations on the way, mostly situated in the Bight of Benin, where cables behave better than men. The African Direct system was made and laid, about the same time, by the Telegraph Construction and Maintenance Company. Through the instrumentality of the two sections between the West Coast of Africa (at Hathurst) and St Jago and St Vincent, this company secured its own com- munications with Europe via the Brazilian Submarine Company's lines to Lisbon, and thence by the " Eastern " Company's direct cable to England. Two years after this, the Eastern and .South African Telegraph Com- pany determined to extend their East Coast of Africa system by a cable from Cape Town, via Mossamedes and Benguela, to Loanda, the southern terminus of the West Af ' in Company's .system. Going south, the first of the two sections — that between Loanda and Benguela — was made and laid by the Silvertown Company, and the other by the Telegraph Con- struction Company. Communication was thus completed, in 1889, along the whole West Coast of Africa down to Cape Town. These three systems comprise nearly 8,000 miles of cable. It was now arranged that the West African Company and its cables should be taken over by the " I'^astern " promoters, so as to constitute, with the African Direct and the Eastern and Southern African — and for their mutual benefit — one working system of alternative communications with the Cape. ICach of the stations served by these three systems have an opportunity of transmitting, on the combined system, any messages they may have at stated times during the day. In the field of Atlantic telegraphy, a fresh competitor arrived in 1884, in the person of the COMMERCIAL CABLE CoMi'ANV. Two cables were laid across the Atlantic for this companj- in the same year, its promoters wisely foreseeing that, in view of the continual chance of a breakdown, this was the only way in which they could safely attempt to compete with their more firmly established rivals. The " Commercial " Company was mainly promoted by two .American millionaires, Mr J. W. Mackay, the celebrated New York financier, and Mr Gordon Bennett, proprietor of the Neiv York * In the course of layiiif; some 3,000 miles in a hot climate with many exposed ends and splices, it is satisfactory to note that in this instance not a single fault was revealed. 136 SUBMARINK TELECKArilS. Herald* vith whom were associated the Messrs Siemens, who became afterwards tne contractors for the enterprisc.f These cables, like the Jay Gould lines, stretch from the extreme south- west point of Ireland (which is connected by special cable with England) to Nova Scotia, and thence to the United States — one of them direct to New York. The system is directly connected with that of the Canadian Pacific Railroad Company, thus affording ready communication with the Dominion. Neither the Commercial Company's system nor that of the Compagnie Fran'VAISE des CAhles Tklixikai'HIQUES is at present in the "Atlantic Pool " ; the)-, in fact, constitute the two exceptions prcviousl)- referred to. In 1886 the Italian Government entered into a contract with SociKTA Pirelli, of Milan,;!: for the construction and maintenance of a number of cables — about 700 N.M. in all — to connect various islands in the Adriatic and Mediterranean Seas with the mainland, chiefly for military and naval purposes. For the execution of this contract, the Societa Pirelli built a cable-sheathing factory at Spezia, and a telegraph ship — the " Citta di Milano" § — in England, Messrs Johnson and Phillips supplying the machinery for both. The core was made at the Milan works, and sheathed at those of Spezia. M. Pirelli had also engaged the .services of Mr W. S. Seaton, who superintended the construction and laying of these cables on behalf of the " Societa." This Italian firm has since carried out other similar work, on a small scale, for its own Government, besides constructing and laying a fresh series of cables between the Balearic Islands (in 1890J for the Spanish Govern- ment. |! In electric lighting it was still earlier in the field, that department of electrical industry having been quite pmctically developed in Northern Italy for .some time past. * Whence the concern is still often spoken of as " the Mackay-Hennett cables." t The construction and sejiarate laying of the two cables (\\\ the course of diftierent expeditions) within tlie same year, forms probably the smartest performance in cable work up to date, representing, as it does, over 6,000 N.M. of cable. .At the factory some 50 X.M. were turned out each twenty-four hours from ten machines. \ .A firm of india-rubber and gutta-percha manufacturers (previously alluded to) who had been making core during the last ten years. S In future, wherever a properly equipped telegra,'h steamship for permanent cable work is referred to, the letters "T.S.," as i p.'cfix to the ship's name, must be taken to stand for " /cAx'/vj/// j/tv(W(V."' This implies l.er l\;\ing tanks, paying-out and jiicking- up gear, also deep-sea sounding apparatus, ;ind that she is still afloat as a telegraph siiip. II For further information conrerning the Italian ("iO\crnment cables, and the work executed for them by the I'irelli firm, the reader who is familiar with the language ;Tiay be referred to an excellent little Italian treatise recently produced by one of Mons. Pirelli's associates. Signor K. Jona, which is entitled "Cavi Telegraphici Sottomarini." _ DEVELOPMENTS. 137 Down to nine or ten years ago the French had not troubled themselves much about cables to their colonies or foreign parts, and the few they had felt necessary they got made and laid f(jr them by English hands. Latterly, however, they have concluded to render themselves more independent of British lines of telegraphic communication, and with this object have com- menced in earnest the work of making and laying cables on their own account. Thus in 1887 the French Minister of Posts and Telegraphs signed a contract for the subvention of an extensive system of cables to connect their colonies in the West Indies with French Guiana, communicating at Cuba with the United States and Atlantic systems, and at Viseu, in lirazil, with the Brazilian lanrl lines to Rio and Buenos Ayres. A change of government led to the rejection of this contract in the Chamber of Deputies. Subsequently, however (between 1887 and 1888), a part of this scheme was carried out — as far as La Guayra, Venezuela. The cables were constructed by W. T. Henley's Telegraph Works Company,* who were also contractors for the laying of them. Mr R. E. I'eake (of Messrs Clark, Forde, and Taylor) executed the latter part of the contract for " Henley's," while Mr W. S. Seatc.i acted as engineer on behalf of the juoprietors, La Participation des Cahles des Antilles. In 1888 La SociETE Fran^aise des TelEgraphes Sous-Marins was formed, to take over the above cables and extend them as soon as the Chamber of Deputies should ratify their contracts made with various Ministers of Posts and Telegraphs. In 1889 the necessary ratification was obtained. Accordingly the .society proceeded to enter into contracts with the SociKTi: Generale des telephones for the construction in France of the said extension cables. The latter firm, which had previously made core only, for telephone and other purposes,! now (in 1891) set up cable- sheathing works at Calais. The cables were manufactured with complete success — partly by the Societe Fran(^aise des Telegraphes Sous-Marins and partly by the Henley Company — and were laid for the " Soci6te Fran^aise " by Mr W. S. Seaton between 1890 and 1891. * Half the required core, however, was made at the Hezons Works of La Societe (k'ncrale des Telephones. This was the first order that firm had obtained for submarine <::ihlo core, and it proved exceedingly satisfactory. + This well-known company — originally MM. Rattier ct Cie. — had been india-rubber and gutta-percha manufacturers, and had made and laid telephone lines ever since the commencement of practical telephony throughout Paris and other French towns. M. Mcnicr had also had rival works of the same description near Paris, but joined in with the ncwly-fornicd Telephone Company (La Societe Industrielle des Telephones), when that was established three years ago, his works being taken over by them. The " .Socidt^ Industrielle" constitutes the construction business of the former .Societe (lenerale, since the Government took over the exploitation part of the latter's concern. 138 SUBMARINE TKLKGRAPHS. It may here be noted that those last-mentioned cables went over some of the same ground as the old "Central American" Company's lines alrcidy referred to. It was not intended, however, that the French sj-stem should work in connection with the "Western and Brazilian" or the "Brazilian Submarine." By agreement its cable joins the Brazilian Government land lines for local traffic purposes, the European traffic going, as above mentioned, via the Western Union land lines and Atlantic cables. More- over, the French company may be said to work in opposition to the West India and Panama ; for its cables not only touch at the French islands, but at several of the others (both colonial and independent), for purposes of West Indian traffic generally. As stated before in connection with the first West Indian cables, the sea-bottom here is undoubtedly the worst over which any cables have yet had to be laid. In order to cope with this difficulty, the plan was adopted, in one case, of laying down quite a heavy type of cable — " shore-end," in fact — in the middle of some of the sections where coral reefs were known to exist ; and, in order to ensure of the heavy type being deposited in the right place, this part of the cable was laid first and then buoyed. The plan was naturally both a lengthy and a costly one, but it will be probably found to pay in the long-run. The main types of these cables were sheathed with rather stouter, and therefore more rigid wire than is usual. The object of this was to defeat the attacks of saw and sword fishes, which, as previously shewn, tend to make such havoc of cables in these shallow seas, as well as to anticipate the intrusive attentions of any possible teredo. The Halifax and Bermudas Caule Company was formed in 1889, to give effect to a contract with H.M. Government for laying a cable and maintaining telegraphic communication between the two important naval stations designated in its title. This contract has been, and is, carried out under a Government subsidy of twenty years' duration.* The manufacture and submersion of this cable were given to Henley's Company, on whose behalf Captain A. W. Stiffe (formerly of the late Indian Navy, and prominently connected with the first Persian Gulf cables) was engineer in charge of the expedition. It passes through water as deep as 2,824 fathoms, one of the greatest depths in which any cable is known to lie. * The concession had been in the first instance obtained by a company formed just before, and called the International Cable Company, who assigned it to its present holders. The International Company had attempted to float a more ambitious scheme — the same, in fiict, as that of the old " (ircat Western " Company— and had actually laid a shore end at Lisbon to save their concession. DEVELOPMENTS. 139 The object of this telegraphic connection was Imperial rather than commercial. It forms part of a scheme recommended by a Royal Com- mission in 1884 to provide a means of communication between the British West Indies and the Mother Country, passing entirely through British territory.* As the line connects up with several Anglo-Atlantic cables at Halifax, the direct communication demanded by the Commission has been effectually established. In 1 89 1 the French Government invited tenders for two cables to connect Marseilles with Oran and Tunis respectively. For the first time in the history of submarine telegraphy British contractors were excluded altogether. The Oran cable was allotted to La SociriTf. Generale des TiiLKPHONES, and the Tunis one to Mons. Grammont.+ The Oran cable (the core of which was turned out at Bezons, while the sheathing was applied at Calais) was laid by Mr W. S. Seaton on behalf of the French contractors, under the inspection of Mons. E. VV'unschendorff, the Government engineer, and author of the first complete work concerning submarine telegraphy (" Traite de Tclcgraphie Sous-Marine," Baudry et Cie, Paris), on a part of which this book is, to a great extent, based. M. Grammont retained the services of a civil engineer and compatriot, Mons. Peltier, for laying the Tunis cable. He chartered the Telegraph Construction Company's T.S. "Calabria" for this purpose, and availed himself of the assistance of some of the latter company's staff. For the manufacture of this cable, M. Grammont erected a factory (core and sheathing) at St Tropez, near Toulon. In 1891 the South American Cable Company was promoted by those interested in the Silvertown business (India-rubber, Gutta-percha, and Telegraph Works Company), the objects of which were to form an exten- sion of the Spanish National Company's system on the one hand, and, on the other, an alternative competing line for the Brazilo-European traffic. This was to be effected by means of a cable between Senegal, West Coast of Africa, and Brazil. The cable * was constructed and laid the following year by the Silver- town Company. It extends from St Louis, Senegal, to Pernambuco, ■* The completion of tliis scheme— by a newly-formed company associated with the above— is now about to be carried out by the line being extended from Bermuda to Jamaica, 7'tir Turk's Island. + M. Cirammont, it appears, had not done any work of this description before. His regular business was that of .i large contractor to the P'rench Army. I l'robal)ly one of the most perfect modern tvpes of cable for deep water ever designed, combining, as it did, the contractor's requirements for easy handling and laying, with the still more important owner's requirements for durability and maintenance. I40 SUISMARINK TELEGRAl'HS. Brazil, and touches at the island of I-'ernando de Noronha en route. The last section (about 350 N.M. in length) was furnished with india-rubber core instead of gutta-percha, the locality being considered a suitable one for giving india-rubber a fresh trial. The main part of this line passes through one of the greatest depths in which any cable actually rests, i.e., 2,830 fathoms, lat. 9 53' N., and long. 21 24' VV. At Pernambuco this company's A frico- American .system meets that of the " Western and Brazilian," and al.so that of the Brazilian Government land lines, thus gaining access (by agreement) to all the principal Brazilian towns as well as to the rest of the South American Continent. In 1893 the Europe and Azores Telegraph Company was established to effect telegraphic communication uctween Lisbon and the Azores group of islands. This company is worked on a subsidy from the Portuguese Government ; indeed, the cable is almost exclusively a Portu- guese national affair, the company simply acting as Government agents in the matter. It was laid for them by the Telegraph Construction Company in the same year, and connected two of the islands, Fayal and San Miguel, with one another and with Lisbon. La Soci^te Fran9ai.se des Tel^graphesSous-Marin.s* promoted in 1893 a scheme for a cable between Queensland and the P>ench colony of New Caledonia — di.stant some 8cX) miles odd — their primary object being to bring this island into telegraphic communication with France via the " Eastern " Company's .system. Ultimately they intended that it should become a first part of the thc.i proposed Franco-German Pacific Cable scheme. The contractors for the manufacture and submersion of this cable were La SocifnE Generale des Ti-XEphones. This firm had recently gathered together a staff of French engineers and electricians, and this was the first cable really laid by French hands. Mons. Rouillard was the engineer in charge of the expedition, Mr ICdward Stallibrass being al.so on board on behalf of Mr W. S. Seaton, who held a kind of " watching brief" as adviser to the contractors. , ' ' In the early part of 1895 the P"rcnch Government ordered a cable to be made and laid between Madagascar and Mozambique, from which point it would communicate with France and the rest of Europe via the ICastern and South African Company's system. This cable is entirely a State con- cern, being worked e.xclusively by, and on behalf of, the Government which ordered it. Half its length was made at the works of M. Grammont, and Now La Compagnie FRAN9AISE des Cables T]6li5:graphiques. DKVELOPMENTS. I4I half at the Calais works of the Telephone Company. It was laid by r.S. " Francjois Arago"of the latter firm, by M. Peltier, en^nneer to M. Grammont. In 1894 yet two more additions were made to the list of Atlantic cables — one on behalf of the Commercial Cable Company, and the other for the An^do-American Company. The new "Commercial " line was constructed and laid by Messrs Siemens Brothers, and the " An^io " cable by the Tele- <^rraph Construction Company.* Fig. 49 shews the type adopted for the deepest water of the latter. Full particulars concerning all the types of this cable will be found in Part II., with further reference to the core in Part III. Special arrangements were made in the design of both these cables to meet the requirements of increased speed. Since the successful application to submarine cabl'js of various modifica- tions of Wheatstone's automatic transmitter (intended only for land telegraphy),f the limit to the speed attainable only depends, practically speaking, upon Kk;. 49.— Angl»-Amcri- the type of cable employed. In a general way, there- '^"" Atlantic Cal)le fore, It will be readily understood that, if funds are Type, available at the time for the construction of one cable which will do the work of two, a notable economy is the result. \ On these principles, the core of the new Commercial cable was compo.sed of a ctjpper conductor weighing 500 lbs. per N.M., covered with a gutta-percha insulating sheath weighing 320 lbs. per N.M., while the new "Anglo" (see Fig. 49) has a core with conductor weighing 650 lbs. per N.M., and gutta-percha in.sulator * A detailed description of this cable was given in the course of an interesting article in The Electrician for 12th October 1894, and the full specification of it appears in Part II. of this work. It forms the fifth loorkiiiir cable of the "Anglo" Company. Their three first cables — of 1858, 1865, and 1866 — have been " dead " for some time, but the 1869 French cable has not yet been abandoned so far as simplex working is concerned, though not in operation at the moment of writing. t This instrument (following others of Hain and Siemens) was invented in its original form in 1859. It came into very general use on H.M. Post Office telegraphs. In 1879 MM. Belzand Brahic adapted the same principle to an instrument suited to the exigencies of submarine cable work ; this was followed by other modifications devised by Herbert Taylor (1888) and T. J. Wilmot (1890), besides more recent ones. All these varieties of the VVheatstone automatic transmitter will be found described and illustrated in Part 111., where the general principle of machine transmission and its advantages — alike in attainable speed and, from a " receiving " point of view, in the avoidance of the variable liiiman element of manual transmission — are also discussed. + A submarine cable system should, however, if it is to compete at all successfully, possess at least one spare " string to its bow " to provide against the contingency of a breakdown. 142 SUUMAKINK TKLEC.K.MMIS. 400 lbs. per N.M. * involving a completed cable (main type) nearly double the ueif^ht of previous corresponding^ lines. The actual speed obtained by automatic transini.ssion with the latter cable is as hi^h as forty-seven (or even up to fiftj'j five-letter words j^er minute.t On the previous lighter Atlantic cores twenty-five to twenty- eight words per minute was the usual maximum speed attainable ; the former, say, by average manual transmission and average receiving, and the latter by automatic transmission, other circumstances corres|jonding. With a cable in good condition, jiractically the same maximum speed can now be obtained working duplex as in working simplex. Duplex telegraphy, as applied to cables, has, in fact, been developed to such a pitch of perfection that, as previously stated, their carrying capacity is practically doubled by it. Atlantic Cable Systems. — As a part of the union between the Old World and the New, there are altogether fifteen cables at the bottom of the North Atlantic, which are usually termed " Atlantic cables." Out of the.se the first three are absolutely dead — as well as buried ; nine are in perfect condition for duplex working ; and three are, at the time of writing, rendering a fairly satisfactory account of themselves — with the help of occasional repairs — in simplex working. J In some cases the Atlantic companies have special cables of their own from the landing-place at the extreme south-west point of Ireland to points on the Continental coasts — those of France and Germany more particularly. These cables, as well as the European ends of the main .sections of the various Atlantic systems, may be seen in the map on the opposite page (Plate IX.).§ * The largest core hitherto made for submarine cables was composed of 400 lbs. copper conductor, and 400 lbs. j,'Utta-percha insulator. These were the core dimensions of the Malta-Alexandria cable of 1861, originally intended to connect up Falmouth and Gibraltar for the Government. This same type of core was also employed in the 1873 and 1874 "Anglo" Atlantics. Most of the Atlantic cores, however, had been smaller than this. + The corresponding maximum speed on the new " Commercial " cable is said to be two hundred letters, or about forty-two words, per minute, by automatic-machine transmission. + It may be mentioned here that if duplex be dispensed with {i.e., in simplex working), a cable behaves rather be/fcr with a small fault in it than when perfect. No cable, however, can be satisfactorily worked in duplex unless it is in perfect order; at least it is then only that anything like the full advantage of duplex working can be secured. S Both this and the following map are brought up to date from the last issued by the International Telegraph Bureau at Bern. They are ])urposcly reproduced in French, that being the language adopted by the Bureau and in the Telegraph Convention, besides still being the usual tongue in international matters. [I'LATK IX. 3 a. 5 \Toface p. 142. DEVELOI'MENTS. 143 Plate X. (see overleaf) suggests a somewhat complicated state of affairs at the other, or American, end of these lines, through their ever-increasing numbers. Some of these cabl-s, at each end of the corresponding main .section, contain more than one insulated conductor.* In the early pioneer days of ocean telegraphy, the Atlantic Telegraph Company t started with a mu::mum tariff of ;^20 for twenty words, and £i for t .ch additional word. This was first reduced to ;^io for twenty words, and was further altered later on to £s for ten words. After this it stood for a long time at a minimum of 30s. for ten words of five letters each. Subsequently, in 1867, the Anglo-American Company tried a word-rate of * One great danger to which cables in the North Atlantic are continually subject is the grounding of ice-floes, besides the wear and tear of rocks, near the shore. For this reason special methods are now adopted for the protection of the shore ends. In the last (1894) "Anglo" cable, the sheathing wires of the Irish shore end, besides being of great circumference, are applied with a very short lay (see Fig. 50), the object of this being to increase the weight of iron (within a given surface), thus reducing the chances of its being shifted, and avoiding abrasion. This plan obviates the necessity of an exceedingly large, and therefore rigid, type of wire being used for sheathing. Thp idea originated, it is believed, with Mr P. C. Dresing, the engineer to the "Great Northern" Company, who in 1892 designed such a cable for communication with a lighthouse off the Chinese coast, near Hong Kong. The section of a piece of cable, cutting through the wires thus laid up, gives them the appearance (as may be seen in the figure) of being elliptic. For further particulars, see Fart II. Lock-armoured cables have been devised by Messrs Felten and Guilleaume, as well as by others, with a similar object — i.e., that of introducing the greatest possible weight into a given limited area. Cables of this class are, however, more especially intended for rivers subject to strong currents. They are also largely used for underground purposes, as being an excellent means of contending with interruption from pick-axes or animal life. In the case of the new "Commercial," the shore ends are protected against the same danger by an armour consisting of some form of linked chain which is wound round them. At the Newfoundland end this is an especially desirable precaution, on account of the prevalence of ice. A few years ago Mr H. Kingsford suggested an ingenious system of alarm wires for the shore ends laid on doubtful bottoms. These insulated wires, embedded in the serving between the inner antl outer sheath, arc in circuit with an electric bell, which, being to earth, only comes into operation in the event of one of the wires becoming chafed. This would naturally occur some time before the main core was aflfected inside the inner sheathing. Moreover, the said alarm wires furnish the means of a loop test being taken to localise the precise position of the fault. Again, with such timely warning a local repair may be made without involving the engagenient of any repairing ship for the purpose. It also obviates the necessity of periodically underrunning the shore end — a practice open to several objections, besides that of expense. A plan like this may be the means of avoiding several weeks' interruption, and consequent loss of traffic. A full description and illustration of Mr Kingsford's device will be found in \.\\c Jflunuil of the Institution of Electrical Hni^inecrs, \ol. xix., p. 656. + The tariff universally in vogue up to that time was, in fact, based on the message rate common to land telegraphs — i.e., a charge was made on a message up to ten words, and so much for each additional word, depending upon its destination. 144 SUBMARINE TELEGRAPHS. £l for the 1865 and 1866 Atlantic cables; but it was net until 1872 that Mr Henry Weaver, their able manager, first instituted a regular word-rate system (without any minimum) of 4s. per word.* At the present time (1897), thanks to competition, to technical improvements in the plant, and to increased traffic, bringing in its train those economies in the working which are always possible in a larger scale of operations, the rate stands at IS. a word with all the Atlantic companies.f The twelve Atlantic cables now in use represent a total capital of something like i^ 1 7,000,000 ster- ling. A knowledge of the profits derived from each system is not readily to be arrived at ; but from a comparison of the traffic re- ceipts or "money returns" of the oldest existing Atlantic com- pany at different periods,* we are bound to conclude that the "takings" are, roughly speaking, very much the same now as they were twenty-five year.- ago. This is explainable by the fact that, although the number of mes- sages now passing is much greater, the reduction of the rate (with the ever-increasing competition of rival lines) just about cancels the advantage, so far as receipts are concerned. Kk;. 50. — Irish Shiire End of 1894 "Anglo" Atlantic. * (Ireat advantage was taken of this by the public, and the word-rate system was almost immediately taken up by the other cable systems — to wit, by the " Eastern " in 1872, on the opening of the Hritish-Australasian line. Though the number of messages conveyed at once enormously increased, it took some time for this increase to balance the effect of so large a proportion consisting of one or two words (chargeable only as such), as compared with the minimum ten-word tariff. In due course, however, as the use of the telegraph became more widely extended and appreciated, the increased numlier more than balani ed the decreaseil average length of messages ; and, ultimately, the introduction of the word-rate had the indirect effect of very materially adding to the earnings of not only the Atlantic, but of all cable systems, + The shilling rate was first permanently adopted (down to the present, at any r.ate) by all the companies in 1888. Hefore that year competition had certainly had the etTect from time to time of bringing the rates down to is., and even to 6d., for a few weeks or months at a stretch ; but ur'il 1888 they hati invariably returned to their former figures, or something similar. J The .•\tlantic and .-\nglo-Ainer'can Telegraph Companies were not actually amal- gamated \m\\\ 1873. When the " Aiij.l.i-American "Company was promoted, in iS66,itwas for the purpose of securing fresh ca[.ital io complete the work undertaken and started by the .'Vtlantic Company. From that date until 1873 the two companies wt)rked togetlier as [Plate X. [Tofacef. 144. DEVELOPMKNTS. 1 45 General Retrospect. — The reader has now been given an opportunity of surveying the whole, or at least the most important parts, of the vast network of submarine telegraphic systems with which the world is at present endowed. It is, of course, the original cables only, which first opened up telegraphic communication with the various countries, that have been most fully noticed, subsequent duplications being sometimes referred to, but not dwelt on in detail. As already mentioned, the important trunk-lines to the East and Far East have been more than duplicated, besides many of the branch and independent cables. Two distinct lines, one of which is duplicated, now unite F.urope (directly) with the South American continent and all its branch lines, thus indirectly giving additional lines of communication with the West Indies and North .America. They also communicate with the Vv''est Coast of Africa, and via this branch with the Cape. The folding map at the end of this Part gives an up-to-date idea of the main general telegraphic systems of the world — the network of its " electric nerves." This map indicates not only the original cables, but all their duplications and multiplications.* It is arranged in the way it is in order to shew more clearly the principal gap that is still open for repletion. t A noteworthy void is observable in the North Atlantic, between the Azores and Bermuda, which, if filled up, would constitute another Atlantic cable, and thus an additional telegraphic highway between Europe, on the one hand, and the United States and Canada on the other. A still greater blank occurs between Mauritius and the West Coast of Australia, which might profitably be made good, so as to create an extra line to Australia. Another useful extension would be that of the Central and South .American cables up to San Francisco. one, sharing profits as soon as there were any to share. At the same time as this arrangement was eflfected, the "Anglo" Company entirely took over the New York, New- foundland, and London Telegraph Comjjany, with which the "Anglo" cables had previously been working in connection. * Though, at the moment of writing, the " Halifax and Bermudas " Company's extension between Bermuda and Jamaica is not actually laid, from a statement of Mr Joseph Rippon (the general manager), there can be no doubt that it will be within a very short time of the publication of this volume. + This is a specially prepared map, and the /ini;itti franca has not here been adhered to, on the grounds that by far the greater part of the world's cables are English —made, laid, and worked by English hands— stretching in all directions to British terri- tories and dependencies. CHAPTER I\'. MISCELLANEOUS AND COMMERCIAL RESUME. Section i. — The Proposed Trans- Pacific Line : Engineering Problems : Financial Pros- pects : Tariff": Political Utility : National, Imperial, and Strategic Aspects. Section 2. — Total Length of Cable Submerged and Monetary Equivalent as compared with Land Telegraphs of the World. Section 3. — Engineers and Contractors — Bright and Clark : Gisborne and Forde : Thomson and Jenkin : Canning and Sauine: Clark, Forde, and Taylor — R. S. Newall and Co.: Glass, Elliot, and Co. : Telegraph Construction and Maintenance Company: Siemens and Halske; .Siemens Brothers: .S. W. .Silver and Co. : India-rubber, Gutta- percha, and Telegraph Works Company : Mr W. T. Henley : The Hooper Com- pany — Johnson and Phillips-Elliott Brothers. Section 4.— Telegraph Ships— "Silvertown" : "Faraday": ".Scotia." Section 5. — Miscellaneous F'gures and Estimates-- Initial Cost and Life of a Cable — Maintenance — Renewal Fund- -Repairs and Duplications — Number of Messages Conveyed — Time occupied now and previously -Code Messages — Earning Capacity — Revenue — Value as an Investment — Submarine Telegraphs opening up a Country— "Eastern" and Allied Companies' Jubilee and Retrospect. Section 6. — Comparative Effects of Railways and Telegraphs on Civilisation — Revolu- tion in Methods of Diplomacy — Strategic .Standpoint — Influence on Commerce — Difference of Time limiting the Hours of Communication with Distant Points — English Financial Pioneers — Mr Henniker Heaton's Proposed Reforms — Influence on the Press : Dissemination of News in times of War, etc. Section 7. — Business Systems — Codes : Effect on Number and Length of Messages — International Administration : Bern Bureau — Subjects for Consideration : Landing Rights : Shore-End Protection — Official Telegraph Map — Great Safety of Cables in Deep Water. Section 8. — Founders of the Society of Telegraph Engineers — Early Papers concerning Submarine Telegraphy — Institution of Civil Engineers — Institution of Mechanical Engineers — Early Articles in the Tchxrdphic Journal and T/ic Ekttiicinii. Section 9. — Inductive Telegraphy— Past and Future. Section i.— Main Communications: Present and P'uture. Pacific Cable Projects.— How soon the greatest gap of all, namely, that across the Pacific Ocean, will be spanned by a telegraph cable,* it would be out of place to predict.t If, however, the present long peace ■•■■ When spoken of in the light of a direct line across the Pacific, from San Francisco to Japan and China, this is sometimes described as the "missing link "of the earth's girdle. + Since the above lines were written, the .Secretary of State for the Colonies (the Right Hon. Joseph Chamberlain, M.P.) has called together a conference at the Colonial Office to go into the question of an All-British Pacific Cable from every aspect. Over MISCELLANEOUS AND COMMERCIAL RfiSUMfi. I47 between the great Powers of the world is not broken, there is no reason in the nature of things why this big enterprise should be much longer delayetl. It is difficult to foresee any insurmountable engineering diffi- culties in its way, albeit the ground has been only partially sounded over at present. Along one or two of the proposed routes it is true that depths have been found* which exceed, by some 700 fathoms,+ those in which any cable has hitherto been laid.* This, of course, would necessitate the construction of a well-adapted tyjje of cable, as well as of suitable machinery for paying out and— in view of what must be called the usual eventualities— for picking up the same.§ Hut such matters will certainly not daunt any telegraph engineer or contractor worth his salt. i| On the electrical side, again, it has been asserted that if the Pacific line tills the Under-Secretary of State (Lord Selborne) presided, and he was assisted in his investigation by various important colonial oflFicials, as well as by the engineer-in-chief to H.,NL Post Office and consulting engineer to the Colonies (Mr W. H. Freece, C.B., F.R.S.). .A number of experts were called to give evidence, and a report on the whole in favour of the project was duly arrived at. This affair occupied from June 1896 to January 1897, Mr W. Hepworth Mercer, of the Colonial Office, acting as Secretary. * Associated, moreover, with deposits of which no practical experience has been gained. t Though the Atlantic runs the Pacific pretty close, the deepest sounding yet recorded was taken last year (1896) by H.M.S. "Penguin" about 550 miles north-west of New Zealand. This gave 5,155 fathoms— or a depth of nearly six miles — but the proposed line would not, under any circumstances, require to go immediately into this region. In these great depths the bottom is so soft that great diffi'"ulty is experienced in determining when the lead actually touches the bed of the ocean. Thus it sometimes happens that the depth registered is far in excess of what it should be, owing to the wire continuing to run out and coil itself down after reaching bottom. These remarks refer especially to depths over 2,500 fathoms, where, on account of the great length of line, the jump is less easily observed. The Halifax and Bermudas cable, in approaching Bermuda, runs into over 2,800 fathoms, as does also the South American Company's line, and one of the lines spanning the North Atlantic ; moreover, the Brazilian Submarine cable was laid in over 2,700 fathoms. \ Again, on what is the favourite route from a national point of view, the longest section would run into some 3,500 N.M., as against 2,717 for the longest existing section — across the North .\tlantic between Brest and St Pierre. This, however, would introduce no very serious difficulties. S It has been urged by those who are opposed to the scheme that recovery would be an extremely lengthy — if not impossible— task. Regard must, however, be had for the fact that the Direct Spanish Company's cable hrfs been picked up and repaired in some- thing like 2,000 fathoms within the course of two or three days, not to mention other repairs in much greater depths (upwards of 2,700 fathoms), though taking longer. II Forty years ago the feasibility of Atlantic Telegraphy was the subject of similar incredulity at the hands of many of the greatest authorities until the cable was actually laid and worked in 1S58. In that instance there was practically no data to go upon, whereas the jiroposcd Pacific line may be regarded as but a further extension of what has already been done, though certainly involving special arrangements and precautions. 148 SUBMARINE TELKClKAl'llS. were laid it would not work satisfactorily. This suggestion is not, how- ever, in agreement with facts ; though it is true that the maximum speed obtainable on the long section of the All-British route (say 3,500 N.M.), with quite a large core, would be low as compared with that attained on the Atlantic cables, which are, of necessity, kept heavil}- burdened with traffic more or less continuouslj'. Still, with a core of the same pro- portions as that adopted in the " Anglo " Company's last cable, a speed could be obtained well up to the minimum required b)' the Canadian Government in 1894. The foregoing would be by ordinary manual trans- mission, whereas all the latest improvements in machine transmission with curbing arrangements (as well as condensers) would naturally be applied with something like 30 per cent, increase in the speed — quite apart from the application of the duplex system.* The more doubtful question, however, is whether the line could be made a commercial success ; whether, in fact — even within the next quarter of a century, much more within the next ten years — .such an expensive enterprise could be made to pay. Although it is upon the.se commercial, as well as what may be called quasi-political (Imperial, Anglo- Australo- American, " Pan-Britannic ") considerations, that its fate depends, rather than upon any advances in the art of submarine telegraph engineering, some account of what has been said and done in the matter ma)- not be amiss here. The scheme has been considered and discussed by many able authorities for a long time. Thus it is now twenty-seven years since (in 1870) a devious sort of trans- Pacific cable was first proposed by the late Mr Cyrus Field and other American capitalists, who endeavoured to negotiate financial arrangements for the purpose. Their plan was to connect Cali- fornia with China via Alaska and Japan, but it had to be abandoned. f * As a first venture the above cable would probably be sufficient to meet the ends in view. It is conceivable that a larger core would be out of the question on the ground of cost. Moreover, increase in the dimensions beyond this would have the effect of farther augmenting the mechanical difficulties as regards a suitable type of cable to enclose the required minimum thickness of jute packing. E.xperiments have already been made on two Atlantic cables looped together to test this point of the possibility of working through a considerably greater length than that to be dealt with in the longest section here, the results being perfectly satisfactory. t IJy one of the schemes the total length of submarine cable required would only be about 750 miles. This was by a line across the Behring Sea touching at various islands of the Aleutian group (about a hundred in all) on the way. Most of the sections would thus be in quite shallow water — say 30 fathoms— but some might have had to go into very great depths in certain places, near some of the islands. The Hehring .Straits would have still further reduced the length of cable involved to but little over 50 miles, indeed. This route, however, was debarred partly on account of the presence of ice and snow together with the absence of soundings by sea, but also owing to it being an imprac- ticable route on each side for the erection or maintenance of any land lines. MISCELLANEOUS AND COMMERCIAL KLSUML. 149 Since that time the Pacific idea has been further developed in this country, and from a national rather than a private commercial point of view. The various routes which have found most favour in the English mind are those which provide in the first place for communication between Hritish Columbia and Australia, with resting-places at one or another of the groups of islands mid-ocean. H.M. Government and the Colonial Govern- ments most concerned have been urged, from time to time, to consider the matter in its naval and strategic aspects. Two Colonial Conferences (in 1887 and 1894) were largely occupied with this subject, as may be gathered from perusal of the bulky Hluebooks which record their i^roceedings. The Dominion Government took the matter up quite strenuously in 1893-94, and invited the various contracting firms to send in estimates for con- struction and laying, under condition of forming a company for working and maintaining the cable. Subsequently Lord Jersey, in the course of a long report on the Ottawa Conference,* strongly recommended the Home Government to take further steps, and to order a series of soundings to be taken on the various suggested routes. The proposed tariff rate from I'^urope to Australia via the projected Pacific cables was 3s. a word. In view, however, of the losses said to have resulted from the recent reduction of tariff on the existing system, some authorities have expressed doubts whether such a comparatively low tariff could be rendered profitable.f This consideration raises the whole question whether the existing service via India J does not meet all the practical re- * Report on "The Colonial Conference at Ottawa," 1894, to Right Hon. the Marquis of Ripon, P.C., K.G., Secretary of State for the Colonies, by the Right Hon. the Earl of Jersey, P.C, G.C.M.G., Chairman of the Colonial Conference at Ottawa, appointed Delegate to represent the Imperial Government. + Cheap tariff experiments have not been encouraging to the existing companies. The rate between Europe and Australia was reduced in 1891, under a Government arrangement between the Colonies and the Eastern Extension Telegraph Company, from 9s. 4d. to 4s. per word, which is said to have resulted in a heavy loss to the company. The Colonies then arranged for an increase to 4s. yd., and this, with abnormally favour- able circumstances, has considerably reduced the loss. Similarly, the reduction of the New Zealand cable tariff in 1893 from 8s. 6d. (and previously los. 6d.) to 2s. per word, resulted in a loss of nearly 60 per cent, of revenue. The rate at present stands at 5s. 2d. In any original agreement between a cable company and a (Government, it is now always stipulated that the Government shall take upon its shoulders a certain proportion of the loss resulting from any abatements of tariff which may be insisted upon in any future international telegraph conventions to which the said Government may be a party. The highest existing cable-rate from England is that to Colombia (South America), which is still about 27s. per word, and the next highest that to Peru, at about 22s. I By this service, provided by the " Eastern " and its allied companies, Australia and New Zealand, as well as India, are placed in communication with North .America, not only via Europe, but (if necessary) via the Cape, West Africa, and South America. The further extensions of the great Eastern trunk-line also connect all these countries tele- 1-50 SUBMARINK TKLEdKAPHS. quiremeiits of the case at present. It sliould be remembered that by this route messages from AustraHa to America only take a few minutes longer in transmission than those which stop short at Great Britain. This service, passing, as it does, over cables entirely duplicated, and in part triplicated, cannot be considered liable to interruption by any of the ordinary " accidents of cable life." There is, however, one contingency — and a very serious one — in which this extremely undesirable eventuality might occur. In the event of a great war* between this country and another naval Power, or l'owers,+ it is quite conceivable that more than one of our Mediterranean cables (if no others) might he ruthlessly cut by the enemy, J and our communications with Egypt, India, and other Kastern and Australasian stations entirely broken off.§ Not only can the cable be cut in shallow water near the coast by an}' small steamer with purchase gear that will raise an anchor, but lengths be removed in a manner that would ta.x the resources of a repairing vessel to graphically with China and Jajian. In fact, it will be seen, by referring to the Telegraph Map, that China, Japan, and om- East Indian and Australasian colonies and depen- dencies, possess already — apart from duplications -at least three alternative lines of com- munication with the United States and Canada. These are — (i) The Eastern, Eastern E.xtension, etc., cables to India and Euiope (to England via Continental land lines, or via Ciibraltar, etc.), and the Atlantics thence to America ; (2) the Great Northern cables and land lines from China to Europe, via Siberia and Russia, in connection with the Atlantic cables as above ; (3) the above-mentioned Cape route from India, via West Africa and South America. * Mr C. Scott Snell has lately endeavoured to meet this by what he terms a cable defence scheme — i.e.., a plan for paying out cables rapidly from a man-of-war to any desired spot to take the place temporarily of an interrupted cable, or to establish communication for the moment between any two spots, or to an outlying station, hitherto unconnected. This scheme is referred to further elsewhere. t The present lines to India and Australia are as follows : — {(i) Lisbon, Gibraltar, Malta, Egypt, and the Red Sea ; {b) France, Italy, Greece, Egypt, and Red Sea ; {c) Germany, Austria, Turkey, Russia, and the Pacific Coast ; (-, and converted into a telegraph ship in i879,t the first piece of cable work she did being the la\ing of the cable between Malacca and .Singapore in 1S79. She has since laid a considerably greater length of cable than any other single telegraph ship, amounting to upwards of 25,000 N.M. Like her companions, the ".Seine" and the " Britannia," .she is a very hand.some ves.sel to look at — ornamental as well as useful. As the " .Silvertown " has the greatest beam (and mainly for this reason the greatest carrying capacit)-), so the " Scotia " has the greatest length, her dimensions being — length, 379 feet ; beam, 48 feet ; and depth of hold, 38 feet. SECTION 5.— MiSCKLL.VNEOUS FIGURES .\M) ICSTIM.XTE.S. Cost of Construction and Laying. — The cost of a submarine telegraph cable to its purchaser (taking the average proportion of the different types usually employed) may nowadays be roughly estimated at ^150 per N.M. The greater the proportion of core, and the larger this core is, the heavier, of course, will be the expense of the entire cable. :J: The cost of its submersion — presuming average luck as to prevailing con- ditions and contingencies — may generally be roughly estimated at about half as much again as that of its construction.^ Life of a Cable. — Unfortunately, however, even though perfectly free * The " F.nraclay " was, in fact, one of the fust twin-sciew ships biiih. + The "Scotia'' was originally a packile-boat, but for deep-water cable purposes it was necessary to convert her into a screw shi])— a performance at that time regarded as a rather remarkal)le piece of marine engineering skill. \ Cable for submarine telegraph purposes has been supplied at as low a figure as ^50 a mile. S A cable costs between five and seven times as much as a land line, and the total cost of its construction and submersion comes to between seven and eight times that of the erection (including original cost of wires, posts, etc.) of the aerial wire. 164 SUBMARINE TEI.KGRAl'IIS. from electrical faults when laid, no submarine cable will last for ever. No very precise limit can at present be assigned to the longevity of a cable of suitable type, carefully manufactured, and laid on the bottom and in the waters for which it was designed.* The history of submarine telegraphy is scarcely long enough to arrive at any very definite conclusions upon this point. All that can be said is that in cases where a cable has not been subjected to casual sources of detriment (such as ships' anchors, rocks, sharks, saw and sword t fish, teredoes, and other "common objects"* of the deep sea in different latitudes §), the records of cable existence have, of late years, been distinctly satisfactory. j| Several portions of the early lines laid in shallow water — between England and its neighbouring countries — from iany at East Greenwich, on 14th August 1896. On this occasion c ur distinguished guest had pre-arranged a series of lengthy cipher-code messages to Shanghai and elsewhere — in one instance addre.s.sed to S/um S/iiiii )'aii Sltea iVa/t, almost a message in itself! These tele- graphic despatches were no light reading, but Li was in a position to coo with |jride and pleasure when he realised that he had sent a message i2,6oS miies,f and had received an answer within seven minutes ! :^ M Opening (jf I.ine. At Present Day 5 to 6 hours. 30 minutes. 9 to 10 '5 3 to 4 20 5 35 8 80 10 100 8 -5 10 60 10 70 10 80 * A quarter of a century ago it was considered wonderful to receive a message from India in a few hours. Now the same message would only take a few minutes. The tariff, moreover, at that time stood for Bombay at /4 los. for a minimum of twenty words, and proportionately for every e.>;tra word. Now it is 4s. per word without any minimum stipulation. .Similai'moditications have taken place elsewhere. t It may be mentioned further that the message in question consisted of sixty-eight words, and that it was despatched in two and a half minutes ! Wc must, howe\er, remember that, both in this instance and in that of the Silver Jubilee Celebration of the Eastern Telegraph Company in 1894, every possible arrangement had been made before- hand to facilitate operations by Mr T. A. Bullock, Superintendent of the "Eastern" Company's London Stations. \ Another striking case of uji-to-datc telegraphy subaqueous if not submarine - is the manner in which the evening newspapers in London are able to report the various stages of the Uni\ersity Boat Race whilst it is |)rocceding. This is brought about by the Press Steamboat paying out an insulated wire (connected to a receiving instrument ashore) as she follows the boats, having an operator on board who manipulates tlic sending ke) whilst observing tlie various incidents of the race Thus the result can be fdled in at the different Fleet .Street offices within a second or two after - or /'(yjm' -the winner has passed the |)ost I ^'et another e.-;amplc of the kinrl is the recent Parliamentary Chess Match between the House of Commons and the United States House of Representatives. This MISCKLLANEOUS AM) COMMERCIAL RKSUMK. 169 Section 6. — Iueect oe SuBxMARine TELEORArin on the World's I'rocress. Social and Political Influences. — The great revolution which sub- marine telegrapliy has effected in the world's progress (its rate and its nature) may be regarded from two main standpoints, the politic;d and the commercial. Let us commence with the former.* In the first place, then, it has accelerated — even more perhaps than the im- provements in locomotion by land and sea — what may be called the practical shrinkage of the globe. The nations and peoples of the world, being in continual contact with each other through the telegraph and its powerful ally the l'ress,+ know one another, and understand one another's actions, thoughts, and national aspirations, infinitely better than they did thirty or forty years ago. The effect of this better knowledge and insight upon their mutual relations may not always, in the first instance, be a happy one : there is certainly a seamy side to it, so far as the commercial ascendency of this country is concerned — teste the manner in which the Germans have been stealing our industrial thunder (and sometimes improving upon it) during the last two decades. The rapid rise of Japanese competition in the East is another case in point.:J: Eut if the whole world gains, as it undoubtedly docs, by closer contact and the lessons which one nation is thereby induced to learn from another, we need not take very seriously to heart any relative — and may be, after all, quite temporary — decrease of ascendency in two or three departments of our national activities. Such " ups and downs " are the necessary incidents of social and industrial progress all the world over ; we have had plenty of them in this country in tlie past, so must make up our minds to bear patiently with them in the match uas played over the cal)les and land systems of the "Anglo' ('onipany and the "Western Union" Company. The smartest piece of transmission done during the play was London to Washinjjton and back— a distance of 8,360 miles— in 13] seconds. * Notwithstandini; that a iarj^e |)roportion of the line is submarine, Dublin can now, by machine transmission, communicate with London at the rate of about 500 words per minute a fact which somewhat discounts one at least of the stock arguments which used to be brought forward in favour of Home Rule for Ireland. \ Instances of the indebtedness of modern journalistic enterprise, for some of the strongest and most pit|uant fooil that it thrives upon, to the telegraph cable are given further on in connection with the 'ommercial results of submarine telegraphy. It may safely be averred that without it the foundations of certain great newspaper fortunes could never have been laid. + Can it be a mere coincidence that the same quarter of a century which has witnessetl the phenomenal rise of Japan from the position of an insignificant Oriental nation to that of one of the (compar,ili\{ly groat) I'owers of the modern world is also the period which has marked the completion and consolidations of the cable systems uniting the Far East with India and Europe? I/O SUllMAKINK ti-:le(;rai'hs. present and to profit from them in the future. We may e\en >ct have to pass through the fire of much t^reater tribulations and humiliations before we achieve our national destiny, but we shall not have the telegiaph or any other modern instrument of progress to blame for that. Meanwhile there is at least one political result of this great development of the world's system of electric nerves, which Englishmen may safely regard with unmixed satisfaction and pleasure. This is the much closer relations which have thereby been rendered possible — nay, are on their way towards being fully established — between the mother-countries of the United Kingdom and the daughter-nations, luiglish-speaking, English- modelled (as to their institutions), and, in the main, of liritish and Irish stock, which have sprung up in the most distant quarters of the world. The " Little England " idea, so fondly cherished by the old Manchester school of economists and politicians (who would gladly have .seen all our young and vigorous Anglo-Celtic brcjod chased, as young birds from the parent nest, almost before they could fly), is practically as dead as a door nail. In its place, we hear on ah sides of Imperial Federation and Inter- Colonial Federation schemes, of a I'an-Britannic Zollvercin or Customs Union between the United Kingdom, its self-governing colonies, and India, and — grander, if less practicable, than all these — we now hear of negotia- tions for the establishment of a permanent arbitration tribunal for settling peacefully all future differences between the two main divisions of the English-speaking world. These movements may end in some form of British Imperial Federation, accompanied with a permanent niodus vivendi with the United States. They may even lead, bcyiMid this, to the con- stitution of a new nation, on a grander scale than any which the world has yet seen — a true Pan-Anglican Federation — embracing all the "free" com- munities in different parts of the world which, albeit of diverse races and even colours, are naturally united by the common bonds of the English language as their official and most prevalent tongue, and of religious and political institutions of l^uropean and mainly Briti.sh origin. In a work like this, partly written for the rising generation of telegraphists in all these countries, from the United Kingdom, and its great "emancipated daughter" the United States, down to the smallest African and West Indian com- munities speaking and reading our modern lingua franca, it does not seem (jut of place to refer to such possibilities — especially as the extension of submarine telegraphy is doing more, perhaps, than any other single move- ment in the world to render their e^'cntual realisation possible. To discuss them at greater length would, of course, be quite outside our province. Influence on Diplomacy. — Another department in which submarine MISCELLANEOUS AND COMMERCIAL UESUMf:. I/I cables have produced a notable political effect, is the diplomatic. If the peoples have been brought more in touch with each other, so also have their rulers and statesmen. An entirely new and muchly-imjjroved method of conducting the dij^lomatic relations between one country and another has come into use with the telegraph wire and cable. The facility and rapidity with which one Government is now enabled to know the "mind" — or, at any rate, the professed mind — of another, has often been the means of averting diplomatic ruptures and consequent wars during the last few decades. At first sight, the contrary result might have been anticijmted ; * but, on the whole, experience distinctly pronounces in favour of the pacific eifects of telegra])hy. The most obvious risk, perl ips, in submarine telegraphy to a nation like Great Britain,+ who.se colonies and posse.ssion.s — with the naval and militar}' forces for their protection — arc distributed over every quarter of the globe, is that her (iovcrnmcnt may, at one moment or another, Uati too much upon this valuable means of rapid communication. In the event of a surprise war — carefully |)rc-arranged — declared against us by another naval Power, or of a well-prepared revolution in one of our colonies or dependencies, the inconvenience of suddenly-cut cables might conceivably take the Home authorities unawares. * On the subject of cable-cutting and of the value of International Telegraph Conventions more is said further on (sec pp. 150, 151, al.so p. 179). Influence on Commerce. — Let us now turn to tlie commercial results of these great developments of submarine telegraphy. The.se have been jjartly anticipated in describing certain improvements in tariffs and speed of trans- mission, and altogether the subject is so vast, .so complicated, and so far- reaching, that to attempt a detailed, or sjstematic, account of it within the compass of a work like the present, wouid be but presumptuous. The fact is, the methods of conducting business between merchants and financiers in different countries have been completel)' revolutionised by the telegraph cable, which places the business man in touch with the money markets of the world. This is so patent and obvious to the older generation of business men now living, that it is the \'ounger only that need reminding of it. Thus, fifty jears ago it took a London or Liverpool merchant si.\ months to get an answer to a letter addre.s.sed to a correspondent at Calcutta, and * liulccd, it cannot be denied that there arc occasions when rapidity in the inter- change of diplomatic communications may have liad- aye, and may still have— the effect of prcuhicing ruptures which "a little more time to think" would have avoided. t No other country can be said to possess such long, or acute, cars as John liull. X As might also indeed the temporary stoppage of telegraphic communication hctweun two or more important parts of our empire by an enemy effecting a successful lOuft ife main upon a station (or cable-end) in tlie main line of communication. 172 SUUMARINM". TKl.KClRAl'IIS. complete a ]jiece of business : no\vad.'i)-s, by means of the telegraph, the same transaction can be effected within si\ hours. Another result of the change of conditions brought about by the wire and cable is the partial elimination of the middle-man in some departments of international com- merce. This, again, is an item in the general revolution which can onl\- be referred to, the discussion of it in detail being c]uite beyond our present scope. It should be noted, however, that the phenomena of w iiat may be called the telegrapho-commercial revolution are by no means the same between different trade-centres at equal telegraphic distances from each other. Longitude is, of necessity, a powerful factor in the matter:* so are the political, religious, educational, linguistic, and other circumstances, which in one case may facilitate, in another impede, the rapid development of trade under the new conditions. Thus, the previously existing com- mercial ties between Buenos Ayres, Cape Town — na)-, even Yokohama — and London might be drawn (and, as a matter of fact, have been drawn) closer by means of the telegraph than those between Constantinople and London. The total imports of the world amount to over 1,900 millions sterling. As the late Sir John Pender has put it,+ "considering that commercial operations are now begun and ended by means of the telegraph, it will be seen that these vast figures have an important bearing upon submarine telegraphy." The converse is, ofcour.se, equally true and important. Upon the progress of submarine telegraphy in the future as in the past, a great deal of the world's commercial and industrial progress must depend. And not only the progress of the whole world cf)llecti\ely, but the relative importance and mutual relationship of certain parts of it. The constant extension and duplication of the cables and land lines themselves, the fact that these communications have been effected chiefly by English- men, and retained for the most part in British and American hands, the great reductions made in tariffs, the improvements in speed and volume of telegraphic traffic (due to the successful application of the duplex system to cables, as well as various improvements in instruments, etc., already * Owing to the differenrt' in time between certiiin important centres, it is impossible for merchants in the one to obtain a reply on the same clay to their messages cles|)atchect in the morning to the other. To use a familiar bit of slang, their business hours don't "gee." Even in the case of London and New York, notwithstanding the important negotiations constantly proceeding between them, there is onl>' about one hours simul- taneous session of their two .Stock Exchanges. This means smart work for the operators, as an enormous traffic (in this and similar cases) has to be concentrated into a few minutes of time. Obviously where longitude is not a barrier (<•.,«,'., between London and Paris or Lyons) 'C(\q possibilities created by the telegraph are relati\ely greater. + .Sec his speech at the Imperial Institute, while presiding over the bancpiet above referrt-d to, hold in celebration of the twenty-fifth anniversary of the completion of the " Eastern Company's" first cables to India. MISCKLLANliOUS AND COMMKKCIAL RKSUMK. 173 referred to), and finall}- the new system of code and cipher signalling — all these developments may be continued, nay supplemented, by others in the immediate future. But how and by whom this is to be done ; more especially whether chiefly by men of our race or institutions,* and in the interests of— or, at least, not to the detriment of— the continued growth of harmony and union in the English-speaking world ; all this depends upon the private enterprise, as well as the political wisdom and decision of purpose, of the present generation. Proposed Reforms. — Mr J. Henniker Heaton, M.F., has of late years been almost as indefatigable in his efforts to bring about a uniform reduction of rates for cablegrams to our Colonies and the United States, as in his earlier scheme for a universal penny postage. .So far these efforts have not culminated in anything practical, but his day may yet come.f It must be remembered that the present (much varying) word- rate system itself did not come into universal and permanent use until after the St Petersburg Convention (of the International Telegraphic Conference), hereafter referred to, which took place in 1875. The adoption of a word-rate was then definitely agreed to by all the Government tele- graph departments and all the companies represented there. ;J: Dissemination of News by Submarine Cables. — Before leaving the subject of the world-wide effects of submarine telegraphy during the present generation, one important class of them should be especially referred to, which is both political and commercial. This is the phenomenally rapid * Let it not be supposed that it is intended in this book to deprecate the growth of French, Italian, Spanish, Japanese, or any other foreign enter|)rise in suljniarine tclej,naphy. Quite the contrary. Whether we call ourselves Englishmen, Americans, .\iistralians, or what not, we shall prosper none the less, or the slower, because our iiciglibours -because the whole world in fact— arc "moving."' Therefore, by all means let every nation that wishes and is able to develop its own cable systems, anil train up its own army of telegraph engineers and electricians, do so with our very best wishes. .Ml that it is our business to see to is, that li'c at least don't lag behind. And if any ring- fence (Of preferential rates or other pri\ileges) is to be established, let us make sure that those admitted within it are also those who by kinship, conununity of language, or historical association, can be expected to gel on well and harmoniously together both with ourselves and with each other. t Mr Heaton has also recently urged the desirability of our cable system coming under .State control, mainly on the grounds that if the Ciovernment takes over the working of the system, the rates could be reduced to half what they are at present, whilst the telegraph would, in his opinion, still remain a paying concern. The time may, of course, occur when there will be one rate on all telegraphs— whether land or submarine -throughout the world. I Regarding the earlier history of the evolution of the word-rate, see pp. 143, 144. Its introduction was no doubt largely ijrouglU about by the '"packing" of messages by Router's Agency, their custom being to pack sever.d caijlegrams into one, thus enabling the public to economically send any less number than that corresponding to the company's minimum tariff. 174 SUHMARINE TKLE(;KA1'I1S. dissemination in all quarters of the world of war and other sensational news. In old times it sometimes happened that battles were fought in ignorance of the fact that a treaty of peace had already been formally signed between the contending parties — sometimes long after it. Now, thanks to the telegraph, such dreadful mistakes would be impossible. The influence of this early news upon the policies of nations and the financial and commercial operations of individuals, upon the fortunes — indeed, the very existence — of a great portion of the dailj- press of modern times, is incalculable. Thus, during the Afghan campaigns of iS/H, 1879, and 1880, the Indian authorities and our own made large use of the telegraph cable and wires, thereby incidentally enabling the public at home to read full details of every action almost as soon as it took place. On the other hand, the disaster of Isandula, South Africa, in January 1879, was not known in this country until some weeks after, owing to the absence of telegraph communication. This probably did more than any other single event to advance the negotiations for establishing a submarine cable to the Cape. In 1881 all the negotiations with the Transvaal were conducted througii the telegraph. By this means the British Government was in hourly communi- cation with the Boer leaders, and the unfortunate dispute was settled — as it certainly would not have been otherwise — without further recourse to arms. A still more signal instance of the value and capabilities of the telegraph in war occurred at the bombardment of Ale.vandria. During this operation the Alexandria end of one of the cables was taken on board the Eastern Tele- graph Company's S..S. " Chiltern," and the progress of the destruction of the forts wired to London from minute to minute. The military operations which followed in Egypt, and in the subsequent campaign in the Soudan, were announced at home with the same wonderful despatch, telegrams being sent off direct from the battlefield at ever)- stage of the proceedings. More recent evei\ts have afforded, and are at the time of writing affording, fresh illustrations of the great boon conferred upon us by the telegraph under the able administration of the " Eastern " and other services.* * In connection with iIil- i|iiite recent (i8g6) trouble in tlie Transvaal, there can be little doubt that but for the telegraph, .South .African affairs would be in a worse way than they arc, for then Mr Chamberlain would ha\e been unable at the rij^ht inouicnt to explain that the famous but lamentable "Jameson Kaid " on Johannesburg had been arranged entirely without the authority, or knowledge, of Her Majesty's (Government. About this time the two cable systems clown the East and West Coast of Africa were each in turn subject to interruption. Hut for the happy chance that their breakdown was not simultaneous, our understandings with President Kriiger might have been less satis- factory. All this ])oints to the desirability of having direct communication with South Africa — independent of the existing lines touching at a number of foreign colonies en route. 1 1 is understood that, with commendable foresight, the Eastern and South African Company, recognising this necessity, are about to institute such a system. miscellankous and comm i'.kciai. kksumf.. 1/5 Skction 7. — Business Systems and Administration. Code and Cipher Messages. — As has already been mentioned, one important cliaiiijc which has contributed very much to the increased use of submarine cables durinLj recent years, is the development of a system of ijrivate codes. Secret language always took, as it does now, two forms, code and cipher. Code, or pre-arranged language, is composed of dictionary words, the context of which has no meaning, but each word of which represents a phrase or a sentence. An\' two persons may arrange a code for private use Several such codes have been published, some of whicli are adajjted specially to a particular business, others to the affairs of daily life. The cipher .system, on the other hand, is constituted by a number of letters or figures arranged in a manner (|uite unintelligible to the orclinar>' reader, or even of letters and figures combined. This system is mostlv employed, in the shape of figures, in diplomatic or other Government com- munications. It is the most expensive form of .secret language, only three letters or figures being allowed to the " wortl " ffir tariff purposes. Various methods of building up a pri\ate code ha\e been introduced from time to time with explanatory books of reference.* Probably the first was that of Renter, followed .some time after — in i8r)6 — by that of the late Colonel .afterwards Sir Francis) Boiton, R.E.+ The telegraph companies at that time could but accept code on the same terms as ordinary messages. At the Rome International Telegraph Conference of 1870, however, certain regulations were laid down regarding the use of codewords; and again at the St Petersburg Conference of 1.S75. At the latter it was decided that code words should not contain more than ten characters. * Words of greater length in code messages are liable to be refused. Some telegraph companies, howe\er, accept them at cipher rates, i.e., three or five characters to a word, according to r^givic. Sub- sequentl}' the Bureau of this International Congress was authorised to coinpile a complete vocabulary of the words to be recognised and admitted "■' .Almost from the very beginning of siiljmaiinc telegraphy, tcmi)oranly improvised forms of codes were used both by (]overnments and by mercliants. On the l-ngiish land lines code messages were in vogue among the great mercantile firms as early as 1853, if not earlier. t The telegraph codes of the present day are built on somewhat the same principle as the above. They are improvements m.iinly in the sense of being perfectly simple instead of e.\tremely compiicalcd— and yet they are ecjually, if not more, trustworthy, from a secrecy standpoint. % A "character'' consists of one letter onlj-, e.\ccpt in the case of the combination c h. Almost invariably this is telegraphically expressed by four dashes ( — -), and treated as a single character. 1/6 ■ SUlSMAKINli TKM'.CRAI'IIS. f(ir code purposes. This vocabulary was duly printed and issued, l-'resh editions of it are brouf^ht out now and ai:jain, and three years after date of issue it becomes oblii^atory upon all parties to the St Petersbury; Convention to abide b)' it. The transmission oi submarine code messages is liable to be ])artiall)', or entirely, sup])ressecl at anj- moment by the Government of the country which i^ranted the concession for the cable in t]uestion. Moreo\er, (iovernment messages at all times take precedence (immediately on handing in) before all others. These conditions, under which all such conces.sions are granted, are very obvious and natural precautions, if only in view of war ; indeed, whether expressed as a stipulation or not, it is certain that any Government would be acting within its rights in suppressing code messages at such a time, and would almost certainly exercise this privilege. From the point of view of the general jiublic, the economy effected by the use of code is often even a more important consideration than its secrecy. A single code word, charged for only at a slightly higher rate than one ordinary word, may be made to convey the sense of a good many.* The telegraph cable thus becomes available for business and other ])urposes by many people who could not otherwise afford it, and the number of messages which pass over it daily have enormously increased in consequence. And with this increase in the number of them, there has not been the corresponding decrease in their length which might have been anticipated. The public has simply become educated to the more liberal use of the telegraph, and has availed itself of its fitcilities in the measure and in the s])irit in which they have been granted to it. The increase of the total volume of traffic, and of business leading to still greater traffic in the future, has more than compensated the companies for the economies effected by its code-using customers. The fact is, but for the code system, the existing number of cables * The following examples, taken tVoni a certain mercantile code, may be of interest here : — Code Words. Pl.iin Kiiglish Kquivalents. Eu'.iN, = Every article is of good quality tiiat we have shi|)ped to you. Standish, = Unable to obtain any advances on bills of lading. I'KNlsrONK, = Cannot make an offer ; name lowest price you can sell at. Co.MAil.LK, -= Ciive immediate attention to my letter. ("iKANi'HAM, ^ Wliat time shall we get the Oueen's Speech ? Gl.oucKSTKR, = Parliamentary news this evening of importance. FoRKAR, = At the moment of going to press we received the following. A striking example of the unlimited application of the code piincijile is the word "unholy," which was used to exjiress o/w Ituiidrcd and sixty i>.ths of the ocean far away from other I'.urnpean Powers. Section 8. — Institutions, Pai-kus, and Pukss Organs. In 1S71* the SOCIETV OI" TelE(JKA1'11 KNGINKEKSf was founded, mainly as a result of the efforts of Dr (afterwards Sir C. VV.) Siemens, F.R.S. ; General C. I"'. Webber, R.E. ; Colonel (afterwards Sir Francis) Bolton. R.K.; Mr C. V. Walker, i-.R.S. ; Mr Latimer Clark, M.Inst.C.E. ; and Mr W. H. I'reece, M.Inst.C.K. ;^ This was during the absence of several eminent telegraph engineers and electricians engaged abroad at the time, who would, no doubt, have co-operated in promoting and organising therefrom. .A complete discussion on this subject is one worthy of the International Telegrajjli Conj,ness, especially considering the larj^c number of so-called accidental injuries inflicted by the anchors of tishing craft which swarm in busy channels — such as the I'lc. 51. -Specimen of Ciiblo torn liy an Anchor. English Channel — and so frequently cause interrujition to our {Government's and other cables. An idea of the injuries so caused may be gleaned from the above illustration. * Thus, as was pointed out by Sir Henry Mance, C.I.E., in his inaugural address as President for the current year (1897), the Institution has just completed its quarter of a century. Sir Henry also took occasion to indicate the useful work done by the .Society during its existence. Throughout nearly the whole of this period Mr F. H. Webb -who is about to retire in favour of a well-earned rest — has acted as Secretary, and to his unwearying efforts its success, in holding together many diverse interests, may be largely attributed. It has been thought, therefore, that — if for these reasons alone — a few lines with reference to the history of the Institution from the telegraph engineer's point of view might not be out of place. t Ten years later named the " Society of Telegraph Engineers and Electricians." In 1883 it attained sufficient importance for incorporation under the Companies Acts. I Shortly after this occurred the death of that distinguished electrical savant and experimentalist, Sir Francis Uonalds, who bequeathed to the Society his almost perfect collection of books on electrical su 'jects, covering the very commencement of telegraphy. This was, indeed, a rich heirloom for so young a society to come in for. MISCF.I.LANKOUS AND lOMMKKCIAI- ki;Si;Mi:. iSl the society h;ul tlicy been in Miij^iaiHl. Its main objects were to bolii meetings of the teiej^M-aph enj;iiieers and electricians estabhshed in or within reach of London ; to read and (h'scuss at these mectin^fs papers deahn^' with telegraphic and cognate subjects ; and to print and circulate among its members (in all |)arts of the world) a journal reporting the proceedings of such meetings. It will be seen, by reference to the early numbers of this journal, what a large proportion of its contents relate to submarine telegraphy. T'or some time past, indeed, it had been felt that this was a branch of civil engineering which, by its rapid growth in importance and in the number of those engaged in it, required a s])ecial societ)' of its own, such as mechanical engineers already had. This was recogni.sed by the Institution of Civil Kngineers, who rendered the same practical a.s.si.stance to their new electrical offshoot as they had done to the Institution of Mechanical Kngineers (and do now in several other instances) by allowing the meetings to be held on their premises.* Later on, as the general evolution of telegrajjhy in all its departments ^' It Ilia)- lu'ic be remarked thai tlie Institution of Civil En^'ineers had itself produced some most valuable pajjcrs connected with calile work— from the historical point of view perhaps the most \aluable extant. The following are their titles, with the volumes of the Minutes of Proceedings of the Institution in which they are to be found :— " Submarine Electric Telegraphs." By F. K. Window, A.Inst. C.E. Vol. xvi. (1857). " Submerginjj Telegraph Cables." By T. A. Longridge, M.Inst.C.E., and C. H. Brooks. Vol. xvii. (1858). "The Practical Operations connected with I'aying-out and Rci)airing .Submarine Telegraph Cables." By F. C. Webb, Assoc. Inst. C.E. Vol. xvii. (1858). "Electrical Qualifications requisite in Long Submarine Telegraph Cables." By S. A. Varley. Vol. xvii. (1858). '■ The Maintenance and Durability of Submarine Cables in Shallow Waters." By VV. H. Preece, Assoc. Inst. C.E. \'ol. xx. (i860). "The Malta and Alexandria Submarine Telegraph Cable." By H. C. Forde, M.Inst. C.E. Vol. xxi. (1862). " The Electrical Tests employed during the construction of the Malta and Alexandria Telegraph, and on Insulating and Protecting Submarine Cables.'" By C. W. Siemens, M.Inst.C.E. \\)1. xxi. (1861). "The Telegraph to India, and its Extension to Austialia and China." By Sir Charles Tilston Bright, M.P., M.Inst.C.E. Vol. xxv. (18O5). Thus, the Institution of Civil Engineers may be regarded somewhat as the nurse of submarine telegraphy. When the Society of Telegraph Engineers was formed, the cardinal points had been settled ; indeed, submarine cable work was, to a great extent, an accomplished fact. The Institution of Mechanical Blngineers had also had some valuable jiapcrs upon machinery employed in connection with submarine telegraphy, viz. : — " Description of a Machine for Covering Telegraph Wires with India-rubber." P.v Dr C. W. Siemens, F.R.S. (i860). " On the Construction of Submarine Telegraph Cables." By Fleeming Jenkin, F.R.S. (1862). " Description of the Paying-out and Picking-up Machinery employed in Laying tht Atlantic T.-lcgraph Cable." By George Elliot (1867). l82 SUIiMARINK TELEGRArilS. had passed through the joiitliful and more rapid stage, and attained something like maturity, a kill occurred in its further progress, during which other branches of electrical work attracted more public attention — especially electric lighting. As the Society embraced all engineers and sdvaiits who occujjied themselves with electricity and its various applica- tions, the papers read at the Great George Street meetings now began to deal more and more with electric lighting, telephony, and the distribution of electric power, until — about the time of the Paris Klectrical Exhibition of 1 88 1 — telegraphy began to take, comparatively speaking, a back seat. .Accordingly, in 1S89, the Society was re-christened the Institution ok Eli-XTRICAL Engineers — a title more suggestive of its widened scope. To students of submarine telegraphy, however, its proceedings in earlier (la)-s under the former title had perha])s a greater interest — at any rate until becoming adepts and past masters in their profession. The following may be considered to be the more important |)apers relating generally to cable w(jrk which have been read before the Society of Telegraph I'-ngi- ncers from time to time : — "Contributions to the Theor\' of Submerging and Testing Submarine Telegraphs." By Dr Werner Siemens. Vol. v. (1876). " The Working of Long Submarine Cables." By Willoughby Smith. Vol. viii. (1879). "Cable Grappling and Lifting" By A. Jamieson, F.R.S.E. Vol. vii. (1878). " Submarine Telegraph Cables : their Decay and Renewal." By Samuel Trott and Frederick Adam Hamilton. Vol. .xii. (1883). " Deep-Sea .Sounding in Connection with Submarine Telegraphy." By Edward Stallibrass, A.M.Insl.C.]':. Vol. xvi. (1887). Most of the above papers, as well as several others, have alreach' been alluded to in this book in connection with those parts of our subject to which they more particularly refer. Some of the other contributions to the journal of the Society, concerning the various methods of electrical testing, the instruments to be used for this purpo.se, and for working cables, have also been referred to, or are in Parts II. and III. The papers by Mr J. J. F"ahie, Sir Henry Mance, M.Inst.C.IC, and Mr A, E. Kennelly (in 1874. 1884, and 1887 respectively), on their methods of Aiult-localisation and the discussions upon them, will be found especially interesting and instructive, though somewhat beyond the scope of the present volume.* The discus- sions on such papers will invariablj' be found well worthy of study--often * It may, liouevcr, be roinarked in |)iissinn that liin^ely owin}; to these tests, coupled with the " Fall of I'otnntial Test" of .Mr Latimer Clark, this art has been brought to such a pitch of ijerfection that in the present clay an electrician can often localise a fault in a subttiarine cable closer than the captain can navigate his vessel. MISCELLANKOUS AND COMMERCIAL KIvSUMl':. 1 83 elicitin;^ more practical infonnatioii than the papers themselves. Again, many of the annual inaugural addresses presented by the various Presidents of this Institution naturally contain much of interest concerning matters telegrajjhic — to wit, those of Dr C. W. Siemens, Sir William Thomson, Mr Latimer Clark, Mr C. V. Walker, Professor Abel, Lieut-Col. J. U. Bateman Champain, Mr W. H. Preece, Lieut.-Col. Webber, Mr Willcnighb)- Smith, Mr C. K. Spagnoletti, Mr Edward Graves, and Sir Charles Bright. The last-named, however, and that we liave recently had from Sir Henr)' Mance, are two which deal more especially with submarine telegraphy, historically and otherwise. J""or some )-ears before the establishment of the Society of Telegraph ICngineers, a certain means of intellectual intercourse for members of that profession, as well as for electricians and electrical engineers generallj', existed in the Press. The Electrician (original series, weekl)') was started as early as 1861,* and the Te/cgraphic Joiintal {<.m^\\M\\ scries, monthly and then fortnightly) in 1872;+ the main title of the latter having since been changed to the Electrical Rcvieio as a weekh' publication due to Messrs .Alabaster, Gatehouse, and Co. Previous to the above The Engineer was practically the only technical organ available to telegraph engineers, its \-\\-^\, Engineering, no\. having been established till 1S66. Some numbers of J'lie Engineer, about the time of the first Atlantic cable project, contain a good man}- articles of interest to submarine telegraphists. The early numbers both of 'The Electrician and of the Telegraphic Journal abound in valuable contributions — such as, naturall)-, we never see now — from the ablest authorities on ocean telegraph)-, and should be consulted by all students of its evolution and earl)- history. The above and the Electrical Engineer (at one time monthly, but now weekly) are the only English journals to which special attention need to be called to on the historical side of this de|)artment of electrical work. But telegrajjli engineers and electricians who wish to keep tht)roughly ujj to date n\ their knowledge of the most modern imjirovements in plant, testing-room instruments and methods, may also read with advantage the Electrical Engineer, the Electrical * The original /i/rr/r/t/ii/i - \\h\ch ceased to exist in 1864— is said not to have been in any way connected witli the present joutnal (appearing first in 1878), though got up in the same style. + A weekly publication bearing the same title had pre\iously made its appearance in 1S64. .Again, as far back as 1845, the late Mr C. V. Walker, K.R.S., had editc'd, for a short time, a highly interesting journal called the /:7ir/n'ui/ Miig(i:ini'. This latter somewhat resembling a "ijuartcrly," reporti-ig meetings and jtapers, besides reviewing books — was probably the (irst instance of periodic electrical literature, apart from actual books. 184 .SU15MAKINF. TKI.KCRAI'IIS. Review, .ind the EUctrical World of \e\v York, also the ijn'nci])al (jcrman electrical journal, Electrotechuisclie Zeitschrift, as well as the back numbers of the now defunct La Lumicre Electrique* The foregoing, as well as maiiy other useful periodical publications^ dealing with the subject in ICnglish and other languages, may be seen not only at the libraries cjf tiic great professional institutions already referred to, but at that of the Patent Office, Southamjiton Buildings, Chancery Lane, London — which is o|)en to the general |)ublic. The current numbers of most of them, we believe, m;;y now be also found in the reading-rooms attached to all the chief public libraries of the great provincial towns of the United Kingdom. Sl'XTION 9. — RkTROSPECT. With the exception, perhaps, of more careful preliminary surveys before the laying of a cable, and the ground being more completelj- sounded over previous to the selection — and in some cases the actual marking-out — of a route for the line, ;^ the operations of constructing,^ * Some years ago La I.UDiihr Electriqiie published a series of admirable articles on submarine telegraphy from the pen of Mons. K. Wiinschendorlf, the French (Jovernmenl engineer. These were much appreciated at the time, licnce his book (compiled from these), on a portion of which the present work is partly founded. t The Quarterly and Iulin/>uri;lt (formerly the North Britisli) have both from time to time publislied admirable articles regarding matters connected with submarine telegraphy, some emanating from that able writer, the late Professor Flceming Jenkin, F.R.S. Other magazines and journals have done likewise. Amongst those of compara- tively recent date may be cited e.\cellent articles, of the popular sort, by Mr Herbert Laws Webb (author of a useful little book on "Electrical Testing") in Scrilmo's Mai^ashie, and some b>- Mr A. P. Crouch in Cor/i/iill, as well as the Xineticnth Century. There are also various papers germane to the subject read before the British Association and Royal Institution from time to time, besides a ca])ital series of Society of Arts Cantor Lectures delivered by Professor (then Mr) Fleeming Jenkin, F.R.S., in 1866. X No doubt, partly owing to the light brought to bear upon the bottoin of the ocean by the "Challenger" K.\pedition of 1873-76, in which so many distinguished men of science participated. The work of this expedition was fully recorded in a series of large volumes (edited by Sir \Vy\illc Thompson, F.R.S. , and by Dr John Murray, F.R.S.), which are entitled " Reports of the Scientific Research Exploring Expedition of H.M.S. ' Challenger,' 1873-1876." The subject of sounding for telegraphic purposes has been very fully treated by Mr Edward Stallibrass, A.M.Inst.C.E., in a pajier — referred to above— read by him in 1887 before the Institution of Electrical Engineers, on '' I)ec|)-Sea Sounding in con- nection with Submarine Telegraphy."' Mr Stallibrass gives a complete sketch of the history of sounding work in all its aspects, and a detailed description of the apparatus used at various times by different parties. .i; X'arious experimenters have from time to time suggested cheaper classes of insula- tion other than that of guttapercha or india-rubber. These suggestions, liowever, come from peojile who appear to be ignorant, or obliviou.s, of the fact that the above costly mate- rials are only em])loyed because others, though pcpially ctVicicnl electrically under normal conditions, altogether fail to carry out the mechanical requirements f^r submarine calale purposes, quite apart from their physical failures, lack of durability, and subseivience to MISCr.LLAXKOrs AND COMMERCIAL KKSUMK. 185 laying, testing, and icpairin{^ telegraph cables arc carried out in much the same way now, and with much the same appliances, as they were some twenty-five years ago. That is to sa>', the improvements which ha\c been introduced during the last quarter of a century, arc improvements in details rather than in general principles. More radical changes may, l)erhaps, ba anticipated in the not ver}- remote future. There are some, at any rate, who look forward to the time when, through the further development and practical application of the theories of such learned investi- gators as Mr Oliver 1 {eaviside, I\R.S., Professor .Silvanus Thompson, 1\R..S.,* Professor Oliver Lodge, F.R..^.,+ not to mention that doyoi of electrical science. Lord Kelvin, :J: submarine telegraphy may be effected in an entirelj- different, and at the same time a simpler and less expensive, fashion than at present.^ The Cooke and Wheatstone of a new " root-in\ention " maj- even now be on the point of success. When so many able minds are found working about the same time upon similar lines — in electrical matters, teste the comparatively recent cases of (iramme and .Siemens, Swan-Edison and Lane Fox, and, again, Hughes, Graham Bell, and Edison — there generally has been some important practical outcome of their contemporaneous efforts. Meanwhile, one of the next important improvements in cable-working seems likely to take the shape of an alteration in the form of the cable itself, rather than in the instruments used with it. The, latter have now surroiiiulint,' influences. These matters were recently dwelt on by the author in the course of an article in The Elcctricitin (" I'roblems of Ocean Telegraphy," by Charles Hrijjht, F.R.S.E., vol. xxxi.K., p. 6). * The advent of ccean telephony^ as well as of high-speed ocean telegraphy, have been prophetically discussed by Dr Thompson, and particulars of his suggested systems will be found in many of his scientific p;ipcrs and patent specifications, as well as in Part 111. of this book. He regards the primary cause of retardation of current impulses to be "capacity"; moreover, he points out that this is a distributed^ and not a local, grievance. Flencc, whatever means are applied to a cable to counteract "capacity" must, in his opinion, be (//.v/r/'/w/iv/ also. He further believes that such a distributed remedy is to be found in bobbins possessed of electro-magnetic induction. His proposal is to construct cables ha\ ing such bobbins judiciously placed at intervals throughout the length of the conductor. t Author of that admirable treatise, " Modern \'iews of Electricity," one of the Xatiire .Series, which is responsible for teaching us more about electricity (from an enlightened standi)oint) than is to be gathered elsewhere, and a |)ublicalion th.it does the above journal and its i)ublishers great credit. .Another most heljjful work, which marked the introduction of an entirely new order of text-book, is "I'ractical Electricity," by Professor W. E. Ayrton, F.R.S. (Casiell and Co.). The latter sets aside the oft-repeated experiments with pieces of sealing-wax, a cat's back, etc., in favour of exjieriments having a more useful bearing. I Hcsides Mr Nikola Testa, and, still more, the late I)r Heinrich Hertz. S The suggestions of -Mr Heaviside, and those more recently made by Professor .Silv.-.nus Thompson, for high-speed telegraphy, are referred to fiuther in Part III. 1 86 SUBMAKINK TELEGRAPHS. probably been brought to their highest attainable degree of efficiency — cjuite beyond that required or justified by the cable itself under present conditions.* The human element scarcely enters into our calculations when machine- transmission is in question ; for, although the e\c can only read at a certain rate, the recorded message can be divided up in such a manner that different parts of it are being taken down by different clerks at the same time. Inductive Telegraphy. — Compared with the improvements last men- tioned, iNDUcrnE TeLEGRAI'Hv'- is truly " a big order." Yet even this achievement may not be very long dcla}ed, if we can judge by recent indi- cations. Within the last ten years or so various experiments have been made in this direction, across the broad rivers of India, and across certain channels of this country, as well as between boats and the shore, by Mr Melhuish of the Indian Telegraph Government Department, by the late Mr VVilloughby Smith, :|: by Mr Charles Stevenson, F.R.S.M.,and latterly, on a more extensive and practical scale, by the engineer-in-chief to our Government telegraphs, Mr W. H. Preece, C.B., F.R.S., assisted by Mr J. Gavey and Mr H. R. Kempe, A.M.Inst.C.E.^ Mr Preece has made tliis one of his special subjects, and attacked it with the business-like tenacity for which he is well known. He has, from time to time, given us full descriptions of his experiments in this direction. He has, in fact kept the world well posted * A certain economic limit being placed on the dimensions of the core. Modifications artecting the form of the conductor within the core have, however, been projjosed recently, and have constituted the subjects of iiatcnts by Mr (). Heaviside (1880), Mr W. H. I'leecc (1892), and others. These consist in multiple-wired cores, the arrangement of the conductors being designed to reduce their electro-static capacity as well as their resistance, and thus, according to the Kk law (see p. 203), to materially increase the working speed. These devices were principally intended to meet the special require- ment of long-distance telephony — viz., low capacity but they are, of course, applicable to electric signalling generally over long distances. + The first suggestion in this direction apjjears to have emanated from Mr J. \V. Wilkins, a telegraph engineer of the earliest day. In 1849 Mr Wilkins proposed inductive telegraphy as a means of establishing electric communication between Enghind and France though never as yet put into ))ractice on so large a scale. In those days this method similar in principle to later suggested systems — was spoken of as "telegraphy by means of earth conduction." I Assisted by Mr \V. 1'. Granville. Their experiments were later on extended by Mr Willoughby .Smith's son, Mr W. S. .Smith, the present manager of the Gutta percha Works at Wharf Road, attached to the Telegraph Construction Companx'. S Author of the famous "Handbook of Electrical Testing" (E. and F. N. Spon), which has now run through several editions; also of "The Electrical Engineer's I'ockct-Book " (Crosby Lockwood and Son). II In the course of papers read before the liritish Association's Meeting of 1894, and the Society of Arts in the same year, the titles of which wtre " Signalling Through Space " and " Telegraphy without Wires." MISC'KLI.ANKOUS AN'l) COMMKRCIAL KI-'.SUMI-;. 187 up, in this matter — as in others of an cleetricai nature — with reference to the stage of progress so far attained. This method of telegraphy between places at short distances has frequently been spoken of as "telegraphy without wires"; but, though an attractive title to those who look forward to the cheapening of practical telegraphic methods, it is scarcely an accurate description (as a rule) of its present a]jplication. This necessarily involves the employment of lengths of wire running parallel, or nearly so, at right angles to the direction of the com- munications to be effected, and of at least the same length as the distance between the |)oints. * The principles upon which it is based, and the manner in which it is carried out, are treated in greater detail elsewhere in this book. At its i^resent stage of development, inductive telegraphy does not seem likel\- to prove applicable to submarine working on anything like an extensive scale + — that is to saj-, between points at any considerable distance from each other. Moreover, if it were, there would not ajjpear to be any econom\' realisable b)- its adoption ; rather the reverse — as already shewn — since two long cables (one along each shore) would be necessary instead of one. I'or this reason, then, even if the able and experienced scientists now engaged upon the subject see their wa\- to making the inductive system (on its present lines, i.e., the long parallel insulated con- ductors) applicable in all other respects to long-distance signalling, it is hardly probable that it will be adopted for practical work on an extensive scale. If inductive telegraphy, as at present understood, is ever rendered thoroughl}- [jracticable for transmarine signalling oxer any considerable * Indeed, seeing that tlie eonductor has to repeat tlie s.uiie lenj,'th on each side as the distance acioss, the total len.i^th r(^c(uiie(i by this method should be douljle that involved by the ordinary direct subniarine tele},Maphy, though allouinL; of a considerable cost reduction in obviating the necessity of an expensive annoiir. + Its most promising sphere of utility for the present seems to be that of signalling between lightships, lighthouses, and the shore, a problem which it bids fair to solve successfully before long. The oidiniry method of communication by a subniarine cable, connectin;^.; up any two or more given points, is apt to break down in these cases through the constant chafing of the cable against the moorings of the light \ essel under certain tidal conditions, etc. Mr H. ISenest, .\.M.Iiist.C.E., read a very complete and iraeresting jiaper on this subject before the Balloon .Society in lS()2, imder the title of " Coast Telegraph Communication.'' In establishing telephonic or telegraphic communicati(ni along our coast-line u hich has never yet been completely carried out — all conducting wires should be subterranean. The War OtTice should recognise the force of this, and make it their business to see it projierly and com|)letely carried out, for in time of war all trlograph lines above ground uould be seriously imperilled. Just as the Meteorological Department are in a position (by means of telegraphic communication with certain outhing stations) to issue warnings of the coming storm, so should the Military and Marine Departments be in a position to obtain immediate notice of what is taking place within sight of any part of our coast. i88 sun.MARiNK ri;i,K(;K.\i'iis. disliincc, the main way in whicli, and the ^^cncral purpose for wliicli, it seems most likely to be ap])lie(!, is in the hands of the State, and (|)rimarily at all cventsj with a view to naval and other national contingencies. In times of war, two coasting lines in the hands of the same naval Power, or of two allied Powers, would possess obvious advantages, as a secure means of communication, compared with a single, or even a duplicated or tripli- cated line across the ocean. As has been already pointed out, International Cable Conventions nia\- jMove rather broken reeds for a great commercial nation like Great i^ritain to lean upon, in the event of a war with other na\al Powers. It is (|uite conceivable — na\-, more than conceivable — that, without having b\- any means lost command of the seas immcdiatel)- sur- rounding our coasts, we might be unable to pre\ent our trans-Atlantic cables from being cut b\- the enemj'. Now this would be the very time when — not to speak of the ordinary exigencies of naval communication in warfare — it might be of most vital ini])ortance for us ((•.<,'•., for avoiding the cutting off of our corn supplies through any unwarrantable panic among shippers on the American side) to keej) in constant touch, telegraphically, with the seaports, if jjossible, even of Canada and the United States. Again, strategically speaking, it would also be important for us to possess alter- native methods of communication with Ireland, the Hebrides, and the Channel Islands; perhaps, also, with certain neighbouring countries of the European mainland which happened to be allied with us, or " friendly neutrals." Under such circumstances, we should certainly bless the wise prescience of our (lovernment — possibly in collaboration with those of the United States, the Canadian Dominion, and the others concerned — if it established and maintained a practical sj-stem of inductive coast cables, (jranting that greater national security is at all likely to be attained thereby, expense (in the waj- of experiments, etc.) should scarcely be " an object " in the calculation. Afterwards, the only substantial item, treated as a ' question of national expenditure, would be the initial one of construction and submersion. This, of course, could then be readily estimated. ICven in the case of the trans-Atlantic communications, it may safely be averred that the combined cost of the requisite British and American coast cables would be small compared with man\- of our little Admiralty or War-Office " experiments." This c|uestion, then, in the humble opinion of the present writer, will \ery soon become ripe for practical consideration by " the powers that be. ' As to the still greater question of inductive telegraph)- for general u.se, who shall say that some entirel)' new system, such as may be more truly entitled to be called " telegraphy without wires," will not be evolved before long by which it may be successfully solved? Is it possible that one of MISt'KI.LANKOUS AND COMMKKCIAI. KKSUMK. 1 89 tlic invL-ntions ascribed about a year at^o to Ur Cornelius Her/, can relate to inductive telcLjraphy ? The indications which he has at present L,n'ven regardin,^' one of them certainly suggest some entirely new departure in telegraph}'. As it is stated they are about to be patented, the world will probably not be long kept in ignorance on this ])oint. The past work of \)v Her/, certainly entitles us to hope for further excellent and wide- reaching achie\ements from him in the domain of electricit)'.* Quite recentl)- a j'fnmg Italian electrician, Guglielmo Marconi, has in- vented an electro-static method of telegraph)- which would be independent of any continuous length of wire, and has, therefore, been spoken of by Mr John Mimro (in the ccjurse of an able article) as Ethenujl Telegraphy. Such inventions as those respectively of Her/, and Marconi might, of course, in the end, deal a veritable death-blow to submarine telegraphy as at present known, and as described in this book.+ On the other hand (if it ever came to that) they would bring about such an enormous e.\tension of tele- gra])hic work all over the \^■orkl — constructive, administratixe, and operati\e — that they would not nece.s.sarily be unwelcome to those who are pro- fe.ssionall)' or industriallj- engaged on it. Past and Future. — Submarine telegraphy is just one of these achieve- ments of human scie v,:e and perseverance which will ne\er be forgotten, even if it comes to be superseded in any form. When many of the passing cra/.es of the ]jresent time, manj' of its .sensational inventions, have been con- signed to limbo, f)ur great cable enterprises, and the men w ho carried them out, will be noted by the historians of posterity as some of the mcst charac- teristic features and ])er.sonalities in the civilisation of the latter half of this centur)-.* Still more sensational developments of material j)rogre.ss in the wa\- of communicating with our fellow-men may be in store for humanity. We may learn to fly through the air on wings, or Mr Maxim may construct for us a new aerial leviathan, while Mr Edison or somebody else teaches us, with some new fish-like craft, to cleave swiftly and noise- lessly through the still depths of the ocean, instead of pitching and tossing in a painful manner on its summit. But looking ahead, say, as far as the * In the course of an interesting article in the Fortnightly for January 1897, .Sir E. J. Reed, K.C.H., F.R..S., made si)cci.il allusion to these inventions of Dr Herz. t Signor Marconi's invention was dilated on at some length by Mr Preece in a lecture at Toynbee Hall, at the end of last year, on "Telegraphy without Wires," and again, i|uite recenily, at the Koyal Institution in the course of one entitled ''Signalling through .Space." From these it woukl sclmh that, so far, nine miles is the greatest distance at which this form of new teL'graphy has been successfully accomplished. This was a material advance on what had been done by the |)revious inductive methods already referred to. + The Committee of the International Submarine Telegraph Memorial have recently decided to establish a Jubilee Commemoration of Submarine Telegraphy in the year 1901. 190 SUHMARINE TELEGRAPHS. rising gencralioii and its immediate successors, it is extremely doubtful if any advance in applied science of such compar.itive importance to material civilisation will be seen for many a year as was marked by the successful layin^^ of the first great submarine telegraph lines. In the words of Rutlyard Kipling : — " The wrecks dissoh'e above us ; their dust drops down from afar — Down to the dark, to the utter dark, where blind white sea-snakes are. There is no sound, no echo of sound, in the deserts of the deep, On the great grey level plains of ooze, where the shell-burred rabies creep. Here in the womb of the world — here on the tic-ribs of earth — Words, and the words of men, flicker and flutter and beat." Some Enemies of the Cable. A jiiece of DecpSea Cable covered with Shells, etc. Barnacles on a Cable. " The Wonders ok the Deep." APPENDICES. ■.SaBMAK,XKTKU.X.R.U.nsuXDEK„.M,.OSTOKK,CK n. SUBMARINK TELEPHONY. APPENDIX I. SUBMARINE TELEGRAPHS UNDER H.M. POST OFFICE. When the Government took over the land telegraphs in >H/C tlicy at the same time became masters of all those submarine cables (belonging to the " Electric " and " Magnetic " Companies respectively) which went to form a ])art of the system — /.('..certain cables between Kngland and Ireland and between Scotland and Ireland, which united the land systems of each country.* The Electric Company's cable ship, the old " Monarch," was also transferred, along with the cables.f A few years later the late Sub- marine Telegraph Company's cable ship, "Lady Carmichael," was also acquired. Built in 1869, .she is one of the first ves.sels in the telegraph service \ie\it pcriiiniiently for cable work. This small paddle steamer has since been re-christened by the Post Office under the patronymic H.M.T.S. " Alert." There are in all, at the present time, fourteen cables (as shewn in the map on the following page) running from England to the various Continental countries around her, being the joint property of the different * For several years past it had been felt that the welfare of the nation as a whole would be best i)rovide(l for by giving the administration of all its telegraphs to the Post Ofifice authorities -in other words, mitio/ta/isiiig \.\\ti telegraph service. At last, in 1870, this was effected by Act of Parliament. The companies were bought out, and their valuable property acquired by the Stale for a sum total of ^4,182,362, including compen- sation to certain of the railway companies who lind enjoyed the privilege of transmitting public messages. The total mileage of hind lines transferred by this transaction was 48,378, e.xclusive of railway wires ; the total mileage of cable was 1,622 ; and the total number of stations was 2,488. 1 The Post Otificc at the same time took over those members of the staff of the principal companies who were available. Thus, Mr K. .S. CuUey became the engineer-in- chief, and on his retirement later, he was followed in tiiis capacity by Mr Edward Gra\es, with Mr W. H. IVcece as chief electrician, lioth these gentlemen had served with the "Electric" Company. Since Mr Graves' death, Mr Preece has assumed the double responsibilities of engineer and electrician. .Similarly, in 1889, when the Submarine Company's property was absorbed by the Ciovernment, some of their then staff were simultaneously given places in H.M. Postal Telegraph Department. ; - .-^ -— o — — '"' "'."" 194 SUItMAklNi: TI'.MUIKAI'IIS. administrations affected. These are irrespective of tlie Great Northern Company's lines to Norway, Sweden, and Denmark, of the Continental connecting' lini\s for the trans-Atlantic telegraph service, as well as of the ICastern and Direct S|)aiiish roni|)anics' cables. Out of these, six riMi between l'",nj;laiid and I'rance, three bein|4 main- tained by the En^dish (lovernment, and three, now, by the l""reiich,all bein^ equallv owned by the two countries. Included in this total, there are two cables reaching,' to Hel^dum. The.sc are maintained by us (half the cost being charged to the Ik-lgians), though the joint property of the iMiglish and ^ ... « BRUSSELS English and Anglo-Continental Government Cables. Belgian Governments. The two Anglo-Dutch cables are, however, in the sole possession of our Government. Then come, finalK', the three Anglo-German cables, regarding which it has already been stated tiiat each Government owns one cable exclusively, while the remaining one is held jointly by the two. Each Government looks after its own cable, and the joint cable is attended to by the English Government, half the repair expenses being chargeable to the Germans. The various cables owned, worked, and maintained by H.M. Government, are now laid, and attended to generally, by 1 l.M. telegraph shij) " Monarch," SUHMAKINK TKI.KCRAPHS UNDKK II. M. I'l )ST (ilKICK. I95 drawing's of uhicli arc licrc appciulcd, aiul also by I I.M. tclc^napli sliip " Alert " referred to above. The original " Monarch," after wliich tlic prevent ship of that title \va.s named, only served Her Majesty for a very j . »rt period. In the very same year that she was taken over by the Postal Tele^fraph Department, and on the very first piece of work she was sent out n|)on under tlie new regime, her cnj^incs broke down so hopelessly* that she had to be altogether abandoned as a ship. She is now doing duty as a coal-hulk. Though the then engineer of the Post Office (Mr R. S. Cullcy) had from the very first strenuousl)- urged on the Government the advisability of replacing the old "Monarch" by a new (iovernmeiil telegraph ship, it was not till a good many years afterwards that this recommendation was put into effect. Thus for some time all the {cw cables that were then under Government control were attended to as occasion rcqi'ired by various telegrai)h ships s|)ecially chartered for the purpose from ti' ; various cable contractors — indeed, in some cases (where proper cable shijjs were not available) ordinary steamers were hired and temporarilj' fitted with the neces.sary gear. It will easily be understood that this, after a time (as th.c number of cables gradually increased), became very expensive. This state of things would, indeed, have been practically im|)ossible now that the Sub- marine Company's lines form a part of the system requiring Government attention — thereby bringing the total number of cables at the ])rcsent time under the Post Office supervision well over a hundred.+ In 1883, however, the Postmaster-General, at the instance of Mr l^dward Graves (the then I'cjst Office engincer-in-chief), succeeded in persuading the Treasury to consent to the necessary expenditure, and the present " Monarch " u as built and ec|uii)ped at a total cost of about ^50,000. She is the result of carefully thought-out designs, largely ba.sed on the extensive practical experience of the marine superintendent, Mr David Lumsden,;): and of the assistant marine superintendent, Mr W. R. Culley.i^ the services of Mr J. II. Ritchie, * This \v;is under stress of weather, as grapliically shewn by the IllustnitCil London News at the time, and also in Mr Wilkinson's '' Subniavine Cable Layin;,' and Rciiairin;,'," J3ublished at The Electrician office. t The total number of conductors, including those in cables actually o-u'neii hy H M. ( ;o\einment, being above four hundred. This includes all short lines to the various grouos of small islands in the neighbourhood of dreat Britain, as well as those across lochs, rivers, canals, etc. \ Formerly of the Electric Telegraph Company. S Son of Mr R. .S. Culley, late engineer-in-chief Mr Culley has since become marine superintendent at the Dover Station of the Postal Telegraphs, in succession to the late Mr J. Hordeau.\-, Mr Lumsden still remaining chief superintendent, with headtjuartcrs at Woolwich. 196 st;i;MAi:i\i, rKi.i,(;i|) and Co., of l'ort-(ilas{.;ow, under the supers isioii of Mr KiU hie, llhistrations of tin- " Monarcli " are |.dven in l'"i^,'.s. 52 to 56. I'ij^f. 52 is a ^.jeneral t;levalion ; l''ii;. 53 a section ; wliilst l'"i^,'s. 54, 55, and 56 shew plans of the varions decks. Her principal dimensions are : I.enf^th hc-tsvtten |)erpendi(;ulars, 240 feet ; breadth, moiild(;d, 33 feet; depth, froiri keel to deck, ainidship, 20 feet; tonnafje, builder's nicasnrcineiil, l,34.H,', ;. Iler load draii^(ht, with fxx) tons of cable and I .'o toiH of fuel on board, \voiild be 15 feet 6 inches, but as she rarely has rc;ason tfj carry more than kxj tons of cable, this is considerably in excess of her nsnal dran^dit. II';r ordinary speed is about 10 knots, but she is cajiable of attaining; I3 at a push. .Sh(; has a raised (|uarler-(leck of the lirij.;!)! o( the main rail about 65 feet lonp;, a mord\ey forecastle about 20 feet, and a luurii ane deck rnnniii}^ from the front of the (|uarter- (lc:ck about KXj feel forward, below which are tin; d<;ck hoirses. The " Monarch " is rij^^'Cfl as a two-masted schooner with ptjle masts. I 'nlik(; many tele}4rai)h ships afloat, which have a ^reat sheave bolted on to 'he bows for cffcctin}.; cable- operations, the " Monarch's " bfjws are them- .selves so < onstructed that the bearin^js for the reels -.m- part of the ship itself, and },'reat stren^'th and convenicrnce are obtainerl, besidi-s tlie fact that the shi|) is not made to look U[S,\y and to|)-lu:avy at the; bows by the use of the conventional bow-sheaves* 'I'hc- |)latts of the vessel art! gradually formrd into two powerful box ^drders for the sujiport of the bow-sheaves, an.[ ton ,. It is fitted with two overhiiiij^ oiit- sic'e drums 6 feet in fliaineter and 2 feet 4 iiu lies on the face. '1 -esc drums, whii h are used for pickiiij^' up or paying' out th(! cable. * 'I'lii: sliips of tlic " I'laslj^rn '' ;iiiii :illi<(l 1 umpanif's arc now sii))ifarly construclcd witli tfic fjowsficavcs fjuilt inU) tlic fiiiji. iiKlccd, it is i)ciii-v((l, tliat this plan originated willi liir; patent specification No. iK,«4i of iK«g, taken out by .Mr I'cn y Isaac, M.l.N.A., of tile I^aslcrn Telejjrapli r'ompany. I'l.ATi: XI. I '/tl JllK- /t, |(,f,. '<■'::.-:.' [I'r.ATK XII. li ■| -11 Mil ^ f;?:: i'A 3 u X s I [ To /ace p. 196 (,»//.•/ /'/,:/,■ XI. ). [Plate XIII. ^ 1- i/l jIL C/5 I [To face p. \^{aflei P/ate Xrf.\ sriiMAKINi: TKI.KOKAIMIS UNDER II. M. I'l iS'l' OKl'ICK 197 can be worked eitlicr quite distinctly or to-^rethcr at will. The indicated brake hor.se-ijower of tiii.s t^ear is 150, with a steam ])re.ssure of 80 Ib.s. Ihat such a machine has cntjrmousiy heavy work to do I'and, therefore, re(|uires to be exceedingly powerful) will i)e readily understood when it is remembered that .some of the cables round our islands weit^h nearly 30 tons jjer N.M., while the very lightest Post Office type is as much as 7 tons per mile.* Again— as another rea.son why the "Monarch's" gear is, of necessit}-, exceptionally strong- when grappling in sucli shallow water as is met with Fli;. 57.— Cable Muchiiu-, Il.M. Telegraph Shiii " Moiiiirili." where the Post Office cables arc laid, foreign bodies attach themselves to the c.ible in great ciuantities.f * Cables in shallow waters must necessarily be much heavier than tliose laid on the ocean bed, wliich should be, indeed, out of all harm's way — pro\ ided they are once properly laid down— and not likely to be disturbed. Thus, the main (deep-sea) types of our Atlantic cables do not weijjh over li tons jier N.M. as a rule — or even less sometimes ; whereas in the line from Holyhead to Howth, near Dublin — the heaviest submarine telegraph cable— the shore-end type weij^hs as much as 28 tons |)er X.M. t A case is actually known where as many as thirteen anchors in all were picked up on a four-mile length in the Firth of Forth. Once, indeed, an actual ship was brouglit up with a cable, during repairs, in the North Sea — a small one, no doubt, but still a ship. It was raised sufficiently near to the surface to enable those on board the rejiairing vessel to recognise it as a schooner, before it fell oft" the cal)le and sank again to its bed below. 198 SUHMAKINE TKLEdRAPIIS. The length of cable to be raised 011 the bight in shallow-water repairs is small as compared with that dealt with in ocean repairs. The specific weight and accessories involved are, howe\cr, invariably much greater than in the latter case. Thus, the cable machiner\- of such a ship working in shallow water reijuires to be every bit ;is strong as the gear for ships working on ocean cables — and, as before stated, the " Mo.narch's " is actually the heaviest cable machinery in existence. Great advantages are claimed for the comparatively modern overhanging drums, such as this gear ])rovides.* These drums can be geared for dif- ferent speeds. There are two sjieeds on the port druin — I and i^ knots (N.M. per hour), the slow speed being ap|)licable to lifting heavy cables, and the quick for light ones. The starboard drum has only one speed — i.e., i mile per hour— being intended for intermediate types of cable. These drums, through the medium of a series of spur wheels, are driven by a double-cylinder engine which runs at from 150 to 160 revolutions per minute. Fixed to the quarter-deck, on the port side of the rudder-head, is a large cable shea\e, but it is only screwed down to the deck, being but seldom employed. Indeed, it is very usually unshipped, along with the apper- taining leads, from the cable machine, and kept amongst the stores in the ship's hold until required.^ Ships which are only intended for paying out comparatively short lengths of cable — such as " repairing ships " — are seldom provided with any cable gear at the stern, as it is considered that the greater convenience and safety of paying out from the stern for a short time only, is, in such instances i/iore than balanced by the risk always involved in passing the cable along from bows to stern on the completion of picking-up operations, previous to starting paying out.* The holding-back gear of Sir Charles Bright forms a part of this vessel's equipment for paying out cable: a full description of it will be found in Mr Wilkinson's " Submarine Cable Laying and Repairing." S^ Under the hurricane deck arc situated (1) a large office for the engineer- ing staff on the starboard side, and (2) the spacious electrical testing-room on the port side. On account of the special character of the work on which the " Monarch," * The usual practice, hitherto, had been to place the drums (which carry tlie cable) inside the framework. t This sheave is mainly used for passing' the cable round with ;i \icw to slack, and in order to avoid it being subjected to jerks at the bows by the pitching of the vessel. :j; Any advantage in paying out from the stern consists mainly in greater convenience. The vessel, however, always steers better when laying a cable from the bows. S '/Vie Electrician Printing and Publishing Comjiany, London. SLIIMAKINK TKLKCaAI'IIS UNDKK II. M. POST OFFICE. I99 lilvc otliL-r tclcj^rapli ships, is cin|jloyc(l, where all manner of speeds and all kinds of steerinj; are required from time to time, she ha.s a very com- plete sj'stem of telegraphs between different parts of the ship, so that the engineer in charge may be enabled to telegraph instructions from the mon- key forecastle to the steersman, as well as to the officer in charge of the engine-room. It is especially on account of the great noise made by the cable gear* on the fore-deck that some kind of telegraphic communication between the forecastle a, id the bridge is .so indispensable. A semaphore worked by hand is, however, very often found to answer admirably, with the advantage that there is practically no mechanism to get out of order and which cannot be readily repaired as in the case of elaborate mecham'cal or electrical telegraph systems. There are also many points in favour of ordinary speaking tubes over any electrical or mechanical methods of communication. The particulars of the " Monarch's" cable tanks are as follows : — There are three of them, all as large as the breadth of the shi|) in each \y.ut jicr- mits of The after tank, which is .selckim used, has a capacity of 2,730 cubic feet. The cone in the middle of it, with a capacity of 200 cubic feet, is used as a store for keeping meat. &c., in good condition, which purpose it answers excellently, owing to the usual supplj' of cold water kept in the surrounding tank. The main tank, situated a little forward amidships, has a capacity of 6,600 cubic feet, and is about 2S feet in diameter by 10 feet high. Its cone is used as a fresh-water tank, being able to carry some 10 tons. The fore tank is just forward of the main, and has a capacity of about 3,890 cubic feet. It is the same diameter as the "main," but little more than half as high. All the cable tanks stand on a deep double bottom of cellular construc- tion. These double bottoms are divided into five compartments, so that any part may be filled witli water to help to maintain the trim of the vessel. This arrangement is particularly valuable on a telegraph .ship, in compen- sating for the weight of cable as it is i)aid outboard from any particular part of the ship. Forward of these tanks is the hold for storing large telegraph buoys, buoy chains, grapnels, mushrooms, etc. The smaller buo)'s are fixed in the rigging except when under great stress of weather. On the top of the forward cable tank is the " 'tween decks." Between the main cable tank and the men's quarters in this 'tween decks is a large space which is used as a workshop. At the after end of the main tank are the coal bunkers, * More recent machines are, liowcver, very quiet in tlieir action. Thus it is tliat no deck-signalling apparatus is employetl on the " Eastern '' Company's repairing vessel. 200 SUHMAKINE TKLKCKAIMIS. whicli arc capable of carryiiii; about 260 tons of coal should so much be required, lictwecii the coal bunkers and tlu- after cable tanU is the entjinc and boiler space. A bulkhead is built just behind the inain tank, and tlie corner sjjaces between it and the tank — as well as the s|)aces between the two forward tanks — are used' for storing' fresh water. The cable tanks all drain into the ballast tanks below, and when they contain cable it is necessary to keej) tin- cable covered with water. The .side plates of the tanks are jj inch thick. On construction they were sub- jected to a pressure of 10 IIjs. per scjuare inch, as a test of their water- ti'ditness. Like the jubilee of the Queen's accession to the throne, the jubilee of the tcleijra])h in this country was comnieinorated in 1.SS7, in virtue of Cooke and Wheatstone having established the first practical telcL;rai)h — based on an application (if their combined patents — in liS37. This telegraph jubilee — mainly a Post Office affair — was celebrated by a bancjuet at which the then Postmaster-General (the late Right Hon. H. C". Raikcs) ]iresided. lie was supported by all the leading telegraph engineers and electricians of the day, .several of whom had taken part in the pioneer work of the early stages of electro-telegraph)'.* * There are two or tliree ivien .still li\ing who have been connected with clectro- tclegra])liy ever since its establishment. Thus, a short time ago the jubilee in the telegraph service of .Mr W. T. Ansell was commen.iorated by a banquet given in his honour. This gentleman, till recently the traffic superintendent of the Eastern Telegraph Company, may be said to be the doyen of telegraphy, lie was one of the earliest members of the '' Electric ' Company's staff. APPENDIX II. SUBMARINE TELKl'HONV. Inasmuch as in 1880 it was dctcnninccl by a court of law that a tclci)lionc is a telegraph,* it has been thought tliat a brief summary concerning the application of the telephone to submarine cables in its present stage might he suitable here, without actuall)- entering upon the principle or construction of the telephone instrument itself The advent of the telephone began a new epoch in the progress of electrical communication. In 1S76 Professor Graham lieli exhibited his original "speaking tele- graph " at the Philadelphia Exhibition, where it was seen and heard by Sir William Thomson, who introduced it to the notice of Eurojje at a meeting of the British Association held that year in Glasgow. The instrument bj- itself was not well adajited for speaking through long lines. The trans- mitter and receiver were both alike, and the .sounds were feeble. It par- took, in fact, more of the nature of a scientific toy than anything else, it has since become a u.scful adjunct to the telegraph, of which it ma\' be rcg.irded as the flower and culmination. In 1877, however, Professor D. I'",. Hughes, F.R.S., discovered the microijhone, which has, up to the present. Ijr.vcd the best transmitter to employ in conjunction with the Mell recei\er. The carbon transmitter, invented by Edi.son in the same year, similarl)- rendered the telephone a practical success. Various companies were soon promoted in the United Kingdom for establishing telephony throughout towns. In 1S80 the United Telephone Company f was incorporated in * Besides Mr Prccte, the exjiert witnesses on behalf of the Crown were .Sir Charles Bright, Mr \V. H. Barlow, Mr I.atinicr Clark, Professor D. E. Hughes, and Mr Warren de la Rue. On the side of the Company there were Lord Rayleigh, .Sir William 'riiomsoii, Sir ("■. (i. Stokes, I)r John Ilo))kinson, l)r J A. Fleming, and Professor Tyndall. t Now, by amalgamation, the National Telephone Company, which eventually absorbed all the other telephone working concerns in this country. The " National " Com|)any works under a (io\ernment license for working telephones between people in the same city or town. This was the outcome of the aforesaid legal action by which the Post Office estab- 202 SUBMARINE TELEGRAPHS. England, for purposes of telephone exploitation, since which most of our large cities have been connected by trunk telephone lines. Central exchanges for intercommunication by word of mouth have been established in all the larger towns, and the telephone is now in constant use in almost every business house. A merchant in London can talk with one in Birmingham ; a citizen of Edinburgh is now in earshot with a friend in Dundee. Corre- sponding, and still greater, progress has been made abroad — indeed, Eng- land was comparatively tardy in taking up the telephone properly, and even now the service can hardly be said to be satisfactory. Paris has for some time been able to " speak through " to Brussels and Marseilles; likewise Chicago to New York, by a line over i,ooo miles in length.* Honolulu has a telephone exchange ; and recently this instru- ment made its appearance on the Congo. Some years ago the late Mr R. A. Proctor predicted that ere long a whisper would be conveyed beneath the ocean, which none of the million waves that tossed above it would be able to drown. We are still some way off this imaginary consummation. It must be remembered, however, that after the opening of the first tele- graph line in England, and after the first telegram was sent, twelve years elapsed before the first submarine cable was laid. Since then, practically the whole of our earth has been strung with electric wires, and time and space have both been annihilated. Articulate human speech has been transmitted over wires many hundred miles in length — or (to speak with greater scientific accuracy) the vibrations of the air caused by the voice at one end of the wire, have, by the agency of the electric current, been faithfully reproduced at the other. The subject of long-distance telephony and submarine telephony has been very clo.sely studied by several eminent electricians for a considerable period, and various papers dealing with the difficulties and requirements have been read from time to time by Professor Silvanus Thompson, E.R.S., Mr W. H. Preece, C.B., F.R.S., and others, before the Royal Society, the British Association, the Institution of Electrical Engineers, and elsewhere.f lished their rights over the telephone as a form of telegraph within the meaning of the Telegraph Purchase Act of 1869. It is only a question of time when the telephone system generally will come under the direct management of the Post Office. The so(>ner this takes place the better, for the telegraph and telephone are obviously intended to work together. * In America the telephonic systems are owned by private companies, but on the European Continent chiefly by the Governinents in question. t One of Dr Thompson's schemes for ]iiceting the difficulties of long-distance tele- phony (submarine or subterranean) is to have a scries of leaks and induction coils along the line, with a view to freeing the cable raoidly of some of its superabundant charge. This is referred to elsewhere in Parts I. and III. amongst the recent novelties not yet fully developed in practice. SUBMARINE TELEPHONY. 203 The whole trouble in telephony is induction, which is a much more serious matter in this case than in ordinary telegraphy, on account of the delic.te nature of the instrument and the delicate currents suitable for working it. We have here to deal with ripples corresponding to the infinitesimal vibrations of the voice, rather than waves of electricity. The former are naturally more liable to get blended together by the attraction and holding back effect of induction, in proportion to the electro-static inductive capacity, than in the case of stronger currents producing waves.* To put the matter in a popular light, the electric current has the curious, and often inconvenient, habit of setting up other and different currents on surrounding conductors. In the instance of a cable, for example, the charge of electricity as it rushes along the wire induces an opposite charge on the wet .serving or sheathing, or on the sea-water itself These two charges attract each other — stay to exchange views, as it were — so that the original current — or rather, what proceeds of it — is very much delayed. The transmission of the delicate currents produced by the vibrations of the human voice is under these circumstances liable, in extreme cases, to be practically impossible. As we know, the speed at which signals can be made to follow on one another in such a way as to be read separately at the other end (instead of getting thus blended or blurred together) is dependent on the amount of what is known as the retardation of the cable. This retardation is made up by the combination of the total resistance offered by the conductor ( = R), and the total electro-static capacity (for induction) of the cable ( = K). It is, in fact, the product of the two ( = KR). The maximum speed practically attainable (for separate distinguishable signals) is, indeed, inversely proportional to this factor as announced by Lord Kelvin as early as 1856. Mr W. H. Preece has shewn that this same law (usually spoken of as the KR law) is the sole factor which governs the practicability of being able to hear through a telephone at the receiving end of a telephonic circuit — i.c., in such a way that the separate voice ripples shall be distinguishable and not " blurred " or blended together on arrival at the further (receiving) end. Thus, in order that speech through a conductor may be practically possible at all, the retardation, or product KR, must be very much smaller than for fair working speed on an ordinary telegraphic circuit. In calling attention to this fact, Mr Preece gave, as the result of * The limits are also much more confined with the telephone, owing to the fact that so far the application of any form of relay has not been found possible as in a telegraph cncuit. 204 SUBMARINK TELEGRAPHS. experiment, the outside figures for "KR" at which speech becomes practicable or impracticable, as the case may be. The results shewn were obtained on some of the Post Office cables, the trials being made with a view to testing the practicability of a telephone circuit between London and Paris for the proper interchange of speech between those capitals. The figures given by him were as follows : — • When KR=i5,cx'K) (or over) speech becomes impossible. „ =i2,>.oo „ „ „ possible. „ =10,000 „ „ „ yood. .. = 7.500 „ „ „ very good. „ = 5,000 „ „ „ excellent. „ = 2,500 (or under) ,, „ perfect. The point of difference in the conditions for telephony between aerial and subterranean or submarine lines is, of course, that the latter involve induction to a much greater extent ; indeed, overhead conductors, under favourable conditions (owing to the distance of the suspended wire from the earth), introduce hardly any at all. As, moreover, the induction recjuircs to be much less on a telephone circuit than on an ordinary telegraph circuit on account of the difference in the nature of the instrument and current employed — and, since the retarda- tion (as expressed by the symbol KR) varies directly with the length of the line — it is obvious that the length of underground or submarine cable (still more than the length of overhead wire) is of a strictly limited character — that is to say, with the present known devices. Again, as a metallic circuit for telephonic purposes is absolutely essential in long circuits on account of the extra induction introduced when using the earth as a " return," the distance between which telephonic working is possible is still further limited.* The going and returning wires of a metallic loop must also be alike exposed to this influence from without. The practice is, therefore, to cross the wires so that they exchange places at intervals along the route. The electric echoes, sputtering noises, or " hypnotic suggestion:; " from other lines are thus annihilated, and overhearing, thet retically speaking, should be impossible. This looping, however, has the effect of something like doubling the KR by, roughly speaking, doubling the length of wire in * The extra inductive phenomenon here referred to is the " cross-talk '' — as it is popularly termed— from neighbouring circuits using the same (earth) return. Moreover, the earJi is objectionable for the return in long circuits owing to the efiect of earth currents — however weak — on so delicate an instrument worked only by the feeblest of currents. Again, the employment of the earth is often ruled out of court on all tele- phone circuits subjected to neighbouring wires conveying stronger currents — also on account of induction. SUBMARINK TELEPHONY. 205 the circuit. Initial cost has also to be taken into account. The smaller (and shorter) the wire, the less it costs, and the lower the inductive capacity, but on the other hand the higher the conductor resistance. To complicate tlie matter further, we know that the resistance increases in a higher ratio than the capacity for induction diminishes by the above. Thus the resist- ance and capacity have to be so adjusted (by the type of wire or cable selected) as to give the most effective combination, compatible with a certain limit of initial cost. London-Paris Telepikjne Link. From what has preceded it will be seen that the question as to whether a telephone circuit could be satisfactorily established between London and Paris was not by any means one which could be .settled off-hand. Thus, no little credit is due both to the French and English Government officials — and especially to Mr Preece — who carefully went into the matter before it was 2. fait accompli^ by the greatest city in the world being put into tele- phonic communication with the gayest. The idea of connecting London with Paris by telephone first emanated fiom the French people. M. Coulon, who was the Minister of the French Administration des Pastes ct Tch'graphes, thought telephonic connection both feasible and desirable, and communicated with the authorities at St Martin's- le-Grand upon the subject. Having been proved experimentally by them to be scientifically possible, the Treasury made no difficulty in coming forward with the necessary funds. This undertaking w.is actually carried out in 1891 — fifteen years after the invention of the telephone— and was the first instance of submarine — or rather partially submarine — telephony being established.* Though, of course, only on a small scale, it has proved entirely satisfactory, and up to, or even beyond, all expectations. Inasmuch as the London-Paris telephone circuit would be partly com- posed of aerial wire (at each end) and partly (in the middle) of submarine * In 1889 the telephonic system of France came into the hands of the Adminhtr,Uion des Posies ct Ti'li'^raphes. The English Post Office and tlie aljove French Administra- tion in that year purchased, as a joint property, the Channel cables of the Submarine Telegraph Company, and their next step was, as stated above, to project a telephone line and cable from Londcm to Paris. Mr Preece had just designed a river cable to cross the estuary of the La Plata and connect the cities of Buenos Ayres and Montevideo by telephone. This cable was 28 miles long, but the bronze overhead wires brought the length of the entire line to 186 miles and the KR to 10,400. The speaking attained on this line is, however, very good. 206 SUBMARINF TELEGKAPHS. cable, a number of experiments were tried with various types of overhead wires applied to artificial copies of the electrical components of different types of submarine cable in order to arrive at what would give the best result. In Mr Greece's experiments he found that speech would be good on an overhead copper wire if the KR did not exceed 10,000, onan overhead iron wire if the same did not surpass 5,000, and on a submarine cable or under- ground wire if it be within 8,000. This last figure, in fact, determines the design of a telephone cable — i.e., the type of conductor and the thickness of its insulation — just as the previous figures determine that of an aerial tele- phone line according to the metal used. Iron is clearly unsuitcd for long, or trunk, telephone lines, because its specific KR is so large, and, in fact, it is never emploj-ed except on short, or exchange, circuits. Copper, having a lo\ ■ electrical resistance, is used for long trunk lines and cables. The total distance from London to Paris by the railway routes on each side is 371 miles, comprising 70 miles from London to Dover, 21 miles from Dover to Calais, and 180 miles from Calais to Paris. The \oo\y circuit being essential, the length of wire needed is, of course, twice 271, or 542 miles, including 42 miles of submarine core. It was decided on each side to make two separate land lines with a common cable of four conductors, the joint property of both Goverinnents. The English land lines are of copper wire, weighing 400 lbs. to the mile ; the French are of the same material, but of a gauge represented by 600 lbs. per mile. In both cases the wires are elevated on poles 30 feet above the ground. The connecting cable, as designed by Mr Preece and his assistant, Mr H. R. Kempe, contains four separate insulated wires, or cores, each consist- ing of a strand of seven copper wires (each wire being 35 mils, in diameter), weighing 160 lbs. per N.M. The above stranded conductors are individually coated with three la\ers of gutta-percha alternated by Chatterton's com- pound. The dimensions of this dielectric arc represented by a weight of 300 lbs. per X.AI., bringing the total weight of each core (conductor a, id dielectric) up to 460 lbs. per N.M., and the diameter to 390 mils. The copper used for tlic conductor is of the very purest obtainable for yielding the highest specific conductivity possible. The resistance of each conductor in the cable is about 7.5 to ^.6 ohms per N.M. at a temperature of 75' F. The capacity for induction of each N.M. of cor*^ does not exceed 0.305 microfarads, its in. ulation being not less . than 500 megohms at 75° F. The four cores, as above descHbed, are laid up together, wormed by a serving of tanned hemp; and the diagonal pairs are u.sed together in the same metallic circuit. The cable sheathing consists of sixteen galvanised SUBMARINE TELKI'HONV. 207 iron wires, of 280 mils, diameter, their individual strength being represented by a breaking strain of 3,500 lbs. — or over li tons. An illustration of the cable — which was constructed by Messrs Siemens Brothers— is given here (Fig. 58). It was laid by H.M.T.S. "Monarch" and the Post Office officials in March 1891, when the heav\- snowstorm and other inclement weather then in force greatly interfered with the opera- tions. The length of the cable is 20 N.M. : it extends from St Margaret's Bay, near Dover, to Sangatte, near Calais. The land lines on each side had already been completed by the I'rench and English Governments respectively. The total length of the line is 31 1 English miles. The copper resistance of each metallic circuit is 1,380 ohms; and its capacity (calculated) 5.3 microfarads. The total KR is, therefore, 7,314, which brings the circuit well within the limit of good speaking as defined by Mr Prcece. The instruments used in London are the usual I'cjst Office teleph(jnes, each being fitted w ith two double-pole Bell receivers. In Paris, the Ader, the D'Arsonval, and other telephones are used, subject to the approval of the French Administration. The first circuit was opened to the public on 1st April 1891, the traffic being considerable from the outset — in fact, more than could be dealt with on a single circuit. In February 1892, the second circuit was thrown open for traffic, and both circuits are now always fully occupied. The present charge for a conversation of three minutes' duration is 8s.* The line is largely used by members of the London Stock E.xchange and Paris Bourse,! as well as for Press work and general commercial purposes, I'lc. 5S. — The London- 1 'aris Tcleiihont- Cal.le. * Two consecutive periods of three minutes may be arranged for ; but in no case can more than six consecutive minutes be allowed, except during slack ]5ortions of the day ; and then only by arrangement at the time of application for a conversation, and on the understanding that if the line is leciuircd at any time after the expiry of six minutes it will be taken. The line cannot be pre-engaged. It is customary for users to either write or telegraph to their correspondents to be in attendance at a certain time, and then wait their turn. + Thus during the middle portion of the day the traffic is heavy, and users of the line occasionally have to wait a short time for their opportunity. 208 SUBMARINE TELEGRAPHS. both circuits beiiij^ always open day and night. The average number of me.ssages per day (on the two circuits) is about 250. This telephone line has since been followed by another* in 1893 between Scotland and Ireland (Glasgow to Hclfast), and there is a further jjrospcct of our being put into telephonic communication with Brussels and Berlin. in spite of the electrical difficulties of the problem, inventors and exjjcri- menters are constantly engaged in endeavouring to better these beginnings, anrl even hcjld out some hope of some daj- talking to America by telephone. For full information regarding the whole subject of telephony, the reader is referred to Messrs I'reecc and Stubbs' e.xccllent trcati.se thereon. f "" The sul)ni;uinc cable in circuit licre is of preciscK the same ])attern in cvvvy respect as the Anglo-Continental cable just described, except that the served and wormed cores have a brass tape sheathing" round them. This is in order to co|)e with the depredations of the l.tiinioria terchraiis-w niollusc- like worm distinct from the teredo of the Eastern seas. It has a pri'dilection for the gutta-percha as well as the hemp serving, and has been found within recent jears to infest even these (non-tropical) waters. This is possibly owing to cables from the tropics being brought home in the course of repairs, and the germs being communicated at cable factories ; indeed, the core is often resheathed for second use. Thus, since 1S93 it has lieen the custom witii tho Post Ofifice to apply metal tajjing to the core of all I'ost Ofilice caljles. It is also partly on this account that the Department always specify hemp instead of jute for the inner serving ; though it may I c doubted whether the former withstands the ravages of submarine borers any better than the latter. + "A Manual of Telephony," by William Henry I'reece, C.Ii., F.R.S., and Arthur J. Stubbs (Whittaker and Co.), il, f. ii ■''4 ■-1 *?>■ m «•>. I ■: \. -.lit' ■ 'Ik .■ [■ S'O- ■>!' ' i .. ,■•.' ^ fs, ■ ■ ■ Ai-i^ f«-: GREAT BRIT*In'7^ / .^^iiX, \ IVy^'*^' X AND IRE R U S\S I A M^rjoM G E R MANY -O^ Al J'* Xps/anTe fer' AUSTRIAV^UNGARV. ^ -^ w^ O -n .V r I A TT Ouuik^^tc;;: V«pvr5C T ^ Virtbd -■^^ * o * I C23 M O -V (T. IRI II M IK £ Iladeira ' Moi'ocott ^'\? 1.. ,P. E\ R S I A AFGHANISTAN T I B E T EGYPT' TEIIAN '.Jaak f I STAN <$> I'-/''' N n I SAHARA D E S E R T I A/«c« y6 S O U D A ;. Ichmi .K-' „lri ...I"" \ c. V j^»j£,^. ombny .N .ABYSSINIA SEA '^^^-^ / ;^;^p«<(rrt ^Maiir LVvlon l£ Gulf of Guinea\~»ri.ci/M ^ CI 1 X Z? "^ 1 1 O ^ T I. A ■■•^ T 1 C \\ .l/.v. I IS^ D I A JS^ .VyrAe//-/* ...a/fe-i o c 3^ O C E A 1^ iCAPE COLONY C of Gaud Boy '^^^ ^ Submarine Cables Working . Constructed and Partly Laid Projected srnAftwt acf ii>HO TW Z\ yftuint'/ttf PA C 1 P i iton ALAND N.B. Only the principal land lines connecting the submarine cables of THE WORLD ARE SHEWN HERE / V ^ll-if Wne li^tuUf 81j.Ui.i..I 1' i',' 6 ■■7 V -A D O M I ^v^4, A M E N I *^WJ OF R T IT v^%^ ': *■'■;■*' i Wiuthmj^ton s i btihrjrttm^ '»ft ihnnifStoi A/ T f*Strmtuiar CV)K MEXICO f SEA '■■< iwta ^ E N £ ^ ' COLOMBIA lECUADOR -O 6 •\\Asaruri4^ B It A Z I L Bahiar oilan/ic ^ ^ n i.r'r/p BOLIVIA O *A^nniwt OCEAN Valpuraisd o* ^ Sauting "* A O S C) r L A C E U T H\ N T I C N Cone^aum/ f^^ixeaiojf ^^va X o Co TAOON I A V "-Ji I Li>tXvvT>v«i^ M^ piJBiiSHEO BY Ch^'SBy LocKWOoo S Son, Lonuon f., H f. :?,- PART II THE CONSTRUCTION OF SUBMARINE TELEGRAPHS CONTENTS OF PART II. 4'»t» CHAPTER I.~THE CONDUCTOR. Section i.— Copfkr - - - - - - • - 214 Section 2.— The Conducting Wiur, ------ 227 CHAPTER n.- THE INSULATING ENVELOPE. Section i.— Early Methods of Insulation for Subterranean and Si'tiAQUEOus Lines - - - ... . .243 Section 2. — Cutta-percha : How and Where Oihained - - - 248 Section 3.— Chemicai,, Physical, Mechanical, and Electrical Pro- perties OF Gutta-percha ....... 262 Section 4.— Method of Purifyini; Gutta-percha - - - - 285 Section 5.— Wh.loughby Smith's Gutta-percha - - - - 297 Section 6.— Manufacture of Core: Covering Conductor with Gutta- percha -.--.--..- 299 Section 7.— India-ruisber -..-... 332 Section 8. — i^elaiine Merits of Gui ta-pfkcha and Iniiia-rui)1!ek - 348 Section 9.— Other Suggested Lnsulatinc; Maierials - - - 351 CHAPTER III. JOLVriNG. Section i.— General Remarks and Implements Used . . 356 Section 2.— Jointing the Conductor - ... - , 360 Section 3.— Jointing the Insulation: Gutt.\-percha Cores - - 366 Section 4. — Joinitng Vulcanised India-ruhher Cores -^ - - 376 CHAPTER IV.~MECHANICAL PROTECTION AND STRENGTH. Section i.— Metal Taping ....... 381 Section 2. — Inner Serving ....... 391 Section 3.— Sheathing - - • - - - - - - 403 212 CONTENTS. I'AGE Section ^--Application of thk Shkathing Wires to the Served Core 430 Section 5.— Compoundino and Outer Serving - - - - 455 Section 6.— Stowage, Testing, etc. ------ 476 CH.-XPTER \\-- COMPLETED CABLE. Section i. — REyi'iUEMEMs am> Tests ..... 4S0 Ski HON 2.— Mechanical Tesiing -...-- 484 Section 3.- Lighi c"ai!I es -.--... 494 APPENDICES. I. Lkgai. Stanharh Wiui. GArGK ..-.-. 513 II. Si'ix IKICATION oi' .-VxGi.o-.^MEUicAN Telegraph Company'^ \'alf.ntia— Heart's Content Caiu.e, 1894- - - - - - 514 III. Post Office Specification of Anglo-German Cahli:, 1891 - - 516 IV. Forms for Electrical and Mechanical Data - - - 522 Kastcrii .iiul Uiiiziliaii-Sul)iiiarinc Oimpanies' Telfgrajih Station at Carcavellos, Lisbon. PART II.- CONSTRUCTION. COMPOSITION AND MANUFACTURE OF SUBMARINE \ TELEORAPH CABLES. NOTWITHSTANDINc; tlic modifications which have been proposed from time to time, all submarine cables laid up to the present* have been of the type first adopted in 185 1 for the Dover-Calais line, comprising: — 1. A central conductor for convej'ing the electric current. 2. A covering of iiisulating material round the central conductor to prevent leakage. 3. An outer metal sheathing to protect the insulation from possible injur}' during and after submersion ; and to give sufficient tensile strength to permit of the cable being subsequently raised, if necessary. The insulated conductor is generally termed "core." Where this expression is used here, it is in that sense. * The exceptions arc the Black Sea cable, which only lasted a very short time, the uncompleted cable from Oran to Cartagena, and some other less important lines of earlier date which never did public duty. CHAPTER I. • ., ■ THE CONDUCTOR. ' Section i. — Copper: Electrical Conductivity: Physical Properties: Uifferent Species: Electrical Tests: Formula' and Data: Influence of Temperature: Suggested Substitutes. Section 2. — The Conducting Wire : its Form — Different Types compared Electrically and Mechanically : Leading Principles — Initial Tests. Strand Manufacture : Machine for Laying up Wires : Length : Gauge : Lay — Rate _ of Work. Section i. — Coi-pek. Electrical Qualities. — Kvcry material ma\- be said to be a conductor of electricity ; it is only a matter of degree. The question first ari.ses, What constitutes a good electrical conductor, and \\h\- are the metals found to be the best conductors ? Probably the fact of metals being highly homogeneous and very dense* in their texture, as compared with other substances, has something to do with it. Mi.\tures of good con- ducting materials will not conduct as well as each material when pure. This is, no doubt, owing to the variation in te.xturc and a certain chemical action between the molecules setting up a complete change in the resultant material. I'^or instance, lOO yards of pure silver i inch thick melted down and mixed with a similar 100 yards of pure co|:)per of the .same thickness, each having the same conductivity when alone, would not conduct twice as well as either wire by itself, though it would otherwise (having double the thickness for the same lengthj but for some specific change having taken place. Similarly, the conductivity of the alloy of the two metals would be distinctly less than the wire of the same dimensions composed of either metal in the pure .state. Copper, the electrical conductivity of which is higher than that of any other metal commercially available,t has been invariably made use of for the * Physically speaking, electrical conductivit;/ may be said, as a rule, to go with opacity, and electrical resistance with transparen( y. t The only metal which when pure has, generally speaking, slightly higher electrical conductixity is silver, and this is naturally ruled "out of court" for conducting purposes on any large scale if only on account of cost — £^ 5s. per lb. as against yd. to 8d. per lb. for copper. THE CONDUCTOR. 21 5 central conductor of submarine cables. The following table gives the con- ductivity (or conductance, as it is now sometimes termed) of the principal metals and alloys relatively to that of pure silver, at o" Centigrade : — Silver (annealed) ------- loo „ (hard) ....... ij^. Copper (pure) - - - - - - - loo „ (annealed) ...... gft „ (hard) - - - - - - - 94 Clold .--...-- 74 Aliiniiniiim (annealed) ------ 53 Platinum - - - - - - - - 17 Iron (pure and soft) - - . . - - 16 „ (telegraph wire) - - - . . - 10 Lead ........ 8.2 German silver ------- 7.5 Mercury (liquid) ------- 1.6 Selenium (annealed) .--... i Mechanical Qualities. — Besides its electrical suitability, copper has excellent mechanical qualities. To begin with, it has great powers of e.xtension. It will, in fact, stretch 10 to 15 per cent, of its length before breaking ; so that, if a cable is subjected to heavy strain, the conductor, permanently stretching* much more than the rest, will remain intact until after all the sheathing wires have parted, cominunication being thi s maintained to the last.f The copper used for conductors of submarine cables is .selected, however, rather on account of its electrical than for the sake of its mechanical features. Copper wire does not, in fact, usually bear a greater strain than the equivalent of 17 tons to the square inch J when ainicaled — the soft form in which it is used for purpo.ses of elec- trical conduction ; the hard-drawn, "camperneal," copper wires (unannealed) standing a strain tantamount to some 30 tons per square inch. The * Amongst the curiosities in early inventions was a special cable, devised in 1858 by Captain Drayson, R.A., and Captain Binncy, R.E., the object of which was to provide for the contingency of a longitudinal strain. It was called an " Elongating Tunnel Sub- marine Telegraph," and consisted of a single wire conductor in the form of a helix surrounded by india-rubber in which it was capable of moving freely. No further pro- tection or strength appears to have been provided. Various other spiral conductors have been designed of tubular shape, by way of securing elongation and elasticity. t It is unfortunate that the insulating material outside the conductor (gutta-percha or india-rubber) does not also confine itself to stretching instead of being correspondingly clastic, and therefore having a tendency to leave bare places on the copper wire with a certain amount of strain. \ Thus the tensile strength of an ordinary average strand is represented by a break- ing strain of about 200 lbs. This is, however, practically never turned to account owing to its accompanying elongating qualities being far beyond that of the rest of the cable. 2l6 SUUMAKINE TELEGRAI'IIS. density, or specific ^ravit)', of pure annealed copper at Co F. is [generally taken at 8.9* and its meltinfj point at 2000 V. Conductivity of Different Species of Copper. — In the earl)- (la\s of submarine tele;.,M-apiiy the purit)- of copper was supposed to be sufficiently well indicated b) the degree of facility with which it passed through a die. This, of course, would be {Governed In' different degrees of softness, but the causes of the widely \ar3'ing conductixity values, as determined by physicists at that time, remained entirely unexplained. The table below serves to give an idea of the tremendous variation obtained by different earl)- ex|)erimentalists for the conductivity of copper, as compared with that of pure silver, taken at 100 : — Rcc((uerel - - - 95.3 Snow Harris - - 200 Riess - - - 67.2 j Huff - - - 95.4 95-3 , Snow Harris 67.2 i Huff 734 1 I'ouillet - 91.2 Arndsten - 66.0 Leiiz - - - 73.4 I I'ouillet - - -73 Davy - - - 91.2 I Arndsten - - - 98.7 Christie As a matter of fact, in the above, the only results of observations made at a uniform temperature (o" C.) are those of Becquerel, Lcuz, ;uk1 Arndsten. It is believed that Mr Latimer Clark was one of the first tt) bring to light the wide variation .^vlsting between the conductivity of different species of copper. In 1857, whilst the first Atlantic cable was being manufactiu'ed. Professor William Thomson (now Lord Kelvin) made the discover)- 1 that the presence of foreign substances, e\en in minute quantity, reduced the conductivity of copper to a very marked degree, and he pointed out the effect this would have on the speed of signalling.* In i860 Dr A. Matthiessen made a complete investigation of the subject, having been requested to do .so b)' the Committee of Inquiry appointed by the Board of Trade in conjunction with the Atlantic Telegraph Company.^ He first experimented with pure copper carefully prepared by the method of electrolysis, and then observed the effect pro- * One cubic foot weighs about 556 lbs. + This discovery was made owing to a suspicion that the conductor was not electri- cally uniform. The suspicion was followed by an electrical test on various lengths, and has led to the present practice of a test for conductivity being applied to short lengths of a certain proportion of the hanks of copper on arrival at the cable factory. Since the above, a branch of copper manufacture has grown up for producing what is known in the trade as "Conductivity Copper," to meet the requirements of all specifica- tions subsequent to this date. , ■ , ■; I Proceediiii^s of the Royal Society, ]\xwQ. 1857. S Joint-Committee to inquire into the Construction of Submarine Telegraph Cables, 1859. Hluebook, with Report and Evidence, published 1861. THE CONDUCTOR. 217 duccd on tlic conductivity by tlic separate addition of tlic |)rinci|jal substances in natural combination with copper ore; he subsequently analysed various samples of commercial cojipcr, measuring their different conductivities. Dr Matthiessen found (what is now ^^enerally reco^niised) that the merest trace of arsenic is sufficient to reduce the conductivitj- 40 per cent.— /'.('., from 100 to 60* — and when the propcjrtion of arsenic is increa.sed to 5 per cent., the conductivity falls as low as 6.5. It is reduced as much as from 100 to 78 by 0.05 per cent, of carbon, though the latter is itself a very iair conductor ; to 70 by 0.13 per cent, of phosphorus, and to 92 by 0.18 per cent, of su!i)hur, which also renders the copper verj- brittle, forming sui]jhurct of copper in some degree. The presence of either bismuth or silicon have since been found to have damaging effects on copper — both electricallj' and mechanically speaking — almost equal to that produced by any of the above metalloids. The action of oxygen is still more cogent : by melting ])ure co])per with a very .short exposure to air, traces of sub-oxide of co|iper formed, such as were too minute to measure by the then known methods of chemical analysis, had the effect of reducing the conductivity to as low a figure as ^6 : it rose again to 96 after hydrogen had been forced into the molten metal for three hours, thereby reducing the sub-o.xide. The influence of metals, though generally less apparent than that of the metalloids, tends in the same direction. The conductivity of ])ure copper alloyed with 0.48 per cent, of iron is only 35 ; with 1.33 per cent, of tin it is 50; and with 3.2 per cent, of zinc, falls to 59. Strangely enough, the addition of 1.22 |jer cent, of silver — the best conductor, so far as we know at |)resent — reduces the conductivity' of pure copper to 90. It is thus proved that the conductivity of pure copper cannot be augmented by artificial means, but that, on the other hand, the presence of any foreign substance, to however small an extent— no matter what its own specific conductivity maj' be — always has the effect of increasing the electrical resistance. It .seems at first sight a curious anomaly that the resistance of a metal is actually increa.sed by incorporating with it another metal possessing a lower specific resistance, but such is the case, cjuitc apart from how low the resistance of the latter material may be. Indeed, it can be said that alloys have a ])articular resistance of their own, in no way governed by the specific resistance value of each of their component metals. This suggests * Copper containing any considerable quantities of arsenic is, moreover, rendered too hard and brittle to be drawn into wire at all. Arsenifcrous ores arc, indeed, quite out of the question tor electrical conductor purposes. -^v, — ,- 2l8 SUBNfARINE TELKGRAI'HS. that a distinct chemical and consequent |)hysical chan^^e occurs, due to the mixing; of (hfferent metals. The alloys of copper, besides h.'ivin^ such a damaj^in^ effect to electrical conductivity, appear also to lower its mechanical properties, inasmuch as ini]. ire is not as extensible .is pure copper — breaking socjncr, in fact, under a strain.* Copper is met with in the lar{j[est cjuantities in Chili, Japan, Australia, Cuba, and Canada, and stf in small quantities in Cornwall, Devonshire, the island of Anglesea, and in Ireland. Most of the copper u.sed for electrical conductors, however, comes from either Chili, Au.stralia (Hurra- Hurra), or Canada (Lake Superior), particularly from the latter, as it is found there in nature in the metallic state. Kor this reason. Lake Superior copper is generally spoken of as " native metal," the jjreparation in smelt- ing and refining being comparatively small. Copper — like other metals — is, however, usually found as an ore ; and the most common ore of copper is copper pyrites, a yellowish (jre, being a combination of suljihur with Ton. Other copper ores are, of course, met with ; such as those in which tin and nickel are amongst the alloys, and in which oxygen is present in large quantities. Copper is so found in Australia (Hurra-Hurra) and in Chili. In the processes of copper refining, good results, in the way of softne.ss and its accompanying ductility, are, however, obtained by the acklition of a small quantity of lead or tin, and this is explained by the following experiment of Dr Matthiessen's. A sample of copper, when melted and exposed to the air, gave a conductivity of 87 ; on adding i per cent, of lead or tin, and remclting in a current of carbonic acid gas, the con- ductivity rose to 93 ; but at the same time the residual quantity of lead or tin was found so slight as to be scarcely traceable. It seems that the lead or tin, as the case may be, reduces or drives off the sub-oxide of copper, leaving the metal relatively purer than at first. * Theoretically, at any rate, the copper conductor should have a stretchint,"' capacity as high as possible, in order to approach as near as may be that of its insulatinjr sheath. When a strain comes on the core, the insulating material stretches to an almost unlimited degree (especially if composed of india-rubber), and when once the conductor ceases to stretch also, it has to take the full force of the strain. Again, whereas gutta-percha or india-rubber return to their original form (especially the latter) on account of their elastic qualities, the copper conductor maintains its elongated length, and is, therefore, liable to knuckle through the insulation at any spot. Owing to its lessened rigidity, as compared with a solid wire of same bulk, the strand form of conductor avoids this defect to a certain degree. The above were, however, some of the original causes of failure in the earliest cables, from which experience has been gained since the Hoard of Trade Inquiry (alluded to above) concerning the construction of cables. Illl. CONDIKTOK. 3IC/ ICi^lit sampk-'s of commercial copper obtained from various sources, which were experimented on by Matthiessen, fjavc measures ofconductivity varying;; as mucli as between 98.78 and 14.24; tlie chemical analysis of which revealed, in the different instances, traces of silver, lead, iron, nickel, antimony, ar.sem'c, and sub-o.\i(le of copper, as the ca.se maj- be, and in \erj- dirferent degrees. The sample at the head of the list in order of conduc- tivity contained traces of silver only ; the last but one, whose conductivity was 59.34, came from the Demidorff Mines in Russia, and the last one from Rio Tinto in Spain ; * both the latter contained only arsenic, the Demidorff samjjlc having a mere trace, and tliat from Rio Tinto 2 \)cv cent. It was f(jund, again, that, apart from tlicir nature, the greater the number of ailoj's in mi.xture with coi)])er the greater the decrease in conductivit)' ; and, what is also natural from the foregoing, the greater tlie proportion of the alloys with the pure metal, the less •■. ill be the resultant conductivity, as has, indeed, already been demonstrated. In conchifling his rejjort, Dr Matthiessen ])ointed out the desirability of securing, for submarine cable conductors, the ver)' purest co])per obtain- able in the market. He further .shewed that, in order to secure this, the surest plan would be to specify in contracts that the co|)j)er should )-ield a certain conductivity. Thus, it would be t(i the manufacturer's interest to suppl)' the purest co|jpcr, for otherwi.se he would be obliged to pro\ ide a greater bulk of copper to make up the required conducting power, which would i)robabl\- not be to his advantage. Hitherto the only require- ments that it was customary to specif\- were that the conductor .should be up to a given gauge, trusting to the contractor for the purity of the copper. As has been shewn, the electrical conductivity of copper, or of an\' metal, is governed both by the degree of purity of the metal (as well as by the nature of its composition) and also by its sectional area. As a matter of fact, both of these factors require to be specified for — the one as much as the other. If the specified conductivity is secured by a larger-sized wire, it will be accompanied by an increa.sed electro-static inductive capacit)-, unless the dielectric be correspondingly increased. Thus, b)' securing the purest copper, the bulk, and therefore the electro- static capacit)-, is reduced to a minimum — and in the most economical fa.shion — for a given conducting power, and for a given thickness of insu- lating covering. The result is that nowadays the gauge, as well as the * The conductivity of tills ore is, indeed, no higher than that of iron. The same remark applies to some other coppers wliich, like this, contain large quantities of other metals and metalloids, such as arsenic, lead, iron, and nickel. O 220 SUIIMAUINK TKI.KCJKAI'JIS. electrical coiidiictiv it)' t>f the wire, is tested on nirival at tlie cable lactiiry, as a check on the wire-drawers. Moreover, as a further and more accurate check (111 the material, and for additionally calculating the diaineter, the \vei},du of each hank of wire is also measured. The ^'reat, thouj^di },fradual. improvements m.ide in the conductihilit)' of copjjcr within recent years — since the establisiiincnt of subinarine teie- j:fraphy — is largely due to the advances made in smelting' and in refininj; to a complete state of reduction or purification. The cor lujtixity of copjjer metal after smelting is, however, a ^'reat deal below what it is afterwards made to attain by the wire-drawers. The principal means of raisin<; the conductivity is by the after-effect of heat in annealiii}; the wire ;* but there are other mean.s taken which arc sacred to the w ire-drawer. This particularly applies in the " best selected " (or " e.\tra smelted") copper, as prepared at the smeltin^r works of Messrs Vivian and Sons at Swansea, where verj" lar^e (piantities of the Lake Superior copper are dealt with — /.(•.. electrolytically refined — this bein^^ |)robably more lar^^ely emploxed in the crude form for electrical conductors than an)' other ore. This copper has onU' S" per cent, conductivit)' in its original state, but is worked up to what it is at the ))resent time b\' the wire-drawer and metallurj^ist. As a matter of fact, almost absolute!)' pure co|)per is now produced on a larj^e cominerciai scale, though onliitniy commercial co|)per still has a conducting power as low as 30, compared with pure copper at 100. What is known as d it nea li'd w'wc '\^ that which is " annealed," or made .soft,t after " drawing." The last operation (in this country mostly performed at I^irmin^diam) actuall)' strengthens the copper somewhat — laterall)-, at an\' rate — but the process of annealing; reduces it again t(j a point far below what it was oriijinall)'. With copper,^ annealing consists of heating finst and then cooling suddenly — by plunging into cold water, or by some other means. For electrical conductors the operation is neces.saril)' a]jplied after the cop|)er has been drawn into wire; partly because if done before, the copper might become too much weakened to permit of successful drawing into wire, as well as for the reason that the subsequent hardening effect by drawing would, in "■^ The beneficial effect of annealiii),' copper so far as its electrical conductivity is con- cerned—was first observed by I)r Matthiesscn, diirinj,' his exhaustive experiments already alluded to. He then found that after being annealed the conductivity of the same sample wire had increased by 2\ per cent, over what it was when in the hard stale. + Copper when annealed will allow of a dent being made on it when using only moderate force. ;; '. ■:■:-.'. .' % In this respect unlike iron and other metals. ' ;' TIIK CONDUCTOR. 221 this instaiicf, Il-iuI to reduce the conductivity a^'aiii to somethiiij,' like its original fij^ure. The jjroccss of anneahnjf has a wcakeniii}; cflect on an>' metal, reducitij; its tensile stren^^th to nearly half what it was before, (ireat lon^dtudinal strength is not, however, aimed at for the conductor of a submarine cable, where the sheathin;^' wires are intended to take all the strain. The purest copper is obviously that obtained by electroljsis — /.(•., depositing; copper (obtained by an electrolytic system) in a trou{,di from, siiy, a number of dynamo machines. Such a method has tiie disadvantatje, however, of slowness and costliness, and is not, therefore, much favoured as \-et for practical work on an\' l,irjj;e scale.* .Nowadaj's commercial copper is readily obtained, which };ives a con- ductivity etjual to 97 per cent, (and over) of that of the pure metal.+ American (Lake Superior) copper is remarkably free from objection- able impurities, and )'ields one of the highest conductivities; so doe.s .Australian (Hurra-Hurra) copper; and perhaps still more the co])per from Chili, as well as that from Japan. in Hurra-Hurra copper, however, one of the impuritL-.i is bismuth, which is difficult to separate from the ingots, and is almost as objectionable as arsenic. It frequently hai)]jen.s in the present day, with the various samples obtainable, that by the test calculations the wire under test gives higher conductivity than that afforded b\- the standard, owing mainly to the latter not really being .so pure as what we are now able to obtain commercially.* In fact, electro- deposited copper wire made according to the IClmore process has on the average a conductivity (|uite 2, or even 3, per cent, above that of Matthies- sen's standard. The ultimate conducting power (and, therefore, the resistance) of an ordinary copjier wire depends very much on tlie drawing of the copper into tlio form of wire. Compression naturally has a tendency to harden the * This method is, on the other hiind, exclusively ado|)ted for makinj; tlic sin;dl quantities of absolutely puie copper rci|uired for electrical standards, and experimental laboratory work K'-'H'-'rally ; moreover, it was the means by which Matthiessen obtained his standard of ])ure copper. t On the first Dover-Calais cable of 1850 the conductivity of the copper conductor was as low as 30. On that of the 1857 .'\tlantic it was exactly half of what is quite ordinarily obtained at the present time for electrical conductor purposes. Thus, as the signalling speed attainable on a cable is directly proportional to the conductivity, a cable of to-day of the same dimensions would be capable of cariying just double the number of messages in a given time. This would imply double the earning power— a consideration which naturally appeals to the investor. I This, of course, points to the desirability of a fresh standard of pure copper being established. 222 SLHMARINK TKLliGKAl'IIS. copper, and this again has the effect of reducing its concUictivit)-. This effect ma)" be accounted for by the increased ri^ndity of molecules thereby produced, just as the process of annealing renders the molecules more free to move in respcjnse to any electrical strain.* Tests and Calculations. — Electrical measuring instruments are usually arranged (for greater convenience) to give the value of a quantity which is the reciprocal of conductivity.+ This quantity is termed ■' resistance." Tiie relative conductivity- C of a wire, referred to that of pure copper which is represented by the number lOO, * may be obtained by multiplying its calculated resistance p (on the basis of purity) by loo, and dividing the product b\' its actual (observed) resistance ;'. Thus: — ■"■'■■'■■■'"''''■"■■■ r The specific resistance of pure copper, or the resistance of a cubic centi- metre at o C. = .00000164 ohm ; and that of a cubic inch at o C. = .00000063 ohm. The resistance of 1 foot of pure (soft) copper wire, weighing 1 grain at a * In 1883 Mr W. H. I'rcecc, C.B., F.I<..S., read a very complete paper on the subject of "Electrical Conductors" before the Institution of Civil Engineers. This paper, with the discussion thereon, gives very full information regarding the diflercnt |)hases of copper and other metals for conducting purposes. More recently, Mr lUicknall Smith's hook on "Wire" (published by liiii^ineerini::) has furnished a great deal of up-to tiatc matter con- cerning copper wire, as well as an exhaustive description of the process of wire-drawing, which, it may be remarked, is somewhat out of our scope, even if thi- necessary space were available for treating with the subject. + However, some years ago, Lord Kelvin had bo.xcs constructed for joining up con- ductors in parallel in different ways, so as to give direct measurements of conductivity in different substances. He gave the name of " mho" (ohm spelt backwards) to the unit of conductivity in the Hritish Association or H.A. system of st.mdards and units. X In practice— for commercial purposes — the conducting value of copper wires is always compared with that of a pure wire of the same metal as the standard, the latter being, therefore, taken at 100. I5y this means — instead of silver (of the highest conduc- tivity) being the standard — an idea of the purity is also implied, though degrees of purity and degrees of conductivity cannot by any means be said to go hand in hand, in con- sideration of the fact that the merest trace of arsenic reduces the conductivity of a pure (100 per cent, conductivity) copper wire to 60 per cent. This is the most striking example, but in no instance does the degree of effect in conductivity accord at all closely with the degree of alloying. A copper wire may have a 90 per cent, purity and yet (owing to the 10 per cent, impurities being, say, partly composed of ajscnic; its percentage of conduc- tivity might not be more than about 30. Thus the percentage purity of copper, as deter- mined by chemical analysis, cannot be relied upon as strictly indicative of the percentage conductivity. Moreover, the electrical test for conductivity oftCn gives a more accurate insight into the degree of purity than can be attained chemically. TIIK (.ONOUCTOK. 223 temperature of o° C, bein|^ .2064 of the legal ohm,* that of a wire haviiiij a lenjj;th / exiircssed in feet and weiLjhin^ re <^rains, will be — .20 64 X /- 1 ~ w The conductivity, therefore, of a wire at o' C. /feet long and weighing ^v grains, with a measured resistance of /- ohms, will be — .2064. x l- The resistance of a naut (N.M.);J: of pure copper wire, or strand, weighing I lb. at a temperature of 75' F. is taken as 1 196.7.^ I*>om this the resistance per N.M. (/■) of any other pure copper wire or strand weighing 7V lbs. becomes .=ii9^at75F. where resistance per N.M. multiplied by the weight equals resistance ])er naut ijound. The resistance per naut of a cable conductor at 75 V. is in fact, roughly speaking, equal to 120,000 divided by the product of the percentage con- ductivity of the copper and its weight per naut, in pounds. It is also equal to the resistance of a naut-]Jound corresponding to the particular percentage ccjnductivity divided by the weight in pounds per naut. Thus, thn resistance of a wire of given material varies directly with the bulk or area — i.e., decreases with the square of the diameter. For instance, if the diameter wire is doubled, the resistance will be a quarter what it was, and the con- ductivity quadrupled. Moreover, with a given iy!»<:«_/?f resistance — ?>.,vvith a * The legal ohm— or ohm, as it may be termed — is equal to 10" C.G.S. units (centimetre- ;;ramme-second electro-magnetic fundamental unit system) of resistance. It has now been agreed to take, as the practical unit of resistance, the resistance of a specified colunm of mercury (H.A. Committee on Electrical Standards, 1892 ; Report of Electrical Standards Committee of the Hoard of Trade, 27th October 1892). To obtain the relation between resistances measured in 15. .A. units and resistances measured in ohms we have : — •■ I IJ..'\. unit = .9866 ohm. I ohm = 1.0358 B.A. units. Thus to reduce H.A. units to ohms, wc have to multiply by .9866 — i.e., deduct 1.34 per cent. t The explanation of the variation by length being as the square in this formula, rather than merely directly as the length, based on unit proportions, is as follows: — If a unit foot-grain of copper be drawn out to double its length, its section will consequently be halved over the process. The result is that the resistance will be not only doubled, on the score of the length being doubled, but will be again doubled owing to halving the section of the wire. + Throughout this book either the term "naut" or the letters "N.M." are used in abbreviation for " nautical mile " in place of the oft misapplied term " knot," which is in reality a rate— representing a nautical mile per hour. S The equivalent at 32' F. ( = 0' C.) is 1091.22. 224 SUBMARINE TELEGRAl'HS, given quality of material and conductivity — the resistance of a wire varies inversely with the weight, and consequently the conductivity directly with its weight. The percentage conductivity of an>' wire may be found by multiplying the resistance calculated for a pure wire of the same length and weight at the same temperature by lOO, and dividing the product by the resistance of the wire as measured. Matthiessen's standard was a pure annealed copper wire lOO inches in length, possessing a resistance of 0.516 ohms at 60' F., and the conductivity of this wire was taken as 100. Thus, the conductivity of any other wire, in relation to this standard, may also be determined bj" taking a standard having a resistance (o. i 516 w) equal to 100 inches of the above pure co])per wire, weighing 100 grains at 60 F. The conductivity of any other wire again but of similar resistance will then be as the square of its length in inches, divided by its weight in grains. Influence of Temperature on Electrical Resistance. — Becquerel shewed that the electrical resistance of metals increases with a rise of temperature. These variations were measured in 1862 by Matthiessen and Van Bosc, who, after numerous experiments, were able to state the following formula, the conductivity of a metal at o" C. being represented bj- 100, and C. being its conductivity at any temperature /, ■ : - :, . 7= \ooxaf+iit-, a and fi being positive or negative constants for different metals, according to circumstances. For copper — , - c „ ' ' ., ' ■•,•■ ,.,.;:..■:■.. ,;'. —= 100 — O.387U I / + 0.0009009/-. •/ The resistance offered to a current of electricity through any conducting wire varies, in fact, in proportion to the temperature, more or less according to a logarithmic curve, t.e., by compound interest. This variation is different for different metals — though in the same direction — and is largely dependent on the purity of the metal. The con- ducting properties of alloys are very much less influenced by temperature than in the case of pure metals. Moreover, the former are not effected to any great extent by exposure to the atmosphere. The resistance of copper and all the metals increasing with a rise in temperature and vice versd is possibly due to the changes of density thereby produced, thus possibly a'^ording a more perfect conduction at a low than at a high temperature ; though it must be admitted that in the former condition the molecules are more rigid — />., less free to move — and can therefore only act inductively on one another. THE CONDUCTOR. 225 The tests which submarine cable cores uiiclcrj^o diirinj^ in- it liiis been proposed to rejjlace copper f(jr tele<;raphic and telephonic purposes by silicious bronze, which has about the same conductivity as commercial cojjper, and much greater tensile strength. This |)roposal — like that of aluminium and aluininium bronze — mainly applies to aerial land lines, where it has alread)' been put into force in place of iron as well as copper. It has, howe\"er, also been sugj^estcd for submarine cable purposes. In this latter application the idea is that the iron sheathing mi,i,dit then be reduced in weii.jht — i.e., smaller wires, cheaper type, and less of them — which would have the effect of les.sening the cost of the cable, besides rendering it easier to lay and repair.* * M. Vivarez, on the basis of the weights of copper and }.;utta-percha forming the core of the F'rencI) Atlantic cable, has drawn up the following specilication for a deep-sea I'er nautical mile. cable with a silicious bronze conductor .Silicious bronze Gutta-percha Jute 28 iron wires of No. iS H.W.n. Hemp and comjiound 'iotal weij;ht in air - - 2,710 — 1.2 tons. .Such a cable, about I inch in diameter, would weigh 0.3 ton in water per N.M., anil would resist a tensile strain of 2.8 tons, half of which would be taken up by the conductor. It would, therefore, be strong enough to support nine miles of its own length hanging vertically in water, {/.eitschrij't fiir Elektrotcclinik, 1.S85.) I'ounds. 485 397 176 1,102 550 EasRrn Telcgra|)h Company ; (librallar Station. tiik condlctok. 22^ Section 2.— Thk Conductinc; VVirk. Comparative Features of a Solid and Stranded Wire: Ultimate Reasons for the Latter Form. —The conductors of the earliest submarine cables were composed of a single solid round wire, usually No. 16 H.W.G. = .065 inch in diameter. This, the simj^lest form, is also at first si^ht the most suitable and economical, presenting, for !j;iven volume, the smallest possible surface area. In the case of a sinj^lc .solid wire, the weight of insulating material required for covering the conductor with a given thickness, and the electro-static capacity of the cable, are both kept at their lowest for equal weights of cojiper.* Thus, in obtaining a certain result, the cost of manufjicture is less than can be the ct.c with any other form of conductor ; or, to put it in another way, as the speed of signalling attainable is in inverse ratio to the electro-static cap' involved in the case of an (ordinary equal-wire strand may also be reduced either by drawing' the finished strand through a die, and thus conipressint; each w ire aj^ainst one another,* so as to fill up the interstices, and thus reduce the outside circumference of the entire strand ; or else by fiUinfj u]) the inter- stices by wormin},' them with intermediate fine wires in the process of stranding, as already shewn. Where the iii^ulation of a submerged cable is imperfect at some point or other, the positixe current, passing from the copper to the .sea, decom- poses the water and the salts in .solution ; .soluble chloride of copper is then formed, which is carried off b)' the water as fast as produced. A negative current sent through the conductor forms a deposit on the copper in contact with the water, of hydrogen, .sodium, etc., which are, electrically, positive components of water ; anj- solid substance in contact with the conductor is reduced and free hj-drogcn given off, the bubbles of which enlarge the hole or fissure through which the gas escapes. In either ca.se aggravation of the fault ensues. The rapid succession of signals through long .submarine lines unfortunately involves the use of alternating currents, the combined effects of which tend to bring about the destruction of the cable all the more quickly. t As a remedy- for this, the late Mr C. V. Varlej- propo.sed placing a fine platinum wire in the copper strand to maintain continuity in the event of the cop|)er conductor being entirely eaten away. This device has not, however, in an\- instance been turned to account. Formulas and Data.- The weight per naut of an)- round copper wire is about lbs. subject to its degree of purity ; and for a strand of the ., ^^ .same '-- lbs., where (^j' is its diameter in mils. ;;J in other words, the weight 73-3 of a naut of copper strand wire varies as its .sectional area or bulk, ^ divided by the numerical expression 73.3. l! ■"" rii()U}.;li the compression of the wires together will naturally have the effect of harder.ing the copper, thereby seriously reducing its conductivity, this may be subse- quently corrected by the entire strand going through the process of annealing— i.e., softening by heat and then, in the case of copper, cooling very quickly. t In practice, however, this has never been found to be a serious matter. + I mil. = loVcth of an inch. S This, however, can only be regarded as an appro.ximate method of arriving at the weight of a wire, depending— as it does— so much on the density (or specific gravity) of the metal, as well as on the lay and power of " gauging " a strand. 11 Where possible, however, the weight should be ascertained from actual test measurements rather th;in l)y calculation from tlie diameter, except as an extra check. This measurement may then form a suitable basis for subsequent calculations — amongst aja SUHMARINK TELKCRAPHS. The diameter of a coi)pcr wire ueij^hin^ 2i> lbs. per naiit is about 7.1 ^tv . . . mils., and for an ordinary, equal wire, .strand, 8.1 Jji> . . . mils.* The first of these varies fas in the weijjht formula) with the decree of purity ; the second also addition; My with the formation of the strand — i.e., its layf — and the amount of compound incorporated therein. It may be again remarked in this connection that more reliable and accurate data will be .secured by calculatinj.? the diameter from the weight — where the latter is .iccessible — than b)' arriving at the weight from the 12 per cent, greater in a strand than in a so/it/ wire for the same weight of copper, with a proportionate increase in the inductive capacity, and, consequently, also a corresponding decrease in the signalling speed. With the Siemens combination solid-strand conductor (as a mean between the two) we get a 5^ per cent, decrease on the diameter and capacity, resulting in the same increase of speed — an advantage which should represent something material in a long cable, where the electrical constants become more and more serious items with every slight increase in length. + The shorter the lay the greater becomes the area, and consequently also the greater the inductive capacity. I When the diameter is doubled, the area (rP) is four times what it was. Tlius the power of conduction is also quadrupled, its resistance being a fourth. In fact, the conductivity varies directly with the sectional area, and the resistance correspondingly varies inversely with the area. Till: CDNDLCTOK. 233 the same time increase the ca])acity, unless the thickness of the dielectric be sufficiently increased also.* For this reason, also, it is essential, to start with, that the reduction of the conductor resistance to a minimum be effected, as far as possible, specifically — i.e., by the very purest of the highest conducting metal beinjf employed. However, apart from this rule (which is a sine ijud noii, and means economy in the end), increasing the size of the conductor is, in practice, more beneficially effective as rej^ards the conductor resistance than it is the reverse a.s regards capacity. It is, indeed, more economical to attain a high working speed by a low conductor resistance than by a low capacity. In the former, the conductor alone is involved ; but rn the latter, in order to obtain the same degree of effect, the thickness of the dielectric has also to be increa.sed, and it must be remembered that, whereas copper costs about /d. a lb., gutta-percha (the usual substance used for insulating submarine cables) costs .somewhere between 3s. and 6s. a lb., according to the state of the market at the time. Thus, the usual recognised policy is to adopt a dielectric of just sufficient thickness to ensure mechanical safety, according to the type of conductor used ; and the speed is got up to the required degree through a given length by the conductor being made of sufficient .section accordingly.! Quite recently, in answer to the ever-increasing demand for trans- Atlantic telegraphy, it has become necessary not only for the com])eting companies to lay extra cables to meet the contingency of break-downs, but also that these new cables shall be rendered capable of working at a higher speed — effected by mechanical transmission. To meet this, the core of the last two Atlantic cables (of 1S94) arc, in each case, of a much heavier type than anything hitherto adopted for submarine telegraph purposes. In the case of the new " Commercial " cable core it is, in fact, composed of a type represented by 500 lbs. copper per N.M. to 320 Ib.s. gutta-percha; and the core of the last " Anglo " cable is constituted by as much as 650 lbs. for the conductor to 400 lbs. for the gutta-jjcrcha insulating envelope. Inasmuch as there is practically no limit to the speed afforded by the * Hy doubling the diameter of the conductor, the capacity is doubled where the thickness of dielectric is built up to exactly wliat it was previously. Thus, niiiinly on the score of the heavy cost of the dielectric material, it is essential that the rei|uired low conductor resistance shall be secured as far as possible specifically — /.*'., by copper of the highest conductivity — rather than by a large area of wire, as well as for mechanical reasons. + The only factor which places a limit on the e.\tcnt to which this principle can be pushed is that of fault liability. 234 SUHMARIM. tki.i:c;kai'IIs. various forms (»f Whcatstonc automatic transmitters — up to, sa)-, i.coc) words per minute — the dimensions of the core (where warranteil In- tin- traffic) mi^'ht be still further increased so as to (,Mve the cable a still liij,'lier eariiin[^ capacitj', but for the alread)' enormous initial cost of a lon^^ cable, and tile ^reat increase of the same therein- entailed.* Initial Tests previous to Manufacture at Cable Factory. The C')|)per \vire+ arri\-es at the caljle racli>r\- in iiaidxs or bundles of \-aryin^ size, wei^hin^ froni some 15 to 70 lbs, the length beinj;' from ] to 3.I miles or more, according to the tjpe of wire. With a view to having as few joints as |)ossible, the wire is required in the longest len^;ths the wire-drawer can produce, with a jjropcr regard to convenience of carria^^e.* The weight and j,'au};e of the wire on each of these hanks is measured on arrival. A sample leiifjth is then usually cut off 10 per cent, of them, which is carefully tested for weight, diameter, and specific conductivitj-. At certain factories the practice is for the samples to be 30 feet in length ; at others 12 feet only is cut off. In some ways, within liniits the greater the length the better. The.se different measurement.s, besides acting as a check on the u ire- drawer {to .see that the wire .supplied comes up to specification in each particular), also act as a check on each other. It is, in fact, essential that the conductor should be true to measurement in every respect. Thus, if the conductivitj' were up to specification, but the diameter of the wire were larger than what was specified, when made up into .strand the electro static capacity would be too high on this account; moreover, with the weight specified for the dielectric, its thickness (to cover the increased conductor area) would be less, which would be the cause of a still further increase in the capacity, besides prejudicially affecting the mechanical properties of the core. Again, if the diameter were correct, but the weight were not, ■■'" If, however, the dimensions of the core be further increased so as to yield a still hij,'her working,' sjjced — or to obtain the similar speed on a greater length - it is certain that the weight cf the cable will hv so much augmented by the increased nimiber of sheathing wires involved, that it will become necessary to modify the existing form of paying-out machinery so as to maintain sufficient control over the cable during paying-out operations. Moreover, designing a suitable type for laying — and still more for recovering — in dee() water would, if this principle be pushed much further, become no easy matter. + If for an india-rubber core, the surface of the copper «ire requires to be efticienth tinned, to prevent any sulphur which may percolate through the inside covering of pure rubber acting on the copper, as e.xplained elsewhere. J With the comparatively small wires used for stranding in telegraphic conductors, the length in wh'ch they can be supplied by the wire-drawers is, as a rule, in no way restricted by the limit of length which a single bar will produce, but only by considerations of portability, and. more especially, by the weight admissible foi- each bobbin of the stranding machine, of a universal type for all subr.iarine conductors. TIIK CONnUCTOK. 335 tin's would ill itself imply tli.it the metal was ii<>t to specification as re^'ards conductivity owiiij; to a discrepancy in tin- (piality — />., purity — of the copper used. l''or this reason, it would verj- likely be also wanting in tenacity.* Thus we see that all of these points re(|uire specifyint,',"'" and that tests for each should be made — partlj- as a check on one another. The conductivity must, of course, be specified and mea.sured, for it is on the b. — Pcrcha has also been said to be merely the name of the particular tree. + According to Dr Werner Siemens, he suggested the use of gutta-percha as an insulating medium to the Prussian (iovernment tw j years previously to P'araday. nil', IXSn.ATlNG KNVPXOl'K. 249 wire on an extensive scale in a thoroughly permanent, uorkinanlike, fashion, ill sii':h a way that it could be relied on to stick to the wire. It was thought that whoever attained this u ith either ^utta-percha (which received the most attention) or with india-rubber, would make larL,^e quantities in answer to a probably extensive demand. The first attempts, however, to insulate wires with Ljutta-i)ercha were not, by any means, attended with immediate success either in this country or in the German iMnpire. This was, no doubt, principally owintj to the defective form of joints adopted — that is to say. the j^utta-percha was rolled round the wires in spiral, or lonjjjitudinal, strips, thus necessitating a con- tinuous joint between each strip, which probably had insufficient adhesion, and would, after a short time, <;ive out. The first ])atent in this country in which gutta-percha was proposed to be used for insulating purposes was that taken out in 1848 by Messrs Harlow and Ff)ster, in which several wires insulated from one another were drawn between two sheets of a compound of gutta-jjercha, New Zealand gum, and sulphur, which were pressed together between two rollers. The .sheets were, however, ne\er properl)- united ; moreover, the gutta- percha was not sufficientl)' purified of the wood contained in the raw material as it came from the tree.* Mr Charles Hancock, in the same year, patented a gutta-percha mi.xture for covering wires, consisting of gutta-percha mixed with muriate of lime, pas.sed between heated cylinders and sprinkled over with rosin. This patent also covered a mi.xture of gutta-percha, shellac, and borax as an insulating" compound. Neither of these branches of the above patent were, however, turned to anj- practical account. Messrs Siemens and Halske certainly appear to have been the first to use gutta-percha for insulating conducting wires on any extensive .scale, and to have eventually brought the practice to a succe.ssful issue.f First Die-covering Machine. — According to the late Ur Werner Siemens, he, in 1847, first devised and introduced a machine for covering * Harlow and Forstcr's patent was followed in the same year by one somewhat similar taken out in the name of John Lewis Ricardo, as chairman of the Electric Telegraph Com|)any. This was adapted to some extent for subterranean lines. Moreover, a submarine line, insulated according to this system, was laid in I'ortsmouth Harbour by the "Electric" Company: this did not last long, however, owing no doubt to the continuous joint between the seams. t One of the principal features discovered in connection with gutta-percha was that it is capable of being laid on a wire to a required thickness ; and, when heated, tliat it becomes plastic. It can then be easily worked into any shape, and will remain firmly in that shape when cool. S 2SO SUHMAKINl'. TKI.KlikAPllS. wire with gutta-percha (rendered plastic by heat), pressed round the wire through a cylinder and die without a seam, thus obtaining a homcjgeneous covering, thereby avoiding the continuous joint existing throughout the length of previously made core composed of gutta-percha strips. Siemens described it as being similar to a macaroni machine, and it (together with Bewlej-'s tube-making, or lead-pijjc drawing, api^aratus of 1845*) ^^'i^ undoubtedly the germ of the gutta-percha covering machines as we now have them in a perfected form. Owing to Siemens being at the time a Government ofF:er (lieutenant in the Prussian Artillery), no patent was taken out for this machine in England till 1850, when ;Uso a slight Improvement was effected. First Gutta-percha Underground Telegraph Lines. — In 1.S47 Werner Sieincns laid the first gutta-percha covered underground telegraph line between Berlin and Grossbercn. This was immediately after Mr C. W. Siemens (subsequently Sir William Siemens) had .seen Dr Montgomerie's specimen of gutta-percha at the Society of Arts, and had suggested to his brother its possible utility for purposes of insulation in place of india- rubber, with whicli the line was to have been covered. Everything tends to show that Messrs Siemens are at any rate fully justified in claiming priority in covering wires with gutta-percha in such a manner that no seam was involved, with a machine specially devised by them for the purpose. In 1848 and 1849 Messrs Siemens and Halske obtained contracts from the Prussian Government for making and burying many hundred miles of insulated conducting wires throughout the kingdom of Prussia, thus demonstrating for the first time in that country the practicability of sub- terranean telegrajjhy on an extensive scale. The lines did not, however, last long. This was, in some cases, owing to the admixture of sulphur with the gutta-percha insulating envelope — the sulphuretted gutta-percha being sui)plied by the Gutta-i)ercha Company- -and also to the lack of experience and perfection in the joints and general maiuifacture.f * Henry Bewley was originally a Iead-pii)c drawer, Init joined the Ciutta-percha Company, for whom he applied the above machine to making gutta-percha tubes, bottles, etc. This was not, however, used for covering conductors with gutta-percha till 1847, and again in 1849 over the first Channel submarine line, laid the following year. Previously this company had, for over a year, applied the gutta-percha to connecting wires in strip form only. It was more than ever necessary that a single, complete, seamless covering should be employed for any line deposited at a certain depth under water. t These gutta-percha covered lines were protected by a leaden pipe, and were laid under the curbstone and gutters. The lead was gradually eaten away, and the gutta- percha desiccated. Ultimately, in 1853 and 1854, these lines were replaced by bare overhead wires, on earthenware insulators, attached to poles. IIIK INSILATINC. ENVEI,OPK. 251 First Subaqueous Gutta-percha Insulated Line. — In 184;-' Messrs Siemens laid under water one of these seamless gutta-percha covered wires in the i'ort of Kiel, forminj^ a part of a submarine mine system — sometimes less aptly termed a " torpedo system." Another short cable (quarter mile) in which {jjutta-percha was employed for insulation, is said to have been laid by the above firm the followinff year across the Rhine from Dentz to Cologne. About the same time the Brothers Hancock and the Gutta-percha Company were doing their best in this country to design some machine that would lay the material on the wire in a more homogeneous maimer than that of strips or spirals, as hitherto. No pronounced or lasting success in this direction appears to have been recorded here till soine time after Siemens' German lines had been laid ; though a considerable cjuantil}- of wire was covered for railwaj- tunnels, and later, for the lines laid in iron pipes under the streets of towns.* Experiment in the English Channel. — In i(S49 Mr C. V. Walker (electrician to the South-Kastern Railway Company) laid an experimental telegraph line in the English Channel. Full particulars of this venture have already been given in Part I. It suffices here to say that it consisted of a two-mile length of a single No. 16 B.W.G. copper wire coated with gutta-percha. The experiment was quite successful, and proved, at any rate, the jMj.ssibility of signalling through a gutta-percha covered copper wire under a certain depth of water. First Anglo-French Line. — In 1849-50 the Gutta-percha Company manufactured the first practical Channel line,+ consisting of a copper conductor thickly covered with gutta-percha by means of a cylinder and * .^ftcr the gutta-percha unclergrnund lines laid by Werner .Siemens (for .Siemens and Halske) on belialf of the I'russian Government, the next complete system of subterranean telegraphs was that of the " Magnetic" Company laid down in 1 85 1 between Manchester and Liverpool along the Manchester and Yorkshire Railway, under the supervision of their engineer, Mr (afterwards .Sir C.) Hright. These lines were laid in the six-foot way between the rails, where they would be least liable to be disturbed. The following year similar cftmmunication was established by the same company, under the direction of Mr Charles IJright, between Manchester and London ; but in this case the lines were laid aldng the public roadway. As a part of the "Magnetic" system, other subterranean telegraphs were laid to dlasgow and also through a great part of Ireland. In 1853 the Electric Company laid their lirst long length of underground line, between London and .Manchester, along the London antl Norlh-Western Railway. All the above underground conductors were insulated with gutta-percha, as in Siemens' lines. They were made at Wharf Road by the then newly-formed (".uttapt.. ha Company, and worked well for a number uf years. t See .'art I. ^■)- siKMARiNK Ti:i.i:(;K.\riis. die machine, thus avoiding;, for the first time in tiiis countn-, any con- tinuous scam in the j;utta-i)Ciclia co\erini(. The faikire of this cable, the day after submerj^cnce, was in no way (hie to any fault in the construction of the ^utta-percha insulating covering of the main (deep-water) part of the cable. However, as regards that ])ortion of the line intended for the first half-mile, the copper wire was covered with cotton saturated in a solution of india-rubber, and enclosed in a leaden tube. This form of insulating covering at the bottom of the sea — even at that small depth— would be quite sufficient to account for the short life of the line, apart from other misfortunes. Dover-Calais Cable, 1850. — The following >ear, the first actual com- plete submarine cable, as at present constructed, was laid between Dover and Calais.* In the construction of this, at the works of the Gutta- percha Company, the six conductors were each covered with two coats of gutta-percha up to a {-inch diameter, under the supervision of Mr Samuel Statham.+ Hitherto the custom had been to apply the gutta-percha envelope in a single coating ; but it was thought that a greater chance of detecting any mechanical "flaws" or incipient electrical faults would result from apphing the required total thickness in separate coats. This plan is now ver)' generally adopted ; indeed, three, or even four, coats (according to the required total thickness) is the usual thing. The general character of the die-covering machine, adopted by the Gutta- percha Compan)- for the construction of these lines, was not unlike that of Siemens. Collection and I'kkpar.vtion. We have now traced the history of gutta-percha, from an electrical point of view, up to the period at which submarine cables were first constructed — as regards the method of insulation — on the same general ])rincii)les as at the present day ; moreover, we have reached the stage at which the gutta- percha envelope was applied in the same general wa\- as it is now. It is not, therefore, necessary to pursue the historic details of each subsecjuent cable core, and we will now proceed to consider the collection and manu- facture of gutta-percha. Before doing so, however, it may be remarked * See Part I. t This gentleman ni.iy l)e said to Ikivc led the way in this country in applying himself to the |)roblem of the manufacture of }iutta-i)ercha for suljniarine cables. In connection with the manufacture of this cable, Mr Statham enormously improved the machinery for the manipulation of the j^utia-percha. 'iiii', iNsrr-ATiNc i:nvki,oi'i;. 253 that fur some ten jears after the iiitnxhictioii of india-rubber and j^utta- percha into this country, and subsequent to the starting of submarine cables as articles of commerce, various patents were taken out for mixing' other vegetable substances with the pure masticated india-rubber and gutta- percha, with a view to beneficially effecting or preserving the material, and also from a point of economy ;* but certainly as regards gutta-])crcha, they were, without exception, a distinct failure. As a matter of fact, the purer the gutta-percha, the better article it is physically and mechanically — moreoxer, the higher and — what is m// fvmn Ikiiica, whirli htis much in common with the Pnvfiiit Iccni. ()f thi- remaininL;- L;uttiters, tlio.se which are tolerabl_\- well known ;md cl.'issified, such tis the " nialoeh bahim temha^ti cU: soepayaiiL; " and the " njatoeh balam docritin de socp;i\an;4"," ])roduce ^utta of only inferior qualitv, slick}- when Wtirni, and soft enough when cold to he indented with a thither nail. The n;iti\t's of !5orneo .wIumi- /soiidiii/rn giiL'ti is now mainly met with) min;^le the Stii)iVom some of the nei^hliourini;' tri'es with th.it obtained from this tree, either as ta suijplement or as an .•idulterant. .Sometimes saps from as nitin}' as the different species are thus mi.ved together to ni.'ike u|) the ordinary commercial "^iitt;i tab.an " * as we j^et it for most purposes, amoni^st others, for insulating electrical conductors. f Seat of Growth, and Appearance — (niltti trees arc nowadays only found in the densest p.irts of the \ ir_L;in forests, where the i^utta-seekers discos er them with mar\ellous skill. The)' .ire guided, ,is to species, by the colour of the trunk, the thickness of the liark, or in- the hardness of the wood. Occasionally they make a cut in the bark and test the tjuaiity of the St'ip which trickles out b_\- working it between their fmj^^ers. When the verdict is satisfactory, the tree is felled with .in a.\c, the toj) also bcinj; sometimes cut off to |)re\-ent the s.ip diffusinj^ throuj^h the 'e.ivcs .and branches. Collection. — The s.ip is collected in \-arious wa\s in the different parts * " Ciutt.'i tabtin '' is, howc'er, the tcrni often applied e.\ciusi\'ely to the |)rodutt obtained from />ii/ii>/>sis i/s(>/i(Ui//rir) i;u//(i. t The "^rutt.i baton '' described by Mr Seli^'iiiann-l-ui, after his voyage to llic East Indian Airhi])ciago in 1882, appears to be obtained from tlic ralaijiiiuni calophylluiii I'ieric (Borneo), a variety of tlie I'lilaquiuin ohlongifoliiiiii species of tree. In quality this kind is second only to the " KUtta taban," but it is of a lighter and redder colour, somewhat stiffer and of coarser tissue. ll'i.Aii; Wl. l-'iii. S. --C'dUcclion (if iIk' [nice nf iliu honaiuliii Ihit.'a. { To face p- 256. Tin: iNsn.ATiNc; i;nvi;i.(i|'i;. 257 uluTc it is to l)c foimd. \'"\<^. 8 j^ivi's an idea of the collection of tin- ^iitta as it should lu- |K'iToriiu'(l, with the tree iiiidistiirbcd from its root. 'I'he usual plan is, however, to cut the tree down, and after laying' it full lenj^lh on the ground, to cut riiif^js ri^^ht round the bark alonj,' the entire lei,,.^th, at distances of a foot immediate]}- after eolleelion i for examination and exiieriment. lie considers that in this way a fresh source of supply mi^ht be (liscoxered. Collection from Leaves.— M. Serullas, who for m,ln_\- \ears has made a close study of L;utta-percha, sus^gesled a sh(jrt time aL;'o the more careful and s)'stcmatic cultivation of Ljutta-pcrcha, in such a manner as to render it possible to extract the juice from the leaves and twigs of the tree on a large scale, thus obviating the necessity of disturbing the trunk antl of endangering its further growth. The leaves, after being dried, are first ground to a fine powder and mixed with one-tenth of their weight of caustic soda, dissolved in water and heated to boiling ]K)int. So far, how- c\er, it does not ap|)ear to have been found ])racticable to turn this excellent idea t(j account at all extensive!)' for commercial |)urposes, or, indeed, to place it be)'ond the pale of laborator\- interest and ex|jerimental inves- tigation.* Chemical Analysis of Specimens. Again, M. Lagarde has pointed out the advantage of examination and chenn'cal anal}'sis of large s|)ecimens of the raw gum direct from the seat of growth, in addition to electrical tests on the manufactured article when about to be used as an insulator.+ He has drawn attention to the fact that though twcj materials might test much the same electricallj-, the)- ma)- really be very different in their nature, one perhaps containing more water or resin — both a sure source of subseciuent deterioration, if in excessive i^roportion. It would thus seem in ever)- wa)' ■"■ Too liltle of tlie juice could be obtained fror.i each leaf by incisions to make the process worth gonig through. It could, therefore, only be collected by chemical means, introducin},' applications that would proi)ably act injuriously on the t^uni itself. Again, this would involve machinery oi- materials being taken out to the scene of action, unless the whole plant were uprooted and taken home to be operated on an extermination which would prove expensive. The kuter appears to be the only way in which the leaves could be got at conveniently, but even then it would be a lengthy process, such as would increase the scoi)e for early ilecay due to oxidation, partly owing to the substance being brought into a somewhat laminated condition. We must remember, moreover, in this connection, that in certain out-of-the-way places there are only a few trees, and that those which are present often yield but liltle saj)- as is testified by the com])aratively small lumps in which it is often sent hoinc. In any ca^c it is probable that any juice collected from the leaves of the tree woukl be more open (during extraction) to oxidation, and consequent resinitication, than by the ordinary means of collection. t As a matter of fact, it is the custom at all the large cable works to submit samples of gutta to chemical analysis previous to selection. Till", INSILATIXC. ENVELOI'E. j6i desirable — especially from a cliirability |jc)int of view — that specifications for the dielectric of a cable should be based not only on electrical, but also on chemical, tests of the best materials available at the time. Reference for Further Particulars. —Finally, we may add that in the Electrical Reviezv of IJecember 1S90 and January 1S91, will be found a series of interesting and instructive articles* concerning gutta-percha, to which the reader may be referred for further information. Moreover, jirobably before this book is published, Dr Eugene Obach, F.C.S., will have delivered, at the Society of .Arts, a course of Cantor Lectures on the same subject. These will, without doubt, prove both interesting and instructive. * Prepared by Mr K. March \Vebl3, Eicctrician-in-chief at the Silvertown Works. Eastern Telegraph Company : Station at Siuikin. 202 SUHMAKINK TKLKC;UAI-|I.S. Sl'XTION 3. — CJIKMICAI,, I'llVSK AI,, M KCII ANIC.M,, AM) l'Xr.( IKK AL Pkoi'kktiks of (IuITA-I'KKC IIA. Native Gutta-percha. — Iti the i)uiu state, ^utta-ijcrclia is a imjious substance of a inill<)-\vliitc colour, which however resists the ciicroacli of water, and is indestructible by chemical a<;ents. It is, moreover, insoluble in water, alcohol, alkalies, and dilute acids, but extremely soluble, especially wlutn hot, in ether, benzine, chloroform, turi)entine, creosote, naphtha, and ^rcnerally in all resinous licjuids. Strong sulphuric acid attacks it, especially when moderately heated, and leaves nothintj but carbon dust ; strong' m'tric acid chanj^es it into a yellowish resin. As a h)'dro-carbon, having,' the same chemical composition as oil of turpentine fC;^.,!!:,!,;. 't contains :— * Carbon .... 88.92 1 , , , ,, ' parts in 100.00. Il)ilr()Kcn - - - - 11.08 ) When subjected to the o.xy^en of the air, it turns brown and becomes brittle, chan^'ing to a resinous substance soluble in alcohol. This o.\ida- tion takes place more readily in the |)re.sence of li^ht, heat, and especially under alternating dry and wet conditions, or great and sudden changes of temperature.* It is still further accelerated under a combination of all, or an)', of these influences. Absolutely pure gutta-percha can only be obtained by having recourse to chemical methfxls of purification — far beyond that of mastication. As already stated, the material is then absolutely white. This would, however, be much too costly a plan for practical work on anything like an extensive scale, and can, indeed, only be adopted for laboratory experimental work. A small quantity of a certain very su|)erior class of Horneo gutta- percha (almost pure_) is obtained which is cpiite pink in colour. This costly species is principally used for the base of false tecth.t The 'Jele- graph Construction Company, in the early days of submarine telegraphy, imported some of this material from .Singapore, the general Malay market for gutta-percha. * Tims, when applied to open-air conductors exposed to sunlijjht, it rapidly deteriorates, and even cracks off the wire, or ^'radually drops away as so much powder; but when enclosed in iron pipes, or submerged under tlie sea, it is prac:ticaliy indestructible. The degree of effect produced by light is in pro|)ortion to its Jictinicism and intensity. It is independent of the source. Thus the electric arc is sometimes found to be as destructive to gutta-percha as daylight. + Most of the guttapercha employed as mouth mouldings is, however, rendered pink artificially. India-rubber is still more commonly used nowadays as above. nil; iN.sri„\ii\<; k\\ i.i.oi'i;. 263 'I'lu' sii|)])ly of j^iilta iH'icha ^fciicrall)- hcin^^ iiui<:h sinallcr and tlic cost accordiii^'ly iiuicli ^^rcralcr — lliaii in ri)rm(.T times, iIk- avcraf^c i^'uttapcrcha MOW coininonly met with is usual!)' 'if a mori; mixed, and, tlicrcl'on;, often ol' an inferior ciiaiaetcr to that \\ln'(li was used for tlie same pnriiose at that periofl. I'he mi.'re fact of several different ^uttas of an inftMior ijuality bein;^; mixed with a ^iven hi}.di (|uality, but scarce and ex|)ensive, ;;iitla, lhoiii,di sometimes to a certain extent beneficial, is often sufficient to account for tiiis inferiority ; not to mention tlie by no means uncommon [)ractice of adding resinous matter in order to produce specifically c;ertain electrical results, with a view to meeting,' the difficult)- fif the scarceness and increased cost of ^iitta-jjercha. The result is that the material was in thos(; days much mtjre durable.* It is true that the total insulation on a line of ^'iven dimensions was not nearly as iii^h in th((se days as it is at prescntt — notwithstandinj; the above facts. Ihis was mainly due to the lack of experience in joint- mal' some authorities — there is more ozone in the sea-air than elsewhere, it would aj)pear that exposure here, if prolonj.jed, would be an unfavourable condition for this material. On the other hand, up to the present, the only known way to jirevent oxidation of j^nitta is to keej) it under water. It is then practically inde- structible ; + indeed, there has never been a case known of the cji'^ta sufferini^ through oxidation in the immersed portions of submarine cables. It is on this account that some companies who.sc cables are landed where the climate is hot, enclose the subterranean lines (joining u)) to the cables) in pipes which are kejjt filled with water under pressure from reservoirs on the higher portions (>( the ground. When tubes without water are used, or where the cable is buried in dry sand, if the wire be insulated with gutta-percha,* the gutta becomes brittle and perishes in course c^f time, leaving the ccMiductor absolutely bare in places. Thus, land lines, or even beach cables, should be either ke|)t in water (if gutta-jjercha insulated) or * Resin is a most dangerous insulating substance. Hesidcs rapidly evaporating, and tending to gradually render gutta-pcrclia brittle— especially in a dry atmosphere or soil — it also acts chemically on gutta-percha, and tends to destroy its natural gumlike cjualities. I>y iindering it less homogeneous, the gutta is more subject to oxidation. t It has sometimes been thought that salt-water had in itself an absolute j)reservalive intlucnce on gutta-percha. This is not so. Gutta-iiercha remains constant at the bottom of the sea only on account of the absence of oxygen, both as regards air and light. It is prolxible that light tends to have an even greater deteiioraiing etfect (by oxidation) than air, though it has never been actually proved. The sun's rays, however, lose their pene- tration at some 100 fathoms belou the surface of the sea. .-\gain, a core which is in any way armoured is not likely to be much troubled with the presence of light. In a cable at the bottom of the sea, gutta-percha is, moreover, at its best, mechanically anil electrically, on account of the pressure and low temperature to which it is subjected. I In this country, when gut'.a-pcrcha covered wires have been laiil underground, certain precautions were found necessary in quite early days in the way of protecting them from sun and air. The gutta-percha dielectric was taped e.xternally, which taping was then tarred and sanded. The tar used at first was coal tar, but this was found to act iujiniously on the jjcrcha. Subsequently Stockholm tar (applied to yarns) was adopted, and this was found satisfactory. 266 SL'BMARINK TKt-EC.KAI'llS. else covered with india-rubber.* In 1852 Mr lulwin Clark found that f^utta, during the necessary purifying process, takes up mechanically a certain amount of water, which again evaporates partially during mastica- tion, leaving in its place a resinous substance more or less porous. A fair sample of gutta taken from a newly manufactured cable, and analy.sed by Dr Miller in i86c, contained 15 per cent, of resin, and 2.5 per cent, of water. Although the methods of ]nirifying gutta have since been much im- pro\ed, it also ajipearcd from the 1876 experiments of I'rofessor Abell" that as regards the |)roducts of oxidation formed at the expense of the gutta and of the water in suspension, much the same results were obtained. The analysis of some high-class guttas, which had been e.xpo.sed for several years to light and air, shewed that oxidation takes place but slowly under the influence of these two agents in cases where the gutta has derived a certain degree of homogeneity and solidity, through |)rolonged mastication. The proportion of water in sus])cnsion thus indicates — at an)' rate, appro.ximately — the degree of perfection of the gutta in this latter respect, upon which the insulation resistance so largely depends.* The pro]3ortional quantities of salt and fresh water absorbed by gutta- perclia under the same conditions, at ordinary tem])eratures (according to the late Sir William Fairbairn's i860 experiments §), are as 3 to 5. ; This absorption takes place somewhat rapidly at first ; after some time it ])roceeds very slow ly but still goes on — indeed, it is doubtful whether even in the course of a year a submerged core has absorbed all the water it will e\cr do — depending upon the nature of the material and the prevailing circum- * " Engineering and Electrical Report on the Vof 15,iy-I)akar Repairs," by Charles Bright, A.M. Inst.C.E., M.I.E.E., 1S94. t Now Sir Frederick Abel, Bart., K.C.B., F.R.S. + The denser and more homogeneous a vegetable fibrous material is, the less porous it is, and consequently the less it tends to absorb moisture or actual water, with the result that the electrical resistance becomes higher. Viewed physically and electrically, the gutta-percha dielectric has been likened to a sponge (and also to sand) in which the conductor is enveloped. S These experiments were conducted in connection with the Board of Trade Inquiry (of that year) into the Construction of .Submarine Cables. II The quantity of salt-water absorbed by a given bulk of gutta-percha being thus less than the quantity of fresh-water which it will similarly absorb, is naturally accounted for by the greater density of salt-water. This was arrived at by the material being plunged into fresh and salt water each in turn, free from ])ressuro. In the case of fresh- water, after the gutta-percha had absorbed all it could do, it was found that the weight of the gutta-percha was 5 per cent, greater than previously ; whereas when the same experi- ment was made in salt-water, the weight was increased by 3 per cent. only. The author assumes that these experiments w ere made with raw gutta-percha, believing that manufactured gutta-percha would not absorb anything like this amount. THK INSULATING ENVELOPE. 267 stances. The rate of ab.sorption is said to be .somewhat hij;her under a vacuinn than under the sea. The absorption of .sea-water doubles when tile teinijerature rises from 4 C". to 49 C. — no doubt owing to expansion : for fresh-water tlie increase is rather more rapid. Pressure makes no .sensible difference in this comicction.* The water absorbed appears only able to penetrate laterally to a very slight distanced and when this limit is reached, the quantitj- of water does not afterwards increase, no matter how great the thickness of gutta.* Water mechanically susjjcnded in the pores of gutta-percha has, a])parentiy, no effect on its electrical tjualities until the weight of water exceeds 2 or 3 per cent, of the weight of gutta, con- .sequently in ordinary practice this (|uestion of absorption by a gutta- percha cable core § need never be considered electrically, except in the case of a flaw. II The main question which decides whether or no any of the mai;crials suc'i as are mechanically adapted for the |)urpo.se are also good insulators electrically is their degree of deiiseness and homogeneity. This is largely on the grounds of durability, as alreadj' shewn ; but it is also based on actual electrical values. Viewing all substances as conductors of electricity, there arc certain facts which it is well to bear in mind regarding good conductors and bad conductors, or insulators. Thus, the purer and more homf)geneous the good conductor is, the better it conducts ; and, on the other hand, the purer and more homogeneous the bad conductor, or insulator, is, the worse * The explanation of this rests, probably, in the fact that when material pressure is applied, though there would be a greater forcing' in tendency as regards the water, yet, on the other hand, the material would become correspondingly denser in its texture, and therefore less porous and absorptive. Thus it is doubtful whether at the bottom of the ocean the absorption by gutta-percha is at all greater than in a bucket of salt-water. If the experiment could be conveniently carried out, the degree of absorption might with advantage be noted at various dejiths, so as to determine at what point the structural influence outweighs the tendency towards increased absorption. A proof of this increased homogeneit\' of gutta-percha under a given column of water exists in the reduced bulk, which may be observed in a cable core when picked up from the bottom of the ocean after a certain jjeriod of submersion. + It is not thought that even the smallest particle of water e\er reaches the conductor through the insulation of a submerged core (though under great |)ressure) except at an actual fault. I Fairbairn found that the absorption by thin sheets was actually greater than in thick sheets, pointing to cajjillary attraction on the surface being the main cause. In any case, this is an extra reason for a certain minimum thickness of insulation for a submerged core, quite apart from questions of specific resistance. >$ Manufactured gutta-percha invariably contains a certain small percentage of moisture —indeed, from a durability point of view, this is a desirable feature. Ji Many years ago it was shewn by I'rofessor Fleeming Jenkin, F.R..S., that the insula- tion resistance of a sound gutta-percha covered wire, enclosed in an iron sheathing (with the ordinary intermediate packing), is little, if at all, affected by submersion. 26.S SUHMAKINK TKI.I'.CKAI'IIS. it conducts, as a rule, /.('., the better it insulates. I'his may, to a ^reat extent, be accounted for by the fact that the former is alvvaj-s a metal, and the latter invariabl)- a vegetable fibrous substance with a certain dcjjree of porosity. It must, however, be admitted at the outset that there are man)- features regarding insulating materials,* which with our present knowledge we cannot attempt to explain — as, for instance, the inany contradictory facts regarding gutta-jiercha and india-rubber when brought into com- |)arison. It can only be said generally that what appears to constitute a good conductor in a metal, at the same time constitutes a bad conductor (or good insulator) in a non-metal, or vegetable substance. When a fibrous material is made up from several different substances it cannot possibly be so homogeneous, and, therefore, in that case it iriust be more porous. Again, actual chemical action occurs between its components ; and, in fact, the nature of the material is liable to be entirely altered, being governed by the composition and the proportions of the same, electrically as well as physically. A high insulation resistance is, however, only a .secondary consideration for the dielectric of a submarine cable as compared with durability, and a pcnnanctice of its insulation at a fixed minimum.f If low resistance mi.xtures could only be relied on to remain constant they would answer the purpose admirably as dielectrics ; but, unfortunately, owing to chemical action between the constituent parts, or to lack of homogeneity, the material tends to gradually alter — indeed, to deteriorate — physically and electrically, until a point is reached of comjjlete breakdown in its insulating powers. Speaking generally, it is found by experience that permanence of electrical, as well as mechanical, qualities can only be .safely looked for from the pure (homogeneous) materials,* which also happen to have a ■* As a contribution to, and illustration of, the molecular theory of conduction, Mr Rolio Appieyard recently read an interesting and instructi\e paper on "Dielectrics" at the Physical Society, durinj,' wliich he shewed experiments with a gutta-|)crch;- sheet having, in turn, various proportions of brass tihngs incorporated in its texture. In the course of the discussion the present writer suggested that the phenomena of the resistance being decreased so suddenly when more than a certain proportion of the filings were worked into the gutta sheet, was accounted for by the circumstance that the conduction as the result of induction became possible on their being sufficiently close to one another to permit of electric influence {Pioc. Physical Sec). + As a matter of fact, a cable with a comparatively low resistance dielectric should signal through somewhat better, within certain limits, than one with a very high resist- ance, other conditions being equal — though practically this seldom, if ever, comes in I As a rule, too, the greater the density of the texture, the higher the resistance on account of decrease of moisture suspended in the pores. Speaking generally, there is a Tin; iNsiLATiNc i:n\ Ki.oi'H. 269 fairly Iiit^h specific rcsistanci.; at the outset, and Iii^dicr tliaii most of tlic coin|joim(ls.* Thus, though different classes of gutta may be sometimes advantageously, or necessarily, mixed toj^ether, other materials, of an entirely different chemical composition and different texture, cannot be advantaf^eouslj' allied with i^utta-pcrcha for permanent electrical and mechanical pur])oses.+ A certain minimum is, therefore, usually stated for the resistance of the dielectric, and this is best fixed from a knowled^fc of the corresponding^ s|)ecific values of the most suitable tjuttas to be obtained in the market at the time. A fairly hi^di insulation resistance has also the advantage of shewing up the presence of any incipient faults more readily during manufacture, and also of permitting a lower batter)- power for subsequent "working" jHuposes, than if a material were emplcjjed which, at tlie very outset, had but a comparatively low resistance. Inasmuch ;is an abnorni'illy high resistance is nowadays usually suggestive of either a comparatively large proportion of resin or else an over-masticated :J gutta (for purposes of low capacity), it is very customary also to specify a certain /////// for the dielectric resistance.^ connection between density and homogeneity ; and, in the case of ;i material like gutta- percha, homogeneity usually implies a iiui.ximum electric-al resistance, as well as a n\i^iiliir value in this respect. Where, however, the pores are tilled with resin oil, the resistance then would usually be greater than with a more dense and homogeneous structure of the same material. Incidentally it may be mentioned that attempts hive been made to rc-juvenate old gutta-percha (from land lines) with many cracks by forcing resin into its pores ; but, for chemical, mechanical, anil other reasons, success has not been met with in this respect, except by thoroughly mixing the two materials together, after reheating the old gutta to a plastic condition, by being taken off the wire and practically re-manufactured. Resin oil (unlike many oils) has a higher resistance and, as a rule, a lower capacity than gutta-percha. Thus, eleitricaUy speaking, its admixture with gutta-percha should be distinctly favourable. Unfortunately, however, it is of a non-durable character, as it tends to eva|)orate. (iutta-percha with a large proportion of it is, therefore, not serviceable for any length of time. * .Steadiness of insulation is what is mainly looked for, however, as a sign of mecha- nical and electrical permanence, rather than any abnormally high specific v.alue. t ISroadly speaking, density and homogeneity —besides opacity, as a suggestion of purity for a given thickness and colour -may be taken as being collateral with a more or less high electrical resistance ; and the latter effect is, therefore, likely to be promoted by low temperature, pressure, and the mechanical "setting' due to age. \ In throwing off moisture, mastication, as a rule, has the eftcct of increasing the resistance and decreasing the capacity of gutta-percha up to a certain point, at which its physical and chemical character is altered. To uie a trade expression, the gutta-percha wnen in this last condition is said to have been "killed." S .*\ high rate of electrification also often implies the presence of a large proportion of resin. It is sometimes, therefore, specified that the electrification between the first and second minute should not be above some 5 or 6 per cent. 270 SUIIMAKINK TKLKHUAI'lIS. Gknkkai, lM)RMri..i;. Dielectric Resistance. — The iiisulatin^f power of gutta-pcrclia, or tin- resistance whicii it i)f(ers to the passage of an electric current, that of i)ure copper beinjj tal- of gutta, per unit of volume, vary within certain limits, and have to be determined for each particular ca.se. Commercial guttas being them.selves mixtures of different natural kinds, manufacturers desirous of ascertaining the preci.se value of the samples they buy, not unusually make about 500 \ards of core from each sam])le, and then compare the electrical qualities of the different lengths. The insulation resistance R of a hollow cj-lindcr composed of any dielectric is given by the formula where A is a constant, D and ' probable, if only on the grounds that the material would be rendered so much less porous ; indeed, when the pressure gets over a certain figure, it may tend to actually squeeze moisture out of the gutta as it would a sponge. In this case a jioint might somewhere 'le reached at which ■permanent deterioration would occur. I At Hrst sight it would apjjear that the natural method of determining the effect of pressure on the resistance of a gutta-percha core when submerged would have been to lower it gradually in the sea : but here, again, the temperature would decrease as well as the pressure increasing ; consequently the temperature woukl be taking part as well as the pressure in altering the resistance — more so, indeed. ;i In order to he entirely independent of the opposite effects of absorption, and to arrive at a strictly true coefficient in this formula, the pressure should, really speaking, partake of a solid form. This, however, would be impossible in practice. 2/2 siHMARiNK ti:i,i;(;kai'Iis. pressure in ll)s. per S(iiiarc inch, and R/ = the incruasL-d rcsistaiici; rcsiiltinj,' from subjection to such a |)rL-ssurc. Tiuis, 0.00023 was tlic amount of increase in resistance found to occur on unit resistance (\ mej^ohm) by unit (lb.) |)ressurc.* .Messrs ]iri}j[ht and ("lark tested the first Persian (iulf cable under pressure, finding the j^utta-pcrcha to be increased in resistance 2.6 |)er cent, for every 100 lbs. per scpiarc inch pressure ; whereas Siemens' t.-xperi- ments siiewe., rou^t^hly about 60 |)er cent, per \.M. pressure — equivalent to somethin";- lilni|)<>iiiiil iiitcn-st, law ;* as in the case of tin; inctals, only at a iiuicli ^jrcater ratc.f With (lifferciit K'"'""^. '|"''''''""^ ■'''"' mixtures, this coefficient of variation for ^Mitta-percha is siilist.iiitiall)' difft rent ; * inorefivtrr, it varies very niuch accordinj^ to the a;.;e of the material, i.e., accordin}^' to the ienj;th of time it lias been maimfactnrcd into <;oic. 'Ihus, thoi^di th(.' law has never bet'ii (|ues- tioncd since first laid down ;is above, the coefficient is only ron).;hly applicable to ^;ntta-|>ercha ^'(Mierally. Strictly sptjakin^^, the coefficit'nt rc'iuires to be determined for each (pialitv of ^(ntta. Indeed, if we are to obtain absolute accuracy, it should bi! freshly arrived at by experiment on evi-ry new set of coils where a chaiiffc is made in the i.;um, or {^uins, used. Mvcn then it is only a|)plicable to newly made core, and not strictly accurate when applied aftt^rwards to a sul)iner).;ed cabh; sometime after mamifactnre. An allowance should then, in fact, be made for the increase in resistance by aj(ein^ or maturation— suppr)sed to be due to a natural " setting,' " of the texture.^ Such exactitude is not, however, really necessary in practice, and s<:;irccly comes within the limits of tiie tests. The variation is a sub- stantial one in any case, and should, thereforw commonly met with, the resistance variation per cent. \n:v de^net; l''ahrenheit* is usually staincd at various trm|i(.'raturcs. On (:onn('( tiiij,' up the points, the cxpcrinR'nIal curve except for irr<'Kularities due to slij^lit ('rrors involved in llii' experiment ■ pra<:ti<:ally coincided with the true lo^;aritlin)i<: curve. f The resistance of gutta-percha at T,(t V. is about ten times as much as it is at 75 !•'., ntJK'r conlc item as regartis the dielectric. •! In subm.-irine cable work all pr.utical temficrature measurements and observations are made according to the Fahrenheit thcrmometric scale. 276 Sl']!>[ARINE TKLF.GRArilS. ture (75° F.)* will be 0.075 ; that is to say, an ori^t^inal resistance of i megohm under a decreased temperature of 1 I'., would become 1+0.075 = 1.075.+ Then for a further decrease of temperature this coefficient is naturally ajjplicable (by compound interest laws) to the last existing resistance — /.<'., in this ca.se to 1.075— and ""t nierel)- to .075. The same principle naturally applies when the resistance is some multiple of unitj'.J Thus, based on the coefficient for variation obtained by experiment, a complete .set of tables may be drawn up, giving the correct coefficients applicable to each number of degrees of difference of temperature from the standard temperature — in fact, the coefficient for each degree Fahrenheit, already calculated. Thus also with the coefficients for temperatures on the other side of the standard temperature. Such tables (a|)plicable only to the particular material in use) are to be found in ever)' cable factor)- all read)' drawn up, as well as at every testing station.§ The author has attempted an explanation of the phenomenon of the resistance of gutta-percha being increa.sed b)' a fall in temperature and decreased by a rise thereof On the principle that all such electrical changes are due to physical changes, it comes back, as in the case of pressure, to var)'ing degrees of de!isity and homogeneity. The nature of the physical change produced by a change of temperature on vegetable fibrous sub.stances of the gutta-percha (and india-rubber) order is that of cold * This is the standard temperature at which tests are made during manufacture, and to which subsequent tests are reduced to, for purposes of proper comparison. It lias been for many years universally agreed on as being a convenient average temperature capable of being readily provided during manufacture. t Where 0.075 is the coefficient for I ' change of temperature on i megohm, then for, say, 20 difference the coefificient becomes (o.o7sr and in the case of the 20' being that amount below the original temperature (at which the resistance was 1 megohm), we get (i+o.o75)* = (i.o75)'-'" Or, expressed in a general way for the compilation of a complete table = (1.075)" where 11 varies according to {i.e., represents) the number of degrees difference. + If the original resistance, instead of being I megohm, be, say, 600 megohms, then with a decreased temperature of 20 we get ( 1.075)-'" X 600 or 600 X (1.075)'*' If, however, the temperature be increased by that amount, then the coefficient, on an original resistance of i megohm, becomes (i -o.o75)*' = (o.925)'^'' and with an original resistance of 600 megohms this becomes (0.925)*' X 600 or 600 X (0.925)'-'^' S In practice they are usually made out, in a simplified form, for uniform subtraction (or addition) of logarithms for either side of the standard temperature. \\ Jotinidl Soc. Tel. Enters., \o\. xvii., p. 679; Electrical Revicio., i6th November 1888. Till'. iNsri.ATiN(; KNVKi.ori:. 277 coiUnicliiiL; tlic material, and licat cxpaiidiiiL;- it. Viewing ail substances, in some degree, as conductors, b\' contraction the |)orcs of tlie material tend to be closed by its molecules being brought closer together. Conse- i|uently it is more compact, and less s|)()nge-like or "leaky" in its texture: Its absorptive tendency is proportionately decreased, and, indeed, any moislun: previousl)- contained b\' the jjores is, more or less, scjueezed out. The effect of heat, on the other hand, is that of ex])ansion separating the pores, and thus increasing its natural absorpti\e tendency as well as the disposition towards leakiness, i.e., conduction. The whole effect may be, in fact, traced to mechanical causes as in the case of jiressiu'e, though the result is much more marked.* The fact that tem|Jerature exerts an opposite influence on the conducti\il\' of \egetable fibrous materials to what it does on metals + may be to some extent explained, as the author has previously suggested,* by the fact that fibrous materials such as gutta-percha contain moisture, a good conductor in it.self, .uid natural!}' tend to take up all the moistiu-e the\- can. \\y |)ressure or low temjjeratiu'e this moisture is expelled ; In- heat, more is absorbed, for reasons already shew 11. v^ The fact that the resistance of gutta-jiercha (or indiarubbcri varies b\- change of temperature according to a logarithmic curve, rather than bv direct proportion — i.e., is increa.sed at a rate so much higher at low than at high tL'm])eratures — can be ))hysically accounted for b}' the circumstance that it is only when low temperatures are reached that the ex|)ulsion of moisture begins to take place. | * When a cable is laid at the bo'''^ni of the sea, the cold water b\- convection takes away any heat established by pressun t This is sometimes less accurately expressed by saying that electrical comiiictors and insulators are oppositely affected (as regards their resistance) by temperature. Carbon, however, is a good conductor, but being a porous vegetable suljstance, it is attected by temperature accordin.;ly, i.e., its electrical conducting power is increased by a rise in temperature, and tvVi' Tvrsn. J: Electrician, vol. xxiv. S But for this, no doubt temperature would influence such gums the op])osite way — /.(•., the same as it does metals- for, viewing everything as a conductor in some degree, increased homogeneity should imply more efficient molecular action, and, therefore, bc.ter electrical conduction— inasmuch as it is not unusually recognised that the high conducting power of the metals is based on their denseness and homogeneity. The author recognises that this assumption is not in keeping with the \ ibratory theory, Init the latter does not appear to be borne out in all its aspects as regards the actual facts concerning the effect of temperature on metals, though it does in the case of temperatiue and pressure in connection with fibrous substances. II The conductivity of cop|)cr is affected by temperature according to the same rule. This is probably by reason that metals are not materially condensed until low tempcra- U 278 sir-MAkiNi: Ti:i.i;<;kAriis. \Vc have already stated that, as in metals, the low resistance ^iims and mixtures are more affected elcctricailj' b)- temperature tlian those of a hi^di sjiecific resistance.* The explanation of this fact, as ret^ards fibrous materials like <.nitta-percha (or still more, india-rubber), is ])resumabl)- that the lower resistance i;ums, bein^' less pure and homogeneous, \er)' usually contain more moisture, and are more absorptive. Thus pressure or low temperature increases their resistan!_e more, by drivint; out moisture and preventing' abs( )rpti( )n. The view that the difference in the effect of temi)erature on the resist- ance of fibrous materials to that on the metals may be accounted ft)r !)}• the jirescncc of moisture and ab.sorptive tendency of the latter is further sup- ported by the fact that change of temperature takes much lonj^jcr to affect the ^utta-percha insulator of a core than it docs the co|)|)er conductor."'" It mi^ht, ill some ways, naturalK' be sup])osed that, the cojjper conductor beini( enveloped inside the ^utta-|3ercha insulator, tlie ^utta-percha would — especially in the ca.sc of a laid cable — the soonest adapt itself to any alteration in the prevailing- temperature. This does not, however, appear to be the ca.se ; in fact, the gutta-percha, as a rule, latjjs uniforml}' behind the copper in this respect by about forty-eight hours. That is to say, in the instance of a fall (or rise) of temperature of, say, 30' !<"., the gutta- percha would not give its true resistance value (due to change of tempera- ture) till about forty-eight hours after the cop|)cr has done s().:|: In the copper conductor it is only a question of the degree of density and homogeneity of the metal being altered by changes of temperature ; but in gutta-|jercha the effect of temperature change is (by increasing, or decreasing, its density) that of gradually driving out, or absorbing, moisture, and thus gradually increasing or decreasing its resistance. Inasmuch as it takes gutta-percha so much longer to adapt itself electri- cally to a change of temijerature — or to become " temporised," as it has been expres.sed— there must be a time when, in reducing the observed dielectric resistance to 75 F., it is inaccurate to correct the resistance b\- the temperature calculated from the conductor resistance. Under these tures are leachcd. No degree of presbuie expels any large ainounl of iiioistLiie from gutta-perclia or iiulia-riihber. and the conductivity of copper is not aftectcd at all by pressure — so far as we know, at any rate. * As regards metals, no ready e.xplanation offers itself indeed, the opposite might with more reason have been looked for. + "Cable Testing, Copper and Dielectric Resistance," by Charles Bright, .M.I.K.lv, ///(• Elcctrkum, 7th December 1888. \ This statement is based on actual experience on a calilc e.xpedition, during the course of which the temperature varied from about 32 F. to about 90 F. Tlir, INSULATINc; KNVELOPK. 279- circumstances it will be foiiiul sometimes useful ;uul instructive - if ()nl\- as a check — to calculate the temperature of the dielectric from its own resist- ance,* and also, as an additional check (though only a rouj^^h one), from the observed temperature where the core, or cable, rcsts.+ As it happens, the conditions at the bottom of the ocean are, ordinarily speakinjr, in every way favourable to a gutta-perciia insulated conductor, as reffards the conductor itself as well as on account of the insulator. Thouj^di temperature affects the copper and the j^utta-pcrcha the reverse ways elec- trically, inasmuch as one is intended to conduct and the other to insulate, this is in every way favourable. 'Ihus, the low tem|)erature at the bottom of the ocean increa.ses the conducting })ower of the conductor, and still more increases the insulation resistance of the dielectric* Ilowexer, at very low temperatures gutta-percha is liable to crack. Thus, in sr)me parts of the Pacific Ocean (where the bottom temperature is .said to be below freezing |)oint), it is possible that gutta-percha might lose its insulating qualities altogether instead of the dielectric resistance being further in- creased, as it would otherwise naturally tend to be. India-rubber has not this tenrlency to crack with low temperatures, and might, therefore, recom- mend itself under certain circumstances of this descrii)tion, as much as in instances of abnormally high temperatures. Age. — Another feature which governs the electrical resistance of pre- pared gutta-percha is its age, /.<■., the length of time for which it has been in the manufactured form.S^ This influence is due to the maturing of the material causing a natural tendency to mechanicall}- "set," which operation increases the resistance appreciably, though not to anything like the same extent that motlerate decreases of temperature or average pressures do. This mechanical " .setting " goes on quicker at low than at high tempera- * III this case the ctTect of any iirevailin^' pressure on the resistance of the j^utta- pt'icha at that depth would, of course, letjuire to be included in the calculation. f It may be mentioned, in this connection, that the late Sir William Siemens intro- duced in 1 860 what he called a "resistance thermometer." This was a plan for obtaining a more accurate idea of the temperature of the place where the cable rested by measuring the resistance of a coil placed alongside the cable, any given resistance being known to correspond to a certain temperature. This may prove a useful clue sometimes when a cable is obliged to remain dry in a tank, say; and where, therefore, the gutta-percha dielectric may be in jeopardy. X The pressure of the bulk of water above the cable — though it is not supposed to perceptibly aficct the conductor -also increases the insulation resistance, as has already been shewn. S When wfc, gutta-percha tends, of course, to o.\idise and deteriorate if exposed to air or light. 280 SURMAKINi: TICLEGKAPllS. tiires, ;uul (iiiickcr out of water than in water,* where no evaporation of moisture can occur. It mostly takes place immediately after manufacture.t owin^ partly to the moisture taken uj) (lurinj,^ mastication. Thus, the insulation resistance of any particular coil can be easily bnaight up to spccific.ition b)' keepinj^" it long enough (preferably at a morlerate temperature out of water) before final testing, if it shews signs of being slightly wanting in this respect. This factor of variation of resistance by age naturally tends to become merged with the other changing influences — temi)erature and pressure. As in the case of tem|)erature and pressure, it varies with different gums and mixtures — and much in the same way. At present the coefficients applied for temperature are u.sed for gutta- percha generally, irrespective of age. This cannot really be correct, for, as we have already seen, the coefficient is different for gums of different specific resistances, and the effect of age is to increase its resistance — indeed, practically to render it a different texture of material by "setting." In the first place, in order to se|)arate the.se two influences, the final tests at 75° F. should be taken at the latest possible moment after manufacture. (2.) Experiments for deterinining the temperature coefficient should be made on the same manufactured gutta-percha as soon after construction as may be, so that the subsequent resistance change in the core shall l)e as far as possible independent of age. (3.) A resistance curve and coefficient should be drawn up based on exjjeriments on gutta-percha at various periods after manufacture, the temperature and pressure having been main- * Thus, again, the aye effect of gutta (sucb as causes it to increase in resistance) is that of heconiiny; more liomogeneous. Moreover, the moisture is gradually forced out under certain conditions by the material drawing itself up. it will be understood, therefore, that a low temperature naturally favours these conditions ; whereas a high temperature, by expansion, would be unfavourable to such a change. Again, exposure to air and light tend to bring about oxidation as fast as the moisture leaves the gutta-percha, which also tends to increase the specific resistance of the material until cracks begin to appear, and then a ra])id fall in resistance occurs, by the material gradually losing all its essential oil by evaporation. A physical picture of what probably occurs would be supplied by covering a wire \\ ith cold cream, butter, or any material containing a certain proportion of water, especially if the experiment be carried out under ordinary atmospheric conditions and at a low temperature. The fact that the absorption of oxygen (of high specific resistance) has something to do with the increase of resistance of gutta-percha by time in the presence of air and light is somewhat borne out by the circumstance that the material gradually becomes darker by exposure. Indeed, pure, white, gutta-percha eventually becomes as black as any other gutta-percha, and the sap when left out in the sun to coagulate soon darkens at the very first — this latter being due to oxidation. t /.«•., almost entirely within the first 100 hours— usually assuming a permanent state, at any rate, whilst still at the factory. Tin: INSULATINC KNVKI.Ol'K. 28 1 taincd coiistiiiit. This would tlic-ii c;iiat)It' the necessary allowance for variation of resistance due to a^^e alone to be applied. ('4.) On the above ^^rounds a standard a^c should really be fixed on, for the purjjoscs of speci- fication, and of after comparison and refluction, in the same way that a standard temperature .ind a standard (atmospheric) pressure is adopted, /.('., all standarfl tests at factory should be made a certain stipulated time after manufacture of core. Sometimes, but not alwaj's, jjrovision is made for this in specifications b)- a clau.se to the effect that the core tests are to be made a certain number of daj-s -usually fourteen -after manufacture.* Inductive Capacity. The specific electro-static capacit}- of t^utta- ])ercha, relatively to that of air taken as unity, is about 4.3. The electro- static capacit)- K of a hollow cjlinder, 1) and d Ixmiil; tht; exterior and interior diameters, is ;;i\i'n by the formula K = .\ nn'crofarads where L re|jresents the lent^th of the cxlinder, and .\ is a constant ; or, more definitel)- expressed, 1\.= 1.3S K '—— microfarads II J a where K = the capacit)' of a jjlate 1 scpiare fof)t surface X i mi! thick = .1356; and 1.3.S a constant which varies materially with the particular c^utta used. The electro-static capacity of a cable core de|)ends upon the surface of the conductor and the thicknc;ss of dielectric. It, in fact, \aries inversely, antl In- compound interest, in respect to the relationship existing' between D and t1, which i-. ex])resscd in a formula b\- I K L- 1) This law was first enunciated bj- I'rofessor Thomson (now Lord Kelvin) in connection with the construction of early Atlantic cables. It will be evident that the capacity varies also w ith the (]uality of the dielectric material, /.('., with its specific inductive capacity. This is usuallj- represented bj' the ca|)acit\' of a cube naut of the core reduced from tl.e ■* A niinimum dielectric resistance is often specified for the cable when laid. It is not unusually stated tliat when reduced to 75 F. the values shall Ije equal to that as core at the factory. It ouj^ht, however, to be materially greater on account of age as well as pressure. 282 SI i;maii(lc oCii* — \arii's \('ry mii
  • i' ^iims iiscrl in its coiiiixisitioii, and iIk- < Diiditioii of its tL-.\tiiic. •As a ^a-iicral ruk-, tliosu materials uitli tlic hij^dicst insulation rcsistancL- oITlt also tliL- lii^dicst resistance to induction — />., have the ioWL-st electro- static capacity— owiii^f, also, no doubt. 111 their greater |)iirity and density. This does not always, houexcr, a|)|)!\- in the case of inductive cap.icit)', for mail)' inferior insidatin^; f^unis and mixtures of ^unis ha\e i|uiti' a hii^h inductive resistance — more so, indeed, than some of the pure and hii^hly insulatin^f ^anns. This bein;^ so, in the author's opinion, a thin hut sufficient coat of hi^h (juality insulating f^utta su|)pleiiieiiti'd I))' ;i sufficienc)' (for mechanical ijurposesj of lower <|ualit)- ^utta outside it, iiii^ht hi' found a serviceable form of dielectric. The capacity mij^ht then be further decreased — and the workinj^ sjjeed correspondingly increased — by some more low (juality ^nitta bein^^ incorporated with the jute servinj,^ thus converting- the latter into a jiart of the dielectric instead of formiiiLj, when wet, the inside surface of tlu- outer n.eyden jar) plate. I'hiis, by increasing; the thickness of the dielectric, the cipacity would be materially reduced, and the speed corres|joii(liiij.^ly increased. The initial cost of the cable nii^ht also be appreciably lessened in this \\a)'.+ .Moreover, the inductive capacit)' beinj.; thus decreased, the size of the conductor (for low resistance) mij(ht bi- rerluced for a ^dven s|H'ed. Should the electro-static cajjacity of a con; be too hif^h, it can usually be j;ot down within the recjuired s|)ecificati()ii limits by the i^utta bein^^ subjected to further mastication. Owinj;, however, to the circumstance of hii^h insulation resistance and low inductive capacity bein^ liable to be mori- or less inseparable, it is very often found that when the capacitx has been sufficiently reduced, the insulation resistance has ^^oiie up to a jjoiiit above the specification recjuirements, in ca.scs where a limit is jjlaced in this direction with th'^ object alrcad)- named. Weight and Diameter. — Ihe wei^dit of L(utta-i)erclia rc(|uired for a core of 1) outside diameter, the conductor havini; d diameter (both 1) and d c.\|)ressed in mils.), is a|)pro.\imately '^"-'^\..lbs. 490 * It mij;lit appear as thoiinii tlic reciprocal to this- /'.(•., the inductive rcsisliutce of the dielectric:, or its rcsisliince to iiuluction- would be the more natural feature to consider in this connection ; liowever, the inductive iapinity is what is always taken and stated. t .Such a plan would provide for the localisation of faults in a manner that would scarcely be practicable with some of the suggested methods for obviating the static charge and so increasing the working speed. 284 SLMMAKINH TKLIXIRAI'US. When the ratio between the weights zc of copper and W of pcrcha^ — or relative diameter d of conductor and D outside core — are given, the capacity and resistance of the core are the same (with given si^ecitic values), no matter what the absolute values are. Thus it is only necessary to ascertain the quotient or , and the capacity or resistance is arrived IV a at from the specific values of each. 9 A Eastern Telegiapli Coni|Kiiiy : Aden Station and fjuavtcrs. THE INSULATING ENVELOPK. 285 Section 4.— Method of Pukiivinc (iuTTA-i'i:K(H.\. Exportation and Importation. — Most of the raw tijiitta-percha imported into this countr}' and Europe Ljcnerally comes from Sarawak, from British Nortli Horneo, anri from Java. Large quantities are sent from tliese |)laces to Siiit,fai)ore as well as to England for preparation for commercial purpo.ses. From the Mala)an Archipelago it arrives at the merchants, dealers, and agents in England, German)-, India, and elsewhere, in forms varying roughly between that of a ball of about i lb. weight and a large block of h cwt., the average weight of each lumj) being about 30 lbs. These irregular lum|)s are packed and sent home in baskets (in which it arrixes at the cable factory) about 3J; feet high bj- i^ feet wide, and holding about l /, cwt. of gutta-percha. Storage. — .\s already stated, gutta-|)ercha rapidly oxidises b\- exposure to air or light, and in a less degree by exposure to either alone, as well as by variation of temperature. I'or these reasons, then, it is not as a rule kejJt at the cable factory until it is actually reijuired, when it is ordered from the rlealers. It is then stored in dark rooms or cellars, maintained at a fairh' uniform temperature, as free from air as practicable,* and is [jasscd through manufacture as quickly as possible. Impurities and First Stages of Manufacture. — Being sold by weight, the noble but enterprising sa\age is prone to incorporate with it all sorts of impurities, such as bark, cla}-, sand, and stones, or any other substance more plentiful and ready than gutta-jiercha itself — indeed, even pieces of iron ha\c been added as " make-weights." The raw gutta often contains as inuch as 25, or even 30, per cent, of impuritie.s.+ Thus, to render it fit for an\- of the uses to which it is turned, it has to pass through a series of l)urif)'ing or cleansing processes. In order to render the gutta-percha " workable '" for the.se said processes it recjuires to be given a certain tem- perature — just above the boiling point of water. It is highly desirable. "'■ It may be reniarkecl, houevci, that the tendcmy towards oxidation, when in tills form, is but small as compared with its oxidising tendency dming,'and after, manufactme, when the surface exposed is so mucli greater, .uid the tendency is further cncouiaged by tlie presence of heat. t It is the first care of llie manufacturer to ehminate these foreign substances ; and should this process not be effectually carried out, the germs of decay may be left within the manufactined article, which would speedily lead to its destruction. The value of raw gutta-percha depends almost entirely on the care with which it has been collected and the honesty of the collectors— or, in other words, on the quantity of foreign matter mixe- I^'ig. 10. It represents, in I'K;. g. — ( liiliiKiry I'irsl Mastiiatur. fact, a sectional end view of the machine, c being the lump of gutta which has been inserted at o, and is being worked, under considerable pressure and heat, between the revolvirg roller and outside frame, in order to expel the occluded moisture. As will be .seen hereafter, there are several different forms of masticating machines applicable to different stages of manufacture. That which we are at present dealing with is a type of " drying " masticator, its principal object being to wring out the moisture ab.sorbed by the gutta during the * The hlouii-out aijpearance of the j^iiila when in the masticator is due to tlie expansion of moisture in the jjutta-percha, luidcr heat, to the form of steam, which naturally intlales the material. 288 SI r.MAKINK TKLKCiRAI'HS. previous operaticjn. This |m-occss, besides getting rid of further impurities, also renders it still more i)lastic by working it into a stiek)- mass. By thus thoroughl}- mixing the various cjualities employed, a compact and fairly homogeneous lump is secured. l''ir,. lo. — Sccticii.il I)i;ij;rani llluslr.itivc of tlio .KcliiMi (if .Mastiaitiiig Mai-liiiie. Thiiugh the drying operation can jje carried out in time by the different portions of the gutta being, each in turn, exposed to the air, this machine is sometimes steam jacketed to further effect this object, and so hasten the operation. In such a case the pipe C (Fig. 9) serves to conduct the steam to the inside of the hollow cylinder H for this ])urpose. The length of time required for this operation depends upon circumstances, and is determined by the foreman according to the ajjpcarance of the substance. I'lii. 11. — Washing Masticator. The size of these masticating machines is represented by a weight of about 2 cwt. I'^ach of them is capable of working about i ton of gutta per day. The gutta-percha, in its inflated conrlilion, is then put into the washing Till', IXSULATINC; KNVKI.OI'i:. 289 masticator, having w.iter in it. i'his machine is siiew n in !'~i_t^. 11, and is about 3 feet 4 inches lon^, by 3 feet 4 inches liroad, 1j)' 3 feet 2 inclies dec|). It is, in fact, larLjer than the (hyini,^ masticator to the extent of the extra space required for the water (say ico i^allonsj, so as to hold about the same quantity of ^utta (roughly 50 lbs.) — indeed, each piece of t,^utta-percha is "worked u]) " in the different processes systematically and inde|)endently throu<,diout. In construction, the washing machine is very similar to the drying masticator. It is not, as a rule, steam jacl- portion of its surface, in turn, into contact with the water which carries away the impiu'ities. These fall to the bottom of the c)'linder (', which can be emptied through the door K. The first boiling process in the tank has only the effect of separating the distinctly heav\- impurities, such as stones, etc., that might be present. This last washing operation frees the gutta of a quantity of less hard and heav)' impurities, such as particles of earth and sand, by thoroughly knead- ing them out, during the course of one to two, or more, hours, as the ca.se may be. An outside view of a similar machine,+ for the same purpose, is given in Fig. 12. This shews the hinged cover, or lid, associated with ever}- form of masticator, having two large holes K K. The entire arrangement is, in the above apparatus, enclo.sed in a large iron tank M N o P, which is itself filled with water. The impurities which are washed out fall to the bottom of the tank, and are removed at the close of the operation. * The roller of the washing machine very often has much larger flutes than in the preceding (drying) masticator. Hence, though the entin' machine is bigger, there is room for rather less gutta-jjercha at a time. These flu ire made larger with a view to more thoroughly tearing up the gutta-percha, so as to i' luighly free it of all impurities. t Very usually known as the "Truman," after its designer, Mr Edwin Truman, a surgeon-dentist, who exercised himself much in such matters, and coated experimental lengths of wire with gutta-percha prepared by his process. . 290 SUHMAKINK TKl-KCKArilS. Tlu- ^iitta-percha is next placed in ;i dninj; masticator a^aiii.* of the same description as that previously set forth in reference to the second l^rocess, but of a smaller size. The outer casin^^ of this machine is steam jacketed (instead of beinj; subjected to the injection of steam) according to requirements, as in the previously- described masticators. There are two rea.sons for this. One is .so as to prevent any fresh moisture settlin \yy iiand, so as to more thorouj,dily effect moisture exclusion, as well as to |jrcvent the ^^^utta sticking at any part of the machine by the reduced amount of moisture at this sta^^e of manufacture. Besides tendinis' to entirel\- throw off all water taken up by the jirevious (washing) jjrocess, this ()|)era- tion also helps to knead out any remaining impurities. We have now arri\ed at the stage at which gutta-percha is sufficiently pre|jared for ordinar)' commercial purposes, when it is then rolled into sheets in a manner described later, thus rendering it read}' for storage and for .sending away for further special manufacture as required. Straining. — Howexer, when great freedom from moisture is essential as well as a \er}- high degree of purity — as in the case of the electrical insulation purpo.ses, with which we are dealitg — the gutta pas.ses through a special (fifth) process of puri- fication. This process is, as will be .seen, a purel)' mecha- nical one, it being found that the small residue of organic matter still remaining is better removed In such means — rather than bj' any further prolonged washing, favouring at the same time, as it does, the ab.sorption of a further quantitj' of water, which becomes mcjre and more difficult to extract later on. The arrangement employed to effect this opera- tion consi.sts of a strainer or filter, in conjunction with an hydraulic press (Figs. 14 and 15). Here A is a thick cast-iron cylinder (about i foot 3 inches diameter bj- I foot 6 inches deep), open at one end, and capable of holding 100 lbs. of gutta-percha. The gutta is placed in this immediately after the last \\Ws\^\^^^^^'^ Kit:. 14. — Hydraulic (liilla percha Strainer. 29- s L' r>.M A K I \ K Ti :i,i:t ; r.\ im is. rdryin^-mastication) process, whilst still in a thoroiifrhly plastic state. In order to inaiiitaiii the required plasticity, and to prevent the [,aitta-percha ti[ettin,u[ cool and hard — which is, of course, i)articu]arly important in this |)rocess — the walls of the cj'linder are lu^llow, and steam caused to circulate in the intermediate sjiace. Fitted to the bottom of this cylinder is a fine iron wire gauze ])late, or sieve, D. The web of this ' temperature of Smith's gutta-percha, as determined by the in- ventor of the process, used to be taken at 8.0 percent, per degree Fahrenheit. It is supposed to be rather less under present prevailing conditions, or, at any rate, more nearly resembling that of ordinary manufactured gutta. It might be thought that inasmuch as Willoughby Smith's method of manufacture gets rid of more moisture that it would be more capable of absorbing water on subinersion afterwards, and that on this account the advantage previously gained as regards reduction of capacity would be lost again — or more than lost again — after being laid at the bottom of the ocean for some time.+ This does not, however, appear to be the case. Anyhow, the w(jrking speed is found to remain as constant with Willoughby Smith's as with an ordinary gutta-percha dielectric. * This is not what would 1)0 expected from what has already been said regarding the effect of freeing gutta of moisture, and also on account of the additional oxygen. More- over, the resistance being lower it is somewhat remarkable that the capacity should also be lower. Any increased amount of oxygen and reduction in moisture would account for this, but only consistently if the resistance be greater instead of less. + There would, in any case, often be great difficulty in actually settling this point, owing to the difficulty of accurately arriving at the capacity of a great length of cable on account of retardation and electrical absorption. Here again, this could only be absolutely settled by laying two cables, one insulated with ordinary gutta-percha and the other with \V. Smith's, of precisely similar dimensions and length, and compare their capacities (or speeds) with one another both after manufacture (before laying) and also at a certain period — siihscquciit to subinersion. Tin; INSULATING ENVELOI'E. 299 Section 6. — Manueacture oe Coke: Covering Conductor WITH Gutta-percha. Following the gutta-percha from the masticating department, it comes to the core shop in sheets (as previously described), where they are laid up read)' for use, soon becoming more or less hard. Boiling down from Sheet Form. — As any sheet is required, it is placed in a tank of boiling water. The tank is similar to that in which tne lumps of raw gutta-percha are first placed, but rather smaller. The gutta-|)ercha sheet is just laid on the top of the water, and its surface washed. Bj- the heat of the water it is softened, and once more rendered plastic, ready for being " worked " once more in a convenient form and suitable condition for its future u.se. ElG. 17. — Kiiiiil Dryint; Masticator (I'laii of liollcrs). Fic. iS. — Einal Drying Masticator (End \'iew). Final Mastication. — The gutta is then taken to a drying masticator again, similar to those in the masticating shop.* In this last drying machine, however, a slight modification has been made of late years. There are usually two cylinders instead of one, which are made to revolve in opposite directions, thus drawing the gutta between them. Moreover, these rollers — in recent forms — are, as a rule, spirally grooved (Fig. 17). These cylindrical rollers are enclosed in a rectangular iron tank with double walls (Fig. 18), between which steam circulates. It is steam jacketed, in fact. The tank is closed at the top by a half cylindrical cover A E D, which has a movable lid E E kept closed by strong iron bars. The gutta being dratwn between the rollers is forced into the grooves, fresh surfaces ♦ When a big cable order is l^eing effected, it is very usual to take the gutta straight from the hydraulic strainer to the masticator in this, core, shop (instead of converting it into sheet and storing it, etc.), to save time. 300 SUBMARINE TELEGRAPHS. being in turn more thoroughly and continually exposed to the hot air in the tank. The condensed water collects at the bottom, and can be drawn off at the outlet O, as required. A more recent pattern of the double cylindrical rollers (as commonly used in some of the French gutta-percha factories) is shewn in Fig. 19. Here the spiral grooves on the cylinders are interrupted at intervals of a few inches, so as to renew the surfaces of exposed gutta still more rapidly. Thus the gutta-percha is now rendered ready, worked up to a proper consistency for covering the conductor by insertion in the core, or covering machine. The final process of mastication, besides rendering the gutta plastic Fig. 19. — Special Drying Masticator. and again ready for further application, also has the effect of thoroughly squeezing out any additional moisture taken up by the washing process. The latter is most important at this, the last, stage of preparation. Fresh surfaces being continually exposed to the air in order to get rid of the moisture, a certain amount of oxygen is at the same time unavoid- ably absorbed in e.xchange. The gutta then gradually turns brown, and the workman who examines it at intervals knows by the ccolour and consistency when it is ready to be taken out.* * In point of fact, by stretching a fragment of gutta between the fingers until " extremely thin it appears translucid, and the slightest trace of remaining impurity can ■ be detected, even by unskilled eyes. THK INSULATING ENVELOPE. 30I Requirements for Insulating Gutta-percha. — P'or the manufacture of insulated telegraph wire — as well as, in some degree, for many other applications of gutta-percha — it is necessary to have the gum absolutely free from impurities, and almost free from moisture. Thus, these processes of alternate washing and drying mastication require to be repeated several times, as has already been shewn. The last operation (in the core shop) is, however, final, and, at the same time, has the effect of converting the material into a perfectly homogeneous paste. The efficiency of a submarine telegraph s)-stem is governed very much by the value of the insulator — i.e., its degree of purity — the nature of the mixtures of gutta-percha employed, the various kinds and proportions of gum adopted, besides the manner in which the working and mixing is per- formed immediately before being placed in the coring machine. Indeed, the success ultimately attained largely depends on the care of those in charge of the successive stages of manufacture. The gutta u.sed for purpo.ses of insulating the copper conductor is generally composed of various qualities, some selected for the sake of their physical, and others for their electrical, properties, in such proportion that will meet the conditions specified for the cable, and at the same time be a durable material. Principle of Gutta-percha Covering Machines.— As already stated, Werner Siemens (for Siemens and Halske in Germany) was probably the first to apply gutta-percha under pressure whilst in a plastic state by means of a die in a seamless, tubular, form on a practical scale. His machine may, therefore, be looked upon as the prototype of those in use nowadays in their various modified and improved forms.* Siemens' tubular core machine was, of course, very similar to machines for making — (l) macaroni ; (2) lead-piping ; f (3) bricks from clay. There are several different gutta-percha covering machines in the present day. An ordinary cylinder and piston is, perhaps, the oldest form amongst tho.se still in vogue for feeding the conducting wire with a coating of gutta-percha. In this, the gutta is placed in the cylinder, and the piston * Previously, both IJewley on behalf of the Gutta-percha Company, and Siemens and Halske had covered conductors with gutta-percha in strips, after the manner of india- rubber ; but much trouble was experienced with this type of gutta-percha covering owing to moisture getting in at the seams. Bewley had the first patent for covering wires, but Siemens' machine for setimless coats was the first practical success met with in this direction. + The late Mr John Chatterton was originally a lead-pipe drawer in Wharf Road. Soon after joining the Gutta-percha Company he applied this form of machine to gutta- percha core manufacture. .• . ,. 302 sun^fARI^•I•: tklegrai-hs. — usually actuated by a screw motion — forces it out ajjfain into a die, throuj^h the holes of which the w ire is drawn ; and, therefore, then draws with it a certain thickness of gutta, according to arrangements, Sucii machines have been set up both vertically and horizontally, the gutta being forced through either the bottom or the side of the cylinder as the case may be.* The objection to a machine of this sort in its crudest form is that air enters the cylinder with the gutta, and thus tends to make a way into its pores — being hot and plastic, whilst inside the cylinder chest — when drawn through the dies round the wire.+ As has been already pointed out, air getting into the body of gutta tends to force its way out under any outside pressure, or under molecular expansion due to increased temperature, the result being what is termed "blowing" of the gutta, leaving holes or chambers which, if sufficiently deep, may be the cause of serious electrical faults, and into which more air may find access, leading to further trouble of the same description. Gray's Gutta-percha Covering Machine.— Howcxcr, in 1879, a patent (No. 5,056) was taken out in the name of I\Ir Matthew Gray, for an ingenious gutta-percha covering machine^bcing a new combination of well-known mechanism—which very perfectly overcomes these difficulties, and which, on account of its general perfection, is selected as a specimen for detailed description here.* It is illustrated in end elevation by Fig. 20, and in side elevation by Fig. 21 ; a plan view is given in Fig. 22. The plastic gutta-percha, when it is brought to this machine, is laid endwise, in cylindrical lumps of about 4 lbs. at a time, between the pair of horizontal steel rolls D and D^ (Figs. 20 and 22) heated with steam or hot water,§ whose axes are in the same horizontal * These usually consist of two cylinders side by side, with a common channel between them for tlie entrance to the die, so that whilst one has just been drawn from and is being recharged, the other full one is supplying the die chest with more gutta for being drawn off by the wire continuously. t It was thought that any defects caused by the presence of air or moisture in one coating could be remedied by a subsequent coating, but this has proved, in practice, to be fallacious. I Mr A. Le Neve P'oster also appears to have been prominent with regard to the application of machinery of the above type for the purpose in question. S The object of these rollers (with their bearings in the main frame f) being heated, is partly to maintain the plasticity of the gutta by again heating up the thin skin, but also to assist in working out the air and moisture from the gutta-percha in the drawing of the gutta between their adjacent surfaces. To further assist in keeping up the temperature of the percha, a shade is usually affixed at a little distance above the rollers where the gutta is inserted. TMK INSULATING ENVELOPE. 303 plane, and which act as a feeding apparatus for sup|)lyinff the material to the rest of the machine. These rolls arc so actuated that they revolve towards one another (their rotary motion being obtained from the main shaftinj,')- «inject of this screw is that, as fast as the gutta-percha arrives in the cylinder, it shall force the gutta uniformly forward * The object of placing a limit to the bulk of gutta-percha supplied to the cylinder is partly to avoid a strain on the wonn or the cylinder. t The speed at which this propelling screw is run is regulated by the cone-shaped pulley P (Figs. 20 and 22), which is on the main shafting. The strap on the main shafting is adjustable on to any section of the pulley, according to the speed required for the screw. This again — as will be seen later — depends on the speed of drawing off the wire, varying according to the thickness of insulation in question. Each section of the pulley usually corresponds to a particular speed of drawing otT such as is adopted for a given type of core. There are certain previously arranged and fixed rates for the screw according to TIIK INSULATING ENVELOPK. 305 aloiifj the leiifjth of the cyliiuler. iiiuler a required pressure, through the entrance of the die chest or "nose piece," connected to it at its further end, throti^'h which the coiuhictinjf wire is bcin^' drawn. Thus, in fact, the die box is continually {\:(.\ with a re^^ular supply of ^utta at an unvarj'ing uniform pressure, rate, and consistency.* As the conducting wire under operation is drawn through a hole of a l-'io. 22.— Gray's Gullii-percha Covering Machine (Plan). certain size at the further end of the die chest, it thus draws with it (under a uniformly high pressure) a coating of a definite thickness — depending on above rec|uiremcnts. In a similar way the speed at which the horizontal rollers are worked to feed the cylinder is also thus regulated — being, in fact, from the same shafting. These rates, together with the speed of drawing ofT, may be adjusted to a nicety so as to give exact results— /.t'., so that the gutta-percha may get thoroughly cooled in passing through troughs; and yet that there shall be sufficient, but not too much, gutta uniformly forced on the wire. * The only mechanical point which limits the speed at which the propelling screw can be run is that of safety. Thus, if it were run too fast, it would be liable to strain, or even burst, the die cylinder by forcing more gutta-percha in than there is room for. On the other hand, in order to give a certain required thickness of coating (as provided for by the die holes), the screw must be run up to a given speed in proportion to that at which the conducting wire is being drawn oflf. 306 SUBMARINE TELEGRAPHS. the pre-arranged relationship between the diameter of tlie die hole to that of the wire — of the plastic gutta-percha, which, under pressure, adheres very firmly, especially as the conductor is first coated outside with comptjund. It is of the utmcjst importance that the gutta be kept thorout^hly warm and plastic — in fact, in a " tacky" (i.e., sticky) condition — rii^ht up to the time that it is applied to the wire, so as to i nsure it hiyinj;' on properly. For this reason, therefore, more or less the whole of the machine is steam jacketed. The motion for driving the rollers and the propelling screw is taken from the main driving shaft G, to which is keyed a worm jf and a spur wheel gK The worm ^ gears into a worm wheel g- on the shaft of the screw propeller c, and the spur wheel ^^ gears into a wheel ^* mounted on a stud axle projecting from the framing !■'. Secured to this wheel ^^ is a spur wheel ^* of larger diameter, which gears into and drives a wheel /i on a horizontal shaft II. A worm /i^ kc)'ed upon this shaft gears into and drives a worm wheel i/ on the axle of the roller D, and this roller is connected with the roller D^ by means of a pair of pinions d^. Suitable provisi(Mi is made for the escape of any air at starting the machine by the receiving cylinder, or chest, being [)ierced at its forward end. The die chest has also an overflow pipe and cock, providing for the escape of any excess of gutta under certain circumstances. When in working order, this machine is as nearly air-tight as possible. Advantages of Gray's Machine. — The great features of this apparatus as an improvement on previously existing machines for covering wires with gutta-percha are briefly : — (i.) The exclusion of air and of more than a certain amount of moisture,* by there being only space for a thin sheet of gutta to be drawn in between the feeding rollers. (2.) An unvarying pressure of gutta being maintained by means of the screw being worked uniformly. The result of this is a uniform supply of gutta, both as regards quantity and consistency — in other words, a uniform homogeneity and thickness of coating throughout. * The ill effects of any material quantity of moisture remaining in gutta-percha about to be applied to a conducting wire in the form of core is the same as that of air ; namely, when afterwards it is driven off^cither by heat, by the pressure at the bottom of the sea, or by being subjected to some abnormal temperature, say, in the ship's hold — spaces will be left in the core, and a little hole, possibly extending to the copper conductor, will be the result. A certain proportion of moisture must, however, be retained in the gutta in order that it may preserve its physical i|ualities, and not decompose. THK INSULATINC. ENVEI-OrF.. 307 General Operation of Covering Wires with Gutta-percha. — \Vc have now described the manner in which the ^t;utta-|jcrcha is led on to the wire, taking the above machine (in use at the Silvertown Works) as a specimen for carrying this out. We will, therefore, now ]jroceed to consider the manner in which the conductinj^ wire is drawn through such a machine f- of a screw, is gradually worked down the cy; nder by hand, thus effectually ])ressing the pure compound through the strainer i ..„ "^e tank immediately below it. t It may be mentioned that this compound is also sometimes used purely for ])urposcs of adherence, as in the case of solid wire conductors about to be covered with guttapercha. Before Chatterton's compound came into use the copper conducting wire was liable — after the subjection of any strain on the core — to start out of the gutta-percha envelope. This would come about owing to the gutta having so much more elasticity than the copper. The percha tends, in fact, to return to something like its former length, whereas the copper remains pretty nearly at its elongated length due to the previous strain. However, by the application of Chatterton's compound to the wire, the gutta- percha was soon found to adapt itself to the copper wire in this respect. Where the gutta-percha is applied in more than one coat it is highly desirable that the successive coats should be equally well united ; or the inner coat alone would conform with the wire as above, and a general disruption occur. THK INSULATING ENVELOPE. 309 The wire is led into the compound tank T (Fig. 23) through a frame with holes sufficiently large for the passage of the wire, and out again by another frame with holes of a size just large enough to permit of a very thin coating, or film, of compound remaining on the wire. It is essential that this compound shall be of exactly the right thickness, as if too liquid it would not adhere properly, and, if too thick, it is unwork- able and liable not to produce satisfactory or uniform adhesion.* The so-compounded wire, on its way to the gutta-percha covering machine, passes over another set of gas jets so as to warm up the compound immediately before-hand in order to effect a satisfactory union with the gutta frcMTi the die box of the covering machine. We have already dealt with the feeding of the gutta-percha die chest by the covering machine. We will now, therefore, consider how the gutta is laid round the wire to the required thickness by means of the said, specially constructed, die mould. The wire passes through the middle of the die box is (Fig. 24) by a pipe. a b Fig. 25. — Die Box of Gutta-percha Flc. 26. — Die and Ca|) of Gulta- Covering Machine. percha Covering Machine. The gutta-percha, on arriving at the ncse-piece, enters the die (Fig. 25) inside by the channels each side of it. It is not allowed to come into immediate contact with the copper wire, as by so doing it would, by its weight, be liable to bend the latter, and ihur, the gutta would not lie round it evenly. The wire leaves the pipe by a nipple (shewn in a of Fig. 26), and then passes through a corresponding hole of a cover, or cap (shewn in b), there there being about ,V inch space between the nipple and the hole, which is also slightly larger than the nipple. The gutta-percha is, at the same time, forced through the channels on each side and through a series of very small holes about J inch in diameter. Having passed through these under great pressure, the gutta then meets the compounded copper wire in the allotted space between the die and its * The quantity used for the required film is extreinely small, and is, for instance, represented Ijy somewhere about 1 lb. per N.M. for every successive coat— maintaining the same f/i/ci-ws': for each— in an ordinary {U core. This quantity is always included in the total weight of the dielectric. 3IO SUHMARINE TELEGRAPHS. cap, which is just sh'ffhtly in excess of the len<^th of the nipple. The size of the cap holes are arranged according to the thickness of coat required. The wire, as it passes from the nipple to the cap hole, draws with it a coating of the hot, plastic, gutta-percha, which is pressed round it under considerable force, in the small space between the end of the nipple and the cap hole. A final pressure of the gutta-percha round the wire is effected in passing through the cap hole immediately in front of the trough.* Cooling and Hardening Process. — The coat of gutta-percha having been applied round the wire in a hot and plastic state, the wire — which has now become what is termed " core " — is liable to get damaged as regards the insulating covering during its further movements, especially on being drawn round the collecting drum. Steps are, howevci at once taken to cool, and so harden, the gutta-percha covering. Accordingly the covered wire, on leaving the die, is drawn very slowly through a long trough, some 200 feet in length (the near end of which is shewn in Fig. 24), filled with clean water, maintained at an exceedingly low and constant temperature. The temperature aimed at is ver)- usually 40 F. (4.4^ C). This should not at any rate exceed 55" F. VVell-water answers the purpose; but large cable factories usually employ refrigerating machinery for feeding the various troughs (belonging to different machines) with water at the required temperature. This consists of ether machines worked b)- hori- zontal engines, as a rule. According to a very generally adopted system, the core is drawn down the length of this trough (Fig. 24) to a drum at its further end, which, being driven very slowly from the main shafting of the shop, gives the necessar)- * It is not improbable that means could be adopted for increasing the resistance of newly manufactured gutta-percha to its full limits at once — i.e., to as high a figure as mechanical set, or drawing up, increases it in time. This might be effected by each coat being, at this stage, drawn between two rollers at various consecutive points — say, along the trough. The result would be the forcing out of moisture, especially at the first set of rollers just beyond the die. Care would, of course, have to be taken not to drive out too much moisture, or the material would lose its gum-like qualities, ard would become subject to serious decay by absorbing oxygen into its now loose pores. The advantage gained would be that of effecting the mechanical set without keeping the core back after manufacture and before testing. A certain amount of drawing-up action is at all times desirable to render the material durable. It is possible, moreover, that by this means an inferior and cheaper insulating substance might be rendered suitable, mechanically and electrically — as regards capiicity as well as resistance. TIIK INSULATINC; ENVKLOPE. 3II hauling-off motion. The core takes one turn round this drum, and is then drawn back aj^ain through the trough and round another drum just above, near the covering machine. It then repeats its journey down the trough to the chum at the bottom, and, after passing round rhis, it once more returns up the trough and half-way down again to a large carrying drum mounted on a high framework or scaffolding. This reel is revolved by belting from shafting under the water trough, its rate of motion being maintained in proportion to that of the other intermediate hauling-off reels worked from the same shafting. On this last reel the core is finally collected, by a process of automatic coiling, ready for subsequent operations. To ensure even winding, the core is led to this collecting reel between upright guides, which are moved to and fro by a double-threaded screw parallel to the axis of the reel. The belting, which transmits the required drawing-off motion to all the various reels, is usually made of gutta, bands of this material being naturally at hand. In passing three times up and down this trough, in the manner described, it is thus, in reality, passing through as much as some 1,200 feet of water at about 40° F., and as the drawing-off motion is very slow, the hardening effect is quite perfect, though the precaution is usually taken of testing the covering in this respect, by hand, from time to time. Examination of the Insulated Wire. — The core now passes through a process of examination, in a special room, with a view to the detection of any possible flaws. This is carried out by the core being uncoiled from its reel on to another, and on the way being held between the fingers by an experienced workman, who, by practice, becomes very expert at detecting by touch any defect in the insulating covering. In the event of a hole, crack, or any sort of mechanical irregularity being discovered, the place is made good by the application of a hot iron to the surface, or by slightlj- warming the gutta over a wood naphtha lamp and >vorking it up between the fingers. If necessary, fresh gutta-percha can, of course, be .added to the weak spot. Should the defect consist in the presence of an)' foreign substance, this is, of course, extracted. Measurement. — Where this completes the entire core — i.e., where no further coating is required, or where the total thickness of gutta is laid on at one operation — it is then al.so measured whilst undergoing examination. In the event of sub-secjuent coats, however, being applied, this measure- ment is more usually only taken on the completion of the entire core, after 312 SUBMARINE TELEGRAPHS. it has received all the strain which comes into force in drawing off for each process. Where subsequent coats are to be applied, the core is very commonly kept for one or two days before it is taken to the covering machine f(jr its second coat, for purpcjses of maturing. Thickness of the Covering. — As regards the thickness of the insulat- ing covering, theoretically speaking — .so far as electrical requirements go — a thin film, or " varnish," of gutta would be all that is necessary in many instances for the purposes of insulating the conductor sufficiently, as well as for acting as an efficient dielectric from an electro-static capacity, and signalling, point of view, especially if the jute packing be worked up as a dielectric substance in the manner already pointed out. For efficient mechanical protection, however, something more than this is necessary, though the minimum thickness considered e.s.sential has been gradually reduced down to something much less than used to be — in fact, even for submarine purposes, cores with a thickness represented by 59 lbs. per N.M. gutta-percha, to 47 lbs. copper, have been constructed.* The ordinary core for lengths of submarine cables below about 1,200 N.M. is 140 lbs. gutta-percha to 107 lbs. Cu. It used to be thought that 160 lbs. gutta + was the least that could be prudently relied on, for mechanical reasons, with that sized conductor. J * A core of the above dimensions was made at the Silvertown Works in 1890 for a lighthouse cable laid between Tory Island and the mainland, off the northern coast of Ireland. Again — besides the Brest-St Pierre " P.Q." cable — there is the case of the Com- mercial Company's Channel cables of 18S4 and 1885 — respectively, from Canso to Rochefort, from Waterville to Weston, and from Waterville to Havre. Both of these have cores represented by 70 lbs. copper (solid wire) to 75 lbs. gutta- percha per N.M. The amount of insulating material in either of the above cables is, no doubt, quite sufficient for short shallow-water sections — indeed a like practice might be extended elsewhere with perfect safety. t Other instances of a similar waste of material have occurred. For instance, the author has met with a case in which a thickness of gutta represented by 2,45 lbs. per N.M was ap- plied to a 130-lb. conductor, where 170 lbs. gutta for the insulator would have been ample. I In practice, as a matter of fact, this usually resolves itself into a question of the least number of coatings deemed safe. The gutta is very generally laid on the conductor in as thin coatings as possible, so as to decrease the chance, as far as may be, of weak- nesses escaping notice. Three coatings, each of 30 mils, thickness (equivalent to about 140 lbs. gutta-percha), is considered by many to be the least number which can be used to safely insulate a conductor of 107 lbs per N.M. However, the insulation of certain cables laid in the Gulf of Mexico in 1881 — though of 166 lbs. per N.M. (to 107 lbs. Cu) — was constituted by two coats only. There seems to be no reason why the two-coat dielectric should not be ample for many short sections, even up tn 750 N.M. As a signification of mechanical fitness, it may be added that all the Post Office underground conductors have, for many years, been covered with only two coats of gutta-percha. THE INSULATING ENVELOPE. 313 Relative Advantages of Single and Multiple Coats.--In the earl>' days of insulated conductor for underground lines, and in the first sub- marine line laid from Dover to Calais in 1850, the insulating; coverin' rate — witli disastrous results. In some of these costly experiments the Stockholm wood tar of Chatterton's mixture was substituted by coal tar. This tended to dissolve the jjutta ; besides which, holes were blown in the ^^utta-percha envelope when under pressure, on submerjfcnce. In other instances the naphthaline used as a .solvent cau.sed similar trouble by evaporation. In any case the insulation resistance of the j^utta-percha covering was materially reduced by being in contact with a mixture containing coal tar. ITnfortunately these bad features did not, as a rule, come to light till after the core had been submerged under the pressure of the ocean. .After pa.ssing through the tank of compound, the core is then led throu^Ii the covering machine, and thus, by means of the compound, a fresh layer is firmly united to the previous one. The core is then again slowly drawn through the trough of cold water — three times, in fact — preparatory to being again automatically coiled on its collecting drum and once more examined for the fresh coat. Examination after Application of each Coat. — On the completion o( each successive layer, the core undergoes the same rigid examination throughout its entire length, and any flaws discovered are made good. Both of these processes have already been described. Measurement. — Whilst this examination of the core is being per- formcfl — by being rapidly run through the hand during drawing off from one reel to another — it is at the same time passing through a process of measurement. This is effected in a doubly certain manner, by both the drum that it is being hauled off from and that which it is being hauled off oft to, each having a revolution indicator in connection with their axles.* Moreover, an additional measurement is also very often obtained during the process of covering, by an indicator being geared into some part of the hauling-off machinery — not uncommonly in connection with the drum at the foot of the cooling trough. Weight of Insulation. — Besides the length measurement being taken, the weight of each completed coil is also tested. By deducting the pre- * A comparison of the lengths obtained on the completed core (and on each individual coat) with that given by the conductor alone during the stranding process, shews the amount of stretch which has been involved, in the meanwhile, by "drawing off" during the operation of covering. ;._^.. ;^^_ Till", INSULATING KNVKLOI'E. 319 viously measured weight of the length of copper stnind forming part of this coil from the total weight of the ccjij, a knowledge is obtained (by inference) of the weight of tlu- insulator alone. This is not very accurate, as a rule, inasmuch as the machine used for weighing the entire coil is not by any means as sensitive as that for measuring the conducting strand by itself It is, however, the only means of arriving at the weight of the dielectric* The weight of the flielcctric is specified for (in addition to that of the conductor) as a further check on the material employed to meet the specified electrical rci]uirements, besides ensuring the mechanical qualifica- tions, as regards dimensions, being properly carried out.f Outside Diameter of Core. — Similarly, the outside diameter of the completed core is usually specified for (in addition to that of the con- ductor), and is checked from time to lime for this, and, still more, to ensure the mechanical proportions and individual requirements being secured. There is an additional reason why the weights should be specified and tested — i.e., because the cost of materials is always estimated and made out by weight. Moreover, it is usual to measure the diameter of the completed core (the conductor having been previously gauged), or on a certain proportion of the coils, at any rate, to see that it is up to specification. It is highly desirable — as in the case of the weights — that both the diameter of the conductor and that of the completed core should be specified for, not only for mechanical reasons, but also as a check on the method of securing the required limits of capacity and resistance — i.e., by a sufficiency of dielectric material, rather than specifically. The difference between the conductor diameter and the outside diameter gives the thickness of dielectric. Recording of Data concerning each Coil. — Every coil, after being measured and weighed (and in some cases gauged), is given a rotation number from the commencement of any particular undertaking, and various information respecting it tabulated under different headings, "* A nautical mile is always taken as the standard length in this respect — as in other matters — partly on account of convenience, and partly because it is a fair mean length such as can be measured within a reasonable percentage of accuracy. + It is very usually stated in specifications that the average weight of the entire length of the dielectric shall not be less than so much per mile — or within a certain percentage {generally 5) thereof. 320 SUBMARINE TELEGKAI'HS. besides being noted in a book for after-reference. These particulars usually consist of something like the following : — (a) The number of the coil ; (fi) its length in yards and nautical miles ; {c) weight of conductor and weight of dielectric ; (d) date of leaving covering machine ; (r) date of immersion in water at 75" F. ; (/) date of testing electrically ; (g-) date of leaving 75' F. tanks for serving shop.* Rate of Covering. — The particulars regarding length and weights are stamped on a gutta-percha (or leather) label which is then attached to the coil itself As regards the rate at which a conductor is covered with gutta-percha, the wire is drawn off through the "coring" machine on the iit'cnr^q-c a.t a speed of 750 yards per hour.f This is, in fact, the rate of covering with one coating, for the \ery ordinary type of core constituted by a conductor of 107 lbs. copper per N.M. and a dielectric of 140 lbs. gutta, made up in three separate coats. This amounts to about 3 N.M.iJ per day of twelve hours. 5 From this it will be seen that the ordinary machine with six dies — capable of covering six wires at a time with a single coat — can cover about 18 N.M. of wire with a single coat, in the course of a twelve-hour day's work, or 18 N.M. of three coats in three days. Il Where the said covering is * It will readily be understood that some of this information has to be filled in afterwards. + In the case of the (Iray and Gibson covering machine previously described, the corresponding speed for the horizontal rollers forcing the gutta into the receiving cylinder and for the worm forcing the gutta-percha into the die chest is about fifteen to seventeen revolutions per minute. I It may be remembered that it is on these grounds that the complete (stranded) con- ductor is usually made up in about this length. If the length of the conductor was shorter than that which could be covered in a continuous working day, scarf joints in the strand would be involved. These take a sensible time, during which the gutta at the end of the covered length would become more or less hard. If, on the other hand, the length of the strand were longer than could be properly dealt with by the covering machine during the time of continuous work, on resuming, a joint in the covering would be involved between the already hardened gutta (which would require abnormal heating) and the gutta in a hot plastic state. S It should be added that, as the wire is not usually supplied in any iwnc/ lengths, the length of each completed coil varies. It is sometimes the practice, however, to specify that each coil shall be of an exact length — 2 or 3 N.M. as the case may be. This has the effect of simplifying calculations in reducing values to the standard unit, length I N.M. On the other hand, however, this involves the conductor being cut at an exact point, leaving a number of odd ends which either introduce waste or increased time and expense in jointing them together. II Were an attempt made to start on another coat in any one day, a further change of dies would be involved— apart from other objections. THE INSULATING ENVELOl'K. 321 constituted in its entirety by three separate coats, this is equivalent to about 6 miles of completed core in a day. At a lar^e cable factcjry there will be somethin^^ like half-a-dozen such machines, the result being that somewhere about 50 N.M. of single-coated core can be turned out during a working day. This, however, largely depends on the thickness of each coat, as already explained. In any ca.se, the rate of core manufacture should be well ahead of the sheathing. There .should, in fact, be no chance of the cable depart- ment having their machines standing still for want of core to feed them with. o Mechanical Tests. — It has not been the custom, as a rule, to apply any actual mechanical tests to the completed core any more than to the conductor alone, though on the last " Anglo" Atlantic cable of 1894 the core (Fig. 27) was tested for breaking strain. This core, composed of 650 lbs. copper and 400 lbs. gutta-percha per N.M., J'"^- 27-— Core of 1894 • r 11 1 c \ 1 • "Anglo"' Atlantic bore a stram of 1,000 lbs. before breakmg. Cable. The fact is — as regards breaking strain, at any rate — the mechanical qualities of the core can .scarcely be said to come into the question in practice. This is owing to the circumstance that the extensibility of the gutta-percha is such that its point of rupture is quite different to that of the rest of the cable ; and, therefore, it does not tend to increa.se the total strength of the cable, however high its break- ing strain may be. Thus, any breaking strain obtained for the core is really that of the conductor alone ; and this would be quite insignificant as an addition to that of the rest of the cable, even if it came into action at the same moment. Maturing. — The core so completed is usually kept — for maturing purposes — often as much as six, or even fifteen, days before anything further is done with it ; but sometimes only one or two, if required at once, or where further maturing might put it on the wrong side of the specification.* Electrical Tests. — With a view to ascertaining whether the work of * The specification should always state the length of time after manufacture at which the core is to be tested. This is desirable, in order that the results obtained may be absolutely independent of the influence of this important, and varying, factor. 322 SUBMARINK TELKGRAPHS. covering the copper conductor has been successfully carried out,* the core is next taken on its large wooden carrying drums to the core testing department, where the coil is bodily submerged in cisterns, or tanks, filled with frcsh-water,t uniformly maintained at 75" F., with the help of steam circulating through pipes, or else by a double-bottom steam-jacketing system. The core is subsequently tested whilst in the tank of water, but it is first kept immersed there for at least twenty-four hours. This is in order to give the water a fair chance of percolating at any weak spot to the con- ductor, and also to ensure the core truly taking up the fixed temperature of the water. It is very usually stated in the specification the length of time after immersion in water or after manufacture that the core is to be tested — or, at any rate, the minimum length of immersion (usually twenty- four hours) is given. The length of time necessary to meet the above requirements varies, of course, with the type of core, a great thickness of gutta taking longer than a small one ; indeed, thirty -six, or even forty- eight hours, may sometimes be found desirable ;:J but with an average core, twenty-four hours' immersion should be sufficient, as a rule. The import- ance of this is only equalled by the importance of rigidly keeping the water at the temperature named. This temperature is taken as a standard, or basis, for subsequent compari.sons of electrical tests: the factor of the varia- tion of both conductor and dielectric resistance by temperature is thereby eliminated. § 75 F. was selected as a fairly convenient temperature for reproduction under any circumstances. The core then, whilst still under water, passes through a verj- severe and exhaustive system of tests regarding the electrical condition of the core.|| * It would be useless to make this test in air, since even without any insulator at all the current does not pass readily into air. + Theoretically, salt-water would answer the jiurposc better, being a superior con- ductor electrically and a more perfect imitation of what the cable has to experience on submergence ; but there would be difficulties to effect this in practice. I Messrs Siemens Brothers arc in the habit of keeping their core for two days (forty- eight hours) before testing it. vj Thus — a record being kept of the results of tests on each coil of core as made at the factory — the electrical value of any portion of the cable, at any other subsequent tem- perature, may be compared with these original values (as core) at the standard temperature, by applying to the observed value the coefficient for the reduction of the resistance to the standard temperature. II This was carried out systematically for the first time by Messrs Hright and Clark over the manufacture of the first Persian Ciulf cable of 1863 ("Notes on Telegraphic Communication lietween England and India," by Charles Hright, F.R..S.E., Jouiiuil ., that it will be reduced by an increase of voltage — but it has been found that such is not the case. As long as the dielectric acts as a conductor only, there being no sparking action through it, no change in the insulation resistance can be detected. + The same system is now adopted at all cable works, although (as already shewn) the period of immersion is in some cases different. At certain factories— notably at the Telegraph Construction Company's Gutta-percha Works — the core is also tested finally at a lower temperature of 40 or 50' F., with the object of more certainly detecting any small incipient faults. This is based on the principle that weakness in an insulating material reveals itself moie readily in an electrical test when the material elsewhere offers a high electrical resistance, as would tend to be the case at a low temperature. Moreover, if a temperature more nearly approaching that of the sea bottom be taken as a standard, the error necessarily occurring in any subsequent reduction to the standard temperature — owing to a general coefficient not being applicable to any particular batch of gutta— is considerably lessened. On the other hand, the higher the temperature, the greater the general strain put on the electrical resistance value of the core, besides being a severer test mechanically, though a minute fault may not be actually as easy to discover. It must also be remem- bered that in tropical climes, at shore ends — up to the hut —the cable often has to experience exceedingly high temperatures, when, for instance, unavoidably running under a long stretch of dry sand. Hence 75' F. is usually adhered to as the standard temperature. ' 324 SUHMAklNE TELKORAI'HS. polarisation of the dielectric. The elcctrificatifin of the dielectric is more closely watched at this stage than at any other. Jiesides the above test on the insulation, the first test made is that on the conductor for its resistance. Perhaps the main object of interest in testing at this juncture is the electro-static capacity of the completed core. It is imjjortant, at the earliest jjossiblc stage, to know, for signalling purpo.ses, that it is not above the specified limit in the above resjject. This, like all the other electrical tests, will be found detailed elsewhere.* Improvements in Manufacture. — The manufacture of cable core has so far improved within the last twenty years, that a core with an insulator weighing 150 IVjs oer N.M., which then had a dielectric resistance of some 250 megohms per N.M. at 75" F., can now (principally owing to greater l^erfection in the joints) be obtained giving 2,000 megohms. This would not necessarily imj^ly perfection or durability with regard to electrical and mechanical qualities, as already explained ; though a moderately high insulation may usually be taken as a sign of excellence of material for the ])urpose. Re-making Core. — Where a high capacity, due to insufficient mastica- tion, is accompanied by a dielectric resistance some way above the limits, this can be remedied by the somewhat troublesome course of making the core up again after the gutta has been strijjped off and re-masticated. + Care must, however, be then taken in getting the reciuired ca|)acity, that the insulation resistance is kept within the required limits each way, where .so specified. Standard Electrical Values at 75 F. — These tests are taken as the standard electrical values of the cable for purposes of after-comparison, any subsequent tests made being reduced to the corresponding value at the .same (standard) temperature, 75° F. Records. — The results of these standard tests are recorrled on special forms. Sometimes, indeed, curve sheets are drawn up for shewing tiie in- sulation resistance from week to week after original manufacture (to bring * .See Mr H. I). Wilkinson's up-to-date work, published at J/m lUcctrician office ; also Kenipc's " Handbook," ibid. ; still more a fortbcominK treatise by Mr J. K. Young on " KIcctrical Testing forXele^^raph Kngineers," of the same series as Mr Wilkinson's book. t Old gutta may be rejuvenated in this way, by being mixed afresh with new gutta containing the essential oils, and (he whole masticated and "worked up" together. THK INSULATING KNVKLOPE. 325 to li^'ht the improvement by aj^ej, as well as curves settiiif,^ forth the rate of electrificati(Jii* (liiriii|^f a certain tcst.f After any coil of core has been tested, if it is " passed," it is kept under water and screened from lif^ht as far as possible until it is required for use in the cable. Placing of Coils in a Section. — Owing to the variations of^utta now in the market, and to the enormcjus difference in the electrical results accruing from different mixings and methods of manufacture, there is often a great discrepancy between the dielectric resistance of the various coils for a particular cable order. Some coils may have an insulation of ICX) * PZlcctrification — more closely definecl ;is absorption -vn'n.y be viewed as something between capacity and conduction, or leakage. It takes place very much (|uicker at low than at high temperatures. Kioni a wide range of experiments no broad or definite law can be arrived at regard- ing the relationship between the specific resistance and rate of electrification in any given insulating material : in other words, the absorption rate of a gum cannot be said to betoken any particular specific resistance. .Speaking i|uite generally, however, rapid absorption is most usually an accompaniment of high resistance, and iiice TcrsA — just as it is more liable to be with a given gum at a low than at a high tenii)erature. Paraffin wax, india-rubber, and gi.t'a-percha, when laid at the bottom of the ocean, are all examples of this in comparison with gutta-percha under normal, factory, conditions, as regards temperature, pressure, and age. It should be explained, however, that a material possessing a high rate of electrifica- tion is synonymous with saying that it absorbs very little electricity, and that what little is absorbetl soaks in within a very short time — i.e., at a high rate. With such a material then, the true insulation resistance — denoted solely by a permanent leakage current — is arrived at comparatively C|uickly. It seems ])rol)ablc that there is a closer connection between dielectric absorption and sign.illing speed than is at present known of; and that rcs(;arch in this direction might lead to imjiortant results, 'rheoretic.ally, it would appear that from a tv//r?t7/)' standj)oint, a rapid absorption ;>., a small total absorption — -should be favourable to a high rate of working. With p.evailing practice, however, this does not appear to enter into the problem : moreover, the significance is not necessarily a good one with all gums ; there is another side to the r|uestion as is shewn further on. The ^jreat point to be aimed at, and ascertained, is that the electrification i.e., absorption shall be perfectly steady in its gradual decrease subsequent to battery application. + Air condcMisers have, of <()urse, no absorption, and Mr R. T. Cdazebrook, F.R.S. (H.A. Report on Klectrical .Standards, 1892), has compared mica condensers with them. He found the aftpurcnt capacity of the latter i|uite I per cent, smaller when tlie battery contact was very short than when the contact lasted for from five to twenty seconds. Clearly, then, a mica cable compared with an air condenser in the usual way at the factory would have a working speed -say 1 per cent. — better than that calculated, when the rate of signalling is hinh, and the contacts, consequently, short. Though we have no mica cables in actual practice, there seems to be some interest —or even importance- -aW-acXwliS. to the c|uestion whether the cflfect is not in the same direction in the everyday comparison of gutta-percha cores with mica condensers ; and, if so, to what extent .' - -■ 2 " 326 SUBMARINE TKLKCKAI'HS. megohms per luiut where others have as much as 3,500. In such instances, the coils are arranged and joined up in order in the cable, in order that a coil with a comparatively low insulation may be balanced b)- one with a high resistance following it ; so that, in the event of subsequent cutting, the average dielectric resistance will be about the same for any part of the entire line. Historical Records. — In Appendi.v I\^ at the end of this Part, Form B shews the .sort of tests and general data that are made and tabulated in connection with a completed cable section when laid. A step-by-step statement of the factory " C. R. " (conductor resistance), " D. R. " (dielec- tric resistance), and " I. C. " (inductive capacity), of each coil must al.so be drawn up for every laid section — just as it is done for every sheathed factory section ; and this sh(juld be accompanied by a record of all bottom temperatures taken at intervals along the length of line as laid. Selection of Gums. — To ensure the right electrical results being obtained, .some systematic method of testing experimental proportions t)f gutta are essential. One plan is to make up .several comparatively short coils not e.xceeding a quarter mile in length, each covered with a certain species of gutta. From the results obtained with each, the proportions of each gutta to be used to meet the sjiecification of the core may be decided on. Another plan is to test actual lumps of gutta between plates to which a connecting wire is attached. In any case, assigning proportions — such as produce the preci.se required result — is not .so simple a matter as it might, at first sight, appear. Requirements. — The e.xact insulation resistance of a material is only of importance in .so far as it .serves to signify the material being what is wanted, with a given thickness for mechanical requirements. The fact is that, apart from the necessities of electric insulation, a dielectric resistance, within certain limits, each way is significant of a certain, known, durable, gutta-percha material such as cannot be recognised by ocular external e.xamination, or by any other test than an electrical one. The actual re- quirements, as regards electrical resistance, y^^r ///f successful zvorkiiig i^i a submarine cable, do not require to be nearly so carefully looked after — that is to say, any gutta-percha would probably offer a sufficient specific resistance, and usually much more is obtained than is really necessary.* * Indeed, as is pointed out elsewhere, a comparatively low resistance insulator would — if it could be relied upon— more closely realise the theoretical requirements of high speed signalling on a long cable. TIIK INSULATING ENVELOPE. 32/ As a sign of a durable form of gutta, it has alrcMcly been pointed out that too high a specific resistance is every bit as bad as too much the other waj'. Indeed, extremes in either (hrection are a sign of the addition of other materials, or of widely different gums ; * but a comparatively small diver- gence above the mark generally suggests tiie presence of a more or less large proportion of resin, which, when in good condition, usually has a higher resistance than gutta-percha. -As has been shewn previousl)-, resin readily eva]jorates into dust, and is, therefore, much to be avoided. It then not only has a low resistance, tending to absorb moisture, but also brings about general decay and mechanical destruction of the core, owing to the jjorous holes and cracks so set up.t Thus, it is quite as important to ])ut a limit on the resistance of the gutta-percha as it is to specify a minimum ; and this, nowada)'s, is almost invariably done by the engineers to the owners. In driving off moisture, the degree of mastication adojjted has a very considerable bearing on the resistance of gutta-percha, besides also govern- ing its capacity. * It will be seen, then, that either of these electrical require- ments may be re.adily met without signifying the employment of a durable material. § Specified Limits. — Thus, properly speaking, a specification for the limits of dielectric resistance on each side should be based on experiments with all the gutta to be obtained in the market at the time. With the knowledge of what are the most suitable and durable guttas amongst the above, II samples of those selected should be electrically tested. After * The admixtuie of a large number of widely different gums usually constitutes a non- liomogeneous, and therefore noii-dural)le, gum. This would be still more implied if other than gutta-percha form part of the mixture. t Each of these in themselves constitute more or less of a fault in insulation if exposed to moisture. I It does not always follow that the resistance of gutta-percha (or of india-rubber) is decrciised by water absorption. In Willoughby Smith's process more moisture is driven off (by further mastication), but the dielectric resistance is lower- not higher- than "ordinary" gutta. As a broad rule, however, with what is termed (?r' be sub- mitted to electrical tests whilst actually under i^rcssure. The hydraulic pressure is applied by means of force-pumps, and its degree is adjusted according to the depth of the ocean in which the particular cable is about to be laid, the maximum available strength of pressure being equivalent to about 8 tons on the square inch* — well outside that of oceans' depths so far within our knowledge. The above test is more particular!}- ap|)!icablc to the sjstem of laying all the gutta-percha on at one operation, whether by a multiple die or other- wise. This is so, owing to the increased chance of air bubbles and flaws generally, or of foreign matter otherwise escaping detection till laid at the bottom. It is also, in a less degree, applicable when the gutta is laid on in separate coats, unless an electrical test is made as each separate coat is applied. The core may very suitably be thus subjected to hydraulic pressure whilst undergoing the already described standard tests in water at 75 F., or else the electrical test may be applied to the core soon after it has been subjected to the pre-arranged pressure. In an)- case it is well to keep the pressure on for .some time before noting the effect on the dielectric resist- ance, inasmuch as the application of pressure has the effect of increasing the temperature for the time being ; and consequently any alteration in resistance during that period would be partly due to the change of tem- perature. Similarly, the withdrawal of pressure tends to temporarily lower the temperature of the water, and this in itself would increase the resistance. Thus, sufficient time must be allowed for an accurate idea of the temperature to be obtained, so as to make the necessary correction. This test is thought by certain authorities to be not only unnecessary in the present day — owing to the decreased chance of air bubbles, and other defects, with improved manufacture — but also actually objectionable, on the ground of tending to temporarily mask faults as well as to divulge * Four tons per square inch represents, however, the pressure more ordinarily applied. Tin: iNsuLATiNf; envklope. 331 them. The late Mr Willouf^hby Smitli shewed this to be the case in the course of some exhaustive experiments many years ago. VViiat is perhaps of still more importance is the fact that instances are known where the insulation has been pcrmancnti)' damaged by the pressure test.* In any event, it is a somewhat expensive process, when the high pressures are reproduced as involved b>' the depth of the ocean. This, owing to the great strength necessary for the tank in order that it may with.stand the heavy strain to which its walls are subjected by the pressure of the air, or water, until the required pressure is reached as indicated by the gauge. It is, however, a plan which has many points in its favour. High Proportionate Cost of Gutta-percha Envelope: Reason for Length of Chapter. — If this chapter on gutta-percha and the gutta-percha covering appears to be unnece.s.sarily length)-, it must be remembered, on the other hand, that the cost of the gutta-percha dielectric in a cable forms a large [iroportion of the total cost. Moreover, there is the fact that this part of the subject — i.e., the construction of the dielectric — has never been dealt with at all fully in any jjrcvious treatise. * On the other hand, there arc those who consider that pressure could be made to have a /£V-W(«//(V///)' /////rw/;/^'' effect on the resistance of gutta. This is supposed more especially to h^. the case with chemically impure materials of inferior quality. As some of these have quite a low electro-static capacity, it would seem that a field of research was opened up here for elucidating the |)roblem of high speed, cheap, but durable, cables, and for meeting the requirements of long-distance submarine telephony. The difficulty in these matters is that the experiment can only be put to test in a practical way when the entire cable is made — aye, and laid at the bottom of the ocean. 332 SUliMAKINE TKLECIKAI'HS. Sl'XJTION -. — lNliI.\-KUIilli:K. Where and How Obtained. — For submarine piirposcis, the only other material which has been in practical competitii)ii with {^iitta-pcrcha for the dielectric, is iiidia-riibber — or caoiitclioui, as it was originally called.* The importation of this gum to Kurope dates back- to the c(jmmence- ment of the eighteenth century. La Condamine, during his mission to i'eni, in the year 1735, was the first to make it known. India-rubber is jjroduced by the desiccation of a milky saj), which e.xudes from incisions made in trees of a certain species. The most highly priced rubber comes from the central plains of South America, watered by the Amazon and its tributaries. Para, Clara, and (latterl)-) Manaos in the Brazils are the main sources of supply. ' lis is alw.ays known in the trade as I'ara rubber, and is superior to rubber from other countries, especially for insulating purposes, largely on Jiccount of the more careful and reliable method of collection (Fig. 28). When transported from these countries, it is found to be much freer from foreign substances. The lum])s in which it is collected are usually loaf, or bottle, shaped, but occasionally — as after overflow from the collecting cups — in round balls called negro, or nigger, heads. These are not so clean, and more liable to decomposition than the fine kind, being subject to the heavy rainfalls, as well as to the admixture of bark, earth, etc., from the tree, and the ground on which it stands. The trees which produce rubber gum arc the Siphoiiia or Jfevea, belonging to the family of Eiipliorbiaceie ; chief among these being the Siphon in elastica (Fig. 29) or Hcvca guayauliisis. Of other kinds of india-rubber trees, the following are the most widely distributed : — Qjsttl/oci elastica, found in Venezuela, New Granada, Ecuador, Peru, I'anama, Costa Rica, Nicaragua, Honduras, and Mexico, yielding rubber of inferior quality, but which is frequently — and often necessarily (for mechanical, as well as economical, reasons) — mixed with the Para kind ; Ficiis f/asliaiSjf met with in Java, Madagascar, Assam, and Australia; ■* India-rubber — though of a far less oily iiaiure ihan gutta-percha — contains, as a rule, a small quantity of oil known as " caoutchoucine." t This is the species that is so commonly domesticated in our homes in this country in plant form. IJeing discovered in the Indies in the first instance, it is supposed that this tree gave the name of india-rubber, partly on the above account and partly because it was found when solidified to possess the property of rubbing out pencil marks. [Plate X\'II. I'll;. aS,— Coilctliiiii cil tlie liiico ullho Iiuliarulilicr 'Ircc in I'.ira. [ Tofue /*. 3.^2. [Pl.ATK -Win. Kic. 29. — The Siphoiiia H/ns/iia RiililK-r Tree. iTofacc t. .U2 {i\fUr riaU XV/L). TlIK INSL'1,ATIN(; KNVKLOl'i:. 333 Urceola elastica, confined to the Malay Archipela;4o, and |)rinci|)ally found in liornco,* Sumatra, and l'enan^^ The latter variety is a sort of creeper, some- what similar to the vine in aijpcarancc, having; branches growinj,^ to a length of some 200 feet in the course of five years, though the trunk from which they s])ring rarely exceeds a few feet in height : it yields annually about 60 lbs. of rubber. Mozambi(|ue rubber is the least .sought after : the natives wind it up on small pieces of wood, thus forming the spindle-shaped masses brought to ]'",urope. Contrary to the practice in vogue for gutta-percha, .so far as J'ara rubber is concerned, the trees are left .standing, and merely notched with a hatchet, a trough, cup, or some such vcs.sel being ])laced under each incision to collect the .sap as it oozes out. About a (juart of rubber is thus obtained from a tree in the course of a morning.+ The sap is then dried in the sun. With Para rubber the i)ractice is to smoke it, instead of sun-drying. This smoking has much the same effect as smoking a ham or a haddock, the acetic acid acting as a preservative. • » Collection — J'hc method ot collection and its subsetjuent purification from clay, sand, grit, etc., is, in fact, in many res|)ects, very similar to that tjf gutta-jjcrcha,^ both being hydrocarbon gums.^ Though the mastication rccjuired (in the case of Para rubber, at any rate) is rather less c.\pensi\e as a rule, the after-treatment is always much more elaborate and com- plicated ; for, unlike gutta, a number of other substances — varying in character and proportions — require to be ini.xcd with it (which require careful selection) in order to render it suitable for the |)articular ])urpose for which it is about to be used,' of which there are many and various ; * The gutta coming' from lloriuo is usually ronsidercd second l)cst to that fnini I'aia, and tliat wliich is hiou^ht in \\w^i\ ((uaniitiis from Senegal (West Coast of .Africa) perliaps third host. The latter is in)|)r()ving in (|uality. t The African, East Indian, and Central American gums arc, however, collected in a much rougher manner. In Central America the tree is sometimes felled and "ringed" at intervals, the milk being allfuved to f.ill on the leaves placed under the trees. This is a brutal method of (olleclion, as all the decomposed vegetable matter 011 the leaves and bark is inised up with the rubber and tends to shorten its life. In the other countries named, though the method of collection is less crude, no trouble is taken over the purification. \ On the other hand, a certain ilifference of treatment is involved by the fact that, whereas gutta is naturally more or less plastic and not very elastic, india-rubber requires a distinctly increased temperature to become at all plastic, and is naturally highly elastic. S Moreover, as they are both employed for very similar purposes, they arc often classed together as though more alike in character than is the case in reality. II In fact, unlike gutta-percha (which is useil, more or less, in its raw state), india-rubber is employed as a manufactured article. 334 SL'liMAklNK TKI.KCKAI'IIS. and according; to the particular varict\- oft^um or l^uitis enii)lo)ccl, of which there are at least twenty.* Pure unviilcanised sheet india-rubber is prepared by cuttinj^ the slabs into very thin pieces, by means of a disc with cutting edges rapidly rotated. The fragments arc washed in cold water and then broken up under rollers of different kinds. It is then dried in a room maintained at lOO' V. ; after which it is masticated + to a thorough state of amalgamation, under a continuous stream of cold water. Ihe result is a large lumj) of homo- geneous dried, but jxisty, substance. This is ]nit into a straining machine with a plunger which is brought down by hj-draulic power. After being left under this pressure a block is produced, from which thin sheets are cut, subsecjuently rolled out to the retiuircd thickness. The rubber sheet is then stretched on canvas and rolled up on itself so as to exclude the air and ]jrevent the parts sticking together. Mastication, etc. — Mastication is supi)c)sed to promote the absorption of oxygen, by increasing the porosity of the substance and the amount of air imijrisoned in it. As an alternative, therefore, the slices of rubber are sometimes ex])oscd to hot, dr}-, air, to evaporate the water in the pores. They are then compres.sed into a solid block by hydraulic power, the block being afterwards cut into sheets by means of a knife working rajjidly to and fro with a slow downward motion at the same time. Physical Characteristics. — Mastication has also considerable effect on the chemical properties of rubber, depriving it of strength and tenacity to a great extent. Until the chemical and physical changes (partly due to oxidation) in the material has taken place, mastication — in throwing off moisture — tends, as a rule, to increase the electrical resistance of rubber, and to reduce its electro-static capacitj". India-rubber is a tenacious and extremely elastic substance,* grey in colour, and slightly less dense than water. Its specific gravity is about 0.92. Wlien heated to 170' or icSo F. it becomes viscous and melts at 250" F., giving off a peculiar characteristic odour: at a still higher temperature * Recently British Guiana has been looked to as a fountainhead for ruliber, and Mr Thomas Holas, F.C.S., has shewn (Colonial Exhilaition Report, 1887) thai the rubber trade here niij^ht be further developed. He also considers that there is scope for a considerable development in this direction throughout the .Straits Settlements. + Hy a machine consisting practically of a small cylinder revolving inside a small stationary cylinder. I In both these respects it differs from gutta-percha, which is scarcely at all elastic or tough. TIIK INSULATING ENNKI.OI'K. 335 it burns with a very brilliant flame. Havint; been once melted, it never regains its former state, remaining soft and sticky when cold. On this account it cannot be moulded or laid on to wire (in a tubular form) when rendered plastic by heat, in the same way as is done with gutta-percha.* On the other hand, two freshly cut surfaces of rubber will unite again if firmly pressed together. India-rubber absorbs a greater proportion of water than gutta-percha; thus, when slabs of india-rubber remain under water for three hundred days they increase in weight from lo to 25 per cent, in fresh-water, and 3 per cent, in salt-water. Gutta-percha, under similar conditions, absorbs only 1.5 per cent, in fresh, and i per cent, in salt water. India-rubber is also to a slight extent soluble in water ; as is, indeed, suggested by the stickiness at the surface acquired by slabs which have been some time under water. Absolutely pure rubber, like gutta-percha, is simply carburettctl hjxlrogen ; but the commercial kind contains resin, water, and ashes. India-rubber, when exposed to light and air, takes up ox\'gen, changing into a white resinous substance, in the .same \vay as gutta-percha; alterna- tions of wet and dry conditions accelerate this action, which goes on more rapi(ll>- in the manufactured article than in the natural substance. Electrical Application as an Insulator: History. — In 1842 Professor Jacobi, of St Petersburg, conducted a .series of experiments with india- rubber, as regards its electrical ([ualities for covering underground con- ductors ; but Mr Charles West appears to have been the most prominent in first drawing attention — in the same year — to its practical utilitj' as an insulating material adapted for submarine cables.+ In that )-ear Mr West covered a few fathoms of copper wire with india- rubber tape, and induced the " Electric " Company to submerge it from a small boat somewhere in Portsmouth Harbour. The experiment was a success, though the line did not work for long. Notwithstanding that india-rubber was introduced for the purpose — almost exclusively on short underground lines — some time previous to gutta-percha, it never came into use on anything like a practical scale till * Tlie elasticity of rubber also renders this impossible, causing it to tend to resume its previous form and thus collect in lumps, leaving more or less bare patches of conductor elsewhere. t Mr West seems to have tiiought that the insulating power of india-rubber being double that of gutta-percha, the signalling speed would be twice as great in a given conductor when covered with india-rubber and when coated with the same thickness of gutta-|iercha. This, of coinse, was incoriect, though, on tiie score of a materially lower capacity, a distinct advantage accrues to india-rubber, as is shewn elsewhere. 33^ SUliMAKINE T1:LK(;KAI'1I.S. ■ after yutta-pcrclKi liad been similarly cmploj-cd for man}- years. The first attempts — between 1848 and 1849 — by Thomas Hancock,* Silver and Co., Siemens,! and others, did not, in fact, meet with much success, owing to the physical alterations above referred to (due to chemical changes) which take place in rubber by variations of temperature, especially by heat. It was found also that when in contact with copper it was liable to undergo a species of decomposition, and to become permanently softened.^: Its hygro.scopic qualities were also found to be a serious barrier to its use — for submarine work, at any rate. Vulcanised India-ruhbek. Historical Memoranda. — Nowadays, in all india-rubber insulated cables for submarine purposes, the rubber core has passed through the process of vulcanisation ; indeed, in most instances when india-rubber is used as an insulator it is vulcanised rubber. In 1843-44, Charles Goodyear, in the United States, and Hancock, in this country, independently introduced the system known as vulcanising for ordinary india-rubber goods of commerce.§ Sulphur combines with india-rubber, in various proportions, under the influence of heat. Roughly speaking, the opcraticjn of vulcanising — or curing, to u.se the " shop " term — consists of mi.xing from 3 to 8 per cent, of sulphur with the rubber, and heating the whole for about two hours up to * This gentleman established the first India-rubber Manufactory, in (loswell Road. Later on he was joined Ijy Mr Jolin ^L■lcintosh, who had a ])atcnt for highly rectified coal tar naphtha as a harmless sohcnt of india-rubber. t Messrs -Siemens had introduced an ingenious machine for applying pure rubber by what was then an improved method. By this, two strips of rubber were placed longi- tudinally on each sid(! of the conducting wire. The whole was then drawn through semi- circular grooves, which, in firmly pressing the strips round the conductor, caused them to unite at the edges (whilst clean and hot, immediately after they had been cut), and thus form a complete cylindrical casing for the conductor. The spare rubber from each strip was at the same time trimmed off at the sides by small circular cutters, one on each side, close to the rollers. This plan was a great improvement in some respects, as it overcame the objection of unevcnness of covering due to an overlap[)ing seam. The main principle of the machine may be seen repeated in many modern india-rubber covering machines. When more than one covering was applied, the joining lines of the successive layers were placed at right angles to one another — i.e., the succeeding longitudinal layer was applied so that the seams of the two half tubes were at some distance from that of the preceding layer. \ This destructive action is checked and modified by tinning the copper conductor. S Brooman attempted to apply the saine process to gutta-percha in 1845 ; but this, for various reasons, was a failure, as shewn elsewhere. ^ I UK INSULATING KN VKLOl'i:. 337 a constantly maintained temperature of somewhere about 250 F.,* but not, as a rule, exceeding 300' F. This has the effect of causing a chemical action, and, therefore, producing a complete physical change in the rubber, of such a character that it becomes almost entirely impervious to changes of temperature, thus overcoming the difficulties previously experienced. In this condition — that in which it is said to be vulcanised — it, in fact, retains the same degree of flexibility at low temperatures, is better able to resist heat, does not oxidise in air, is more elastic, and absorbs less water; moreover, the ordinary solvents of rubber, when cold, have no effect on it, though it maj^ be dissolved in boiling oil of turpentine.+ Vulcanising can be carried out on a small scale, by iilungiiig the rubber into a bath of molten sulphur at about 250" F. If the temperature is gradually raised to 280' F., or thereabouts, a portion of the sulphur will combine with the rubber. Hooper's Core. — In 1849 Mr William Hooper, a chemist of .some dis- tinction, who had turned his attention to india-rubber, determined that when vulcani.sed it would form a suitable dielectric medium for cables.* Having a materially lower specific electro-static capacity, and an ■ appreciably higher specific resistance — especially, as a rule, when vulcanised — if it could be made a success mechanicall)', it would naturall}' be better suited than gutta-percha for dielectric purpo.ses. By vulcanising, Mr Hooper endeavoured to attain this result. The sulphur contained in vulcani.sed rubber was found, however, to have a * The temperature adopted in cuiing varies considerably with the mixture to be vulcanised and its future use. It must always, however, be above the meltinj,' point of sulphur = 2380," F. .Similarly, the length of time for which this " curing " process should be applied depends only on the amount of sulphur in the mixture. With the same proportion of sulphur, the higher the temperature the quicker the " cure " ; but there arc certain degrees of heat which are best for each rubber mixture. t \'ulcanising, in fact, restores to mixed (////-vulcanised) rubber the mechanical qualities of pure rubber, and renders them permanent. I Thus the late Mr Hooper was the first to apply the principle of vulcanising rubber for insulating purposes. This he was successful in, and every credit is due to him as the originator of vulcanised india-rubber core ; for it may certainly be said that until the intro- duction of what was then known as Hooper's core no success was met with in rubber as an insulator, owing to being unsuitable physically and mechanically, besides being seriously wanting as regards durability. Mr Hooper worked at the subject closely, and performed an extensive number of experiments with different mixtures — in which he was ably assisted by Mr T. T. P. Bruce Warren — before deciding on the constructive nature of his "separator." The methods of the present day do not substantially differ from those evolved by Mr Hooper ; for instance, the "separator" now in use is composed, similarly, of oxide of zinc. 2 A 338 SUUMAKINE TELE(ikAlMlS. deterionitinjj effect on the copper conductor, even when " tinned," injuring the conductivity besides renderinjj it brittle — which, ajrain, also acted on the vulcanised rubber. He overcame this difficulty by introducinjf a coat- ing of pure rubber next to the conductor, outside which was the "jacket" of vulcanised rubber, containing 6 per cent, of sul|)hur, and lo per cent, of lead sulphide. To prevent the sulphur in the vulcanised rubber penetrating in anything like large quantities through the pure rubber coat, he ajiplicd what he termed a separator between the layers of pure and vulcanised rubber. This "separator" was made up of rubber mi.xed with about 25 per cent, of zinc oxide, mainly chosen as being one of the jjrincipal mixtures (or pigments) used in manufactured rubber. It was found to answer the purpose well, besides acting as a fairly adhesive union between the pure and unvulcanised rubber, which could not be made to properly stick together of them.selves.* Mr Hoo|)cr adopted somewhat similar methods to Siemens, Silver, and others, for ajjplying his se|)arate coverings to the conductor. For rea.sons already stated, it was found that india-rubber could not, like gutta-percha, be applied round the wire, by means of a die, in a tubular form. It had then to be laid round the wire, either in a longitudinal strip, or else in a spiral taping with overla]j.+ Each of these methods have their particular advan- tages (as will be .shewn later), and a combination of the two was generally adopted by the succeeding layers being applied differently; a- final bind- ing of some sort being, as a rule, effected spirally to allow of greater mechanical pressure being brought to bear. The strip, of whatever form, was cut beforehand t(J the reijuired breadth, read)- for use. In 1864 Hooper's core was vcr\' favourabl)' re|)orted on by Messrs * Not only had ilifFiciilty been previously met with in adherinf,' the successive layers of pure rubber, but also in making the first layer stick to the conductor, owinj^ to the latter acting as a solvent on pure rubber and turning it viscid. .Siemens had used Chatterton's compound for both purposes but with fatal results, a chemical action being set up which entailed viscosity in the rubber. .Xn inner coating of gutta was also tried by Siemens as a protective union between the conductor and the rubber ; but here, again, besides a chemical change occurring, a union of gutta-percha with india-rubber must at all times be bad, owing to the fact of heat affecting the two differently, thus producing, amongst other things, a tendency for the wire to decentralise. Latterly heat alone was the agent— as now, to some extent. Heat, however, has often been found to fail to effect its object in a sufficiently strong and permanent manner, and great care requires to be exercised to apply the recpiired pressure whilst the material is still sutificiently warm. If, on the other hand, too much heat is present, the insulation of the core is liable to be damaged. + Adherence between the longitudinal half tubes, or the turns of the overlapping spiral, used to be effected by oil of najjhtha ; or else— more usually of late — by placing the core, on completion, in boiling water for half an hour. Till-; INSULATINd KN VELOI'K. 339 Iki^'lit aiul Clark, as well a's, in a less exhaustive ir.anner, by other eminent engineers, electricians, and chemists. Subsequently, this type of core was adopted in many miles of cable, being especially selected for tropical climates, where high temperature and the presence of submarine animal life were known to be contrary to the interests of gutta-])ercha, but found to be comparatively harmless in the case of india-rubber, so far as could be discovered, ihjopcr's core was, in fact, almost exclusively adopted — with complete success — in the China Seas when the (ireat Northern Company's ICastcrn System was being established in 1871. It, however, gave less satisfaction a few vcars after in connection with another important undertaking elsewhere.* i..itcr on it fell out (jf favour for some time. Modern Practice. — Nowadays, in the case of vulcanising for india- rubber core purposes, the ])ractice at most factories on a large scale is -somewhat as follows : — The rubber is first kne.ided whilst warm in a masticator, and sprinkled now and again with flowers of sulphur till there is thorough mixture. This may be carried out by pa.ssing the rubber and the sulphur between two steam-heated cylinders (with jagged surfaces) revolving at unequal speeds. The rubber is thus torn as it is drawn between the points of contact, and simultaneously the sul])hur is thoroughly and uniformly grcnmd into it. French chalk is, at the same time, also largely mi.xcd with india-rubber for insulating purposes, and sometimes other substances.+ This being gone through, the mi.xture of vulcanising * This lias been to some extent explained by the fact that the type of cable adopted was originally designed for deep water, whereas the line was laid in comparatively .v/z^f/ZoTi' water, and subjected to various disturbances. + For general commercial purposes many other substances — indeed, almost anything - inay be added to render the india-rublier mechanically suitable according to the use to which it is to be turned. There are, in fact, over a hundred various mixtures, including I'otter's earth, lime, jilaster of Paris, sulphide of antimony, sulphide of zinc, sulphate (and various oxides) of lead, oxide of iron, magnesia, litharge, silica, chalk. Fuller's earth, linseed oil, lamp-black, etc. etc. — all in various proportions according to circumstances. .Some of these may lie only used as pigments to give a specified colour ; others also, or solely, to assign to the material the desired mechanical consistency ; whilst others again favourably influence vulcanisation, being in some cases solely incorporated on this account. As a rule, these mixtures are only incorporated with rubber th;it is about to go through the process of vulcanisation ; but this is mainly due to the fact that unvulcanised rubber, other than jiure, has nowadays an extremely small commercial use. The mixtures vary also according to the gum (or gums) employed, in order to convert the whole into a working mass, and also with the jiurpose for which the material is to be turned. The relative proportions of these ingredients are varied according to the degree of flexibility, elasticity, and toughness desired. The manufacture of vulcanised india- rubber is, indeed, somewhat complicated ; and there is certainly plenty of scope for errors during the various stages, and especially in the mixing and curing. The details of these 340 SUHMARINK TKI.KlJKAI'llS. riihl)ci* is taken to tlu> cjilciuler for rollinjr^ machine. I'Voin there a uniform sheet is obtained which, after beiii^ cut into strips of the rc(iuireci breadth, is ready for applyinj^j to the wire. When this has been successfully effected, and the core finally surrounded by an even band of lapped calico (or cotton- felt) tape.t the completed core J is placed in tne "cure," where it is kept for the reipiired time at a temperature of somewhere about 285 ]•". Hcsidcs completely vulcanising^ the two outer coveriiifjjs, and partiall) the inside one, this pnjcess also has the effect of consolidating the whole mass. The curing vessels (or " vulcanisers ") have varied in form and shape very much of late years, at the different factories, and according to the material to be vulcanised, but the princi])le of all is the same. The)' are merely steam boxes — iron vessels, in fact — capable of being raised Uiuickly if necessary) to a certain temperature, and of maintaining it uniformly for a given time. The temperature of this ovt 1 is regulated by the pressure of .steam indicated by steam gauges. I'erfect vulcanisation can only be secured by mechanically incorporating an e.xcess of sulphur.^ The free sulphur, however, is liable to effloresce at the surface, turn acid, and cause deterioration. This is avoided by sub- stituting for flowers of sulphur i 5 to 20 per cent, of sulphide of antimony, obtained by boiling native sulphide in a .solution of caustic soda and precipitating with an excess of hydrochloric acid. The sulphide should contain 20 to 25 per cent, of free sulphur, and, if necessary, further sulphur may then be added. mixtures (as regards proportions for various purposes) on which success so much depends are naturally kept as trade secrets. In fact, the different nii.xtures and proportions are often {,'iven fancy names, the significance of which is only in the possession of those organising the work. Some idea of the composition of a vulcanised rubber core may, however, be gleaned from its specific gravity, that of sulphur and other ingredients being about double that of pure rubber, which is about half as much again as water. To deal with the manufacture of rubber completely might well occupy an entire volume. * The term "vulcanising rubber" is very usually applied to mixed rubber capable of being vulcanised. + In binding together the several layers of completed core, this outside tape acts somewhat as a metal mould. Moreover, it has usually been previously steeped in ozokerite, or in some preservative, insulating, anhydrous, and non-absorptive, composition to fill up its pores. Ozokerite compound may be regarded as a partially vulcanised india-rubber, in which the colloid pores are filled u|) with the crystalloid particles of the hydrocarbon ozokerite, which is closely allied to solid [laraflnn wax— in itself a highly insulating substance. + The curing is reserved for this stage, owing to the fact that if performed earlier the edges of the rubber coverings would not unite — being hard and possessing no "tackiness" when once vulcanised. S During this operation the coil is very usually covered up in powdered plaster, to ensure uniform heating and to prevent any turns adhering, should the rubber become sticky. Tin; INSULATING FNVELdl'K. 341 When tlic iJioportion of sulphur reaches 35 to 50 per cent., the rubber becomes remarkably plastic, and can be moulded into any shape.* The degree of " cure " adopted is a most important factor in determininj; the physical, mechanical, and insulatin[.j pro|)erties of rubber. Over-curing is as fatal as insufficient "cure."t General Retrospect. — \o two india-rubber cables are exactly alike. Cores made and tested on exactly the same lines which do not behave alike have some difference in their manufacture — possibly over-curing, possibly over-mastication, or .some error in the intermediate stages of the one or the other. The degree of success met with largely dc|)ends on the care and regularity a]jpliefl in every stage of manufacture. When any great variation occurs in the results, it is sometimes put down to alteration in the raw material. It is usually, however, due to variations in one or more of the operations of manufacture. For rea.sons already stated, a seamless tube of rubber being impracti- cable,^ the first layer (of jjure rubberj is ajiplicd either spirally or longitudi- nally — usually the former. The .separator, in any ca.se, is, as a rule, applied longitudinally ; but with the .seams of the half tubes at right angles to that of the previous covering of pure rubber, if the latter be applied longitudi- nally. The jacket is sometimes ajiplicd spiral!}' (with a \ery good overla])), and more often longitudinally ; but in any case there is, almost invariably, an (juter cotton taping about i inch in width, usually steeped beforehand in * If tlie core is iiropcily " cured " there is practically no iinvulcanised portion, as the inner coat takes up a certain proportion of the sulphur from the two outer layers. If, in addition, 3 ])er cent, of lamp-black and the same quantity of burnt magnesia is incorporated, and the mixture be vulcanised by steam at a temperature of 275 F. for periods of six, eight, or ten hours (according to the thickness of the rubber), a hard black substance called ebonite formerly vulcanite — is the result. This substance interests us only as being (like ordinary india-rubber) an especially bad electrical conductor. It is, therefore, exclusively used for mounting electrical instruments. t Indeed, in "curing" it is usually thought safer to err on the under-side than to over- step the mark. In the latter case it is difficult to tell, except by the action of time, whether the material is over-cured or not ; whereas the substance being under-cured is brought to light at once. + This statement more particularly applies to high-class rubbers. Owing to their stiffness and to the tearing action of a die, the material gets "killed" in the operation. The advantages of the tubular form have already been made evident, but the vulcanising of the present day so perfectly unites the seams that they are practically non-existent. Owing to their greater plasticity — sometimes approaching that of gutta — low grade (cheap) rubber mixtures can be spewed on a wire through a die, as in the case of gutta- percha. 342 SUliMAKINE TELEGRAPHS. ozokerite or other compound, and applied spirally under pressure,* with a good overlap (and in an opposite direction to the jirevious co\ering, if spiral), in order to thoroughly bind the whole together whilst in the proper condition.+ There being a greater art in the successful application of india-rubber to a wire than in the case of gutta-percha, the manner in which this is carried out, in its successive la\-ers, is usually kept, to some, extent, a secret by those who have made a specialty of the subject. This is more particular!}' the case owing to the fact that many of the Uiachines used for the various o[jerations do not form the subject of a patent Be this as it may, much valuable information regarding the practical details of rubber manufacture^ may be gleaned by a perusal of Mr Stuart Russell's work (Jti " I^Zlectric Light Cables," to which the reader is referred for further particulars of this description, if required. § Physical Qualities. — India-rubber is a most curious material to deal with in many ways. It alters in its physical properties so enormously under different conditions, that any description of it will only apply to that particular state of affairs. When vulcanised, its ])hysical properties are almost exactly the reverse of what they are when un vulcanised. In the original raw state it is elastic ; in the manufactured (" mixed ") state it is inelastic ; but when "cured " — />., baked — it becomes ela.stic again — indeed, more so than ever. Thus, in speaking of india-rubber, it is verj- necessary to specify with some precision the e.xact form, or stage of manufacture, it is in. Moreover, it is, in any case, impossible to speak of india-rubber collectively (with regard to its properties) owing to there being — as already shewn — over one * As long ago as 1852, Mr H. V. I'hysick had a patented machine (specification No. 77S of that year) for applying "calico cloth or otlier fibrous material" to a wire in tape form. This was by way of insulation, the tape l)eing " previously saturated with gutta- percha, shellac, tar, jiitch, or other insulating substance."' Tlie macliine was very ingenious, and actually applied the tape by a peculiar form of die. t The various points regarding longitudinal and spiral applications of rubber are, roughly, as follows : — In the longitudinal half tubes the actual breaking strain of the core comes in more ; on the other hand, the continuous seam is of the weakest possible kind — being, in fact, a "butt" joint. In the s])iral tape the continuous joint thereby involved is much longer ; it is, howe\er, of a stronger character, being of the overlap form. More- over, more material is required here. Hy the combination of the two methods alternately in each successive layer, the strongest and most reliable insulating envelope is obtained. J It should be mentioned in passing that when once vulcanised, this material practi- cally never gets softened by heat; thus it is unnecessary to draw a core so co\ered throu^jh cold water (ns is invariably done with gutta-percha) for cooling and hardening purpost ". !5 " Electric Light Cables and the Distribution of Electricity," by .S. A. Kussell, A M.Inst.C.E. (Whittaker and Co., London). THE INSULATING KNVEI.fM'l-:. 343 hundred different mixtures of it, with totally different ingredients and pro- portions, each mixture having its special peculiarity for the particular purpose for which the substance is intended. Vulcanised rubber being so highlj- elastic, it cannot be successfully " worked " in thi:-: state. Thus when cured, le.ss than ever can it be put into any shape by pressure whilst hot and plastic. If attempted, it only draws u|) and returns to its original form after a certain time. It is for this reason, then, that though the admixture of sulphur is effected immediately after purification, along with other "mixings," ])ractically all the curing process — a given degree of heat for a specified time — is reserved till after the material has been made up into the form it is required. Thus, in the case in point, the rubber is not actually vulcanised to any extent till after it has all been applied to the wire in its various coverings ; the coil so made up is then placed in the curing chamber. Several means have been suggested from time to time for testing the degree of vulcanisation in rubber. Most of these are in the nature of applying additional heat — i.e., a sort of .semi-cure — such as renders the rubber harder and less elastic. If there is an excess of sulphur in the specimen — (jr if it has been overheated in coating — the material at once shews signs of brittlencss. Insufficient curing also easily shews itself. Unfortunately there is no mechanical test for rubber that cannot be evaded in some direction or other. The reputation of an experienced contractor — together with electrical tests which are in any case essential — are best relied on for ensuring a good quality rubber, and one that is really durable, which is the main thing to be sought after here. It .seems to be imagined by some that the purer the rubber the better for till purposes — partly, ])erhaps, because it is dearer ; inasmuch as pure rubber, when cleaned, costs about 4s. a pound, whereas .some of the ingredients in mixed rubber cost about as many |)ence. However, where durability under un- favourable conditions is a consideration, well-made " compound " — i.e., " vulcanising "^ — rubber will, as a rule, be found superior. Physical, Mechanical, and Electrical Data. — Owing io the enormous variation in the nature of \ulcaniscd india-rubber, as manufactured by various mixings and methods of treatment, it would be absurd to attemjjt to give any definite physical, mechanical, or electrical data, in the way of actual constants and specific values, with reference to vulcanised rubber generally. It can only be stated, that its electro-static capacity is generally taken as atjout 2..S to 4.2 for ordinary gutta-percha* — where air = i ; and * And Willoughby Smith's jjutta-percha 3.1. 344 SIMiMAKINK IIJ.I'CKAI'IIS. tlial its iiiMilatimi ri">istaiiri! is usually at tlic very least douljK; thai n( t^utta-pcrclia,* hut fjftcii maii\' times nH)re.+ It is usuall}' admitted tiiat, i( aiiytliiii(.;, pressun; tends to a< tiially decrease the iiisniation rcsistame of \ iMcaiiised iniiiarubbcr, thoii^^h the cffcci is, in any cast;, i:xcL'cdiM^;iy small. ;J I'lu- differcmee in this respect, as C(jmparc;d with |_nitta-pcrclia, is probably ouinj^ to its (greater absorptixt- power 'even wlieii vuh aniserl;, due to the fact of bein;( necessarily applied in such a way as to involve a < onlinuous seam, instead of in l)omo;;eneous tubular form.§ Teiriperature influences the resistance of all (lasses of rubber and rubber im'xtiues cttiormousl)' less than ^'utta-percha.* A^ain, vulcanised india-rubber is much less influeiKcd by a;.;e than ^futta-|)er<:iia. If, however, it is left uiivulcanised, rubber undergoes much the same molecular settiii;^' b)' aj^e as in the case of KUlta-percha, the rc-suIt bein^r a very similar increase in electrical resistance. On the other Iiand, with unvulcanised rubber this only ^oes on up to a certain point, after which it becomes "treacly ' — by decom|>osition due to oxidation. When once "cured," rubber is no lonj^er open to an)' material physical chan^^es, and, therefore;, its electrical resistance also rc-mains fairl)' constant irrespective of time. Yet, elei trification takes pla( (; \ci\' nni( h more rapidly with india- * I'liis is a niiioiis <:ir( iiiiislani e f)ti llic fate ol it. liciii^; a inon' or N's-, pure, iin- adultcratrd, anil lioiii'i^ciU'oiis ^iiiii, it iiii^lu naunally lie tluiii^jit lliat ^iiUa uoiilil li.ivi- iIk; lii^jlicr (:l<;< irii ;il rcsistatid'. It appears, liowivci , t(i Ix; almost ilii|)ossil)l(: to i oinpai'- these materials owinj; to the i^nriraini' still prevailing n^jaKlin;; the aljsojiili' physii ,il conditions of (yicii. t Notwilhstandint.! the r omparativi.-iy low specifii values lA most o( the mixing; ingredients, the insulation resistan'c of many (Lasses of vulcanised ruhljnr is often I onsideraliiy Krcalcr than that of pure ruliher ; l)iu this a^ain varies tremendously wiiii the nature of tiu; mi.sture and (lire. This can only he aidiimled (or liy the iliemiiMJ .md physical i hanK(;s eff(r( ted ljy the niixin),' and (urinj,'. { When ( ompared with mitta-percha, th(r ahovc seems stran>^c at first si^ht, as it mi^ht he supposed that the least lioiudneneoiis I'most porous and al)-.orpti\c. material would offer tla greatest s( ope for improvement in this r(;spe( t imder pressure. (" 'ihe I'hysir.il and Kleilrical Kl'fiicts of I'ressine; and Tempirriiliu'e on a Subuiarine (aide ('ore,'' hy (.,'hatles ItriKht, VAi.S.V.., /cur/iii/ Inat. I\.l\., vol. xvii.; .*$ Still, in so far as pressure and low temperature lend to make sik h ,i material mor(.- lii'iiu', lite ele( lri( al resislani e of india ruhlier lends lo he iru reased on this ( oiuit Ihouj^h not lo tiie sain(- dcj^ree as ^;utl;l pen ha. I The proportion is, roughly speakin;^, ahoul I to 4 ; hut if iIk; riihljcr he unvul- canised there is nothin]^' like ihis difference. In fart, pure ruhher is usually even more afTertcd physically hy lemperatiire than Ki>ll:>-|>cr( ha. Ileiue, il has heen found lliat when siihmerj^ed, tli(; absorjition of a (crtain (lass of rulilxM' was ei^^lit limes ^jreater at 120 I'', than at V; I'-i whereas with ^y\\\n pen ha it was only douhled. " For si-ver.d reasons the opposite niixin reasonably b(! e.^peded. All that (an, however, be said is, that having a distinctly different lextural character, they are affected quite dilTcrently ; and this explanation must be taken as e(|ually applyiuK lo tlie elfei I of pressure. nil. iNsci.ATiNt; I';n\ 1,1,'ii'K. 345 iuIjIh:!' 'whether xiihaiiised or not; tlian with [Mitta-pcMc h;i. 'I'his a^'aiii varies enormously with the mixture; l)iit so (.jrcat is it that it is not unnsnal for the a])|)ar(.'nt resistance aller Ihree minutes' battery ajiphiation to he floiil)le tiiat alter one iniinit(r. With ^^iitta-|)c;ri;lia thi: electrification only canseil a risi; in tlu: apparent resistance of about 25 |)er cent, during the first five minutes: for rubber it may well be over 100 jH-r cent.* I he fornmia- for obtainini^ all tin; abosc mentioned data aie n.ilurally the same as with jjutta pcrcha, differiii}.; only as rej;ards the constants and c(jcfficients.+ hl.ri.klOKA HON III' JMdAKIMlMI.I;. On accoiml of its valuable: electrical (|ualities, and Iroiri the fact lh.it it is not supposed to be prejudicially attacked by marine or^^■misms, india-rubber woulfl seem to be (|uile the ideal form of dielci trie for sidimariru: (.ables, especially as, when vulcanised, it stands heat and ex|)osure to air and lij^ht. I iifortunately, howev<:r, it is subject to more or less serious deteriora- tion, the exact nature of which is only very partially uiidersto(jd ;* cables so insulated, supposed to be similar in every respect, ^ivin;^' sometimes alto- gether different results. Thus, aiinouicd toi|).-do i able, containini.; seven separate ( ondm tf)rs insulated wilh india rubber \ iih .inised throii'diout, have been found to seriously deterioratr: ;dter eijditeen mo'iths' iimnersioii, At * I'liiis llic ;i|)|);irrnl rc',ist.in< <■ :iIict liircc iriiiiiiH-,' li.itui)' :i|)|)li( miIdh is, rou^^lily s|)i;il,', Hvi( (• l|j;il iifu-r (i;if iiiiiiiiK' ; ;iii(l .(ri'-r tnr iiiiiiilti-s it is llMcclold ulial il woiiM lie adcr one iniiiiilc r)nly. • I'liDU^ii lli(s<> I ;ui lie ;;ivrii willi sniiic sense of .i' ( iir.u y in relatiun to ;;iina ))ir< li:i, tiic MiixUires of india riihlier and ils mctliods of nwiniifai lure at dilfciriit f,i( lorn- . bcin); so varied, il ttoidd Ix: nscjcs-. lo alteMi|>l il with llii! I.iltii. Tlic Ixsl pjai <■ for cihtainin^; lliis inloinialion ai < iu;it('ly at tin- lime, foi |iiar tii al |iiir|)oses, is al 1 n li iii(h\ idiial f.ii tor y for each material. J Mr IJrucc Waircn lindin>; lli.it liroiiiiiie, iodine, and < liloriiie, inslc.id of oxidising ilKJiariiljIicr in ( oiitai t willi water, prodni c an alto|;etlicr difliictil effec 1 oni e ciidea- MiiiK'd lo turn lliis to .Kioiint in tlie iii.innf.K Hire of (able (ore. liy lii«s priKCss, tlic (oiidiKtor was ' overed willi two ( oaliii^^s of india riiliher, wlii( li wcri! first welded together in hoiliii).; water, and afterwards iiliinjjed into a solution of iodiiii: in iodide of ijolassiiini, or of lironiinc in hroinidc of pulassium, or else exposed to the aetion of chloral. India-riihlier treated in this inanner is said lo withstand a ( onsiderahle aiiioiint of heat witlioiil detci ioraliiiK. It also resists the a(tion of air, ,iiid tli;it of its ordinary soKcnIs, altlioii^di no traie of iodine, liroinine, or free ( liloral (an he (lrte( ted hy < lieiin( al analysis. (,'ontaiiiiiiK no suljihiir, it do(;s not attai k the (ojiper, wlii( li, therefore, docs not re(|iiirc to l)e tinned. It is said to retain a piTinaneni e|(m^;ation like copper when suhjectecl to tension, so lliat the ( ondiK lor should keep ( cntral when the strain on the ( ore is rirle.ised. It is staled that the ehv tri( ,il (pialities of the india-nihher ;ire improved liy tlic .ihovc tri:alnient. It is a pnxess, however, wliii h, in (diniiioii with other spe( ies of unviilcanised riihher mixtures, wouUi nei eiiSiirily he open to some measure of dctcrioratiun hy time, and has never hcen adopted in a( liial pia( ii( <•. 346 sun.MAKiNi-: tklkgkai'iis. the faulty parts, the dicicctric had become sufficiently porous to permit of the water passing throuf^h to the conductor, with the result that some of the cores had much lower insulation than others in the same cable. It would seem, then, that vulcanised india-rubber, as we now have it, cannot always be absolutely relied upon to provide any specific and un- varj'in;^' insulation resistance, notwithstanding the iiriprovemcnts which experience have ^iven us. Vulcanised india-rubber cable, .some protected with canvas for army field service and others with iron-wire sheathini; intended for submarine- mine purposes, have been stored up, exposed to the air, for ten years or more without sufferinj^ in the least, though other similar cables stored in the same building — .some under water and .some in air — have behaved very differentl}'. In one instance, a length of a (cw inches at the ends of the cables stored under water was left dry to meet the required conditions for testinj^, and here the inside coating had become vi.scid and oozed out at the ends. This deterioration ceased abruptly at the point where the cable entered the water, shewing that, in this case, the deterioration could not be due to the contact between the rubber and the copijer. The same vi.scous exudation was noticed at the ends of the armoured cables which were kept exposed to the air, but here the mischief was found to extend over a much greater length. This deterioration was, no doubt, the result of serious o.xidation, due either to too much heat or to sunlight — producing, in fact, precisely the same effect as over-vulcanising in manufacture. The direct rays of the sun have a distinct influence in this way.* The gradual transformation which sometimes turns the inside covering of rubber into a semi-fluid, viscous, substance docs not ajjpear to have the effect of actually lowering the insulation of the cable — especially where next the conductor it remains quite pure. In course of time, however, it un- doubtedly has a solvent action on the outer coatings of vulcani.sed rubber, and must always be highly injurious eventually to the general mechanical constitution of the cable. It ma\- be stated generall)- that the deterioration of rubber is, as a rule, due to bad manufacture, or bad inatcrials — usually the former, and .some- times bt)th.t Cables made and tested on exactl)' the same lines which do * Indeed, in .America tlie sun's rays arc actually turned to account in a certain method of vulcanisinjj;, for what are called sun-cured goods — or fabrics spread witli luhber and sulphur subjected to the direct rays of the sun. This evidently is the effect of a combination of lic.it and light whicli produces the same result as tlie action of heat alone at a higher temperature. t Owing to tile fact that rubber is a manufactured article, whereas gutta-percha is used almost in its raw state, there obviously exists a much greater scope for errors of manufacture in a core of rubber than in that of gutta. THE IXSUI.ATINO EN VKI.OrK. 347 not behave alike have some difference in their manufactiM'e, probably over- curing, possibly over-mastication, or some error in the intermediate stages. Since the original ap|)lication of the principle of \iilcanisiiig to rubber as an insulator, the manufacture of vulcanised india-rubber core has been made a subject of close and careful study at the hands of the Silvertown Company and Messrs W. T. Henley and Co., as well as of Messrs Siemens brothers and Messrs Johnson and I'hillips, besides Messrs Hooper, the originators.* Ilie result is that it is now, by experience, recognised as the most reliable — though initially, most costly — insulating material for electric lighting requirements, as well as for other underground conductors, cspeciall}- where a comparatively high electric pressure is employed, and also generally where rough handling, frecjuent changes, and frec]ucnt storage may be looked for, as in the instance of torpedo cables.t Vulcanised india-rubber has also been turned to good account as the dielectric for .several more or less deep-sea telegraph cables, more especially in tropical waters and where the teredo and other enemies are known to abound. * Latterly, also, the Telej^rraph Construction and Maintenance Company have enlarged their sphere of operations by manufacturing consideral)le lengths of india-rubber insulated cables for electric light and otlier purposes. t C.utta-percha is, however, also employed as the dielectric for submarine-mine (" torpedo") cables. In either case, felt bands, or even tarred linen bands, are usually lapped outside the cores of torpedo cables as a preservative, and to give the core greater strength for pulling al)out. In this case of shallow water, the objections to the tar so close to gutta-perc ha even do not seem to seriously apply in practice, or are overcome by the advantages gained in the preservative tape. Eastern iiml .Scmdi African Tck'grai>h Company : Mombasa Station. 348 SUUMAKIXK TELEGKAI'llS. Sf.CTION S. — RkI.ATIVE MKRITS of GUTTA-rKRCIlA AM) iNDIA-klllliKK.* Advantages of India-rubber.— As ijrcviously stated, at first sit^ht india- rubber would appear to be the best adapted material possible for insulatintj; purposes — especially when \ ulcanised — c\en for siibuiarine lines. Tiiis is on account of havini; a materially lower electro-static cajjacity tiian pcrclia in an\' form, and usually more than double the insulation resistance. Thus on the first count a materially ijreater sit^nalling speed would be the result on a lont^ length of continuous cable, where every little increase in tile electrical constants bej'ond a certain point makes a sericnis differcnce.+ Secondly, vulcanised india-rubber is, as a rule, when in good condition, infinitely tougher than gutta-percha. Thus it stands rough treatment much better. Thirdly, india-ruV)bcr, wIkmi vulcanised, undergoes heat better than gutta- percha, mechanicall}- and electrically. The highest tem])eraturc which gutta-percha will stand before softening is about 115 I*". ; whereas no mixture of vulcaiii.sed india-rubber softens till about the boiling point of water is reached.* Thus, if the cable be anywhere ex]3osed to the sun, the conductor is much less likely to fall eccentric, or the mechanical and electrical qualities of the dielectric to be otherui.se detrimentally affected b}' an increase of temperature with a VLilcaniscd india-rubber covering than in one composed of gutta-percha.^ h"ourtlil\-, india-rubber, when vulcanised, is almost unaffected by the atmosphere, besides being but little influenced by dr\' heat, (nitta-pcrcha and nearl}" all resinous substances arc composed in part of \-olatile ingre- dients, and after being e.vjjoscd for a time to the atmos]>here or the rays of the sun, these volatile substances e\ai)orate, the compound beccjmes hard and brittle, and in consc(|ucnce liable to crack. The cracks thus * India-niljbcr and gutta-percha being both liyilrocarlions, appear chemically similar, inasmuch as it is very hard to learn much about a hydrocarbon. In reality, however, tliey arc perhaps as unlike in physical properties as is conceivable, for any two such materials, though both suitable insulating mediums. + In the case of the proposed Pacific cable, for instance, an india-rubber dielectric would — on i/('(V;7Vv?/ grounds at any rate — beat a distinct advantage, with gvcn dimensions. I "Insulation Resistance," by Charles Bright, A. M. Inst. C.K., /('//;//<«/ Inst. K.E., vol. xviii., p. 123. Ji Cables in shallow water often experience temperatures as high as 85° F. - or even nearer to 90 F. towards the beach — which, after a time, is iiKjre liable to affect a gutta- |)ercha core prejudicially than one of india-rubber in the ordinary coiuse of affairs. rilK INSIJLATINC KN\Kr.( )1'E. 349 formed .idmit ;uul retain moisture, whicli h;i.s tlie effect of yrcatly impairinj^ tiie insulation of the conductor, and finally of destroying it altogether. When pure, india-rubber is no better than gutta-percha, if exjjoscd to light and air, as regards durabilit)- ; neither is it under alternating dr\- and wet conditions.* Wlien \ulcruiised, however, it is infinite!)- superior, especially on the first count ; indeed, light and air are not supposed to materially affect certain forms of vulcanised india-rubber.+ Advantages of Gutta-percha.— On the other hand, high-class india- rubber cannot, owing to its great elasticity, be a|)plietl in a permanent manner round a wire in tubular form by means of a die ajoparatus, as is done with gutta-percha * Heing laid on in previously prepared longitudinal and spiral strips, a continuous seam occiu-s, which, though overlapped, must always tend to be a .source of weakness, mechanically and electrically, as compared with the complete tube.i^ Again, electrically, the insulation resistance of vulcanised india-rubber, when submerged, has been known to become reduced by time, pointing to a possible deterioration rather than improvement, as in the case of gutta- percha under the same conditions. This may be due to the .somewhat extensive absorption of water by india-rubber of all forms; verj- likely partly owing to the continuous seam already alluded to. * As regards <;iitt:i-perclia, mechanical and electrical deterioration under these conditions is brouj^lu about by the evaporation of the natural oil under extreme drj'ness, causing cracks which are subsequently filled up by water under the opposite succeeding intluencc. When new, india-rubber may also be said to be slightly volatile, though scarcely constituted by an oil in the general sense. t These hist three features apply where a cable is liable to experience much handling and changes of position, as in the instance of subniarine-mine connections, sometimes at the bottom of the sea, sometimes stored ashore. I Inferior mixtures of rubber, being more or less plastic, may be squirted on to a wire tubularly. Owing, however, to the tearing action of the die, this is a doubtful advantage with any class of this substance. S It may be remarked, however, that this disadvantage in rubber core has, of late years, been reduced down to rather a fine point by improved methods of i.i.iniifactiue, the seam being eventually so perfect as to be practically impercei)tible w hen perfo nied by certain machines. With definite materials and by a definite method of procedure the mixing and vulcanising renders the seam non-existent in reality. ] Henley's ozokeritted india-rubber core was intended to meet this objection, the pores of the india-rubljer being filled up with o/okerite wax, which is, moreover, an excellent insulating medium itself The ozokerite may also be applied to tape as an outside covering to the core for the same purpose. This is very usually done, and with good effect. 3SO SUHMARINK TKLKCRAI'IIS. The ]3r()ccs.s of joint inakiii^i; in vulcanisctl india-rubber must ah\ay.s be a more elaborate and troublesome affair than that in Ljutta-i)ercha, besides tiic risk of defect beiuL^ iiere correspondingly greater, w liere the ])rccisetime for vulcanising is so important a consideration. On account of the higher specific resistance, faults of insulation in india- rubber should be easier to detect than in the case of gutta-percha. Owing, however, to the high degree of elasticity of the former material, an\- weak place is liable to be at times concealed — .sealed up, in fact. Thus inter- mittent effects are produced, such as ver\' often render anj'thing like accurate localisation an e.xtrcinely difficult, if not impossible matter, in comparison with gutta-percha under the same conditions. In the event of gutta-percha becoming seriously scarce — as it has sometimes threatened to — it is at any rate satisfactory to know that there is a fair substitute in india-rubber, which, with further experience and improvements in maiuifactiu'e, may still more closely realise the reciuirc- ments even for subm"'-ine purpo.ses. For /rt//^/ purposes it is all that could be desired, as has alread\- been shewn. It is, moreover, well suited for exposed places — on the beach and elsewhere. Kiistcrn ami Smith African Telegraph Company ; Cable lliit, .Maurilius. TIIL INSULATING KN VKI.OI'K. 35 I Spxtion 9. — Othkk SUGC.ESTKr) Ixsulatinc, Materials. It may be fairly said tliat as regards the initial expenses attached t(i a submarine cable, the j^rcatest apparent scope for ini|)r()vement lies in the composition of the dielectric, owinij to the heavy cost of ,i;utta-percha (or india-rubber) as an insulatin^f medium. Various Inventions. — h'rom time to time, subsequent to the emploj-- ment of gutta-percha and india-rubber for this purpo.se, various inventors have been .said to have discovered marvellously cheap substitutes for the above ; but it is worthy of note that nothing is ever heard t)f these being adopted in practice, though it certainly does not follow from this that they are not po.sses.sed of great merit. However, on close inspection, they are not, as a rule, found to have quite the same qualities that experiment voluntarily suggested, or was made to suggest. On the other hand, where these "inventions" are found to be entirel)- satisfactorx', it invariabh' turns out that they are in reality a form of rubber or gutta-percha — gutta-percha or india-rubber forming, in fact, the principal base — under a different, and more elaborate, name; or, at any rate, that this satisfactory result is brought about by the introduction of a more or less large proportion of rubber (or gutta) into their composition. Advantages Claimed over India-rubber and Gutta-percha. — Some of these ccjmpounds have been said to be most capable of resisting oxidation, attacks of insects, and other objections ; besides being less affected by changes of temperature. Many of them certainly appeared — at first blu.sh — to pos.sess valuable electrical qualities, but with none as )et have we found anj'thing like the mechanical indestructibility and electrical fixedness of gutta-])crcha when kept under water, or the toughness and reliabilit)- of india-rubber on land when exposed to the sun. l"p to date, indeed, nothing has been found which is likely to replace gutta-percha or india-rubber in their application to submarine telegraphy, as a dielectric material, for many )-ears to come. Particulars of Alternative Materials. — We will, however, briefi\- make reference to some of the princi])al substances which it has been proposed lo substitute for these from time to time : — i'aper,* wool, cotton, silk, hair, canvas, flax, jute, hem]) — in yarns or * Comparatively recently Messrs Fclten and (luillcaimie have sugjjcsted the use of flat strips of prepared paper applied round a cross-shaped conductor with air spaces between, the wliolc cable being protected outside by a waterproof casing— lead tubing, or otlicr 352 SL'HMARINK ■li;i,i:( iKATI IS. strips or br;ii(liiv^\ as the case iiia_\' l)c -all tonned the sul)jects of early patents in \arioiis \\a\s for iiisulatinLj pur|)()scs, and were even su;^j.jcstcd as a siiitaijle means of insnlatiim for siibiiKviiic cables. It should be men- tioned, however, in passing, that, in most instances, it was proposed to l)rcvioiisly saturate the abo\e with some preservative composition of a resininis nature that would tend to render die material anhydrous, and consequently non-absorptive. Bitumen, o; pitch — a residual pnxkict of coal tar — was the usual liquid material suggested for steeping any of the above fibrous materials in, or else some variety of the same. Vegetable and coal tar and their oils were also prominently put forward as a jirescrvative anhydrous mi.xturc, possessing a fair insulation resistance; as well as lin.seed oil, paraffin* and paraffin oil, ct lioc ge)itis oninc, all jios.sessing a very high degree of insulation when fresh. Besides the plan of jircviously saturating the material with any of the above compositions, there was also that of pouring it into a metallic tube of some sort (usually lead) into which the conductor, lightly surrounded with the fibrous material, had been previously drawn. Then there were the suggestions of forcing, or steeping, bee's-wa.x, paraffin, or other wa.x, rosin, shellac, and bitumen, as insulating substances, in a fluid or semi-fluid state, into the pores of wood or any of the previously mentioned fibrous materials. White lead, o/.cjkerite (/.<'., jjaraffin in a natural state), spermaceti, tallow, cold cream, and butter, have all been made mention of in the same way, to render the fibrous material durable and anhydrous, as well as assigning extra insulation to the whole substance. On the other hand, however, one or two inventors ajjpear to have protectinjj material of some description. This form of cable they suggested, on the grounds of low capacity combined with lightness and cheap insulation, more especially for long-distance submarine telephony. The joints might, however, present some difficulty, l)oth as regards efficient carrying out and the attainment of non-absorption and subsequent water-tightness. Again, the dielectric in the famous concentric cable of Mr S. Z. Ue Ferranti is com- posed of prepared paper. This cable is said to be doing useful work as a high-pressure main for electric hghting. * I'arafifin, a product of the distillation of certain kinds of coal and bitumen, is an excellent insulator and an admirable excluder of moisture ; but being of a brittle nature, it is generally acknowledged nowadays that it cannot be directly made use of in cable manufacture, even for land pur|)nses. It, however, serves to protect the bare ends of the leads used for testing purposes, and keeps them from contact with the air. To do this, the ends of the wires are dipped in paraffin previously melted in a small vessel ; on this being repeated five or six times, the ends receive a white coating of solid ])araffin, which prevents any loss of electricity along the surface. THE INSULATINC KNVEI.OI'E. 353 abandoned the idea that tlie insulator, even for a submarine cable, need necessarily be waterproof, f^oinj^ in only for what they jjrincipally cherished, as being strong, fibrous, plialjle, and durable materials, with a certain insu- lating power of their own, such as horse-hair, for instance!* In lleardcr's patent of laniil. It, in fa*!, refers (;()ually to all llir differcTit oi.casioir. on uliich joints n:'|tiir<: to hi- made i)(:tw(-irn Icnpjths of the iiisulatcl <.oii(!ii(;tor, i.e. '\j the various iinsht;alhe(l (oils ; '2) tlio sh(;alhefl se<;tions at factory ; (i,j the same ahoanl shi|) in preparation for layin}.j ; (4) during repairin^( operations. The term " splicing;" is sf>metimes applied to all tlie ojjc^ration, rieies- sary for coiilinnity helu'icn two cables ; the cfftuiiK tors, insulating envelope, hempen cov(;rin^, and sheathing; wires bein^^ (tadi sloyin}^ such instru menlH and methods as would ^^ive a satisfactory < hie re^ardinj.; the state of affairs. Sometimes, incieed, such tests are altr^jether delusive. When two sections of cable already laid arc s|)liced to^'cther 011 boarrl, and the bi((ht so formcfl (juickly h-t \.[f>, it is almost impossible to obtain even the roughest indicaticm as t(j the condition r;f the joint. I'here is * Sometimes invdlvinx several months' intfrnipiiDii 10 trafifir, hesideit a direi t osl of tfiousands of pounds ! tliii, ii'i avail;il)l(: ificaiis of vcrifyiiit; tli<- w'»rlite <>( every precaution to r.'iisure cleanh'ri(!ss. .\ jointer at work ,hould alway . have an assistant, so that he may not have to touch anythiti^; uncoiuiei ted with In" s work, after the joint has once been tarted, 'I ';')I,S. The necessary tools lor makiii;^ an ordinary jMitla |;ercha joint in elude*- - I re , tie hencll. i'lumber's stove, or fii-e|)ot. Spirit lamp, Solderin;^ in^n. 'I"ooliM}.j, or polishing;, irons f(jr workin;.; and kneading the jMitta-per( ha. I''lat jiliers 'if different sizes. Knives, ra^;s, emery pajx-r, resin or stearine, etc. The Ixii' h M'i;;. yj) is furnished uilh a pair of small vices, or < lam|js, placed in a line facin;; one anothirr. One of tlu! vicirs is adjustable alon^ a !,;roove cut in the bench, to which it can be secured at any point by a nut underneath. These: clamps are for firmly holding each condui:tor end to^^jether durinfj tlw; process f»f jointin(,;. The; spirit lamp serves to warm the polishin;;, or tooliu};, irons, and t( the (lame. I'll.. )l. S|iiril l.aiii{< t\w\ WmA. There are also a ninnber of smaller holes pierced all round the hood, tlius ensuring; a sufficient drau^'ht of air lhrou(.(h Ihein and out at the top, with the result that the (lame a< Is sonu'what as a for^;*! (lame. * Naphtha is montcitpec iaily usc|)iii lioncl ii(/ii (or c:i»iiviMiii-iit use sliDiil'l li;i\c the (' illowiiit' 'liiii'-ii'.ioiis : — l.i'ii^;lli of iron llicidlli :il tin- riid I'll''. Illi near llii- liancllr Tllii Kll(:^•l al till- liiul'lli' (i III' Ill's. i - in 11 rill- iioii Mill I Mill)' \)i- licilcd over ;i spirit l;iiii|) 'ol lin- ilc .< lipti'/ii ^ivcii; in a iilmiiixi's stove as (|cs( riix'd, and its use is (oiilincd I'l jjicad ^ .1^ I'li;. \2. Toolinn Itcii. inp, out tile ( liattciton (oiii|)oniid, hr^idcs |)()lisliinj; and (illiiif; up the si-anis in tlu; (.Mitia pen ha. I lie |)iopci- trinpcratinc to wiiiiji the iri/ii should he ln-atrd is ri;co(.(nist;d by a (.((riitic Wiiriiitl) perceived on lioMinj; tin- iron an iiK h or two away from tin- ( licck when also the end of tin- iron has a' ijiiiri'd a |iali- blue col'iiir. i he ;MiUa p(ii:lia is cut with vshal is (oii,iiionly l.nown as a " triiniiiiiii; kiiifr," the l)ladi;s of wliii h iiiiist he \rvy sharp. Just hcfori- usini;, the tonj;U(; is passed aloii;; 1 he Made to pievcnl tlie ^Milta peri lia adherin;; to the iiielal. The \saste cdj;!', of ^jiitla-perclia sheet used for tin- joint are I lit off" with a pair of JK-rit scissors, pre\ iously tnoistened in a siiriiiar manner. 3<5o SUHMARINK TKLKCkAl'IIS. SfXTION 2. — JOINTINd Tlir; CONHUCTOK. The ^utta-pcrch;i iiisulation (jf the tucj |)icccs of core to be joiiiti'fl is cut away (I''ijJ[. 33), so as to bare the copper conductor for aloout i\ to 2 inches from either cud. Care has to be taken thai the copper wires are not at anytime nicked b}' the knife — even in the smallest de^^ree * Should accidental injury thus occur, there should be no hesitation in snip- |)in^f off the Icnt^th of core alread)- bared, and starting again on a fresh piece. The several wires of the copper strand are now unlaid, and each pulled out straight at their various angles, care being taken to give them no twist. Each one is then separately cleaned either with fine emery i)aper or with the back of a knife-blade, more especially in order to get rid of all the Chatterton's compound with which each lias become more or less covered. The jointer should wash his hands carefully, and after wiping, ])lunge them into na|)htha, which is allowed to evaporate so as to leave the finger.s ^"•• ii' — Conductor IjkIs I'rciiared for Jointing. perfectly dry. The bared co|>])cr wires are al.so sometimes wiped with naphtha, so as to completely clear them of any grease or other foreign mattcr.+ The copper wires are now twisted together again into a true strand as before for about a third of their length, using a pair of small flat-nosed pliers, care being taken to twist them in their original direction, and ])reserve the proper length of lay. This first |)art of the operation is common to all the methods of copper jointing. The two ends can be jointed together in any of the fcjllowing ■* .\fter a little soflcnin},' by heat and picssiiij^ round with the pliers to tlie requirid distance, the length of ^;uua-perc:ha may often be neatly liniwn off\.\iit conductoi with the pliers, thus obviatin;,' the necessity of cutting with a knife. \ This is not, however, allowed as a rule, owing to the insulating properties of naphtha, wnich might thus prevent proper conduction between the various wires composing the strand. The cleaning of the wires is, in fact, usually alone carried out by emery paper, or bv the baci^ of a knife-blade as above. JOINTING. 361 ways, all of whicli ^nvc j^ood results, so far as reliable contiiuiit)- is concerned : — ■ 1st. The seven wires* of each conductor are divided into two sets fl''it^. 34;, one containin;^ four and the other three wires. The close por- tions f)f the two c(jnductors are then brouj4ht to^^^ther end to end, and the four sets of wires intercrossed. Kach .set of wires is then sejKirately wounrl round the o|)()osite conductor, coverin;^^ the lay of its corresponding .set, but Fk;. 34. — A l''orm of Coii'liicinr Joint. without crossing each other. The ends are trimmed off with cutting jjliers. The wires are wound in ])lace, using small flat pincers held in one hand, whilst the centre of the joint is firmly held in the other hand with a larger pair of pincers. 2ik1. The two ends of core to be joined being prepared in the usual manner already described, the central, or heart, wire of either end is cut, and the remaining wires o|)enefl out, as in l'"ig. 35. Tiny are then interwoven so that each wire of ou'j end passes between two wires of the other end. Flc. 35. - .\ I'lirni of Cniidiiclor Joint. 'I'he ends of the heart wires , ire then butted together, and the other wires of one end wound spirally round the o|)posite strand, and converscl)'. The splice is first made b}' hand, and afterwards finished off with the flat pincers. The two above methods give e.vcellent results with regard to continuity and mechanical strength, but increase the diameter of the conductor at the * Tills is assiimiii^' tliu contlticlor 10 bo composed of ;in ordinary scxcn-wire strand ; but these remarks would in this method equally apply for jointin}^ any other form of conduclijr s( far as the KCiKM-.d principle is conicrncd. 362 SUBMARINE 'I i;i,i;(;u.\i'i IS. joint ; this, thoiiLjli of little consec|ucncc in land lines,* would become a serious drawback in submarine cables, where the core must be enclosed in an outer sheathing of fixed and uniform diameter. l'"or this reason, one of the three following methods is to be i^referred : — (n.) The wires being first laid up again to form the original strand for about two-thirds of their length, three alternate wires of e(|ual length are I'K;. 36. — I'siial tniin of loiiil in .Siilini;uiia' CciiuUiclols. cut out of each strand, and the remaining four arranged parallel to the axis of the strand in both conductors. The two ends are then brought together, and each wire butted into the corres|)onding vacant space in the op])osite strand. Ihe whole is then covered with a serving of fine copper wire, extending beyond on cither side for a dist;uicc equal to the length of the joint. (,'''.) The wires com])osing the strand are first carefully re-formed over Fit:. 37. — JoiiitLT's Bench and Tools !n Operation ; Splicing the Coniluclor. the entire length of each end of bared conductor, .soldered together f and filed down to a long bevelled or tapered wedge (I'"ig. 36J, so that when laid together they exactly fit, without increasing the size of the conductor * Nowadays the above .somewhat fvu^'/i-forwct/ joints are scarcely ever adopted even for land-lint' jjurposes, tlioiij^ii perfectly etficient. + This is best effected by ilip|)inn the bared end i ulirely into a lump of molten solder on the solderiny iron, running it round the iron to ensure evenness, ami linally shaking ofTany superfluous lumps whilst still in the fluid state. JOINTINC;. 363 at the joint.* The bevelled ends havin^r Ijcen cleaned in tlie way to be presently shewn, a little further solder is applied to them ; + when the file is again used lightly to obtain smooth sharp surfaces. The conductor ends are now jjlaced in the \ ice, * the bevelled ends being fitted together (Fig. 37) and pressed against one another. These two wedge surfaces are then Krc. 38. — Applying Binding Wire 1" Motiillic Joint. soldered together. Over the joint and on either side, for a distance equal to its length, is wound (Figs. 38 and 39) fine copjicr wire of No. 30 S.\\'.(i. .012 inch), intended tf) bind the joint firmly together in a I'll;. 59. — Ciiniplcled Metallic Joint. ])ermanent man-ier, and to maintain communication in case of separati(jn of the bevelled surfaces by failure of the metallic joint. The whole of the * This iircparation for scarfiny the two conductor eiuls together to form a scarf joint (the principle of tiiis method) requires to be performed witli great care to ensure the two scarves fitting projierly and truly against one anotiicr, by their angles exactly correspond- ing as well as by a j)crfcctly even surface being secured. To carry this out in practice it is very usual to ha\e a ni( he cut somewhere (as a gauge) on the jointer's bo.\ (Fig. 37), into which the end of the wire is laid and filed away till tlush with the block. The wedge or ta])er is usually about one-third in length, but longer for big conductors. It will be obvious that the longer the taper the better, with the limit that it must not be so long as to be dis|)osed to break off, and this depends on the diameter. t One of the main practical points in soldering is to remember always to clean the surface of the iron previous to using it, either by wiping or else, preferably, by spirits of salts and emery cloth. Another point is that the iron slujuld be applictl as hot as possible without risk of damage. I In placing the ends in their respective clamps care must be taken not to allow the edge of the gutta-percha covering to come too close to the ironwork of the vice for fear of it getting seriously heated during the soldering of the joint. 364 SUHMARIN'K Ti;i,K( IKAIMIS. joint is then finally soklcrccl ovci.* This latter is the method universally a(lo|jte(l for the conductor joint of submarine lines of the present day. Tin Soldering. + — Ar already indicated, after a metallic joint is made ^ood, it is tin-soldered.* This is obviously indis|)ensable in the case of the last method described ; and by this means, in the instance of the other earlier methods, good metallic contact is ensured. Variations of tempera- ture have a tendency to force apart the interlacing^ wires, in unsoldered j(jints, and so increase the resistance of the conductor. Great chaiv^es of resistance occurred on the old aerial lines, even durintj the same day, where the ends of the wires were simply twisted round each other witht)ut * Tlie .spiral lappinj^ of fine binding wire war. originally intcntled in part to meet the conditions of the conductor being subjected to an undue strain, by allowing of a certain amount of drawing out -after the manner of a helical s])ring. To turn this to account, therefore, it is \ery often considered best only to apply solder at each end of the spiral and not along i'. s entire surface. Or, again, very usually there are two wrappings applied reverse ways, so that the wires in each cross one another. Here the tirst is soldered right along (the interstices completely filled with the solder), but the outside wrajjping is only soldered at the ends. 15cfore applying the binding wire its surface is first cleaned usually by drawing the length intended for use through a piece of fine emery cloth. It is applied (see Fig. 38) in the form of a tlat hand by being doubled into about four lengths. This spiral lapping actually formed the subject of a patent m 1H55 taken out l)y .Messrs Slalhani and Willoughby .Smith, as before stated, to meet the contingency of a teni|)orary strain or actual rupture of the conductor at the joint where it is naturally less extensible and flexible, besides being more brittle, than elsewhere ; and of course a fracture of any single joint renders the cable useless till repaired. t As Mr W. H. I'reece has pointed out {Electrical A'ci/cii', 29th October 1888), soldering is a term which should be applied solely to the process of uniting the surfaces of metals. It is effected by the intervention of a more fusible metal than that which has to be united. The soldering metal, called " solder " on account of the purpose to which it is turned, being melted upon each surface, serves- |)artly by chemical affinity, partly by the exertion of cohesive force — to bind them indissolubly together. ".Solder" is usually an alloy. It must not only be more fusible than the metal or metals to be joined, but it must (as already explained) also have some chemical affinit)- fi)r them. Hence it is that different sorts of "solder" are employed for different jiurposes. It is called either hard or soft, according as its fusing point is high or low. The test of efficiency of " solder" is a pecidiar creaking sound, called the " cry of the tin," which is heard when a stick of it is bent close to the car. I The soft solder used as the soldering agent for joining electrical cr)nductors (which used to be known as telegraphic solder) is comjiosed of equal parts by weight of ingot tin and pig lead melted together : expressed in /'////!', this would come to about two of tin to one of lead. Hard silver (or brass) solder is, however, invariably used for joining together the individual wires during laying up of conductor into strand form, being very fusible and non-corrosive. It has been pointed out by T. I'. l!ruce-\Varrcn {I'llcctriciiui^ 19th October 1878), that owing to the impurity and brittleness of many qualities of soliler, it is advisable, so far as telegraph work is concerned, to mix the right jiroportions of the metals comprising the soldering fluid rather than to purchase it ready made. jolNTiNc;. 365 soldering; and tlic difficulties in workin^f these were notorious. 'I'heiv would he diUif^er of the same sort of tiling in tlic case of submarine cables, which are tested at 75 1'"., and afterwards laid on the sea floor, where the temperature may be as low as 35 !•". The conductor is cleaned just before soldering fas already described; with a little spirits of turpentine or naphtiia, and then dipped into, or covered with, powdered rosin* or stcarine, b)- way of a flux-'- for the solder.* i\ sinall ([uantity of solder is melted on the soldeiing iron and ])oured over the joint iti a small continuous stream, until all the interstice.s of the wires are completely filled u|).§ Immediately this is effected, two or three slij^ht blows are given to the conductor as a test, anrl in order to detach any small portions of alloy which may not have properly adhered. The solder, when cold, is finally worked o\er, or smoothed down, light!)', with a fine file to remove any possible roughness or irregularities, and the jointing of the dielectric is then proceeded with. * This is now sometimes termed resin, but the old name (rosin) is prcfcraljle for this, if only as a distinction from rrsi/t as used in a chemical sense. + The flux action is that of i,'^ the surface of the conductor ( lean and llnis permitting clean metallic contact with the solder -by preventing the formation of a thin film of oxide ("scilc"), which would naturally take place otherwise durin,' the jnocess of soldering owing to the heat introduced. I Spirits of salts (/.v., hydrochloric acid and /in( ) have been used as the flux agent for this purpose, as it is more con\enient and effective, besides cleaning the wire at the same time. It is, however, nowadays usually objected to on the ground of seriously eating into the copper conductor, by introducing a continuous chemical action between the former and the solder. Moreover, like sal-ammoniac (which is also sometimes used) it harbours dampness, owing to the fact that it does not dry up. Howevei, both of these latter arc con\enienlly and s;ifely used for the le.-.M \ ital niatlcr of effecting a joint between the iron sheathing wires and an earth wire at the testing hut or cable station. S A very usual way of carrying this out in practice is to rapidly run the hot soldering iron underneath the bared conductor at the joint, and simultaneously run a stick of the solder along the top of the conductor so heated. 366 sL'itMAkiNK ti;m;(.kai'IIs. SKCTION 3. -JoINTINc; IIIK InSIM.ATION : (ii;'ITA-l'i:K( HA C'OKKS. Tlu; joint ill tin; citiidiictor almost iiivaiiablv a scarf joint — is after a littlt; practice a fairlj- siiii|jlc matter. Tile joint in the dick-ctric, however, introduces nuich greater scope for really serious misha|)s flue to improper workmanshi|), as will he c\|>laincd later. It suffices here to say, that there is considerably more practice rc(|uired in the case of the flielectric joint, the difricully bein^^ at first to keep all air bubbles excluded from the material while hot, and to finish with the jointed conductor perfectly central in its insulatinj^r cover. First of all, the ends of the core are usually pared off to avoid joininj^' to the ^utta-pcrcha those portions which have received heat from the soldcrinff, and which may be in some dcj^'rec injured.* The metallic joints and the ^aitta-percha ends are next cleaned by bein^' wiped over with a clean bit of ra be .Hjjjlied. .Some authorities object to it for joints partly on the same grounds as tli(.'y do for the conductor generally />., that of injuriously acting on the gutta-percha, and also on the score of its application in joints tending to introduce air-holes afterwards. S .After being heated over the lamp this iron should be- thoroughly wiped with a clean rag before touching the " Chatierton " or gutta jjcrcha with it. II It is very usual to blow the end of the flame near the gutta-percha. jOlNTINi;. 3'57 III this way tin; ^aitta-pcrcha is softcnwl on both sides of the joint for nearly 2 inches, aiul the two ends of ^'utta-|)ci(;ha arc then ^rachiaily fwith the fingers*; drawn towards one aiioth(;r till they are about A inch apart, the core being turned round with a twisting motion backwards anfl for- wards throughout tin," operation. One end {n in l'"ig. 41; is then drawn down to a thin film, whilst the other U>) is gradually, by dexterous inain'pu- l''lc;. 40. — I'irsl Sla^c of (liUlaperclia Joint. lation fl-'ig. 40), drawn over it, until thi' joint is envelojjed in a covering materially thinner, but nearly as uniform — -if performed by a skilled work- man — as the rest of the conductor. The first covering is then completed. Till thickness of insulation is about the same as that of the first coat of gutta-percha in the rest of the core, as is, indeed, shewn in I""ig. 42, which Ik;. 41. — I'irM Staf^c of (;iilla-|j(;rcha Joinl. represents the joint at this stage. The joint is then kneadcfl and smoothed down with the tooling iron. After the whole of the "draw-down " has been thoroughly worked over with the thumb and forefinger, it is allowed to cf)ol and "set" for a while, after which the surface of the draw-down is rougheneil with a knife. It is then slightly " lamped " over again, preparatory to Chatterton's com|)ound Kli;. 42. Completion of I'irsl Sti'jjc in ( iiiUa-pcrclia joint. being lightly a|)|)licd Tor adhesive purposes) as befcjre, though in this ca.se some consider it better to n'// the hot end of the stick of " Chatterton " over the gutta-percha, instead of dabbing it on in lumps. In any ca.se, this * The fin},'crs re(|uirc usually to be slightly moistened with saliva to prevent sticking during maniiJulation of the semi-plastic gutta-jjcrcha. 368 SUHMAKINE TELEdRArilS. process is followed by "lamping" and toolinj^ over the compound until an even surface of compounded ^utta-percha is obtained, ns])ccial care being taken not to overdcj ♦ihe heat for fear of damaging the gutta-percha, and causing subsequent air-holes : at the same time the heat must be sufficient, or the compound will be liable to remain in hard lumps. One of the strips* cf gutta-percha sheet roll kept pur])osely for jointingf is then carefully softened by the assistant jointer by warming over the spirit lamp. When sufficiently softened, a piece about 21 inches wide is cut off the sheet with a pair of scissors, which is next stretched in order to reduce the thickness to the required limits ; the length of the sheet will now be just what is required for the joint. The jointer then takes the strip into his fingers (which are moistened with saliva to avoid sticking) and apnlies it from underneath lengthways to one end of the core, and being firmi) pressed is drawn along the length of Fli'.. 43. — I'irst Covering c 'aiUa-pcrchii [ciiiUs. the joint underneath; the edges are rai.sed (I^'ig. 43) and gradually by a uniform pressure brought t(jgether at the top so as to completely surround the core.:J: At this stage — and from time to time — it is usually found advis- able to warm up the sheeting and the core by " lamping," to ensure better adherence ; as well as to facilitate good workmanship in the way of an even * Before starting work the assistant jointer usually cuts several strips off from tne roll of gutta-percha convenient for handling over the spirit lamp, of suitable dimensions respectively for the two coverings for which it is used — the thickness and number of each bearing some kind of corresponding relation very often to that of the separate coverings of the rest of the coic Usually, however, two such strips are applied to each joint, the last (outer one) overlapping that previously by an inch or more at each end. t This gutta-percha sheet forms part of the " stock-in-trade" of a jointer's bo.\. It is generally kept in an air-tight metal case, usually filled with water, to preserve its charac- teristic qualities. It is most important that it should be thoroughly clean as well as quite free from moisture at the time of application to the joint— as much as that the kneading tools be so kept. I The reason for this procedure is to make sure there are no air-bubbles imprisoned by commencing at one end and gradually squeezing the strip against the core at every part till the joint is en'irely covered flush with the rest of the core where any spare ends are cut off. Should there be any sign of an air-bubble or moisture, the hot tooling iron should be applied to the spot at once so as to draw it out, the place being made good afterwards. JOIXTING. 369 and uniform coverin<,r. Indeed, it is best to turn the joint upside down* after heating en one side with a view to warming it on the other, thus helping to drive off any moisture from the [lands that may have found its way amongst the core and sheeting. The jointer now pinches the edges tightly together between finger and thumb t(j obtain firm adherence at the seam formed between the new strip and the old gutta-percha inside. He then trims off the exce.ss with a pair of '"^ nt sci.ssors.f The heated tooling iron should then be jjassed over the seam so as to open it again. After this it is once more pinched up, the result being that any air is forced out that may have pene- trated. In the last p'nching up process, it is best to make one edge c.erlap the other very slightly, so that the warm tool finally run over the .seam may more perfectly seal it up ; or, if the edges are merely butted, great care must be taken that they properly meet. The joint is now again " lamped " over and kneaded with moistened thumb and forefinger, care being taken to preserve its shape and to knead evenl\' all round. The iron, heated to the required temperature, is next used to smooth off any inequalities in the gutta-percha, in order to make a better join between the two ends of the new layer and the adjoining portions of the old gutta-percha by working down smooth the ends of the strip so as to taper off gradually on to the core. The same operations — softening (by lamping), kneading, and smoothing over — are repeated a number of times until the outside surface is faultless, and there are no signs of air-bubbles escaping from the gutta- percha under the kneading influence. Finally, this .second covering is perfected by the joint being rubbed into .shape with the moistened palm of the hand. Followed by the same warming, compounding, and tooling over, another gutta-percha .sheet (forming the third covering) is then applied to the joint in precisely the same vvay, * equal pains being taken in the sub.seciuent hand manipulation by way of kneading and tooling down irregularities, as well as in tapering off and smoothing over the joint at each end between the main core and the gutta-percha sheet. In this covering the strip is longer by an inch or more at each end than * In doing this, the jointer aad his assistant should turn it over simultaneously, so as to avoid puttin^f a twist in the joint. Similarly, when the operation is concluded, the joint should be turned back in the opposite direction in order to take the twist out again, other- wise a permanent twist will make its way into the core at each joint. + In order to effect this, it is necessary to pass .he blades of the scissors over the tongue, as already explained. \ It is, however, advisable to apply the outside strip, bit by bit —starting from the opposite end to what was done with the first strip— and thus working the strip on by hand in a reverse direction this time. ac 370 SUBMARINE TELEGRAPHS. the previous one so as to ensure it completely overlapping the latter, thus bringing the joints with the rest of the core at either end to different points and consequently ensuring a more general tapering. In applying this outside covering care must be taken, moreover, to see that the centre line (or the full part) of each strip comes immediately over the joining line (or seam) of the strip preceding, so as oppose the lines of weakness in each layer (Fig. 44). It is necessary also to avoid softening the Fig. 44. — Section finished layers beneath, when warming the outside gutta- of Finished Gutta- percha, in order that the kneading will only affect the percha Joint. layer actually under treatment. When the kneading of the last layer is finished, the gutta-percha is once more and finally slightly softened. Then, with the palm of his hand well moistened, the jointer rubs down the joint. This rubbmg must be done uniformly and equally all round ; it tends to solidify the joint and inadvertently assigns to it that highl)- polished and finished appearance so characteristic of good work. <>I.INOH-» Fk;. 45. — Alternative Gutta-percha Joint : Commencement of First IVocess. We have here only endeavoured to describe one \ery usual method of gutta-percha jointing. B)' another method, very largely adopted, the gutta-percha sheet instead of being applied as a longitudinal strip, after the core has been lamped and compounded, a strip, about 6 inches long and i inch wide is (after warming) wound round the core (Fig. 45) several times in the form of a knob (Fig. 46) over the centre of the usual draw-down, forming the first covering. The knob is then quickly worked for about 4\ inches in both directions with the Fic. 46. — Completion of First Stage. finger and thumb, so as to make the new gutta-percha meet that of the rest of the core on about the same level, where the joins of the two gutta-perchas are then tooled down with the heated iron. This then, after being care- fully worked and tooled to an even and gradual tai)ered surface, completes JOINTING. 371 the joint so performed. This method has certain advantages. Probably, however, with equally skilled workmanship the two joints are equally efficient — in fact, as efficient as could possibly be. A well-made joint is usually, when finished, somewhere between 6 and 8 inches in extreme length, and but very little larger than the adjacent core, tapering away gradually, as shewn in Fig. 47, on either side from the centre.* The joint being completed, it is first allowed to cool by being placed in cold water — or having cold water poured over it — and afterwards hung up in the open air. It is important that steps should be taken at once in this direction, to prevent any damage or decentralisation of the conductor in its insulating envelope. At sea^when time is of first importance — to accelerate the action, the core is usually placed in a trough of iced water ; or, still better, in a special Fir.. 47. — Finished Gutta-percha Joint. cooling mixture composed of a solution of ammonia and saltpetre, the proportion being — Muriate of ammonia . _ . . 5 parts. .Saltpetre - - - - - 5 » Water - - - - - - 16 „ This mixture inust be kept well stirred until the joint has sufficiently cooled.t The mixture is placed in a kind of tray or trough, and the joint held down in it by i.vo rings at the bottom for somewhere about ten or twenty minutes, after which the joint is tested. The special construction of this tray (to meet the electrical requirements) will be found fully dealt with elsewhere. * A section of the joint— sec Fig. 44 — even when examined under a lens, should show a perfectly smooth surface round the conductor, and there should be no su)(gestion of bubbles, or of moisture. When cut through longitudinally, the copper should be found exactly in the axis of the cylinder, and adhering (irmly to the insulation. The several layers of gutta-percha should be traceable by very fine black lines of Chatterton's compound lietween them, and there should be every evidence of perfect adherence throughout. + When, however, the above is not available, an excellent cooling mixture consists of 2 oz. sal-ammoniac, 2 oz. washing soda, 2 parts fresh-water. This has been found to cause the solution to drop in temperature as much as 21" F. (from 78" to 57 ) in the course of two minutes. 372 SUB\rARINE TELEGRAPHS. At the factory, the joints in the core — which occupy about an hour* — are each rigorously tested, as soon as they are effected and sufficiently cooled, by means of an electrometer or galvanometer, and what is known as the accumulation method (due to Mr Latimer Clark), whereby the effect of the weakest current passing through the insulating sheath at the joint is inten- sified many fold in its effect — and, indeed, shews itself where it would not do otherwise. This test is very fully described in Mr Young's work on Testing, with all the different ways of carrying it out.t On the other hand, as a rule, owing to the prevailing conditions, it is very often the custom not to attempt to test the joints made at sea. | Others, however, go through some sort of test (as a control on the jointers to a certain extent), as shewn elsewhere, though by the test which is not uncommonly applied, it would require to be an extremely weak joint to call any special attention. By way of general review, it may be remarked that the jointer must be always careful to heat with the lamp any portions of the joint he may have touched with wet fingers, before laying on another layer of compound or gutta-percha, so as to drive off all trace of moisture. Should there be the slightest sign of perspiration on the jointer's hands owing to the heat of the weather, he should immediately wipe them with a clean cloth ; c •, better still, dip them in naphtha, the rapid evaporation of which will cool the surface of the skin. This should be repeated during the continuation of the work as often as necessary.§ It is usually understood that all dirty work is to be done by the * Hy practised hands they can sometimes be effected in forty to forty-five minutes, including the time taken (lo to 15 minutes) over the braze in the conductor. In the tropics — aboard ship or ashore — they require a quarter of an hour longer for cooling and hardening by iinmersion and bathing in iced water as aforesaid, unless one of the above mixtures be available. In the latter case, th^ joint is almost instantly rendered fit for covering up previous to the splice being started upon. + "Electric Testing for Telegraph Engineers," by J. Elton Young {T/ic Electrician Printing and Publishiug Company, London). \ In present practice, jointers very rarely fail to make a perfect joint, having, as a rule, served their time in the factory, where joints, of necessity, occur at every three, or even two miles— according to the type of core. They are, moreover, specially picked out as reliable mon for sea-work. S .Some men are actually prevented altogether from making good joints on account of being so prone to perspiration. A joint requires continual handling during manufacture, and it will be readily under- stood that perspiration is liable to affect the gutta-percha in such a way as to prevent a proper junction between the several coatings. In further explanation it may be remarked that the perspiration, coming into contact with the hot gutta-percha, sometimes turns into steam, which, underpressure, bursts through the layers of gutta-percha. JOINTING. 373 assistant jointer, leaving the jointer free for the requirements of joint coverings, where cleanliness is so important an item. In holding the core it should be taken firmly between the thumb and forefinger at such a distance from the joint as to be beyond the influence of its heat, for the gutta-percha here should always be kept hard. If the hands be too near the joint, they may press the material where it has been softened by the heat, and so cause serious damage. It is of the greatest importance that the strips of gutta-percha used in making a joint should be, as far as possible, of the same quality as the gutta-percha employed for the rest of the core. With gutta-percha of widely different quality, it is almost impossible to produce a sound, homo- geneous joint, and many faulty joints have been due solely to dissimilarity in the materials used, though each material may have been good of its kind.* Faulty joints are generally caused by — (a.) Unskilful cutting of the copper wires, causing nicks. (/>.) The wires being badly laid up, or not filed to a true scarf (r.) Faulty soldering. (rt'.) The conductor being centrally displaced through unskilful knead- ing, or tooling. (e.) Lack of efficient adherence between the conductor and the insulation. (/.) Air-bubbles between the different layers of gutta-percha due to insufficient pressure when applying the strip. (g:) Burns on the gutta-percha caused by careless use of the lamp, aiul overheating. (//.) Imperfect adherence between the layers of gutta-percha or Chatterton, through moisture or want of cleanliness. (/.) Accidental abrasions. If any water, or even moisture, finds its way in anj- part of the core during the manufacture of the joint, it is sure to be the cause of trouble afterwards if the gutta-percha is applied over it.f This, owing to the water forcing its way out under the subsequent pressure (when laid at the bottom of the sea), and leaving a hole in the insulating envelope, which * Thus anytliing' like a permanent joint with an okl cable, the gutta-percha of which has been exposed, is an almost hopeless matter. + Hence the importance of thoroughly drying the joint under construction at its various stages by " lamping" it over continually with the naphtha spirit lamp. 374 SUHMARINK TELEGRArilS. may or may not fall a ready prey to more water reaching the conductor ; but, in any case, leads to a more or less serious insulation fault. Another frequent cause of this " blowing " action of the irutta-percha is that of air finding its way into the core during manufacture. Should there be any such air-bubbles imprisoned in the joint, they are almost certain to lead to ruptures in the insulation sooner or later when under the great pressure at the bottom of the sea, which amf)unts to as much as \\ tons per .square inch for every i,ooo fathoms depth. When the cable is, on submergence, subjected to this pressure, any places where air is imprisoned are, indeed, invariably burst open, thus causing .serious faults. It is, therefore, as desirable that any chamber of air shall be exploded, and the air let out during manufacture of core, or joints in core, as that moisture should be. Joint-making in tropical climates is a peculiarly troublesome and delicate operation on the above accounts ; firstly, becau.se the strong evaporation of a hot climate especially tends to draw out any moisture from the gutta-percha ; secondly, owing to so large a quantity of moisture pervading the atmosphere ; and, thirdly, on account of the difficulty some- times experienced in getting, or keeping, the gutta-percha sufficiently cool and hardened. However, the special conditions and provisions regarding joint-making at .sea — and especially with reference to hot climates — are gone into more fully elsewhere, with reference to cable-laying operations. Finally, it may be remarked that there is more in the actual carrying out of successful gutta-percha joint-making (as regards really pernianent joints for submarine purposes) than might at first sight appear to be the case. There are, indeed, many practical details which make all the difference in the degree of success attained. For this reason, jointing is not a thing which can be properly learnt from a book — perhaps even less than many other operations in engineer- ing practice. To attain anything like perfection, the student should put himself under instruction from a professional jointer. These notes on the subject are only intended to give an idea of the main points involved, and .some kind of notion of the principles in practice, as a guide for the amateur who may be suddenly — under stress of circum- stances — required to act in the absence of professional comrades.* Practice alone will further help. * The matter is gone into soinewhat at length, on account of its vital importance in cable work. JOINTING. 375 It may be said generally that yntta-percha joints, as effected nowadays by first-rate jointers under favourable circumstances, are as a rule (for sub- marine cables), practically speaking, as perfectly homogeneous and absolute — mechanically and electrically — as the rest of the core.* * Actually when compared electrically against a similar length of the same core, the joint almost invariably tests better. This may be to a great extent accounted for, however, by its slightly greater dielectric thickness. Eastern and South African Telegraph Company : (Quarters of one of the Staff at Delagoa Bay. 376 SUBMARINK TELEGRAPHS. Section 4. — Jointing Vulcanised India-rubber Cores. The soldered scarf joint in the copper conductor having been made in the usual manner (as shewn in Figs. 48 and 49), and left with a smooth and clean surface, the external tapes and braidings should be stripped back from the rubber. The more or less bevelled surfaces at the edge of the old rubber, which have necessarily been exposed during the making of the Flc. 48. — Si-arf Joint in CoikIik-lo . joints in the conductor, should be well scraped — or, indeed, pared away — and then wiped or painted over for an inch or so with pure benzole or naphtha to free it from dirt or grease by actually dissolving the outer surface.* A strip about I inch broad — or more than one, as the case may be — of Kic. 49. — Finished Conductor Joinl. pure rubber treated in tlic same wa)' (so as to obtain the natural coherence of two similar fresh rubber surfaces} and having about the same thickness, as the original inner strijj, is ajiplied, under tension, cither longitudinally or spirally round the conductor — usually the latter — so as not only to cover the entire metallic joint, but also (see Fig. sO to overlap the inner edges of the rubber in the rest of the core. There is an advantage in the inside covering of the joint being applied spirally in that it permits of it being * After cleaning as above, it is \ery usual in present practice to first cover the metal joint and exposed conductor with one lap of ^ inch broad cotton tape (sometimes coated l-'ic. 50. — Metallic Joint Enveloped in Tajie. with india-rubber) as shewn in Fig. 50. This prevents action between the diflferent rubbers or between the ibbcr antl the copper wire in the event of any sulphur having percolated as far —and gives a fairly even bed for the rubber strip that follows. JOINTING. 377 laid on tif^htly under a fair pressure. In either case a joint is very often made with the inside la)'er of pure rubber, merely by pressure. Where, as is usually the case, more than one layer of pure rubber is necessary in order to build up the joint to the same thickness as the inside coat of the rest of the core, the successive layers are each applied (under considerable tension) in alternate directions. The ends of each of these pure rubber strips are very usually secured down by means of quite a small quantity of india-rubber solution.* This j0l,00imBmt0mmtggifffitiMamggf- Flc. 51. — First Rublier Covering. solution may, indeed, be applied outside each tape to ensure their uniting together, care being taken to allow sufficient time for the spirit to evaporate before applj-ing another tape. Then over this and the bevelled surface of the old rubber are lapped layers of mixed and vulcanising rubber,t followed by an outside covering of waterproof tape, varnished over all, until the diameter of the completed joint (Fig. 52) is about equal to the entire thickness of the original core.* The rubber should be put on tightly and evenly, so as to leave no spaces filled with air — indeed, it is actually stretched slightly in the process, as a rule. Fli;. 52. — Complelcvl Imlia-niblier Joint. The rubber joint so effected should first be covered with a prepared tape put on spirally, then with a piece of calico sheeting firml>' rolled on * hidiarubber solution consists of 20 parts of rubber which has undergone mastication in 100 parts of benzine or mineral naphtha oil. t These arc usually composed of two coverings of prepared tape, § inch broad, laid on in opposite directions, with strong shellac varnish between them. I By the old method of joint-making in Hooper's core, the oxide of zinc separator was maintained in the joint by wrapping the pure india-rubber strip round with canvas strip impregnated with oxide of zinc. This was then covered with two strips of vulcanised rubber (/.c, rubber sprinkled with flowers of sulphur), the last overlapping the first — a plan still often adhered to. 378 SUliMARINK TELKCRAIMIS. loiiyitudinally. This again is tightly bound up with strong selvedge cotton tape applied spirally. The sheeting and selvedge tape are only applied to act as a mould and hold the joint in shape under pressure whilst it is being cured. They are removed again as soon as the vulcanisation of the joint is completed. The process of curing — as has already been shewn in the chapter on india-rubber — involves apparatus for maintaining the article under operation at a high temijerature for a given length of time. At the factor)-, this con- dition is readily met by the joint being kept in contact with steam.* A convenient and fairly accurate test of the degree of vulcanisation is to try and indent the rubber, when cool, with the thumb nail. If properly cured, the rubber will yield to the pressure, but no mark will remain. If, however, the imprint of the nail is left, the rubber is not sufficiently cured ; and if it is hard and unyielding, it is probably over-cured. When it is known that the joint has been properly made with the right amount of vulcanisation, after being electrically tested in the usual way, it is finally protected externally by a lapping of strong tape, which should extend an inch or so over the braiding; or serving. This latter very often finally receives a coat of varnish to further imbue it with the necessary waterproof qualities in correspondence with the rest of the core. The length of time required for a vulcanised india-rubber joint is a varying quantity, according to the exact routine adopted and prevailing conditions. It usually occupies somewhere about three-quarters of an hour, but the curing process may run into as much as three hours, or it may only take an hour, depending on the type of core, etc. On the other hand, being practically independent of temperature, little or no time for cooling is necessary. The principal causes of faults in india-rubber joints are the same as in gutta-percha — i.e., air-holes and moisture. The same precautionary care is necessary to avoid them, including " lamping " over, from time to time. Successful and reliable joint-making in india-rubber cables, especially as regards the vulcanising, is a much more uncertain matter than in the ca.se of gutta-percha. It will, indeed, be obvious that the joint can never be as homogeneous an affair in the former instance as in the latter. Thus, with rubber joints more than ever, instruction in their manu- * For land-line, and aboard-ship, work, different forms of portable " cures " have to be used, but these are matters foreign to our immediate subject. JOINTINC. 379 facture can only be satisfactorily obtained from a professional jointer and by much experience.* These notes are only intended to j^ive a [general idea of the principles involved in practice : the student can best find out further details for himself by experience. * The main requirement in vulcanised rubber jointing consists in recognisin^'^ the right degree of curing, besides care and experience in giving the right temperature, and time for the same. No great manipulating skill (as in gutta-percha jointing) is necessary ; for here the applying of spiral (or longitudinal) tapes is comparatively speaking a simple matter, as against the kneading with a hot iron and fingering required for gutta-percha joints. Eastern and South African Telegraph Company : .Superintendent's House, Capetown. TMz:. CHAPTER IV. P^^fiOP 5.k-i^ 1^^ ^^ A " Cal)lc Sh(>i>. MECHANICAL PROTECTION AND STREN(iTH. Section i. — Submarine Horers — History of Metal Tape — Present-day Application — Alternative Suggestions. Section 2. — Inner Serving : Historical — Constitution of Jute — Tanned Jute Yarn — Routine of Inner Serving Application — Serving Machine — Lay of Innor Serving — Miscellaneous Particulars — FormuUu, etc., for Weight of Inner Serving. Multiple-Conductor Cables : Where Desirable : Advantages and Disadvantages. Suction 3. — General Description of Ordin? y Sheathing : Types. Testing Iron Wire — Tension and Elongation Test : Torsion Test : Galvanising Test -Routine of Cable Sheathing— Bright and Clark's Compound — Compounding of each Iron Wire — Taping each Wire. Section 4. — Operation of Sheathing : Leading Principles Involved — Skeleton-Frame Machine: Disc Machine— Modern Imjjrovements Lay of Wires — Points in Con- struction—Formula for Weight of Iron in a Cable : Trial Specimens. Section 5. — Bright and Clark's Cold Compound -Outer Canvas Taping— Bright and Clark's Hot Compound — Cooling the Cable- Relative Merits of Outer Tape and Yarns : Outer Yarn Covering : Hemp Yarn Applied Externally : Jute Yarn Applied Externally; Outer Hemp Cords : External Canvas — Tape ;..nd Hemp Cords — Center Covering: General Particulars — Hauling off Completed Cable- Rate of Cable Manufacture. Section 6. — External Whitewashing on Way to Cable Tank : Coiling into Tank — Test- ing during Manufacture - Stretch of Core during Sheathing. MKCHANICAL PROTECTION AND STRENGTH. 381 Section i. — Metal Taping. For those portions of any cable which are about to be deposited in waters where marine ort^am'sms exist, the core now very usually first receives a sheath of metal tape by wa)' of protection. Submarine Borers. — These enemies to cables consist mainl)' of what are known to naturalists as Teredo nai'aHs* .xylop/iag the up half being held down by a weight hung on a projecting arm. As already implied, arrangements are made for water to drip on the core as it receives the first .serving of jute, with a view to keeping the jute damp, besides wetting the surface of the dielectric, in order to ensure the detection of any flaw therein — at anj' rate, on pressure being sub- sequently brought to bear at the lay plate by the iron wires, the water being then literally squeezed into any possible flaws. This watering of the core and .serving is put into effect by the supply of water to a small jjipe H (Fig. 54) fitted with a tap. The rapid rotation of the hollow shaft and disc, combined with the slow longitudinal movement of the core, causes the jute yarns tii be wound, or spun, on spirally. ■"■ Here it is a disc machine wliicli is shewn ; but the same work may be equally well performed by a cylinder frame machine, as described further on in connection with the iron wire sheathing. Each have their advantage, and sometimes both jirinciples are applied in the same machine. The disc is capable, generally speaking, of holding more bobbins — some being placed on each side of the disc -whilst also taking up less floor space. On the other hand, the cylinder frame— the centrifugal force being less serious by this arrangement —permits of a greater weight for each bobbin, and therefore a greater length of wire. In order to get an increased numlier of yarns for increasing the size of the serving for heavy types, an extra disc loaded with bobbins may be conveniently applied at the back of a cylinder frame machine, thereby combining the two arrangements in one machine. MECHANICAL PROTECTION AND STRENGTH. 397 The bearings in which the shaft F c. revolves are kept cool by wat^r constantly dripping from the pipes v and \\. Lay of Inner Serving. — Fitted to the revolving part of the machine is a brake, consisting of a block of wood at the end of a lever arm, and this may be pressed against the edge of the disc carriage A, to stop it turning, as required — for instance, when it is necessary to feed the carriage with a fresh bobbin of jute, or to effect a join between the ends of a broken yarn. The function of this se'-ving round the core is, as before stated, almost solely that of forming a protection of a certain thickness to the core, from the iron wires, on the one hand ; and, on the other, as a bed for the latter of such an outside circumference as will permit of the required iron (wire) arch being formed. This being so — any questions of strength being scarcely, if at all, relevant for the inner serving* — it is usual to apply the jute with a distinctly short lay (varying from 2 to ji inches, according to circum- stances), by way of making the firmest possible packing to the core, in order to prevent any iron wire finding its way between the yarns. The lay is determined by the relation borne by the speed of drawing off to the revolutionary speed of the disc carriage. The speed of the revolving disc is always maintained the same — a fairly high maximum speed, f with few and light bobbins and a small disc or cylinder — but the " draw-off" speed is altered by means of change wheels according to the speed required to give the desired lay. If the lay is .shorter than a certain angle, the outer diameter is liable to be too great for the wires to close round pnjperly; and if too long, the packing is liable to be insufficiently dense, or secure. To correct either of these, the s]jced of the haul-off gear should be increased or decreased, as the case may be, or — under some circumstances — by the revolutionary speed of the bobbins being decreased or increased. Miscellaneous Particulars. — The jute yarn used for this purpose is usually "single ply" — i.e., one yarn — but sometimes two or even three ply is adopted when any appreciable strength is desired. * In fact, the jute used for the inner servinf,^ being employed only as a packing or lied, has generally a very low lireaking strain : it is of so little value practically and is so unreliable that it is not, as a rule, considered. + 130 revolutions per minute is very usual with an ordinary rate of draw off to give an average lay. This is equivalent to about four miles of core being served in the course of a working day. 398 submarinp: telkgraphs. The jute yam is seldom, if ever, tested for breakint^ strain, but sometimes a limit to the number of twists in a given Icnj^ah of the jarn is specified.* The various skeins of yarn are wound, by means of a swift, to fill up the bobbins. Each bobbin holds on the average somewhere about a mile length. Strength not being considered, joints are only limited as far as possible on the score of their involving very slight lumps, such as mean stoppages, though of extremely short duration. These joints arc usually effected by a whipping of single spun yarn (or twine) being bound round the join ends. Matters are so arranged in practice that the bobbins of yarn run out at different points so as to avoid the joints in the various yarns occurring coincidently. The number of bobbins depends, of course, on the type of core to be covered and the type of yarnsf used, as well as on the thickness of serving for the particular form of cable in question, the object aimed at being to have the closest possible packing, whilst maintaining perfect evenness. With an average core, about twenty-five separate yarns in all J (each mounted on a bobbin) is a very ordinary form of first serving. Within recent years there has been a tendency in some quarters to reduce the quantity of inner serving for deep-water cables to as fine a point as possible in order to reduce the number of iron wires required, and, there- fore, the weight and bulk of the entire cable. This may be safely pushed to a fine point, where a great thickness of gutta-percha surrounds the con- ductor, and where the cable is not likely to experience a high temperature. Thus, the deep-sea type of the last Commercial cable made by Messrs Siemens Brothers — an excellent type in every respect — had an inner serving of this description. However, such space as there was between the core and the iron wires was very th(3roughly filled in§ by what may be termed a tight packing. It is usually an acknowledged axiom that, with a given * For a "single," the I'ost Office authorities often specify a limit of ten to twelve twists in a 1 2-inch length. + The type and number of yarns employed varies with the description of cable. Thus in intermediate or shore-end types, the yarn adopted is invariably thicker than that used for deep-sea cable. I However, different factories have different practices in this respect, as in others. Some employ a larger (or smaller) number of yarns of less (or greater) size to produce the specified bulk of inner serving. A greater number of yarns introduces more stoppages and joins, but should secure a denser, more even, and surer bed. Cienerally speaking, as large yarns are used as is practicable for the space to be filled, whilst providing for a firm packing. The number of yarns may be, in fact, anything from ten to fifty, or more, if the former, it would, probably, be in one application only. S It must be remembered, moreover, that the wires are very small. Again, in any close-sheathed cable, the wires butting firmly against one another act as a complete tubular shield. MECHANICAL PROTECTION AND STRENGTM. 399 space between the core and cylinder of iron wires, it is better that there should be overmuch, rather than undermuch, packing ; thus ensuring the jute fitting well into the interstices of the wires, whilst also securing good coilable qualities, though at the expense of material, bulk, and coiling space. Springiness in a cable is, in fact, obviated (i) by plenty of inner serving, and (2) by taping of each iron wire. The former must not, however, be pushed so far that the cable at all approaches an alternate iron and jute pattern. The inner serving for heavy types must not only be sufficiently greater in quantity to secure (for safety) the same thickness as with a deep-water type, but must also have an increase in this respect to combat with the area of the large wires. It is not, however, necessary to have the same quantity in a given area — i.e., the inner serving is not so tightly packed — as in a small type of cable with a limited area for the wires. This inner serving is almost invariably applied in two separate appli- cations, one above the other, laid up the opposite way, to ensure good packing. Thus the core served as above, in being drawn from the preceding machine, is usually drawn through another preci.sely similar machine, just beyond it, as shewn in Fig. 54, which is made to spin in the reverse direc- tion for applying an opposite lay. In other respects they are precisely the same with corresponding arrangements in each, and the two servings are exactly similar — indeed, they may be regarded as a single machine, each part of which effects a part of the same operation. In the figure, the core is shewn coming from above; but, of course, it may be in the same shop. Moreover, the sheathing can be performed at the same operation from a part of the same machine as the serving — by a combined serving and sheathing machine.* On the other hand, the serving is sometimes (where more convenient) effected in a .separate shop, and the served core drawn from tanks as required — or direct from the serving machine — for sheathing. Anyway, the serving machine, in order to save ground-floor space, is very usually on an upper floor, and placed just above the sheathing machine it is intended to feed * This is a very usual plan in modern practice, for it introduces a saving of time and hands — though perhaps less sure. Hy the other system, an opportunity presents itself of testing the core after being served, and this is here always taken advantage of. Where the core is brass-taped, the operation is either performed separately or else the jute serving is applied at the same time. In the latter case, the sheathing and outer coverings form a separate process ; and where the former is the system adopted, the jute •"- laid on contemporaneously with the sheathing wire and outer covering. Thus by either plan it is a case of two opciations in all. 400 SUBMARINE TELEGRAPHS. with served core. Where the latter is not required at once for cabling — or where it is the practice to test it first — after the serving operation, the core is coiled down into tanks filled with water. Formulae, etc., for Weight of Inner Serving. — For calculating the lueighl of inner serving in a cable, in Fi^;. 56, let Dj be the diameter of the centre line of the iron wires in inches ; D the diameter of the dielectric in inches ; d the diameter of a single wire also in inches ; and n the number of iron wires. Then transverse sectional arc of the jute for hemp) is 0.7854 {Vi^--Vi--id'^) square inches. And the weight per N.M. of jute, or hemp, serving required to efficiently fill up the space between a given core and cylinder of iron wires as above is approximately ^•a follows: — 56. — Inner Serving. 20»(Di2-D2-^^/=')cwt. It is also very usual, in the first instance, to make up various machine- made specimen lengths of a fathom or so, for purposes of examination and experiment. This trial is sometimes found useful in order to ascertain whether the amount of jute settled on for the inner serving could be properly got into the space between the core and the iron sheathing arranged for. Multiple-Conductor Cables. In the case of a multiple-core cable, i.e., a cable to contain several — two, three, four, five, six, or even seven — insulated conductors, the central heart which is drawn through the hollow shaft is usually a hemp or jute yarn (though sometimes an insulated conductor), and round this are laid u]) alternate insulated cores and hemp, or jute, yarns.f The number of bobbins will then depend on the number of conductors, with an intervening bobbin of hemp, or jute, yarn for protective, " worming," purposes. * It shoukl be pointed out, however, that the above constant varies very much accord- ing to individual views and practice. The formula is, indeed, only given as presenting an idea of the principles adopted in such calculations. t These "wormed" cores arc then served with jute in tiie usual way— />., as in the case of a single core. MECHANICAL PROTECTION AN!) STKENGTH. 401 Here the cores to be laid up together are reeled on bobbins and placed in machines somewhat similar to those described in the next chapter for deep-sea sheathing* — i.e., the same provision beinj^ made so that no torsion is given to the core. If one of the cores is to form a central heart round which the remainder are to be wound, it is passed singly through the hollow shaft. More usualh", however, the central core is replaced b)' a hempen strand of requisite thickness, according to the number and diameter of the cores in use. To completely fill up or "worm" the interstices remaining between the cores, a disc E, carrj'ing small bobbins of hemp yarn, is fixed to the hollow shaft in front of the stranding apparatus (Fig. 57). The cores unwinding from the bobbins A pass through the openings B in the disc (Fig. 58), and enter the lay plate I) side by side with the yarn, where all are stranded together. The so-formed multiple core next receives its serving of jute and D A. ..J^ tI^ 1 nil P 1^^^ f & mm Fic. 57. — Worming Machine for a Multiple-Conductor Cable. sheathing, according to specification, in the ordinary way, as described further on. Where Desirable : Advantages and Disadvantages. — Such cables are almost entirely confined to the purposes of heavy traffic to neighbour- ing important islands and continents,f or across rivers, when the extra heavy initial outlay is sufficientlj- warranted : for nowadays it is not thought by the best authorities that a number of conductors laid together inside a necessarily heavy and expensive single arinour sufficiently decreases the chance of total interruption io warrant the extra cost in insulated con- * In special cases, however, each core is first surrounded with jute, and the so-served cores are then laid up together in a similar manner. t Thus the old " Electric " Coinpany used to own cables of the multiple-core type ; and the cables under the auspices of H.M. Postal Telegraphs are at the present time almost exclusively of this description. • 2 E . . . ■ ■ . ■ ■ . 402 SUISMAKINE TELEGRAPHS. ductors and armour. It is, indeed, usually considered better to guard aj^ainst such a contingency, by laying separate (single-conductor) cables between the points and on entirely different routes as far as possible ; though multiple-cored cables are admissible in some cases where — owing to strong currents (as in certain rivers and in shallow and stormy seas), or to a shifting or very rough bottom — the cable in any case requires to be a very heavy one,* and where, therefore, the exigencies of traffic, if involv- ing more than one conductor, may just as weW be met by the several conductors being laid up together inside one such cable.f In all other instances it is better to provide the required number of lines Vic. 58. — Disc of Worming Machine. by laying separate single-conductor cables. The lighter cables are more fle.xible, easier to lay and repair ; and in case of one breaking, communi- cation is kept up by the others. * It should, however, be remarked that, for shallow water where strong currents prevail, the cable should, as a rule, be heavy specifically , rather than by bulk, the latter involving increased surface subject to the prevailing elements. + The relative merits of laying several separate ordinary cables, and of enclosing several insulated conductors in a single armour to do duty for the same purpose, was gone into at length at the Institution of Civil Engineers in i860, in the course of a paper, entitled " On the Maintenance and Durability of Submarine Cables in Shallow Water," by Mr W. H. Preece. This pioneer paper, together with the discussion thereon, may be strongly recommended for a close studv. MECHANICAL PROTKCTION AND STRENGTH. 403 Section 3. — Sheath 1 n(;. General Description of Ordinary Cable. — As has been previcxisly remarked, the type of submarine cable at present in vo^aie is practically the same (in its main characteristics) as that of the first ever laid * — i.e., a close iron-.sheathed cable, after the manner of an ordinary rope, of wires varyinjr from .07+ to about .400 inch in diameter,* and in number from ten to about thirty-six, § thus formin^^ a more or less flexible mail, according to depth and local conditions. * This is probalily the only instance of the sort in engineering practice. t Wires of as small a cliameter as .040 inch (No. 19 .S.W.Ci.) have on occasions been used, in which case they are generally covered with Manilla, unless for "torpedo calile" purposes. I No. 15 and 4/0 British legal standard wire (S.W.G.) respectively. In the Historical .Sections (Part I.) of this book, the gauge referred to was the usual gauge of the time — i.e., the 15irminj;ham wire gauge. However, since those days the standard gauge adopted by the Board of Trade — as a compromise of the various gauges in use -has been legalised for general use to meet the difiiculty. In the further text this gauge (see Appendix I. at end of this Part) has accordingly been assumed for up-to-date, non-historical, matter. In many instances the actual diameter of the wire in fractions of an inch has also been given. •^ This includes that form of cable whose outer serving consists of a number of three- wire strands, as used occasionally in heavy " shore ends.'' Twenty-four is a fair outside limit for an ordinary close-sheathed "deep-sea" type, :ind twelve about a minimum. The rec|uircments here are sutificient flexibility, qualified by an assurance that the wires shall not be dangerously small in section, either from a piercing or corrosion point of view, though as regards tensile strength, the smaller they are the greater will be the breaking strain per square inch as a rule. Actually, the number of wires adopted m:iy be said to depend on the relation existing between the outside diameter of the served core and the gauge of wire employed. In the "deep-sea" portion of the 1894 "Commercial"' .Atlantic cable there were twenty-four wires each of No. 15 S.W.G. (.072 inch) — the smallest type of wire used in any ordinary close-sheathod telegraph cable. It is doubtful whether wires of less diameter than this could be safely employed— not at any rate on a mud bottom, which (unlike sand) \ ery often acts chemically on iron — on the score of leaving too small a margin for reduction of strength by gradual rusting. Small wires, however, have the advantage of making up into an iibsolntcly close-sheathed complete arch cable without involving rigidity or springiness. jl The recent tendency towards heavy cores to give a high signalling speed (by machine transmission) introduces mechanical difficulties, inasmuch as it involves a greater number of iron wires in order to completely surround the serving, which means an increased weight. This necessitates stronger holding-back machinery for paying out. Though a cable of this description has its advantages as an investment, there is a limit to which this can be carried. Thus it appears that in the event of a Pacific cable being undertaken, it would not be advisable to attempt a high ( uiachine transmission) speed, such as would involve an extra heavy type of cable, the difficulties of laying and of recovery being already sufficient in view of the great depth to Ije dealt with. This is quite apart from cost or prospective traffic considerations. If, however, extremely heavy cores are to be the order of the day, it is probable that in the case of extreme depths 404 SUHMARINE TELKCKAI'IIS. In this the armour consists of iron wires laid helically on to the served core in a perfectly symmetrical form.* The iron serves a double purpose : it affords tensile strength and also resistance to abrasion. , Requirements for Different Conditions. — In dceij water + — for pur- poses of after-recovery — tensile strength, with a ^iven limit of weight, is the main consideration ; and here a com])arativel}' fine wire of mild Hes.semer steel, or homogeneous iron, is emploj'cd with a breaking strain represented by as much as 80 tons to the .square inch — or more.* In shallow water, however, a different set of conditions have to be considered. For instance, in the type of cable adopted for approaching the beach, the quantity of wire necessary to resist abrasion with rocks, and for giving the some return to the alternate hemp and iron type of cable will have to be resorted to — or preferably, perhaps, the taping of each wire may be adopted on an extended scale. * In a close-sheathed cable the diminution of diameter is prevented by the abutment of each iron wire against its neighbour, which, therefore, support each other laterally, after the manner of a complete arch or tube, so that the precious soft heart, or core, of the cable should urdergo practically no compression on this count as regards solid pressure — though not, of course, water-tight against fluid pressure, such as that of the ocean. Theoretically speaking, for purposes of tensile strength — so far as deep-water cables are concerned — the wires should be applied straight. By this plan, however, the wires would require careful binding, and the same result can be more effectually attained by a lay in the form of a heli.\, besides affording a greater facility for stretching in the event of a strain. t Where a cable is, as a rule, unmolested by rocks. I The Bessemer p'ocess consists in forcing air through molten iron, which takes off certain impurities and leaves only a given proportion of carbon. The difference between iron and steel is constituted by the difference in the proportion of carbon. Steel has a definite and very small proportion, such as best yields the strength sought for — less than that of wrought iron, though greater than that of cast iron. Homogeneous iron (Bessemer process) is not exactly steel, but it is very nearly as strong — combining, in fact, some of the malleability of wrought iron with, practically speaking, the same strength as steel. It is this which is almost invariably specified for the sheathing wires of quite deep-water types, for it secures practically as high a breaking strain as that of steel, but at a much lower price than if the latter were actually asked for. .'\nother advantage in the sheathing wires of an ordinary deep-sea cable being comjjosed of " homo " (homogeneous) iron rather than of absolute steel, exists in the fact that the former are less springy, ma'-ing up, therefore, a better cable for handling and all sub- sequent operations. The improvement in the manufacture of *: j, )t;eneous iron wire within recent years is something enormous, especially as regards tensile strength. A stress of quite 90, or even 100, tons per square inch can now be applied to this class of wire before it breaks : twenty-five years ago there was difficulty in obtaining iron wire which would stand 50 tons per square inch. In "drawing down "to a small diameter the tensile strength is considerably increased, though, in being rendered harder, the wire becomes more brittle texturally speaking. .MIX'IIANUAI, rUOTKCTION AND STUKN(;TII. 405 desired weight to avoid shifting under pressure from currents, etc., is such that an abundance of tensile strength is secured by wire testing at less than half, or even a third,* the above strength.f The same quality of iron is used for the sheathing wires of the " intermediate " type, as a rule. As it is usually a single-sheathed cable and there is altogether much less iron in it, the available strength is materially less than the shore end, and some- times less than the dcejj-sea type ; but this is of no importance for shallow in,. 59. — Marine (jrowlhs found on a Cal>li; Fault. water cables, as has already been explained. It is, indeed, in every way more advantageous to employ softer (annealed) wires of the commonest iron,;J as above, partly on account of steel or " homogeneous " iron wires * The breakinj,'' weight of the commonest iron rod is about 25 tons per square inch section. The breaking weigiit of drawn wires —especially if hard drawn— is very much ^'reater than any rolled or annealed iron. This, however, varies so much with the par- ticular quality that it would be absurd to attempt to give any rule or statement regarding its acttidl strength. + Moreover, the paying-out or picking-up machinery will often not bear a stress much above 50 tons, so that any breaking strength beyond that would be wasted. It should, however, be stated that it is usually acknowledged as an axiom in the present day that all the cable machinery connected with a telegraph ship should be capable of standing a strain at least double the stress which the strongest cable in vogue will bear. X Iron wire of a still commoner class is less annealed, and, therefore, rather harder. This is occasionally thought to be best suited for " shore-end " and " intermediate " types, 4o6 SUUMAkINK TKLKCIRAI'IIS. beinjf too spriiifjj' and ri^nd for liaiifllin^ and working' a bulk of wires of this number and section, as well as for economical reasons. Such wire, whilst bearing a strain up to about 30 tons, has an clontjation equivalent to as much as 18 per cent, of its length when stretched.* * It is usually known as extra-superior quality, and designated " best best" (B.B.). This wire is always carefully annealed, is very ductile, and, after galvanising, should stand several bends at the same point before breaking. Fk;. 60. — A Fine Specimen of Coral. The specific gravity of ordinary bar iron is about 7.8 If suspended vertically in water, a wire composed of the above should not break under its own weight until it is made to support a length of about 3.5 N.M. In practice, however, it is not prudent to load iron much beyond a quarter of its actual breaking strain. Where the wires are all applied with equal tension, the tensile strength of a completed cable being approximately under certain conditions, owing^ to its greater durability under water as regards abrasion or corrosive action, though more brittle. Sea-weed and vegetable matter arc known to corrode iron, more or less rapidly, owing to the iodine they contain. Thus, some shore deposits and marine growths (Figs. 59 and 60) are very injurious to the sheathing of a cable. * It may be here remarked that the greater the elongation, the less will be the tensile strength, and vice versA. In fact, in tempering iron, some of the tenacity is lost, which would naturally accrue to it when hard. MKCHANICAL I'ROTKCTION AND STRKNGTIT. 407 equal to the sum of the \vci<;hts which each individual sheathin^j wire is capable of supporting,* it will be evident that cables, with the above ordinary iron, should not be laid in depths exceeding about 1.5 N.M. It is for the above reason, therefore, that this class of wire is not employed for the deeper waters ; in fact, in extreme cases, well-tempererl steel is sometimes resorted to with a tensile strength equivalent to nearly 100 tons per square inch — or, at any rate, quite hard-drawn wire. The sheathing wires of all types of submarine cables are galvanised. This was so from the very beginning as regards comparatively shallow- water cables, though not in the case of the first Atlantic cable. It was thought at that time to be unnecessary for deep-water cables, on the jjlea that there was no scope for chemical action at the bed of the deep ocean. Moreover, a strong idea prevailed that galvanising tended to reduce the strength of a wire.f The object of galvanising is to preserve the iron wire from the oxidising influences of air and water — i.e., from rusting. The process of galvanising an iron, or steel, wire consists in coating it with a film of molten zinc* Zinc readily changing to oxide of zinc, when expo.sed to the air or water, a wire so treated becomes covered with a thin coating of oxide of zinc.§ This, in absorbing carbonic acid from the air, passes into basic carbonate, which tends to protect the metal from further chemical change. Zinc is electro-positive to iron. I'hus any result from the.se metals being in contact is at the expense of the zinc rather than of the iron. Should any imperfection, however, e.xist in the galvanisation, the iron here tends to corrode more rapidly than if ungalvanised. It is, therefore, of the utmost importance that the very purest zinc should be employed for galvanising iron or steel wires for the purpo.ses of a submarine telegraph cable. As a general rule, the iron wire (of various descriptions) is ordered at the * This approximation would not, however, be considered by many authorities to hold good where hemp cords are applied outside, it being contended that these add materially to the strength of a cable — to the extent of i ton very often — provided they are applied with a lay bearing such a proportion to thiit of the iron wires as accords with their relative elongation. + As a matter of fact it is now usually considered to have slightly the opposite effect. In softening the wire, it certainly renders it less brittle. X The wire is first cleaned with sulphuric acid, so as to free it from any grease, etc., which may be present. It is then passed through a bath of the molten zinc. ■^ Oxide of zinc is insoluble in water, which fact would in itself render it a preservative to the wire. 408 SUBMARINE TELKGKAPHS. ' cable factory ready galvanised. Messrs Henley have, however, been in the habit of galvanising (as well as annealing) the wire themselves.* The competition in the .supply of ordinary ungalvanised wire being infinitely keener than in galvani.sed wire, they are thus enabled to obtain it at a lower initial co.st. In our submarine cable, as usually constructed in the pre.sent day, there are many and various forms which the armour may suitably take, according to the depth and nature of the bottom. ' In a proposed submarine line between any given points particular types are invariably assigned to certain portions of the line. These types vary as regards the number and class of iron wires used ; and, again, as regards whether there is only a single sheath of iron or whether this (with an inter- mediate jute, or hemp, serving) is .-iupplemented again by an outer armour of larger wires. The latter type, in one form or another, is employed in shallow water, nearing shore. The character of the cable varies still further according to distances from shore, nature of bottom, strength of any prevailing current, presence, or otherwise, of ground icebergs, ice- floes, etc.f Just as for purposes of recovery, a cable for deep water should, first and foremo.st, be as light, and, at the same time, as strong as possible,* so al.so for purposes of efficient laying, the cable should, as a property or invest- ment, have the greatest possible weight§ within a given area in order to ensure sinkage into the irregularities of the bottom, at an angle not too obtuse with reference to the ship. No doubt, from the contractor's point of • * Indeed, in early days, Mr W. T. Henley was originally a wire-drawer in addition to a cable manufacturer. + Specially powerful gear would, in extreme cases, be necessary for bearing the strain of picking up such a cable. \ That is to say, it should be capable of resisting a tensile strain somewhat greater than that involved by the weight of the greatest length of cable, which might reasonably be in suspension during the course of repairs. Hence it is usually considered that the " modulus of tension " of a deep-sea cable intended for the deepest water ought to be such that it will sujiport at the very least 6 N.M. of itself in water. S This is apart from the fact that the cable should also be able to support the complete length between the ship and bottom, during paying out, without fracture. This naturally implies, on the other hand, that the lower the specific gravity the belter. However, such a cable as an investment can never be laid so efficiently — though more easily without accident. II From a certain standpoint — that of skin friction in passing through water the area should be limited as far as possible both from an eflficient laying and a successful recovery point of view. In the former case, friction tends to retard the rate of submersion and lengthen the angle, and in the latter to seriously increase the strain. MECHANICAL PROTECTION AND STRENGTH. 409 view, such a cable is more difficult to restrain in payint? out,* and involves iTKjre precautionary measures to adjust the amount of slack within the required bounds.! * As has been pointed out by Mr Thomas Gray, F.R.S.FJ., a cable is paid out too fast if it goes to the bottom quite slack. When a cable is laid at a uniform speed, on a level bottom, quite straight but without tension, it forms an inclined straight line towards the position of the bottom that it ultimately occupies. This is precisely the movement of a battalion in line changing; front. When laying a cable in a three-mile depth, it is calculated that with the ship steaming eight knots the length from the stern of the vessel to the spot where it touches the ground is over twenty-five miles, and that it takes a particular point in the cable more than two hours and a half to reach the bottom from the time that it first enters the water. + The difference between the speed of the ship and the rate of paying out gives the amount of slack. This varies in different cases between 3 and 12 per cent. Hut the mere paying out of sufficient slack is not a guarantee that the cable will always lie closely along the bottom, or be free from spans. Whilst it is being paid out, the portion between the surface of the water and the bottom of the sea lies along a straight line, the component of the weight at right angles to its length being supported by the frictional resistance to sinking in the water. After a little consideration it will be evident that the angle of immersion depends solely on the speed of the ship : hence in laying a cable on an irregular bottom it is of great importance that this speed should be sufficiently low. Tiiis may be illustrated very simply as follows :— Suppose a a (Fig. 61) to be the surface of the sea, b c the bottom, Fic. 61. and c c the straight line, then if a hill n, which is at any part steeper than the inclination of the cable, is passed over, the cable touches it at some point / before it touches the part immediately below / ,• and if the friction between the cable and the ground is sufficient, the cable will either break or be left in a long span ready to break at some future time. It is important to observe that the risk is in no way obviated by increasing the slack paid out, except in so far as the amount of sliding which the strength of the cable is able to produce at the points of contact with the ground may be thereby increased. The speed of the ship must therefore be so regulated that the angle of immersion is as great as the inclination of the steepest slope passed over. I'nder ordinary circumstances the angle of immersion varies between si.\ and nine degrees— ?>., quite a small amount, but still an amount which under unfavourable circumstance.s may make all the difference in the safe deposition of the cable from an owner's point of view. Thus, in practice, most telegraph engineers do not consider paying out an increased quantity of slack a good substitute for going slowly over the ground. Under all circum- stances the laying vessel should approach banks and ledges at quite a moderate rate. If a large quantity of slack is paid out after it is discovered that a bank has been passed, the slack comes out at the wrong place, and only results in dangerous kinks (when after- wards picked up) by the cable collecting in coils at the bottom. There is also the disad- 410 SUBMARINE TELEGRAPHS. The limitiiif^ feature to this weight is, of course, the absolute necessity of jjroviding that it shall be sufficiently light in proportion to its strength to permit of successful raising from the depth at which it is to be deposited — not essentially on the basis of a single bight recovery ; indeed, attempts are seldom seriously made to pick up an entire cable in a greater depth than about i,ooo fathoms. A cable laid in deep water, free from strong bottom current, should, unless under a strain, sink well into a soft bed of ooze, sand, or mud, which, in itself, acts as an actual pre.servative, unless some chemical agent is present which attacks the iron wires, and which indirectly decays the hemp or jute. The nature and depth of the bed has been known to alter in medium depths owing to the action of sub-surface currents in causing shifting banks and so forth. These currents, which tend sometimes to remove all the soft microscopic shell deposit* from the surface, leaving bare hard rock, are not supposed to occur, even to a small extent, at greater depths than 1,000 fathoms.f Where no such deposit can b2 found on the bottom, a strong current and hard bottom may be fairl>' assumed to e.xist, and should be provided for with a cable offering greater metallic surface for withstanding abrasion.* .' ' ,'■■._.-' ■ . ;. Again, stouter — and therefore more rigid— sheathing wires are a wise precaution for that part of a cable which has to be deposited in waters that the saw-fish, the sword-fish, or the shark, are known to especially favour. Types.— As a rule there are at least three tj'pes in any given length of cable. These are usually designated under the general terms " shore- end," " intermediate," and " deep - sea," or " main," cable, which latter, vantage of waste by a superabundance of slack. On the other hand, if laid too tight, a cable remains suspended between the peaks of submarine mountains exposed to fracture by its own weight. Where irregularities have to be contended with, the best plan is to make a very careful survey before setting out to lay a cable, and, after determining on the route, to carefully mark it off with buoys in the treacherous region, thereby obviating the necessity of going at a high speed in order to steer a particular course — i.e., thus ensuring the right route, currents and slow speed notwithstanding. Occasio lally, however, a high speed is necessary, in order to lay the entire cable before threatening weather becomes serious. In such instances extra attention must be paid to getting out the required slack. Unless the tanks are large, some risk is here run of a foul, or accident, during the operation. * This takes *he form of what is commonly described as a sand, mud, or ooze bottom. + This is the greatest depth at which they are at presei.L known of. + It should, however, be rcmirked thru currents of great strength are mainly confined to quite moderate depths, where an " intermediate " type of cable, sheathed with wires of comparatively large diameter, would in any case be furnished. MECHANICAL PROTECTION AND STRENGTH. 4II generally speaking, forms bj' far the greater proportion of tiie total length, and varies again in character according to the depth. To give a rough idea, the " shore end " is often used, say, for the first two miles (or less) from the beach in depths up to 35 fathoms, the "inter- mediate" into water up to something like 350 fathoms, and the "main" type for the remaining portion, changing in description according to the depths and conditions to be contended with. It should be remembered, however, that a cable may be built up from four, five, or even six types in all, where, in a great length, the var\'ing conditions are of a very wide character. In this case, the different types are very usually split up by the expressions "heavy" and "light" "intermediate" and "heavy" and "light" " deep-sea," such further designations being applied in each instance by way of distinction : or, again, each type may be numbered A, B, C, D, etc., or I, 2, 3, 4, etc., and such a plan is perhaps preferable, if only to obviate the apparent paradox, which sometimes occurs, of a " light deep- sea " cable being heavier in air (though lighter in water) than a " heavy deep-.sea " — being materially larger, in fact, though having a lower specific gravity. The " .shore-end " type .should have .sufficient iron in it to .succe.ssfuUy cope with the wearing action brought about by neighbouring rocks, anchors, fishing trawls, etc. ; and, within a given limit of area, .sufificientlj- heavy to prevent .shifting. Owing to the incessant movement of the .sea, due to wind and tidal influence setting up a continual .sawing motion on the bottom, shore-end cables have been occasionallj- made to ineet these requirements by a single sheathing of exceedingl)- stout wires. A type of this de- scription can, however, scarcely be recommended, for it involves the wires being .so stout that thej' become almost in the nature of rigid rods. Shore-end cables arc, therefore, more usuallj- constituted by a double .sheathing. This has many advantages. It is then generally arranged so as to be a case of merely re-.sheathing the deep-sea, or light intermediate, type (with a packing of compounded hemp betuccn), the inner sheathing wires being maintained of the .same gauge,* .such as does not undulj- compress the core, as is .sometimes the case with the single sheathing of stouter, rod-like, wire.s.f In very large shore ends the outer sheathing has sometimes been * By the I)..S. type running in tliis way right through, it can be conveniently used alone to form the beach cable to the hut in instances where no "intermediate" type is used. + In a double-sheathed type, in fact, the inner sheathing takes off the squeezing tendency of the outer sheathing, assuming th.at the wires are "keyed up," and not of the " open-jawed " type. 412 SUHMARINE TELEGRAPHS, composed of previously formed strands * — three wires laid up together — with a view to offering greater surface to withstand attrition, and in order to decrease the rigidity for so heavy a type. However, as a rule — even in such extreme cases — single solid wires with a very short helical lay are preferable, inasmuch as a greater weight is thereby secured in a smaller area.f * The above more particularly applies to multiple-core cables, where a certain bulk is, of necessity, involved, and where, owing to the nature of the bottom, a great quantity and weight of iron is entailed. This form of sheathing, in fact, combines a certain amount of flexibility with the above conditions. The cable laid at the mouth of the Seine in 1877, between Le Hoc and Fenedepie — where great banks of sand shift bodily during spring tides, and where, consequently, a light cable could never last — is an excellent example of this type. Manufactured by M. Menier at Paris-drenelle, it has lasted nearly twenty years without requiring any sort of repairs. Apparently, owing to its great weight, it has sunk deeply into the sand, so as to be below the layers which are periodically washed away by the sea. This cable (Fig. 62) consists of five separate cores laid up Kli;, 62. — Multiple-Conductor Cable with Stranded Outer-Sheathing. together. These are " wormed " with tanned jute, the whole being then externally served with jute, round which are spirally wound fifteen wires 5 millimetres (= .192 inch) in diameter (No. tt S.W.Ci.). Outside this inner sheathing is a second covering of jute (compounded), and over this again the outer sheathing, formed of eleven strands close ; fitting, each strand having three wires of 5 millimetres (.192 inch) diameter, previously laid up together, by an ordinary stranding machine. The methods of laying up such cables and the machinery employed is, of course, precisely the same as that described for others. The heart of " wormed '' cores (laid up as already described) is merely drawn through an ordinary sheathing machine— usually of the deejj-sea type — for the inner serving. After the next serving is applied, the whole is then drawn through a he.ivier sheathing machine for laying on the previously stranded wires. + .Shore ends of this type will be found fully describes ..nd illustrated later on in con- nection with the s;)ecification of the last ".\nglo" Atlantic cable (1894). Here the outer sheathing wires are laid up so " short ' that a photograph of the cable in section gives an idea of their being oval rather than ordinary circular wires, as they are actually. MECHANICAL I'ROTKCTION AND STRKNGTH. 413 The Post Office Department have naturally had a great deal of experi- ence in the direction of heavy shore-end types for multi])le-conductor cables in instances of rock)', anchor-ridden, and boisterous approaches and landing-places round about the various islands of the United Kingdom ; as well as across rivers, and in connection with coastguard lightships and lighthouse communication. They ha\e, indeed, made a special stud}' of the question regarding, the most suitable pattern : the result is that the shore-end type now adopted by this Department is invariably a very Iieavy, close, double-sheathed cable.* The "intermediate" type usually consists of a single sheathing of more or less ordinary iron, the wires being rather stouter than that of the main cable — in degree governed bj- the existing requirements as regards depth and nature of bed. Very occasionally, in special ca.ses of bad bottoms for some distance from shore, intermediate types have been composed by a deep-.sea type with an outer sheathing of wires rather larger than, but not so large as, that of the shore-end outer .sheathing. Testing the Iron Wire. When a stock of sheathing wire reaches the cable factory, each coil is first tested for weight and diameter, the latter being taken from the mean of two measurements, one in each direction. Should any coil be seriousl)- at variance with what it ought to be in these respect.s — the former relative to the length of course, and the latter to the specified gauge required — it is rejected. A proportion of 10, or sometimes 20, per cent, are then tested (a samjjle of about i fathom length being cu*^ off from each end of the coils) for tensile strength and elongation ; or for torsion, as the case ma)- be, according to the class of wire and type of cable it is intended for. Large, soft, iron wires are tested both for torsion and tensile strength ; but the tensional test is alone applied to small "homo" or steel wires. About 6 inches of this sample length is also set aside for te.sting the galvanising onl)'. In testing a wire for tensile strength — i.e., till it breaks — it is al.so, at the same time, tested for elongation ; or rather, a note is taken of the amount of elongation which has occurred before the breaking of the wire * F"or example, one of the P.O. types between England and Ireland is represented by a weight per N.M. of as mucli as 27 tons. This forms part of a seven-conductor system. Such a cable has a breaking strain of nearly 30 tons. There are several other very similar instances. ., Correspondingly, the lightest form of close iron-sheathed cable weighs usually about I ton per N.M. wet in air, and bears a 6-ton stress— or more. 414 SUiniARINK TELEGRAPHS. under the j^radually incrcasintj; stress, the ultimate amount of the latter being additionally lujted. The small "homo" (or steel) wires of great tensile strength intended for deep-water cables are tested for their breaking strain and corresponding elongation, the requirements of the case involving both these factors, especially the former. An elongation of 4 per cent, on the original total length is usually specified for, about 5 per cent, or so being about the ordinary elongation which they will stand before- breaking. A breaking strain, or modulus of fracture, represented by at least 80 tons per square inch, is very ordinarily required, anrl an equivalent of over 100 tons per square inch often secured.* This class of wire is not tested for torsion, as a rule, inasmuch as it is known that when a number of such wires are laid up (even closely) into cable form, the result is sure to be sufficiently flexible — more or less, i.e., directl)- in proportion to the number, and in- versely to the diameter, of the wires employed. The larger, ordinary for " best best ") iron wires are, on the other hand, tested for torsion. Representing a test of toughness and even quality, this is especially to the point here; as the type of cable it is employed in — mainly ".shore-end" and "intermediate" — is liable to experience a good deal of rough usuage generally,+ in which brittleness might prove a fatal source of trouble.* It is al.so important on the score of the great bulk of wires, tending to make the whole cable very rigid. The test is carried out in practice by noting the number of turns the wire will bear before breaking, the length of specimen being usually 6 inches. The largest type of wires em]>loyed in cables generally stands about si.x turns or twists in the ab()ve-menti(jned length, whilst those very ordinaril)' used to a " heavy intermediate " type bear .some twelve twists before breaking, the smaller wires taking a much larger number. The * The true breaking strain of the wire should, strictly speaking, be obtained by testing- the wire without its outer galvanising coat, which may be got rid of by dipping the sample in sulphuric or other acid ; or else, in working out the B..S. of the wire alone, an allowance of from .002 to .004 inch 'should be made for the thickness of the galvanising. Again, the reduced area of the wire at the fracture is sometimes taken for calculating the H.S. per scjuare inch, instead of the area of the full section elsewhere. However as it is uncertain that the former is ultimately any more accurate —the latter is usually adopted, or a mean between the two, as a basis for calculations. + Besides being more open to local damages, as already shewn. \ Common inalleable wrought iron— sometimes only rolled, not drawn — being so much less homogeneous, is more subject to brittleness than anything of the steel order. Besides the objection to brittle wire as above, there is also a strong objection from a cable manufacturer's point of view, owing to the increased number of stoppages thereby involved during the operation of sheathing. MECHANICAL PROTECTION AND STRENGTH. 4'5 tension test is also applied t(j these soft wires,* their elon^fation being often noted at the same time. This latter may amount to a nearly 30 per cent, increase on the original length, 18 per cent, being very commonly specified for.f We will now turn our attention to the machines used for carrying out these tests. There are many different forms of machines employed as regards both Flo. 63. — Wire-Testing Machine for Tension and Elongation. the tensional and torsional tests, and recent )cars have brought to light .several improved devices. * This test obviously also acts as a test of brittlencss, and it is in this way that it is additionally applied to the above class of wire use-ing the test, and afterwards to count the number of turns shown by the line. The length of wire for the torsion test is generally 6 inches. The heat developed in the wire during torsion is much less than that experienced during the elongation test ; work being done, in the former instance, only on the outside fibres of the metallic cylinder. For the same * This latter, however, would not usually come into use for testing such wires as are tested for tension in this connection. MliCHANU:AL I'kOTECTION AND STRENGTH. 419 reason the duration of the torsion test affects the result in a much less ciej:frce than in the case of elongation. Speaking generally, the better qualities of mild steel wire usually stand torsion much better than tension ; and, moreover, better than other classes. However, the latter require — for the types for which they are used — to be tested more for torsion. As the displacement of fibre in iron wire under torsion increases pro- portionally to the distance from the centre of the wire, the number of torsion turns which wires of similar quality but of different thickness can withstand should be in inverse proportion to their diameters. Another practical test which affords a very precise measure of ductility, is to count the number of times a wire can be bent backwards and forwards at right angles, on a cylinder of constant diameter. Unfortunately the test affects only a very short length of wire, which may be of different quality at a little distance from the actual ]Mint where the experiment is made. Test of Galvanising. — In order to test the galvanising, the wire is usually dipped four or five times successively, for a minute each time, in a saturated solution of sulphate of copper at 60 F". (with five times its own weight of water), the wire being wiped clean between each dip. Should the steel, or iron, be laid bare at any point by the coating of zinc being too thin — which is shewn by the copper depositing — the coil to which the specimen belongs is rejected on this count ; and if tnere be many such cases it may be found necessary to reject the entire batch. Another test of the galvanising — and one very generally adopted at cable factories — is to coil the specimen round a cylinder about ten or twelve times the diameter of the wire, and note whether the zinc coating flakes off. Should this occur, unmistakable evidence is afforded of in- efficient galvanising. It ought, moreover, to be seen that the galvanising is smooth and free from irregularities. References. — Mr Bucknall Smith's very complete book on wire* will be found, amongst other things, to give exhaustive information regarding the testing (as well as the manufacture) of iron wire, and the reader is referred thereto for further details on this subject. ; Data. — The Table on next page serves to give an idea of the present capa- bilities of some of the various classes of wire employed for the sheathing armour of submarine cables, besides indicating the tensional and torsional tests which it is now the custom to apply. * "A Tre.ilise upon Wire," by J. IJucknall Smith, C.E., published at the offices of En^neeriiiji. 4^0 SUHMARINE TKLEdRAlMlS. ResUI-TS or Tests on Specimens of Iron Wire used for S/teo'hing Qil'les, by Messrs Clark, Fordc and Taylor, < fween 1892 and iL3 34-6 35-6 32.8 14 .1.98 .201 .194 2039 2160 1920 16.7 20 .4 16.5 18 'S 29.6 31.9 29.0 30 .200 .204 .198 2435 2580 2220 20.2 24 • s — — — 36.0 39.0 32.8 30 .199 .203 .197 3225 , 2460 2040 17 21 12 17 25 10 33-2 35-3 3'-i 30 .202 .205 .197 2324 2550 2100 23 29 17 II 20 10 337 36-9 3>-7 No. 9 LS.W.C. WIRE. % 25 .144 .151 .141 I 143 1296 1065 1 17.91 21 16 23.3 26 20 31-2 34.3 29.4 40 ■145 •147 .142 II22 1298 1003 15.6 22 II 23.0, 26 1 20 30.3 34-1 27.1 40 .144 .147 .142 1102 1232 1007, 14-7 20 10 23.3 26 21 30.1 1 32.S 27.4 15 .144 •147 .142 1147 1272 1045 14.4 20 ii.S 23.7 28 21 21-3 33-5 28.2 '5 •143 •MS .142 1122 ' I3OI 1 1004 14.6 17 II 24.1 25 22 3'-o 35.7 27.1 \ ■ ■ ■■;■■ ■ ■ No. 13 L.S.W.C Wire. ' 25 .098 .100 .096 1454 1600 1360 6.8 8 6 _ _- — 93.5 105. 1 89.4 30 .098 .101 .095 1430 i6oo 1300 ] 7-9 8 5 — 92.0 96.7 78.5 30 .098 .101 .096 1404 i6co 1320 i 6.7 1 8 S — — 90.3 100.8 90.6 25 .099 .102 .096 1506 1640 1360 6.5 1 8 4 — — 94.8 107.8 91-3 30 .099 .101 .094 14781 1610 1390 6.3 7 4 i — 93.1 99-3 85.7 No. 14 L.S.W.G . wiRF. /:, ■ ^ 30 .083 .085 .081 1 1152 1280 1050 54 6 4 — 1 — — 104.9 "0-9 95.6 30 .083 .085 .081 1119 1240 1020 6.1 7 S ■ 1 — 101.9 107.4 1 90.6 30 .083 .085 .082 1 100 1300 1020 5-7 7 5 — ; — — 100.2 i 1 12.6 95-3 30 .083 .086 .081 1078 1180 1000 49 6 3 — J — — 98.2! 99.7 95-9 30 .0S3 .087 .081 1003 1060 950 4.8 6 3 — — — 91.3 99.0 86.5 mechanical i'kotection and strkngth. 42 1 Genkkal Particulars reciardino a Sheathed Cable. Routine.— After wci^hiiifj, gauj,Mng, and testing specimen pieces for tension, elongation, and torsion of a certain proportion of the coils of iron "ire, the coils arc then prepared for use in sheathing and made up in the proper form, ready for applying to the "closing" machine. Partial Failure of Galvanising — In quite the early days of submarine telegiaphy it was discovered that the process of galvanising failed to act as a complete preservative against corrosion of the iron wires. After a more or less short period of submergence under the sea, they were found to have rusted considerably, and to be so weakened that recovery became a hazard- ous, if not impossible, operation. Iron, even when galvanised, is acted upon by salt-water, especiallj- when resting on ground which contains soluble sulphides. Here even quite stout wires are corroded away in a very short time, the ends being sharpened to needle points. It is usually thought that the salt-water tends to decay the zinc coating in the galvanising, and, having effected this, the iron wire rapidly oxidi.se.s. Thus, whilst the insulation remains intact and perfect, the cable is liable to break at the first attempt to raise it. Another .sort of chemical action also causes deterioration in iron, giving a characteristic fibrous appearance to wires which have been under water for a long time. Failure of "Open-sheathed" Cables. — It was partly to meet these drawbacks that the type of cable adopted for the 1865 Atlantic came into vogue, and was employed for a number of undertakings in deep water. One of the features of this type was that of preserving each of the iron wires by previously encasing them in tarred hemp. Here, again, a cable of low specific gravity was obtained, whose tensile strength as a whole exceeded the combined strength of the iron and the hemp taken separately.* However, as has already been explained, this type of cable did not prove durable, and was eventually abandoned. The hemp being in close contact with the once rusted iron, rotted away sooner than ever, even when of the best class t — not to mention its immediate contact with any possible * This result is explained by remarking that the weak places in the wire and the surrounding hemp are probably seldom coincident, so that the strength of the covered v . wire the sum of the average strengths of the wire and the hemp ; whilst each of these ■_ substances, when separately put to the test, will give way at its weakest point, where the .. strength is always less than the average. t On exposing to sea- water a cable protected with wire so covered, the water, entering between the thread-;, attacks the metal ; and a rapid destruction of the hempen covering thereupon ensues. 422 SL'HMAKINK TKLPZGKAI'IIS. mineral or orj^anic matter on the ocean bed. Again, the iron wires not fitting together, any species of boring insect, or fish, can much more readily find its way through to the gutta-percha core* than is the case where the wires fit closely against one another. A cable so formed once losing its solidity — owing to the destruction of the hemp — a general decay rapidly .sets in, on the entry of the water all round the iron wires, and its recovery for repairs soon becomes practically impossible. Bright and Clark's Cable Compound. — The oxidising action of salt- water (and of air) on the zinc coating in the galvanised iron sheathing wires is nowadays to a great extent arrested by the application of what is known as Bright and Clark's bituminous compound, together with an outer binding, or bindings, of hemp, jute, or canvas tape, in a manner which will be gone into hereafter. The compound is incorporated with any of the above bindings, both outside the wires t and outside the entire cable, besides the materials being sometimes previously steeped therein. This .system is ba.sed on patents of the late Sir Charles Bright (Nos. 466 and 538 of 1862), an additional object of which was that of firmly adhering and binding the various coverings together. ij: The above preservative compound (first used on the Persian Gulf cable of 1863) is a mixture of asphalte, or mineral pitch, § silica, and tar. * There are several insects which have a pronounced penchant for hemp and jute, as well as for gutta-percha. t It is highly desirable that compound should be applied outside the sheathing — or preferably that each wire should be previously steeped in compound and also taped, if possible— as the outer compounding must go with the tape, yarns, or cords when they fail, which (except perhaps in the latter case) does not take long to occur. \ Previously, in 1858, .viessrs Clark, Hraithwaite, and I'reece had taken out a \ tent — ■of which Mr Latimer Clark was the main author — for applying a covering of heni,^ and asphalte as a preservative to the iron wires of a sheathed cable. The asphalte was to be applied whilst hot outside the finished cable, and was heated up by charcoal fires. This plan was tried on a short cable to the Isle of Man in 1859 ; but gave a good deal of trouble during manufacture, the insulation becoming seriously damaged by the process. No further use was ever made of this particular system of preservation. S Mineral pitch is the heavy residuum of coal tar, after various spirits have been drawn off. It may also be described as the solid variety, at a normal tenijierature, of artifici.-.l bitumen. Natural bitumen (or vci^etahlc pitch), from Trinidad and elsewhi re (formed as the heavy residuum from wood tar), is not usually turned to account in cable compounds. It has, however, been occasionally incorporated as the mollient in place of tar, being much clearer, finer, and softer than mineral pitch— having, in fact, more tar left in it and of the finer sort. Pitch — more particularly 7'ei:;etable pitch — is still occasionally termed by its original name, bitumen. It has, indeed, occasionally been spoken of as asphalte — or asphaltuni, originally. The latter, however, is distinctly unsuitable in the ])resent day, considering that the term is generally used to imply something very different. MECHANICAL PROTECTION WO STRENGTH. 423 In this concoction, it is the pitch which acts mainly as a more or less air-tight and waterproof preservative casing. The tar is incorporated princi- pally as a mollient — i.e., to make the pitch workable, the latter being, by itself, too stiff; just as the tar alone would be too thin and liable to run, or get washed away afterwards by the incessant action of the sea. Both, however, are similar in their characteristic preservative and waterproof quali- ties, the mixture being effected chiefly to obtain the required consistency. The silica — made from calcined flints ground down to a i)owder, similar to sand — was added to the above composition especially with the object of evading the ravages of the teredo by damaging its boring tool, which object there is evidence of it having successfully accomplished. It is now, how- ever, very often left out (owing to the difficulty of keeping it ])n)perly mixed with the rest),* though particularly to the point in shallow-water cables infested by marine " borers." It may be remarked that the actual proportions of this mi.xture are varied very much accc^rding to the requirements. Special compound cements are made u|j for different and particular i)urpo.se.s, the result of e.xperimcnt and c-xiierience ranging now over a number of years. However, all the cable compounds in use at the various factories are based on the above original mixture,t with the same — besides sometimes additional — constituents therein. ;J Again, in all, mineral pitch forms the base, or main constituent ; and the amount of tar added is comparatively small, as a rule, though in some instances it is largcr.§ The specific gravity (jf liright and Clark's compound varies, of course, according to the proportions. However, one cubic foot of the original composition weighs about 100 lbs. * This defect in practice is one which niii,flit suitably receive more attention in some of the cable factories. + Largely owing to the method of application (to be described later), this patent proved pjrhaps the most lucrative of any connected with subniarine telegraphy, yielding as much as /^3o,ooo to the inventor (Sir C. Bright) and his partner, Mr Latimer Clark. I Resin oil is now frequently incorporated in hot compounds. S As will be shewn hereafter, the tar employed is sometimes coal tar and sometimes Stockholm (wood) tar. The former, which is cheaper, is invariably employed in the case of hot compounds for the outer serving. lUit the latter, being of a lighter and finer con- sistency, is always adopted for the cold compound outside the sheathing wires, as it would not run at low temperatures with gas tar^in fact, here the amount of .Stockholm tar used has to be about the same (by bulk) as that of the pitch. This (cold) compound is trouble- some stuft'to deal witli, and would be quite unsuitalile for the outside serving, as it would not sink in readily, neither will it stick on like hot compound. However, hot compound could not be applied outside the sheathing when once "closed," for fear of damaging the insulation. The matter is usually obviated now by the more com|)lete preservative system of dipping each coil bodily into hot compound before it is applied to the served core. This matter is dealt with in subsequent pages. ^ 424 SUHMAKINE TKLEGRAPIKS. Compounding of each Wire. — Another device w ith a view to (wel- coming the deca)- of the sheathing armour was that described in a patent of the late Mr Willoughby Smith (No. 3,622 of 1878) for embedding the iron wires, in long open spirals, into an extra insulating coat outside the ordinary core, composed of a soft mixture of gutta-percha and shellac ; either the wires or the outer surface of the core being heated immediately before, by way of ensuring efficient embedment. This plan was presum- ably found to be difficult of proper effection ; for, it is believed, nothing was done with it in practice. It, however, no doubt served to lead the way to present-day jjractices. Thus, in 1880, the " Anglo" Atlantic cable of that year (manufactured by the Telegraph Construction Company) was close-sheathed with iron wires each of which had been previously coated with a mixture of refuse gutta- percha and Chatterton's compound. This method of preservation to each iron wire has been very commonly adopted ever since — indeed almost invariably except where each wire is surrounded with preservative tape (in a manner which will be explained hereafter) or even as a preliminary additional preparation. Nowadays — with the prices of cables so much cut down — the gutta-percha mixture is very commonly replaced by the ordinary bituminous preservative compound of Messrs Bright and Clark, just described. In order to effect the complete coating of each iron wire with the com- pound, each coil, after being tested on arrival, is first heated for an instant in an oven to effectually drive off any moisture. It is then dipped bodily into a bath, or tank, of the hot compound.* This plan very usually takes the ])lace of the coating of compound out- side the completed sheathing, thus rendering certain that the wire will be entirely covered with the mixture. When only applied externally, it probably never percolates to any extent through the interstices of the wires, and is confined, therefore, to the outside surface. There are those, however, who assert that this method of compounding each wire .separately (or that of enclosing it in a similarly compounded tape) has a tendency to effectually disguise the presence of faults brought about during the process of sheathing — due, say, to burning, or what not — by preventing water reaching until the cable is subjected to the pressure of the sea. The author has, however, never heard of any instance of trouble * Possibly on account of the nature of the operation, the term "pickling" has been sometimes applied to the above " dipping in compound " process. This, however, is liable to lead to confusion with the process of plunging iron wire Into acid, after being ilrawn, to cleanse it of all grease or other impurities on its surface previous to galvanising. MECHANICAL PROTECTION AND STRENGTH. 425 on this account. Again, it is asserted by certain electricians that the above phm — as well as that which is to follow — causes some inconvenience in reduc- injj the efficiency of the "earth," the sheathing wires always being made use of in a submarine cable for this purpose, as offering a ready and excellent form of electrical connection.* It has been pointed out that if the sheathing wires are separately coinj)oundcd in the manner described, they are no longer in direct metallic contact ; and, inasmuch as the compound is not only of a waterproof but also of an insulating nature, the earth connection must, perforce, become considerably less reliable and effective. Extreme variability in this respect has certainly been experienced with cables whose wires are separately compounded or taped, besides " kicks," etc., during testing and signalling operation.s. It would seem, however, as though such drawbacks must be either sub- mitted to, or overcome in some other way ; for the advantage of dipping each wire separately into compound—in the absence of taping each wire — is now so generally recognised as to be regarded as a sine quA non. Taping each Wire. — In 1870 a patent was taken out in the names of Messrs Matthew Gray and Frederick Hawkins, of Silvertown, for covering the sheathing wires of a cable separately with strips of woven cloth (made of cotton, flax, or other yi»rn) saturated with some form of bituminous (vegetable pitch) waterproof composition for purposes of protection and preservation. According to this patent the previ(5usly prepared tape was to be applied spirally to each wire before laying up, in " at least two coverings alternately in opposite directions." Whilst the inner taping was by preference to be composed of cotton, the outer was to be of Hessian canvas. In this original device the wires so lapped with tape, when laid up, completed the entire cable, and one of the incidental advantages claimed for it — in comparison with the previously prevailing open-sheathed type of cable — was the fact that a material diminution of the bulk was secured without reducing the breaking strain, whilst providing a more efficient and durable form of protection for the armour. This type was first made, on an extensive scale, by the Silvertown Company over the Post Office Wexford cable, more especially in connection with the shore-end types. Nowadays, this device, in a modified form, is turned to very general account with regard to deep-sea types. * Especially in a long length of laid cable, tlie surface exposed to the sea being, in that case, enormous. 426 SIJIIMAKINK ri;Ll,(;UAI'IIS. In present |)r;t(;ti(:e the outer covcriti^^ of <:()iii|)arativi;Iy thick Hessian ta|)e is replaced with a similar covcrin^^ of eottoii tape, laid on in the opposite direction ; or else — far mo;-;; [generally — it isapjilied sin^^ly, it hein^j commonly considered that with mon; than owr. lap of tape there would Ix! too ^Mcat a fiistancc between the wires, to meet the (|ualifications of a close- sheatlied cable, A^;ain, there are always other coverin^js oulsidi! the sheath of taped wires, wliich, in this modification, Ijiitt |»retty closely a^,'ainst one another. Indeed, in its |)ri'sent application the cabhr approaches more nearly to the close-sheathed cable of nioflcrn days, whereas the ori^jinal device may be iooki^rl upon as a species of the "gridiron" type. C'ables of this flescrijjtion have been made r)n an extensive scale — mainly, or characteristically, !>)' the Silvertown Company, for tiie last twenty years or more. A cable with taped wires may be re^oirded as sonu; sort of compromise between the absolute close-sheathed and open-armoured cables — or, more properly.as an e.xcellent mfjdificatioii of the absolute close-sheathed cable — combinin^^ in the main the ^nrat advanta^^es of the former with certain con- veniences and advaiita^'es in the latter. 'i'apini.( each iron wire has the effect of n.-diiciuK the resiliency of an orrlinary close armoiir inaUin;^ it more flexible, in fact, whilst renderin},' it less spriii[^y and rij.;id. it is, therefore, more |)liable for handling' durinj,' contractors' o|)erations, an'l is less liable to kink -/>., to throw itself into a loop when leaving.,' the hold of the vessel in which it is coiled -or to any other si>ccies of accident during layin^j. It is also claimed for the taped-vvire principle, that a cable s(j constructed is more durable than with the orflinary close sheathing, on account of the blotter protection of (.-ach wire by the prepared tape closely envelo]>int4 it,* which latter is suppo.sed to be more or less water- proof. This feature renders a taped-wire cable well adapted for corrosive bottoms.! Where the sheathing wires arc taped, thir specific fjravity of th( cable I;:, moreovi-r, appntciably rerluced. This type is, th(;refore, peculiarly suitcfj for extremely deej) water — where the exi^jcncies of recovery become a * Thus if only (in this iiidnini niiitcri.illy liicreiiHinK llii: < liiim cs ol siirrcHsful recovery ;ifti;r years of siihnuMsion. It niay l>e suxKcsteii thiit llic wires of grapnel and hiioy ropes should also he treated in like manner, besiost destructive to steel wire as to iron chains. t riic last is a strong; tcature, inasmuch as it is often not lon^ before iliu outside cuvcrinK rots away especially if only ctanposed of tape or yarns. MKCIIANK AI, I'KOTI'CIION AND srKKN'JTM. 427 serious coiisidciatioii hy rciidcriii^j tli(; cahk! (.;i|);il)l(; of siis|)(MKliii(^f a ^jri-alcr l(;i)^{tli of ilsclfii) watt.'r.* On tlic otiicr liaiid, il is also coiilciidcd that the decrease in specific (gravity arul increase of skin frictir)n here entailed, is not sufficient to seriously alter the anj^U; in payin^^ out in such a way as would prevent the cable adapting,' itself to the irregularities of the l)ottom.+ VVh(;re tlut slii-alhin^; wires of a cable are to be individually "taped," the coils are not (.(enerally tlipped bodily iMt(j preservative ctjmpound, as previously tlescribed. * However, in the operation of applying' the silicated preparefl tape to the wire, the latter in bein^' drawn off from the iron bobbin on to which it has been coiled, is Hrsl led throu^di a tank of hot compound, on its way to the taping,' apparatus, immediately previous to the apjilication of the tape. This ojjeration is performed by spinnirij^ roimd the wire a bobbin or disc,§ loaded with the pre|)arcr| tii|)e. The speed of firaw off in relation to that * Tlif fill I that till- I ocfficii-nt of frii lion is slij,'l)tiy iii^ (locn not usually apply Ih'k- as iiiiicli as the advaiita^jr of (l(!i rcfasi.-d spci ifi<' gravity ; lliou^li it would it prcrsscd fiiriiiur, uiili!ss tiu; spci-d of pi(|{inji<'iit it must also lie renieiuliercd thai loo uiui li slai l< woiiM lie .IS l)ad as too little, if introducing lengths of c.'il)le (oiled down at iIk; hottoni. 'I'Ik; latter, when lifted, wn: liable to involve kinks sui li as hreak und<;r any romiderahle slr;iin. [ Nevertheless, owinj^ to the very perfect prestMvalion hy the dippin;,' in ( onipound, pre( cded hy Ix'atiuj^, this proi ess f(»rms it most littin;' picliminary in ;iiiy rase. ily this UKMhod, .ill moisture or moist matter liein^ driven off, ihe ((impound, a|)plieil at an i'\cfi'ilitti;/y hi^li teniperaiure, adheres almost ;is firmly as a varnish. J5 The disc here is mounted li(;iween two metal plates, which serve to keep the tape in its place. il The material is usually piepired hy Ikmuj; led lh|■ou^,'h a tank of hot prescrv.itive (cable) compound Iroin its roll whilst in slurct form. In (ominx away from the ((impound tank il is drawn through a lathe wlxrre it is cut in strips to the required width, and then wound on to the discs here alluded to. The abovi; is the Silvertown plan, ac( (irdln)^ to the (iray and Hawkins patent. Mcssrii Johnson and I'hillips, however, patented a devi( c in 1H76 ^\o. 3,533) for cutting the t.ijie direct whilst on the se( (ind (wdoden^ sjiindle, aflei passiii)^ lhroii)/h a ( oinpouiid bath. Ily this plan, the sjiindlc itself w.is also (tit rii^lit through into thin discs or spools, which are ready for fitting,' to the wire-t.ipinn ma(.hine or to the calile machine, as Ihe case may be, with the tape of the r principlef — t.e., of the axis of each bobbin, during the revolutions of the carriage, remaining perpendicular to the plane of the earth and to one another, with the above object.* In early days the sheathing machines used to be — like most small (conductor) wire-stranding machines — of the vertical type, as was the * Patents for somewhat similar devices were also obtained later by Mr W. T. Henley, Monsieur F. M. Baudoin, and others. + The principle adopted in sheathing machines may also be likened to the " feather- edge " principle of paddles in a paddle-steamer. \ The method of effecting this is based on very simple geometrical considerations. .Suppose a circumference (Fig. 68) turning on an axis passing through the centre A, and a second circumference of equal radius having its centre H on a line drawn vertically through A. Again, suppose the two circumferences to be connected by a series of rigid rods parallel to the line A is, and to one another. If the second circumference is capable of no other movement than that of rotation on its centre, it is evident that the rods will all retain their relative initial positions. The one extremity M of any rod M N, being brought to a point M by the rotation of the circumference .\, the other extremity of the rod can only occupy one of two positions, n and «i — the points of intersection of an arc of a circle described about the centre in with radius equal to M N, with the circumference li. Now w // is parallel to M N ; for if we move the second circum- ference along the common diameter I! in so as to bring its centre over the point A, it will exactly coincide with the first circumference, and all its points will have moved through equal distances in parallel lines. More- over, /// n is the only possible position for the rod .M N to take up, for the points n and «i being symmetrically placed with regard to the line u w, it would be impos- sible to pass suddenly from one position to the other ; unless, indeed, the rod M N happened to be in the position ?n 7', and to be the only one. The simul- taneous presence of several rods obliges them all to retain their original parallelism. In furtlier explanation, it may be added that the second circumference is compelled to move with the same angular velocity as the first, by the rods, half of which are in tension and the other half in compression ; the turning effect being greatest at the sides and decreasing to nothing at the top and bottom. They are, in fact, " coupling-rods," which can have no other direction than one parallel to the line joining the centre of the two circles. , . Kic. 68. — Principle of Machine for Laying up Wires without Twist : (jeomelric Demonslration. MECHANICAL I'R(JTECTION AND STRENGTH. 433 case with roijc-makiiij^ machines of tliat period. These were, however, replaced after a time by horizontal machines, the first of this class bein^ used over the manufacture of the Persian Gulf cable of 1863 at the works of Mr W. T. Henley. This form has been adhered to ever since. Thou|;h the vertical machine naturally occupied less floor space on the same level, it involved cither a materially greater diameter to carry all the bobbins or el.se a number of platforms to enable it to be attended to at various points ; thus, also, requiring, in consequence, a larger number of hands to look after it. With the horizontal form, moreover, a higher working speed is possible, owing to being on one common foundation, with greater stability in consequence ; as well as — partly for reasons of centrifugal force — on account of the smaller diameter, by various sets of bobbins being placed one behind the other. Again, in the early machines (of Newall, etc.) the revolving carriage to hold the bobbins took the form of large di.scs of great weight. The speed at which it was safe to " run " such a machine was closely limited by principles of centrifugal force, varying, of course, with the outer circumference of the disc and the weight of loading. The.se have, therefore, been gradually replaced at most of the cable factories by machines * whose carriage consists of a long aiid comparatively light framework — at any rate as regards those intended for the construction of cables with a light type of sheathing wire, where a high speed of sheathing may be safely and usefully adopted. For laying up very heavy wires, the old disc carriage machine is still sometimes adhered to.-f- Here, notions of speed have in any ca.se to give way to strength, without the chance of an uneven strain being placed on any part of the machine. It may also be mentioned incidentally that in the class of wire here involved the breaks are of somewhat frequent occurrence, and, therefore, attempts at a high rate would be unsuitable — not to say wasted. Moreover, the speed advisable with any machine is more closely limited in this case. Again, there is not here the same call for a high speed of running, owing to the length required of heavy type cables being much le.ss, as a rule. With either class of machines the bobbins are always "geared " on the .sun-and-planet principle already alluded to. In the case of a double-sheathed cable — such as a shore-end, and some- * Such as can be safely caused to revolve at a much higher rate under the dififerent set of conditions generally prevailing. + It is improbable, however, that any new machines, even for heavy wires, would be made on this principle. . 434 • SUIl>rAKINI': TKLKGKAPIIS. times intermediate, type — tiie second sheathing is performed by the cable bein^ run through a larger machine suited for loarlin^ with the iieav)- class of wires constituting; the outer sheath. Machinkry. We will first proceed to describe the j^eneral principle and working' of that form (jf sheathing machine which is in most common use in the modern practice of cable construction, especially — and characteristically — in con- nection with the manufacture of cables of a li^ht type. The Skeleton-Cylinder Machine.* — -In this machine — a i^eneral view of which is shewn in Fig. 69 — the three frame wheels A, n, c (Fig. 70) are Ri o Fig. 71.— Skeleton-Cylinder Cable Machine ; End View. keyed on to the hollow shaft and turn with it. Round the circumference of the front wheel A are fitted sixteen cranks ;;/ (Fig. 71) of equal length, which couple to a large ring F G, the diameter of which is equal to that of A; the centre of the ring is in the same vertical line as the centre of A, and the ring is kept in position by the two adjustable rollers D l). Sixteen rect- angular horizontal iron frames H are placed, half between the wheels A and B, and half between B and c. These frames are pivoted longitudinally at * Known sometimes also as a skeleton-frame, or cylinder-cage, machine. [I'LATK XIX. Kii;. 69.— Deep-Sea Sheathing ov "Closing" Machine. ■y my Flu. 70. — Cable Sheathing Machine : Skeleton-Cylinder Pattern. MECHANICAL PROTECTION AND STRENGTH. 435 either ci".d by horizontal rods, the front ends of which are secured to the crani< heads in the front wheel A (Fig. 72). These frames carry the reels of wire K,* the s])indles of which are horizontal, and revolve in grooves cut in the upper faces of the frames. The spindle ends j (Fig. 73) are kept in place by |)lates of iron M secured to the frame by two butterfly nuts, or by hinge and bolt. Routine. — When a bobbin of wire is entirely wound off, the ]jlate M is removed, the empty bobbin replaced by a full t)ne, with the help of a crane, and the ends of the wire jointed together. With the large, soft, iron wires, this joint partakes of the nature of a weld.f no solder being used, but sal-ammoniac, or sand, as a flux, for cleansing purposes only. The small "homo" and steel wires arc, however, jointed together by "brazing," i.e., a hard metal like brass being used as a reliable solder, where great heat is necessarily involved as in welding hard iron or steel. Within recent years the joints in both classes of wire have been very succcssfull}' effected by the process of electric welding. Here, the weld should be absolutely pure, being free from sulphur, coal, dust, etc., and should, therefore, in this sense, be superior to— and more durable than— an)- ordinary forge weld, on account Fio. 72. Fic. 73. of the greater homogeneity at the joint thereby implied, with equally quick, and usually quicker, effection.* * The number of these \aiy very much accoichiiK to the type of cable, the machine hem^i fitted accordinjily. However, the averaj^e number of wires for a single sheathing of deep-sea type is about fourteen each from a separate bobbin. t It is sometimes actually specified that all the joints in the iron wire are to be lierformed by welds. This is partly as a safeguard against pronounced scarfing, which entails skilled workmen and sharp edges such as migiu (in breaking) damage the core. However, it woukl scarcely be to the contractor's interest to attempt proper scarf-joints in the sheathing wires. I Electric welds in iron wire can scarcely fail to be preferable to a f>raze, which latter must always tend to introduce chemical action when submerged in salt-water. 436 SUBMARINE TELEGRAPHS. This system of welding electrically is now universally adopted by the Telegraph Construction Company, as well as by Messrs Siemens lirothers, in the operation of sheathing cables. There are those, however, who still prefer the old forge method for \ariors reasons. These joints in the wires necessitate stojiping the machine whenever a bobbin has to be changed. The length of wire which each drum or bobbin holds, varies considerably with the class of machine {i.e., weight and size of bobbin) and the t)'pe of wire. In any case, however, the stoppages are fairly frequent ; for, in the first place, arrangements are, as a matter of course, made so that no wire terminates at the same point,* in order to avoid the position of joints in the various wires coinciding.t A small spring brake cl (Fig. 74) presses against the frame or spindle of each bobbin, thus restraining its motion and causing the wire to unwind with the requisite am.ount of tension. The bobbins arc made to always remain in the same Kic. 74. horizontal plane (so as to ensure, as already described, an absence of twist in the wire during " laying up ") by the carriage in which each rests being allowed to work freely in the general framework, during the revolutions of the machine. * It is very often stipulated in specifications that no two joints in the ilitiferent wires are to come within 12 feet of each other. t Moreover, a break sometimes occurs in a wire — at a joint, perhaps, after "laying up." This more particularly applies to the large iron wires owing to their lower breaking strain per square inch, and to their greater brittlcness — so far as standing bending about is concerned. In such a case, where a fresh joint is impracticable, the entire sheathing has to be bound round here with binding wire (about No. 15 gauge) and spun yarn. In some of the early cables of the "open-sheathed" type, a yarn "whi])ping" was applied along the entire length in the form of a long spiral just sufficient to prevent the projection of any broken wire such as would tend to catch into the next turn or lower flake, or into the machinery, during paying out. This was found to meet the necessities of the case very effectually. In 1869 Mr V. C. Webb took out a patent (No. 3,489) for a metal tube, more especially to obviate the piercing of the core by broken sheathing wires. This metal tube (steel for deep-sea cables, to bear any material strain ; iron or copper for shallow- water) was to be applied as a riband outside the jute or hemp serving. After receiving an external covering of tarred yarn, and the usual sheathing wires, the cable was completed. The principal feature of interest in this patent was, however, the ingenious method of putting it into effect. MECHANICAL PROTECTION AND STRENUTII. 43; On leaving the bobbin, the wire passes over a small ^uide pulley «, and on through the hollow pivoting rods to the " laying up" dies. To avoid overloading the hollow shaft E E (Fig. 75), the weight of the two wheels H and C is taken by two pairs of rollers ^^. As there is much wear between the wheels and rollers, the spindles of the latter are pivot-^d in a fork frame /(Fig. 76) worked in or out by a screw h, and the rollers, by this means, are kept up to their work. The roller on the side towards ^Mjl^ Kk;. 75. Kic. 76. which the lower half of the wheel is moving usually wears away much more quickly than the other. The actual "laying up" of the wires round the core naturally takes place at the further end of the machine, which we will now turn our attention to. The end of the hollow shaft E E (Fig. 75) is supported by a plumber block L. Just in front of the plumber block is keyed to the shaft a tootiied wheel N, pierced with holes through which the several wires are led. Connected to this wheel, by three rods, is a ring o (Fig. yy^ which surrounds the wires and forces them into parallelism with the shaft. On coming tlirough the holes in the wheel N, the wires pass along longitudinal grooves cut in the body of the hollow shaft where it passes through the plumber block L. A hollow cone piece P (Fig. 78) is fixed to the end of the hollow shaft E by three rods or brackets /; (Fig. 78) ; inside this fits tiglitly another solid cone (j (I'ig. 79), secured by a set screw e, and having si)iral grooves cut in its outer surface The wires, in passing through these grooves, adapt themselves to the spiral form they have afterwards to assume, and unite round the core at the point R, where a jet of water keeps everything cool and moist. IMG. 77. 43« SUBNIAKINK TKLEdUAI'HS. The die block S, throiit^h whicli the cable passes immefliatcly bchiiul the point K, serves to force the wires into their places and keeps them close fitting. Sometimes it is simply an iron collar like the one in the serving machine of the same diameter as the cable, and in two halves bolted toj^ether with india-rubber cushions between. At other times, the die consists of four discs, or narrow rollers, placed crosswaj's round the Fid. 78. Fig. 70. cable (Fig. 80); the rollers can be adjusted to the diameter of the cable. Again, sometimes it is formed of two horizontal rollers, one above the other, both having semicircular grooves (Fig. 81) : the s|)indle of the upper roller works between vertical slides, and is kept pressed down on the iT>ller beneath, by a powerful spring. Tic. 8c. Vh.. 81. On leaving the die, the cable takes three turns round a large drum T (Fig. 82), which obtains its rotary motion from the hollow shaft K, as we shall .see further on, and which regulates the travel of the cable through the whole train of machinery—acting, in fact, as an intermeoiary "draw-off." It is on this drum, moreover, that the length of cable, as manufactured, is usually measured by means of a clockwork revolution indicator geared to, MECHANICAL I'ROTKCTION AND STRF:N(;TII. 439 and controlled by, its shaft. A piece of hardened steel r — which, being edt,^e-shaped, is called the " knife " — bears aj^ainst one (jf the flanges of the drum on the inside, constantly forcing the turns outwards as they Fic. 82. — Inlermeiliatc Draw-dtlaml Mtasuriny; Druiii. come on, and so making room for the next. The pulley V — al.so turned by the machinery — compresses the second turn against the drum with a force which can be regu- lated by slightly displacing one end of the spindle by means of the screw q. The control of the various parts of the machme is effected by means of the wheel N (see I-'ig. 75), and also by two other toothed wheels X and V on the hollow shaft E K, which are situated between two bearing brackets (Fig. 83) near the wheel F G (see Fig. 70). The bevelled cog wheel X (Fig. 84) engages the cone w, the spindle of which, at right angles to the shaft E, carries two pulleys ; the one marked « being keyed, and the other 440 SUli.MARINK TKLKC.KAI'IIS. li being loose. The belt which drives the ])iilley , the s|Mndle of which is rotated by a lever r, connected to the batten 5' (see Fig. 71); the lever tro- is pivoted at . The compound,* contained in a double-bottomed trough D, is raised by the third cylinder c parallel to, and in contact with li. Steam circulates inside the hollow rollers and the double bottom of the trough, to heat them and prevent the compound solidifying. The compound is pressed into the fibres of the canvas whilst the latter is passing between the rollers, and all excess falls back int(j the trough. The sheet of canvas when cold is rolled up on itself and cut into strips of the required width — usually from li to 2 inches — by a circular saw, or knife. Subsequently (in 1876) Messrs Johnson and Phillips patented a plan for Flc. 104. — Machine for Preparing Canvas Tape, saving the operation of windin\; from the spindle — on which the cloth has been cut — on to bobbins. Thi,. consists in the roller, composed of wood, being cut right through with the tape into the form of discs convertible into a sort of reel (called a " tape-head ") by having plates fitted to each side and a spindle run through them. This plan has been already alluded to with reference to the individual taping of each iron wire.f * Sometimes instead of Hright and Clark's compound, merely tar has been used — usually Stockholm (vegetable) tar. A^'ain, at other times ciuite difi'crent mixtures have been employed. In the 1880 '' An^lo" .Vtlantic, the outside covering of canvas strip was previously impregnated with " stearine," />., ozokerite compound. t The preparation of the cotton tape for each iron wire, and the canvas tape for out- side the entire cable, are performed at most factories in precisely the same way, whatever the method be. 460 SUBMAKINK TIXEGKAl'HS. Messrs Johnson and Phillips have been in the habit of supplying to the Telegraph Construction Company (for use in their cables) large quantities of canvas tape, so prepared, on disc bobbins — ready for ai^plication to tlie cable-making machine. The manner in which the canvas tape is applied round the sheathing immediately' after the cold compound has been applied (if there be any) is shewn by Fig. 105. The end of the compounded strip is drawn from its reel (; into the hollow shaft or tube A B, supported by two standards I', and having a longitudinal opening /;/ at the opposite end, about a foot long and 2 or 3 inches in width. The shaft is rotated by driving a belt on the pulley .'^, to Fig. 105. — Method of Applying Canvas Tape. which two other pulleys .s' and .s" of different diameters are sometimes joined, so as to vary the speed by placing the belt on one or other of the pulleys. To the hollow shaft is fi.xed a collar C with two arms, one of which, D, has a counterpoise K, and the other, V, carries the " head " c. on which the tape is wound. The tape-head is secured by a bolt and thumb screw II to a quadrant I, pivoted at F, and adjusted to the required angle by a bolt and nut at I. This bolt works in a slot in the bent bar K, which is itself fi.xed to the upright arm C F. The strip of canvas L enters the hollow tube through the opening at >//, and, carried round by the rotation of the shaft and reel, winds on the cable, which at the same time is being drawn steadily forward through the shaft. Under the combined effect of the two movements the strip is laid round the cable in spiral turns.* * The tape-heads hold on the average about a mile at a time. When this is exhausted a freshly charged " head" is fitted to the machine, the end of the new tape being united to th end of the tape already on the cable by means of ordinary cable compound. MECHANICAL PKOTKCTION AND STRKNGTII. 461 The requisite tension of the strip L is given by means of a small brake attached to the reel (l. To regulate the length of lay the angle of the lead at l" is set as required.* This naturally varies with the width of tape adojited where there is no overlap. At different factories different widths of ta])c are used, varying from I to 2 inches. The length of lay of the tajje varies correspondingl)-. When, as is usually the case, a second taping follows this in the reverse direction, it is not the custom to apply the tape with any overlap, the two edges of each lap being made to fit against one another. Hy this arrange- ment, practically s|)eaking, a perfectly even surface is procured, besides the coiling space involved being reduced to a minimum. Bright and Clark's Hot Compound. — A second coating of Bright and Clark's compound is now applied hot over the compound or tarred canvas tape, after the latter has been wrapped round the cable and in the manner just described. In this ca.se it is a hot compound that is used, there being practically no risk — especially by this method (jf application — of the insulation being damaged where a bad conductor of heat, such as jute or hemp, intervenes. For purposes of firmly sticking the tapes or yarns together, cold compound would still always be better, but this is not of so much vital importance as in the instance of adhering the first layer to the iron sheathing. Moreover, cold compound being such troublesome material to deal with, its use is always avoided where possible — especially as when hot the compound is much cleaner. The molten mixtu'"': is contained in the tank A (Fig. 106), the double bottom of which (not clearly shewn) is heated by steam from the pipe Q. As in the previcnisly mentioned apparatus for applying cold compound, the method of application here given is that of a chain elevator. The fluid compound is raised by an endless chain of thick links moving round the pulleys C and D. Most of the compound so lifted falls from the pulley C on to the inclined .shoot i:, and so on to the cable.f * The length of lay is also, very commonly, controlled by the revolutionary speed of the tape-head. The speed of "draw-ofif" cannot be adjusted for this purpose, as this has to be regulated according to the requirements of the lay of the iron wires, which again depends on their number. t It will be seen that in this machine the chain is made to run in a diagonal direction instead of upright as in that for api)lying the cold compound. By this means, besides serving as a distin • ion, the less adhesive and heavier compound is less liable to inadver- icntly tumble off as it is drawn up from the tank. 2 I 4^3 SUBMAKINK TELEGRAPHS. When, for any reason, the cablini^ machine recjuires to be stopijed, the workman who is attending to the compounding of the cable draws aside the inclined shoot by means of the le.er L, so that the hot comixnmd falls clear of the cable — and is, in fact, diverted into the tank again — thus avoiding heat- ing it up at one spot during sto|ipage.* The revolving chain is, however, kept running continuously (throughout all stoppages) to prevent the compound forming solid blocks around the links and the upper pulley, such as would tend to choke the apparatus on re-starting.- On resuming "cabling" operations the compound "shoot" is again drawn over the line of cable.f By way of regulating the thickness of the coating of compound a man is commonly stationed just beyond the compound tanks with a pair of tongs Fk;. io6. — Hot Comiraunding Apparatus. (Fig. 107), through which the cable is made to pass, and which therefore act as a die. These tongs require to be heated over a furnace from time to time in order to be effective in this way ; and it has been found that, on their applica- tion to the cable, they are occasionally liable to overheat it. To obviate this ■* Moreover, if the stoppage is likely to last any length of time, it is very usual to cover up that part of the cable immediately over the compound tank — by means of a half- tubing of rubber, for instance, or by some other bad heat conductor. Failing this, it would be necessary to temporarily shut otTthe steam in the compound tank. + Tiie disc form of elevator, previously described, is also sometimes here employed. It is, however, less suited for hot compounds, which, owing to their greater consistency, require to be more continuously and thoroughly agitated. Moreover, the chain is usually found lo draw the thick compound up better. MECHANICAL I'ROTKCTION AND STRENGTH. 463 objection, and to more thoroughly and completely round off the surface of the compound,* at the Silvertown Works a superheated scraping die is put into gear with the rest of the compounding apparatus. This apparatus, introduced by Mr F. Hawkins some ten years ago, is .shewn at P in Fig. 108. The die is formed in two halves, each half being steam-jacketed in connection with a flexible steam-pipe. The two parts may be drawn close «»»»'""» iiMiiiiiiwiMiiimTHl Kli;. 107.— Hand Compound Die. up to one another, or may be drawn apart from each other. To the back half is attached the trough or shoot, which catches the compound from the chain. The two halves are connected by levers as shewn, and in their normal position are kept apart by means of a weight on one of the levers. The levers are connected by a rope which is led overhead to the man whose 0@0k \S^ \ c.«» %T ^1 %. ftr — 1 \ .. \ !■■ \ / \l \ 1 '■ . II \l '- .1 "• / 1 -•' 1 '■ :.-==.r:....J Side Elavation £„j Elevation Vic. 108.— Superheated Die fitted to Compounding Apparatus. . duty it is to attend to this part of the cable machine. When the machine is started, the man pulls on the rope, which action— by lifting the weight- brings the two halves of the die together and the compound flows on to the * One of the features of Bright and Clark's cable compound is that of imbuing the completed cable with a smooth exterior, thereby reducing the coefficient of friction in picking-up operations. This is especially to the point in the case of a rough heinp- covered cable, and still more if it havcan outer casing of hemp cords. _ — ,^-..,-- 464 SUHMARINK TKI.KCRAI'IIS. cable, ail)' superfluity being readily taken off by the steam-heated die. On tlic machine stop|Mn^, tlie man lets go the rope and the die separates. The superfluous compound which has not passed the die is then pulled back by hand (previousl)' dipped in water) whilst the c()m|)<)U id is still hot. This apparatus is applicable whenever the cable is covered with hot compound — i.e., in every case except where the bare sheathing is uppermost. Second Outer Taping.- The second covering of tape is applied in a similar manner and withinit overlap, but wound on in a reverse direction to the first taping. Final Coat of Hot Compound. — Following the above again comes a third coating of Hright and Clark's compound laid on hot in precisely the same way as the last coat. Details of Compounding Apparatus. — To obtain continuous rotation of the chains in the different compound tanks (for reasons already explained), ^ |iiiiii j.ii ' ?"i(;. 109. the wheels o, O,, O., (Fig. 109) on the axles of the chain pulleys li, t', C,, all receive motion from the wheel K driven by a belt from the main shafting. Cooling the Cable. — Immediately after receiving the last coat of com- pound, the cable passes under a long pi])c pierced with small holes, through which water is made to issue in fine streams for the purpose of cooling the hot compound, so as to prevent it injuriously affecting the core. This is .shewn in Fig. 110, which serves also to give a general idea of any "deep- sea " * sheathing and covering machine, in which the outside covering is * Nowadays, neither shore-end nor heavy intermediate cables arc taped outside, as a rule. Instead of this, these types are usually enveloped in jute or hemp yarns, the yarns (wlien such heavy types are in question) beinj,' less readily damaged by cable machinery during paying out as well as by rocky bottoms and hard ground generally. Otherwise, in principle — though not in detail— this illustration would serve, equally well, to give a good tjencral idea of the heavier type of machinery used for laying up heavy (shallow-water) cables. [Plate XXI. J3 a U o i d [To /ace p. 464. MKCHANICAL I'KOTKCTION AND STRKNGTH. 465 constituted b)- two layers of canvas tape, besides the arran{remeiits of the various parts. This illustration also shews the served core coming from an upjjcr floor, all these various coverings, in this instance, being applied at one operation ; or rather, one behind the other during a single "draw-off."* Relative Merits of Outer Tape and Yarns.— The main object of the outer coverin^f of an ordinary submarine cable — of whatever it be com- posed — is that of holamg the wires together, and of preserving them fnjm decay. The above system of canvas tapes applied an an outer covering to sheatherl cables has been very largely used for a number of years ever since its first practical introduction by Messrs Johnson and Phillips for this particular purpose. It has certain advantages over the previous hemp or jute yarn outer covering. Thus, the canvas (Hessian) tape is more durable, as a rule, than the loose yarns. Secondly, it keeps broken wires better in place, partly owing to the fact that it can be applied with greater tension. Thirdly, it is perhaps rather better able to resist the attacks of living submarine organismsf for a longer time, at any rate.* On the other hand, tapes involve a more rigid and less ])liable cable, which is an objection from a contractor's point of view — as regards general handling up to the time of actual submergence. Again, j-arns are found to adhere together better than tapcs.§ They are, in fact, a superior vehicle for the compound, owing to it being better able to percolate between the threads. For these reasons — and still more owing to the improvement in the durability of jute and hemp yarn — canvas tape is less used nowadays than it was, a return having been made to hemp yarns as well as to jute for this purpose, not to mention the introduction of hemp cords. * Where the core is brass-taped, however, cither this forms a separate process, or where the inner servin;,' is apphed at the same time, the sheathing and outer serving must together form distinct operations. t Hemp yarns arc somewhat readily demohshcd by the teredo, and others of its sort. I Several of the cable-ownini,^ companies have found it a good plan to keep a stock of this Hessian tape at their stations, as well as on their repairing ships, all ready for renewing the outer servings of cables picked up for repairs. The gear for applying the tape to the cable (also fitted on the repairing vessel) is then rendered complete by the addition of draw-off gear, change wheels, and counter-shafting. Thus an old cable, when picked up for repairs, may be re-taped as necessity requires. S An outer covering of canvas tape tends to peel off somewhat readily after a com- paratively short period of submergence. 466 SUBMARINE TELEGRAPHS. Outer Yarn Covering. — A j'arn is what in spinning parlance is i- to the test would be, of course, to lay two cables at the same time side by side, externally covered with each respectively, whilst other- wise similar. To carry out the idea properly, the two samples should be laid in vessels containing the same water, and lined with a specimen of the bottom to be encountered.* Alongside the whole length of the cabling m.achine at the floor level, a counter-shaft runs in connection with the main factory engine shafting ; and from this the taping heads or yarn discs are driven by belts, and the draw gears by means of bevel and spur gearing. A brake is usually fitted to the machine, by means of which it can very quickly be brought to a standstill throughout. As a rule, this brake Flc. III. — Mauling-oft" Gear. almost entirely encircles a part of one of the discs or cylinder frames, and is actuated by means of a lever at the lay-plate. All " cabling " machines, especially tho.se for applying heavy wires — such as the outer sheathing machines — should be set up on a very strong bed-plate, continuous from end to end. * Especially if containing mineral or organic matter. MKCHANICAI, PROTECTION AND STRKNGTH. 473 Hauling off Completed Cable. — Tne ij^car which transmits the hauling motion to the cable through the "cabling machine" is shewn in Fig. 1 1 1. Here the cable is led over a deeply grooved sheave .\, whilst a jockey- wheel C, also slightly grooved, rides on the cable and keeps it jjressed down on the sheave. Both sheave and jockey-wheel are rotated by gearing- wheels I) and K in opposite ways, so that the cable is gripped between them and forced onwards. To ensure sufficient friction between the jockey- wheel and the cable, in spite of variations of diameter during the different processes, the spindle of the jockey-pulley is made to work up or down in a vertical slot. A forked lever F, pivoted on either side of the framework at G, and weighted at I', presses down the spindle ends of the jockey, FlC. 112. keeping the cable firmly grasped between the two wheels. The pressure of the jockey-wheel on the cable is regulated by moving the weight P in or out along the lever arm. The wheel D which drives E, receives its motion through intermediate gearing from the horizontal shaft pre- viously designated by the letter 12 (Figs. 84 and 1 12) and so from the main shafting. The preceding gives an idea of a very usual form of hauling gear for deep-.sea cables. That for " intermediate " and shore-end types is the same ill principle, but the various parts are constructed of stronger material, besides being of a heavier build, as may be .seen from a glance at Fig. 1 13. Here, the hauling-wheel A is driven by the wheels D, E, K ; and the jockey- 474 SUBMARINK TK1.K<;RA1'I1S. pulley c by the wheels (; jiiui II. The piillc)' J is iiitendetl tu take an endless rope, and by that means, drives similar draw-gear, placed, when necessary, immediately above the iron tank (in a direct line with the "cabling" machine) into which the cable is to be stored, Rate of Cable Manufacture.— The iron sheathing wires having a considerably longer lay than the copper stiand, it might appear that the operation of " cabling " would be performed at a faster rate than that at which the conductor is stranded up. As a matter of fact, however, it is liG. 113. very much the reverse, the rate being about as i to 5 in favour of the stranding of the conductor. With such a long lay as the larger iron wires are given, the point which limits the speed at which the wires can be laid up is the mechanical difficulty already alluded to, involved principally by centrifugal force — especially in the case of heavy wires and a large number. This, in turn, puts a limit to the rate of drawing off (with a given distance existing between lay-j)late and bobbins) and thus to the speed of "cabling." The machine itself has, moreover, to be made heavier in proportion to the type MiailAMCM, I'KOTKCTK^N AND .STK1:N( ;TII. 475 and number of wires, and this in turn influences the speed of la\'in_L,f up, with whatever type of machine it be. A^ain, mainly owing to the fact that the bobbins hold so much less wire, the stoppages for changing bobbins and for bra/es are a great deal more frequent in a heavy ty|)e of cable with large wires than in a light type.* These stoppages + are, indeed, the principal cause of the great difference in sjx'ed of sheatiiing small and large wires. Thus, ] mile of a shore-end type of cable is sometimes all that can be sheathed (with outer sheathing) in a working day — though i to lA N.M. is more commonly done. The total time taken up for stoppages of one sort or another is, in fact, often as much as would be sufficient for sheathing a complete mile of cable; whereas in the case of a deep-sea type, 3 X.M. is a very ordinary amount to be completely " cabled " in the same time, at a speed of about thirty revolutions per minute for the cylindrical cage frame carrying the bobbins.* The lightness of this carriage, as compared with the ponderous discs used sometimes for laying u}) heavy cables, in itself makes a great difference, ofcour.se, to the speed attainable with .safety. The larger cable factories have s(jme ten to twelve cable machines, for all types. Each of these machines could, under jire-ssurc, turn out as much as 5 or 6 N.M. in a day. Under ordinary circumstances a large factory manufactures some 30 N.M. of fini.shed cable in an ordinary working day of twelve or fourteen hours from an average of half-a-dozen machines, equivalent to about 180 N.M. in a week.t^ In the case of the last (1894) Mackay-Bennett cable, the manufacture was proceeded with continuously tlay and night; thus .some 50 to 55 N.M. were turned out at Messrs Siemens' works during the twenty-four hours. As a rule, however, night work is not allowed in a cable contract, owing partly to the light not being so good for the work ; as well as to the fact that it involves a shift of " hands " of po.ssibly less experience. * hi early days the slow rate of sheathing with heavy wires was further accentuated by their greater degree of brittleness, which was especially hable to cause breaks at a braze when passing round the hauhng-offdrum. t 'I'ogether with the obvious impossibility of running a heavy (disc) machine at as high a speed as a comparatively light (skeleton) machine. I The /lumit'f of wires and yarns has a great influence on the rate of manufacture as regards all types, by involving a greater or less number of stoppages for insertion of bobbins, joints, breakages, etc. Thus, the modern deep-sea types, with a large number of wires to enclose a heavy core, occupies a longer time in construction than former corresponding types. S The corresponding rate of manufacture over the first Atlantic cable was about 20 N,M. a day, or a little over 100 N..\I. a week. 2 K 476 SUUMAUINK TKLKGKAI'IIS. Cable Tanks al Factory. SixTiON 6. — Stowack, Testing, etc. External Whitewashing.— The cable is coiled into the factory storage tank by h;.nd, ready for testing in water previous to, and ready for, shiji- ment. Each "flake" for layer) is plastered over, by means of a "swab," with whitewash (chalk and water) to prevent the turns (jf the same flake sticking together, as well as of adjoining flakes, either of which occurrences* may often be the cause of serious accidents — by a " foul " in the tank + — on the cable being drawn from the tank iigain. * By this plan, however, it will be seen that the whitewash is liable not to penetrate entirelj- round the surface of each turn of cable. * More especially liable to occur in warm surroundings. + Such "fouls" arc, however, almost entirely confined to laying operations, and seldom occur during shipment from the factory tanks, where the speed of coiling is usually less than h.ilf that adopted for paying out. For this reason no " crinoline " gear is fitted to the factory tanks as ir. the case of the ship tanks ; as well as owing to the circum- stance that in the former the space between the top flake and hawse pipe is invariably sufficient for the turns to take themselves out. I On the other hand, whitewashing oi/r be oxerdone ; inasmuch as in paying out a cable a slight sticking action with the turn below serves as a suitable check to the rate at which the cable flies up the tank. MKCIIANICAL l-l<()TKCTION AND STRKNGTM. 477 Thus, at the Silvcrtowii cable works it has been for some years the custom to lead tl e finished cable on its way to the tank (in fact, just above it) through a wooden die-box loaded with whitewash, having a rubber ring at the entrance. This plan (devised by Mr I*'. Hawkins) has, moreover, the advantage of saving labour in the tank, besides enabling coiling to be carried out a trifle faster. Coiling into Tank. — The corresijonding tanks (see illustration at head of this .section; into which the cable is coiled from each machine arc of enormous size, having a diameter of somewhere about 30 feet, and a depth of 15 feet or .so. Each tank is capable of holding something like 200 N.M. of deep-sea cable.* In the centre of these factory tanks is a wooden cylinrlrical or conical framework — about the height of the tank, generally — -round which the cable is coiled (r'ght-handcdlyt) from the wall (or "outside") of the tank, turn by turn, towards the centre. J On this wooden frainework stands one of the coiling hands who guides the cable down to the tank, where it is taken in hand by the other "coilers," of which there are .several, one of whom journeys round the tank with the bight of cable. On the completion Fic. 114. — Cubic laid { compared with the standard tests of the core at 75' F. — in order to detect at once any sijfns of deterioration, and for subsequent comparison — should be either made with the c.ible at the same (standard) temperature ; or, if this is impossible, a very correct idea of its actual temperature at the time of testing should be arrived at, ill order to make the required allowance (or reduction) for this difference of conditions. I In the case of the dielectric to be afterwards converted back into resistance, by use of reciprocal tables. CHAPTER V. COMPr.ETEl) CAIJLE. Skction I. "Matters of Importance : Data necessary. Skction 2. --Mechanical Testing: Tensile Strength — Qualifications — Representative Deep-sea Cable : Representative Shallow-water Cable Specifications and Tests ; Details of Construction : New Types Cost of a C^ble — Data and Records. Skction 3. "Light Cables"— Karly Forms; Core without Sheathing: Allen's Cable; Siemens' Cable ; Lucas' Cjible — Requirements ; Weak Features in Hemp and Iron Light Cables — LatcrTypcs of Hempen Cables — Trott and Hamilton Cable Unlaying and Laying up of Turns in a Cable — Conditions regarding Hempen Cables- Light Sheathed Cables ; Hright's Aluminium-bronze Sheathing. Spxtion I. — Re()Uirements and Tests. Matters of Importance: Data necessary. — Besides the specific gravity of a cable and its weight in water — together with a knowledge of the " break- ing strain " — being matters of importance both for purposes of laying and recovery,* it is also nccessarj' to know, for loading recjuirements, what the weight v.iU be of a given length when wet in air. This is in order to arrive at the dead weight of cargo involved by a given cable when coiled into the tanks of the layi:i;cnce. When paying out a cable it is, at any rate, essential that it should be laid from a water-tank ; besides being covered with water a short time beforehand, with a view to the detection of any fault previous to submergence. 'I"hc alternating conditions of wet and dry are the most dangerous possible for ,in iron-sheathed cal)le, by intlucing chemical action and spon- taneous combustion. Thus it has been pointed out that if there are not facilities for keeping a cable permanently wet, it had better go out to its destination absolutely dry, until .ibout to be laid, after being tested (as core) in water at the factory. It may, however, be remarked that when a cable has once been covered with water, it takes some time to become dry. + The weight of a cable in sea-water may be calculated approximately from its weight wet in air and from its diameter, as follows : — Find the cubic conti^nts in cubic feet of, say, I fathom of the cable. Multiply this by weight per cubic foot of sea-water {(>4.S lbs.). .Subtract this result from weight of I fathom of cable dry in air, and the weight of i fathom in sea-water is obtained. { The weight wet is usually from 5 to 10 percent, more than when dry with an average close-sheathed cable of the present day. S When estimating the weight of a cargo of cable, the weight of water which is pumped into the tanks to cover the cable must be considered. Tlie water in the tank naturally occupies all the space not taken up by the cable. 482 SUBMARINK TKLI'XIRAIMIS. respect.* This is carried out in prHCtice by han., calculated and even measured — preparatory to its ultimate adoption for the required purpo.se. The breaking strain of an ordinary iron-sheathed cable may be calcu- lated from the accredited breaking strain per square inch of the material composing the wires and from the sectional area of each wire. This latter is obtained from the formula where y is the radius of a circle and t = 3.1416, the relation existing between its circumference and diameter. Then the total breaking strain of the complete sheathing should be the result of the above multiplied by the number of wires composing the armour, assuming all to be of the same gauge and quality. It may also be calculated, of course, from a knowledge — if such exist — of the actual breaking strain of each wire, which when added together will give the breaking strain of the entire sheathing : or, again, the measured * This may, at tlie same time, also be turned to account as a test on the individual specific weights of the materials by weighing each separately. COMPLKTKI) ( AIU.K. 483 breaking strain of a single wire may be taken as representing that of each of the other wires, and may be multiplied by the total number of wires to give the total breaking strain of entire sheathing. Though, roughly speaking, the strength of an ordinary submarine cable is very often constituted solely by that of the iron armour, this is not always the case — at least not in the opinion of some authorities, who aver that, at any rate, hemp cords, when applied with the proper lay (as already referred to), add materially to the strength of the wires, and so contribute to the total strength of the completed cable. This being so, it will be evident that absolutely accurate information regarding the breaking strength of an entire cable is only obtained by actual measurement — i.e., by testing samples of it. Even this is not alto- gether satisfactory because of the necessarily short lengths experimented on. In any case, the engineers on behalf of the owning company usually require a certain number of lengths of the deep-sea types of cable in a given contract to be tested to their satisfaction, as regards tensile strength and elongation. It need, perhaps, scarcely be remarked that no torsional tests are ever applied to any type of submarine cable when completed. The ordinary breaking strain of a completed deep sea cable intended for considerable depth should be somewhere about 6 or 7 tons at least, varying according to the type and depth it is intended for. Thus, the last " Anglo " Atlantic stood a strain up to 8.2 tons when tested, with an elongation of 4 per cent. The breaking strain of the completed cable is invariably somewhat greater than what it is calculated at from the wires alone, the weakest point in a number of wires never being exactly at the same spot.* From the breaking strain, absolute information is obtained as regards the depth of water to which such a type can be laid with some sense of sureness that it can be subsequently recovered if necessary. * Moreover, this is so owing to the friction between the wires acting as a mutual support in a close-sheatheil cable. In the case of a cable having hemp cords applied with the proper lay, this discrepancy is, again, further accounted for. 484 SUBMARINK TKLEGRAPHS. Section 2. — Mechanical Testing. Tensile Strength. — Several kind.s of apparatus have been devised for the purpose of apjilyiii^ a gradually increasing stress to a cable till it breaks, the value of this breaking stress in weight being then noted as represent- ing the force, or strain, it will bear — or rather, the minimum at whicli it breaks. The earliest and simplest form consisted of a tripod about 30 feet in height, supporting at the top a pulley round which the upper end of the piece of cable to be tested was secured. The lower end was fastened to a similar pulley, to the spindle of which was hung a ^ 'atform, on which weights were placed one by one, until rupture occurred. Fig. 115. — Early Tension and Torsion Apijaratus. In this machine the degree of elongation was ascertained by measuring just before rujjturc the distance between two small discs ^^ (Fig. 115) pre- viously secured to the cable at about 3 yards interval, in line with two cross pieces c. These discs were graduated round the circumference, so by making the zero points coincide with a wire stretched parallel to the cable, before tension was applied, the amount of torsion was afterwards shewn by the angle through which the discs and cable had turned. A more complete and reliable form of apparatus, originally designed by Messrs Gisborne and Forde (Fig. 116), has a solid beam A supported and firmly secured to masonry by two u{)rights. To one end is bolted an iron shoe, the upper end of which has a strong hook, or shackle, for securing one end of the cable ; at the other end of the beam pivots a bent lever H, the long arm of which carries a hanging platform and weights, the short arm having a hook to hold the other end of the cable. The lengths of the [Plate XXII. [To face p. 484. COMPLKTKI) CABLE. 48s lever arms are as i to 10: the counterpoise C balances the weight of the lever arm and platform. The cable passes throu},'h a trough n filled with water for observing the erects specially due to water— such as contraction in the case of hempen Kk;. 117. — Brown and Lenox's Cal)lc Testing Machine. cables. The holes in the ends of the trough which the cable only partially fills up are rendered water-tight with tow. The elongation is measured by means of a scale c which passes through the ends of the trough enclosed in a pipe placed close, and parallel, to the cable. To prevent the torsion of the cable, or stretching of the various 486 SUHMARINK TKLKGKAI'IIS. parts of the apparatus affecting the position of the scale, the clip d on the cable is fitted with a small circular disc which enj^ages at right angles in a notch in the scale, so causing the latter to move horizontally with the clip. At the other end, a small cylinder is fixed to the cable which, as the cable twists, turns in proximity to the graduated part of the scale : the cylinder itself is divided off as a vernier to permit of greater accuracy in reading off I'e measurements. To effect a test, the platform is first sufficiently weighted to tighten the cable ; the vernier is then adjusted, and more weights added at regular Fk;. iiS. — Brown ami Lenox's Hand-l'ower Tension Machine for Ropes, etc. intervals until the cable parts. A glance at .the illustration (Fig. ii6) shews that the ratio of the strains on the two^arms of the lever remains constantly as i to lO, whatever position the lever may be in : the weight, therefore, on the platform at the moment of rupture is equal to a tenth of the strain on the cable. The elongation is obtained by the displacement of the vernier cylinder e along the scale up to the instant of rupture. Messrs Brown, Lenox and Co. are a firm of engineers who have always been famous for making a close study of the requirements involved in apparatus and work of this description — in [fact, a large proportion of COMI'I.KTKI) CAULK. 4S7 the tclc^rapli cables at the bottom of the sea have previously iinclergonc tests at their works. Fig. 117 represents a recent type of hydraulic power machine of vertical form, as designed, constructed, and used by this firm. Here the power is api^lied by hydraulic cylinder ai.d hand pump. This machine — designed for testing samples of chain, cables, iron, etc. — tests up to as high as 50 tons, though for the purpose in question such power would never be required.* Messrs Brown and Lenox have also another hydraulic machine — horizontal in.stead of vertical — capable of applying the same stress. This firm has also a hand-power vertical machine (Fig. 1 18), with wheel- worm and screw-gear for applying the power. This machine tests up to I ton, and is especially designed for testing samples of canvas, rope, etc., and is not, therefore, turned to account in regard to submarine cables, though it might very suitably for testing the component parts. A cable covered with good iron should bear at least 2 tons per lb. of iron wire per fathom ; and the equivalent elongation should be at least 3 per cent.+ The elongation of an ordinary iron-covered cable (the sheath. ng of which forms practically a metallic tube) when exposed to half of its supposed breaking weight varies from 0.5 to i per cent. — an amount, by the waj", which could never injure the core. Whilst being laid, a cable generally untwists slightly, but the elongation from this cause is also insignificant. Moreover, it is not permanent, as a cable always reaches the bottom in exactly the same state as it was in when first coiled in the tank. The modulus of tension (or figure of merit from a tension standpoint) of a cable is a most important matter, in that it rejiresents the maximum length of itself which the cable will support in water.ij; In deciding on the minimum breaking strain allowable for a modern deep-sea cable, it is not unusual, where possible, to give the cable .something like four times the tensile strength that is necessar)- for its own sus|jcnsion in the greatest depth in which it is to be laid. Thus, for such a depth as 2,cxx) fathoms, a cable should have sufficient strength to support .some eight, * In connection with submarine telegraphy this machine is, liowever, frequently used for testing stranded wire and hemp grapphng ropes, which are often made of a multiple type, bearing a stress of 25 tons and even over. t The elongation of a completed cable is, however, almost invariably slightly greater than that of each individual wire composing it. This is partly owing to the cable's tendency to unlay and straighten out when subjected to a strain ; as well as to the mutual support of the wires— especially when fitting tightly together under strain. + It is obvious that this may be calculated thus — '" -•--'• , , , , Breaking strain Modu us of tension = .., ■ .,. ■ : — Weight in sea-water 488 SllUMAklM. TKI-KCKArilS. or more, miles of its own wei^Mit in water. This is highly dcsinible ifoiil)- from a jmying-out point of view — let alone picking-up re(|uirenients.* Reverse lays, though they produce great compactness as an outer ser\ - ing, and form an excellent binding to hold the wires together, cannot produce a breaking strain such as may be obtained where both coats are laid in the same direction. This is owing to the fact that, with lays of the .same length in opposite directions, any elongating tendency in the one is cxactlj neutralised by that of the other, and thus under these circum- stances the strength of the outer st .ving is at once put to the test — long before the sheathing wires, with which, therefore, it cannot possibly work. In some ways, it would seem, if the outside covering is intended to increase the strength of the cable, that the two applications of hemp cords (or yarns) — where more than one is ado|jted — should be laid with the same, rather than with reverse, lays ; besides, of course, being applied with such a length of lay as bears the right relation to that of the iron wires according to the relative elongation of the materials. This latter, at any rate, is always made a close study of by those who seek to ensure the outer cover- ing taking its share in the total strength of the cable by causing it to break tuith the iron wires, instead of some time before. Qualifications. — For jjurposes of la)iiig and repairing operations, the completed cable should be flexible, as well as strong, and not inclined to kink, t It should also, even when kinked, bear a considerab.e strain before parting. An advantage in the sheathing wires of an ordinary dee])-sea cable being composed of " homo " iron rather than of actual steel exi.sts in the fact that the latter are exceedingly springy and " homo " wires are less .so. Finally, it may be remarked that in the present day under average ^.rcumstances — as regards conditions for laying — the success of a cable depends, perhaps, principally on its construction. Representative Deep-sea Cable. — The actual available strength of the last (1894) " Anglo" cable is nearly 30 per cent, higher than that of the 1865-66 Atlantic (open-sheathed) type, though, of course, the specific gravity is not so low. On the opposite page (Fig. 119) will be found sections of * The above factor of safety is necessarily subject to modification in practice at extreme depths or where— owing to the introduction of high speed (machine) signalling — the weight of core becomes excessive without introducing practically any increase in the strength of the entire cable. t Flexibility is of almost first importance in the instance of submarine-mine cables, which require constantly to be coiled and uncoiled. ;——;•> .■ — ., —--. . . ci [IM.ATK XXIII. rt 'SI a. Q > o O c [TbjMcp. 488. 2 L ( iiMi'i.i.i III rAiii.i:, 489 Liicli t)|K! composing this latest* Atlantic cable + a splciulid specimen of up-to-date en^ineerin;^ in ocean tele^,fraphic enterprise, and a vast im- provement (Ml lliis company's previom cables. The lull specification of this typical and important specimen ot r cable, made and laid by Messrs Siemens Brothers in i.Syi between Hacton (Norfolk) and Horkum Island, over a sandy and fairly level bottom, with a ma.ximum depth of only 20 fathoms. This cable is the joint propertj- of the German and Kn^dish Governments. Another similar Anf^lo-German Government cable (with certain special " At the moment of scndinj,' in proofs ;i new French Atlantic cable is about to be laid. This, having prarticaliy the same ror(.' as the above, is similar in character, except that in introdiicinji an extra niimbcT of siieathinK wires of tiie sanu; K"i'KC ''^ wei^jht is siibslanlially if not seriously • increased. t The illustrations here jjiven may be taken as a jjood example of the varicjus types of cable suitable for different tlepths - up to about 3,o(X3 fathoms — that is to say, where a heavy core of this dcsrri|)ti(m is em[)loye(i for pur])os(;s of liiKh-specd working; on lonj{ and busy ocean cables. Where a shorter length is in cpiestion, or ordinary nianual transmission suffices, tiie number of sheathing wires involved by the smaller core would be correspondingly less. I The length of lay is actually about 4 inches, presenting an appearance of a spiral. S The Electrician, 12th October 1894. 490 SUHMARINE TELEGRAPHS. modifications alluded to elsewhere) was constructed last year (1896) by the Silvertown Company.* These specifications give fairly fully all that, as a rule, requires to be actually set forth — indeed, Post Office specifications are somewhat famous for their amplitude.f Specifications and Tests. — The cable is invariably tested electrically after complete .shipment in its various .sections, either by the engineer to the owners, or in his presence. Indeed, there is .sometimes a clause in the specification ensuring provision for this, whilst stating, moreover, that the cable must test steadily throughout, and yield uniform results with both currents. It is al.so sometimes signified in the specification that every facility is to be given to the engineers for inspecting all the materials used in the manufacture of the cable, and for testing the.se materials if desired, besides a separate room and testing apparatus being provided at the contractor's works. Details of Construction. — However, bj' those who, from e.vperience, are best able to judge, it is not, as a rule, considered necessary, or even desirable, to go too clo.sely into details of construction in the specification, but to leave them — in which there is, moreover, no finality— to responsible contractors who have a rejjutation t(j keep up.* and often a greater expe- rience in details to work upon than any consulting engineer. Again, there is a certain prejudice to the publication of details of con.struction, such as might be involved by stipulations in a contract. Thus, a very ordinary specification clause with reference to the inner .serving, runs somewhat as follows : — " The inner .serving to consist of a good and sufficient serving of jute yarn steeped in cutch or other preservative .solution ; " without any kind of reference to the lay of the yarns or any oti^^r 'Jmilar detail in the method of carrying out the manufacture. Once more, where an application of compound is to be applied imme- * At the time of writing, this cable was still a subject of contract, and the particulars were not, therefore, avuii.tMc. + Moreover, the construction of all I'ost Office cables is very carefully overlooked by officials of the Department at the contractor's works. + Moreover, it must be remembered that as the contractors usually undertake the maintenance of the cable in good working order for a certaui time, they are — if only for this reason — almost as interested in its complete success as the owners themselves. COMI'LETED CABLE, 49I diatcly outside the laid-up wires, it is most iinportant that at the time of appHcation it should be quite cool ; yet as often as not, no such stipulation is actually mentioned in the specification, it being known that the contrac- tors are fully acquainted with the disastrous effect of the compound being applied hot straight oti the iron wires, and that they are probably as anxious as the owners that the cable shall be a success. New Types. — It need scarcely be remarked that manufacturers are always prepared to construct any sort of cable specified — within certain limits, at least. Sometimes, however, it happens that the contractors have opportunities of recommending a certain type of cable, such as they know by experience to suitably meet the requirements ; or, may be, in which there is some manufacturing specialty of theirs — the result, perhaps, of a large range of practical experiment and experience. Cost of a Cable. — In estimating the cost of a proposed cable, the first consideration is naturally the points to be put into communication ; .secondly, the nature of the bottom between those points ; thirdly, the nature and length of various types suited for the different depths and the form of bottoin to be encountered. These points having been settled, it becomes necessary to calculate the cost of materials involved at the existing mar.cet i^rices. The cost of the component parts of a core ha\e already been touched on in a previous chapter. With regard to its .serving, sheathing, and outer covering,* ordinary gahaniscd iron wire — standing 25 to 30 tons per square inch — as used for the hea\y tj'pes, costs somewhere about ^8 to £g a ton ;t the "homo" wire, as useil for deep-water cables, is sold at about ;^20 to £2^ a ton ; and steel (of special quality), bearing a .strain equiva- lent to 120 tons per square inch, sometimes runs into as much as ;^44 a ton. Jute can now be got at £1^ a ton ; but hemi) varies in price from £7,0 to ;^40 a ton — the best species being e\en more. The cost of a completed cable varies, of ccjur.se, very much. Certain deep-sea types have of late j-ears been known to be supplied at as low a * It should, however, l)e remarked that owin^ to constant fluctuations in the market, all these prices arc very variable within comparatively short periods. t The extra charge for galvanisinjf averages at about £1 a ton of shore-end wire. 492 SUMMAKIXK TKLKCUAI'IIS. figure as ^75 a mile ;* whereas shore-end types run into some X'300 per N.M. and over.+ The cost of laying a cable may be often very roughly considered as somewhere about half as much again as the cost of construction ; and may be estimated for (with a big margin for risk and contingencies) on that basis. Such estimate, of course, should include all the labour* charges involved. § The value of a cable when laid is the item of special consideration to shareholders and prospective shareholders ; this including insurance. It is, however, sometimes a nice point as to what contingencies insurance would cover at a push. Data and Records. — For some reason or other there is still a certain amount of difficulty in procuring full ])articulars respecting submarine tele- graph lines that have already been laid for various companies. This is somewhat surprising in view of the fact that submarine telegraphy has many years ago emerged from the pioneer stage — if not actually from the sphere of science into that of routine. Moreover, the practice of cable engineer- ing has now fallen into the hands of several big contracting firms, whereas for some time it was practically in the hands of one. However, that there IS a difficulty, there can be no question. In their excellent pocket-book — the u|)-to-date vik/i' mecum of electric engineering practice — -Messrs Munro and Jamieson have given the results of electrical tests of various cables from the year 1872, together with such mechanical data as the individual weights of each component part."! More- over, Mr H. R. Kempe's now famous, and very complete, work on electrical testing** contains similar information regarding some of the more recent * ^250 to jC},oo per N'..\I. is a fiiir price for an Atlantic cable, with the heavy core involved, untlunit laviiti;. This wouUl be materially more in the case of extra heavy cores providing for machine transmission. + The average cost of a length of submarine cable may be apprcximately taken as nearly seven times that of a corresponding land wire. \ So long as Trades Unions hold sway — to the detriment of the country's trade, and, therefore, to its sulijects generally — it would be well if a clause providing for the contin- gency of strikes were embodied in all contracts. S Atlantic cables have been made and laid for half a million of tnoney. This figure compares favourably with the million sterling expended on several of our warships. II "A Pockct-Book of Electrical Rules and Tables," by John Munro, C.E., and Andrew Jamieson, F.K.S.E., M.lnst.C.E. (Charles (Iriffin and Co. I '. The same sort of tables are also to be found in the " Handbook of Practical Telegraphy," by R. S. Culley (Longmans, Green and Co.). ** "A Handbook of Electrical Testing," by H. R. Kempe, A.M.Inst.C.E. (E. and F. N. Spon). COMI'I.KTKI) CAlilj;. 493 cables. The same class of particulars was presented by Clark and Sabine* regarding cables laid between 1864 and I1S70. In the author's opinion this information — as regards the mechanical data — is of but little use by itself F(jr the above combination of reasons, then, it has not been repeated here, and owing to the difficulties already mentioned, no table whatever has been given. However, in the Appendices will be found a form — already referred to — which gives an idea of the class of information such as is of .some value, from an historical record point of view, for obtaining and filling in as opportunity occurs. On examination of the form in question, it will be evident, from what has already transpired, that much of the mechanical data would only be required as regards the deep-.sea types ; and, on the other hand, some only as regards shore-end and intermediate types. The individual length and description of each type should be furnished, as well as other information respecting each and all — such as gauge and number of wires in the sheathing or shcathings, also the description of the outer covering. Moreover, the results of the particular tests applied to the wires used in every type should be set forth under that particular type. ■■'■ "Electrical Tables and Formulif,' by Latimer Clark and Robert Sabine (E. and F. N. Spon, 1C71). IiiiloKiiropcan 1 olcgriiph DciurtmeiU : SLili iJiiarliTS at Kao. 494 SUHMAKINK TKLliGKAl'lIS. Section 3.— Lk hit Cables. Early Forms. — Tliere was a period in the history of submarine telegraphy when many cle\ices in tlie form of wliat went b)- tlie name of " h'ght cables"* (/.c, without any outside armour whatever) were seriously thought of; and several undertakings based on their adoption were set afoot. These, houexcr, were never turned to practical account, owing, presumably, to the heavy risk invoked. These devices wore a vory natural sequence to the various failures in the Mediterranean, and elsewhere, in the fifties and sixties — failures not only to recover a heavy ordinary iron-sheathed cable, but also actually to maintain control over it during the operation of paying out, for want of efficient holding-back gear on the laying x'essel.t Mr C. F. Varley, F.R.S., was always an enthusiastic advocate of light cables, and so was Professor Fleeming Jeiikin, F.R.S. According to most of the many devices in the wa\' of " light " cables, the little strength considered necessary was put in the conductor itself,* the latter being iron very often. An early patent § was taken out by Monsieur F. M. Baudoin for a cable based on this principle, the conductor composed of six iron wires, each .079 inch in diameter (protected only by bitumen j, encircling a heart of tarred hemp — a reversal .somewhat of ordinary practice. The light cable, however, which attracted the most attention was that of Mr Thomas Allan. This consisted in a solid copper wire surrounded by a * Some of the above, however, scarcely partook of the dignity of a "cable," as the term is usually understood in the |jrcsent day. .Still, they represented the first principles of a light cable in its most essential features, and were, perhaps, on the whole the most sensible form. + The number of different kinds of patented cables inspired in the minds of inventors about the time of the " First Atlantic " and between that and the " Second Atlantic " were simply legion. These strange devices were intended to overcome su|)posed impossi- bilities. Besides being of the " light-cable " description, cheaj) insulation formed a feature in most of these. In some the conductor — in one instance to be a spiral capable of being drawn out -was only to be enveloped in a serving of rope, composed of hemp yarn or other vegetable fibrous substance worked up with varnish, marine glue, pitch, or the like. This covering was to be applied with a very short lay. Such a cable would obviously be unsuited for the b')ttom of the sea — especially where at all irregular— even if capable of being laid. I This was apparently, to a great e.xtent, with a view to economy — as well as light- ness — no outside sheathing wires being employed. In some of these schemes only just enough weight was furnished in the conductor to ensure it sinking when covered with its insulating material. Moreover, as a rule, no notions of after-recovery were indulged in, the point aimed at being to make a cheap line which could be successfully laid from point to point. S In 1858. COMPLKTKI) CAHLK 495 number of closely fitting smaller steel, or iron, wires,* applied spirally. The conductor so ff)rmed was covered with ordinarj- gutta-[)ercha or india-rubber insulation — the latter at an)- rate outside — the core being encased in a thin covering of hemp, tarred string, or can\as impregnated with pitch, or marine gluc.+ All these were intended for insulating as well as ])reserv€ative purposes. I'lG. I20. — Alliin's Light Cables. It was claimed for this cable — two forms of which are shewn in Fig. I20 — that it combined the utmost lightne.ss (weighing only 353 lbs. per N.M. in sea-water) consistent with necessary tensile strength (2 tons).* It * Mr Allan appears to ha\e considered at that time that j.;alvanising had a weakening eflfect on iron, and his wires were not to be galvanised. In point of fact, in the present day it is found to slightly increase the breaking strain. + Marine glue is a mixture of one part of india-rubber dissolved and softened in mineral naphtha oil, and two parts of gum-lac. I Thus it was said to be capable of \ertically supjjorting in the sea the weight of 12 miles of its own length. Again, not being bulky, a ship of quite medium size could easily carry some 3,000 miles — more than sufiic'ient to telegraphically connect Europe with America. Moreover, the laying could be et'fected with little risk and without elaborate " holding-back " machinery, the cost of construction added to that of laying being some 40 per cent, less than in the case of an ordinary iron-sheathed cable to meet the same requirements. It was even claimed that, by such a form of line, the speed would be increased by as much as 50 per cent. The reverse might more reasonably have been expected. However, in addition to the objections ap()licablc to all light cables, it w.is remarked with regard to Allan's cable that the contact of the two ditierent metals in the conductor would be likely to set up serious chemical action. 496. si'iiMAKiNh; ri;i,i;(;i/ successfully. t With the lit,dit of e.xjje- rieiice it would seem tliat the balance of opinion in those days was correct. Wc have practically adhered to the ori^^inal type of cable from the l)e^,dn- miij4 -an unusual circumstance in enj,'ineerin;reat difficulty in obtainiuK f(ir it a fair trial in practice ; though contractors, of course, may often be in a jiosition to try a novelty of their own. Furnished with an extensive practical experience, the latter are, however, ( ertainly the l)est judKes, and anything they attempt in tlie vv.ay of novelty is distinctly more likely to prove a success. (:o.\iri,i.Ti;i> ( aiu.i,. 497 canvas, wcavrd yarn, etc., |)laitc'I up ic-vitsi; wjiys, with a vi(!\v to hiiidinfj the uli()I(! ninrt! firmly lo^'ctlicr. At a later date MM. Hiondot and Unurdin d(;si^ncd a type of lij^dit cable uliif h was exhibited al the Paris ICIectrical Ivvhibition of iS.Si. This was, in reality, nic-rely an ordinar)' core ; tile onductor bcin^' a sin^de solid copper wire .iiH inch in diameter, and the di<;lectric consti- tuted by three; alternate layers of ^;utta-percha and I'ara ridjber,* with a coatin},' of ('liatt(!rton's compound b(;tween the conductor anrl the first dielectric layer. The i^utta iise(| for manufacturing' the outer layer of the insulating' eiivehipe was nii.xed, whilst hot, with bichloride of mercury, in order to kill any submarine creature which mi^^dit attack the insulatron. The whole was covered with rubber-|)roofed foUoii tape of j^'reat streti^'th anri dmahility. I'he point of s|)ccial interest in connection with this li(.iht cable was, howevi'r, the ilctailed manner in which, for the first time, the desijfiiers had endcavourerl to co|)e with the difficulties of properly laying such a core. 'I'hey reco^'iiised that so far from any holdint,'d)ack strain IxMiit,' admis- sible, they must actuallj' force out their line, owi'i^ to its e.Ktreme li^,dUness. Accordinj,dy, their arrauj^'cments inclufled a larj^e reel or firuin -mounted liorizontally on the laying v(;ssel — which was to be turned !))• an iiidepen- di'iit en^;iii('. I'he speed of this, however, was to be governed by that of the vessc-l's propelling' machinery. The iflea was that the rale of payinj^' out would then vary in accordance with the ship's sp;;ed, and would only differ from it by a [jreviously arranj^ed propr)rtional quantity, rei^reseiu ' >■ slack — i.e., the perccnta^^e of e.xcess cable over 'listance covc;!'ed.+ 1 u^ cable passed over the shi|)'s stern into the sea betwei:ii two hori/.mital rollers (.geared toj^ether and coveri;d with india-rubber. A small model illustrating' the payin^'-out machinery for laying' this li[,'ht (core; cable was exhibited alon^' with the specimen of the cable itself In onler to obviate tin: necessity of joints of insulation in so unprotected a line, the whole len;,'th of cop|)er conductor was to be prepared before- hand, in one piece, so as to enable the insulation covering,' to be a|)])li(;d in one continuous length in each coat. Ihc joints of the conductor were * As l)cfore stilted, the < ombination of layers of both j;uu:i-percha ami india-niblicr in iiny dielectric could never be a success in praf:tice on account of the different dejjrees to wlii( h eai li arc affe'ied by a rlian^e of tcnipcraturc, and especially in the rase of /)//;r, iinvulranised, rubber. 1 III lliis, liovvcver, the inventors appear to have overlooked two fa' Is. First, thai the ship's s|)ecd tiiroiiKll the water bears no fixed reliable ratio to lh-pe above alluded to, one of the prin- ciples of this cable was that the breaking strain would be constituted by the ■* It may be observed again here that the design was that of the contractor himself. t This cable is mainly of interest on account of its ingenious, and beautifully carried out, construction. The tape being of a material thickness, there was a continuous indentation at the edge of the metal tape for the oveila]) of each turn to fit into, thus producing a perfectly fiat surface. I The final breakdown was attributed to insufficient slack having been paid out on getting into shoal water. The cable must have been suspended over a great length, and Ijeing unable to withstand the strain brought on it at the points of suspension, parted before the laying vessel had reached the other shore. The conclusion to be drawn here is that essentially light cables, by reason of their low tensile strength, must be laid with consideral)ly more slack than those of ordinary type, so that they may experience the least jiossible strain, both during and after submersion. This being so, any looked for saving in cost in manufacture would probably not be realised in the end. Moreover, all other things being equal, the working speed attainable would be liable to be less for the same reasons — /.('., by increased percentage of slack necessary for a light cable. Thus, the nett returns .accruing to a light cable, if above a certain length, would tend to be below those of a cable as ordinarily constructed. S Based on the patented invention of the late Mr Edwin Payton Wright for a com- bined hemp and iron rope, and fully described in Fart I. II -Such a cable is naturally laid up by each bobbin on the carriage of the sheathing machine being alternately of iron wire and hemp yarns. COMPLKTKI) (AlU.i;. 499 Slim of the breaking' strains of the iron antl the hcmi) — both bciii^f a|)]jlic(l together with the same lay.* It has an advantage over the Wright cable in obtaining an equal strength in a smaller bulk, thus reducing the surface area. On the other hand, the hemp not being applied round each wire, but only between wires, the feature of ])rotcction to the iron wires — for however short a time — could not apply in this case. Moreover, after the hemp has decayed, the wires are more than ever free to buckle into the core. Nevertheless cables of this description were adopted for several important lines — notably on one to Australia — and again between certain points on the north coast of South America. It was, too, a good deal less costly than the previtnis hemp and iron combination. It may be remarked here that either of the above types in obtaining a low specific gravity by using a large proportion of hemp, are of necessity of great bulk, comparatively speaking. Other combinations of hemp and iron for deep water — based on the principle of a low specific gravity for great depths — have, from time to time, been devised. This, with a view to meeting the difficulties of laying, and still more of recovery, experienced in deep water — both in respect to " holding back " during paying out, and to the weight in suspension whilst picking up. Requirements: Weak Features in Hemp and Iron Light Cables. — For purposes of recovery, a cable should liave as low an actual weight in water as possible, combined with a high modulus of tension,t but should not be of great bulk, as this introduces outside friction.* The above low specific gravity combinations of iron with a large quantum of hemp arc very light in air when dry. On the other hand, when wet — owing to the large amount of water absorbed by the hemp — they become materially heavier in air. Thus, in loading the tanks of a ship with such a cable, it not only requires a large amount of space (thereby involv- ing extra cost) on account of its great bulk ; but also, further, the limit of length which can be carried comes into serious consideration by reason of its weight when wet. In fact, a cable of this descrii)tion must be regarded as a heavy type for transport purposes, owing to the dead-weight of water which it absorbs. * .Such a system of cciiial length of lays does not, apparently, take into consideration the difterent rates of elongation of the two materials. The breaking strain of the two together was, however, said to be the same as the sum of each of the two taken separately. + Sometimes also expressed as the modulus of tenacity. I In these hemp and iron cables, the strain due to friction may easily be greater than that due to the dead weight of the cable itself. - •: ... .. .....t ^.„ 500 siiiMAKiNK ti:i,i;(;k.\1'I1s. Such a cable has an actual brcakin^^ strain — of even greater importance for recovery v.ork than a low specific ^'ravity — far below that of a corre- sponding close-sheathed line. Under strain, tlie wires of any open-shcathed cable are liable to break- one by one — instead of all toj^ether as in the closc-sheathed ty|)e — and to be pulled in on to the core. In pickin^r up a bulky, opcn-shcathed cable, the biL,dit is likely to become flattened on the i^rapnel by tiie wires spreading out until each in turn parts under the unequal tension— or at an>' rate the core is liable to obtrude between the wires where they are flattened out. In fact, these open-sheathefl — or "open-jawed" cables, as they are sometimes termed — are alwaj-s more subject to faults. Thus, if a wire breaks, either end may pierce through to the core, whicli could not well happen with tlie close- fitting arch type of sheathing where each wire butts firmly against the next.* Again, the " oi)en-jawed " type lays itself open much more readily to the successful attacks of the teredo (and other similar eneinics of cables), which cannot so well work their wa\- into a close iron-sheathed line when in perfect condition. It is true that the hemp may tend to preserve the wires, to some extent, for a certain length of time. Hut this soon deca)'s ; especially as the oxide of iron — or rust, in common parlance — tends to destroy it. Thus, ulti- mately, the ojjcn sheathed cable becomes, jjractically speaking, a cage composed of a bundle of loose iron wires, in which form the}- decay more rapidly than ever on account of their entire surface being exposed to the oxidising influence of sea-water.+ It was mainly to meet these difficulties that Hright and Clark's compound was introduced as an extra preservative for resisting oxidation beyond that of galvanising, the silica being added with a view to defeating teredo and other such-like attacks. * The wires of a cylindrical metal tube, in forminj,'- a complete arch, retain their position even under a heavy strain, and so protect the core, by taking an ec|ual pressure all round. The total resistance to stress is, in fact, in this type very much enhanced as compared with an open-sheathed cable, where the wires become deranj,'ed with fatal consequences sometimes, owinj< to the absence of any such metallic arch or cylinder. t On the other hand, with the (r/^rc-sheathed cable, when the outside co\erinj,f becomes decayed, there is still a complete cable with many years of life remaining. Moreover, as the wires butt against one another, their inner side is protected from o.\idation, even after the outside covering of yarn, or tape, has been removed. Thus, the strength of a cable of this class is likely to be maintained fov an appreciablv longer time than is possible with the open-sheathed type. Indeed, frori a durability or " wear-and-tear '■ point of view, the latter is probably unsuitable even for the deepest water — for which it was especially designed, on account of its low specific gravity. - ; coMi'i.i.Ti.n (Aiti-i;. SOI An iron close-shcathed cable so dealt with now forms the usual type of cable adopted;* and this, therefore, is the type the construction of which has been followed up here in all its stages, subscijuent to the serving of the core. Later Types. —Some remarks are now due concerning the more modern notions of a light cable— after the pattern of a hempen sheath, pure and simple. As early as 1.S64, the late Mr Willnughby Smith suggested to the Atlantic Telegraph Company a type of light cable, the core of which was to have two coverings of hemp wound on in opjiosite directions, the inner covering consisting of eight strands and the outer of seventeen. This cable was to weigh but a little over \ ton in air, and have a breaking strain above 4 tons — eciuivalent to about 6i| N.IM. of its own length in air, and as much as 29 miles in water.f However, when a sample of this cable had been under water for six months, Mr Willoughby Smith found that the contraction of the hemp had caused the core to protrude at several places. In 1883 Captain Samuel Trott,J of the " Anglo" Company's S.S. " Minia," and Mr F". A. Hamilton strongly urged the claims of a light cable of their device. This, indeed, may be said to be the only light cable within recent years that has attracted .serious attention. § This was again a hemp-sheathed cable without any iron whatever. It was constructed as follows: — The insulated conductor, of the ordinary type, had two .separate and distinct hempen coverings. The first of the.se coverings to be wound round the core right-handedl)' and composerl of strands laid up the rever.se way. The second covering was wound left- handedly, and consisted of strands laid up from right to left. Fig. 121 .shews one form of the Trott and Hamilton cable as here described. * The close iron-sheathed cable has, in fact, been practically the form in use ever since the first submarine cable, w ith the e.xception of a few early important Atlantic and other deep-sea lines referred to in i'art I. Bright and Clark's cable compound has been invariably employed subsequent to its introduction in 1862. + This — the lenirth of cable hanging;' vertically in water whose weight will cause the cable to break at the point of suspension -is very usually expressed as the " modulus of rupture " or the " modulus of tension." .Strictly speaking, however, the latter should only stand for the weight it will bear, as a tensional strain, loitliout breaking. I Probably no man has had so extensive an experience as Captain Trott in repairing cables in deep water under more or less unfavourable conditions. ■^ In 1874 ^Ir W. M. Hullivant obtained a patent (No. 1,159) for a very similar type, designed especially with much the same features. 503 SrilMAKINK TKI.l.CKAI'IIS. Unlaying and Laying up of Turns in a Cable. — It was claimed for this airuiigcmcnt tliat tlu- coiUiaction ot" ciliuT covering' after immersion would not only resist any tendenc)' to imlay in the other covering, but would also have tiic effect of ti^ditcniii^' up the turns of both coverinjjs, and so strengthen the cable generally. As has alread)- been pointed out, in the construction of an ordinary iron-sheathed cable provisions are maile for avoiding any torsional twist in the wires when lading u\). Moreover, if such a cable as fast as maiui- factured was coiled direct on to a drum, and if it was possible to pay it out from the laying vessel to its destination from a drum, such a cable should always be free from torsion except when — whilst fixed at some point — it is drawn on to from another poiiU. As, however, any considerable length and weight of submarine cable requires of necessity to be coiled into taniss first in the factory and then Fig. 121. — TroU and Hamilton's Light Gilik'. from there into other tanks on board the laying vessel, the conditions are different. In the first place, turns are put into the cable as the bight is coiled into the factory tank. The.se turns are taken out as the cable is uncoiled from the tank, but put in again on coiling into the tank of the laying vessel.* As the cable is drawn up from the tank on board ship, in the course of ]jaying it out to the bottom of the ocean, these turns again relieve them- selves. This action takes place almost entirely in the short length between the running coil and the hawse-pipe over the tank. As the cable passes through the paying-out machinery, it becomes sub- jected to a strain varying according to the depth of water and the slack aimed at. This strain is at its maximum just outside the stern sheave, and * This was all beautifully described and illustrated in Mr F. C. Webb's now almost classic paper on the " Laying and Repairing of Submarine Cables" {Minutes of Proceed- ings Inst. C.E., 1858). ->-- -:—- ,^..:^-.v— :._ _;.^_..- -._.^- . ; :iL^ C()MI'I.i;ti;|) cAiti.i;. 503 (limiiiishcs as the cable passes out ami sinks to the bottom, at wliich point it arrives slacl<. The effect of this strain is to cause the cable to turn on its axis, or unlay, at the point at which it is at its maximum. This unlayiiiff ^frafhially lessens as the strain diniinishes, until a point is reached where uiilaj'iii^f ceases and laying; up a^ain — or returnin^^ to its iKjrmal state — bcfjins. The cable thus arrives at the bottom practically in the same state as it was when in the factory. It has been contended by some writers — notably by Messrs Trott and I lainilton — that this is not the case, but the experience of these experts was more in re^Mrd to \.\\c f)hi'ini^ up of cables. In this a very different state of affairs exists, particularly in the instance of old cables in which the outer cover- I}; of yarns — laid in the reverse direction to the wires — has rotted away. The effect of pickinj,^ up a cable under a considerable strain is to elongate the lay as the cable comes inboard over the bow sheave. This unlaying continues (if the strain be maintained^ until the lay of the cable may be so much elongated as to cause the core to protrude in places, and the cable, where .slaci^ at the bottom, to form itself into complicated kinks and tangles which frequently break under even a moderate strain. Trouble from this cause frecjuently occurs after a length of cable has been picked up, and the ship stops to splice on new cable. Should she bring the lead at all vertical the cable at the bottom flics into kinks, and — on the least .strain being subsequently applied — a break, or fault, follows. As regards this unlaying tendency, however, whatever the circumstances may be, this should not become serious until the outside .serving has rotted away. In other words, no such unlaying should occur with any form of cable when new — i.e., on being laid for the first time — though some such objection may occasionally apply in the case of a shallow-water cable when relaid after some years. It is contended by some that an outside covering of strong hemp cords, in taking all the working strains, tends to prevent this unlaying action ; and, if so, this places their employment at an additional advantage — besides those already mentioned. Messrs Trott and Hamilton's hempen cable, without any iron wires whatever, was designed with a view to obviating the above difficidties, to which they drew s|jeci.il attention in the course of a paper introducing their cable to the profession generally.* In the author's opinion, however, such objections do not apply until a * " Submarine Telegraph Cables ; Their Decay and Renewal," by Samuel Trott and F. A. Hamilton, y^/;-. Soc. Tel. Eii^^rs., 1884. This paper attracted some attention at the time, and incited an eminently practical discussion. 2 M ■ ;■ - ■-- -" ----. -- 504 SUBMAKINK TKMXIRAI'IIS. cable requires to be lifted, when it is free from the bottom, and the wires, perhajis, partiallj' corroded ; and even then an iron-sheathed cable would, as a rule, be better capable of supporting its own weight without fracture than any unarmoured cable. Considerations regarding Hempen Cables. — At first sight, in some ways, it must be admitted that a hempen cable without any iron appears to be quite the right thing for deep water. At one time it was thought that on account of hemp being so light (in air) that some difficulty might be met with in inducing it to sink. However, like jute, it ab.sorbs water very readily. There would, therefore, on this score be no difficult)' in effecting the eventual submergence of a hemp-clad cable, though it would sink only slowly, and would be liable to be taken, for .some length, out of its direct route owing to any prevailing surface and sub-surface currents. Such a cable should, on the grcninds of low specific gravitj', be good for lifting in deep water ; though, as regards actual weight wet in air, this, by becoming readily " waterlogged," may be .something considerable. One of the great objections raised to hempen cables at first was that it was found to shrink so seriousl)- in water as to strangle the core. Due probablj' to improper construction, such cables were found al.so to unlaj' at quite an early stage of manufacture.* Hy only employing hemp that has been thoroughly shrunk beforehand, and by careful and ingenious improvements in construction (ba.sed on extensive experience), Messrs Trott and Mann'lton certainly succeeded in overcoming the.se objections. The best and most costly (Italian) hemp was used : in fact generall)-, initial economy does not appear to have been one of the points claimed by the authors in favour of their cable, though ultimate economy was. When new, this t\'i)e of cable is probably as well able to sup|X)rt its own weight as an iron-sheathed cable. However, though hem|) alone was supposed at first to be practically indestructible in water, the strength of the hemp in hempen cables is not found to be at all sufficiently permanent — though certainly more so than when combined with iron — to be relied on as the sole medium of strength. It is quite true that iron (even when galvani.sed, compounded and taped) tends to be prejudicially attacked — /.('., corroded — bj- the carbonic acid dis.solved in .sea-water ;t and vv'hen once chemical action sets in here, * Possibly both layers were applied in the same direction. t The significance of the ends of the wires at a break becoming sometimes gradually reduced to needle points is not aUvays certain ; but it is usually, in most cases, considered to imply the existence of excessive chemical .iction, or excessive weakness — in the iron itself or in the galvanising — combined with a severe strain. COMPLETKl) CAHLK. 505 the hemp in an iron sheath rapidly decays.* Still, as hemp has nothing like the same actual strength to start with, and as — even when alone — it materially decays under many conditions, a hempen cable would not probably bear the same strain successfully, in the event of a repair some j^ears after submergence, that an ordinary iron-sheathed cable would. In other words, hemj) lasts better in salt-water when no iron is present : but as there is much less initial strength, the deterioration of a hempen line lying at the bottom of the sea is much more serious, as a rule — though often less in degree — than in the case of an ordinary iron-sheathed cable. This is quite apart from the question as to whether a hempen cable would stand the wear and tear of being dragged along the bottom in the course of repairs. It is also apart frcjm the question as to whether — on account of lightness — its presence would be shewn on the dynamometer sufficiently .soon and with sufficient certainty. Such cables would certainly require to be paid out with a great amount of slack (involving, therefore, an unusually great length in connecting given points telegraphically) to meet the drawback, mainly as regards raising, of a lower actual tensile strength and a greater area for skin friction.f This would naturally have the effect of inducing an increa.sed tendency towards kinks. Though, at first sight, a light and pliable cable might appear to more readily adapt itself and fit into the curvatures, or irregularities, of the ocean bed, this is not ,so actually. Indeed, on the contrary, owing to its low specific gravity and comparatively great bulk, it naturally tends, whilst leaving the ship, to descend in too horizontal a line for good and per- manent laying in this respect. For the List additional rea.son, therefore, in order to obtain a fairly vertical line during paying out — similar to that in submerging an iron-sheathed cable — it would be necessary in the case of the hempen cable to drive the ship much slower, and to pay out a great deal more slack. The question of the applicability in practice of a hempen cable depends, however, very largely on the nature of the bottom, as well as on the existence or non-existence of strong bottom, or sub-surface, currents. The hemp or canvas covering in an ordinary iron-.'rheathcd cable only lasts for any material time in very still water, and is seldom, therefore, of much use * Furtherinorc, tlie ])resence of iron in a cable can, on the whole, scarcely be favour- able from an electrical fault standpoint. Iron being a Ccithode, the tendency is for oxide of iron to be deposited. t Moreover, the surface of the above cable being distinctly rough, the coefficient of friction is further increased on this account. 506 SIHMARINK TKI.KC.RAI'IIS. in quite shallow deptiis. Moving water introduces more decay by bringing a fresh siipj^ly of oxygen.* In shoal water, owing to the strong currents sometimes prevailing, the nature of the bottom is often found to be continually changing. Hence, it will be seen that hempen cables could never be seriously con- sidered for shallow water if only on account of the friction, decay, and abrasion they would be liable to experience, in the ordinary course — let alone icebergs. Comparatively warm teredo- .and fish-ridden shallow waters would also put them outside the pale of practical politics ; for a cable of this description would, indeed, prove a ready prey and acceptable meal to this class of enemy. It is possible, however, that such cables might have a sphere of useful- ness in places where it could be ascertained beyond doubt that no currents existed on the ocean bed. Indeed, under these circumstances — provided also that there was an entire absence of chemical action — a hempen cable would probably last longer than one that is iron-sheathed. Where, how- ever, there is any chance of the line being shifted — and thus getting chafed over rocks by existing currents — a cable of this class would be quite out of the question. It is believed, however, that this type has never been recommended for anything but absolutely deep water. Under any circumstances, in the author's opinion, the " wringing action " referred to would be best defeated — if necessary — by some form of double sheathing of iron wires, each sheathing being extremely light, of opposite lays, and, moreover, of precisely the same length. A length of about 50 N.M. of the Trott and Hamilton cable was made by the Telegraph Construction Company in 1889, and during the course of repairs inserted in deep water in the 1869 "Anglo" Atlantic between Brest and St Pierre. Again, in 1893 a similar length was put in, also in deep water. Both of these lengths were in circuit for some three or four years. The more salient features regarding the question of such cables were ably dealt with by Mr James Graves in the course of a communication to the /ounial of the Society of Telei^niph Engineers by way of discussion on Messrs Trott and Hamilton's paper.f * Thus, in small depths a cable sliould, really speaking, be actually buried m order to avoid ino\ in>,' matter. In deep water, owing partly to the soft nav ire of the bottom, a cable usually buries itself — to a slight extent, at any rate. + "On the Causes of Failure of DeepSe >.. " by James Civaves (/out: Soc. Tel. Engrs., 1884). COMPLETED CABLE. 5or Unless the possibility of recovering, and successfully repairing, hempen and other light cables can be made a greater certainty, it seems doubtful whether they will ever come into practical use, even for deeji water — though very good in theorj*. There can, however, be no question that if some form of light cable were devised which, whilst obviating the various objections — especiallj' that of decay — applying to the ordinary iron and hemp combinations, really possessed the required strength, it would have a great future. In the meanwhile it is general!)' considered more prudent to construct cables which — disregarding initial cost — can, at all events, be safely laid with probably greater lasting security ; and such as nowadays can, practically speaking, be repaired with absolute certaint}'. Light (Aluminium Sheathed) Cables. — In 1893 Mr Edward Bright, M.Inst.C.E., and the author devised a species of light cable which en- Kk;. 122. — liright's Aluminium- Bronze Cable. deavoured to combine sufficient strength with lightness and freedom from corrosion, and such as might be found api)licable for special cases. The main feature about it was that for the ordinary iron sheathing wires of a deep-water cable was substituted aluininium bronze* " in the form of a riband laid upon, or surrounded by, flexible wrappings of hemp flax, jute, or other suitable substance." " In thus enormously reducing the weight and imparting freedom froin corrosion, far greater durability is secured." In this device (Eig. 1 33) the metal tape is applied spirally with an exceed- ingly long lay — varying with the type of cable^;— the length of which is (as in the ordinary wire sheathing) only limited by considerations of efficient binding. Between the metal tape and the ordinary inner, tanned jute or hemp, serving, provision is made for a thin cotton tape (as a sort of " washer ") previously .soaked in Bright and C'ark's silicated compound.! The latter is * Aluminium when mixed with about 0.05 per cent, of silicon or tunjjstan is known as aluminium hronze. + It may be here remarked that, for anti-boring insect purposes, in the preparation of this coitipound to its greatest advantage, a detail of some importance is the calcining of 508 SUHMARINK TELKGRAIMIS. applied with overlap, but one of the main features of novelty about this device is that the more or less thin and narrow metallic riband not only has no overlap, but there is a small space between the edges of each turn sufficient to allow of a very slight " play." Over the metallic tape* another cotton tape may be applied of the same character as the former, and then — where required — a second metallic wrap- ping over that, applied in the opposite direction to the first, but similar in other respects. The breadth of the metallic riband should, as a rule, be about \ inch with a spiral turn completed in 6 inches in the case of a cable or rope not exceeding two inches in diameter — increasing, of course, with larger cables. The low specific gravity of aluminium and its alloys is an obvious point in its favour as against iron for the armour of submarine cables— provided that it will support an equal length of itself, and that it is equally durable. It permits of a m;.^li greater length being carried by a given ship, besides taxing the machinery less, for any purposes to which (as rope generally) it may be applied. Aluminium bronze was selected in preference to aluminium on account of its much greater strength. It has, in fact, about six times the breaking strain, and very nearly the same as that of steel, whilst it has a weight only a third of iron.f Aluminium is only equalled by copper as regards pliability. It will be readily understood, therefore, that this renders it — or any alloy — admirably suited fur the sheathing of a submarine cable. Again, the riband form was preferred in this device on account of the further increased flexibility thereby ensured as compared with that obtained from wires of the same material under similar conditions. It was on the.se grounds, moreover (as already stated), that the metal tape is not allowed to overlap — indeed, the edges do not even meet. Again, such a taping could, under no circumstances, seriously damage the core under tension or pressure. It has been suggested that there might be some difficulty in producing efficient joints in a sheath of this character, and that, in fact, there is no satisfactory method of jointing pieces of aluminium or aluminium alloys. A sufficient answer to this finds itself in the many miles of already existing aerial line compo.sed of this material. the flint clown to tlie finest powder possible to ensure it properly mixing in a permanent manner witli the pilch and tar. * Provision was made for the aliuniniuni sheathing taking the form of 7i'/>Y,f, if preferred. + Thus, it is very largely used by the Post Office (as well as silicium bronze) for overhead telephone lines, especially in instances of very long spans. complp:ti;i) caulk. 509 Further, the durabihty of aluiniiiiiim has been questioned (notwith- standinfT the above extensive system of aluminium hnes), and a comparison has been drawn with aluminium torpedo boats which have shewn signs of somewhat early decay. In re\Ay here, however, it may be pointed out that in the latter case dir (in addition to water) is jiresent, as an oxidising agent, in large cjuantities. This would not, of cour.se, be .so in the case of a submerged cable. T.S. " Scotia" landing the " Eastern Extension" Company's Australia — New Zealand Cable, near Sydney, 1890. APPENDICES. I. LEGAL STANDARD WIRE GAUGE. II. SPECIFICATION OF ANGLO-AMERICAN TELEGRAPH COMPANY'S VALENTIA— HEART'S CONTENT CABLE, 1894- III. POST OFFICE SPPXIFICATION OF ANGLO - GERMAN CABLE, 1891. IV. FORMS FOR ELECTRICAL AND MECHANICAL DATA. APPENDIX I. British Legai, Standard Wikk Gauc;e. I )ecirnal Metric Decimal Metric No. I'lquivnlents. Kquiviilents. No. Ktinivalents. K<)uivalt;nts. Iich. .Milliinutres. Inch. Millimetres. 7/0 0.500 12.700 23 0.024 0.610 6 b 0.464 11.785 24 0.022 0.559 5/0 0.432 10.973 25 0.020 0.508 4,0 0.400 10.160 26 0.018 0.457 3/0 0.372 9-449 27 0.0164 0.4166 2 b 0.348 8.839 28 0.0148 0.3759 0.324 8.229 29 0.0136 0.3454 1 0.300 7.620 30 0.0124 0.3150 2 0.276 7.010 31 O.OII6 0.2946 3 0.252 6.401 i 32 0.0108 0.2743 4 0.232 5-«93 33 0.0100 0.2540 5 0.212 5-.3«5 34 0.0092 0.2337 6 0.192 4.877 35 0.0084 02134 7 0. 1 76 4.470 36 0.0076 0.1930 8 0.160 4.064 37 0.0068 0.1727 9 0.144 3.658 38 0.0060 0.1524 10 0.128 3.25I 39 0.0052 O.I32I II O.I 16 2.946 40 0.0048 O.I 2 19 12 0.104 2.642 41 0.0044 O.I 1 18 13 0.092 '-iil 42 0.0040 O.IOI6 '4 0.080 2.032 43 0.0036 0.0914 ' 5 0.072 1.829 44 0.0032 0.08 1 3 16 0.064 1.626 45 00028 0.07 1 1 17 0.056 1.422 46 0.0024 0.0610 18 0.048 1. 219 47 0.0020 0.0508 19 0.040 1. 016 48 0.0016 0.0406 20 0.036 0.914 49 0.0012 0.0305 21 0.032 0.S13 50 0.0010 0.0254 22 0.028 0.71 1 i Note. — The above gauge was rendered legal by Government in 1884, conformably with a notice issued by the Hoard of Trade, which ran as follows : — "On and after 1st March, no other wire gauge can be used in trade in this country, that is, no contracts or dealings can be enforced legally which are made by any other sizes than those above given, as made by an Order in Council, dated 23rd August 1883." APPENDIX II. An(;lo-American Telegrapii Co.'s Valentia- Cadle, 1894. -Heart's Content SPECIFICATION. THE following arc the lengths and types of cable to be furnished by the contractors, under the foregoing contract, viz. : — • 650 Copper. "^ 400 ( iutla-percha. Type A. Type B closed with 14 No. i (.300) yalvnnised - Type E. 10 No. 2 (.280) galvanised - Type H. 12 No. 6 (.200) galvanised Type I). 18 No. 14 (.083) galvanised. Each wire taped compounded and Total Lengths. N.M. 4 17 347 1,587 1,955 Core. Conductor. (a.) The conductor to consist of a central copper wire, .122 of an inch in diameter, surrounded by twelve copper wires, eacii .041 of an inch in diameter, the completed conductor to weigh 650 lbs. per N..\I., or within 5 i)er cent, thereof, but the average weight per N.M. of the conductor shall not be less than that specified. The resistance per N.M. of the conductor at a temperature of 75' !''. shall not be more than 1.9 ohms. Insulator. (B') I'he conductor is to be insulated with three coatings of gutta-percha of improved inductive capacity, prepared according to Mr Wiiloughby Smith's system, alternating with three coatings of Chatterton's compound, and to weigh 400 lbs. per knot, or within 5 per cent, thereof, but the average weight per knot of the insulator shall not be less than that specified. The resistance of the completed core to be not less than 150 megohms per N.M. after one minute's electrification, when tested at a temperature of 75' F., after twenty-four hours' immersion in water, fourteen days after manufacture, and the average inductive capacity per N.M. tiiroughout the entire length is not to exceed .43 microfarads. Sl'KClKICATION OK 1894 ATF-ANTIC CAULK. 515 (c.) The core of uU the types to he served with a good and sufdcieiU serving of strvintj. jute yarn, steeped in cutch or otiier preservative mixture, and applied wet, the yarn for the deep-sea type to l)e fine spun, of even diameter, and of good ([uaMty. Outer Covekinc.s. (d.) I'ype A. Type B to be served witli tarred jute yarn, and again closed with Omcr fourteen galvanised lili iron wires, No. i li.W'.d., e(|ual to .300 of an inch when galvanised, or within 2A per cent, thereof. I'he wire to be soft, and of good quality. (e.) Type E. 'I"he served core to be covered with ten galvanised liB iron wires. No. 2 B.\V.(;., equal to .280 of an inch when galvanised, or within 2A per cent, thereof. The wire to bear a breaking strain of not less than 25 tons to the s(]uare inch, and to be of even diameter, soft, and of gootl (|uality. (f.) Type B. The served core to be covered with twelve galvanised BB iron wires, No. 6 B.W.G., eciual to .200 of an inch when galvanised, or within 2 A Jier cent, thii "f. 'I'hc wire to bear a breaking strain of not less than 30 tons to the .s(iuare incn, v\ith an elongation of not less than 10 per cent., and to stand not less than ten twists in a length of 6 inches. ((i.) Type i). 'I'he served core to be covered svith eighteen galvanised homo- geneous iron wires, each wire being well covered with a preservative comjjound and ta])ed. The homogeneous wires to be No. 14 B.W'.G., equal to .083 of an inch when galvanised, or within 2h i)er cent, thereof, and to bear a breaking strain of not less than 85 tons per scjuare inch, with an elongation of not less than 4 per cent. The wire to be capal)le of being bent round its own diameter three times, and unbent three times without breaking. The wire to be in l)undles of not less than 2 cwt., and to have but one weld in each bundle. (h.) Before being used for the sheathing of Types A, E, and B, the galvanised iron wire is to be heated in a kiln or oven just sufficiently to drive off all moisture, and whilst warm is to be dipped into a hot compound of coal tar and pitch mixed in approved proportions. Outside Serving. (i.) Types A and E, manufactured as above, to be covered with two servings of Omside jute yarn laid on spirally in opposite directions, alternately with two coatings of'"^"'"'^- Bright and Clark's compound. (j.) Types B and D, manufactured as above, to be covered with two of Johnson and Phillips' patent tapes, laid on spirally in opijosite directions, alternately with two coatings of Bright and ("lark's compound. Genkrai. Ci.ausks. (k.) The cable when completed shall be coiled in suitable water-tight tanks, and c.iiiie to be be kept, as far as practicable, constantly under water. km""' " (l.) The completed cable shall be coiled on board ship in water-tight tanks, and r.inks oil be kept as far as practicable under water until submerged. ■ '"""^ ^ '"'' (m.) The electrical condition of the cable when shipped and also of the completed Final cable when laid shall be such as, having regard to its previous condition, and making rondubn due allowance for the mean actual temperature of the water, as shewn by the resist- "'^ '"'''"=• ance of the conductor, to give no good grounds for believing that any fault exists in the insulator or conductor. APPENDIX 111. H.M. Post Oi'kice TtXEGKAi'hs. Anglo-German Cable, 1891. SPECIFICATION. 1. Conductors. — Each conductor sliall he formed of a strand of seven copijcr wires all of equal diameter, shall weigh 107 li)s. per N.M., and shall at a temperature of 75' V. have a resistance not higher tiian ii/)5 ohms or lower than 11.18 ohms per X.M. 2. Insulator or Dielectric. — Each conductor shall he insulated hy heing covered with three alternate layers of Chatterton's comiiound and gutta-percha, heginning with a layer of the said com])ound, anil no more compound shall be used than may be necessary to secure adhesion between the conductor and the layers of gutta- percha. The dielectric on each conductor shall weigh 150 li)s. per N.M., making the total weight of each conductor when covered with the dielectric 257 Ihs. per N.M. 3. Inductive Capacity. — The inductive capacity of such insulated conductor (hereinafter called the core) shall not exceed .3333 microfarad per N.M. 4. Labelling. Each coil of core before heing placed in the temperature tank for testing shall be carefully labelled with the exact length of conductor and the exact weight of copper and dielectric res|)ectively which it contains. 5. Insulation Resistance. -The insulation resistance of each coil of core shall he not less than 500 megohms per N.M. nor more than 1,800 megohms per N.M. after such coil shall have been kept in water maintained at a temperature of 75 F. for not less than twenty-four consecutive hours immediately preceding the test, and after electrification during one minute. 6. Presen'ation.' The core shall during the process of manufacture he carefully protected from sun and heat, and shall not be allowed to remain out of water. 7. Joints. — .Ml joints shall be made hy experienced workmen, and the contractors shall give timely notice to the Engineer-in-chief or other authorised officer of the Postmaster-( leneral whenever a joint is about to he made, in order that he may test the same. The contractors shall allow time for a thorough testing of each and every I'OST OFFICE SI'ECIFICATION OF 189I ANdLO-OKRMAN CAULE. 517 joint ill till' insulated irougli l)y aicinnulatioii, ami tlic Icai^agt; from any joint during; one minute shall l)e not more than douhle that from an equal length of the |)erfcrt core. 8. Sen'itijf. — Each core shall during the process of straniling he wormed and served (save in the case of the core for the one wire deejj-sea cable, which shall he simply served) with hest wet fully-tanned yarn, sufficient to receive the sheathing hereinafter described, and no loose threads shall in the process of sheathing he run through the (^losing machine. The said yarn shall be spun from the best Russian long-dressed hemn, and shall as regards tensile strength and number of twists be in accordance with the particulars given under the headings marked A. and H. in the Second 'lable. The core so served shall be ke|)t in tanned water at ordinary temperature, and shall not be allowed to n'Uiain out of water except so far as may be necessary to t\-vi\ the closing machine. I). S/wal/iinii. — The wire used for sheathing the served core shall be of homo- geneous iron, well and smoothly galvanised, and shall be in accordanie with the particulars contamed in the First Table. The galvanising will be tested by taking samples from any coil or coils, and plunging them into a saturated solution of sul|)hate of copper at 60 1'"., and allowing them to remain in the solution for one minute, when they will be withdrawn and wiped clean. The galvanising shall admit of this process being four times i)erformed with each sample without there being any sign of a reddish deposit of metallic cojiper on the wire. If after the examination of any particular (luantity of iron wire, 10 \\ct cent, of such wire does not meet all or any of the foregoing re(iuircments, the whole of such nuaiUity shall be rejected, and no such quantity or any part thereof shall on any account be again presented for examination and testing, and this stipulation shall be deemed to be and shall be treated as an essential condition f the contract. In the sheath of deep-sea cable, and in the inner sheath of shore-end cable, no weld in any one wire shall be within 6 feet of a weld in any other wire ; and in the outer sheath of shore-end cable, no weld in any one wire of a strand shall be within 3 feet of a wckl in any other wire of that strand. All welds made during the manufacture of the cable shall be re-galvanised. In laying up the cable the strand shall be spliced, and the ends at the butts bound down with spun )arn instead of being welded, the butts in any one wire of a strand being not less than i foot from those in any other wire of that strand. I o. Compound and Sen'ing — (rt.) For Deep-sea Cable. — The sheathed core shall be covered with three coat- ings of Bright antl Clark's compoiuid, and two servings of three-|)ly yarn, the said \arn being placed between the coatings of compound aforesaid, and being laid on in directions contrary to each other. (/'.) For Shore-end Cable. — The inner sheath aforesaid shall be covered with two coatings of Bright and Clark's compound, a serving of yarn sufficient to take the outer sheath aforesaid being placed between the said two coatings of compound. The outer sheath shall be covered in all resi)ects in the .same manner as hereinbefore specified for the sheathed core of deep-sea cable. The compound referred to in this paragraph shall consist of pitch 85 per cent., bitumen 12^ per cent., and resin oil 2| per cent., and the yarn referred to shall be spun from the best Russian long-dressed hemj), and shall as regards tensile strength 518 SUBMARINE TKLEGRAPHS. and number of twists be in accordance with the particulars given under the heading marked C. in the Second Table, and shall he saturated with gas-tar freed from acid and ammonia, but thoroughly dried after saturation, and before being used, so as to have no superfluous tar adhering. II. Measurement. — A correct indicator shall be attached to the closing machine, and each N.M. of completed cable shall be marked or indicated in such manner as shall be agreed upon between the contractors and the Kngineer-in-chief First Table (referred to in P.\ragrai'h 9 of the foregoing Si-kcificatign) Cable Sheathinc;. Type of C.^lile. Description of Cable Sheathing. 1 Lay to )eep Su.i. be l.eft.haniled. Ini Lay to Shore End. ur Shirath : he Left -handed. OultT Sheath ' Lay to he Left-haiuied. i i ■A Strands : Lay to be Right.handed. Nnmber of Wires S V V Mils. 2 ■0 Is w Ji E 3 z Length of Lay. Number of Stranc = Length of Lay. 1 Number of Wires in each Strand. I >iameter of each Wire. Length of Lay. Ins. Mils. Ins. Mils. In«. I-Wire - 10 280 '3j 10 280 '3i I 2 2 I 3 220 54 3-\Vire - II 280 14 [ I 280 14 1 2 2 1 3 220 Sh 4-\Vire 12 280 •5 12 280 •5 '3 22 3 220 Si 6.Wirc - u 280 !6A 14 280 16^ 14 23 3 220 5i 7-\Vire - 14 280 16A 14 280 i6i 14 23 3 220 5i The 280-mil. wire to havi- a ininiinum breaking weight of 3,500 lbs. and a iiiiniiiiiim of ten twists in 6 inches. The 220-inil. wire to have a minimum breaking wei:4ht of 2,300 lbs. and ;i miiiiiiunn of twelve twists in 6 inches. The diameter of any wire is not to differ from the standard diameter by more than 3 per cent, above or below. 'O.ST OIKICK SI'ECUTC.VTION OF 189I ANGLO-GEKMAN CAULK. 519 Second T.msi.e (rf.fkrrhd to in F-vracraphs 8 and 10 ok the foregoing Specification). Yarn. Centre ('■ A. and Worming. ■,ie Par. S.) Inner .Serving. (Vide Par. 8.) c. Outer Serving. (lide Par. .0.) Ply- - - - 5 7 9 12 '7 .Single Single Single 3 Weight, approximate, in \ lbs. per knot - - / 25 24 28 40 112 13 ' '6 25 10 Twists, ina.viiuiiiu ninnber 1 in 1 2 inches - - J 6 6 6 6 4 II 10 9 6 Breaking' strain, mini- \ nil/.',", in lbs. - - / 175 168 196 280 7S4 i 90 112 ■75 70 The yarns indicated by the approximate weights given in this Table are those usually employed in the various types of cable, and their inininiiini breaking strains have been calculated on the basis that i X.M. of yarn weighing i lb. should ha\e a niiniintini breaking strain of 7 lbs. In the e\cnt of yarns being used of weights dittering from those mentioned in this Table, the same standard, namely, 7 lbs. per "knot-jjound," shall be adopted in determining their niininium breaking strain. For the purposes of the tests for tensile strength the samples of yarn taken shall be not less tlian 26 inches in length. CON'DIllOXS 01 COX TRACT. I . Definitions. In the tender and the several schedules thereto — {a.) The term " ]'',iigineer-in-ehief ' means the Kngineeriii chief of the Post Office. (/'.) The term.s "nautical mile" and "knot" are synonymous, and are used to represent 2,029 lineal yards. (r.) When used in a title indicating a type of calile the word "wire" is, for convenience, substituted for "conductor." 2. Samples. Tl.e samples siihmitted with the tender shall, unless otherwise sanctioned by the 2 N 520 SUliMARINK TKI.KC.KAPllS. Engincer-in-chicf, lie takc'ii as the standards by which the supply in bulk shall be governed. 3. Free Access to Contractors' Works. The Engineer-in-chief and his agents shall at all reasonable times have free access to the contractors' works for the purpose of inspecting the [irocess of manu- facture in all its stages, and of examining and testing every portion of cable and the materials used in the manufacture thereof, and the contractors shall give every facility for such examination and testing. 4. Power of Rejection. The Engineer-in-chief or his agents shall have power to reject any wire or other material used in the process of manufacture which shall appear to him or them to be of unsuitable description or of unsatisfactory (juality. 5. Contractors to provide Accommodation for Testing. For the testing of the insulated conductor during the whole i)rocess of manu- facture, the contractors shall, at their own cost, provide the necessary batteries, and, if required, the necessary testing apparatus, together with a proper and se[)arate room and leading-wires thereto and to the tank or tanks in which the cable shall be stored as hereinafter provided. The contractors shall also provide the apparatus necessary for making the various tests of iron wire and hemp yarn required by the specification. (1. Storage. Each cable shall immediately on completion be passed mto a tank or tanks of water, and shall be stored in the same tank or tanks and be kept therein under water until it is required by the Postmaster-General to be shipped or otherwise delivered, and during such time it shall be held by the contractors tor the I'ostmaster-Genernl under a wharfinger's warrant to be given by them to him for that purpose ; but it shall nevertheless remain at the risk of the Postmaster-General as regards damage by fire. For such storage during any period within that stated no charge shall i)e made against the Postmaster-General. At no time during the occupation of a tank or tanks by cable under this contract shall any cable not the property of the I'ostmaster- General be placed in the said tank or tanks. 7. Nig/it or Sunday iVork. Work under this contract shall not be carried on at night or on .Sundays without the written consent of the Engineer-in-chief or other authorised officer of the Postmaster-General. . rs in the same manner as if such alteration or alterations hail i)een directeil or prescribed by this contract. Provided always, that if such alteration or alterations shall cause any increase or diminution in the cost of manufacturing the cable an ecjuivalent allow- ance in respect thereof shall be accordingly added to or deductetl from the price mentioned ; and if any dispute shall arise between the Postmaster-General or the Engineer-in-ciiief and the contractors as to wiiether any such alteration or altciations iiave occasioned any increase or iliminution of cost, or as to the amount of such increase or diminution of cost, then the same shall be settled by arbitration as hereinafter jjrovided. Provided also, that as regards the length of the cable, the Postmaster ("leneral shall not be at liberty to prescriije any diminution of the length thereof .Xnd that if by reason of any alteration in the method of manufacture or of any increase of length some extended time beyond the date hereinbefore specified 522 . SUIJMAKINI-: TKI.KOUAI'IIS. shall be recjuircd hy the contractors for completing and delivering the cable, the contractors shall be allowed such extended time as the Engineer-in-chief may judge necessary for that i)Urpose. 12. Arbitration. All matters in difference between the contractors and the I'ostmaster-Cieneral which may arise under this contract shall be settled by arbitration in conformity with the provisions contained in the Common Law Procedure Act, 1854, in respect to the settlement of differences bv arbitration. 13. Members of Parliament. In i)ursuance of the Act 22 (leo. III., ch. 45, no Member of the House of Commons is to be admitted to any share or |)art of this contract, or to any benefit tliat may arise therefrom, according to the true intent and meaning of the said .Xct. ^ J**^* Dielectr Resistan- :.\... .-!i./>' Dry. I '!.''• ^ — APPENDIX IV. ELECTRICAL DATA. 1 When Laid. [ year.] Length. \N.A/.] Conductor. [Number and Gaui^c of Wires.] Core Weights. [L6s. per N.A^ Diameters. [.Wis., Inches, or L.S. W.G:\ Average Specific Con- ductivity ok THE Copper. [Per cent.] Electrical Values when L Reduced to 75" Fah. [I'er N.Af.] r Conductor. [Copper:] Dielectric. [G.P.orI.R^, Conductor. Outside Core. [A] Conductor Resistance. Electro-Static Inductive Capacity. ] h * 1 ' -.^ '- - ■' ' ' ■■ __' -' ■ ' . :'/ •'■'''■' ■...'■'■* m. MECHANICAL DATA. 1 When Laid. [Vear.] Length. [A'..l/.] Cahle Type. Core Weights. [Lds. per JV.M.] Inner Serving. [Description.] Sheathing Wires. Outer Serving. [Description.] L Con- ductor. 1 Di- electric. Number and Quality. Diameter [Mils, or L.S.IV.G.] Breaking Strain. [Tons per sq. in.] Av "rage Elonga- tion. {Percent.] Number of Twists. [Average in 6 in.] Circumference [Inches.] PENDIX IV. [Plate XXIV. DTRICAL DATA. Electrical Values when Laid. Reduced to 75° Fah. [Pet N.Af.] Average Bottom Temperature. [FaA.] Signals. Constructed AND Laid nv. [Contractors.] Worked nv. [Owners.] nductor sistance. Electro-Static Inductive Capacity. Dielectric Resistance. Hand or Machine Transmission. Receiving Instrument Employed. Average Working Speed. [Letters per mini] • , '- 1 Engineers.. IHANICAL DATA. Outer Serving. [Description.] Completed Cable. Constructed and Laid nv. [Contractors.] Worked nv. [Owners.] ber ists. Circumference [Inches.] Weight. [Per N.M., in tons.] Specific Gravity. Breaking Strain. [Tons.] Modulus of Tension. [N.M.] in.] Dry. Wet in Air. In Sea Water. Calculated. Actual. ■ , • -_-•■■■- :-■■ ' :■' Engineers. [To face p. 522. }^ PART III THE WORKING OF SUBMARINE TELEGRAPHS CONTENTS OF PART III. CHAPTKR I.— THEORY OF THK TRANSMISSION OF SIGNALS THROUGH CAHLES. PACE Section i.— Prei.iminauv Ri.marks ----- - 5-5 Section 2.— rROi'Ad.vrioN or an Ei.kcikic Implm.sk in an Ei.irTKitAi, Conductor - - • - - - 528 Section 3.— Spkkh or Su-.nai.lim; --■--" 56''> CHAPTER 11.— SIGNALLING AITARATUS. Section i. — Intkoductorv Remarks ..---- 581 Section 2.^Reu\v.s and Special Methods for Disciiarcim; Caiii.es ok MODER.VIK Lencitm .-----■- 5^4 Section 3.— The Mirror Svsiem ------ 592 Section 4.— Siphon Recorhkk Work ------ 604 Section 5.— Other Similar Apparaius ----- 631 CHAPTER III.-DUPLEX TELEGRAPHY. Section i.— Historical Sketch ------ ''^35 Section 2.— Modern I'r.\ctice ------- ^^43 CHAPTER IV. MACHINE, OR AUTOMATIC, TRANSMISSION - - - - 662 CHAPTER v.— RECENT DEVELOPMENTS. Section i.— Working-through E.xpkriments . - . - 676 Section 2.— Phenomena in Long-Distance Cakle Telegraphs- - - 681 Section 3. -New Proposed Methods eor Rapid Cahle-Signai.i.ing and Long-Distance Cable Telephony ------ 685 Section 4.— W'ireless Telegraphy ------ 695 APPENDIX.— "Recorder" Signals under Varying Conditions- - 703 PART IlI.-WORKING. CHAPTER I. THEORY OI' THH TRANSMISSION OF SICNALS THROUGH CAHLKS. Skction I. Picliminary Remarks. SKCTION 2. -Propagation of an Electric Impulse in a Cyliiulrical Conductor : "Curbed" Signals ; The Application of Condensers for Signalling Purposes -Alphabets— The r869 Atlantic Cable taken as an example. Dcarlove's Transformer for Working Cables — Mechanical Analogy of Cable Working. Section 3.— Signalling Speed : Absolute \'elocity of Electricity — Data in Practice— Theoretical Calculations ; Considerations involved : Latest \'iews — F'urther Practical Considerations and Comparisons. Section i.— {'kkliminaio- Rkm.\kks. It will be obviou.s that the commercial value of a submarine telegraph cable is dependent on the si^eed at which sit:,nials can be transmitted throut^h it. This varies with the len^t^th of time a charge of electricity takes to produce its effect by the strencrth of current developed at the distant end— inversely according to the electro-static inductive capacity of the whole cable, and directly so to the conducting power of the conductor. The number of submarine conductors between any two points on the globe being necessarily restricted b)' the great cost of establishment and maintenance, it very soon becarne necessary to di.scover the most advan- tageous dimensions of which to form the conductor and its insulator, and also the most .suitable kind of transmitting instrument so as to work the cable at its maximum speed. The solution of both the.se problems depended on the theory of electric propagation in a cylindrical conductor before the permanent state is estab- 3 26 sniMAKiM. 1 i;i,i.(;k.\1'|i^. lislu'd. In liis (.vk'l)r,itt.'(l " TrcMtisi' mi tlir Matlu'inaticiil I'lu-or)' nt" tlic Galvanic Circiiil," (i. S. Oliin — as far haiU as in 1SJ7 had workcMl out llif f()iri's|)()ii(liii^ (li(Tci\'iilial r(|uati. (i.) Stokes, F.R..S., I'rofessor Thomson pointed out that electricity has no velocity in the ordinary sense of the word. For further particulars, see the " .Mathematical and Physical Papers' of Sir William Thomson, LL.D., D.C.L., F.R.S. (Cambridge University Press, 1884) ; also Phil. Mai;., 1S56. The truth of the above has been set forth recently in a very able manner by Professor W. E. .\yrton, F.R.S., during his lecture at the Imperial histitute on ''Sixty Years of Submarine Telegraphy." Professor Ayrton exhibited a mechanical model illustrating the difference between the sudden opening of a door by a ball projected at it with a certain velocity, and \.\\e t^nidunl ojsening of the door by the i!;radual increase of the pull at the Tlli:nk\- ()|- IKANSMISSION Ol' SICNAI.S 11 1 K( il CM CAIll.l'.S. 527 c\liil)itc(l ;i sys 111 of ascertaining tlic contiiur aiui spi-i'd of (.'iLxtric waves passing tiirou^ii tcic^ra|)h lines, in- incasurin^f tlio |)nii'!nial at different piiiiits alnnj^f its Icii^^tli. In the case of 304 N.M. of coik'tl cal)le, it was fiiimd that the wave travelled at 6,000 N.M. per second. other end of a lon^j piece of india-riihber, tlie latter representing the transmission of an electric si^^nal. l''or an accoinil of I'rofessor .Ayrton's lecture, sec the liiipciiiil Ins/itiilc Joiniiiil for July 1897 ; also XiiUirc, 25th February 1897. .\iij;lii-.\iiicricaii Tcli'i^raiili (■|iiii|Miiy's Suiliim ;U \ ali-iuia, Irolaml : In^triKiicnt Kn.mi. 528 SCHMAKIM. ri,l.l.(.lU- willi its cud v. [•> i-.uth, < .iiin(;(.ti:(l ii|' , al A to u liatlfiy wlwisc (jppoHitc pole in also to >!' I.mhiiIi t/i iii^^\\ j;iuil 1j)' I'liUricf, aiul IH CX)»rt:Hsi'(l thus • IU\. X) IU\,.x) V I' in. in. C -( % H - '/J // //V , . .... ^ ,. / Mil , ,V Am ii mil- I' i|in-'. not cvici'd in m I.; oiini ., .ni'l r reaches from K.OCC to lo/i'H) mcjjolliiiH ; /'•' l/rin;; tliciifurc lii . lii.ni ,^. If W(! l;ilj ^-^^ T=_- logef, - - - - (10) r being expressed in secijiuls if a and L arc expressed in C.G.S. units,* or T= X 0.02915 second - - - (11) 10' where /•stands for the electro-static capacity of the cable in microfarads per naut,/t the conductor resistance pernaut in ohms, and L its length in nauts, T= „ X 0.0201 s second - - - (12) 10" ■' R representing the total conductor resistance in ohms, and K the tcjtal capacity (jf the line in microfarads. * An olim is equal to 10" electro-magnetic absolute units of resistance ; a microfarad is cciual to ,, electro-maLMictic absolute units of capacity. io"> ** ' TIIF.OKV OF TRANSMISSION OF SIGNALS TIIKOUCII CAl'.I.FS. 53' I-'roin this point onwards tlic scries tends towards o, and C, increases ii|) to its limit of value ".which is only reached after an infinitely ^rcat interxal of time. Thomson's Curve of Arrival. — The cur\c I (Fii;. 2) is the "arrival curve"* of a current in a cable, one end of which is to earth and the other end in connection with a constant source of electric jjotential. The times are counted on the a.xis of X, each division marked on this axis corres]jond- x,aa. o,aa X H O as, y. u O at length, attain the same fraction of their maximum charge in the same interval of time, it follows |)ractically from ecjuation fio), that the times necessary for charging cables of different lengths but similar in other respects, are proportional to the squares of the lengths. Equation (5) enables us to construct curves of potential in a cable at different times ' r, 2t, t^t . . . of the variable period. In I'ig. 3, n\ represents the length of the cable, o ^■ the electro-motive force 1',, (jf the battery. I'he curves constantly approach the straight line .\ V, but only coincide with it after an infinitely long interval of time. Fig. 4 shews in the same manner the current intensities throughout the cable at the same instants of time. We see that in the middle of the cable the current strength is scarcely |)erceptible after a time-iJericnl At (shewn by the intersection '^:onnecte(! to the batter)' at A Tsee Fi^', \j for a very short time /,, a.id then at once [)Ut directly to earth, the charj^'e of electricity will accumulate at both ends of the line. The current intensity at the 1! end can be determint-d for any instant b>' pre-supposin},' two states, the first due to the potential l'„ established at A at the inoment from which the times are counted, and the seconfl due to the potential — l'„ 30 T \ 1 M) \ L_ \ 30 |\ \ ^^ \^ ?0 1 1 v\ =^t=^^^:^ ^Si|. to i^^^ M \i^ *^^s^ ^ ^ K \ ' <^ ^5=:^ ~ — ' — 1 '^ l^ ^^ ^ 0.1 0.2 0.3 0,* 0.5 0,6 0.7 0.8 09 X l-n;. 4. established at .\ after an interval /— /,, and calculating' the expression (:,(/)= l''(/)" V(^-f,) in which all values of the function F corresponding,' to ncj.jativr time values will be considercfi as nullity. Grajjhically, this c(vmes to the same thin^' as taking' the differences between the ordinates. of the curve I (sec ]'"\^. 2) and those of a .second iden- tical curve supposed to be moved a distance /, towards the ri^ht. Curves 1 to 7, corrcsponflint( to contacts of res|)ective duration t, 2t, 37, . . . yr, were traced in this manner. As a result we j^'et a sjjccies of electric wave extending' the whole length of the line. 534 SLIIMAKINK TKI.KCRAI'IIS. If the duration of contact were infinitely short, tlie arrival cur\c of the current intensity would be represented bj- the ecjuation dt du dt or, going back to et|uations (7) and (8), 2I' r ' = ^ ."' -.,?.,("■ 4//^ + 9«''- 16//'"+ •• ■) - - (13) This intensity is represented b}' curve II (Fig. 2), and is maximum when -— =i\ that is to sa\-, when dt u - \ du' + 81//"... = which is sensibh' the same as or, b\- equations (7) and (91, as "Curbed" Signals. — Instead of jjutting tiic cable to earth, after a contact of /i duralion with the positive pole of the l)atter\-, it can be con- nected u]j to the negative pole of a battery similar or otherwise to the first. The ordinates of the new arrival curve of the current can be calculated if the .second battery has a potential of the same absolute value — !'„, by adding algebraically the e.xjjression - \\t - /,) to F(/) - F(/ - /,), .so as to have F(/) 2F(/-/,)• Ifthe cont.ict with the negative pole onlv lasts for ,in interval of time /.„ and the cable, at its conclusion, is again imnietliatel)' applied to earth, the definite current curve is represented b\- !•■(/) -2F{/ A) + F(/ /,-/,). For example, if the first contact has lasted 47, and the .second contact with a battery of -P„ potential has lasted ^^t, and if the cable is imme- diatel)- afterwards put to earth, curve 3 in Fig. 2 must be movcfl along upside down to the right as far as the abscisses 47, each ordinate f)f curve 4 being diminished by the length of the corresponding ordinate of curve 3. Thus, in Fig. 5 the ordinate ad is ecjual to ah, less h d, which is equal to the ordinate a c. In this case the electric wave will be re|jresented In- the full line curve. We proceed in a siinilar waj" when the second negative contact is followed by a third and positive one, and so on. i'he full line curves in THEORY OI' TRANSMISSION OF SIGNALS THROUGH CABLKS. 535 Fifjs. 6, 7, 8 represent the waves of arrival due to alternate contacts as indicated in tiic following table, the cable being put to earth again immediately afterward's : — Curves. ., 7 Duration of Contacts. + - 4- - 4T 4T ~ 47 2T ^ '\ / \\ \ / \ ^^ / \ d *> V / \ * <» ,,^^ A r \ '■■ -— -.'. "n > \ — — \ \ \ \ ^., -^ ■^ ,.- ■' * c '^ .'' \ * \ I.'." .' IM<-,. 5. The cable may now be considered divided into sections, containing alternate positive and negative charges. These charges, after a time, run into one another, so that, the contacts being of suitable length, the electric wave will be much shorter than if there had been a single contact only. In this p5 ■'^ 1 1 , \ / . ~iT h - '^\A r Kic. 6. way the cable is brought back much more rapidly to the neutral condition, after the charge due to the passage of the current, and the signals can there- fore be made to succeed each other at much shorter intervals of time. 2 O 536 SUIiMARINK TKl.KCiKAl'llS. SiLjnals obtained by a succession of usually about three to five very short alternate contacts are termed curbed si^Mials in submarine telej^raph)-, the effect of the i)artialiy neutralising' or "curbing" currents being to make the /■ ■•> ^ / \ \^ >« / \ 1 ^-. / \ y *"* ^***.;*. _ / /- \ * **"! 4- pj 'v \ A ^,- V \ \y ^1 ^* ' \ t y * \ ,' / ■^*' 1 Vw.. 7. arrival curve much steeper on both sides of the maximum. A " curbed " signal may be said to be that due to the effect of a current that has been curbed in its strength by the application of an opposite current following immediately after it* — -1 — 1 *' # ''\ // /^ \ t * / •v > 1 ^ ^•. ■. /I / \ 1 1 'N '•-., L^ ^-- ^1 f V 1 "■ ^ >^ . / .- — ..\ ^ ^ ■=^ ■*- r- h-*- N *•••< -— ■ ^<*< 1 \ ,*• ,--' ' \ ^ ^*' 1 *■** Fic. 8. Mr C. F. Varleygave a lecture at the Royal Institution in 1867, entitled "The Atlantic Telegraph,"! dwellip'r somewhat at length on the general * Curbed signals in the recorder or mirror systems ;ire somewhat on the same prin- ciple as the double-current system in Morse signalling ; only instead of the secondary current being such as to almost entirely " wipe out " the signalling current after it has performed its duty in order to clear the line quickly, it merely decreases the volume of the working current -/.c, the current density — thus reducing the amount it does, and therefore increasing the rate at which signals can be effectively made to follow one another, besides rendering each more clear. t Proc. Roy. Inst., vol. v., p. 45. TIIK()K\- OF TRANSMISSION OK SKIXAI.S TllKOlCill CAIiI,i;s. 537 principles undcrlyiiiL,' tclcirraphy tlirouL;h submarine cables.* A^ain, in lcS79, Mr James Graves read a mosl valuai)le |)aper before the Socict}- of Telegraph En|.;ineers on "Curbed Sij^nals for Lon^^ Cables." It may be remarked, in passing, that the .sy.stem of curbint^ sij^nials would be applicable for all cables possessing capacity, though less essential, of course, where the total retardation is low. In practice it is only actually necessary, however, where high-speed working is aimed at. For reasons of traffic, short cables are not, as a rule, worked at thrjir maximum speed — t.e., at that which their elec- trical values would afford if machine transmission devices were resorted to. It is not usually worth while to curb any hand-sent signals, the quickest of which arc not fast enough for this to become desirable. In early days, howe\er, and from time to time, various devices have been introduced for effecting the curbing of man lally transmitted signals — to wit, those of Mr Edward Brailsford Bright (1858),+ ''.ofe.s.sor William Thom.son (1858), Sir * This was some years after the pnpcrs of his hrnthor, Mr .S. A. \^Trley, on the same subject (before the Institution of Civil Enjjineers and the Society of Arts), referred to in Part I. The hitter g^entlcman called particular attention to the fact that the speed of signalling was as much dependent on the electrical resistance of the conductor as on electro-static capacity, and that the said resistance varied inversely as the sectional area. Professor William Thomson, F.R.S., had previously pointed to the real problems to be contended with — partly when criticising Mr Wildman Whitehouse's 1856 B.A. paper, which criticism was conducted in the correspondence columns of the Atheiiatiiii. Professor Thomson here shewed that the rate of signalling would \ary inversely as the square of the length, rather than merely with the length, as had been imagined by Mr Whitehouse in specifying the conductor for the first Atlantic cable. He also pointed out here that with every cable there must be a certain time-period before the current begins to appear at the other end ; and that this time depends onl)' on the cable -in fact on the product of tlie resistance of the conductor into the electro-static capacity, and practically not at all on the battery power. For Thomson's complete theory, see Proc. R. S. + This was the fust suggestion of its kind. Indeed, Mr E. 15. Bright may be saiil to have been the originator of the principle (see his paper at the British Association meeting of that year). Sir C. Bright's device consisted in an improvement on his brother's ; and was, perhaps, the most simple form ever published or patented. This " compensating" or " curb" key was intended to meet the requirements of Atlantic telegraphy by clearing it promptly of each successive signalling current, so as to allow the next one to pass through in t|iiicker succession. The usual plan had been that of first sending a positive current of sufficient duration to produce the signal, and then wiping out the residual electricity left in the cable by a corresponding negative current. It was thought, however, that it would be better to transmit in rapid succession a series of opposite currents of very small duration. By this l)lan the cable is cleared much more rapidly, with a consequent increase in the working speed attainable. Speaking generally, when depressing either lever of these keys, a clockwork train was set in motion, by the releasing of a cam. This sent a series of weak reversals through the line. The order of these would depend on which lever was depressed for the primary current. Sometimes the curlsing, or compensating, current appears to have been set up by the same E.M.F. as the primary current, though in force for a shorter period. This was the case in Professor Thomson's 1858 patent. 538 SUBMARINK TKI.KC.kAI'llS. Charles Hright (1860 and 1862), Mr VVildniaii Whitchousc (i860), and Messrs Thomson and Varley (1866). All of these consisted of keys with cam and train of clockwork wheel devices, forming a part of the transmitting^ key and set into action immediately after the depression of the lever. Such keys were termed "curb senders," or "curb keys." They were, however, never used to an)- extent in practice for the rea.son given ; besides the fact of being before their time, inasmuch as at that period there was no demand for great rapidit}- in working. Mo:-eover the ap|)Iiances, in the shape of the cable and the operators, were not then prepared for innovations, or reforms, (jf this character. On the Use of Condensers * for Signalling through Submarine Cables. — By inserting a condenser at each end, between the cable and the sending and receiving instruments, so keeping the cable comjiletely insu- lated, the signals are sharpened — becoming similar, in fact, to the above curbed signals ; f and, moreover, earth currents through the cable are thereby obviated — absolutely so, if inserted at both ends. In securing greater definition of signals by the u.se of condensers, the speed of working is also increa.sed.* This is owing to the line being by this method sooner cleared of each successive signal, and therefore .sooner ready to take the next, besides that the signals are thereby rendered more readable. In point of fact, in using conden.sers fcjr cable signalling, time is not allowed for the .sending condenser to be anything like fully charged before it is again discharged — only a small fraction of the total charge or current available (from the battery) being, in fact, used. It might naturally be siippo.sed that the above would equally apply if the .same manijiulation of the key (by only momentary depressions) were adopted when applying a * The true definition of a condenser is said to be a storer, or accumulator of, electri'-al energy. This definition does not, however, tend to throw any light on the function performed by a condenser in the signalhng circuit of a submarine cable. t Tiie ajjplication of condensers at each end of the caljle has, amongst other features, so much the same effect as any " curbing " arrangements, that, in the opinion of many authorities, the manual keys and machine transmitters (as used nowadays for high-speed work) do not require to have curbing devices applied to them. \ Indeed, a curbing current (as effected in discharging the condensers by the key) serves the same purjjose as the " wipe-out" current in the double-current Morse system. In both instances the primary current is fore-shortened, and the line is more or less cleared of any residual charge more quickly. It is not found possible, however, to pro- duce this "wipe out" or curbing efiect in any manual key employed for the mirror, or recorder, working at all suited to the nature of the signals, though automatic trans- mitters are, as will be seen, effectively fitted with supplementary curbing devices. TMF.OKV OI- TRANSMISSION OK SIGNALS TMROl'OII CAULKS. 539 l);ittciy (Hint to the cable, but in practice tlic result is quite dilTerent. With a condenser, indeed, it is abs(jlutely momentary impacts, or impulses, which arc in operation.* The sj'stem of inserting condensers at eiich end of the cable was first patented by Mr C. I"'. V'arley in 1S62 (.\o. 3,453), the conarll\- due to the circumstance that the cable requires " clearini; " after every contact ; and this clearing is facilitated by any system of " curbini; " such as is one of the features of the condenser. It is now thouL;ht that condensers at the sending end arc especially desirable, supijlemented, as a rule, b\- condensers in the receivint,' circuit. It is i^encrally advisable that the condensers for this pur|)ose should be of comparatively low capacity, this value beini,' usually a certain pro- portion of tlie total ca])acity of the cable. The object (jf interpolating condensers at either or both ends of the line is to obviate the difficulty of a comparati\el\' long time being required for each signal, owing to the retardation of the line — partly <\uv. to the high capacity involved in a long cable, partly owing to its high resistance. A condenser of small capacity and ])racticall)' no resistance can, however, be charged and discharged (or partiall)' so, at any rate) almost instantaneously and much faster than such a cable could be even very |)artiall\'. This high rate of charge and discharge of the condensers is not materialh' reduced when the said cable forms ])art of the inductive circuit, in which onl^ partial charges and discharges — impacts, or impuf.es, in fact* — are an essential feature. Thus, to produce this effect of rapid charge and discharge most satisfactorily (by rapid primary and "curb" charges), it will be readily seen that the smaller the capacit)' of the condenser to be charged to the desired potential (sufficient to actuate the instrument in question to the required degree) the better — i.c., the smaller the condcnrcr, or conden.scrs, the better, for then the smaller the quantity of electricity (q) necessary to charge it to the rc(iuired potential. Again, the smaller this quantity (<^)) the cjuicker it is replaced or neutralised ';y a corresponding (juantitj' of op|)osite sign, as effected by the curbing current following the primary ("working") current. Signalling condensers require, however, to have a certain amount of capacity, in order to keep up the size of the signals, as well as fcjr maintaining their required (recognisable) character. The manner in which the application of condensers to either or lioth * Hriefly, the eftect of rondensers inserted in ;i cal'>ie circuit is that tlic period of potential rise is fore-slioitened in such a way that impulses only are turned to account instead of a steady current flow. This is sometimes less accurately- thou>;h perhaps more clearly- defined by saying that the " volum>- of current" is citecked by condensers and also l>y special curbing devices. 542 Sl'^MARIXK TKI.l'.C.KArilS. ends nf a cable has the effect of "curbing" the signals may be gathereci from Fig. 9. This serves to illustrate the state of affairs when the i)Ositi\e pole is applied to line at the sending end. When, however, the key is allowed to fly up, a general discharge — ^or rather that which is ordinarily expressed as "discharge" — takes place. In effect it ?.v a discharge; but actuallj-, the following is more precisely the details of .that which occurs: — Sending Receiving + T ^"-^ ' -•-"- /yyy:-:^: 21 I'lc. 9. Electricity of the opposite sign comes u]j fiom the earth and restores complete neutrality by neutralising most of the previous (primary; charge throughout in such a manner as to act r;S a curb to the primary current. Thus it is not only perfectly correct to say that one of the functions of a condenser so placed is to have the .same effect as an arranged for curbing current — following on each primary, or signalling, ■ii;. 10. current — but, moreover, a precisely similar phenomenon is actually invo' d when such an electro-static system exists with condensers in circuit. The nature of the effect of applying a condenser at the recei\ing end is exactly the .same as using one at tiie sending end, for what occurs at one end of a circuit (whether conductive or inductive) will correspondingly, and at the .same moment, occur at the other, there being no beginning or eiul of a circuit. If any change is effected by inserting a condenser at one end, double this change will result from additionall)- inserting one at the receiving end. Tili;()K\' OF TRANSMISSION OK SIONAl.S TilKCJUGII CAlil.KS. 543 Sii|)|)osincr a battery communicates, at a given moment, a charge of positive electricit)- to coating No. I of the condenser c (Fig. lo), an equal quantity of neutral electricity being decomjiosed on coating No. 2 ; the negative electricit)' will be held b\' the charge of o|)posite .sign on coating No. I, and the positive portion .set free will flow through the cable to accumulate on coating No. 2 of the conden.ser c'. Here, again, a quantit}' of neutral electricity is decf)mposed on No. i coating, equal to the positive charge on No. 2 coating, the negative portion being held by coating No. 2, and the positive portion set free to flow to earth through the receiving instrument. Directly the contact ceases, the positive electricity on coating No. I of conden.ser C returns to earth through E ; the negative electricit}' on coating No. 2 of the same condenser is set free, and recombines with the positive electricity in the cable, and on coating No. 2 of c'; lastly, the negative electricit)' on coating Ncx l of C', being in turn set free, flows to A B II II Cable. A' B' c t Kk; earth through e', and the cable recovers its neuttal state; or, as it has been e.xpressed elsewhere* b)' Mr E. Ra)'mond-Barker, a positive charge returns from earth, recombines with the negative charge hitlierto held on c', and thus completes the normal equilibrium of the inductive system of cable and condensers. Figs. II to i8 afford a practical and graphic analysis of the evolution and formation of si|)hon recorder signals on a long submarine cable \\()rked with condensers. In Fig. 1 1, K', K'-, represent a rexersing ke\'. .\, 1!, and .\', B', are plates of signalling condensers C and c' res))ectivel)', at two stations connected by cable. Fig. 12 shews electrical distribution as produced b\' depression of K', which operation connects the + pole of the batter)' to plate A of c. * "Lectures of Mr E. Raymond- ISiukcr," the Moiitlily Correspondent, ^hldeil•a, May 1887. 544 scHMARiM'. ti:li;(;k.\i'ii.s. Merc the 4- 1><'1<-' of the batter}- bciii^ ajimcctccl to A, tlius throws on to it a positive charLje which induces a correspondint^ negative chart^e on l! which is connected to the cable, d posit'^^'e charije beint;' thrown on to A' at the other end of the cable. This positive chart^e which now influences A' inchices a negative one on h', whilst an cc|uivaient positive charge ^^oes to earth throu^di r. thereby causini^ a deviation of the siphon — say, above the zero h'ne, the si|)hon — howe\er loni,^ the key may be kept depressed — faliint;' back to zero when onceC' is fully charged, that is to sa\-, w hen the inductive influence between C and c', transmitted throUL,di the cable, has become complete, the time for this to come about depending;- on the amount of retardation which the induced impulse has met with on its passaije throui,di the cable. Fi;^. 13 illustrates the conditions of electrical distribution as produced by the sub.sequent raisin^^ of \C- after its dejjression. i'his raising; of K' ])Uts ]jlate A of c" direct to earth through the upper A a /I B Record on band *^z:l0^ c Fig. 13. c(jntacts of the kej', thereby discharging from it the jjositixe electricity which had been thrown upon it by the |)r(.-\ious depression of k'. 'i'iie 4- chari^e on A having thus pa.s.sed to earth, the — charj^c on I! of C recombines with the 4- charj^je on .\' of c', whilst a 4- charsj^e comes up, .so to speak, from earth E' throuL^h R to recombine with and to neutra'Lse the — charge which was on H' of (', and causes a deviation of the siphon similar in form to the former one in M^. 12, but in the opposite direction, that is t(j .say, the deviation is now re/oiv the zero line. The siphon aijjain falls back to zero, when the neutralisation, aloni;' the TH1■;0R^' OK TRANSMISSION OK SIGNALS TIIKOUC.II CAMLKS. 545 c;il)lc, l:)et\\i.\t C niul (' has become comijlete, the time for tliis to come aliout deiJcnding, as before, upon the retardation in the cable, it being evident that all electrical jjulsations, whether due to charges or to dis- charges, are ec|ually affected by cable retardation. l"ig. 14 gives the electrical distribution after the de|)ression of K- (in A B A' B + - -Jl I I I h- Cable Record on band E' Fii'.. 14. I'"ig. 1 1", which connects the negative pole of the battery to plate A of C ; whilst in I-'ig. 15 we see the result of the subsequent raising of ■-, which discharges to earth the negative charge on A. Fig. 16 illustrates the result of the depression and raising of k', or A' a' A B' «»— + - Record on bond 4-»/TnV =0 Kir,. 15. "dot" ke\-, followed by the de[)ression and raising of K'-, or "dash" ke)-. In this example the keys have b^en kc])t down for .some .seconds of time, far longer, that is to say, than is necessary for charging the inductive system of condensers and cable. » -- Key kept do^n X Hey kept down K'down up K ' doitn H' up Kk;. 16. As a matter of fact, then, I-'ig. 16 gives the signal ft)r the letter A y" dot" . . . "- the ordinates of a curve such as e c.^, the as_\-m])tote to which would be a straight line jjarallel to the time axis ox and situated at K, distance from it. The insertion of condenser c into the circuit produces therefore, during the charging period, the same effect as an electro-motive force increasing from to E - Ej of opposite name to that of the charging battery, and placed at the beginning of the cable. As similar phenomena take place during the period of discharge, the ordinates of the arrival curve, immediatel)' after con- tact is made or broken, are shortened in gaining proportion as the time < interval increases. We now see w In- the arrival curve is steeper when con- ^ densers are in circuit than when the cable is directly connected to the batter)-, and why it assimilates, on the other hand, to the curve obtained by 1*1' '■• i9- applying a succession of alternating currents of diminishing jjotential immediately sub.sequcnt to the primary "working " current. The increase of speed afforded b)- the u.se of condensers at both ends of the Ikest — Saint-Pierre cable, of 1869, amounted, in fact, to 33 per cent. By the use of condensers, although batteries of increased power become necessary, cables need only be charged, except at the extremities, to a potential actually lower than that which they would have if in direct communication with the battery. For instance, if a lo-volt battery is recjuired to work the receiving instruments through a cable of 1,000 micro- farads capacity, experience shews that bj- inserting conden.sers of 100 microfarads at each end, a battery of 25 or 30 volts is sufficient to ensure transmission of signals through the line. Now it is eas}- to calculate a])proximately, in each of these two cases, the inean value of potential in a gi\en section of the conductor. Vox the sake of cl'^arness, let us take the section commencing at the battery end and extending one-tenth of the total cable length. If the battery is in direct contact with the cable and the latter to earth at the far end, the decreasing potentials — neglecting the 54« srii.MARiN'i': ti:i.i;(;kai'Iis. HI 'HF usually comparatively small factor of loss throut;h imperfect insulation — will be rc|jrcscnte(l b)' a straij,dit line whose exterior ordinates, for the Icns^th of line under consideration, are K and ,"„ ]•",, K representing^ the electro-motJNe force of the battcrj* ; the mean jxiteiitial is therefore ,",/;, I'".. When the cable has a condenser at each end, the e!ectro-moti\e force of the batter}- bein^f increased to 3 K, if O represents the char^^e talsen up on each coatinj^ of the condenser C (FiL,^ 10), and 1', the ^^eneral potential of the cable at the end of the char^nnij |)cri()d, we have Q = (3 li - P,)ioo^ i',(iooo+ 100) whence I'. = i K On the coatini,^ \o. 2, and in the portions of cable nearest to it, the potential will fall durin^^ tii^- first few instants after contact from 3 K U> \ E ; so the potential of the cable at points relatively close to the starting end will soon fall to a much lower \alue than in the preceding case. It is also eas)' to explain the manni'r in which condensers act so as to render the recei\ ing instruments ^ ^' ver\- nearl)- insensible to the effects of earth currents. .-\s tlu'se currents ne\er de\elo]) \ery suddenl)', except - are pr.icticall}- unaffected thereb)', es|)eciall)' as mereh' a strip of pa])er and an infi-rred zero is userl for si^nallin<^ |)ur|)oses at tlie receivinj;- station, in the place of the divided scale used for testing. The quantity of electricity which enters a cable separated from the battery by condensers of variable capacity — the duration of the contacts with the batter)- romainiiiL;- const;int — increases with the capacity- of the interjjosed condensers, without, however, exceeding;- the amount with which the cable would be charijed under similar conditions, by direct connection to the battery. This is easily understood if, usin.n the same symbolic letterini,^ as before, and desij^natint,^ bj' 1' the potential of the second coatin^^ of the condenser at an)- ,L;iven instant duriiiL;' the charijini;- period, and t)\- 1" the mean ])otential of the cable at the same momeiU, we notice that we alwavs t,ret /t(E P)=KF' ']"he limit of V beint;' in fact the mean potential I'j which would he acquired b\- the cable at the termination of an equal char<;int:j period, if in direct connection with the batter)-, /('(IC - P) ha . also for limit Kl',, \\ hat- ever the value of/-. These conclusions are confirmed b)- experiments recenti)- made by M. Bel/, on the various underground and submarine lines connected u|j to the Marseilles ofifice ; t',e results obtained with the 1.S80 Marseilles-Algiers cable beint; shewn L;'rapliicall)- in \-v^. 21. The ordinates represent the enterint; char^fes conqjared with a charge obtained by lent^thened contact with the battery, to which the value of icx) is <^iven ; the condenser cai)a- cities bcini; read off on the axis of x. The contacts were produced with a Wheatstone automatic transmitter, their durations correspondinj^^ to speeds of 150 to 13 turns |)cr minute, varv-ini;' between 0.0166 and o.l 1 5 seconds. The batter)- used consisted of 20 Callaud cells. 550 srnMAKiNi: Ti.i,i:(iK.\i'iis. Kacli cur\L" rcprcsciitiiiL; ;i charj,'c Mas for its asj'inptDtc tlir strai^lil liiu-, paralli-l to tlic axis of x, corivspoiulin^ to tlic cliarj^c actiuircd in' tlic cable uluMi coniK'ctcci direct t(. tlie l)attery for an rt|iial diiiation of contact. With a 35-microfaiad condenser, a capacity eciiial to one-foiirtii of tiiat of the cable, the char^rc which enters the line after a contact of 0.05 second is only about 0.15 of the naviininii char|,'e, that is to say, of the cliarj^a- whicli the cable without condensers would accpiire after prolontj;ed contact with a battery of ^^ ^ =? C'ailaud cells. The stroniiest chars a direct explana- tion of this fact. For the iSHo Marseilles-Al^n'ers cable, t bcin|,f equal to O.020.S second, the time 0.05 second, for instance, corresjjonds to 2.4T nearly. Now we have shewn that, at the exjjiration of the interval t, the .strength of the arriving' current at the far end is practically ;///, and that it is very slight even at the end of a time 2.4T. The quantity of electricity, therefore, which enters the cable at the starting end during such small internals of time must therefore be sensibl)- the same, whatever the conditi(jn of the conductor may be at the far end. The use of condensers offers a further acKantage, as elsewhere ex])lained, in prolonging the life of a defective cable, b)' keeping the fault at a permanent negative potential which prevents corrosion of the cop])er. For the above reasons condensers are nowada_\s almost universally employed. In the early days of submarine telegraphy, before the introduction of electrical condensers, it was a matter of vital importance to obtain some degree of definition and compactness in long-cable signals, the characteristic feature of which ui) to that time had been an undefined waviness, straggling in confused undulation.s. It was abundantly evident that an improvement of this nature, by increasing the speed at which signals could be safely transmitted, would greatl)- enhance the dividend-earning capacity of a cable. l''or this reason much attention was paid to curbing devices, viz., arrange- ments for sending to line a succession of alternate currents of decreasing potential, resulting at the receiving end of the cable in a clearly defined signal. Some of these devices were directly manual, that is to say, the sending ke)' itself was made to transmit curbed signaks, and these have been already ■IIII.OKN ()!• TRANSMISSION ( )K SIONAI.S rilKorcil (Ai'.I.I-S. 551 rctl-ncd to; wliilst in otlicis an clL'cln)-inagni.'tic transmitter, actuutt'd ljy hand-kL-ys on a local circuit, was the cnrbinj^ assent. Later on — in 1 875 — the curl} s)'stein was applied l)y Sir Wilhani Thomson .itid i'rol'e^oi- l''leemii>j^ Jeiikin to their "automatic curb-sender," which is ^'overncrl in its action by the passa.^^e throUL;h the a|)paratus of a jjerforated paper band, after the m.inner of Wlieatstone's automatic transmitter, tiiou^h very dillerent in detail. This apjiaratus was, in fact, the first combination of the "curb ke)- " — various |)atterns of which havt' alread)- Ijcen bricll_\- described — and the Whcatstone automatic transmitter. It was onh', however, used 400 1* 5' »« tk to 74 It to "jti H •.i ^* it }6 »S I! II, SO <6 19 I i Marseilles- Algiers Cable. 1680. MDQ'Ha \im\ rr, ) fur r ifi »e / isu. llta C/i^/e lili 'net "y pro on^d — Jiturnn io SO M ♦0 •■ 60 .. so .. 'eai|»c/ ml out In wm Urn C( ndi ise k| 1 1 1 r~ — i 1 1 I 1 1 -^ 1 1 1 1 ^''1 T Kl 1 J 1 , 1 — 1 o'lis hil Ito.9 s ■- =. '~^ ^_ 1 — 1 — — 07s o'o3 o'37J <■ ^ tf —■ — ' -^ -i 1 - "— ~ — ~ — ' ~" "" ■y^ .5.6^ ,.;- ^ -^" ' ~ " 0} S r^ "^ " —"■ vT I d : w _ I , , , _j Oli J_ _j J _J ^ * 10 l< fO ti to it t> Si SO K (0 els TO IS 10 (4 90 II I0« 100 Ul> ID KU Hi IJO 4 tht capMcily i the capacity Full capacity ofl.Ss cabtt of the Cabta •Ii;. 21. of the cable experimentally for a short timcion the .Aden-Bombay cable , and was never considered to be (juite a success for practical purposes. Thoui^h exceedin_<:;l\' iiiL^enious, it was rather too elaborate for reijular work. Moreover, like the iiiiviiial cwh \' left, left, left, right, left. The curbs are here shewn in italics, and it is cxident that their time-value can be controlled by the electrician who, in his manipula- Fic. 22. — Siplion Kccoiilcr .Sijjuals, Uiu-iirlicd. tion, imi)arts to each contact, main or curb, the time-value desirable. The accom])an\ing figures shew signals obtained uinler exactl>' e(|ual 'conditions, excepting that in i*"ig. 22 the signals are uncurbed, whilst in I'ig. 23 the ;-.ame have been manuall)- curbed in the manner above described. One result, then, of the introduction of condensers for u.se on long cables, with the accom|)anying great increa.se of definition and con.secjuent higher effective speed of working, wa.s to lessen the interest hilhert'j taken in curbing devices — necessaril)' in thcmseKes of a somewhat com])licated Kn;. 23. — .Si|ih(iii Recorder Signals, Ciirlicd nature, with a multiplicity of contacts somewhat difficult to keep dean and reliable. In a word, the majority of cable-station superintendents pronounced in favour of the simple reversing key as a transmitting agent for signals, used in conjunction w ith condensers, as being a perfectly satis- factory .sy.stem which extra curbing was thought to spoil. Of late years, however, keen competition combined with a vast increase of traffic over the various submarine cable systems has caused the matter of curbed signals tf) be again taken up in conjunction with improved automatic transmitters, these latter having been rendered necessary b)* the \ery high traffic-carrying capacity of the two last laid Atlantic cables of i or more distinct and insulated circuits. The transformer is represented in Fig. 35. It is equivalent in effect to 40 or 50 microfarads of capacity. Fig. 36 shews the circuit connections. Cromwell Varley in 1862, and Mr G. K. Winter in 1873, suggested the use of induction coils for a similar purpo.se ; but the improvement claimed in this recent method is obtained by the adoption of the closed S62 suiimarim; ti:i.i:c.kai'Iis. iron ci-'ciiit, and the wiiulin^ of the primary ami sccoiuiarj' circuits — the ratio ,)f the turns can be varied as is found most efficient for the circuit upon which it is used, but in no case must the primary circuit have a larger 6 6 ^fieoorder E E Flc. 36. — Connectidns of Dwirlovt's Tiaiisfcirnicr Syslcni. number of turns than the secondary circuit. Thus no undue strain can possibly come upon the cable end under these conditions, provided that m(jderate battery power be used. '..•''■• -■ .'. :\/"'"'"'""\ .•••'\ .••. Fig. 37. — Signals obtained with Transformer, in place of C'onilensers. Tlie curbing action of the transformer is similar to that of the condenser, and the specimen signals given above shew this to be the case. Particulars. — Line, 7,000 ohms. Cap., 330 mfds. Five cells. Eighteen words. Sending direct to Line with Automatic Transmitter. TI1K0K\ <)l I KANSMISSIDN OK SKJNAI.S TIIKOrciI ( AIII.I'.S. 563 KKM AKKS. 1. Signals with neither sending nor rcccivinj,' condcnsi'is. I' 200 olinis. S joo ohms. z. „ no sending condensers, but receiving on transformer (sh>{htly over-curbed). 3. ,, „ „ „ ''10 inic rofarads (insufficient lurb). 4. ,. .. M " 4" Tlic amount of curb in tlic transformer can be renulalcd by tlic addition of no in- ductive resistance in the primary circuit, or by tlie introduction of a shunt, but it is seldom necessary to use this extra apparatus. The particular transformer used has 5,000 liiriis in the primary circuit (I'), atul an c(|ual ninnber in the secondary circtiit fs), both havinj^ a resist- ance of api)roxiinately 200 ohms. Ihe circint bein^^ subdivideil, tlie instrument is easily ada| -ted to worls either loii}.; or short cables, and can be recommended for use on cables up to 1,200 miles in ienijth. The best results are obtained on this system when the battery is applied direct to the cable as shewn in \'"\'^. 36, but the transformer principle of worUin.L; may be adapted to either the duple.\ or simplex inethf)ds of working. There is nothini^ likely to j,ret out of order or require attention in the instrument ; and the C(jst is less than a fourth of that of a conden.ser of equivalent capacity. Mechanical Analo(;v and Mookl ok Suhmakine Cahle Working. In the course of a series of lectures at the Royal Institution,* Professor Geor^^e I'orbes, I'\R.S., ^^avc a hydro-mechanical analogy for the working' of a submarine cable of certain lenj^^th, and, therefore, possessing a certain factor of retardation, accomjjanied b>' a model + placed alongside of the electrical representation, both of which were in working order. In I'rofes.sor Forbes's model a thread ^^Fig. 38) is sus|3ended in a viscous fluid. A twistint,^ force applied at f^he top represents F.M.I"". ; the total twist in any lenj^th represents the charge in that portion of the cable ; the velocity of rotation at any point represents the current flowing at that part of the cable. A spring at toj) or bottom repre.sents a condenser, whose capacity is measured by the twist (charge) given b}- unit twisting force (unit of F.M.F.). * " Lectures on Alternating and Interrupted Electric Currents," by Professor George Forljcs, K.K.S., M. Inst. C.E., delivered April 1895. t Exhibited a short time afterwards at the Royal Society soiree of that year. 564 SUllMAklM. 11 l.l.dKAI'llS. Hy hanj^iii^f a thn-ad in a \crtical tiilx- filli'd with ^dyccriiiL' and watt-r ill siiilabli- pmixirtioiis, \\<.' have all thi' essentials for uiKlcrstaiidiii^r tlic propa^'atioM of electric pressure through a submarine cal)le. lUit thi- ineasurenuMit of tht twisting; force a|)plied at the top is (liffkult. An)' nieclianism iiaving nioinentuni is objectionable, as this introduces the aiiaioj^aie of a heavy scIf-intUiction, whicli does not exist in the electrical ])roblein. I'Or this reason, Professor Forbes suspended the thread, and ;it each end vanes were sup|)orted which could be blown round by a constant pressure of air to re|)resent the IvM.I". The spindle of the vanes is solid, and goes down into the li(|uid to the point where the thread representing; the cable is attached. I'he vanes and air-jet rei)resent the battery, and it AIR BLAH THREAO smiNo T L fAIITH I coNoenscn oable ' CONDENSER A B represent Earth. Kic. 3S. — .\Ifcli;iiiical AiuUiif.')- nt Suliniariiiij CaMc Wurkinj;. is found convenient to have two jets to rotate the vanes in opposite direc- tions. These are actuated by two keys, -|- and — , which admit the air to one or other of the nozzles. If there be no sending condenser to be represented in the model, the vanes must be supi)orted by a silk fibre without torsion. The vane spindle is held laterally by bearings. Things being so arranged, we may assume that the air |)ressure used repre.sents the E.M.F. of the sending battery, say 100 volts. If the cable which we wish to imitate has Soo microfarads cajjacit)-, the permanent charge on it would be ,. x ioo = o.o.S coulomb. Fixing now the lower 10 ' end of the thread, apply the air-jet and obseiv,- the twist. Suppose TIIKOKN should be represented by, = — , = 2 revoUitions per s(.'C<)nd. Leave 60 X .ooS .4S now the lower end free, and apply the air-jet at the [<, in considering^ the type of conductor and thickness of dielectric which will give the required speed of signalling, or when calculating the maximuin working speed afforded by a cable core of given dimensions, it becomes necessarj' to first arrive at the electrical resistance of the conductor and the electro-static capacity of the cable. With these, and the same particulars regarding a cable giving a known s]jeed, by the use of the above formula the corres]Jonding signalling speed of the cable in question, or the core-t)-pe which must be employed to afford it, may be ascertained. The si)eed of signalling through submarine cables is usually defined as the number of words which can be sent correctly from one end of the cable to the other in a single minute. The number of letters contained in different words of the same language being exceedingly variable, the number of words transmitted in a given time will depend, to a great e.vtent, on their length. It has, in fact, happened during trials, that intentionally formed phrases consisting of very short words have occurred in succession over and over again, and a speed of transmission thus attained very different from the practical working speed of the cable. This state of things is remedied b\' indicating the average number of letters of which the words are to he com|)osed ; the number used formerh' to be five, but has since risen to se\en, as the result of the rules for counting words a(lo])te(l by the international Telegrajjliic Conferences.+ To avoid all chance of nn'simderstandings, most managers and electricians of cable c()m])anies specify, as speed of transmission for traffic pin'|)oses, the iiinnher * That whicli takes place in a cable when put into comnuinica'.ion witli an electric generator has been already dealt with, fairly fully, in the last section. It suffices here to say that the retardation in any given cable is due to the static (holding back) effect of the induced ciiarge outside the cable -a form of Leyden jar on the primary charge in the condui toi-. .Similarly, when the battery contact is broken, and the coiid' ctor is put to earth, a cable discharges itself in the same, comparatively slow, niannr; on the above account. In this case the phenomenon is, for distinction, described as rrolongation. + The fact that seven- or indeed nine — letters is found to be ncaror the average than five in ciihle messages is explained by the circumstance that code words form a larger proportion of the tratfic than in the case of land lines, in which five is still ronsiilered the proper standard number of letters to a word. For the latter reason associated with that of general uniformity— a word is still taken ;is representing five letters in all speed calculations for pur|)oses of estimate and comparison. The cable word is. in fact, only taken at seven to ten letters for commercial estimates and calculations in the direction of e.irning capacity dining given working periods of the cable, and for the return on outlay. 2Q 568 SUHMAKINK 'IKI.KdkAI'IIS. of /(VAvi- which can be sent throujjh tlic c.ihlc per minute, for i^urposes of accuracy, and in order to be more comparable with each other.* This second definition is, however, in one way no more concise than the first. The number of elementary signals forming the (Hfferent letters of the Morse alphabet varies, in fact, from one to four. Thus it becomes neces.sary to state the average number of elementary signals of which the letters are to consist. This number is generally three, sometimes four, the intervals separating both letters and words being neglected.+ The first traces of electricity arrive at the remote end of the cable in an interval of time which is extremely short, though not infinitely so as would ■* The traffic on some submarine lines consists of a very small proportion of code words or cipliers. (.)n the otlier liand, the tratiTic on most of them is mainlx' so consti- tuted, witli words often letteis and over. + It may be suggested that speed of transmission would be more accurately defined by the number of elementa.y sij,'nals -"dots" and "dashes,'' more aptly termed recorder- line "lips" and "downs'' — which can be sent throuj,di the cable |3er minute of time, all signals succecdinj.; each other at equal intervals ; but this idea, though correct from a certain point of view, would scarcely answer in practice. It has already been shewn that signalling can be safely carried on at a speed at which all actual definition of recorder- line "ups" and "downs" will have disappeareil, the value of each letter, or part of a letter, in terms of "ups" or "downs" being given, not in so many distinct waves in the ink-line, but by a more or less prolonged hanging-away of the siphon from the zero posi- tion. This being so, it would not be easy to correctly estimate the speed at which ])racticable signals can be produced on a given cable from the mere noting of the number of meaningless elementary signals received in uninterrupted succession in a given time. •Such data would afford no such criterion of practical signalling as would be oftered by the successful transmission within a given time of a certain number of standard words of seven letters, the words being chosen so as to give on an average, for the total number of words, a mean of about 3.1 elements per letter, which is the mean fot the Inter- national Code. The following list gives ten reiiresentative seve".-lettcr words, of which the total mean number of elements |)er letter is 3.1 — that is to say, equivalent to the mean number of elements \)c\ letter in the entire International Code Alphabet, ii to a : — List. Cockpit. Forceps. Bulrush. Colony. Kedjowl. .Sobbing. Cocoons. Zadkiel. Ploughs. Follows. I'he use of these and other words of similar mean \alue in a trial of speed would gi\e strictly reliable data in regard to the word capacity of a cable. In fact, such a test would be if anything somewhat too exacting, as, from the frec|uency with which the shorter letters occur in average words, the number of elements |)er letter in an average telegraphic message will be found to be something below the value 3. A coml)ination of the theoretically excellent element-unit with the more jir.ictically useful word-unit systems may be arrived at in the foi. owing manner. The total mean number of elements per word in the list above given is 21.8, which TIIKORV OF TRANSMISSION OV SIOXALS TIIROI'GII CAHl.r.S. 569 appear from equation (6) — in the first section of this chapter — which is not rigorously exact. For this reason it becomes essential, on long lines,* in order to increase the nett returns of the cable, to use only the most sensitive receiving instruments, such as Sir William Thomson's mirror instrument or siphon recorder. But the value of C, also dci)ends on the potential T,,, and on the cable constants r, /■, and L. We shall now explain how the best results can be practically assured with a cable about to be laid between any two points, by a judicious choice of battery power on the one hand and a projjcrly pro])ortioned core on the other.+ We will first suppose that similar receiving apparatus is used at each is equivalent to 3.1 elements per seven-word letter, the average for the International Tclej^raph .Xiphabet. Then elements per word = - - - - - - 21.8 Maximum space after each word equivalent to, say, 3 elements = - 3. Total elements per word - - - - 24.8 To arrive at a rigidly correct value for rate of speed of transmission through a cable, let us count the number of elements in the words transmitted in a given time, allowing also 3 elements for every word space. The grand total di\ided by 24.8 will gi\e the total number of standard words transmitted, which value, divided by time in minutes, will obviously give the number of standard seven-letter words per minute, spaces included. For example, the lines — " I am the instrument of msin's desire, To hold communion with his fellow-man In distant fields . . . in other climes afar. Swifter ihan flight of migratory bird — Nay, swift almost as speech from mouth to mouth . . . '' were sent through a cable in half a minute. Xumber of elements in words ------ ^09 Number of elements in intervening spaces at 3 elements per space - 105 Total elements - - - - - 514 ' , = 20.7 standard words. 24.8 " ■' — = 41.4 standard seven-letter words per minute. 0.5 mmute * On the basis that the working speed of a cable varies inversely — more or less — with the square of the length, it will be seen that any slight increase in the electrical constants beyond a certain figure bei;omes a serious matter — more and more so with further increase. Hence, where a high speed of signalling is aimed at, it is most desirable in laying a long cable -if on this accoimt alone— to avoid paying out more slack than is absolutely necessary for engineering reasons. + At the outset it must be remembered, as a ruling jirinciple, that it is more economical to reduce the retardation factor in the formula for speed (already given) by a low resist- ance (R) rather than by a low in(lucti\e capacity (K) — i.e., by a large conductor with just sufficient insulation for electrical and mechanical purposes. This is so in consideration of the relative cost of copper to gutta-percha or india-rubber, but the above principle must not be pushed too far, the limiting feature being fault liability. 570 srmiAKINK TI'I.I'.CKAI'IIS. end — mirror instruments, for instance — so that the same current intensity will be required to make them work. Althoutjh the permanent state can never be establisiied in tlicory, as C, 1', onlj- accjuires its limiting value a = ," with an infinite value for /, yet we have seen tiiat in practice, after an interval of about iot. the arriving; current increases but slowly, and may then be considered to have attained its maximum. Therefore, if we take two cables of similar construction, only differinj^ as to their len|^ths L and L', the arriving current will acc|uire the same limiting value if the potentials P„ and IV are such that or 1\, ;-t: ;-L' 1*„ L p, '~V ft ~^ ■ ^ ^ oaa / "' / ^^ •^ o.aor / / ■^ ^ iX o.*a 1 y v^ ^- / r^ ^ o-aa / ^ V / ^ ^ J — O. 4T 8-C 12T 16T ZOt 24T S8T a2T 36T 401 I'll;. J9. that is, if the electro-motive forces of the batteries em])lo)-cd are j^ro- portional to the lengths of the two lines. If the receiving instruments work under the effect of a given fractional 1', part, saj- .^Vy "^ the current ^.p the times / = ;/r and t' = in' at which the intensity ^^V? is reached, will ha\e the following ratio kr\} K'ger, consequently T -kr\:\ ,, The transmission speeds S and S' in two similar cables, under similar conditions, worked by batteries whose powers are projiortional to their Tlll'.OKN OF TRANSMISSION OK SI(;\A1,S THKOLGIl CAlU.l'.S. 571 cable Icnfrths, are, therefore, inversely (jroportional to the .scjiiares of the lengths of the two cables S _!;» If we consider, for instance, three cables whose lengths are as the numbers 1, 2, 3, connected to batteries of similar kind, the number of cells in each battery varying according to the same i)ro[)ortion, the arrival currents will have the same limiting intensity «, which in Fig. 39 is made cfiual to 100. If, again, the receiving instruments work with a current strength equal to 0.40^, we see by the figure that this strength will be reached in times which ,re 'sensibly to each other as the numbers 1, 4, and 9. If two cables are of different lengths and also of different types, the same current intensity will be obtained when the electro-motive forces of the different batteries satisfy the i)ro])ortion P I' ' or P„ ^ /L ^ R p; r'\: R' The electro-motive forces of the batteries should thus be j^roportional to the tcjtal resistances R and R' of the two conductors. The times / = ;/t and /' = /n' at which the same fractional part, J^,a for instance, of the current intensity reciuired to work the receiving instruments, is reached, w ill be lo each other as T -^■r log4 whence f _k r l£ _ RK The transmission^speeds'T' and v are therefore S ^/6 r'L^'R'K' ^~ k' r L- " RK If the cores of the tvvojcables are composed of the .same substances, d and D, d' and D' repre.senting the respective diameters of conductors and cores, we have 1 1^ ^-d-M^ 572 SLIIMAKIXK TI'.I.I'.I ;K.\I'I1S. and, letting A stand for a constant, determined experimentallj', which varies with the nature of the receiving instrument, log^ S = kd^ J j signals per minute.* According to numerous experiments of Mr Willoughby Smith on cables with his improved gutta-percha core and with conductors containing 95 per cent, of pure copper, when mirror receiving instruments or sijjhon recorders are used, A= 1297 X 10° Therefore T297 X rt^ X log X lo'* S= „ ' signals |)(jr minute, D and (i being expres.sed in terms of the same, but any, unit, and L being expressed in X.M. I""or a cable with a dielectric composed of another material, the constant would have to be multi]jliecl by the inverse ratio of the capacities per N.M.-*- of die given cable and the cable with the aforesaid Willoughby .Smith gutta-percha core, the diameters D and (^/ remaining the same.* By applying this formula to the 1869 French Atlantic cable, we find that 5 = 232 signals or about 58 letters per minute. * For purposes of reiidy calculation it is also well to remember that if a constant ratio be maintained between the wei;;ht (or diameter) of the conductor and insulator in the two cables, tlieir relative speeds — provided precisely the same materials be used — will alone depend on their relative core dimensions and lenjjths. This is, of course, assuming the same conditions as regards bottom temperature, pressure, etc. ; or that any difference in this respect will be allowed for so far as is necessary. + Throughout this book "N.M." or "naut" are used as abbre\ iations for "nautical mile." The reason for this choice in preference to "knot" has been explained in Parts I. and II. \ Willoughby Smith's " improved " gutta-percha, introduced in 1870, is taken as the standard dielectric throughout this chapter. Firstly, because it is the material of which the dielectric is composed in by far the greater length of cable at present in use at the bottom of the sea. .Secondly, owing to it having a substantially lower capacity than an\- of the other "ordinary" gutta-percha so far produced, a core so insulated permits of a correspondingly higher s])eed. An india-rubber dielectric for the same reason permits of a still higher siieed with corresponding dimensions, but on other accounts has only been employed on a com|)aratively small scale. Thirdly, the ditferent forms of "ordinary" gutta-percha as manufactured by various contractors at one time or another with different available materials yield distinctly varying results as regards capacity — and therefore, as regards speed. On the other hand, the capacity of Willoughby .Smith's gutta-percha being governed so much by the methoti of manufacture 1 referred to in the chapter on (iutta-percha, I'art II.) naturally forms a much more uniform basis. The comparati\e specific inductive capacities of the above different materials are given in Fart II., and the working speed with each bears the same ratio to one another under similar conditions and with dimensions common to all. rilKORV OK TRANSMISSION OF SICNALS TIIROIOII CAULKS. 573 In a general way Aj being a new constant, R and K expressing in ohms and microfarads respective!)- the total conductor resistance at the tem|)eratiire of the waters in which the cable lies, and the total capacity of the cable. Data in Practice. — According to Mr Willoughby Smith's experiments, A, would be equal to 108x10'. On the other hand, Dr Alexander Muirhead in 1883, obtained through the Jay-Gould Atlantic cable of 1881, between Penzance and \ova Scotia, 7,288 letters in 81 minutes, including repetitions and comparisons, say about go letters or 270 elementary signals per minute. The length of this section of cable is 2,518 N.M., the conductor resistance R at 75 F. 8,320 ohms, and the capacity K of the cable 939 microfarads. It was constructed bj' Messrs Siemens Brothers, and, there- fore, the dielectric is of their "ordinary" gutta-percha.* The temperature at the bottom of the Atlantic being about 37 \\, the value of A' deduced from these data is .A.' = 2 1 o X 10'. Dr Muirhead has also given the s]jeed on the corresponding 1882 Jay- Gould cable as 18 (seven-letter) words per minute. Tile Marseilles-.AIgiers cables of 1879 and 1880 give regularly during simplex wurking, with sij^hon recorders and automatic transmitters, 150 letters |)er minute, each letter recjuiring on an axerage four current im|)ulses. * Messrs Sicniens IJiotliers devised special arranj^ements in the matter of the core of this and some other of their lonj;' Atlantic cables, with a \ieu' to increasing the attainable speed of signalling. The conductor of the cable at each end for some distance was of a larger type than in the middle so as to reduce the conductor resistance, the latter — from a manufacturing standpoint— being the more economical direction to work in for effecting this oliject than by reducing the capacity. The weight of dielectric is also not only less but, moreover, its //lu/ciicss is less than in that part of the core in deep water (besides the material being somewhat different) where — on account of the increased pressure added to the greater difficulties and expense of repairs — extra precautions arc necessary for ensuring a |)erfectly reliable insulation resistance. Thus, in the first Jay-tlould "Atlantic" of 1881, the deep-sea portion was furnished with a core represented by 350 lbs. copper per N.M. to 300 lbs. gutta-percha ; whilst that for the ends was constituted by "^^ ..— -" This device was in accord- ^ 270 lbs. (..P. ance with the notion that the rate of charge anti discharge in an insulated conductor is mainly governed by its form at the generating end. It is not believed, however, that in practice any ad\ antage was actually found ; moreover, the heavy conductor and small thickness of gutta-percha at the shoreward ends materially increased the risk of a (lecentraMsed conductor causing faults. This plan has, therefore, since been abandoned in moie recent cables made bv the above firm. 574 SUHMARINK TKI-KCKAI'IIS. Tlic resistance of these cables, at the temperature of tlie deep Mediterraiiean water (55^ F.), bciii^ respectively 5,350 and 5,220 ohms, and their capacities from 136 to 129 microfarads, the a|)i)ro.\imate \alue of A' A' = 43 X 10". Modern fast-s])eed ocean telej^raphy is represented by the two last Atlantic cables laid in 1S94, one the iJro|jert)' of the Commercial Cable Coin|)an\- and the other that of the A ni^do- American Telegraph Companj'. JJoth of these cables are entirely worked by machine transmission, full descriptions of the \arious systems and instruments of which will be found at the end of this book. The y ^ . on the first-named cable, with a core composed of a cop|)cr conductor that weii^hs 500 lbs. |)er X.M., with a thickness of {^utta-pcrcha insulation represented by 320 lbs. per N.M., is .said to be from 37 to 40 (fi\e-letter) words per minute. On the second cable the ordinar)' workinj.^ speed attained in practice Hay automatic trans- mission j is as hij^h as 47 (fi\e-letter) words ])er nn'nute, press work bein^i; .satisfactorily carried out at a corresponding' rate of 50 words ])ei nn'nute.* Fi;j;. 40 is a facsimile of sit^nals received at Heart's Content .station with automatic machine transmission from Valentia b)' means of Mr Herbert Taylor's latest automatic instrument, and with duijlex connections in circuit. V'yj;. 41 rcjjresents specimen code siijnals received at J47 letters ( =49.4 five-letter words) per minute, with Mr I'. B. Delany's automatic sender. .Speeds of 250 letters and over have, indeed, been maintained in rei^ular traffic over this cable for half-an-hour (and more) constant working-. These .speeds were carefully checked at each end by the company's officials. This, the last Atlantic cable laid (one of fi\e, more or less, workin^^ cables belonj^in*^ to the " Anj^lo" Companyf), may, certainly, be taken as the re]jresentati\e of the most advanced sta|.:jc of cable working in the present da)'. It need hardly be .said that both of the above lines are in\ ariablj- w orked duplex. Thus — in the.se days of " double-block," etc. — the speed is in- crea.sed by 90 per cent, i.e., their working cajiacity is nearly doubled. The conductor of the "Commercial" cable is built up, according to Messrs Siemens' invariable custom with Atlantic cables, by a large central wire * Tlic theoretical speed of this cable, with a KR of 2.42 x 10", based on Mr Dearlove's "Tables" elsewhere alluded to, woukl be 48.8 (five-letter) words per minute. t This company is by far the largest of the Atlantic companies, having requisitioned no less than eight Atlantic cables altogether, three of which, however, have fallen definitely out of use- /.£'., those of 1858, 1865, and 1866. The "Anglo'' Company comes only second to the " Eastern " as regards total mileage of cable. [Pl.ATK XXV. v .^ ) } * ^ < tt <> '-» s 1 c k^ 6 H "-» ■.i ^ ^ c 1^ hi •I > : (i "^ '■. (. « * ■■'. ti S> ■-; d e ('' 1 * .•• * ''. ft, »» ■■■■ «t <> '^ '\ , si Q ;i '^ > C K. Id «) w \ e « «> « c a c . -r rcsistaiiCL" is to altrr tin- form of tlu' electric waves, but their first effects are propa-ated with the same uniform velocity which tin-)- would havi- if tlu- resistance was nil. In tliis sense only lias the expression " ahsohitc speed of clectricitv' " any si^'nification, and we then see that this vi-locit)- is comparable to that of lij^'ht. As the expression A, ^ A ' RK rk\} does not correspond to data furnished in practice, \\c shall substitute for it the fol lowing formula — rk\l I.J A and A, beinL,^ two new constants which should be determined experi- mentally from a sufficient number of observations. Coiifinini,^ ourselves to the two particular cases referred to above, wc find that A = 826x 10' and which ''ivcs A, = 2769 X 10^ S = — - ( S26 + *■' '^° ) 10' signals per minute. rk\,\ I, / Theoretically spcakin;^^ the ma<,metic induction introduced by the iron sheathiiiL; of an ordinary cable should tend to have a slij^htly beneficial effect on its working powers. This would be owing to a tendency on the |)art of the i)i(r' have their own special tables for this purpose, as well as to meet other similar objects, with constants based on their own material, etc.- — which, indeed, require to be adjusted by change (jf materials available from time to time. Such tables usually also include fas a part of the story) the diameter (d) of the conductor, the external diameter (d) of the entire core, and the relation of the twf), besides the electro-static capacity of the core. It would be of little use to present one of these speed tables, etc., as a specimen, for it would be only applicable at the time for the |)articular material it is ba.sed on and with the particular constants used. However, with the formula and the basis for constants, any table can readily be draw n up. The working speed In- the mirror or siphon recorder is limited b\- the rate of transmission. The jjractical limit of .sending speed which a good operating clerk can keep up on these systems does not usually exceed 135 letters ])er minute. With automatic transmission, however, a speed of 600 elementary signals per minute has been reached on certain cables. ■*■ The length L of a cable being a given quantity, it seems useless therefore to diminish r and /' below values whose product is less than ''•^^,(-'-'r)- The electro-static capacity of vulcanised india-rubber cores being about 2 jjer cent, less than that of cores comi)osed of W'illoughby .Smith's improved gutta-percha, the speed of transmission through vulcanised india- rubber core cables for eijual dimensions is greater in the same p-roixirtiun. taping each core in a nuiln|)lc-(:()n''iu;tor cable, in place of a single ta|)ing for the whole when laid up with jute, or hemp, worming. I'his nlan was first resorted to, witii some success, by H.M. Postal Telegraph Department on the 15arton-I!orkuni cable of 1896, the application of the principle to siibiiiarinc telegraphy being originally suggested by Messrs Dresing and (iulstad. With a \icw to partially neutralising electro-static induc- tion by the magnetic induction between the taped cores, Messrs Felten and (iuilleaunie had independently ado])tcd the above plan for undeigioimd land wires, as well as Mr Fleece at a still earlier date. * "Tables to Find the Working Speed of Cables," by Arthur Dearl()\e . Iv and I'. X. .Spon). + Indeed, practically speaking, the speed by machine working is only limited In the electrical equivalents of the line. Tlll.dKN' OK TRAXSMISSKJN (JT SKINAI.S TIIKOUCll CAIU.I'.S. 579 Further Practical Considerations and Comparisons. — Durint,' trials of short duration, very skilled o]jerators have obtained with the mirror instriiinent a rather hiijiier specrl * than that afforded by the siphon recorder, but the practical workini,^ speed of the two forms of apparatus (if worked manually) is sensibly the same for reasons already i^iven. By ordinary li.iiul tr.in^uiission this averai^res at twenty-five words per minute for more or less continuous workini; of several hours by efficient o]jcrative clerks, and thirty words per minute at a maximum for comparatixely short periods of time. The Morse printing instrument, where the electrical \alues of the cable come into force, skives a speed of transmission one- fourteenth that of the siphon recorder. It can, indeed, onl\- be used on cables below 400 miles in leni^th,^ and then only when the weit^dits of co])per and _L;utta-|)ercha are not less than 107 and 140 lbs. ])er X.M. respectively.;); In combination, howexer, with certain relays — ncjtably that of Messrs Allan and Brown — it works at a much hit^her s|)eed, and can then be used on cables considerably lonijer than 400 miles — u]j to .something like double the length, indeed. I'"rom what has transpired it will be seen that a clear distinction must always be borne in mind between the maximum speed (jf manipulating a key on the Morse and mirror (or siphon recorder) system and that which the cable will permit of The Morse key lends itself to a slightly higher speed of working — in words per minute — than the double lever key of the siphon recf)r(ler (or mirror) system, notwithstanding the difference in the duration of contacts involved by dashes. ]?ut the length of cable which will "take" this speed is in the Morse system much more limited, even where "double current" and relays are employed. If a higher sjjeed of transmission is adopted than the retardation of the line allows, the result is that the signals on any existing instrument § get blurred into one another * Sonietinics up to tliirty-five (five-letter) words per niinute at a spurt. + I'nlike the case of mirror or siphon recorder Jiand transmission, first-class mani- l)ulators can work the Morse key at a rate as high as the fastest writer, /c, about forty words per minute. Where such a speed as this is aimed at — and an "ordinary" speed of thirty words — the length of cable (with core) which can be worked b\- this system 140 ' ' would not i)e more than about 200 miles, with an ordinary .Siemens ])olarised relay. I If ordinary Morse instruments were used on the Atlantic cables, it would take about five seconds from the time of battery contact until the relay at the distant end be- came suflTiciently magnetised to record a tirm signal, with the result that not much over one word jjcr minute could be transmitted. ,!^ This all |)oints to the circumstance that it is in the type of cable rather than in the signalling apparatus in which any radical change should be looked for, if we arc to make any rcNolutionary increase in the speed of transmitting thought across the ocean by electrical conductors. ;8o sniMAKIM-. TKI.KCiKAIMIS. before arrival at the other end. Tims it is that on a lout;- len<4th of eable the sj^eed at which the Morse system can be successfully worked is but a fraction of what the mirror or sijjhon recorder would take. On the other hand, it '\s possible to work any len_i,fth of line at some speed — however slow ^by the Morse system, provided the battery contacts are made in suffi- ciently slow succession and sufficiently lont,^ The same applies to any instrument amenable to electro-telet,n-a|jh)-. In man}- cases it mijjht seem, at first sight, that a cable affording the ma.\imum speed was wasted on short sections — especially where only second-rate clerks are emploj'ed, or where the traffic is such as onl)' to necessitate the breaking in of each station for an hoiu' or so ])er da)-. These lines, however, are almost invariably worked throughout their entire length — b}' joining u]j all the sections — at certain periods, and here the maximum speed is usually required.* * .\s a rule, a coast cable of this description is laid mainly in order to bring the extreme points into communication. It is, indeed, usually only landed at the inter- mediate spots for the s.ike of subsidies, or y;uarantees of local traffic — at least sufficient to co\er station cxjienses ; as well as to simplify working;, testing, fault localisation, and repa.rs. Tlic Cummercial Cable Compiiny : Station aiul (,)iiarlcrs near Ca|iL' C aiiso, \uva .Scotia. ri-JAPlER l(, SlGXAfJJNC APPARATUS. SrciipN I. tfiiroductory Reinaiks. Sk'.tion .•• S pi 1 1,-1 1 Mi-thijils for IJisdiar^iriii Cnliles : l)ibch,irji;ing Kelus • \tivi.:,-{. • r)lschniij(; f ',)ik ; Hughes' Priniinij Apparalu'. ^vilh Ilibi iiai>;r: . Prowii Allan kt-l.t.. SlCll'iN' ;. Miiror Rerciving liistrunii-iit : Siispfiiclcd Coil Mirvor. Staiiiin I Hi;!. illation : rr,in.-;ii\ittiiijK; Keys: F.arth Co'incriion : Arr:in>;cments J'>r Keijoidiiig Mtfsaai.'cs at the .Sondir.;; End ; S;uukUts' Key--Cro -iJenianiin .Smith's Switch Key and its Coinicc lions ; Manual 1 ranal.ition : Raymond Parker Tran.statinf.; Key Oickenjon's Trans- laitti'iu Key and it.s Connection.*. Si'XTRW 5. —Oilier similar Apparatus; Laurilzen's Utidiiiator : Tlv:: Uextrineur Siemens' I'ertnanenl Magnet Relay • Adcr Record(;r, SkMIOX l.--lNTKOt)Ut:TOKV Kk.makks. 0.\ .'.^hort siibtnariiic cables nies.saj^c.'^ an- intcftilian^ed by inc.xii.s of Morse or llu;_;hcv iiislriiniciits, workoti (iitcttly by the current thrtnigh tlu' line, 01 fist: with Ihv hol|j of rolay.s. When thu rabies exceed SOJ miUjs or so in Icn-^'th, and it Ix;coiTif-. ncccssar)- lu use nT.'rc .-ciisitivt! apparatus, recourse is had cither In tlu- iniiror r»'cc'iviiig inslninicnl, which <>nly af)ur;ths .dfscribird further on) have since l.)een (gradually iritroducid in place of the Morse instrument. At the ptesent tinie, the " Indo-European" and the Direct Spanish linft are the only crrctiif* 3K >Ho SUBMAKIXE TKLi bcf<;)n; arrival at the other end. Thtf* it js th»>'t ■ • • '"'iiith of cable the spRed at which tht* Morse system a*. ..!•«■. ^h» 'k(td is but a fraction of what the ininor or siphon rec.^ti. >: On the other hand, it \s po'ixihle to work any lonjith of lirir *^ -rM ^fnftc »Ju>vvever slow — by the Morse system, provided tho bitter.* ■ .-:• •►, <■ -^^.j v\».<\tt in suffi- ciently slow succession rind sufficient!) hrl-;;, i^v'..- ViiflH' iifiies to an)- instrument amenable to elcctro-tc!ef,'rapli; • , In many cases it mitfht seem, at firs! -*iiAi, ttei! ' '■.(bk idlording the maximum speed was wasted on short ?!cc»»^, :■ r^h as only to <• ;■• f ,1a)'. These "iHc'i- entire length '♦ijrr (We maximum * As a rule.-, a coast ( ;>ble of tliis '.lescriplmv •- J«rt ruftfi '.-' ■ -"^Mf; 1<> brin^' ihe extreme points into ronnnunicrnion. It i<, in'!' '-y :n)H i-.^if^ vl She inter-. mediate spots for ihi; s.ikf. of subsidies, or jiUari. > li i;at''-i -v '.^Wal sut'ficiiMit to rover station e.xpensi-s ; a? well as to simplilv "nii^ieiT". <^tfry ; .--»..ii CHAPTER II. SIGNALLING APPARATUS. Skction I. Introductory Remarks. Sl-.CTION 2. .S])ccial Mctlioils for Discharging Cables: Dischargin;,' Relays: .-Xuxiliary Discharge Coils : Hui^hes' Printing .Apparatus with Discharge : Brown-Allan Relay. Skction 3. Mirror Receiving Instrument : Suspended Coil Mirror. .Station Installation: Transmitting Keys: Earth Connection: .\rrangcnients for Recording Messages at the Sending End : .SauncU-'rs' Key — Crookes' Radiometer for Recording Mirror Signals as Received. Skction 4. 'I'lionison Siphon Recorder: Electro-Magnet and Coil: .Siphon: Inscrip- tion of Signals — Electric Mill -Vibrator- Later Patterns of Recorder. Installation of the .Xjiparatus and its Connections at each End — Permanent Magnet Recorders : Direct Writers — Benjamin Smith's Switch Key and its Connec- tions : Manual Translation : Raymond-Barker Translating Key — Dickenson's Trans- mitting Key and its Connections. .Skction 5. — Other similar .Apparatus: Lauritzen's Undulator : The De.vtrineur - - -Siemens" Permanent .Magnet Relay : Ader Recorder. Sl-X'TIOX I.— IXTKOnUCTORV RPM.XRKS. On short siibniarinc cables mcssai^es arc interchanged b}- means of Morse or Huj^hes instruments, worked directly by the current throu,L,fIi the hne, or else with tiie hel]) of rela)\s. When the cables exceed 500 miles or so in leno;th, and it becomes neccssar)- to use more .sensitive apparatus, recourse is had cither to the mirror icceivinL,^ instrimient, which onl\- affords transient sii^nals, or to the Thom.son siphon recorder, which automatically inscribes the signals on a strip of paper, with a sensiti\eness to current about e(]ual to that of the reflecting instrument.* * The heavy patent rights attached to the siphon recorder— involving a royalty of 10s. per X.M. — having expired in 1882, special patterns suited for short lengths (described further on) have since been giadually iiitroduced in place of the Morse instrument. At the present time, the " Indo-European" and the Direct Spanish lines are the only circuits 2 R 582 srr.MAKiNK ti;i.i:(;kapiis. When, as usually, the tclcL;ra|)h oftlce is at a distance from the cable landing-place, coniminiication between the two is estaljlishetl by means of underground lines laid in a trench, or running through pipes. The con- nection between the shore-end and land-line conductors is made in the cable hut,* one or more lightning jjrotectors being here inserted to pnjtect the submarine cable from discharges of atmospheric electricit}'.-^ Should the offices be too far removed from the landing-])lace to jiermit of the instruments being connected up to the cable through land lines, the messages are received and sent from the cable liut itself — suitably arranged for the jjurpose — traffic to and from the cable hut being carried on through overhead wires. In other cases the cable is joined up to the aerial line b\- means of rela\'s placed in the cable hut or in the nearest office. Kela)'s are also inserted at times between two sections of a submarine cable in order to avoid the necessity of retransmission.;): Some of these instru- ments,^ such as Siemens' polarised relay, the relays of Stroh, D'Arlincourt, Froment, and others, are well known, and dcscrii)tions of them to be found in all works on general electro-telegra])hy ; others again, such as the Brown-Allan rela)', belong more particularh' to submarine telegraphv. worked on the Morse system. The advantage of a record being obvious, the mirror instrument has similarly fallen out of use almost entirely, Ijeing only emplo\ed liv the "Western and Brazilian" and the "West India and Panama" companies. In the author's opinion, however, the "mirror" should always have a sphere of usefulness during cal^le ojicrations, if only on account of its extreme convenience in portability and simplification of adjustments. In speaking between ship and hut through a "shore end" a sounder could, in some instances, be still better turned to account. If made more sensitive, the latter might even be used for somewhat longer lengths. * A device of the author's for ensuring this being i)ermancntly maintained was fully described in The Electrician of April 1897. t Having regard to doubts as to the nature of the phenomena, some two or three guards of various descriptions are a wise ])recaution - for instance, one of IJr Lodge's, supplemented by a Saunders, Jamieson, or IJright protector, as well as by one of Siemens' plate guards. The latter (fully described by the author in vol. xix., p. 392, of the Journal of the Institution of lUectrical finjj^ineers) is i^erhaps best suited for an unfre(|uentcd hut, inasmuch as when one wire is fused another comes into the circuit automatically. \ This forms what is usually described as the Morse repeater, or translating, system, extensively employed in land telegraphs. ,!i The above relays might become more generally useful if rcnilered efficiently acoustic. The delicate adjustment at present rn|uired to work the Morse coils would thus often be a matter of secondary importance. This would often be a great advantage for temporary operations where time is of the utmost importance, and where a special local battery may not always be available. !| To wit, Culley's " Handbook of Practical Telegraphy, " and I'reece and Sivcwright's "Text-Hook of Telegraphy." Both of these are publishetl by Messrs Longmans, (ireen, and Co. They also fully describe the Morse recorder and the Morse (or \'ail) sounder. SIONAI.I.INc; AI'I'AKATrS. S83 W'c CDine lastl)' to (lii))'cx workiiv^r— nr sendins^r two si;4nals in (ij)|K)site flii'L'ctions — at the same instant and tlin)UL;li the same coiuluetor. This metliiid, worked out in theor\- by Dr Gintl of \'ienna, as early as 1S53, and rendered practicable by Mr j. H. Stearns with the use of condensers, in 1873, was successful!)' a])ijlied some )ears later to submarine cables of an)- IcuLjth. The honour of this t^^reat achievement is |)rmci|)all\' due to Messrs X'arlev, De Sautw Stearns, Muirhead, Ta\-lor, Ilarwood, and Ailhaud. Client Xmilicni Tflcj;raph Compaiiy : Amny Station. 5«4 SLiiMARiM-; Ti;i,i:(iUAriis. Sr.cTiox 2. — Rel.ws an'I) Snx'iAi, Mi:iiit>i)s for DisfiiAKciNc. Caiu-ks of Modkkatk LFN(ii"n. Discharging Relays. — L']) to a distance of 150 miles tlic ordiiiaiy Morse ai)ijaratus can be employed both 011 land and submarine lines. Beyond this limit the rate of sendini^ has to be .considerabl}- reduced, and even then the signals soon commence to arrive in a mutilated condition, due to the effects of alternatel\- chari^ini;- and tlisehari;in;4- the cable. 'I'iie state of thinujs last described is remedied, in a great measure, by wiiat is known as the double-current Morse s\'steni,* which consists in following up i-ach successive signal by a weaker current impulse in the ojjposite direction, in such a wax- as to facilitate the more complete discharge of the line. The strength and direction of this rexersed current shoidd be so regulated as to bring the conductor to the neutral condition, at the instant when the ensuing signal commences. For cables less than 300 miles in length, the strength of the two currents should be in the |)roportion of 3 to 2. Sometimes the line ii simpl)- put direct to earth for an instant after each signal. The discharging current can be sent into the line automatically by means of the arrangement shewn in l'"ig. 43. s is a Siemens polarised relay who.se resistance is about equal to that of the line combined with that of the receiving instrument at the far end : the armature, the side on which * The ordinary .v/V/^Vt'-currenl Morse system is only capable of employment on (/uih' short cables. SlCNAI.I.INt; AI'l'AKATl S. 5-^5 makes cotiiK-ction with the ihscharijinLC batten-, is furnished witli a sprint; intended to prolmiL;- tlu' duration of eontacl (in tliat sidi-. Tlie distance between the tu'O screw contacts \ and \ ' is adjusted to i;i\e sufficient play to the armature A 1). W'licn the sendinj,^ key is dcjircssed the jiositixe current from the hue battery (h'\ ides between the cable and the relay s, the armature A i! making contact with \'. Directly the si^mal is completed and the key returns to normal position, tlie net^ative current from the dis- char^int;' battery divides in tiie same wa_\- between the c.dj'.e and the relaj- s, the positive char,i;e remainins^r j,, tlie cable is neutralised and the armature returns into contact with the terminal V. Several other arran.i(ements effectin^f the same result in a still simpler manner ha\ c been devised in the last few years. Auxiliary Discharge Coils. — .Supposing; that to the "line" terminal of a Morse sending; key are joinctl up the cable and some coils whose j(jint resistance is about «. [ual to tliat of the line, on depressin;/ ,«j tile ke\' the portion of the current which enters the line is sensibly the same as if there were no resistance coils ; and when the ke\- lifts, the line dischari^es itself almost en- tirely throuL;h the C(m1s — be- fore there is time for the key tcj resume its normal position. To a\()id the weakeniiiLj of the resultant current at the far end ow ini,^ to its dividini; between the receiving instrument and the artificial line, the latter may be con- nected to a spriuLj blade, one end of which is fixed and the other end allowed a certain amount of |jlay between two contacts in close juxtaposition. These contact pieces ( I'^ii;". 44) are situated sliL^htl)' abo\e and behind the le\er of the sendini;' ke}-, and the blade is held down against the lower contact b)' a small spiral spring;. A screw point on the kej- lever is adjustetl .so as to make contact with the blade directly the key beijins to rise, the contact beinjf retained until just before the key returns to its normal |josition. This method, devised by Mons. E. Wlinschendorff, M.I.h'.E.,* in 1881, Fk;. 44. * Engineer to the I'aris French Ciovernment Telegraphs, and author of " Traite de Tclcgraphie Sons- Marine,' a part of which work formed a basis for this voknne. 586 snsMAKINK TKI.KCRAI'IIS. wliL'i) the fust loiii^ subtcTraiicaii line-; in I'laiici- were inaiiL;urate(l, has [(wen <^r()(Ki results on the iincler^froiind cable from Paris tench Telegraph Department. With the automatic releasing trigger apparatus and with currents of same polarity, the discharge current produces, at the sending end, the effect of a current from the opposite end of the line, and prolongs the battery current at the receiving station. If the line is charged with several current impuLses succeeding each other at ver\- short intervals, the return current may acquire sufficient strength to print additional letters. To obviate this defect, a steel cam was fitted on the cam axle in the centre of the available space between the two platinum contacts, and SKiNAI.I.INC Ari'AkATlS. 5'S; H re arrarif^ed so as to rub ac^aiiist and raise a flat spring' at the rc(|uir(.-d instant. This flat sprin}^ butts up a;,^ainst a set screw fitted to a second s|)rinL^ above, insulated from the rest of the apparatus by a plate of i\()r\- or ebonite and in connection with a discharL,n'n[,r battery. The form and p(wition of the cam arc such that contact w illi the dischar{;in<; battery bc{,qns an instant after contact with the line batterj- finishes, beinj;- con- tinued until the line is put in direct communication with earth throu^di the framework of the electro-magnet. Tlie compenstiting current lasts in this w,iy about a quarter as long as the line current, and their relative intensities should be in about the same pro|)ortion. The set screw in the upper spring permits of the necessary adjustment. Sometimes the discharging batterj' is replaced by a simjilc earth connection, in which case the discharge will be less comjjlete unless the line is a verj* short one. On the subterranean line between I'aris and Nancy (3^7 kilometres), this modi- fication of the Hughes ap|)aratus works continuously at a speed of 105 to 110 chariot turns per minute. It is, in fact, capable of transmitting 160 letters per minute. fs N l-ii;. 45. Brown-Allan Relay. — This apparatus (Fig. 45), introduced in 1878,* consists of a very light single cylindrical electro-magnet, suspended by a platinum wire K to a strong bracket II. so as to be perfectly mobile. The position of the electro-magnet may be accurately adjusted by turning the screw V and stretching to a greater or lesser extent the two silken threads /,, /.',. The hollow core A I! of the electro-magnet is placed in the centre of the vacant space between the poles N, s, n', s' of two powerful horse-shoe magnets, one of its ends A being attached to two opposing springs i\ and ;■„. A rod of soft iron a l>, resting on the upper surface of * The above invention— due to Mr iirown — is somewhat similar to an earlier apparatus of Mr .-\ndre\v Coleman. The 1 rown- Allan relay forms the subject of a patent (\o. 1,757 of 1876) taken out in the name of (Jeorgc Allan and James Wallace Hrown. vS8 sliimakim; Ti:i.i,(.kAi'iis. the (.'Icctro-ma^^iict, turns with but little frictiou louiul a \filical axis <• attached to the reel, the small au^^le throu^^h which the rod deflects bciii}^ limited b)' two stop screws r, and v.,. The resistance of the coil is usually 500 ohms, and on the ])assagc of a current throutrh the coil, the core cylinder becomes magnelised, causing' its end A to ai)[)roach the pole s', let us say. The rod d l> follows this movement, but is almost immediately brou^'ht up a^fainst the stop ;',, where it closes a local circuit and leaves the coil to continue the movement alone. As soon as the latter commences to svvin^ back to its normal ])ositioii, the rotl a h is carried back till it butts again.st the stop v.y A general view of tliis suspended coil type of Brown- Allan relay — the form used in submarine telej^raphy — is shewn in l'"i^. 4''). In later patterns of this relay,* the rod ah (l''i^^s. 47 and 48) is mounted on the same a.xis /// « as a second somewhat longer rod c d, a sprin and the Morse receiver R. A small condenser c: is sometimes insertetl between the terminals of this receiver to diminish the s|)arkiii^' between the armature ix b and the stop •', called by the "extra current." To ciiaii^'e to llic SLMidiri;^ position the switch 1 is nio\ed to contact Ki(i. 4S. No. 3, which cuts the relaj- I! out of circuit, substituting for it the current reverser K and the sendinj,^ key D. The former of these is worked by the local battery/., when D is depressed : the armature L being pulled down by the electro-magnet m', breaks the contact between the lever /", ; and the terminal /, at the same time leaving /, free to ])rcss uj) against /. The ''^m'^ [§i m Ku;. 49. negative jkjIc of the line battery r is thus put to earth, whilst the current from the positive pole flows into the cable by way of the armature L and No. 3 contact piece. This rela}- , largely — in fact principally — u.sed by the Eastern Telegraph Company) was the result of a great deal of experience and experiment. It 590 sui'.MAkixi-: Ti:i.i;iikAi'iis. supplied, at tbo time of its introduction, a long-felt want, more cs])ecially in the case of cables exccedini,^ 250 miles in lenL;th where . 'orse workint^ was desirable or unavoidable. l're\iousl}-, numerous cables had been worked on the Morse principle at the comparatively low rate of nine or ten words a minute. This was much to the disadvantaL;c of the companies which owned them, not only throUL^h the threat and serious flela\s which fre(]uentl}- occurred to the traffic, but also on account of the man}- eriors which must necessarily occur when an instrument not reall\- adapted to ihe work re(|uircd is pressed to the maximum speed at which it will res|)(ind. The Allan and Hrow n relay, owinn to its sensitiveness, jjcculiar con- struction, and particular ada|)tation to cable working-, ol)viates ,-ll these evils. It increases the speed o\cr the Morse sj'stem (with ordinary relay) previousl}- in use by 120 per cent., whilst involving no increase of trouble. Its principal point is, of cc^urse, this great increase of speed it secures. But there are also other advantages, such as the marked uniformit)- of the signals, the little attention rccpiired for regulation, and the low battery ])ower which it will work with on account of its extreme sensitiveness. This relay, when once pro])erly adjusted, will work for months without recjuiring any further attention. It gives good results on lines of medium length. The " Eastern " C'om|)any's I'orthcurno-X'igo section, 620 miles, could not be worked practicall)- on the Morse sjstem with an}- ordinary relay, but a speed of twent}'-six words jier minute is obtainable with the " Allan and Brow n."* The Direct Spanish Compau}-, in ado])ting the Brow n-.Allan relay on their Mor.se-worked cables, increased their working speetl from twelve to twenty-sexen words per minute, h'ormcrl}- tlu- mirror had had to be ke|)t in readiness as a reserve and cmplo}'ed during aiu- particularl}- bus}- time, the ordinary Morse (i.e., the Morse with the ordinar}- Siemens or other rela}-) being totally inadequate under such circumstances. The Brown-Allan rela}- is also in use with the double-current Morse .s}-stem emi)lo}-ed b}- the Indian Government Telegraphs. Again, the Bushire-Kurrachee section of the Indo-luuopean Govern- ment Telegraphs Persian Gulf cable, 1,050 miles in length, with metallic connection at the intermediate station of Jask, used to give sixt}-five letters per minute, whilst almost double this s])eed was obtained on the two nearl}- ei]ual lengths of divided section, Jask-Hushire and jask-Kurrachee. On working through with a Brown-.Allan relay set U]) at Jask, the sending speed from Bushire to Kurrachee rose, during trials, to at least one hundred letters per minute. * .Now, however, tlic siphon lecortler is in use for working tliis ciil)lt si(;\.\i.i,i\(i AiTAkATrs. 591 However, tninsmission s])eecl trials direct from Malta to London, with Brown-Allan relaj-s at Hona and Marseilles maintaining the ordinar\- re|)cating installations at Paris and Beach)' Hea(l\ onl\' ga\e from fort\'- five to fift)- letters per minute — much less than that obtained over the aerial line alone and through the cable alone, using in the latter case a mirror instrument or siphon recorder. The secret of the success of the Brown-Allan relaj- lies in the fact that it contains what is technically known as a " mo\Mng zero." All other relaj'.s prcviousK- in use — such as the ])olarised relays of Siemens and Stroh — had "fixed" or "dead" zeros. No instrument can be worked with any reasf)nable s|)eed, or success, through cables over 300 miles with the ordinary core for short lengths (under, say, 700 X.M. , which doe.s not con- lain this qualit}" of a "mo\'ing zeri)." The mirror, recortier, ;ind Hrown-Allan relay all include this element —hence their enhanced value and success. On cables of 300 or 400 miles the jockey armature of the Brown-Allan relay can be attached with advantage to any other instrument, such as a Siemens, or other, rela\-, and this alteration will increase the speed certain!)' to the extent of lOO per cent. The Morse s\'stem even when sup])lemented by this rela)' would be ciuite unsuited, however, for ocean telegraphy — or, indeed, for submarine cables over 600 X.M. or so of ordinarx' core. . ■ » ,-,.' ."^.■J^4afti;n.;iv\^'lL'^'„^M^ • .'^'■ 0^^'iW^-^ "(irL'at N'nrtliuin " I'luupany's Ti.'lf^;r.i|ih Slii|i "II. C". (Ir.sliii": ( )(V Coast of Korea. 59- srUMAKINi: Tl.I.l.C.RAI'IlS. SliCTlON 3.— Tin: MiKRoK SVSTKM. Cables cannot be satisfactorily worked on the Morse system — under an\' circunistances, with any e.\is^inlJ relay or cable discharger — if the leni^th in circuit be innch over 700 miles — of the ordinary core for such a Icni^th. Thus when i'rofessor Thomson now Li)rd Kehinj introduced in 1S58 the mirror instrument — i^ahanometer as then called — it was a considerable advance in ocean tele""rai)h\-.* The Mirror "Speaker." — The mirror receiving;' instrument [V'v^. 50) differs from what is now known as Thomson's reflectini^ t^ahanometer in havint;- one coil only and a system of ma^jnetised needles attach.ed (usuall)' by means of light shellac; to the back of the mirror. 'l"he latter, suspended by a \er\' short cocoon fibre, is enclosed in a brass tube which is inserted through the centre of the coil as in dead-beat galvanometers. .\ stout semi-c\iindrical magnet completely covers the upper half of the coil, and can be revolved to a limited extent round a vertical axis by a screw placed at the top. The needle can be brought to any convenient normal position by slightly tunu'ng the controlling magnet in the required direction. The entire apjxiratus is sup|)orted bj' a stand on which are fixed four terminals. The.se terminals connect with two ' r more .separate circuits of 1,000 and :2,ooo ohms, or any other required resistance, severally wound on the reel. By joining up to the terminals in different wu)s the resistance can be obtained nearest to that which gives the maximum effect theorcticall}-. The rays of light from the lamp, ;ifter ))assing through a long narrow „ „jfaiiiiiimMiiiiiiiMiiS jMi|B pliiii| | |iiiiiiiyiiiM Kic. 50. — Mirnir Signalling Insuumciil. * A jjreat point of advantage in both the mirror and siphon recorder instruments (as compared with the Morse instruments) is the fact of their action bein^^ dependent on (/iii//i;-t's of cuirent-strengtli only as measured by distanie from the zero line - /.i'., by a potential luivc ; and the fact that, therefore, it is not necessary to wait for the entire clearinif of the line before a fresh signal can be sent out. SIG%ALLING AITAKATLS. 593 slit in n scicoii, arc focusscd b\' a lens, and are reflected back from the mirror on to a strip of ])a|)er su])])orted on a stand or scale.* The luminf)iis image or "spot" may be finall)- adjusted b}- the controllinj^r mai^nct so tha*^ as lon^i^ as the instrument is at rest, the s|)ot will remain in the centre of the scale. it has become a ver}' L;eneral ])ractice — in the first instance with Messrs Siemens Brothers — to fill the brass tube contairn'nt; the mirror with (_|uite dilute i^lj'cerine.-'- N'ibratory oscillations are considerably reduced by this means without in an\- way spoilini; the sit^nals. This plan is especially a])plicable to a cable subject to stronjj earth currents, or in the case of a fault}- line. Asj^ain, within the last few years Mr Walter Judd, of the l-"astern ICxtension Telegraph C'ompanx-, has introduced a still furdier improxement. .Accordini^ to Mr Judd's device, a rod of soft iron is inserted into the mirror tube, furnished with a shoulder piece at one end to prevent it actually touching the mirror by entering too far along the tube. The core becomes magneti.sed by ever)- current passing through the coils, thus |jroducing greater am])litude in the signals. Again, owing to the fact that it does not gi\e up or reverse its magnetism as rapidl)- as the signalling currents pass through the coils, the signals are steadied and rounded off — a considerable acKantage on short lines, as well as in the instance of a defective cable, or one subject to strong earth currents. By adjusting the length of core w ithin the tube the signals can be brought to any reiiuired size. This last device has been rendered still more effectual b}^ winding the .soft iron core with fine silk-co\ered wire, connected up in series with the mirror coils. The above transformation of the core into an electro-magnet is due to Mr John R_\-mer-Jones, of Silvertown. This gentleman has latel\- de\eloped an im|)roved form of instrument es])ecially designed for use on board ship. Ihe latter was fully described b\- him at the time in the columns of the /Ucctiiin/ Ri'vic'Li' (vol. xl., p. 39 . Here, too, Mr R\-mer-Jones shews '" It is very usual, however, to adopt wliat is loinmonly known as Jacob's transparent scale, the principle of which is described elsewhere. By this means it is no lon,i;ci necessary to darken the room. The method is, in fact, even more applicable to constant signallinjr pini)oscs than to periodic teslini,' purpose .. Another plan is to reflect the spot on to the receiver's writing pad. In ordinary work, however, the message h.is to be dictated, as rccei\ ed, to another clerk. To obviate this, the author has suggested that the receiver, though unable to write the message properly, whilst reading the mo\enients of the spot at a high speed, would soon be able to key the letters of a typewriter. ■^ The details of this plan have recently been considerably simplifieil and impro\e(l by Mr Frank Jacob on behalf of Messrs Siemens Brothers and Co. For further particulars sec the f-'/cctricd/ A'cTi'm' i)i 2^\.\\ December 1S96. 594 sriiMAKiM: Ti:i.i:(ikAi'iis. very clearly the requirements for sensibility, dc:ul-beatness, etc.,* under the varying conditions in which hi-, iniproved ai)ijaratus can be used by ditTerent ac'justments for each case.+ The uni\ersal Nuspended coiljiralvanometer of" Mr 11. W. Sullix ,in :J can also be turned to L-ood account for siL;iiallinLj — es|jeciall_\- where dead- beatness forms one of the reciuirements, as in ship to shore communication on a cable with a fault in it.^ I he .semi-cylindrical controlliiii;- inaL^net of the ordinar)' mirror instru- ment is sometimes replaced b\- two bar ma;4nets (Fii^. 51) which pass in throutjh the coils ri^ht U|) to the brass tube containini.;- the mirror presenting;" i)oles ofo])posite names. 'I'wd ^^ toothed wheels, a and /', ent^aginL,^ in racks on the magnets enable the instrument to be regulated with the greatest nicetw A common i)ractice with the Silxertown Company, in connection with the cables in which they ha\e been concerned, is to employ and provide what is know 11 as a water resistance. This instrument Fig. 52; is inserted in the receiving circuit between the cable and the receixing instrmnent, or between the latter and the earth, thereb\- introducing a certain resistance in such a way as to diminish the size of the signals to the required degree. The \alue of this resistance ma\- be \aricd b\' raisin;/ or loweriu"; the 51- * In Mr Ryincr Jones's device, the front of tlie tube is additionally closed by a trans- parent cap. Thus the movement of the mirror is still fmther damped by the confined air. The beneficial eftect of the above is naturally much more marked in the instance of sharp signals when there is little or no capacity in the line circuit to jiroducc retardation. It is, therefore, peculiarly ajjplicable for working on quite a short length of cable, or for practice purposes through an "artificial." t The two extreme conditions under which the instrument can be used enables the ship after cutting a cable, in the course of repair work, to speak in either direction -i.e., through a long section or on practically short circuit, if close in shore. Thus, the necessity for a Morse instrument during cable operations is entirely ob\iated here. \ For a full description of this instrument reference is mailc to the Eli'i/i iciiiii ;ind the Eliifi iLiil Rei'uic oi 22\v\ Mardi itSi)5. .<■ Again, it is believed that Mr Thomas Clark (chief electrician to the Telegraph Construction Company) and Mr T. E. Weatherall have devised another marine galvano- meter recently, vhich, additionally, meets these ends as in the above case. i This appa Mtus is a cheap and handy substitute for a set of adjustable resistance coil«, though less reliable. In the course of some e\periments made by the author, it was found that — speaking roughly— the resistance of hot fresh-water was as much greater than cold frpjn-water as the latter was in comparison with salt-water of the same temperature. This is, of course, no less natural- on the score of the extinction of animal life under a gi\en rise of temperature— than that distilled water has a still higher specific electrical resistance. SICNAI.LIXC, AI'TAKATL'S. 595 ra->si'BcLy insulated loo]) coiuluctcr L, thus intcrposins^ a i^M-catrr or less area of water between the contact pieces A, It, and the resi)ecti\e terminals C, l> l)elow. With fresh-water the whole len^L;th of each tube represents man)' tliousand ohms resistance. Unfortunately the contact pieces ijct dirty and involve too hi|^h a minimum resist.ance, as well as a vcr)' variable cjuantit}-. More- over, the water is liable to leak. Both of these objections have, however, been to a i^reat extent, if not entirel}', o\ercome in recent improvetl forms. Where very little ca|)acity or resistance is present the retardation is .so small that the sitjnals become ver)- shaky. They may be steadied to a great e.xtent by the interposition of artificial retarda- l tion resistance and capacity) at cither or both ends of the circuit. .\s a rule, howexer, where the ordinar\' forni if mirror instrument is in use, the lowest length of cable, with the usual core, which can be effectively worked on this system is about lOO miles ; and this only w ith a very stiff suspension, besides a good deal of artificial resistance and capacity. Hitherto, therefore, in the ca.sc of lengths below this, the Morse system has been adopted. .As has already been shewn, the latter introduces man}- objections in the way of delays, misadventures, etc., es])ecially if the adjustment of the relay is not ])roperl\- imderstood at either end. It is not improbable, however, that when modi- fied in the complete manner suggested by .Mr Rymer-Jones, the "mirror" might be made to work satisfactoril\- on ([uite short lengths. If so, it would be |)eculiarl}- well ada|)ted for taking th.e place of the Morse entirely during cable operations fr)r signalling pur))oscs between ship and shore. I'll-,. 52.— Water Ki;sista.icc Apjiaratus. Suspended Coil Mirror. — .\ mirror instrument based on the sus- |)ended coil principle has been found a capital substitute for the ordinary, sus|)ended magnet, mirror on occasions. In this, the sus|jcnded coil is free to mcne in the field — /.(•., between the poles — of a powerful permanent magnet. Mr K. Ra\-mond-Barker experimented with such an instrument on the occasion of a fault on the iirazilian .Submarine Company's system, his idea being to be able to work the cable notwithstanding the fault b\- using such an instrument as would be sympathetic to tlrmly transmitted signals, but which — unlike thcordinar}- mirror instrument with exceedingly light suspension — would be beyond the influence of sudden vibrations 59C SUlSMAKINi; TI'.l.KCKArilS. arisini^ from tlic fault. Tlic suspension consisted of a lont^-range mirror on a 500-ohin coil, ke|)t in position by fibres and weights, as in the siphon recorder hereafter described. This instrument has an action which greatly tends to smooth off jerky vibrations ; whilst, at the same time, readily res|)onding to battery im- l)ulses. It is a capital "all-round" form of mirror instrument, as one adjustment suffices for signals from cables of \er\- uneciual lengths. Notwithstanding the great comparati\e weight of coil and mirror, and the general stiffiiess and rigidit}- imparted to the signals b\- the lower bifilar suspension and weights, the instrument as a signalling apparatus is even more scnsiti\e than the ordinar)' suspended magnet mirror — under certain conditions doubly as .sensitive, in fact. It should not be su|)|)osed, howexer, that this latter is aii)- special point, except under particular circumstances. The ordinary mirror instrument is cjuite sufficiently .sensitive for all ordinary cable signalling, besides ! eing an ideall)- simple and portable apparatus. > c, Cable 'H HI, III l-'ic. 53. — .Minor System ('omicclicui. St.\tio\ I\st.\ll.\tion. \\ hen the line is worked simplex, each station sending ;ind recei\'ing alternately, the general scheme of installation is represented by I-'ig. 33. By depressing one knob or the other of the t\vo-le\er ke\- M, the operator .sends a pf)sitive t)t negative charge into the neighbouring condenser c, producing a deflection to one side or the other on the mirror receiver at the other end of the line, lie works the switch .s each time he wishes to change from .sending to receiving, or 7'nr 7'rr.ui. In the figure, stati(m i is in the sending position, and station 2 ready to reccixe. SICNAI.l.INc; AI'l'AkATUS. 597 Transmitting Keys. — Durini;' the period of mirror signal lini^ on lontj caljles prc\ious to the introduction of the siphon recorder, various forms of transmitting kcj-s have from time to time been introduced, all of them beini;- on the double tappet sjstcm, as in the case of needle instrument working;'. Latterly these have been very much improved on in details of construction, various devices having been incorporated therein for dis- charging the cable, by instantaneously and automatically putting it to earth after the transmission of each signal. 'I'hese impro\emcnts were I'li;. 54. — .Mirror Key and Switch (scale='j). mainl\- introduced since the adoption of the siphon recorder in place of the mirror instrument on most of the long lines, the same form of key being of course applicable to either case. Ihe switch for changing from sending to receiving and vice vcrsn is \er\' usuall)- no\\ada)'s incor|)oratcd with the key. Fig. 54 represents a good substantial and reliable species of combined key and switch, as designed by Mr VV. A. Price for the Silvertown Company.* Fig. 55 shews the simplest form of connection * Even by cNperienced clerks, attendance to hand switches is liable to be forgotten. .Some years ayo, Mr R. K. (iray, M.lnst.C.E., designed an ingenious double-lever 2 S 598 sr liM AKi \ i; ti;li;( ; rati is. at a station in connection with a short cable {ivitliont condensers) — having a small amount of traffic — worked by the mirror system. The connections are sometimes arranged in such a way that the current is also conveyed tlirough the instrument at the sending end for the purpose of assurance that there is a com|)lete circuit. This is a good plan in the case of temporary operations, such as during, and just after, the original laying Lamp and Scale o anT Mirror Inst. Water Resistance. Vu:. 55. — Sim|ile Ccnir.cclions al a " .Mirror .Statimi." of the cable, or in connection with repairing operations, A shunt to the mirror at the sending station requires to be then thrown into circuit. Hy this means, moreover, some estimate mav be arrived at as to the character signallin^r key without any liand switch. The latter was replaced by an automatic switch arranj,''ement underneath the levers of the key, the movement of which intliienced them. Unfortunately it was found that the object aimed at here was not always realised in practice. SICNAI.LINC. Ari'AKATUS. 599 of the sit^Mials at the fiiitlicr end, the oiitgoinj,^ sii^mals actini; as a rouLjh guide. To obtain concise sif,mals much depends on well-timed manipulation at the sending end, and duration of contacts suited to the length of the line and the electrical qualities of the core. Too short current impulses may be insufficient to |)roperly charge the cable, and the signals will suffer at the distant end in con.sequence ; too long contacts, on the other hand, may develop counter signals difficult to distinguish from the real ones. To understand this last effect, suppose one of the key levers to be held down till both condensers and the cable are completelj- charged ; the spot will then return to, and remain at, zero. The moment the lever is let go the discharge from c",, c, (see Fig. 53; and the cable will cause an instan- taneous reversal current, which will produce a .second deflection at the receiving end opposite in direction to the first. Kach depression of one key lever thus giving two ojjposite signals, correct reading would be impossible. On the other hand, if the duration of contact is very short, the galvanometer needle G._„ after deflecting, will immediately return to y.evo without passing this [joint, the discharge current merely accelerating the return movement. If however, the key lever is kept down a little too long, the needle having already started returning to zero, the discharge, when it occurs, will cause the needle to continue on its travel and gi\e more or less of a deflection on the other side of zero. Earth Connection. — In the case of submarine cables under ordinary circumstances, the sheathing wires of the cable itself is the proper earth connection to adopt. Several wires should be connected together and made use of for this purpose in the manner described elsewhere. When, however, \ery sensitive instruments, like mirror receivers, are installed in telegraph offices where other conductors are brought in (especially if they are oxerhead wires, such as require powerful batteries), special jjrecautions must be taken with regard to the earth connections. What, in fact, hap])ens is, that a portion of the charge in the land lines — small it is true — instead of dissipating in the earth, leaves its own earth connections only to re-enter bj- those of the submarine cable, where it interferes with the mirrors. A ca.se of this kind occurred, in 1875, at both ends of the Marseilles- Algiers 1871 cable. At the Marseilles end the mischief was casil)- remedied by soldering the sheathing wires of the underground cable (which was about 3^, miles long, and used as an earth for the mirror instruments only) to the sheathing of the submarine cable in the hut. At Algiers, where the ground is drier, it was onl)- possible to prevent diffusion of the electricity from the different earth connections 600 sriiMAKINi; TKI.IKIKAI'HS. (special plates, water-pipes, etc.), by usiiiij as an earth wire for the sub- marine line, the interior conductor of an armoured cable which went direct to the sea, at about i .1 miles from the station, and was joined uj) to a lar<;e i)late of cojjper immersed in the water,* after the manner suggested by Cromwell Varley. Mutual induction between two electric circuits (cables, or otherwise), closely located and running in a more or less parallel line, is another source of trouble which recjuires to be considered and guarded against. Quite recently, in the course of a paper + read before the Institution of Electrical ICngineers, Mr A. I*. Trotter* shewed — by a practical example at Cape Town — how seriously an electrical tramwaj- line could influence the working of a submarine cable whose shore end was sufliciently near. On this occasion the present writer suggested that with care it might always be possible to balance these inductive effects in the compensating circuit of a duplex system, though its accurate maintenance would be a matter of some ilifficult)-. Neighbouring electric light mains are similarly liable to be a source of annoyance — especially if conveying high potential currents: and it is for this reason that their whereabouts are restricted by the I'ost Office land- line system, particularly where the telephone is in question. System of Checking Tran.s.mlssion. When it is desired to keep a check, at the sending end, on the messages transmitted, double-lexer keys are sometimes used of a special form designed by Mr H. A. C. Saunders. They consist of two Morse keys in connection with each other through their pivots, and furnished with steel spring blades at the rear end, these springs being insulated from the levers to which they are attached by thin sheets of ebonite and working between two stop contacts. The connections are joined up as in Fig. 56, and the working is as follows : — On, say, depressing the knob X'', the positive current from the line battery i' charges the condenser c, and a current in the same * It was ])ossibly with a view to obviating the above objections that as long ago as 1856 Mr Wildniaii Whitehoiise and Mr Samuel Statham appear to have taken out a joint patent (specification No. 1,745 of that year) for using a wire as a "return" instead of the earth, either in a single circuit or for several circuits combined. t Jour. /.£.£., vol. xxvi., p. 501. I Lately appointed Electrical Adviser to the Cape Government. , SICNALI.INC. AI'I'AKATIS. 6oi direction, cominj; from the first half of the battery /, passes throui^h the Siemens form of Morse receiver M with duplicate jjolarised armature (^'rt- 57)- Deprcssin^^ the knob k- would send a ncgati\e char^^e into the condenser C, and a similar ciuTent through the receiver M. In the first instance, one of the two armatures of the receiver would be attracted, and a blue mark printed on the paper, the movement of the second armature producing the same effect in the second case. In this way two parallel rows of dots or short marks arc printed on the strijj of paper, the marks in one row corresponding to dots, and those in the second row to lie. 56. dashes, of the Morse alphabet. These symbols read quite as easily as the characters of the Morse code — /> li f The commutator .s has three different positions, the intermediate con- tact being connected directly to earth, so as to enable the conden.sers to discharge themsehes rapidl)' when changing from the sending to the receiving position. In the cases of the two Atlantic cables between Penzance and Canso, laid in 1 881 and 1882, belonging to the American Telegraph and Cable Company, each condenser C has a capacity of 130 microfarads. They consist of 13 boxes of 10 microfarads each, the several boxes being sub- divided into 5 sections of 2 microfarads each which can be joined up 602 sniMAkiM'. Ti;i,i;(.UAi'iis. tof^cther in diffL-rciit ways according; to ro(|iiirciiicnts. Thi.' line battery r consists of lo Siemens and Ilalske cells, of considerable internal resistance, but giving a very constant electro-motive force.* Record of Mirror Signals as Received. — Attempts have also been made to utilise the radionieler of I'rofessor now Sir William) Crotjkes, F.R.S., for recording; si^Mials jjroduced by the mirror recci\er. An instrument based on this principle was shewn in the l-Vench Com- mercial Section at the International Klectrical Exhibition at \'ienna, in 1SS3. The moving- parts of the radiometer ; 1m^'. 5, />', which pass out throuLjh the glass at the lower end and connect to the coils of two Morse electro-magnets A, A' ; the other ends of these coils are joined up to the negative pole of a battery "* "Die Einrichtung iler Kiistenstationen langen Unterseekabcl,'' l)r von Tobler, Flektro-technische Zeitschri/t, 1 884, p. 76. SICNAI.I.INO Ari'AkAl IS. 603 wliiisL- positive piilc CDinimiiiicilcs uitli tiic metallic pivot < on which the vanes of the radiometer oscillate. I'he a|)paratus is placed in front of a mirror receiver in such a way that the spot, when at rest, appi'ars in the centre of the space separatiiiL; the two vanes. When the spot dellects to the riijht, for instance, the vane u' bcinj; repelled, makes contact with the wire /'', and closes the circuit of the elcctro-maj^met .\', whose armatin-e is accordini^ly attracted. If the styles attached to the arm.iture are hroii^^ht close enoiii^h toLj'ether to print the marks on the same -.trip of paper, the signals can be read without difficult)' !))• means of the .StiMuheil alphabet. This apparatus, howiner, has never been turned to acctMuit in the practical working of our submarine cable .systems. 'l'..S. " SilvfiUiwn " l.aiiiliiif; llio Cal \c at l'\rn.ini(> do Noninlui, l.Scjj 6o4 slii.makim: ti;i.i:(;kai'1Is. Section 4. — Sh'Iion Ri-cokdi-.k Work. The sijjhon* recorder, conimoiily known by the more sim))Ic title "recorder," was first iinented by Sir William Thomson in the _\-ear 1S67, but since then it has received numerous improvements. As already stated in I'art I., the si])hon rec()rder has L;raduall\- sup- planted the inirror instrument on all the existint; lont^- cables where the mirror had been in force, excejjting in those of the " West India and Panama" Compan\-, and in some of the sections of the "Western and Hra/ilian " Compan\-. l'racticall\- speakini;, eciually sensitive to weak currents (thouL;h requiring more skill in technical knowledge and atten- tion}, it has the enormous advantage of \-ielding a record of the signals as receixed — and also as sent, if tlesired. Again, being much less trying to the sight, it is a inore satisfactory instrument fur working. Tliough at a \ery slight disadvantage as regards speed of working (under given common conditionsj, the feature of a record being obtained was in itself a sufficient point of advantage to bring about the gradual replacement of the mirror instrument b}- the siphon recorder as soon as the latter had been invented. Inasmuch as the Post Office and other Government inland telegraph systems have gi\"en up the use of records or recording instruments for their .systems, the great advantage of a record for cable working may not appear very obvious. The case of submarine telegraph)- effected hy competing companies is, howe\er, entirely different to that of land telegraphs managetl by the State. Thus : , \.) In submarine telegra])hy there is an ad\antage in any " slij) " method, in that errors are less liable to t)ccur, as the clerk has thereby a chance of referring back if in doubt about an\- word, or words. (2.) Errors are a more serious matter for the companies' cables than for the State-controlled lines — indeed, the (jo\ernment do not — in a complete sense — undertake the oiins of them. It is, therefore, much more important that errors should be kept at a minimum in submarine cable system, and the message sent out absolute!)- ccjrrect to start with. (3.) It is more essential to be able to trace errors, inasmuch as the competing routes undertake to obtain repetitions free of charge, provided that the error is found to rest with them. The siphon recorder j^ossesscs a still further acKantage oxer the mirror system in that — with the usual manual transmission, at any rate — it rctiuires only one ordinar)- clerk at the receiving end, instead of a first-rate mirror clerk and a writer. * Oblivious of its (Ircek derivation, ibis uord is often erroneously spelt syplwn- espccially on grocers' and ciieinists' lal)els to certain vessels containing mineral water. si(;naijjn(; aitaratls. 605 Oil the oilier liaiid. the initial cost of the sip'ion recorder is, of course, ver)' much t^reatcr than that of the mirror instrument — the pro])ortion beint^ about 10 to i, in fact.* Still, since the nnalt\- has been taken off the si])hon recorder costs verj" much less than it used to, being about i^.75 (with vibrator) — or about ^45, with direct writer, for short cables — instead of some /"600 including; royalt\' and sole manufacturer's charijes. The Instrument. — In its latest form the recorder consists of an exceedinyl}- lit.jht coil of wire, delicately suspended between the two poles of a powerful electro-magnet, and ca])able of turning on a \ertical axis. The coil is so arranged that, in its norma! ])osition, the plane of the coils ikdanw .--^ % •/"' V /' : / Under:>l3nd v^ v/' ..^7v^t/u-.-^\-^r-i, A ,/ i .' ■■ / r \r^J A/o-u- v.^,vA/ ■■->c vV ^-^^^ I-'ir.. 59. — Sipliim ReconliT Siijnals. of wire is parallel to the north and south line of the magnet. On a current circulating in the coil, the plane of the wires tends to take U|) a ])osition at right angles to the north and south line, the coil turning one way or the other, according to the direction of the current. t The motions of the coil are transmitted b\- silken threads to an extremel}' thin glass siphon, mobile on a horizontal axis ; one end of this * The iniiior iiistruineiit is sold at about /j, and the double-cuirent Morse at some /18. t There are at least seven text-books which describe tlie siphon recorder, but which, when treating of the suspended coil, remain content with the statement that a current through it causes it to be "impelled across tlie maj,'netic field in one direction or the other, according to the polarity and strenytli of the current passing; tiirou_t,'h it," or words to tliat effect — as if this movement were some phenomenon too complicated for brief explanation. Once, however, it is realised that a current-traversed coil is practically a magnet, tlie rationale of its deflections becomes self-evident. 6o6 sir.MAKiNi; Ti:i,i;c.KArns. siphon dips into a reservoir of ink, and the other end appnjachcs to within a very small distance of a strijj of paper driven through the instrument at a uniform rate. The ink beinj^ in permanent communication with a small electro-static machine, and the paper with earth, the ink is attracted to the |)aper, and issues from the ca])illar)- tube of the siphon with a rajjid succession of tiny sjun'ts. A continuous dotted line is thus inscribed on the stri|j of jxiper, which line is straii;ht when the coil is at rest in its normal position, and undulatini;' when the coil oscillates from one side to the other under the influence of jjositivc and negative currents passing through it (l""ig. 59). The deviations above and below an imaginary l-li;. 60. — Sii-.pcMck'(l C'liil ;»iul Si]ilioii .utachcd tu I'lamc. axial line corresponding respectiveh' to the dots and dashes of the Morse code — i.e., the signals, which exactly represent the arrival curves of the currents — are read \er)' easily when the summits are well tlefined. We see by the figure, which is a facsimile of signals received on the cable from Pernambuco to St Vincent (1,844 X.M.), that when several current throws of same name succeed each other, they arrive so rapidly that the coil has not time to return, in the intervals, to its jxisition of stable equilibrium, so that, as we have already shewn, the signals are produced by the first portions only of the electric undulations sent through the cable. Let us now proceed to examine in detail the various essential parts of the ajjparatus. SIGNALLING Al'l'AKATUS. 607 Coil and Electro- Magnet. — The coil s ('Fit;. 60) is formed of several hundred turns of silk-covered copper wire of 0.003 '"ch diameter, and is wound to a resistance of about 500 ohms. The successive con- volutions of the wire, wound on riijht-handed, are ^lued one to each other, sufficient rigidity being thus obtained as to enable a frame to be disi^ensed with. To render the instrument axailable for dui)le.\ working on the differential principle a second wire is often joined to the first, the ends of the two circuits being soldered to small spirals whose free ends are connected to four terminals (i''ig. 61) insulated from the framework of the instrument by a sheet of ebonite X. The electrical resistance of each circuit is about :350 ohms. When working simi^lcv, or bv Ih-iiige 01. fjuplex, two of the terminals are connected togetlier with a wire, so that the current will |)ass through the two circuits successively and in the same directidu. The coil is susjjended by a fine silken thread whose length can be regulated by means of the screw-nut a. Two threads, /" and /^ secured to the lower corners of the coil (see l''ig. 60), ])ass under a bracket ,;, resting against the roller c, and are kept stretched by two weights p and p^ weighing 25 grammes each, and sliding in an inclined plane K. The bracket .:: is movable to a certain e.xtcnt up or down the ujiright frame to which it can be clamped by a screw-nut // (Fig. 61). This method of suspension brings the coil back to a given aziinuth, after the i)assage of a 6oS SUI'.MAKIM; ll-Ll-CKAl'llS. / Ki( current; b\' raisiiiL;- the bnickct .:, tlic oscillation period of the coil is diminished, and vice versn. In more recent patterns, the \\eit4hts p and />, ("see h"ig. 60) ha\e been done awa)- with, the coil bein_l,^ in some cases, also attached to its frame from the bottom, besides being sLis|jended from the top. The l^'rench Government Telegraph Department several _\ears ago ap])licd a modified form of siphon recorder to their Marseilles-Algiers cable, and in this the coil was maintained in ])osition as follows. The two threads fastened to the lower co'Miers of the coil, HWIIMKIZ instead of being engaged in two grooves on a horizontal c\-linder, adjustable b\' hand (I'ig. 62 1, are pulled apart in a direction perpendicular tQ each other between tlie magnets. :\ rectangular block of soft iron placed between the two poles forms an armature common to the two poles, and by induction tends to increase the intensity of the magnetic field. Round the rectangular block is suspended the coil s, which is thus placed in a magnetic field of great intensit}'. Hy means of the screws V and v', the two coils M surrounding the electro-magnet can be moved nearer to, or further from, the suspended coil s. The batter\- which excites the electro-magnets is di\ idcd into two half-batteries which can be connected up in the circuit separatel)- or combined by means of the commutator II fFig. 66;. A short block of soft iron C', invariabl\- fixed to one of the uprights of the framework, is placed as a core in the centre of the suspended coil s, so as to further increase the intensit\- of the magnetic field. A sort of door W (see I'ig. 64' gives reach' access to the ebonite |)late N in case of need, and enables all the delicate parts of the mechanism to be &CZ)- [Pi.ATi: XXVI. \TofaCi- p. 608. sk;\ali.i\(; ai'maratts. 609 inspected and re|jaired when iiecessarj'. Fig. 67 shews another pattern of a long cable siphon recorder in which the electro-inagnet has been sub- stituted b)- a strong compound permanent magnet. Siphon Record of Signals. — The siphon, shewn natural size in l-'ig. 6.S, is a glass tube of ver)- small diameter, bent twice at right angles near one of its ends, and to an angle of 130 at about I inch from the opposite end. This tube being ver)- fragile, it is well to know how to replace it without ha\- ing recourse to the makers. To do this, select a glass tube of about i inch in dia- meter, with sides about ,'., inch thick- The central ])ortion must now be warmed for a length of about i inch in the flame of a gas-jet or spirit-lainj), tnrning the tube round and Vu.. 66. round during the whole opera- tion. When the glass is snfTi- ciently .softened, it can be drawn out to the rc(]uired diameter, and when cold it is cut into lengths of about 4 inches. To make a siphon from one of these pieces, hold it in one hand, applying the flame of a lucifer match with the other hand to the point where the bend is required. The free end will then droop by its own weight till the necessary curva- ture is obtained. The longer leg can be cut to the proper length with scissors,and the end rubbed on an emery stone so as to get a fine smooth c\u\ which can be brought into close proximity to the paper without risk of tearing. The siphon i thus formed is fastened with a little white wax to the cradle o (Figs. 60 and 69J of aluminium, which is itself .secured to a Fk;. 67. jKiliflmiiliiH .1. •> -Thomson Siphon Ki'i'onlcr, with I'ciiiiancnt Magnet. 6io sriiMAKIM'; TELKCkAI'llS. Flc. 68. --('ilass Siplion nf 'rhnnison RccorclL-i-. platimim wire /. Tin's wire is stretched between two s])rin^^s j^^^ and ,1;.,, and can be Ljiveii a slitjht torsion by turnini; the niill-hcadcd clips I', and v.y The upper end of the siphon dips into the ink-well K, which is insulated from the framework of the apparatus by a rod of ebonite, and also in metallic communication with the disc o ( h"ii;s. 64 and 65). The ink to be used |jreferably is a blue aniline li(|uid, obtained by dissolviuL^ in a half ^dass of water as much of the crystals as can be held on the point of a penknife blade. This solution— of a beautiful dark blue colour, and |)erfectly tluid — does not thicken or form de|K)sits, and can be produced in \ery small (|uantitics. The motions of the coil .S arc con- veyed to the siphon / by two silken threads /> and c (Fig. Go), one of which connects an upper corner of the coil and the centre of the lever y, and the other joins the u|)per end of this same lever to a point n on the aluminium sadtUe of the siphon i) (Fig. 69). The oscillations of the coil are am|)lified in the ratio of the relative lengths of the lever arms of /, which is ]jivoted at ;//, and is called the multi- '^^' plier. In rear of the suspended coil — with regard to the ])oint to which the thread /; fastens — is attached (Fig. 6oj another silk thread .r stretched by a spring (/, this spring being carried in a slide which can be mo\ed to and fro by means of the screw r. The tension of the spring (/ is adjusted to the degree of torsion on the platinum wire /',• and the screw t\ being turned in the required direction, brings the point of the siphon to its normal position opposite the centre of the strip when no current is circulating in the coil. The play of the siphon under the combined influence of the two opposing tensions and the deflecting tendency of the coil will now be easily con- ceivable. The frame <; which serves to stretch the platinum wire / is capable of a slight vertical displacement up or down. It can be clamped by means of the set .screw r .so as to bring the point of the siphon opjiosite the required point on the strip of ]3aper. When the instrument is to be idle for some i',Ki/ — . c ^ Flc. 69. — .'^iphon ami Cradle. SKiNAI.I.INC AI'I'AKATIS. 6ii Ikhii's, it is well to witiuliaw the upper end of the siphon tVom the ink-well, to avoid any chanee of stoppajjc in the tube. To do this, loosen the clamping screw /', and carefully raise the frame c; the sU)t in which the clamp travels during this operation is so shaped that the tension of the thread (• is not appreciably increased. Should the inl< have accidentally dried in the interior of the si])hon, the tube will have to be cleaned by soaking in sulphuric acid. The strip of paper, or tape, which is unwound from the reel R I'ig. 70), is stretched by [jassing under a spring «, passes over the guide roller [i, and Flii. 70. — I'iipLT Strip and Drawiiij^-olV .\ppanitus. then descends over a projecting plate y immediately facing the point of the siphon A It is drawn onwards between two rollers 1^ ami e, the upjjer one receiving its rotary motion from the magneto-electric machine by means of the cord ^ and multipljing ]3ulle)-s l\ and the lower one being pressed against its companion (5 by the action of the spring on the bent lever «>. The tape is adjusted to the proper distance from the siphon by turning the mill-headed screw TT, and the tension of the bent lever spring is regulated by the nut A. WhiiJ-cord is the best line to employ for transmitting the motion, and when the two ends are tied with a reef-knot as in I*'ig. 71, the cord passes easily round the pulley without stretching. A slight elongation, however, of the cord will not matter, as the axle of the lower pulleys I' works in a slide, the weight of the pulleys being suj)ported b)' the bight of the cord itself* As dry paper would have too great electrical resistance, the paper tape Fic. 71 * 'n Tiiore recent forms of siphon recorder, the whip-cord has been replaced by leather boot-lace, or by an india-rubber thong of circular section. 2 T 6l2 SriiMAKlM': TI.LI.dKAl'IlS. used is soaked in ;i solution of 2 parts of nitrate of ammonia in ICX3 parts of water. The |)a|)er never i|uite dries, Ijeinjj l13 and i;' arc- in metallic connection with each otlicr, but insniatcci from the remainder of tlie apparatus. Tile princi|)ie of Varley's machine tells iis that if an electric char{,fe, however feeble, is ^nven to one of the pieces C,, and if the axis x of the mill receives continuous rotary motion, the charge on the inducer I will increase very (juickly. It is even necessary to cover the jjieces c, and the inducers with p.-iraffin, to prevent the sparking which would soon occur from one to the other. The axis ,\ is rotated automatical!)- by the electro-mai^iietic machine. To effect this a horse-shoe electro-maj^net !■ is jjlaced in a receptacle \' underneath the mill, the maijnet bein;j; excited by a local battery whose circuit is alternately clo.sed and broken. The heiL;ht to which the two cores of the electro-majrnet I project is dependent on the len.Ljth of the pieces c,. DirectI)' the circuit of the local battery is closed the ma;4net I attracts the piece C, nearest to it ; the current is inter- rupted when the armature c, has |)as.sed the poles of the clectro-ma[j;net. but the motion still continues for an instant or so, in \irtue of the ac(|uired momentum. As the next arma- ture api)roachcs the magnet, the circuit is again closed, this .second armature is in its turn attracted, and the movement of rotation ccjiitinues indefmitel)-. To effect the automatic make-and-brcak of the circuit at the exact instant re(|uired, a disc / (I'ig- 74) having the form of a regular decagon is placed behind the inducers and arranged to rotate with the axis X. Below this di.sc is a lever t t, pivoted on an axis f>; the end of the lever -ear on the "Central and South American " Company's V\c,. 76. — Siplidii Kicorclcr Sij;nals rev/// X'iliratioii. cables, and had proved of special value in working a section whose " KR" was 9.3 X 10", as well as on one of i 1.4X io".^$ In 1886 Mr Charles Cuttriss (electrician to the Commercial Cable Com])an}-) devised a similar plan. Here, a small style, drawn from * The application of this device iindei- such riicumstanccs is pecuharly to the point, for by its means tlic sensiti\eiiess is so far increased as to obviate the necessity of an increase in the battery power. t And also without any electrification of the ink, the siphon beiny drawn directly over the surface of the slip, thereby introducing considerable friction. + Vol. xiv., p. 343. !$ One of this company's officials, Mr F". P. Walker, subset(uently su^Kested, instead of attaching a fibre between the armature and the recorder suspension, that the armature should be made to ])lay directly on the fibre suspending the coil. This is found to be a convenient plan. It is then necessary that the fibre should be protected against abrasion, or else toughened. 6i6 SI ISMAklNK TELIXIKAI'IIS. very fine iron wire, is placed in the end of the siphon, and se|3arated from the armature of an elcctro-magnct by the thickness of the paper only. A special vibrator determines the excitation of the inrgnet at regular and rapid intervals. The style vibrating in unison with the armature of the electro-magnet withdraws a small quantity of ink from the tube at every impulse, tracing a line on the pajjcr formed of fine dots very close together.* Fl(".. 77. — Muirlicail's Iinprovoil Sii)lion KcCDrder. Later Patterns of the Siphon Recorder. — When applying the siphon recorder to their cables betvecn Marseilles and Algiers, the I'rench Postal * .Since then several other forms of vibratory devices have been introduced — notably those of Dickenson and .\sli. The description of a recent type, as supplied by Messrs .Siemens Brothers, is as follows : — A light iron reed is attached to the siphon-cradle and an electro-magnet is fitted on the frame, or bridge, with its poles opposite the reed. The electro-magnet is si(;nali.in(; ai'I'AKATl's. 617 Telegraphs adopted a modified form of this iii.,trument. The electrical (mouse-mill) method of iiinvindinLj the paper was abolished, and the ordinary clockwork arrangement (as in the Morse recording instrument) substituted for it.* To avoid shaking the siphon suspension, this drawing- off apparatus was i)laced on a separate table. Moreover, the curved i)Iate against which the point of the siphon presses — usually known as " the saddle" — was made movable in three different directions, so as to renrler it easily adjustable to the required position. These special arrangements were novelties at the time, it is believed, as well as those previously mentioned in connection with the suspension attachments.^ I'erhaps the latest ty]x; of 'Ihomson siphon recorder for work- ing long cables is that designed by l)r .Alexander Muirhead,;|: and of which i'"ig. "/"] gives a general \ie\v. In this pattern the com- ponent parts of the instrument are so arranged that the \arious adjust- ments of it can be more readil}' effected than in the original form. The most novel feature in Dr Muirhead's instrument is in the suspension piece, of which i"ig. "jt^ is a general view and Fig. 79 a diagram of the connections. Here the coil is connected by means of two fibres to the aluminium cradle to which the glass si])hon is cemented. The torsion of the stretched, phosphor-bronze, strip which carries the aluminium cradle and that of the two fibres together, give the directive force to the suspended coil. The apparatus § emplo\-cd by Dr Muirhead for imparting the neces.sary I'li;. 7iS. — Muirliciul".-. Sii>]iciisio]i I'iuoc. encryiscd intennitteritly by (uricnts from a primary battery controlled by an automatic '" make-and-break. ' The apparatus is provided with adjustments by whicli the rate of \ibration can be made synchronous with the natural rate of the siphon. * In still more recent patterns -as is shewn a few lines on -the electric motor system has been again returned to, though now as a se])arat(; machine for this jjurpose alone, the mouse-mill with its electrifying provisions being altogether a thing of the past. + Again, this was probably the first instance of a direct writing recorder, as used on similar short lengths of cable, recent forms of which are described further on. J: .See ))atent specification N'o. 20,793 "f 'i^yi' .!; liased on a patent taken out in 1S93 in the names of Alexander Muirhead and Robert Henry Kdgar. .See specification No. 3,4i.'? of that year. 6i8 srilMAKINK TKLKGKAI'IIS. vibration to tiie siphon consists of ;i small L'lcctro-nia,t,nict fixed at one end of the bridge-piece carrjini,^ the siphon suspension, whose armature is attached to the stretched wire on which the si|)hon rides. A vibratory current is passed through the coil of this electro-magnet from a makc-and- brcak a|)]jaratus constructed like that of an ordinary electric trembling bell. The jjair of coils on the bridge-jjiece which carries the siphon are connected in series with the interruptor, a battery and a sliding resistance. To get the interru])tor and siphon in tune, the weight (' (I-'ig. jg) is Fir,. 79. — .Miiirlicad's SiispLMisinii Piece: I )iai;ri\iii cif ('unnc-cliiuis. first placed in a suitable position, and the final adjustment is made with the screw D. A coil c. is fitted on the interruptor to ab.sorb the spark at the point of makc-and-brcak. In this device the clockwork for drawing the paper is replaced by a modern form of elcctm-motor placed at the to|) of the instrument, as shewn in the figure,* The motor is energised bj- a battery consisting of Thomson trays for gravity cells; equivalent to a total E.IM.F. of 4 volts. * Ordinary motors of small type li.ivc sexeial distinct advantages oxer cUx kuoik for this |)ur|)ose. To wit, the oinialion of winding, and, tlieiefore, of |)eriodic jars to the a|)|)aiatus. All siphon rccorileis as now made ami supphed Ijy Messrs Muirhead and Co. are furnished with siicli motors. SICNAI.I.IN'd Al'l'AkATlS. 6lO Mr I'^rank Jacob has cle.siL;nccl tor Messrs Siemens l^rotlicrs a stjincwhat similar suspension piece. The makc-and-brcak of the electro-ma.L,niet, lio\ve\er, in this case inxolvcs the \ibration of tiie siphon onK- instead of the entire cradle, as has been already shewn. Mr Charles Cuttriss, of the Commercial Cable Com|)any, has also de- vised a modification of the Thorrson siphon recorder in a verv convenient and efficient form, and this instru nent — a t^eneral view of which ma\- be found at the end of this section (p. 630J — is in use on the Commercial Company's Atlantic sj-stem. Installation of the Apparatus and its Connections at Sending and Receiving Stations. — .\s the ])o\ver of checkini; messa,i;es at the Vu,. So. — Si|ihiin Kccnnlcr Working. Stations from which they are despatched is an inijiortant point in the ))ractica! working;' of cables, the current which actuates the receiving; instrument at the distant station is in " recorder " workint,^ almost invariably made to first traverse the apparatus at the sendini; end. On account, however, of the (rj-eat delicacy of the si|)hon recorder, onI\- a ver\- small portion of the line current is permitted to pass tlu'oULjh this instrument at the home station. .\n ordinary slide resistance K (Fig. ^. It may be mentioned, however, that if a cable be very faulty, even though the further end be insulated, signals may l)c noticeable at the sending end. To effect the same result in ditf>h:\ working special arrangements rei|uire to be made. SI(iNALLIN(i AI'I'AKA'ns. 621 accordint; to circumstances, is inserted between the terminal l!._, and the earth. Tile current, at the start, divides into two jjarts which reach r., and I!., simultaneously ; at i;, a further division takes place, the lander portion ^oin of the recorder. The number of cells used for signal- ling natural 1)' \arics with the length of line. Between Marseilles and Malta, a distance oC S^4 miles, four to fue cells are enough. On the Malta-.Ale.vandria section, (j2/ miles in length, eight to ten cells are Ibund necessary. •'I.„ ,Si. Permanent Magnet Recorders. — In 1884 a new form of Thomson siphon recorder was introduced which rendered it suitable for working * Of late often replaced by dry cells of extremely low 'ejistance and great staying power ; or preferably liy acciinuilators, as the former sometimes fail — especially in hot climates. Where so small a portion of the charge is employed for doing work, increase in E.M.F. will produce \ery little increase in speed. On the other hand, reducing the battery resistance is of paramount value, as a greater rush of current into the line at the first moment is thereljy secured. It is on this account that the abo\e forms of battery are employed where high speeds are aimed at through a given caisle. The insertion of conder.scrs for signalling purposes at the receiving end of a cable, and still more when, as is usual, they are placed at both ends, involves a somewhat higher battery power. 62: srHMARINK TKI.i:(iRAI'll.S. cables of moderate Icngtli, as \ve!l as on \o\v^ cables. In this niodification, the electro-maiijnets M (see l"ig. 66) are replaced by permanent magnets, the mouse-mill being completely suppressed, and the rheostats R, and R., as \vi;ll as the two local batteries dispensed with. A general idea of these simijlified instruments, with their connections, is given in l-'ig. 82. Here the siphon has to be of somewhat larger diameter so that the ink may circulate by its own weight, without being carried on to the paper b\- the flow of electricity as in the more complete apparatus. The strip of paper Fli;. S2. — Siini>lirii'(l CiiiuK'Cliiins, with Mixlirii rLTiiKincnl Mai;- net Rcccirilcr fur liiniu-il Icnjilhs. l-'li;. iSj. — Tlioiiison Si|;lii;ii IxL-conli-'r : .Simplilicil IVnii.TiK-iit Miip'K'l l';Utcrn. is drawn past the siphon by clockwork. The general appearance of this instrument is shewn in Fig. S3, also, in section, b_\' Fig. '^\. This form of recorder (with permanent magnets; is, with all its modifications, by degrees entirely replacing the olfl electro-magnet form. Again, Fig. 85 serves to shew a recent t\pe (jf |)ermanent magnet recorder adopted by the I'rench i'ostal Telegraphs for their Government cables, with the side adjustment tt) suspension piece as already referred tt). SI(;NAI.I.IN(i AI'I'AKAIUS. 623 Direct Writing Recorders. — On short cables, where it is not necessary ti) vibrate the siphon Ton account of tlic greater strcni;th of effective current , and in which the rate of signalling adopted is not near the limit at which the cable can be workcil, modifications of the Thomson recorder in the form of direct writing siphon recorders are used. .A convenient pattern of such an instrument, designed by Dr Muirhead, is shewn in i'"ig. 86. The siphon in this case is attached to an aluminium frame fastened to the 'm////mM//M/m///M//:"//m' l-ic. 84. cB* ^^m 1 li.. S5. — I'cmiaiiciU Maj^net Uecordcr, with .'>iile Adjustment to Suspcnsidn Piece. coil itself which is suspended bifilarly top ami bottom ; the lower filjres can be adjusted laterally, and there is also an adjustment for varying the tension on the fibres themselves. The platform over which the i)aper passes beneath the marking end of the siphon is in this instrument provided with adjustments in two directions, so that the paper ma\' be raised up into light contact with the siphon and levelled to suit the movements of the siphon. The direct writer being free from "jars," as much as 120 words per minute — and even more — have been 624 srnMAKINK ll'-.I.KCKAIilS. obtained on tliis form of siplion rccorclL-r, the siL;nals beiii^", inoreoxcr, well defined.* In tliis device the paper is drawn by means of a small electro-motor. The motor is conveniently placed at the side and provided with double gearini;' actinj; directly on the paper draw-off, the object of this double i;carin^ bein;^ to extend the range of s|)ee(l at which the paper is required to travel. Fill. S6. — Muirlicad's Direct Writini; RccurdLr, fur Slmrt C'alilcs. This instrimicnt is well ada|)led for high-speed work on cables up to ., . , .1 r 1- I07 lbs. conductor ,. ,, l,ooo miles m length of ordmarv core, „ . , Pcr A.M. 140 lbs. msulator .Another impro\'ed fcjrm of short cable siphon recorder, with clockwork mo\-ement, as made by White of Glasgow 'the maker of all Lord Kehin's in\entions;, is shewn in iMg. S7. This instrument is pro\ided with a comparatively small, but strong, permanent magnet (in horse-shoe, instead of long straight bar magnet, forin\ and is conveniently fitted with "send- ing" and " receiving " shunts. The whole ajjparatus has a very compact appearance. * On an enicry^ency the speed with this instrument has approached something like 200 words a minute. SICNALUNf. Ari'ARATlS. 625 The Smith Switch, or Commutator. — The lever commutator in tlie Thomson recorder is sometimes replaced by an a|)|)aratiis dcsij^ncd by Mr '''^^t^^■|^'^'' I'IG. S7. — While's Diix'Cl Writing; Siijlmn I\L-ci)rilcr. l^Mijamin Smith, t,nviii_L;" |)rccisely the same connections but in a neater manner. I'v^. SS shews the internal arrangements of this, and I'Il;". S'j an Figs. SS .ind 89. — Benjamin Smith'.s Recorder .Switch Key. outside view. It consists principally of four cro.ss arms which butt against stops fitted with contact pieces when rotated horizontally by a lc\er or 626 sriiMAkiNi: Ti;i.i;(.KAi'iis. handle mDUiitcd (in thi: same vertical axis. The connections are estab- lished as in I'v^. 90. In the position shewn, the line is in its normal condition, directly to earth throii^di the commutator. To place the contacts for scndinu;, the lexer is drawn to the left, and it must be mo\inl over to a corrcspondiiiLj position on the riLjht when chanL;in>.( to the relieving position. The condenser, in this installation, is not situated between the line and the receiver, but is placerl between the receiver and the earth ; thus onl)- the signals received come throuj^h the condenser. The result of this arranj4e- Line V\v,. 90. — Kecorilcr Conrifctions with Smith's Oimmutalnr. ment is that the cable and condenser remain constantly at about the same potential, and experience jjroves that the work of sendin;^ is thereby facilitated. The small commutator between the cable and the instruments is intended for puttinij the line to earth so as to cut out all instruments either durini,r storms or for testini,^ purpo.ses. Manual Translation. — Mr H. Smith designed his switch more espe- cially for purposes of ready manual translation at an intermediate station. Manual translation used sometimes to be known as the " human relay system." Even in the early days of land telej^raphy, before the Govern- ri.ATi: XXVII. e B' am 3. I Cam 4. e «*0 e s' s»@ ^ Zl 3 o TOU Clear R FROM L' T TO L* ELLIOTT BRO* LONDON. I'l'.. lit. K:iviiiiinil.H;iiki-i's Translaliiin Swiicli for CaMc CirciiiN. I Vo/.uY /. (>2y. SK.NAI.l.INC, AI'l'AkATUS. 62/ mcnt took over the tcle^niphs, systems of manual translation were in voL;ue in tlic absence of automatic relays. It was, in fact, very soon dis- covered that an immense savini;; of time and labour — not to speak of a reduced chance of error — occurred when the clerk at an intermediate station sent off the nicssa;j;e to the required station diiect from the Morse slij), instead of writing out the message and then handing it over to another clerk to retransmit it on another circuit. .Mr .Smith set his mind to orj^anisinij a similar complete and retjular s\stem of hun.an translation, or repetition, for submarine cable circuits where an electro-mechanical relax- is impracticable, it was mainl)- in order to meet these requirements in a read\- formj for the I'^astern TclcL^raph ("ompan_\'s sxstem of cables that Mr Smith's switch was designed, as abo\e d-\scribed. Mr I^. Ra\-mond-Iiirker also de\ised a commutator, or switch, to meet the same purpose, anil this is ver\- larLjjeiy used by various other companies, bcini^ an exceedini^ly efficient and compact affair. Fig. 91 re])resents a general plan of this instrument. rile \'arii)us conditions, as regards connections, under which the s\\ itch can hv turned to account, in the case of a re]:)eating or translating (inter- mefliate) station on the one hand, and in that of a terminal station on the other, are clearl\- shewn in I'^igs. (J2 and 93 (see Plate X.W'III. overleaf).* As already stated in connection with the mirror s)'stem, \arious cable transmitting ke\s have been devi.sed from time to time. The improvements on the original reversing ke\' (similar in principle to that used in pre- historic needle-signalling days) consists mainly of greater excellence of wori 180 , the left-hand spring is insulated b\- the eccentric and the other two make contact. During the rotation of the commutator there comes a time when all three springs are making contact simultaneousl)', but this onl\' lasts for a moment if the handle is worked ciuickh-. This arrange- ment, as we shall sec further on, facilitates the discharge of the cable. The entire apparatus — e.\cept the commutator handle and the tajjpets — is enclosed in a round brass box with a glass top. The connections are made as in Fig. 95, where U, and v., represent two xariable resistances containing four coils each; the resistances of the -'/; ncfu; I-, ■h -m h 1' I'lc;. 94. — DiL-kensDn's Trans- iiiitting Key. coils in U, are rcspecti\el\- i, 1.5, and )hms ; in u., each coil has an etjual resistance of 500 ohms. The latter rheostat, as we have already explained, serves to deaden the oscillations of the coil s of the recorder, the least effect in this direction being obtained w ith one coil, and the greatest effect with all four coils in circuit. The current at the sending end — or a portion of it, at least — is made to traxerse tlu' recorder coil .s for facilitating the checking of messages, as previousi)- narrated. The commutator being in the receiving position ^which is the one shewn in the figures), if a charge of electricitj- arrives through the cable at the condenser C, a charge of similar sign is set free from the opposite coating of the condenser. This charge dixides into two |)arts at the rheostat I'.,, one part .going to // through the coils of L„ which are in circuit, a'ul the other orders I ^ Kacdr Z [Plate XXVIII. ] Cablt L' fiecdr. I Recdr2 f k' K' f I — l-o., 4---^^ /?' fi' t' o. ikl>[g.. o o 6,..v6 IT fl /rom L' ^,. R from L' T ro L ^'"' T to L' \Working Reeorder 2^ RfromL; (./„^ T to L left on left on (Clea [;■ Connections for one Recorder, with ^1 Cable " Recdr i^ iiii»J R' It' L 6. .a .-o :0 « from L' Clear " '"'"'"" ^ r to L T to L' Iff' left on L ~\ \r' left on L' J (Clear) Cable ' H Connections for one Recorder, with varyir s; cT^Reedr m • J» ^acrfr 73f^ |I|i|i|i|i|i1i|i|i1f'- A" /(•• /?' H\ L' S' t>, i 'S^ ISS®' i i 9 ! ■^ Cable L' Cable m S' |l|l|l|l|l|lil|l|l|l|M^ y K' /?' fff A' o.Nx:iD,,.^-cr~T7,.o- |i|£>5] witli DiikciiM.ii's Key. On chan;j[inL;' to the sendiiii; |)osition b)- turnini;- over the handle ;■, we .sec that, at the instant when the three s|)rin^s are simultaneously ])ressinL;' on the contact piece, the cable is in connnunication with the earth throuj^h the condenser C, and an\' i)ortion of the chari^e still remaining- in the line can readily escape. Now suppose the knob of tlie lever A, be depressed, the nei,sitive current from the line batter}- I, I!, leaving the pole :, pas.ses throuL^h ternn'nal No. 2, the ujjper contact of the lexer/.,, the upjjcr contact of /, through terminal No. 4, and so to earth. The |)ositi\e current, IcaviiiL;' the |)olc l\ passes throus^di terminal No. 3, the lower contact of /.„ throui,di this le\er to the rear right-hand spring, and so to the contact piece against which the two springs on the right are pressing. Here the electricity di\icles into two l)ortions ; one part being conveyed through terminal No. i to //, where a further divi.sion takes place, one portion traversing the coil.s of the rhecstat I'., which «u'e in circuit, and the other part going through the recorder coil .s to rejoin its fellow-current at the axis of the rheostat L'„ ; the second part of 630 srnMAKiNi: iin.r.c.KAriis. the i)rinci|)al cuneiit on IcavinL,^ tlic contact |)iccc, passes through tlie fnmt rij^lit-liaiul spriiii;- to terminal No. 6, whence to tlie rlieostat l'.„ and fmally to the axis of r.,. Tlie now rcunitetl cnncnt llows with its full strcnj^th into tlie condenser (', immediately |)recedin}^ the cable. The resistance in circuit of Uj bein<; alway.s very sli^lit, the greater |)ortion of the current traverses this rheostat from the first, so that the current passing' throui;h the recorder is of no f:freatcr intensity than that recei\ed from the distant end. The circulation of current ])roduced b\' tlepressin^f the other lever /, is precisely similar but opposite in direction. II, is a local battel}' which ser\ es to e.xcitc the electro-niatjjnets M \|. .Another vcr}' excellent combined key and switch is tliat of Messrs Peel- iiiLj and Davis, which serves for recording sent as well ;is received inessai^es. The Plate opjiosite (I'ig. 96) represents the connectiiins at ;i recorder station as recently furnislied by the Silvertown Company for the South American Cable Company, and maj- be taken as a Ljood exam))le of others. As may be seen in the drawintj, the sii^nallini; condensers are arran<,red in /ii >■/!//(■/, according to itnariable custom, in order to securt' the sum of the capacities of each.* * Trouble is sometimes experienced with these— especially in tv()])ical climes. The insulation has occasionally j,fone down from about 800 to about 150 ohms pur N.M., due to a rise of temperature from 65' to 75 F. By the same temperature increase, the capacity lias also materially increased on occasions. It would seem as thouj^h a warm temperature brinj;s about a chemical action in the wax which alters its specific qualities as rcj^ards insulation and inductive resistance. The .Siphon Rcconlcr : Ciutriss ratlcrn. [Platk XXIX. [To face p. 630. [Platk XXIX. ^1^ r'l i1 5| rl l^-s? *SSs n js ■ ■■ •c 10 Uj — r jr " .' J r I. o « «- W S » -si 3 e a S CO \Tofacep. 630. I '^ »;i '■ ■■ f, » i'i ' o ii:^. ^c, --f-.-^ 3 3 r ' t , h. ;<-4 SI(i\Al,Ll\(; AI'l'AKArUS. 631 SixTiox 5. — Otih.k Similar Ai-pakatis. Lauritzen's Undulator. — Tliis ;ipi)iiiatiis, which lias certain points of similarit)- with tlic siphon recorder, is chiefly used on the submarine hues of the Great Northern Tclej^raph Compan\-.* It consists principally of four straight electro-magnets i)laced at the four corners of a scjuarc (I'itjs. 97 and 98), the coils of the maL;ncts beins^ joined u|) in ore continuous circuit. The direction of winding is the same for the coils situated in the same diagonal, and opposite to that of the ct)ils in the other diagcmal. The |3oles, for instance, at the ui)])cr ends of the cores, with the same current, will be north for the diaj^iinal \, N, and south for the diagonal s, s. In the space between the four electro-magnets are four ver\- light steel magnets, ti|-. poles tx\ c\ I' and t retransmission. where the telegram is read direct from the slip, and the delay and risk of errors occasioned by the copyinK of the telegram— previous to retransmission —thus avoided. The receiving SICNAl.LINC Ari'AKATlS. 633 The Ader Recorder. — Just as this book goes to the press, an in.t:,rcnious aijparatus has been deNised by M. Ader, niakinj^ use of the principles of photoL;raphy. Here the coil of the siphon recorder is superseded b\' a long fine \ertical wire through which the current |)asses. As the wire is drawn from side to side b}- the poles of the magnet (in the field of which it is stretched; a ra)- of light from a lamj) throws its wavering shadow on a travelling stri|) of |ihotogra|)hic paper — automatically de\elopcd lii passant — in the form of an undulating white line (on a black ground), representing the signals of the message. This apparatus is claimed to be mf)re sensitive than any preceding instrument, whether sii)hon recorder or mirror. It has iicen tried on the French Atlantic cable between lirest and St Pierre, the result being 600 signals per minute instead of 400. It is reported that with this sx'stem New \'ork and I'aris are shorth" to be put into direct communi- cation. It may, of course, turn out that the sinuous line on the sensitised paper is more troublesome to read than the siphon-recorder line, but this is scarcely likel\'. The absence of the friction between the si|)hon and the ])aper, together with the small inertia of the moving parts, are advantages that ought to be brought to account — if onl\- on the score of legibility. Again, its simj)le construction as compared with the siphon recorder, and the absence of a vibrator (which frequently gives trouble and requires close attention in order tf) maintain a regular rate of vibra- tion and scnsibilit)- , are additional |)oints in favour of M. Ader's instrument Altogether, there seems little doubt that the idea f)f recording messages by photographic means will be largely adopted in the future — at anj* rate for working verj- long cables. h'urther, it js somewhat surprising that the application of photography to the deflections produced on "dead-beat" reflecting galvanometers and on the mirror " speaker " has not \ct been turned to account in practice as a means of avoiding the Oitigue experienced by the eye when following the rapid clerk, by means of the " dcxtrincur,"" ( an rereiv* mcssajjes faster, mi>rco\er, having' no lon-e tape to .ittend to. Where the " dextrineiir " is in use, immediate manna! translation (as read from the slip) is of course impossible. This apjiaratus is partly intended for the purpose of preserving all the slip in each messaj,fe se])arately — for possible checking or reference — in a convenient form. Thus, wlicn a messa;;e arrives, it is — as fast as it comes — gummed on to a siieet, then written in Knglish woids b\- a clerk, this word copy being delivered to the person it is directed to, the original gummed slip las received i being at the same time filed, instead of the ordinary word copy and loose slip. In the case of an intennedi.Ue station, the clerk translates— /.('., repeats on - from the slip ready gummed on to conveniently formed sheets. 634 SrUMAKlM-; ll-l.ia.KAl'llS. muvemcnts of a biiL;ht light.* It is certain that the much smaller move- ments of a spot of light — such as would sufficiently serve if recorded by photography — would enable a much higher s|)eed to be attained than with the comi)arati\cl)- large amplitude reiiuircd fc^r visual tclegra|)liy. Indeed, the extreme sensibility which rellccting galvanometers are capable of justifies us in anticipating by this system an even higher speed than that already claimed for the Ader recorder. With reference to this latter, again, those who have e.\'perienced the difficulties of deciphering recorder sli|), following the trail of a nervous, sinuous, line, will greet the photographic method cheerfully, as me uf gre.it |)r()mise. ■"' The apiilicaiion of i)h()t()i;rapliy to ilie purposes of recording mirror signals was actually suggested Ijy Mr H. (i. Clieesenian as much as twenty years ago ; and devices based on this ])rinciplc have since been patented several times by varicjus people. Western ami lira/ilian TclL-grapli Company : Landing I'lacc at Rii) di' lanoiiu. CHAPTER III. DUl'I.KX TELEORAl'HV.* SixilON I.— History— Differential Principle: Wheatstonc liriilj^e I'linciple X'arley's Artificial Cable : Steams' Method— De Sauty's Method. Skction 2. — Modern Practice : Muirhead's Inductive Resistance : Muirhead and Taylor's Method: " Double-Block '-Practical Examples and Installations: Duplex Direc- tions for Short Circuits : Duplex Directions for Long Circuits — Comparison of the Principal Dujilex Systems - (^ther Methods : Benjamin Smith's : llarwood's : Jacol)'s : Aiihaud's -Comjjarison of X'arley's and Muirhead's Artificial Line— Similes of I)u|)lex TelcHrajjhy. <,)uadruplex and Multiplex I'",xperiments on Cables. Sr.cTioN I. — Historical Ski-.tcii. DUI'LKX tclcgnii)Iiy is cunstitiilccl b_\- tlic simtiltancoiis transmission of messaj^fcs in both dinxtions from cacli ciul of the conclucting line. The principle of tliipicx workint; is to render tlie receiving instruments insensible to tlic ciuTcnts sent into the cable at their own end, whilst tliey faithfull)- record all signals coming from the distant station. LJ|) to the present this problem has been solved mainl)' in two ways, one or the other of which embrace all the special methods suggested b\- different inventors. Firstly, the dilTerential system, dtic, in principle, to l)r Gintl, of Vienna, who in 1853 first shewed in a practical w a)- how it was possible to send two messages in opf^ositc directions, on tiie same w ire at the same time. In the following )ear 11^54} this system was perfected by IIcit C. Fri.schen, of IIanover,t and adopted in the .same year b)' Messrs Siemens ■*■ An entire chapter is devoted to this subject (l)esides being referred to somewhat fully in Part I.) on account of its vast importance — /'.('., its immense bearing on the earning capacity of a given line. But for the duplex system, as now |)ractised, we sli()ukl rei|uire many thousand more miles of cable to carry our mess.ages here, there, and everywhere. t In this year (t854) R. .S. Newall includetl in a patent a method of telegraphy such as would be now described as "duplex" telegraphy, and was at that time spoken of as a doul)le-speaking system. It is referred to in Part 1. of this book. This claim was '" for the arranging or combining of electric telegraph apparatus in such a manner as to render it possible to telegraph simultaneously in opposite directions between two stations, using one line wire and the earth as the means of communication." This formed the first Hiiii/ish patent for duplex telegraphy. The second English patent was that of the 636 SII;M.\K1M- 'lI'LI-CkAl'IIS. and Ilalskc, parti) in virtue of a sonieuliat similar patent of l)v Werner Siemens. Secondlx', the W'heatstone bridi^^e system, the idea of which was \a;j^iiel\' put forward in 1S5S by Mr I'"armer, an American, and clearly- demonstrated in iSf^)^ by M. Maron, of Berlin,* wlm, however, ne\er broui^dit the matter to a practical conclusion.''" The differential .system entails the use of receivers cont;iinin_Lj two coils, the wires of which are wound in opposite directions. l)r Gintl's method was to join uj) one of these coils to line, and the other to a suitably adjusted rheostat. L'sino- ;i double contact ke_\-, he was able to send cinrents from two distinct batteries, through tlie two circuits simultaneously, the effects of the two currents on the receiver at the sendini.^ end mutually cancelling one another. Messrs I-'rischen and Siemens ;J: also wound the two coils of their receivers op])osite ways, but they made them of exactly e(|ual resistance, and placed them under identical conditions with rec^ard to their influence on the ma_L;netiseil neetlle. The two coils were joined up at one end to the same battery I' Vv^. loo,, the other end of one coil bein;;' connected to line, and the further end of the second coil to a resistance K, equal to that of the line. The batteiy current fmm I' thus divides into two (.n|ual parts whose effects on the needle of the receiver (; mutuall\- cancel each other. The current from the distant station, on the contrary, _i;oes to earth either by passini; successivel_\-, antl in the same direction, throu_L,di the twu coil circuits, broiliers Hris.;])! Preferred to flscuhcre), .ind tlie third th.it of Mr \V. H. Proece(i855\ this latter huing a dit'tereiitial ^xstein. Mr Prccce has always been closely idcntitied with duplex telegrajjliy : in 1879 he j.;ave a series of Society of Arts Cantor Lectures, which inckided one on this subject. This formed the most complete account of duplex icle- ^'raphy in existence, put in such a way — as is his wont^that the uninitiated Could readily follow him. .See A'//;'. Soi. .l//s. \o\. xxvii., |). A9MAaMSUU>- Fli;. lOO. — Duplex Tclegrapliy dh the Dift'crL'iitial riiiKi|ilc. system of duplex telegraphy may be likened to a "tug of war." When both sides are equally strong in the latter, no matter what ]30wer is used to pull one way, if an equal power be exerted to pull the other, there will be a neutral result, or zero indication. So it is in a '' differe:itial " instrument, Line MjlisJLilSJlAS- Fu;. lOl. — Duplex Tclc^;ra|ili)- on the Whe.-vlstcme Bridge I'lineiple. whether it be a galvanometer or a rcla\-, the object of which is to divide the current equally but o])positely, and thereby to produce no effect, however strong the currents sent through it may be. The rheostat and other means of final adjustments are emplo\-ed for balancing, in this as in the bridge system about to be described. 638 srnMAkiM-: I'Ki.i-dkAnis. In till' W'hcatstonc brid^rc s\-stciii (Fis^. 101,,* the line forms the fduith arm of a brid^^e whose dislant an.^le is lo earth. The resistances K, /•. and /■' beinii; adjusted to t;i\e a balance, the jjoinls I! and C are at the same potential, and the current from tlie battery 1' cannot traverse thi' (HaL^onal lie. It is evident that if the receiver c is placed- in this diagonal, it will not be affected by the current of tlie sending battery, but will be able In reproduce all si_L;;nals sent out from the distant station. S|)cakin^ L,renerall\-, an adv;intaL,'e in the bridge system lies in the fact that ir)/y kind of signalliuLi; instrument can be used ; whereas in tlie "differ- ential " system an instrument with diffei'entiall)- wnund coils is, of necessit)', inxohed. The practical difficulties in the ap])Iication of either one or the other of the abo\e methods are caused b\' a sharp throw, of short chu'ation, communi- cated to the needle of the receiver each time the circuit of the batterv 1' is broken and closed. The alternate dellections, opposite in direction, are due to a flow of electricity every time the line is charj^cd and dischart,red. They have been practically entirely eliminated so far as rcL^ards the duple.xing of overhead wires by the special a|)plication of conden.sers to a dui)lcx circuit as first instituted b\- Mr j. H. Stearns, of America. Uy this means the How of electricity due to the line charging; and discharging is exactly balanc(.;d 1)\- the op|)osing rush caused bv the charge entering and lea\ ing the condenser.+ Submarine cables, having considerably greater electro-static cap.icity than aerial lines, ^ retain a much larger charge ; besides which, they are worked with instruments of greater delicacy, so that the balance in their case is much more difficult to establish and maintain. * For the sake of simplicity and clearness the keys in the first few (theoreticab diagrams of tiiis chapter are represented as sinj^le-lever contact keys. In actual practice, the signalling key is, Iiowever, a double-lever arrangement on all cable circuits unless the Morse system is in operation — which is pro1),ibly never the case where a cable is duple.xed, except in the instance of such busy short lines as those constituted by the .Anglo-Conti- nental and the .Anglo-Irish cables. Similarly the receiver t; is shewn as a galvanometer in these first lew diagrams. It need hardly be remarked that in the case of a submarine cable, the receiver would be almost invariably cither a siphon recorder or a mirror instrimicnt —as a rule t!ie former. Thus, in later diagrams a recorder is shewn for the rccei\ ing instrument. t Mr Stearns' form of artificial cable — embodied in his patent for diiijiex telegraphy of 1872— was, in actual fact, precisely the same as Wirley's plan of representing a cable by .illernate resistance coils and condenser (tinfoil and paraffin paper) for the purposes of reproduction at the sending end in order to obtain an idea of what the signals would be like at the receiving end under gi\ en conditions as regards battery power, etc. I Indeed, owing to the distance from the ground at which aerial land telegraph wires are usu.illy erected, overhead lines have, |)ractically speaking, no electro-static capacity excepting in very wet weather. i>n i,i:n 1 i:i.i:(;k.\i'II\' 639 ♦ lluis, tlKiiiL^li ;i C(in>ic!cral)lc number (if land lincN liad been duplexed, it was not until after Mr Stearns concei\cd the plan ' b\- his ])atent of iiS/j) of insertini;' condensers in the artificial line, so as to re|)resent the capacity of the cable — in addition to the resistance b\' resistance coils, as in land- line tlupIe\in_L( — tiiat an\' material lenG;th of cable was duplexed. In duplexint; the short sections of one of the "Anglo" Atlantic cables in 1X73, ;md the main section some time afterwards fin 1S78!, Mr Stearns ailoi)ted the differential system, as previously adopted by the I'.O. 'I'elegraph Department. ■*■ This was effected b\- the si|)hon recorder bein^ furnished with two separate differentiall)' wound coils, each wound doubl)' according to anti-self-induction principles. I'ractically all the other submarine cables which ha\e been duplexed — almost entirel\- In' Messrs Muirhead — have been duplexed on a W'heatstone bridge basis. As stated before, Mr Stearns' arrangement was in effect a precise reproduction of a plan of Mr C". 1'. Varley (|)atcnted in 1X62 ^ for repro- II TiTiinn i Fic. 102. — Narlov's Artificial I.iiR'. ducing at an\- station what occurs in the cable in question — at any rate, as regards the manner of building up an artificial line by what is termed a * In .Anieiica tlic_\- had worked their land hnes on tiie duplex system, without any sort of condensers, as eailyas 1867,10 i)e followed by the Euiopean C(>ntinent. Cieiniany was, however, undoubtedly the first country to employ any form of duplex telet;ra|)hy, the ditTerential system of Frischen and Siemens being adopted the very year -1854— in which it was invented, from Hano\er to (aittingcn, and gradually on a large scale. The duplex telegraphy was not taken up till several years later by the I'nitcd Kingdom. This was gradually after the purch.ise of tlu' land telegr.i|)hs by the Stnte in [S70. Previously the "Electric"' Company had employed the Whcatbtonc automatic system for press work ever since it came out in 1864; and they did not retjuire to work their lines by a duplex method, with the traffic of that time, for any other circuits. I When the duplex system was taken up by the Postal Telegraph authorities, the plan .adopted throughout (as now* was the differential method, on account of its simplicity, and owing to the fact ot" a form of differential instrument iinenlcd Ijy Cromwell X'arley about 1850- being in very general use in the Cnited Kingdom (Government Telegraphs. The method of Mr Kdcn was the first employed in England. However, no efficient or continuous duplexing even of land lines occurred until Mr Stearns made known his method, in 1872, for the application of condensers to the compensating circuit to represent the capacity of the line- small though it be in the rase of aerial wires. I See specification N'o. 3,453 of that year— a "master patent'' — the second claim being for ''employing a 'test circuit ' formed by ' induction plates ' and resistance, so adjusted to each other as to produce an artificial line, possessing the same amount of retardation as the cable itself" 640 sniMAKiNK 1 i.i,i;(,K,\nis. "step by s'lL'|)" dcvicf,* as shewn licic in I'ii^'. 102, and a^ain in I'i^r. 103, in Mr Stearns' arranj^cnit-nts, the two circuits (if tiic rcconler cnii had cacli a resistance of about 250 ohms. The artihcial line which jjalanced tlie cable vl'i^. 104 consists of a metal rihaml lia\in;4' \ery considerable specific resistance wound round aimther thick cord and afterwards covered with the thinnest possible la_\er of an insuiatiiiL; substance possessint,' ^n'eat ~n -ps -p -p V\i,. 103. — StL-ariif.' Arliliiial Lines. inckictive capacity. The balance is rej;ulated by xaryin^^ the resistances r and /•', a resistance bein^ inserted between the condenser C and the cable, in case of need. The stren.:.,fth of the arri\al current throu!.;li the recei\er can be diminished by connecting terminals 1 and 2 with a shunt. In duplex teleL;raphy bj- differential systems, the battery forms part of the circuit when the ke}- is down and a signal is being sent ; but as soon as Ciible I'lr,. 104.— .Stoains' Duplex Methoil. the signal ceases, the battery is no longer a portion of the circuit. All batteries — even those used for duplex cable signalling — possess some, though vc)' little, internal resistance. This item is .sometimes provided "■'' Mr C. F. X'arley's patented artifirial caljle was beautifully described by him in tlie Royal Institution lecture of 1867, prcvioush' referred to. It is, however, a question whether the \iews there stated did not origin;ite with his brother, Mr .S. .A. X'arley. in I'l.ix ri:i,i;(.k.\nn. 641 fur I)) inserting bctwcun tlie Ul-j- and the cartii .1 rc>i--t,mcL' coil vi\ua\ Id iIkj internal resisiance of the battcrj-, so that whether tlie l'in^f his system in the early (la\s. It wotild, however never now be put into practice, as rc^^ards submarine cables — with the double-block Whcatstonc bridj^e system —for the battery resistance, besides beini; exceedin^l)- low, does not come in here. Mr Stearns met with verj' considerai^le difficulty in obtaining,' anything like a permanent balance, accordin^f to the principles of duplex telegraphy, on the -saort lenijth he first exi)eriincnted with, and still more on the inain section.* This difficult)' was no dotibt due to the lar^'c number of points of contact (and corresponding terminals) between the conden.ser and the resistance coils involved in Varley's artificial cable, as adopted by Stearns, thus introducing; the liability of vari.ition to a larj^^c extent, thoui,rh — in theory— the finer the sub' balanced line might be understood, and the number of words carried each way by the cable on 'duplex" was nothing like the theoretical double number of that on " sim|jle.x." i^ * No douljt the only reason tliat an electrically lonj,' cable is often t'ound to lie nioic difficult to accurately " balance" than a short one is that in a lony cable a more hij>hly sensitive signalling instrument (^siphon recorder, or mirror) is employed than on quite a short line where the Morse or some such instrument may be in voj^ue. Thus, in the first case it is necessary that a more complete ,ind absolute balance be maintained las well as attained), the instrument in question beinj^ actuated by slight aileratioiis of the current only. But for the above fact, theoretically speaking, the longer the cable the more easy tlie balance, owing to the increased retardation of the line more completely deadening any defects in this respect. + In order to obtain the maximum capacity effect from a number of condensers, regaicl must .iKvays be had for the fact that the sum of the capacities )f each is onl\- secured when they are joined up in parallel. \ This has, indeed, actually been urged as an advantage for this species of "artificial" over that of Muirhead, where the resistance and capacity are formed in one. It must, however, be remembered that the latter offers extremely fine addition.il methods of adjustment : thus, any such claim appears to be scarcely borne out in practice. S In 1881, in the course of a joint Report to the Submarine Telegraph Compan\- on Stearns' Duplex Method, Mr C. F. Varley and Professor W. E. .-Xyrton jironounced it t') be, practically speaking, unworkable. It should ise remarked, however, that at that time die system formed the subject of a lawsuit — Stearns 7'. Submarine Telegraph Company. 2 X 642 SI liMAUiNi; I i:i.i:(,K Ai'iis. TliL- l.itc: Mr ( '. \'. tk- Saiit>- is not imiisually accii'ditrd with having' accDinplislU'd tlir Inst diiplrxiii^' ofain- matiTial lcn;4th dfcable. I'his was ill 187^, on tin- submarine lino Ix-tuivii I.islxju and (iibraltar, ;!,C)$ N.M. Mr I)c Saiity iMnploj-cd the bridge nictiiod, iisin.Lj, like Stearns, tlie X'arley artificial cable the only form then known;, as shewn in I-'iij. 105 /.<'., a series of resistances shunted by condensers at alternatiu}^ points, thus constituting an imitation line haviiiLj lioth resistance and cajjacity, the prodiut of which should be the sami- in the "artincial" as in the ri-al cable to be balanced.* This first piece of duplexing,' by Mr l)c Sauty, though of much interest and utility experimentally, was not looked u|)on as a complete practical success in a permanent working; sense. Indeed, an artificial line of this nature, if it vSLSUU/ — T-^8 3. -T-^8 3Jb — r^SJLli^ |— T T ^ ^ [E] [El Fii;. luj. — I)c .SaiilyV MlUuhI. is to be .111 absolutel)' |)crfect etiuivalent to the cable, would roijuire a positi\ely unlimited number of subdivisions. This condition was fully realised by Messrs Muirhead and by Mr Herbert Taylor. Thus, in 1875 the difficulty was overcome in a most ini^cnious manner by a joint jiatent (No. 6S4 of that year) standin;^ in the names of Herbert Arnaud Taylor and Alexander Muirhead. This was for an entirely novel form of artificial line, combinini; throuL,di<)Ut, in one, the function of resistance and ca|)acity— as in a cable — instead of separately and alternatel}-.+ The result of this device ■'" .\ full (le->('ii])ti()n of Mr I)c .Sauty's (hiplcxini^ arrangements on this cable will be fouml in vol. ii., |). 138, of the Joi/niii/ of tliv Society of Tclei^niph Engineers, 1S73. + .\s a matter of fact, in the above patent, plumliago was specified ('by Mr Taylor, tlie originator: for the conductor and plates ; whereas tinfoil, previously and independently tried by Mr John Muirliead. has since been adopted in universal jiractice. Dr A. .Muir- head first devised the gridiron form for the conductor strip in place of a continuous length, and in substitution for ordinary plates condensers. The late Mr Robert Sabine 's also said to have Ijeen responsible for some gridiron type of condenser. i'i'i'i.i:\ ri:i.i;i,k Ai'iiN. "4,1 was tli.il (luplrv: in\)U- wurkiuM finm tli.it time became possible in pnutici' ; and tlie s_\-stem lias siiue been applied successively and succes-,rii!ly to almost all tlie cables iiou in operation at the bottom of the sea, tbereb\- increasinn; their workiiii; capacity, in the i)reseiit day, by some 90 per cent.-- /■<■., \cr>' nearlj- doiibliiiL; it. I'he diiple.\ system is, in fact, e(|iiall\- effectual when applieil to cables as in its application to aerial wires. .Si;( TioN _'. M()i)t:KN 1'k.\( tick. We will now proceed to describe the salient features of -.Mall: Section. .Seclion. F-ength in N.M. 447.66 848 Copper resistance - 5,210 (.» 9,632 <" Electro-static capacity- 128.7 •/' 238.241/) Insulation per N.M. 3.12412 2, 1 I 3 il Ill I'l.lA TKI.I'dKAI'IlN, 647 The arr;uii;cinciit of .ipparatus and connections was as shewn in I-'Il;. I I J. In the duplex installation of these cables Messrs Miiirhcad and Taylor, balancin,^' the cable with their form of artificial line on the Wheat- stone bridt,rc s)'stem, placed a condenser in the brid!j;e containing- the rcceivinji; instrnment, with a view to blocking off any possible earth currents. Balance was generall)' obtained under the followini;' conditions: — I*Kor<)KTi()NAi. Arms. C'.ip,-icily Caiii.ks. 111 tlie Receiving Upper. Lower. Ci>iitlenser. Marseilles-liona 1,000 (u 1,000 0) 4O'/' Nfarseilles-Malta 2,000 2,025 40 17.0 Aktifkial Line. i^esi stance. Capacity. .S.035 '" ')7-4 I 7,000 tt) 1 S.ooo 190(0230 On the Mar.seilles-Bona cable, 8 Leclanche cells were u.sed for signallini;" when successfully balanced by dui)le.\- apparatus, et|ui\alent to n.8 Daniel! cells; and on the cable from Marseilles to ]\Ialta, 22 Leclanche cells, ec|ui\alcnt to 32.6 Daniell cells. The workins;' speed throuL^h both these lines with the recorder and skilled operators was, almost at the outset of duplex work being effected, as much as twent)'-five Knglish words per minute each wa}-. At Aden, on the .\den-Hombay section, 1,817 niiles in length, balance was obtained b\- making .v (.see Mg. 112)= 1.23 microfarad, /•, = o, /-., = (\ ;-,, = 210,000 ohms (this last resistance being applied at a point 250 miles along the artificial line counting from the bottom), r, = 00, and r- = y-. T'e total resistance of the artificial line wa 11,827 ohms (about three- quarters of that of the real cable), its cajjacity 656 microfarads ; the resistances in the proportional arms were 2,000 and 3,000 ohms respec- tively, the first resistance being close to the cable, and the second one near the artificial line. At the Bombay end, />, = 2,005 <'hms, t>-, -.035, /-, = 60, r., = 120, /'.J = -J^, i\ = 175,000, and 1%^ = oi. The cable from Ballinskelligs Jiay (Ireland) to Torbay (Nova Scotiaj, belonging to the Direct United States Cable Company, was the first ocean cable to which the system of dui)lcx working was applied. This was estab- lished with complete success by Messrs Muirhead and Taylor in 1878.* * As already stated, one of the sliorl sections of the "Anglo" Company's cables had been ex])erinicntally (lii]il('\itl l)y Mr ]. 11. Stearns in 1873 ; hut not sufficient success was met with to warrant .1 long trans-Atlantic section of this company's cable system being "duplexetl '' till Hve years later. . 648 Sll'.MAKIM-: TKI.KCKAI'IIS. The leiiy;th of the cable is 2,423 N.M., its conductor resistance 7,315 Siemens units,* and its capacity 987.6 microfarads. At Ballinskcllij^s balance was obtained by making /', = 22, /^= 1,400, r^= 1,600 S.LI. ( = Siemens units), ;%, = cc, j-, =^o.o6(/), .v = 6o microfarads. The proportional arms were />, = 2,000 ohms, /(.^ = 2,036 ohms, the higher resist- ance being on the side of the artificial line. At Torbay, the balance corresponds to >\ = o, r.^ = ^o, ;-.,= 5,000 at a distance representing 1,600 X.M. of the real line, /-,= y~~, /•-^90,ooo S.U., •^1 = 4-37'/'' -^' = 60 microfarads, /), — 2,000 ohms, i>.y= 2,010 ohms.+ The ratio of the capacities of each artificial line at liallinskelligs and Torbay to that of the cable was .'. The working speed through this line was It d C» L mm ■i<;. 113. found to be about 100 letters per minute each way, or ver}- nearly twice the speed with simplex working. The receiver was a mirror galvanometer. The adjustment of the duple.K is more difficult with this instrument than with the recorder for two reasons. In the first place, tlie mirror being more .sensitive than the recorder, and the s|K)t always moving along the scale in a straight line, the lateral displacement of the zero may easily cause con- fusion in the signals ; in the recorder any displacement of zero takes place * 'I'lic Siemens unit is equivalent to 0.9434 legal ohm. + A. Muirhcatl, T/ii' Tclci^raphii' Journal iiiid Kh'ctrical Review^ 1879. mi'LiA Ti;i.i:(iKAi'iiv. 649 tnuisvcrscly to the pajjcr, and the le a slide resistance bo.v. A simple .system of commutators enables the changes to be made from simplex to duplex working, or from recorder to mirror receiving, and vice versa. To receive on the recorder, the holes marked r in the com- mutator l^ are plugged, and those marked g unplugged. The reverse oiK-ratioii is performed in order to receive on the mirror instrument. During simplex working, the holes marked .v in commutators I,, I.,, I^, I. l-'lc:. 1 14. MiiiilioailV rail) 'X Systoin, shewing " .\ililicial " Conncclions are plugged, and those marked d left ojjen. The key D, is used for send- ing, the lever of the reversing switch M connecting contacts i and 4. For instance, the left-hand knob of D, being depressed, the jjositive current goes straight to earth. The negative current, passing through contact No. I, divides into two portions at the lever M. One part, passing through I.,, 1^, the recorder s R and its .shunt k.„ I.„ and i,, arrives at the condenser c, ; the other part pas.ses through I.,, R,, and rejoins the first portion. I""or duplex working the holes .s- arc unplugged, and those marked d plugged at l|. I.,, I^, I-. The kc)' D., is in communication with a battery l'., of .somewhat greater power than i',, and is employed for sending. The switch M is not then in use. The manner in which the principle of the Muirhead and Tajlor artificial line is carried out in practice will be readily followed from l""ig. 114, shewing the working connections. 650 sniMAkiM, Ti:i,i:(;i<.\i'iis. Muirhead's " Double-Block." A\ liat is now know n as the " doublc- block " s\stcm of duplex formed the salient feature in the 1876 patent of Messrs J. and A. Aluirhead. This is constituted (Fif^. 115) b)- havinuj condensers in each |)roportioiial arm, for the double purpose of wardini; or " blocking " off earth currents and — in place of hi;j;h resistance — acting as a reliable " block " to the current so as to ensure a sufficiency passing (across the britige) through the recorder when signals arc to be received. Messrs Muirhcad and Taxior at first .so inserted condensers in the bridge arms in conjunction with a resistance UJ [To fa- is at rest, hold down the key and plug resistance in or out of the resistance coils at the end of the artificial line until the same zero, as at first observed, is obtained. Then perfect the balance fi^r " dots " by " pum|)ing " the keys and altering the rheostat and adjustment (1) and perhaps (2) as well, until the s|)ot remains motionless — or practically so. After making any change of adjustments (1) and (2; always ,dter the rheostat until the best po.ssible balance is obtained. Thus, su|j|jose the balance cannot be obtained .satisfactorily with the rheostat onl\-, plug in or out cajjacity bj- ,01 inf at a time, and get the best effect with the rheostat. If this is not efficacious, increase or diminish the shunt by 1,000 ohms, and vary the rheostat and condenser as before. On cables over 300 miles in length further adjustments are ver\- often recjuired, when the recorder or mirror is the instrument u.sed, and are shew-n in I"'ig. I 16, viz., (3) a small .set of resistance coils ''one amounting to 100 ohms in the aggregate is sufficient) is inserted between the first line terminal of the artificial line antl the terminal marked A I, of the bridge. On cables over 300 miles in length it is not recommended to leave the bridge in circuit permanently, but only to employ it to facilitate the preliminary balancing of the cable, two sets of condensers being .substituted for the two arms of the bridge, as in Fig. 116, and exj)Iained below. Other adjustments are sometimes found necessary to perfect the balance on long circuits, the principal of which are the following: — ;'4) and (5) Two .sets of resistance coils, of higher resistance than the last (3), inserted respectively between the first and second capacity terminals of the artificial cable and the earth ; [ 7'o fare f. 652. Dll'I.lA TKi.li.KAI'in. 653 (6) one or more- IcaUa^jc circuits, coils of wire of from 5,000 to 100,000 oliins rcsistaticc, inserted between certain of the line terminals at the far end of the artificial cable and the earth. I""i^f. i 16 shews all these adjustments in position, hut it is seldom that more than four of them are reciuired. The balances at I'en/.ance station of the Western Union Telc^^raph Company, Lisbon and I'ernambuco stations of the Brazilian Submarine I'elef^naph ('omi)any, are ^iven below as t)picai cases : — I'ENZANCK, ('ORNWALI.. S| = 80 microfarads. 1 R| = 25 ohms. Sa=8o „ j Ra=30 „ Si' = 8o ,, I Ra= 100,000 ohms on uiiitli box. S,= 4.402 ,, R,,^ 22,000 on first five boxes. §4 = . 504 „ I Lisbon (No. 2 LisnoN-MAni,ii I R, = 640 ohms. 84=^4.67 „ j Rh=is „ R, = 18.8 ohms. I R,i,= 3,200 „ between nineteenth and Rj = 600 ,. I twentieth box. Duplex Directions for Long Circuits. — In all cases of ionj4 cables the readiest method of obtainin<4 balance will be found to be as follows: — Startin^f with the adjustable condenser s., and the whole of the shunt box Kr, to the first four boxes in circuit, keeping the knob of the rheostat in one hand, send a rather rapid succession of " ckjts " by means of the key, and turn the knob backwards and forwards until the best balance procurable is obtained. If a .satisfactory result is n(jt so obtainerl, insert .05 mf in s.,, increase or diminish it b\- .01 or .03 mf at a time, after each alteration obtaining the best balance possible by means of the rheostat. Notice, of course, whether such alteration of the condenser improves matters or the reverse, and <^n on in the direction of improvement till the most suitable capacity is found. Should the last adjustment not be effectual, alter the resistance of the shunt by 5,000 or io,ooo ohms, and repeat the adjustment with the subdi\ ided conden.ser and tlvj rhef)stat as before. When getting the balance near, alter the .shunt by smaller amounts, 2 \' 654 sriniAKiM'. Tia.i'.cKAriis. say l,ooo;it ;i time. Should there still remain a "JHr"()f the mirror, or blurred line on the recorder slip, while sii^nialHnL; on one ke\-, which is unaffected by any variation of the condenser s. and the shunt K., then insert the resistance box R., between the first capacity or earth terminal of the first box of the artificial line and the earth. If on sendinLj; reversals a sharp wave is produced, which cannot be eliminated b\- means of any of these adjustments, a leakage circuit k., w ill ha\e to be ap|>lied at some point of the far end of the artificial line, the position to be found by trials. The conden.ser s., can be dispen.sed with in a t^^reat many cases by inserting- resistance R,, between the beginning of the artificial line and the bridije Sometimes on very lon^r cables another set of resistance R^ is required, either alone or in conjunction with R,„ jjlaced witiiin the second earth or capacity terminal of the artificial cable and the earth, in order to eliminate the "jar." I'Vom da)' to day it will be found necessar}- to alter the shunt R., or resistances Rj and Rx, accordinj^ to the variation of temperature of the artificial line and the underj^round or land line lead to the cable. On lon^r cables, after obtainin<.j the nearest balance by means of the bridi^e and the \arious adjustments above described, the condenser s., is remoxed, and two sets of condensers s'.^ and s"„ are inserted in place of the arms of the bridge, one between the terminal a of the rheostat and c, and the other between the terminal /' and A i,. To adjust these two .sets of condensers, it is necessary to have a finely subdivided condenser s^ in connection with s".„ and the mode of proceeding in order to re-establish the balance is the same as above described, the conden.ser s^ taking the place of the condenser s.,. The subdixided ccjndenser s^ is, of course, in parallel with s".„ thereby increasing the total capacity (to the value of S^) by increasing the area of the plates to that extent. The best mode of proceeding to correct for slight variations in the balance is as follows: — First get nearest result by means of the rheostat and condenser .s^ while sending rapidly on one key. if then, on sending reversals, a sharp wave or jar is produced, alter the resistance R,, or the shunt s., if used, and get nearest result by means of the subdivided con- denser s^, with the a.ssistance of the rheostat. Proceed thus in the direction of improvement. Should there be a sharp return wave, or flick, after doing all that can be done by means of these adjustments, then the resistances between the first and second earth terminals and the earth will have to be altered, and perhaps the position of the "leak." When the line is made up of a mixture of land wires on poles, and underground or submarine cable, the "balancing" becomes more com- plicated. On a mixed line of cable ^submarine or subterranean) and land wire, in tho.se cases where they are to be worked together as one circuit Di'i'i.Kx ti;i.i:{;kai'Iiv. 655 cluplexint:^ is rather a troublesome matter, and special arrangements require to be made. Tims, when the cable is at the distant portion of the circuit, its dischartter gentlemen, till tjuite recently. What the actual point of superiority is in Muirhead's artificial cable over that of Varley — as adopted by Stearns — cannot, of course, be said with any certainty. It would, however, appear, at the outset, to be a more faithful imitation ; for in a cable it is not a ca.se of alternate resistance and * Just as Stearns' method (of Varley "s artificial and diflfcrcntial principle) is invari- ahly adopted for overhead land Hne duplex work. It is obviously better here, where the capacity to be inserted in the artificial line is a variable and, at the most, an infinitely low value as compared with the resistance recpiircd. There being so little capacity, comparatively speaking, the advantages of Muirliead's "inductive resistance" does not apply in this case. The capacity of an aerial line is roughly about one micro- farad for every too miles, under ordinary circumstances and in average instances. 656 sri'.MARIM': 'rKI-KCRAIMlS. capacity, but of the two combined throughout the length of the conckictor. One thing is clear, and this is that, in practice, Muirhead's method enables a balance to be more readil)- obtained — and, what is more to the point, more assuredly maintained — that is to say, as far as concerns a submarine, or subterranean, line, possessing material caphcit)' as well as resistance. It would be both interesting and instructive to compare the effect of balancing the same cable by the two methods. It is believed, however, that this has never been done. The greater difficulty of establishing a permanently complete balance on the Stearns .system certainly tends to affect the speed of working, for with an imperfect balance the signalling speed has to be kejjt within certain limits, owing to the disturbing influence on the received signals thereby incurrcl. The trouble experienced in setting up and maintaining an ab.solutely complete balance in Stearns' method by an ordinary Varley artificial line is partly due, very probably, to the large number of contact jjieces at each junction of ca|jacity and resistance,* which naturally tend to be a source of leakage and variability .seriouslj- affecting the prospects of a comjilete and permanent balance where such sensitive instruments are in question as those used for ocean telegraphy.+ Other Methods. — Besides the Stearns and Muirhead .sy.stems of duplex telegrajjli}' as apj^lied to cables, there are .several other forms of the differential and bridge methods, employing either Varley's artificial cable or the Taylor-Muirheaci artificial. Instances of the.se are the .s)stems of Harwood, Benjamin Smith, and Jacob in this country ; and of M. Ailhaud in France. Mr Benjamin Smith's method of duplexing (devi.sed in 1876^ makes use of the Wheatstone bridge princi|)le, and employs a Varley artificial cable for the compen.sating circuit. The no\el feature of this plan consists in the insertion of a high resistance in front of, and in series with, the cable. Mr Smith, in the course of his experience in the attemi)ted du|)lexing of * Though, theoretically speaking — as already stated — the greater the miinber of sub- divisions the nearer the approach to the true imitation of a cable in wliicli each section (of minimum dimensions) constitutes both resistance and capacity. + In the same way, a cable with a fault in it will not work duplex 'thouj^h, unless a \eiy bad fault, it works better siniplexi on ac<:ount of the balance being thereby upset. Faults b'Mng practically always variable, cannot be efficiently alloweil for in the adjust- rnents--that is to say, if the defect form an important item in the prevailing conditions. It may be mentioned incidentally that a fault beins close to the sending end of a simplex circuit is, as a rule, a fa\()ural)lc condition, unless it be so close that the battery jjower has to be kept very low in order to avoid breaking down the fault. Diri.r.X TKI.I-.CRAI'IIV. 657 cables with \aryin[^ types of conductors and varyiiiij tliickncsses for the dielectric, conceived the idea that by so inserting a hi^^h resistance he would render his cable more easy to balance on account of the extra retardation thercb)- introduced. This would have the effect of causing the current charges to be materially slower : or rather, to put it more accuratel)', it would thereby take a Ioniser time for any upsettini; of an absolute balance to affect the sii^nals— so much so that the period mitjht be avoided altogether ; and, moreover, when such a change did take i)Iace, it would not be so serious. In Harwcjod's method (as dexised in 1879 on the bridge principle with Cable V r-<, -tv V/ V^ AL r m k ^ (^ Fk;. 119. — Ilarwood's Duplex. Muirhead's "artificial" line) the battery I', Fig. 119, is in the bridge which iisualh' contains the receiving instrument c. ; and reciprocal 1)', condensers of about equal ca|)acity to those usually inserted in the line for simplex- working, are placed in the proportional arms. It may be remarked, how- ever, that where the transmitting key is jjlaced in the bridge instead of at the a])e\ (or fork) of the proportional arms — in fact, when the sending key and receiving instrument are reversed in their positi(jns as above — it is usuall\- thought advisable to insert a condenser in the bridge along with the ke>-. A Muirhead artificial line a 1., su|jplemented h\- an e.xtra adjustable resist- ance,* forms the third arm of the bridge, the cable being the fourth arm. This plan gives good results on lines of medium length. It has been in u.se on the cable from Porthcurno to Lisbon, the length of which is 850 miles, the copper resistance 8,050 ohms, and the capacit)- about 250 micro- * This supplementary resistance forms one of the extra means of balance adjustment, and (as may be seen from the various recent diagrams) is common to all modern methods in practice for duplexing, at any rate, short Icngtiis. . .. ^ - 658 Si:i!MAKIM-; TKI.KCkAI'lIS. farads. The artificial line used in duijlexing this cable is cnclnjed, at Porthcurno, in nine boxes, its resistance being 5,819 ohms, and its cajjacity 192 microfarads. The supplementar)- resistance at the end of the artificial line is of 3,000 ohms, and the condensers in the comparison arms of the bridt^e ha\c each a capacity of about 40 microfarads. The sending battery is composed often Minotto cells, and the vvorkini; speed is about 140 letters jjer minute each \va\-. It will be obvious from a studj' of the connections that in this method it is most important that the battery be efficiently insulated.* This in itself is a |)oint a.^ainst its adoption under certain circumstances. It is, moreover, rendered somewhat imjjerfect owini; to the extra retardation it introduces.^ Nevertheless, it is well adapted — indeed, rather convenient — for cables that are worked at a speed far below their working- capacity, where, therefore, the extra retardation involved is of no consecjuence. The balance beinij less sensitixe, is less trouble to maintain. Ailhaud's method of duplex ma)- be looked upon as a combination of the differential and VVhcatstone bridj^e .systems. It differs from the preced- ing methods in not requiring' an artificial line — that is to .say, a line pos.sess- in^ simultaneously both resistance and capacitj- — the fourth arm of the bridge being formed of a simple rheostat. This method has been adopted for duplexing the Marseilles- Algiers 1879 and 1880 cables, and other French Gcnernment lines, with complete success. An advantage claimed for it is the high degree of variation as regards scojje and nature of adjustment. Comparison of Varley and Muirhead Artificial Lines. — However, so far as English practice is concerned in the |)resent da)-, almost all of tho.se of our submarine cables which are du|jlexed employ the Wheat- stone bridge jirinciple with the Muirhead-Ta\'lor form of artificial lii.e for the com))ensating circuit — constituting, in fact, what is conimoiil)' known as Muirhead's method. In most instances the duplexing of these cables have been carried out, or su()erintended, by Dr Muirhead himself Nevertheless, there arc those, even now, who argue that the Varlej- * Whatever is in tlie bridj,'e must be thoroughly uell insulated — in fact, its two ends must be ctiui potential. A liattery naturally rccjuircs more care to insulate than an instrument of any sort. + By llaruood's arrangement there is retardation just near the battery, at the .sr/n/i/tx' end (thn)uj;h the compensating circuit) instead of at the receiving end. This has the effect of rendering it an insensitive method by, as it were, reducing the strength of the current at the outset. Harwood's plan is, on the other hand, one which necessarily implies easy balancing. It is, however, suited for certain cases only- cliietly those of short circuits. DLi'LKX •n;i.i;(;K.\i'ii\-. 659 artificial line is preferable for balancini; inirposcs* on account of the greater scojjc for nice adjustment, both as reijards resistance and capacit)-, consti- tuted by these alternations of separate resistance and capacit)-, which can thus each be dealt with separately — under any special change of condi- tions, for in.stance.+ There is no doubt that vast improvements ha\e been made in the practical application of the Varley "artificial" to cable-duplex work. Thus, during the last five years the Silvertown Com|)any have success- fully du))le.\ed a number of cables — for the Western and Brazilian Corn- pan}-, for the Central and South American Compan)', and for others — on the VVheatstone bridge principle, but employing (like Mr Benjamin Smith) the Varley artificial line for compensation. Previously — in 1888 — Messrs Siemens Brothers liad du|)lexed the Pou)'er-Ouertier Atlantic cable by Jacob's method of that year, using a \'^'u■ley artificial line. Messrs Siemens have also applied duplex apparatus to some of the shorter (multiple-core) sections of the " Commercial " and other Atlantic cables b\' means of Jacob's system of midtiplex telegraphy with multiple-core cables. This system (jjatented 1882) consists, in fact, of balancing one insulated conductor against the other ; thus, where a multiple cable is in tjuestion, obviating the use of any special compensating apparatus. It is also considered by some that the Varley " artificial " is preferable to Muirhead's for submarine cable duplex work (as well as for land-line du|)le.\) on the score of the indejjendence of the resistance and cajjacity components for the fcjllovving reason. It is stated that the tinfoil in the combined inductive resistance is verj- much influenced as regards the resist- ance factor by changes of temperature such as maj- be made in the var}ing and various climates that the apparatus may be installed in. This feature * On tlie other hand, the leadinj.; up resistance Ri (Fig^. 116) in tlie connections of a Miiirhead artificial line tends to l)alance any self-induction in a cable. Tlie coils in a Varley " artificial " being necessarily wound non-inductively, this is not so here. In a coiled cable the self-induction is considerable, of course ; Ijut even in tlie linear conductor of a cable, seme self-induction is involved. t In point of fact, the main difficulty to be met with in the practice of duplexing cables lies in the insulation of the condensers, which is liable to vary — and, indeed, under some circumstances, to gradually fail altogether — owing, for instance, to climatic condi- tions. This state of things t'.,iy be brought about by any chemical changr in the wax of the paraffined paper, causing it to gradually decompose, thus altering its specific nualities as regards insulation and inductive resistance. A fall in insulation from 800 megohms to 150 megohms (per N.M.) has been known to occur by a rise of temperature from 65' to 75 V. only, the inductive capacity being at the same time materially increased. Actual mechanical shrinkage of the dielectric is another source of trouble which rec|uires to be guarded against with reference to the condensers. It will be readily understood that any change in the value of the condensers (and thus of the compensating circuit) thus brought about has the effect of entirely upsetting the balance. 66o S U H M A R 1 N I', T K L I-X; K A I' H S. requires, therefore, to be carefully guarded a^^ainst or compensated for, in order to maintain an efficient balance ; whereas in the Varley " artificial," the resistance being provided for separately, can be made up frf)m a material — like German silver, i)r any similar alloy — which has a very low temjiera- ture coefficient, electrically speaking. On the other hand, it must be remembered that the tinfoil of Muirhead's" artificial " is buried in a mass, and that even supposing it is so affected the appat;^tus is rendered com- plete by a rheostat for final adjustment according to surrounding conditions at any given moment. Be this as it may, the objection raised does not appear to apply in practice, as there is no actual evidence of inefficiency due to the above cause. SiMILK.S. Various similes have been given to bring home the principles of dujjlex v/\/\AA/\/N/\ AAAr 1 Fin. 1 20. telegraphy. Perhaps the best is that of the " tug of war," bj- which, if equal forces arc applied in opposite directions, no result ensues. In the case of -(- 4- + ifi^fJii^iMil.Ji'^^J^Af. Fic. 121 the connections in Harwood's bridge method, the bridle simile has been apti)- u.sed on the same basis. This is suggested by Figs. 120 and 121. DUri.KX TKi,i:(;i<.\i'iiv. G6i OUADRUPLEX KXPERIMKNTS. In 1878 Ur Alexander Muirhead, in collaboration with Messrs J. A. Bri,i;j^s and G. K. Winter, conducted a scries of experiments* in the direc- tion (jf the application of qnadruplex telegraphy to submarine cable work- ing.+ The results attained were not, however, of a sufficiently satisfac- tory nature to warrsrit the system being adopted practically in the few cases where it would be of special value.* Moreover, as long as the signalling instruments for working long submarine cables are of so deli- cate a character as the recorder — influenced by cliahges of current — there does not seem much prosi)ect of quadrupiex telegraphy being ap- plicable here on any extensive scale. On very short cables, land-line " quadrupiex " may be applied, the difficulties increasing gradually with increase of capacity and consequent increase of retardation. It may be further added that attempts ha\e been made experimentally even to instal " sextuplex " and " octuplex " telegraphy on submarine cable circuits — i.e., by which three or four messages might be simultaneously transmitted in both directions through the same conductor. These, of course, met with .still less success. * On the basis of their patent, No. 4,590 of that year. t The term "quadrupiex" is j(iven to those arrangements which enable two signals to be sent in one direction and two others in the opposite direction at the same instant of time. Quadrupiex telegraphy is, in fact, constituted by the combination of duplex tele- grapliy with what is known as " diplex '' (or "biplcx") telegraphy, which latter consists of the simultaneous sending of two signals in the same direction : this is generally dependent on the use of two relays of such a nature (/>., one " polarised," the other unpolarised) that one works solely under the influence of currents of given strength and varying direc- tion, whilst the other is alone acted on by currents of varying strenf.th, but in one direction only, the same compensating arrangements being effective as those em|)loyed in ordinary duplex telegraphy. Diplex telegraphy, indeed, is set up oy two messages being sent through a cable in the same direction simultaneously, and when this cable is also duplexed, quadrupiex telegraphy is then established. Van Rysselberghe's anti-induction system is an instance of this ; as well as, more recently, the phonoporc of Mr Langdon- Davies alluded to towards the end of this book, and the plan of M. Picard. \ It is found that on short cables with a heavy trafific, such as those between this country and the Continent, the Wheatstone automatic with Wheatstone repeater (Morse system) get through the work with all the recjuired expedition. CHAPTER IV. AUTOMATIC MACHINE TRANSMISSION. Gencr.ll Remarks — Hclz-Hr.ihic System —T.iylor's Automatic Transmitter — Dclany's System — Taylor and Dearlove's Automatic Curb Transmitter — Wilmot's Transmitter: Cuttriss' : Muirhead's Curb Transmitter: Muirhead and Saunders's Curb Trans- mitter: Trice's Electrical Contact Apparatus for Transmitters — Advantaj,'es of iMechanical Transmissions — Application to Long Cables for Hij^h Speed Workinji. Thf; problem of how to increase the workinjj and earnini^ capacity of a jjiven submarine cable came to be considered principally in connection with trans-.-Xtlantic telej^raphy owin' 0' m', mounted on the .same pivot, haviiif.^ to do with the needles at one end, and with two screw stops insulated from each other at the other end. Two s|)ecial sprinj^s '/'> '/ ''< f<-'"<' to keep the bent levers constantly pressinj^ against the screw stops. These springs are attached to the lower ends of the levers it t, it'v', .so that their tension can be rej^ulated by means of a screw / acting on the upper ends of the levers. The whole of the mechanism is of very solid construction, and capable of working for months without being touched. The apparatus being merely required to send dots, the jjerforator (Fig. 133) was sim]jlified. It has three punches only, one for the ])ositive current imjnil.ses corresponding to dots, the second for the negative currents giving the dashes of the Morse al))habet, and the third for drawing the strip of paper along. Fig. 124 gives an elevation and plan of the punching apparatus as it appears with its cover on. Fig. 122 (opposite) shews in plan the connections of the Froment rclaj' arranged as a current reverser. The positive pole of a local battery is joined up to the framework of the automatic transmiiter, the current being admitted — by the make-and-break motion of the apparatus- — to one pair of relay coils, or to the other as required. The two coils of * So beautifully perfected in detail by the mechanical genius and skill of Mr Augustus Slroh, this instrument is sometimes worked (simplex) at a rate of 600 words per minute on the Press circuits where it is used. In ordinary practice, however, the speed is more often about half the above. It is found that when a certain rate is exceeded, it becomes impossible for the clerical staff to deal with the slip as it positively pours out. Moreover, very often, the delays due to repetitions are so much greater at the higher speeds, that a inore moderate rate gets through the work quicker in the end. This being so — fascinating as the 1,000 words a minute pointed to by inventors may be — in practice it is rather a wild notion at i)resent. In view of various undertakings and prophecies, these remarks apply to " uj) to date" and future cable telegraphy as much as to inland telegraph systems, so long as the present general methods are in use. t The late Mr Robert Sabine is said to have experimented with the Wheatstone transmitter for working the cable between Calais and Fano (Denmark) at quite an early date. 664 srnMAKiM'; tki.kckai'Iis, L'iich pair are joined up in parallel to lessen the resistance of CJich circuit. One |)ole of the line battery is coiniected up to the two upper screw stops and the other pole to the two lower stops between which the niox iii'-|es between Marseilles and Algiers. The details of installation at a station at one e.\tremit\' of the line are shewn in l'\<^. 135 (see Plate XXXIII., overleaf), and ma}- be taUen as a fair sample of a short cable recorder duplex .system with automatic trans- mission. Here, ^^oin^^ from right to left, we find: — The resistance R situated immediately before the cable. The recorder with coil differentially wound. The train of clockwork for unwinding the .strij) of paper. Vu). 124. — riiiichini; Apparatus : Elovatum and I'lan. The proportional arms of the bridge. Tlie .'Cnding conden.ser A. The conden.ser I!, with the adjustable set of resistances for controlling', it. The set of resistances /i, forming the third arm of the bridge. The conden.ser (' and the set of resistances y. The condenser D and the set of resistances S. A two-lever key for hand .sending when the automatic transmitter is not in use. Two four-way commutators for changing over from one key to the other. A second double-lever key, termed the duplex key, to be used in case of need, for hand sending. The automatic transmitter. T-astly, the reversing relay as already described. 666 SUBMAKINK TKLKCU-iAI'IIS. The wheel of the mechanical transmitter which impels the ]3aper stri|) works regularly at the rate of thirty turns per minute. This wheel having twenty teeth, one turn gives twenty current impulses or spaces ; now twenty impulses go to one average French word of five letters, including the sjjaces between letters and words. The working speed over the Algiers cables, under these conditions, averages therefore thirty words per miiuue, oi i,., whether or no a large, and correspondingly costly, core is warranted by the estimated traffic recei|)ts.* The service is carried on at each station and on each cable bj- four or five punching clerks and one key clerk who inserts the perforated strips in the transmitter and cuts off in lengths the strip arriving, whicli he passes on to the writers. Taylor's Automatic Cable Transmitter. — .After MM. Bclz and Brahic, Mr Herbert Taylor, M.lnst.C.K., was one of the earliest workers in this direction. In 1888 1 he designed for the Anglo-American Telegraph Company an automatic transmitter, which was very success|fully worked. Since then he has given further attention to the subject, and has perfected an instrument, a description of which follows. This later form of automatic transmitter, designed and patented by Mr Taylor, has distinct and important improvements to which reference will be made, as may be gathered from a study anrl short explanation of Fig. 126 (Plate XXXIV.). * In ordinary manual transmission, however, probably no operative clerk could send for any length of time, if at all, even at this (thirty word) rale- much less at fifty words (=about 750 current impulses) a minute, which is the speed attained, with the auloinalic transmitter, on the latest Atlantic cable, whose core was purposely designeil to permit of such work being rendered practicable. + At the end of this same year, Mr Julius i'imm, of the (ireat N'orlhern 'lelcgraph Company, patented a modification (see specification 18,966"") of W'lieatslonc's transmitter suitable for working cables. This was first used on the Ilongkong-.Sh.inghai section of the above system in 1889, antl was fully described in the rc/i\i^r/iic Journal and Electrical Review the following year. • ' , ' [I'LATK XXXU U c ■J '3 S 3 2 [ Tofaa p. C66. [Plate XXXIV. r [To face p. 666 (after Plate \XXni.\ AUTOMATIC MACIIINK TRANSMISSION. 667 As in the case of the Jkl/.-lirahic apparatus, this instrument is of the Wheatstone type, but adapted to transmit the cable code of signals. The two lexers ;// and // ma>- be regarded as representing the two spring blades of the usual hand-.sending key. In this instrument the two levers are controlled in their movements by two needles, and the inovements of the needles are in turn governed by a paper tape which is ])unched in accordance with the message to be transmitted. The cams l\ b' control respectively the motion of the contact levers w, li. One of these cams at the proper time allows cither contact lever to move, and thus to put line and battery in connection ; the other cam, at a regulated period after this operation, connects the line with earth or its equivalent. These two cams l\ b' act through a bell crank lever r, and they are fi.xcd ui)on an axis which is rotated continuously by the clockwork ; moreover, as constructed they are adjustable relatively to each other. V>y this combination the comparative duration of the battery and earth contact with line, to produce a given signal, ma)' be adjusted, until the most suitable arrangement is found for the working of the circuit in connection with the instrument. In some degree this regulation is of the nature of a "curb," as by diminishing or increasing the period of the earth contact with line relative to that of the battery contact with line, so is the curbing effect on the signal diminished or increa.sed. The adjustments and the action of the transmitter are simple, and the speed of working is only limited by the electrical constants of the line. The speed obtained with this form of " auto " when sending I'ress messages on the 1894 "Anglo" cable was as high as fifty five-letter words per minute. The connections and circuit need no explanation, being clearK- shewn in the figure. The Delany Automatic System. — Mr Patrick B. Delany, whose name is well known in connection with a method of synchronous multiplex telegraphy — adopted b}' the Post Office — for land lines, has of late j'cars devoted his energies almost exclusively to ocean cable telegraph)'. This has given eminently satisfactory results in the course of trials on Atlantic cables subsequent to its invention in 1893.* The principal features of the system are an electro-magnetic perforating machine and a new wa)' of making contact through the perforated tape. * See English patent specifications Nos. 21,630 and 23,687 of that year. 668 S U 1! M A R I N 1", T I'. I . VX \ R A 1 ' 1 1 S. The perforator (Fi^. 127) comprises a key having three h"ght levers similar to the lijrhtest form of cable keys. The buttons of these levers are grouped in clover form — dot, space, and dash. An electro-magnet c operates the ilot punch, another I! the dash punch,* and a third A the simple, but \-ury effective, mechanism for spacint^ — performing; the function of the space key in the ordinar\- Wheat- stone puncher, but, if anything;, more accuratel)-, and without makint; a centre row of holes. The only holes in the tape are, in fact, for the si72 SUKMAKINK TIM.I'CKAl'l IS. The connections of these rel.iys arc made in such a manner that one relay K, receives, and is actuated by, the currents which sij^niai " daslies," and the relay K.^ receives, and is actuated by, the currents which si^nial "dots." The curbing currents bj' reason of the jMJsition of the relays have no effect upon them, except to pull the tongues over harder on to what is called the "dead stop"; neither does the dischar^^^e from the cable pass through the coils of either relay. In the local circuit of these rela\-s is the "Herring," which records the outgoing signals, and unless the signal actually passes to line no record is possible; the avoidance of errors and the effectiveness of the " check " is by the.se arrangements greatly increased. The three cams controlling the movements of the needles, contact levers, and curb in Taylor's and Taylor and Dearlove's transmitters are shewn in I*'ig. 131 (as well as in Fig. 126), l\ b\ and /. The clockwork is stopped by moving a lever, which, at the .same time, by a switching arrangement, transfers line and earth to a hand-key for calls, corrections, etc., as is necessary or desirable. The compactness and the actual working of this latter instrument is remarkably good. .A considerable increase in the s|jeed of transmission is obtained under ordinary circumstances, but especially is this noticeable when it is used upon long circuits with a high " KR." The slips (as referred to above) and the conditions under which they were obtained are given on the folding sheet opposite. The.se specimens of signals obtained under the varying conditions here noted prove, beyond all doubt, the effectiveness and free range of the curbing apparatus provided in this automatic transmitter of Messrs Ta\lor and Dearlove. For instance, in s!i|) i no sending condensers are used, but the curb is adjusted suitably. Here the definition and uniformit)- of the signals are perfect, nor is this result to be obtained by other means, such as a variation of the battery or condenser power. Other Transmitters. — lk\sides the automatic transmitting instruments and systems which we have here described, there are also several others which, it is believed, have similarly proved highly satisfactory. Vox instance, Mr T. J. Wilmot in 1890 bnnight out an automatic instrument, being — like the Helz-Brahic, the early Taylor "automatic," and others— a neat modification of Wheatstone's adapted to recorder, for cable work, instead of Morse signals, by alterations in the form of the levers. Then there is the transmitter of Mr Charles Cuttriss (electrician to the Commercial Cable Company in New York), the great feature of which is that the prepared transmitting paper takes indentations instead of holes from the punching [I'LATli XXXV. r V, , . V- r (2) I?' i? (2@ (J)® ^ 6.6 6 Flc. 131. — Taylor and Dearlovo's Automatic Curl) Transmitter. [Tofa>c p. 672. Plate XXXVI.] A'.i?.— These signals were obtained on ;i line of 7,oc» ohms and 330 mfds. or KR = 2.31 x 10". V v.; u~\J ■-' v/ v^ {_..■ \.,., V. — /'x/ V.' •■■■ •■■■^- ■■■■ a ■\ ,. .. ' ^ •"! ."l ' \ \r-"\y-y vw -' ■■■■■•-'■■ 1 /v. V vA .'^,_ ./"* — '•- L — /■/\ .-.. A ..••■•••'\ r-v... .../•\..^-.../^--\ \ ,,... ■■ ■^.^v.''"^ •■ ■•■ '•-••^ .... •' 6 •••--•■\,.-...y" '■>../\./----..y \ .••■■• \ ..' ••.. ■.— y Fig. 132.— SuiNAUi obtained through an Artikiciai, Link under var) Transmitting Apparatu Particulars. Slip I. A'i' .vtv;///«^ condensers ; receiving condensers = 70 mfds, „ 2. Sending condensers, 70 mfds. ; receiving, 60 mfds. „ 3- ,, 4- ,, 5- „ 6. .. 7. 70 70 70 70 70 60 60 60 60 60 Curb adjusted unti Small curbing curr Increased curbing Increased largely t Curbing current in Field of recorder 1 curb current insi A/'o curb (with Tay d 330 mfds. or KR = 2.31 x io«. Six I.pclanche cells. Speed, twenty-eight, five-letter, words per mini ■A r-y"' \.. r'\ /■'-'■■\ A r-"\ n / L'" 1-' '\-sj'\/ '\ — ../■" v---' 'V ■•-•■ ^- V \ /\/ \ / A /X ,...-M A •■■■ ^^- \./ V-' 'VA...../-X/ .... A ...-•■'^ r-v.. ... . ■■■'"■■ r\ r\ ...y\ r-.y---... ■■■ V ■■■■■■-■S AA A""'A A-\ -•■'■•••■ VA ...."L-'^^ ,.■■., .■-•■■'\ .A.., A ■•^•- ^.-y A......' V •(^ .,' \y\ .^._ .'". ...•■' ' '•....•■\ ■■•. .■■■\ ..■'••, ,••••■ "••, / '•.-. ,■•■■■■•. ■■■■'"■\ .• .A, \..-- ./■ ^ r{ .-. y N Artificial Line undkr varying conditions, with Taylor anu Dearlove's Transmitting Apparatus. Remark.s. * i = 70 mfds. Tifds. Curb adjusted until signals proper shape and definition .Small curbing current applied. Increased curbing current applied. Increased largely the curbing current. Curbing current increased until signals appeared reversed. Field of recorder reversed, giving signals in usual position, but produced by the curb current instead of with the signalling current. No curd (with Taylor's piaiti "(ftt/o"), ^ battery and i earth. Plat {•/ AUTOMATIC MACIIIXK TRAXSMISSION. 6/3 apparatus. Both of these mechanical transmitters have been, and are, lar^^ely used on the Commercial Company's cables.* Wilniot's Automatic Transmitter. In 1893 Dr Alexander Muirhead and Mr H. A. C. Saunders joined hands over another curb transmitter (in the form of an automatic key) Flc. 134. — The Cultriss Transmitter. worked on a somewhat different principle, but this apparatus recjuires extremely regular transmission of a special kind, and there is .some difficulty in ensuring this. • * Mr VVilniot, the abov e company's superintendent at Waterville, was one of the very Inst workers in the field of automatic tclet,Maphy. His appaiatns was soon rccoj^iiiscd as l)einn a suciessfiil solution to its application for cables. The Wilniot transmitter is not furnished with any curbing device, the inventor beinj^- one of those who consider that by iisin^' condensers all the rcciuired curbing effect is afforded. A j,'cneral view of this instru- ment is given in Fig. 133, and the like representation of that of Mr Cuttriss in Fig. 134. 674 SriiMARINK TKI.l.llKAI'HS. Again, in 1894, Dr Miiirhead devised an intjcnious automatic sender which also includes arrangements for curbing each signalling current. A great feature in this instrument (already largely used by the " Eastern " and allied companies) is that it jierfectly ensures the attainment of a correct relation f(jr the length of battery and length of earth contacts. It al.so affords means of altering the duration of contacts without stopping the apparatus, according to varying conditions of the line. This device is, in fact, very different in principle from the Wheatstone transmitter, and is. therefore, unlike some of the other cable automatics in this respect. It is said to increa.se the working s]jeed of a cable by as much as 40 per cent. In 1892 Mr W. A. Price invented an altogether novel method of effecting electrical contacts especially applicable to automatic transmitters for working cables. This was intended to meet the difficulties experienced in the proper contact making and breaking through tlie punched holes of the sli[j of the various modifications of Wheatstone's transmitting instrument. In his patented invention, Mr Price proposed to ensure good electrical contact b\- means of .streams and jets of mercury from an Archimedean screw ai)])aratus in connection with an Archimedean pumjj. Unfortunately space would not permit of all these being described in detail. A sufficient idea of some of them has, however, been presented to the reader. In all of these, as in Wheatstone's transmitter, clockwork is employed for drawing off the paper, in the usual way, adjustable to almost an\' desired speed. The point of novelt)' in each, as ajjart from Wheat- stone's apparatus for land-line circuits, is (i) the various more certain methods of ensuring a sufficiently good electrical contact where a high retardation figure is involved as is the ca.se in long submaiine cables ; and in some in.stances (2) the application of curbing arrangements as suitable for long cables of high retardation. Advantages of Automatic Working.— From the introductory and subsequent remarks it will be seen that the advantages of machine (automatic) transmission over ordinary manual transmission may be summed U]) as follows : — I. Hi.jher signalling speed, here limited only by the dimensions of the core.* -'. Greater uniformity or regularit)-, by obviating varying, or bad, * Very few operators can keep up a speed of cable transmission much over 120 letters per minute-— ;>., 20 words — for any lenj{th of time, though even 35 words per minute can be worked up to at a stretch for a verv short time. With automatic sending;, however, the speed is only limited (i) by what the dimensions of the core will permit of for readable signals ; and (2) Ijy what the receiving instrument will take. This, with the siphon recorder as at present used, is at least 100 words jier minute. Thus, an increase AUTOMATIC MACIIIXK TRANSMISSION. 675 clcrk-sciit signals. 3. Improved definition with a |;ivcn speed. 4. Smaller number of errtjrs. Its Application in Practice. — The application of automatic transmission has been, however, so far almost cntirel)' confined to long ocean cables, such as those across the Atlantic, to some of the longer and busier sections of the "Eastern" Company, and by "through working" to the "Great Northern " Company's European .system, liut the French Government Telegraphs were, it is believed, the first to make use of the earliest cable automatic — that of Belz and Brahic — and to apply it to their Marseilles- Algiers cables. In .some special cases automatic transmission has been, anrl is, emijloycd on short cables ; but, as a rule, it is not — onl)- for want of sufficient traffic to warrant its necessity. In .\tlantic cables, automatic working has become imperative, and is almost exclusively adopted, in order to keep pace with the continuall)' increasing traffic without adding to the facilities of the .system by further duijlications. In short cables, however, duplications are less c terminus— owing to the current being at the outset subjected to inductuw influences as above. Some interesting experiments in /cwj/'-distance telegraphy on the Morse system, as regards land lines, were carried out last year in Australia. In the course of these, the longest stretch of line was spoken over that has ever been known to be — />., 7,314 miles, almost entirely round the Australian Continent, from Cape York, Queensland, to Derby, Western Australia. This was effected by ineans of automatic repeaters. There were no less than fifteen intermediate stations, all several hundred miles apart. When, therefore, it is taken into consideration the number of armatures that had to be attracted and relea.sed on the makc-and-brcak of each signal, together with the many local circuits in operation, the results of these experiments ma\' be said to have been eminently satisfactory. Muirhead's Universal Transmitter. — A simple automatic transmitter has lately been designed by Dr Muirhead, which can be used equally well * Indeed, in the opinion of many, a universal .Morse system — i.e., cables joined direct to Morse-worked land lines — would render the work slower than by retransmission. ,1 -^ 678 SUmiARlM'. TKI.l'.CKAI'IIS. for Morse or recorder working. The perforated jjapcr is passed throii^di the transmitter (illustrated by Figs. 135 and 136) in the same way as in the well-known Wheatstone instrument. In this case, however, it is not essential to use a spur wheel for drawing the paper through ; nor is it necessary to perforate the centre holes in the oiled paper, though preferably done in order to guide the paper should there be any irregularity in the line of perforations. For Morse working a special perforator is employed. The dots are punched square by means of the left-hand lever, the paper being moved on -^^ inch : the dashes are punched with the right-hand lever, making an oblong hole, and the paper UKJved on ,-^7 inch. Two le\-ers A, A are placed Fig 135. — Muirhead"sAuloinatic( Universal) Transmitter, for Morse or Recortler Wurkinj;. (Front \"ie\v. ) •11:. 136. — Muirliuuirs Universal Transmitter. (Enil \icw. laterally, having nose-shaped ends trailing against the paper: one or other of them falls into the holes made in the paper as it passes through the transmitter, and makes a short or long contact as the case may be. This contact is made with li or D at the other end of the lever pivoted at A. The connection is broken by the paper coming into contact with the nose- shaped end of the lexer, which forces it out of the hole. The currents sent into the line are made by means of a local transmitter, which enables the man in charge of the instrument to tell by the sound hf)w the signals are passing out. An instrument of this description was tried with success on a land line of about 300 miles in length with a relay at the distant end transmitting the signals through 500 N.M. of submarine cable having a resistance of about 4,000 ohms and a capacity of 170 microfarads. The signals were RIXKNT DliVKLOl'MKNTS. 679 received on an Allan and Hrown suspended coil (cable) relay and recorded on an ordinary Morse instrument, with a speed of 45 words per minute. For recorder working the same transmitter may be used in a similar way, but an ordinary cable perforator would in this case be employed. Both contacts bein^^ of the same duration, the on!}- difference is in the external connection. Cable Relays. — With a view to effectinij; automatic, instead of manual, translation between lengths of submarine line, the cable relay nia\- be said to have been the dream of the cable manager for years, and one that has serious])' occupied the minds of many an electrician. The late Mr C. V. de Saut\', Mr Walter Judd, Mr Charles Cuttriss, and Mr E. Raymond-Barker have especial!}' turned their attention to tlie subject, but .so far no ab.solutel}' complete success has been met with in practice.* The first idea that occurs to the experimenter is n'lturally a rcla}- with fixed contacts ; but, as Mr Cuitri.ss nas expressed it, tlie " sticktion " here involved must always be fatal to success. Jioth Mr De Saut}' and Mr Raymond-Barker have endeavoured to turn the suspended coil to account as a cable relay. Some years ago the last- named devised an ai)|)aratus consisting of a suspended coil in a magnetic field with a projecting tongue to close two local circuits after the manner of Bright's Bells. So far, howe\er, it would seem that cable rela}'s are not within the sjjhere of practical tcletics — not, at any rate, when applied to the end of a long cable involving a varying zero at the rela}' in proportion to the .strength of the more or less exhausted current. -f- If this were to be made a theoretical success, the apparatus would necessaril}' be so delicate and complicated that it could never be left to itself It would, in fact, require the attendance of a skilled and experienced person. This being so, tlie human relay, or manual translation, method is the obvious remed}'. In a word, though it is possible that the cable relay ma}' be applicable to short circuits, in the ca.se of really long cables it does not appear as though it would be possible to obtain impulses sufficiently clear to operate any dead beat relay, such as would be required to actuate signalling levers. If, however, the cable relay could be made a complete success for those circuits which employ the siphon recorder, it might be turned to account in doing away with the siphon and the friction against the paper which takes * Since th( above was written, it is believed that Messrs Herbert Taylor and Arthur Deailove have obtained good results with a cable relay of their device. See patent specification No. 1 1,482""'. + As an alartaii relay, however, this instrument would work anything from a bell to a mid-day gun, or time ball. ^8o Sl'liMARINK 'IKl.l'.CKAlMIS. place at every vibration. If this could be effected, the result would be that of obtaining a sharper and more defined movement, reproducible upon a simpler, and less sensitive, local instrument* — especially in the instance of a long cable, where a gain of something like 20 per cent, in s|)eed might be realised as the result of the application of a really efficient rela\'. Automatic Punching. — In connection with the subject of repeating sjstems from one line to another, it may be remarked that cjuitc recently Mr Arthur Dearlove has devised an ingenious method of punching the Wheatstone transmitter tape at a distance.^ The punching instrument is constructed so as to be capable of being oi^eratcd by feeble currents — i.e., electric impulses — automatically transmitted through a land line or cable. The tape .so jjrepared does duty then in connection with a transmitter at the end of the cable through which it is desired to retransmit the message. This system works very well at a rate u|) to thirty W(jrds, or more, per minute, and it would seem as though it might have a cijiisiderable sphere of utility for working through a .series of cables with intermediate repeating stations, and when they could not be successfully worked through direct in a continuous length from the extreme ends only. This apparatus appears, at any rate, to well meet some of the difficulties encountered, as mentioned above, in cable-relay construction and working. * Hy watching the movement of the siphon cradle when the siphon is off, this jjain in tlehnitioi) becomes ap|)aient. t Patent specification N'o. 9,167 of 1895. S^««iW '-^■V-^^^ Cable-Laying up the Amazon River ; Station at I'arintins (\illa liclla). RKCKNT niiVELOI'MKNTS. 6Sl SKCTKJN 2.— PHKNOMKNA in LoNG-DISTANCK CaIILE 1 KLLGKArilV. The conductor resistance throttles the flow of current just as a partial stoppai^c does in a speakinjjf tube. Any throttiiii^r causes a sudden recoil or baci< thrust, which will hinder the next current, whether of air or electricity. This can be remedied by providing a leak, so that the accumu- lated air or electricity, instead of being thrust back, escapes as waste. This is what occurs at a large fault, and explains the splendid signals often obtained tiirough a faidty cable. The current which arrives at the far end is naturally weak, but a succession of such currents can follow with great rapidity because they are not hindered by recoil currents — i.e., currents which are echoed back by the CR, and which actually flow out at the sending end. Thus, theoretically s|)eaking, an increased speed of signalling should be obtained from a cable having a number of leaks judiciously arranged,* using such an electro-motive force that the current reaching the distant end would still be strong enough for producing sufficient influence on the receiving apparatus. Several electricians have ex])erimented in this direction (with various forms of artificial leaks,t condensers, induction coils, etc., interposed at different points along the line) both for purjjoses of high-speed telegraphy and long-distance telephony. Monsieur Godfrey, Professor M. I. Pupin, Sc.D., and others have tackled this tiuestion in different ways within recent years. Dr Pujiin proposed once more to increase the working speed of long cables by dividing them into sections and connecting them up by condenser repeaters. Though condensers at each end of a cable have a highly beneficial effect in cutting off earth currents, and in further improving the definition by curbing the signals, their interposition at random would probably be prejudicial rather than otherwise. It must be remembered that the dielectric of all condensers other than air condensers are possessed of considerable viscosity, thereby introducing material absorption and thus setting up a lag effect of some degree or other. No doubt need be entertained that success will finally crown the efforts * Professor (1. F. Fitzgerald, F.R.S., has very clearly defined in fuither detail the effect of leakage on wave propa^ ation through telegraph circuits in V'/ie Electrician for 24th May 1S94. t The idea of establishing leaks of a certain resistance between the conductor of a cable and the earth is now a matter of comparatively ancient history. The efficacy thereof for improving the signals on a long cable was first pointed to by the late Professor Fleeming Jenkin, F.R.S., somewhere in the sixties. 683 SUHMARINK TKI.KCK.M'IIS. already made rcf^arding these two problems, and that ocean telcphonj- will not be the last which electrical science holds in reserve as a benefaction for the years to come. So far as concerns any further substantial increase in the speed iLcain- able for submarine telej^raphy, it seems pretty evident that if this is to be effected it will be by an entire revolution in the form (jf conductor, dielectric and completed cable, rather than in the si^nallin^^ apparatus. The latter has probably reached its limits of sensitiveness — already extremcl)- hij,'h — and any further increased sensibilit)' of the instruments is likely to be at the expense of steadiness, and would tend to bring them within the range of influence of other surrounding forces. By way of improving the ])resent means of signalling upon cables, Mr Oliver Heaviside, i"".R.S. — who treated the subject mathematical!)- in the Pltilosophical Magazine \n 1879 — has prominentl)' advocated the introduction of both " leak " circuits and self-induction into cable lines. To jiractically effect some of the above ideas, electrical engineers have devised new forms of cores accompanied by devices which, to a certain extent, reali.sc the theoretical advantages put forward. Taylor and Dearlove's Leak Cable. — In the specification of a patent obtained by Messrs H. A. Taylor and Arthur Dearlove — \o. 13,136 of 1894 — we find the construction of a core described, which provides for the introduction of a leak circuit and self-inducti(jn being set up in the cable. This object is obtained by including two or more conductors insulated from each other in the same strand. In order that the covered and bare wires when laid up round the central wire should form a symmetrical strand, the weight of metal in the covered wires is so reduced that their diameter when covered is the same as that of the bare wires. The central wire is of iron or copper, and is insulated from the surrounding wires, two or more of which are themselves insulated. The wires rr, ^, and f (Fig. 137) are insulated with cotton. It follows that the grouping of the wires for signalling purposes may be made as Flo. 137.— Taylor .ind Dear- love's Leak Circuit Cable. RKCKNT l)KVi;i,()l'Mi:\TS. 683 thoii^'ht most desirable, each j^rou,' cunsistiiii^ (jf two coiili^fiioiis bare wires and one covered one. When the central wire is of iron, the self-induction of the circuit is increased, and in conseciuence the electro-static capacity of the core dinn'in'shed. Some experiments were recently made by Mr Arthur Dccirlove with variable " leaks " on two cables,* respectively I,130 N.M. and 1,066 N.M. in length, of the same CR per N.M. 'J'hc "leak" was in.scrted at the mid- station, or approximately in the centre (>f the circuit. This position Mr Heaviside recommends as the best when only (iiie leak circuit is inserted. The total ("R resistance of the circuit was 18,345 ohms, and the leaks at tlie central ])oint were varied from 10,000 ohms to 1,000 ohms. The conditions of the line during the work were as usual — i.e., both sendinff and receivinj^ condensers were in circuit, and a l)attery power of 50 cells was used with automatic transmission. As the " leak" resistance was varied from time to time, the same messaj^e at the same speed was transmitted, and the resulting signals on the siphon recorder carefullj' compared. The general conclusion of the experiment was that with 5,000 ohms to earth, the signals were more clearly defined than either under ordinary conditions or with lower resistance in the leak ; but such increased definition did ncjt admit of a higher speed of transmission, though the beneficial effect of the leak was distinctly noticeable. A more extended trial of this "leak" principle has been since made with an artificial cable, which lends itself peculiarly well to an experiment of this nature. A number of leaks were inserted at intervals along the line, and their position as well as their resistance was varied to find the most suitable and advantageous result. The effect of the "leaks" on the received signals was, as in the previously mentioned experiment, improved definition, in the arrival signal, which was in character similar to that obtained when curb sending is employed. The improvement noted was not sufficient to encourage the idea that, with the present receiving instruments and method of working, largely increased working speed is to be looked for by the adoption of the " leak." With higher speeds of transinission than at |)rescnt ordinarily practised in cable work, the "leak" principle may prove more efficient. * Zanzibar to Seychelles and Seychelles to Mauritius. 684 S f H M A i; I \ K T K 1. 1;( i R A I ' 1 1 S. Again, later, another experiment was made with a special form of leak, according to the joint patent of Mr H. A. Taylor and Mr A. Dearlove, already described and illustrated by Fig. 137. This, in place of an ordinary' fault, took the form of a shunt of high resistance between the main circuit and the earth. The conductor resistance of the main circuit being some 20,000 (0, the best results were obtained when the leak — placed about half- way along — was comjjosed of about 5,000 (». Automatic sending was adopted, and a marked improvement in definition was noticeable. But this was not sufficient to make up for the reduced amplitude of the signals, due to fall of potential and loss of current at the leaks. Independent Expert Opinions. -Mr F. Alexander Taylor, of the Eastern Telegraph Company, and Mr H. VV. Sulli\an, M.I.F.l'L., have independently come to similar conclusions, which they have made known quite recently in the columns of The Electrician. Again, Mr Rymer-Jones, M. I. E.E. (chief electrician on the Silvertown Company's cable expeditions), has made a series of ex[)eriments with leaks interposed in an artificial cable, his results — pointing the same way — being set forth in the Electrical Review a short while back. The onl)' conclusion arrived at in regard to the application of leaks on the ordinary cable circuits of to-day, is that when suitably disposed along the line, in obviating the choking effect of retardatioii, they secure increased definition for the signals, though not sufficiently to permit of any substantial increa.sc in the working speed — even with the batter)' power raised within reason. m^'- ^ w*Bf«.-..^ -^:;. '-9 -*WM,V,' i i 'gy wiii , 1* ' , ^i _. ,;li. r^ The Telegraph Sliip " Karail.iy. " RKCKNT DKVKI.Ol'MKXTS. GS; Skction 3. — New I'roi'oskd Mi:th(U)s for Rai'ID Cadlk- Su;nallin(; and Long-Distanck Caulk Tkleimionv. At various times and in \ariou.s ways different inventors have from time to time |)roiJosed schemes for abai^donint;- the use of the earth as a return circuit,* emplo)'ini^ a com|3!ete metalHc circuit instead. These schemes have sometimes taken tiie form of a cable enclosinij two separate insulated conductors, and sometimes diat of two distinct cables laid together. The first plan has already been adopted for telephony where the induction involved by an earth return (in the case of other cables similarK- usiiiLj an "earth return" are alongside) is an important item of retardation. It has of late years been also ])r()posed tf) apply it to ocean telej^raphy. As compared with the sijeed of si;4nallin Kic. 138. — .Silvamis Thonipsun's Proposed Cable, with Inductive Sluints or Leaks. diagrammatically .sections of the two-wire and of the three-wire portions of such a cable. The main conductors .\ and li are continuous right through the cable. The auxiliary, or neutralising, third conductor C constitutes the inductive shunt. A good deal of evidence exists, bt)th in the experience of the cable stations and in experiments made in the laboratory upon artificial cables, that shunts at intermediate points do have the beneficial effects which this new construction is designed to secure. It is thought by many that the path to success lies in the direction thus indicated. A new cable constructed on this plan would not cost twice as much as an ordinary ■"■ This, ajjiiin, renders it a comparatively non-invitinj; path for the current. Thus, a current travelling along it will be further delayed by being compelled by a natural law to magnetise the wire around it. To take a simih', if the water which fills a six-inch jiipe at good |)ressure tries to turn aside through a one-inch pipe crammed with tiny water-wheels, it stands to reason that the small bypath will not be an inviting one. So in the cable the main current ignores the thin wire, and passes on to do its duty at the opposite instru- ment. On the other hand, that bugbear tlie clinging current, being left liehind by the main portion of the current, leisurely saunters along the thin wire and into t.ie second wire, where it mingles with the returning current and is out of the way of the rapidly following signal. 688 Sl'IiMARIM". Ti:i KCRAl'llS. single cable, especially if the cost of laying — which is a large proportion of the whole cost — were taken into acconnt ; and, if properly pro])ortioncd, it is contended that it would have something lil( being unable to speak between iMigland and Germany.* Fu;. 141. — I'rccce's l'roper naut. Copper resistance, 5.163 ohms per nam. Inductive capacity be- tween diagonal wires, .09S microfarad per naut. Copper resistance, 5.163 ohms per naut. Inductive capacity be- tween diagonal wires, .loS microfarad per KK FER Naut, C'l.nsEU CiKci;iT. - 2.0719 Tests taken since laying the cable give excellent telephonic results, with perfect freedom from "cross-talk" and external induction. The inductive capacity of the laid 692 .SrUMAklNK TKLKCRArilS. Barr and Phillips' Cable.— Mr Mark Harr and Mr C. K. S. I'hillips have introduced to public notice yet anotlier ingenious solution to the problem of combining high efficienc)- with long-distance telegraphy and tele]jhon>-. They propose to employ what is practically a double con- ductor; but the return circuit for each wire, or grouj) of wires, would, in this case, be the earth again. The principle of this arrangement is, |)rimarily, that of having the helj)- ful leakage between two conductors at the centre of the cable instead of putting leaks between the core and sheath. In this device the inventors rightly recogni.se that, if leakage is obtained by the use of ]japcr or other ptjor insulation, the impervious quality of the cable is destroyed.* And on the other hand, if the leakage is obtained by putting connections from core to sheath, the resistance of the leaks is too low unless coils are used. In the Barr and Phillips cable the mode of signalling is such that the electro-static lines of force, extending from the multij)le-conductor core to B Kli;. 143. — IJarr and I'liillips' Proiiuscil I'liiii for High-speed Subiuaiino Telef;ra]ihy and Long-distance Telephony. the sheath, underg(j very little fluctuation during working. Mence the compound (or double) cT lii;\ l.l.dl'MKNIS. 693 of the cable at each key inoveinuiit, thus acceleratin^i^ the speed of trans- mission aside from an)' imjirovement (Uie to leaka^^e. On bcLjinnin^f to signal, the key (V'li^. 143) is in contact with the njjper conductor r, and a steady current is llowini; in that conductor from A to U. It umy be added that tlie lower conducting stranrl is negative to the upper. The ujjper contact is arranger! to follo\>- the key when the latter is depressed until connection is made with tiic lower contact. At this moment a rapid discharge takes place around th.> cnrl .\ of the cable. On further depressing the key — the movement being continuous, ofcour.se — the upper contact ceases to follow, and onl\- the lower contact touches the key. The current is now flowing in the lower strand I. and in the same direction as before through the cable — from A to i;. Between I. and l' (which, by the way, represent two ,;-jv/i/'S of wires alternateh' placed^ is an insulating material of comparatively low insula- tion resistance and low spL'cific inductive capacit\', such as jjajjer. The receiving instrument is a differential galvanometer. It will be seen that in this cable there is no wide departure nece.ssar)- in the process of manufacture, and that the cost depends upon the same elements as in the existing cables. It is claimed that the speed is faster with this arrangement than with any other disposition of the same weight of copper and gutta-percha. Moreover, it is said to be j)0ssible to duple.\ this cable. in conclusion, it is but fair to suppose that we may be on the eve of developments of a fundanental and radical character in the methods of submarine electrical communication, more especially, and suitably, as regards the structure of the cable. Langdon-Davies' Phonopore.— Long-distance telephony through sub- marine cables — and the telephone la combination with the telegraph — are forcing them.selves on the attention of inventors. Thus, within recent }-ears experiments have been made with Mr C. Langdon-Da\ies' phono- pore system on submarine cables. If the cable be above a certain length, however, capacity stands in the way of success in that direction. This instrument, invented and patented in 1884-85, will be found fully described elsewhere. It certainh- forms a most valuable adjunct to land- line systems for purposes of diplex telegraphy — the line being ws a more powerful battery into the secondary ciicuit where the heaxier work has to be done. In its norminL; die line of .itlion by means (if llic clevalcil transmitter anil leieixcras above, a niaiked increase in the lanj^e of ctt"ecti\e transmission is seemed, tlioii^li it is not so easy to explain how this comes about. At first sij^lit it might appea to be due to the waves being thereby enabled to reach the recei\ er without passing tlirou;^!! hills or other solid obstructions, which no doubt lia\e a greater resistance than the air. lUit the advantage of thus raising the sphere of o])erations has been experienced without the existence of hills /.(■ , in cases of a level suiface of water between ti'.insmitler and receiver. t With reference to the abo\ e, it may be (.|UCstioned in jiracticc. if the rei elvers were in close juxtaposition, whether they would not interfere w itli one another electrically. 'I This gentleman, however, pointed out that his apparatus — crude as it was at that time would jirobably work through a distance of half a mile. " \viKi:i.i:ss" I i:i.i:(.K.\i'iiN'. 701 ])ro\e iiualual)lL' ; * and to Sij^nor Marci'iii iiolliiiiL; l)ul praise is due tor the inL^enuit}- and |)orse\crance with whicli he has developed a successful jiractical application of some of the latest disco\eiies in electrical science — like others who have revolutionised commerce and added to the wealth of nations by facilitating^ interchantje of intelligence. Here we ha\e a remarkable example of the disinterested manner in which the I'ost Office authorities reall\- take U|) an invention that seems |)romisinL;-. It should be remembered that Mr i'reece had for some time been e.\perimentin,n' in the direction of Inductive TcleL;raph\' on lines of his own, but w nen Marconi's system was lirought to his notice he immcdiatel)- recoi^nised its superiority — as he stated, indeed, in the course of his recent Royal Institution lecture (previouslj- alluded to), from which the material for this section is very lar^jel)' drawn. t For further information on the subject the reader is csi)eciall\- referred to the columns of the Electrical Revieiv.'i Ti:.sla's Rksi;ai<(I1i;s. Mr Nikola Tesla is said to be at work on another form of wireless telegraphy, the idea of which has been in his mind for a lon^- time. It may be remeitibered that when in England .several j-ears a^o he prophesied that telci^raphic messai^^cs would yet be sent through the earth to Australia— certain!}- a simplification of the Pacific cable cjuestion ! — and not only messat^es, but electric power, if need be. Mr Tesla now claims to have maile j^ood his words to the extent of sending electric signals through 20 miles of ground without any conducting wire. According to his own account he seems to have found the problem rather easy to soke ; but he will not \ouchsafe any information as to how * A j;reat deal of scnsiuidnal nonsense lias been -.vritten in popular joinnals and ne\vs|)apers about Marconi waxes penetrating metal as easily as anythinj; else, notwith- standing the time-honoured doctrines of Faraday. They may, however, lie regarded in the hght of "florid imaginations" pointing to some "striking ijicuiie ' — in this case that of men of war, gunpowder maga/incs, or forts, being blown up though many miles out of sight — bul witli these we ha\e nothing to do here, beyond referring to them with ridicule. + " Siiy.ialling through Space without Wires," b\- \V. il. I'reece, CH.. I'.K.S., repro- duced i.i The Elcctritiiin. \ Since going to jiress .Signor Marconi's complete specification (Xo. 120,369 of 1S96; has been published, the patent ha\ing been accepted on 2iul July of the present year (1897). ///(■ Electriciiiv of 17th September, whilst giving a very full abstract of this, also reproduces some e.vcellent jihotographs of Dr Lodge's somewhat similar apparatus for the same pur|)ose, shewn at the Oxfortl 15. .\. Meeting of i8<;4. 702 Sl'l!\l \kl\K TKI.I'.CkAl'llS. he (loL's it until liis work is c<)ni|jlctc. All wc know is that he eni|)lo\'s \ ibiatory currents of electricit)', and waxes, or osciikitions, set U|j !>)• them in the luniiniferous ether. I'his latter is comiiiLj to be re^rardeil not onl)- as an inexhaustible store of power, jjut a uni\'ersal vehicle of jjower — a kind of all-round, (omnipresent, yearinjf. Other wonders may yet be in store for us, or the comini; generations, but in the meanwhile the cable manufacturer need have no misj^ivint^s — neither need the tele^ra|)h engineer. West African Tclct^rapli C"oiii|)any : Loanila Cable Iliil. * The intcrobt, if ni)l the satisfaction, with which tlie reader may now close this volume would certainly have been increased if only photoj^raphy had been equal to the task of reproducing the prevailing smell at this benighted ami picturesque spot ! APPENDIX, RECORDER" SI(;i>IALS UNDER VARYING co>,DrnoNs. Tm. ij-.i'iKk ' a'' UNcrRiiKD and Cuki;i:d. Without Cur/'/ux'. (n X.R. = -3 // 'I't/i Cur/'i»^\ (-^) X./?. = / 2 \^ (3) /f./P. = 3 6 (4) /f.^.= 76 (5) A./i. == //e Actual Signals obtained throigh Muirliead's (Inductive-Resistance) Artificial Cable, under dififercnt conditions. N.B. — Case (l) has pnictUal'y no retardation, and Case (5) has proportionately a great deal. INDEX. AHEL, Sir F. A.- gutt.i-pcicha experiineins, 266 Presidential Address to the Society of Telegraph Engineers (i876\ 183 Ader telephone, 207 phono-signal systeni, 586, ujj "Advice/' H. M.S.. '39 Afghan Campaigns, 1878-80, use of tele- graphy in, 174 Africa, South, direct telegraphic comnninica- tion |)roposc(l, 174 African Direct Telegraph Company, 1^4 "Agamemnon," H.M.S.— British Ciovernment lends, for laying first Atlantic cable, 36, 44, 45, 48 cable machinery on, 23, 86, 94 Ailhaud's duplex telegraphy, 124, 5S3, 658 Airy, Professor G. H. (Astronomer-Royal), on first Atlantic cable, 51 ".Albany," S.S., .Atlantic, 1866, jable ship, 95 Aldham, Capt. W. C, H.M.S. " Valorous,' 47 receives ' W'.., 49 Aldini, early ccp rimcnts by, I "Alert," H.'m.T.S., 193, 195 Alexandria, use of telegraphy at bombard- ment of, 174 Algiers-Port \'endres cable, (>(> Algiers-Toulon cable, failure of, 65 Allan, Mr Thomas, lighi cables, 494, 495 Almeida, Jose d', intiriiuces gutta-percha into EuroiJc, 248 .•Mphabet in cable telegi ^ihy, 568 element unit and woi ' unit systems, 568 international Morse 1 ode, 553, 554 Steinheil's, 603 Aluminium bronze sheathed cable of Messrs Bright, 507, 508 .Amazon Ri\cr cable, 127, 128 lead tubing for, 389 .Amazon Telegraph Company, cables by Siemens Brothers for, 127 .American Telegraph and Cable Comjiany, 132 Amos, Mr J. C, Atlantic cable gear, 42 "Ampere," French cable ship, 70 Anchorage, fouling cables by, 179, 180 Anderson, .^m' James — Captain, S.S. "Great Eastern,' 88, 97 Eastern Telegraph Company, 120 knighted, 102 "Statisti(s of Telegraphy," 177 .Andrews, Mr W. S., I'ender Memorial. See Preface •Anglo-.American Telegraph Company — capital of, 91 formation of, 91 French .Atlantic Cable Company merged with, 107 speed on, 575 total mileage of cables, 574 Anglo-Continental cables, 194, 391 .Anglo-Danish cable, 112 •Anglo- Dutch cables, 15, 16, 93 Anglo-French line, 6, 7, 194, 251, 252 .Sec " Dover-Calais Cables " Anglo-German cables, 15 „ Government cables, 194, 489 „ „ ,, specification, i89i,Appendi.\ III., Part II., 516-522 Anglo-Indian Telegraph Company, Sir Charles Bright and Mr Latimer Clark, engineers to, loS Anglo-Irish cable, 14 Anglo-Mediterranean Telegraph Company, 106 merged in Eastern Telegraph Company, 119 Anglo-Spanish-Portuguese system, 128 Appleyard, Mr Kollo, molecular theory of conduction, 268, 697 .Annealing, ])roccss of, metals, 220, 221 Ansell, Mr W. T., jubilee of, 20c 706 IN1)K\. Appolir?^ hiakc, 42, 43, 86 Arl)iti;iti')ii, Imi'iiiiUioiial, iiinucini' of sul)- nuirinc tclcjjiapliy on, 170 Arlincourt, I)', relay, 582, 58C) Armstrong, cxpi'iiincnts hy, in Ilutlson Ki\ IT, 4 Arsenic, etTccl of, on loppcf und concluctiNity, 217 Asplialte, ])ieservati\c for shcritliinj; wire, 64, 422. See " \U\'^\n and Clark' Atliciitiiiin, rih\ correspondence re speed throuj,di Atlantic cable, 53, Si, 566 Atlantic, 1857-58, cahle, 23-56 accident on hoard "Niaj^ara" while laying;, 40 Atlantic 'I'elej^rapli Company rej^istcreil, 49. 50 breaks during laying; operations, 40, 44 liright. Sir Charles, engineer in charge, 32, 33. l^^ IJritish (iovernment support to, 31, 36 capital raised for, ji conductivity of cable, 221 congratulatory messages from Queen \'ictoria to President of United Stales, 49, 50 construction of, 33 cost of manufacture, 35, 253 electrical appliances, 43, 44 engineers and electricians engaged on, 32, 33. 36, 52 failure of, 50, 5 1 first message on, 48, 49 induction coils, 50, 161 instruments for working, 32 landing Irish end, 46, 47 landing Newfoundland end, 46, 47 laying operations, 38-40 laying by two ships towards each shore, 44 length of, Y:,, 47 Liverpool support for, 31 machinery for paying out, yj, 41 " Magnetic" Company's support to, 31 paying-out trials in ISay of Biscay, 44 ])rojeciors, 28 public rejoicings on successful laying, 49, 50 repair of Irish end attempted, 50, 51 results demonstrated by, 5 1 route selected for, 30 section of, '^}i setting out of first expedition, 38 setting out of second expedition, 44 Atlantic, 1857-58, <:i\h\c—((>)ilinii,ti sheathing of, 421 ships engageil in laying, 38 shore ends of, 34, 39 soundings for, 29, 30 speed on, 51 splicing in mid ocean, 44 st()|)page of communications, 50 ■ United States Ciovcrnment ;.upport, 37 Whitehonse, Mr Wildnian, electrician f'"'. ■>:■> Atlantic, 1865, cable, 78 breakage of, 90 breakdown of, 105 construction of, 82, 83, 84 condensers usetl on, 105 cost of, how defrayed, 82 diameter of, 83 dragging for lost end of, 99 ex|)e(lition started, 88, 89 failure of picking-up gear, 90, 91 faults discovered, 89, 90, 105 machinery, S.S. "(Ireat Eastern," 86 message on recovery, 102 paying out, method of, 87, 94 recovery of, 90, 99, 100, loi, 102 repair of, 92 section of, 83 shipment of, 85 shore ends of, 84, 85, 87, 102 speed on, 105, 540 test of recovered, 101 type of, sub ,ec|uently disappioxed, 83. 84, 90 Atlantic. 1866. cable, 78 breakdown of, 105, 128, 129 breaking strain of, 93 condensers used on, 105, 539 construction of, go, 92, 93 cost of, how defrayed, 82 diameter, 93 faults in, 105 landing shore ends, 97, 98 length of, 93, 98 paying-out machinery, 93, 94 repair of, 128, 129 results demonstrated by, 98, 104 shore ends, 93 speed on, 105 success of, 98 tests, by Mr Willoughby Smith, 96 weight of, 92 Atlantic, 1869, " French," cable, 107 route of, 107, 132 speed on, 556 INUKX. 7U/ St.'itfs," Atlantic, 1873, " Anj^lo," ( ahli', i:;8, 575 I oiistnirtion of, 14^ (liiplcxL'd, 637, 647 speed on, 670 AtlaiUii-, [.S74. "Anglo," cable, 128 construction of, 142 dti])le\in>,', 659 ^peed on, 670 Atlantic, icSSo, " An^;lo," |<-ct loi-, opposed, 55 profits derived from, 144 raising capital for, 80, 82 routes proposed for, 79 result of private enterprise, 152 suggestion to suspend by buoys, 55 .•\tlanti( Telegra|)h Companv- - amalgamation with Anglo- .\nierican Telegraph Companv-, 91, 144 board of directors, 22 capital, 31, 79, Si, S2 consulting (ommittee for 1865 cable, S( debentures issued by, 31 formation of, 31 projected, 28 renewed efforts of, 79, 80 registration of, ;, 1 subsidy from Hritish Ciovernment, 31 Azores cable, 140, 145 Ayrton. Prof. W. )•:.— " Practical I'^lectric ity," 185 " .Sixty \cMs of Submarine Telegraphy," 526 BAC.(;S, IsiV.iin, duplex telegraphy, 122 Bain, tra;ismitting instrument, 141 Balata gutta, Mr Thomas liolas on, 259 Balloons, proposal to suspend Atlantic cable l5y, 55 Baudoin, Mons. V. .M. - light cable patent, 494 device for laying up v\ires, 432 Barclay, Mr Henry Ford, financial promotion of 1866 Atlantic cable, c)\ Barker, Mr K. Raymond. See " Raymond- Barker" Barlow, Mr W. H., evidence in telephone- telegraph case, 201 Barlow and Foster, Messrs, patent of, for insulation by gutta-penha, 249 Barr, Mr Mark, Barr and Phillips' proposed high-speed and long-distance cable, 692 Bateman-Champain, Sir J. U., Indian tele- graphs, 112 President of the Society of 'I'elegraph I'-ngineers (1878), 1S3 Beauvisage, l)r, classification of gutta-percha, Becker. Mi' Charles, origin of Elliott Brothers, 161 -OS iMii;.\. Becqiiercl — specific conducti\ itv of coppei', 216 electrical effect iif tcnipcratuie o\i copper, 15eer, Mr Julius, fuiancicr of early cable projects, I 20 lieeswax as an insiilatiiij; substance, 352 Hell, Professor (iraham, "speakint; tele- graph," 201 ISell teleiilioiie receiver, 207 Helz, Mons., cxiicriincnts in electrical transmission with condensers, 549, 550 Hclz-Hrahic system of automatic transmis- sion, 141, 662 Benest, Mr II. coast telegraph communication, 187 grapnels, yg submarine rivers and springs, 164 Bennett, Mr Ciordon, promoter of '" Com- mercial ' Company, 135, 136 Bergue, Mr C. de, payingout machinery by, 37 Berlin, ])ro])osed telephone to, 2oS Bern, headquarters International 'rdegraph Administration, 142, 177, 17S Bcrryman, Lieut. (). H., Atlantic soundings by, 28, 29 Bessemer steel process, 83 Bevan, Mr F. A., original director and pro- moter of Eastern Telegraph Com- pany, 120 I'ender Memorial. See I'reface Bewley, Mr Henry — financial promotion of 1S66 Atlantic cable, yl gutta-percha covering process, 301 tube-making apparatus, 250 Bidder, Mr (ieorge, (Huermnent Committee in i860 on submarine telegraphs, 5y Black Sea Telegraph Company, 120 lilondot and ]5ourdin, Messrs, light cable, 497 " Blazer," S.S.. lays first Dover-Calais cable, 1851, 12 Boat Race, The I'niversity, telcgrajjliic de- scription of, 168 Bolas, Mr Thomas-- on gutta-percha, 259, 327 on intlia-rubber, 334 ISolton, Sir Francis — formation of Society of Telegraph En- gineers, 180 telegraph code, 175 Bonfires, interruptions to cable caused by, Bordeaux, Mr j. engineer to the Sul . ' rine Telegraj)!) Company, 1 1 marine superintendent, Postal Tele- graphs, iy5 ISorel, .Mr, modification of Hughes' ])rinting apparatus, 586 ISorneo guttapercha and its (pialities, 258, 353 Bouell, Sir Mackenzie, on Pacific cable pro- ject, 152 Brahic, Mons., transmitting instrument, 141 Brake — .Xjfpold, 42, 86 drum, 17 H.M.T.S. "Monarch," 197 paying-out machinery, 20, 41, 70, 87, <)4 Branly, Mons. Kilouard — wireless telegraphy, 697 coherer, 697, 698 ISrass taping for cable core. See " Ta])ing, Metal" llrassey, Mr Thomas - on first Board of Eastern Extension Compan\-, 1 20 supjiort of Atlantic cable schemes, 1865-66, 82, 91 Brazilian Submarine Telegraph Company's cable system, 46, 116, 124, 127, 128, 139, 147, 165 Brest -St Pierre cables, 107, 132, 312, 547, f>33 Breton > Capei, Newfoundland, cable, 27 Brett ISrothers concessions by French (Jovernment to, 5, 10 proposals by, to Sir Robert Peel on English Channel cable project, 5 Brett, Mr Jacob- early endeavours to unite F^iuo|)e and America, 27 (ieneral Oceanic Telegraph Company, interest of, in, 5 ]3;itent modification of House printing instrument, 5 Brett, Mr John VVatkins— F^nglish Channel scheme, 5, 6 his interest in submarine telegraphy, 5, 6 projection of first .Atlr.ilic cable, 27, 32 Spczia - -orsica and Sardinia - Bona cables, 17 Briggs, Mr J. A., quadruplex telegraphy, 661 IXDKX. "0(/ Hriijlil, Sir Chailcs Tilston, IS6 Anglo-Indian Telegraph Company, en- gineer to, 108 Anglo - Mediterranean Company, en- gineer and electrician to, 107 Atlantic Telegraph Company, promoter of and engineer to, 32 Balearic Islands group caljles laid by. 65 hanciuet to, 49 i)ell telegraph instrument, 1 iS, 586, 636 bituminous preservative compound for sheathing cables, patent for, 75. See "Bright and Clark" brass ta|)ing of core, patent for, 69 British - Indian Extension and China Submarine Telegraph Company, engineer to, 109 compound (hot and cold), 75, 422, 423, 424, 455, 456 conductor (wormed), 74, 229, 230 core recommended l)\-, for Atlantic right, The Right Hon. John, M.P., support of Atlantic cable project, 80 " Britannia," T.S., 165 British Association- Committee on Electrical .Standards and Units, 61, 63 papers read before, on submarine tele- graphy, 184 British-Australian Telegraph Coinpany, 108, 120 Piritish Government — acquisition of land telegraphs by, r 10, 193 Board of 'i'rade Committee on Sub- marine cables, 59, 60 cnier|)rise in telegraphy, 110, 145 land, and submarine lines under, 194 subsidies by, to submarine cable schemes, 31, 57, 59 survey of Atlantic ordered by, 79 British-hulian Submarine Telegraph Com- pany, loH '■ ISritish- Indian Extension" Conipany, 120 British and Irish .Magnetic Telegraph Com- pany, 5 Brittle, Mr J. R,, engineer to Submarine Cable Department of Siemens Brothers and Co., 157 Brooke, Lieut. J. M., sounding apparatus, 29 Brooke, Sir William O'S.— director of East India Company's tele- graphs, 2 experiments across the Hugh, 2, 246 method of insulation, 2, 3, 246 Brown, Mr James Wallace, 587. .See "Relay, Il'rou.-.-Allan " Broun, .Sir William, .Xtlantic Tclcgi.iph Company, 32 Broun, Lenox, & Co. — experimenis for first .Atlantic cable, 33 grappling apparatus, 96 testing machine for cables, 485-4S7 lirure- Warren, Mr 'T. P. — india-rubber core mixture, 343 soldering mixture, 364 Brunei, Mr L K. sheathing for cables, 2)5, 34 design of S.S. "Creat Eastern,' 85 Buchanan, Mr J. Y., survey for Spanish National cables, 134 Bullivant, Mr W. ^L- light cable design by, 501 unlaying and laying-up of cable, 503 Bullock, Mr '{'. .A., superintendence of high- speed working before Li Hung Chang, 168 Buoys — type of, for 1866 .Atlantic cable, 95 marking route by, 7, 410 picking up cable, employment of, 101 suggested use of, for suspending sub- merged cable, 55 Burbridge, discoverer of /s<>/iii/i(/i,r •;////, i, 253 Burck, I)r William, classification of gutta- percha, 254 Bureau Internationale ties Administrations Telegraphif|ues, 177 c ABLES air-spaced, 641 air in, tests for, (13, 64 alarm wires for, 143 Allan's light, 494, 496 aluminium, Messrs Edward and Charles Bright's, 506. 507 Barr and Phillips' proposed double- core, 692 Blondot and Bourdin, M.M., design b\. 497 branch, 114, 126 break in, discovery of, A92 breaking strain of, 57, 72, 413, 482, 4S3, 500 capital invested in, 167 cement, use of, for, 383 close-sheathed, 125, 426, 500, 501 coast, 188 INDEX. I 1 Cables continued coiling, into tanks at fai:t(ir\-, ^|^]^, 502 completed, 480 conipouiKl, HriKlit and Clark's, 74, 75, 422, 423, 424, 455, 456, 458, 461, 463 conductor. See " CondiictDr ' construction. .See " Construction " cooling, 464 core. .See " Core " cost of construction, lAj, 491 cost of layinj^, 163 cost, total of, 153 deep-sea, 410, 41 1, 471, 47.5, X^'^-, ^"^9 depreciation of, 165 y tkptli of water in uhicli laid, 65, ''x;, 13S, 140, 147, 165 design for, principles considered, 232 duplication of, 121, 165, 166 tle\il)ility of, 48S fouling anchorage, 179, 180 fouls in laying up, 476 grapnels, 95, 96, 99, 182 gravity, specific of, 496, 497, 49^5, 499, 501 lock a.moured, 143 machinery and implements, 160, 402 machinery, by Messrs Johnson and Phillips, 427, 428 machinery, H.M.T.S. " Monarch,' 197 manufacture of, 464, 474 marine growths on, and enemies of, 57, 118, 125, 138, 164, 190, 192, 208, 381, 382, 389, 405, 423, 500 multiple-conductor, 3, 14, 163, 400, 401, 413, 577,680,690 number and lengths of, 153 numerous |)atents for, 494 open armoured, 84, 125, 426, 500 o.\idising influence of sea-water on, 500 paying-out and picking-up machinery, 16, 37,41,86, 87,93,94, 197, 198 I'reece, Mr W. H., suggested improve ments by, for, 186 pressure of water, etTect on, 104 (.[uadrupiication of, 121 recovery and repair, 18, 99, 109, 147, 165, 166, 501 resistance, electrical. See " Resistance" Cables— ((V///////(V/ rocks, effect on, 57, 11 ^ 141, 4" serving, intermediate, 13 serving, outer, 455, 458, 471 shallow-water, 197, 198, 481; sheathing. See '' Sheathing '' ships, 161, 196, 200. See " Ships" shore ends of, 7, 84, 116, 143, 41 1, 473 shore ends and land lines, connection of, 582, r,77 speed of working. See " Speed " storage at factory, 476, 477 stowing, 477 telephone, 206. See " Tele|)hone '' temperature, effect on, 104 tensile strength of, 482, 484, 495, 499 tests for, 225, 232. See " Tests " testing during manufacture, 478 testing machinery for, 60, 484 torsion apparatus for, 484, 502 triplication of, 1 21 variety of types for, sections of, 408 weight of, 7, 12, 13, 14, 18, 21, 22, 28, SI, 34, 50, 58, 62, 65, 73, 74, 82, 83, 97, 116, 142, 195, 197, 231, 232, 455, 466, 480, 48 1 wet, necessity for keeping, 63, 85, 481 whitewashing newly manufactured, 477 unlaying cable after manufacture, 502 worming machinery, 402 Wright's, Mr E. P., design for, 498 Cables to — .\bdullah, 76 Aden, 57. 58, 123, 130, 131, 297, 551 .Adriatic Sea, 136 .\le\anilria, 62, 64, 106, 107, 271, 272, 621 Algiers, 60, 64, 65, 66, 67, 1 [9, 530, 573. 599 .\mazon River, '117, 128, 388 > .Xmoy, 1 1 4 .Antilles (The C.reater and Lesser), 1 16 " Atlantic." See " Atlantic Cables " Australia, 108, 120, 145 .Azores, 140, 145 Hacton, 388, 489 Baghdad, ill, 490, 378 iialaclava, 21 Balearic Islands, 65, 136 liallinskelligs Hay, 647 Hallycarberry, 39 liarcclona, 65, 130 ^ • Hathurst, 135 Heachy Head, 164 ^ Heaulieu, 691 712 IN'DKX. Cables Xo— continued Belfast, 208 Iieli^ium, 14 llehrinK Strait, 1 13 Beloochistan, 75 Benghazi, 64, 135 Beimuda, 125, 13S, 139, 145, 147 Bilbao, I 19 Black Sea, 2i, 112, 120, r!i3, 391 Bombay, 57, 58, 107, 108, 130, 297 Bona, 16, 17, 65, 647 Brazils, 46, 116, 124, 127, 128, 130, 139, 147, 165 Brest, 107, 132, 312, 547, 633 i5reton (Cape), 26, 27, 227 Buenos Ayres, 107. 133 Bush ire, ']'^ Calais, 5, 11, 663 Canary Islands, 134 Canso, 312, 601 Cape of Good Hope, 131 Cape Town, 135 Carcavellos, 109 Cartagena, 65, 68, 213, 49C1 Chili, 130 China, 109, 112, 115, 116, 120 Cliuy, 127 Colon, I 16 Columbia, 1 16 Constantinople, 73, 111, 121 Continent (Anglo-Coniinental), 194, 341 Corfu, 22 Corsica, 16, 17 Cuba, r 16, 137 Uemerara, 1 16, 126 Denmark, 16, 112, 115, 194 Donaghadee, 14 Dover, 5- 1 1 Dublin, 25, 169 Egypt, 62, 108 Falmouth, 62, 104, 109, 119, 142 Fano, 663 Fao, 73, III Fernando de Noronha (Island of), 140 Florida, 1 16 Foochou , I I 5 (;ermany, 15, 112, 114, 194,489 C.ibraltar, 62, 109, 119, 142 CiUano, 137 (iurnard's Bay, 691 Cwadur, 73 Hallania, 58 Halifax, 129, 138, 147 Havre, 164 Heart's Content, 98 Cables Xq- continued Holland, 15, 16, 93 Holyhead, 13 Hong-Kong, 114, 116, 666 llowth, 13 India, 108 Ireland, 13 Italy, 16 Ivica, 65 Japan, 112, 115 Khov, 76 Knight's Town, 39 Kurrachee, 58, "Ji La (luayra, 137 Lima, 130 Lisbon, 104, 109, 140 Loanda, 135 Madagascar, 140 Madras, 108, 123 Mahon, 67 Majorca, 65 Malacca, 70, 163, 384 Malta, 22, 62, 63,64 lof), 107, 109, 119, 271, 272,621,647 Marseilles, 119, 130, 139, 549,55^.573, 599,621, 647 Mauritius, 131, 145 Mediterranean Sea, 106 Mexico, 116, 133, 312 ^linorca, 65, 67 Mozambique, 140 Nagasaki, 1 14 New Caledonia, 140 Newfoundland, 26, 27. 227 New NOrk, 4, 26, 131, 227 New Zealand, 120, 145 Norway, 16, 194 Nova Scotia, 26, 129, 647 Odessa, 121 Oran, 65, 68, 139, 213, 496 Panama, 1 16, 133 I'ara, 125-127 I'aris, 131, 132, 205. Cables " I'enang, 70, 1 23, 384 Penzance, 601 Pernambuco, 125, 139, 140 Persia, Ti, 77, 112 Peru, 130, 133 Porthcurno, 109, 132, 590 Portpatrick, 14 I'ortugal, 128 Port X'endres, 66 Queensland, 140 Rangoon, 62 See " Atlantic INDF.X. 713 fables to -continued Red Sea, 37 Rio de Janeiro, 127, 225 Rio de la Plata, 127 Rochfort, 312 Russia, 112, 113, 121 St J ago, 134, 135, 169 St I.oiis, Senegal, 135, 139 St F;):l de Loanda, 135 St I'ien-e, 107, 132, 312, 547, 633 St Vincent, 134, 135, 469 San Antonio, 65 Santiago, 133 Santos, 127 Sardinia, 16, 17, 22, 65 Senegal, 134, [39 Seychelles, 131 Shanghai, 114, 115 Singapore, 62, 163 Spain, 1 19, 128, 130 Spezia, 14, 16, 17 Suez, 58, 108, 130, 297 Sweden, 16, 112, 194 Tory Island, 312 Toulon, 65, 66, 67 Tiipoli, 64 Tunis, 139 Turkey, 57 I'ruguay, 127 Valparaiso, 127, 130, 131 X'arna, 21 Vera Cruz, 133 \'igo, 590 X'iseu, 137 Wexford, 425 Calais, cable sheathing works at, 137 " Calabria," T.S., 139 Campbell, Mr A. H., financial interest in submarine telegraphy, 91 Canary Islands cable, 134 Canning, Sir Samuel — assistant engineer to Atlantic Telegraph Company, 36 Atlantic, 1S65, cable, 88 plan for reco\ering, 99 Atlantic, 1866, cable, expedition, accom- panies, 97 calile machinery by, 86 Cape Breton - Newfoundland cable, en- gineer in charge, 27 evidence before Ciovernment inquiry, 1859-60, 60 ,_ . knighted. 102 Malta-Alexandria cable, 63, 64, 107 Marseilles- Algiers cable, 1871, ri9 Canning, Sir Samuel --(VW//>///(Vi' partner with Mr R. Sabine, 156 'I'oulon-Algiers cable, 67 t'anvas, for insulating purposes, 351, 352 Capacity — Atlantic, 1858. cable, influence of, on speed, 80 artificial cable for du|)lex working, 122 dimensions, type, and lay of copper conductor, effect of, on, 219, 227, 231, 232,496 electro-static, of gutta-percha, 281, 578 calculations for, 282 Hooper's core, 1 59 india-rubber, 337, 343 retardation, influence on, 203 reduction of, and increased speed, 186 speed, how affected by, 81, 232, 537 test for, 76, 234, 324 overhead wires, 638 speed of signalling influenced l)y, 566, 567, 577 Capacity, electro-static inductive- Chatterton's compound, 237 "Commercial," 1894, cable, 575 discussed, 328, 329 electrical transmission, etit'ect of, on, puritv of gutta-percha, how atitected, 253, 263 retardation and, 185 short cables, 205, 232 Capital Atlantic cable expedition, Mr Cyrus Field's exertions to raise, 80, 81 invested in cables, 165, 167 Carcavellos, Lisbon, cable, 109 Carlisle, Karl of, on Atlantic cable expedition, Carmichael, Sir James, assists early attempts to connect England and France by sub- marine cable, I r "Caroline," S.S., Atlantic, 1865, cable, Irish shore ends laid by, 87, 88 Carrington wire-testing machine, 416 Cecil, Lord Sackville, I'ender Memorial. See Preface Cement, use of, for protecting underground tubes, 383 Chamberlain, Right Hon. Joseph, M.I'., con- venes conference on .Ml- British Pacific cable, 146 and Transvaal affairs, 174 Champain-Bateman, Lieut.-Ccneral Sir J. U., and Indian telegraphs, 73, 1 1 1 714 i\ni:.\. Channel cable (1850), 5-1 1 Chattcrton, Mr John, patent for lead tnhing cabk' i:()\er, S9, 301, 3S1; ("hattenon's compound, 58, 62, C>6, 74, 82, I iS, 206, 237, 30S, 309, 314-316, 424, 497 orii;in of, 63 patent for, 63 pressine, applied under, 315 weight of, in strand, 240 in G.l'. coats, 300, 317 Chauvin, Mr G. von, 1881 Jay (iould cables, I'endcr Memorial. See Preface Chcescnian, Mr H. (.',., on the use of photo- graphy for recording mirror signals, 633 China, opposition of, to telegraphy, 114, 115 Clark, Mr Edwin — cable ship's gear, designs by, 16 ;Mtta-percha, on, 266 work on Committee of Inquiry on Sub- marine Telegraph Cables (1859-60), 59 Clark, Mr Latimer— accumulation joint test, 74, 394 Anglo-Indian Telegraph Company, engineer to, 108 conduciivity of various species of copper, 2r6 ( (inductor, segmental, 74, 230, 575 "Electrical Measurements," 60, 493 "Electrical Tables and Formuhc" (Clarkand Sabine), 493. See Preface electrical standards and units, 61 experiments by, for Atlantic cables, 104 ( lovernment inquiry ( 1 859-60), assistance of, 59, 60 partnership with Sir Charles Bright, 74, 155 Persian C.ulf cable, 74, 393 preservative for sheathing wire, 422 See " Bright and Clark's Cable Compound ' Society of Telegraph Engineers, one of the founders (1871), 180 Presidential Address (1875), 183 telephone synonymous withtelegra[)h, 20 1 weight of iron wire in cable construc- tion, 454 See " Bright and Clark " Clark, Forde, and Taylor, Messrs — Amazon River cable, 128 " Anglo ■■ Atlantic cable, 1894, 488, 575 tables of working speed by, 578, 579 tests of sheathing wire, 420 Clark, Mr Thomas, chief electrician to Tele- graph Construction Company, 594 marine gal\ anometer, 594 Clerk Maxwell, Professor — electric waves, 696 electrical standards antl units, 61 Clifford, Mr Henry, 36 Atlantic, 1858, cable, 36 Atlantic, 1865, cable, 43, 88 Atlantic, 1866, cable, 97 brass taping for core by, 69, 3S4-386 cable ship machinery by, 37, 41, 43, 86, 93. 94 Malta-Alexandria cable, 63, 64 Telegraph Construction Comjiany, en- gineer to, 156 Coast cables, utility of, 188 Code and cipher system, 167, 173, 175 alphabet, (wi example of, 176 international alphabet, Morse, 568, 601 necessity for, 176, 177 words, 568 Coils — auxiliary discharge, 585, 586 resistance, electrical, 65 Whitehouse's induction, 50, 51, 52, 161 Coleman, Mr Andrew, signalling apparatus, 587 Collett, Mr Richard Atlantic, 1857-58, cable expeditions, 46 „ 1S65-66, ., „ 97 Colomb, \'icc-Admiral, mode of signalling between ships, suggested by, 77, 100 "Commercial" Company's Atlantic, 1884, cable, 135, 136. Set "Atlantic Cables" "Commercial" Company's Atlantic, 1894, cable, 141, 143. See "Atlantic Cables" Channel, 1884-S5. cable, 312. See "Atlantic Cables " Newfoundland shore ends, Atlantic, 1894, cable, 143 speed on Atlantic, 1894, cable, 574 Commercial influence of submarine tele- graphy, 171 Commerell, Admiral Sir J. E., H.M.S. "Terrible," Atlantic, 1866, cable expedi- tion, 99 Committee (Ciovernment) of IiK|uiry on the Construction of Submarine Tele- g^raph Cables constitution of, 59, 60 report of, 60, 245 Committee (British Association) on electri- cal standards and units, 61 INDKX. / '5 Companies- African Direct, [34 Amazon, 127 American Telegraph and Caijie Com- pany, 132, 601 Anglo-American, 91, ro7 Central anil South American, 126, 130, Companhia Telcgratit a I'iatino - Brasi- liera, 127 Compania del Telegrafo 'I'ransandino, 130 Direct Spanish, 119, 130 Direct United States, 128, 129 Eastern, 119, 120, 153, i()(<, 194 Eastern Extension, 113, 120 Eastern and South African, 131, 135 J'21cctric Telegraph Company, 16, 110 Great Northern, 1 15 joint purse with Eastern Extension Company, 130 India-rubljcr, ( '.utta-percha, and Tele- graph Works Company, 117, 1 ;7. See "Silvertown Comjjany " Indo-European, 111, jSr La Compagnic Fran<;aise dcs Cables Tc'legraphiciues, 132, 140 La Compagnie Fran(;aise du Telegraphe de Paris a New York, 131 La Compagnie P"ran(^aise des TcIl'- graphes Sous-Marins, 126 La Compagnie du Tclc'graphe Sous- Marin, 1 1 La Participation des Cables Antilles, 137 La Societe Frani^aise des Tclegraphes Sous-Marins, 132, t37, [40 La Societe Cienerale des Telephones, "39, 140 London-Platino-lirazilian, 1 27 Magnetic, British and Irish, 5 Mexican, 133 Montevidcan and Brazilian, 127 New ^'ork, Newfoundland, and London, 26, 227 Pacific and European, 1 33 Postal, r.S.A., 116 River Plate and Brazilian, 127 Societe (Jenerale des Telephones, 137 Societe du Cable Transatlanticpie Fran- gais, 107 Societa Pirelli, 136 South American, 1 39 Spanish National, [34, 139 Submarine, 1 20 West African, 131, 134 Com|)anies— (W///////,v/ West Coast of America, [30, 131 West India and Panama, 116, 582 Western and Brazilian, 125, 582 Western Union, 1 if> Compound, core. See " Chatterton's ' „ cable. See "Bright and CI; Conductivity — Atlantic, 1865, cable, 82 metals, electrical qualities o*", for, 277 method of ascertaining, 234, 235 pressure effect on, 91 purity of metal used, 54, 214-216, 21 sectional area, a factor in, 219 temperature, effect on, 91, 277 tests for, 76, 77, 222-224, 234, 235 Conductor — Allan's light cable, 495 Atlantic, 1857-58, cable, 35, 54 .Atlantic, 186;, cable, 82. "Anglo" .Atlantic, 1894, cable, 575 Barr and Phillips' double, 692 Bright and Clark's segmental, 74, 230, 575 capacity, 81 continuity in, 21,22 copper, 6, 215, 216 diameter of, 232 electrical qualities, 214 electro-static, capacity of, iSi'i formula for lay of wire for, 241 formula' and data, 231 gauge of wire for, 240 insulating, method of, 243 joints in, 235, 360. See "joints " la\-, length of, 241, 330 leading principles involved iinlesign material composing, 232 multiple, 3, 14, 18, 163, 388, 400, 401, 577, '')89, 690 Persian Ciulf cable, 74 purity of, substances used for, 54, 268 resistance discussed, 54, yj. 205. " Resistance " salt-water, 271 scarf joints in, 363, 366, 376 segmental, 74, 229, 230, 575 single, 74, 227, 401, 402 solid and stranded, 74, 227, 228, 230, 573 solid-strand, 27, 227, 228, 232 spiral, 215 speed of laying uj) wire for, 240 4'3. 267, See ■J\() INDEX. Conductor — ionlinucd strain on, 218 stranding wires for, 236 tests, electrical, of wire previous to manu- facture, and calculations, 222, 223, tests, electrical, after core manufacture, 324 types of, 231 weight of, 231 u ormud, 74. See " Core " Concessions, rights conferred by, in France and Kngland, 3, 10 Condamine, La, introduction of india-rubber, Condenscrs, 105, 107, 541, 681 vS^ duplex telegraphy, 122, " Duplex Telegrapliy ' Conference, International Tclegrapli, See '73, Contriictors for cable worU, position of, dis- cussed, 155 Convention, International, 1884, Telegraph, 151 '«75, ^li, '75, i7^> Cooke and Wheatstone's — needle instrument, 9, 145 method of insulation, 244 jubilee celebration, 200 Copper - alloys, effect on, 218, 219 anneale„ 324 tests (electrical) applied to, after pres- sure, 330, 331 tests (mechanical), 321 tests, pressure, 329 iniprotecteil, suggestions for, 391 Warren's, Mr Bruce, 345 weight of, 318 winding covered, 312 Cornell, Ezra, (able by, in Hudson River, between Fort Lee and New ^■ork, 4 6V)/7/// ///. I Ai;j,'-(i::/'//d>, telegraphy and cable work literature, by Charles Bright and A. I'. Crouch, I, 184 Cost of cables, total, 153 construction and laying, 163 Cost of messages, 143, 144 Cotton, use of, for insulating purposes, 244, 35', 352 Coulon, Mons., London- Paris telephone, 205 ('o\ering machine, (Iray and Gibson's, 302, 306, 425, 520 Cranipton, Mr T. K. — engineer to Submarine Telegraph Com- pany, 10, 1 1 ILnglish Channel cable laid by, 1 1 Crinoline for paying out apparatus — Sir Charles liright's, 31 Newall's, 19 Crookes, Sir William, radiometer, 602 Crouch, Mr A. I'., literary contributions by, on submarine telegraphy, 184 CuUey, Mr K. S.— engineer to H.M. Post Office, 195 " Handbook of I'ractical Telegraphy," by, 582. See Preface Culley, Mr W. R., marine superintendent, H.M. Postal Telegraphs, 195 Currents — electric, 2t, 25, 51, 52, 203, 543, 563. See " Transmission, Electrical " ocean, 410 Cuttriss, Mr Chailes automatic transmitter, 673 cable rel.iys, 6)9 modification of siphon recorder, 615, 6r9 suspension piece and \ibrator, C119 D 'ALMEIDA, JOSE, introduces gutta- percha into Europe, 248 D'Arlincourt relay, 582, 586 Data of cables, electrical, forms for, .Appen- dix 1\„ Part n. Data of cables, engineering. Appendix IV., Part H. Dayman, Commander, soundings of .\tlantic by, 28, 29 Dearlove, Mr .Arthur — Atlantic, 1894, cable, 116 automatic curb transmitter, 671 cable leaks, C)S2 punching (automatic) apparatus, 680 relay, 679 tables, 578, 674 transformer for signalling, 561, 562 de Bergue, Mr C, paying-out machinery by, 1,1 Delany, Mr P. B.— automatic transmission system, 374, 667, 670 curbs and curbing transmitter, 560 relay and sounder system, 676 speaking system, 076 synchronous multiple telegraphy, 667 De la Rue, Mr Warren, Covernment tele- phone case, 201 Denison, wire-testing machine, 416, 417 Depth of water, 65, 69, 13S, 140, 147, 165 effect on cable life, 165 repair of cable, 103, 147 d'Erlanger, Baron Emile, 107, 120 Dickenson, Mr W. — transmitting key, 627 \ ibrator, 616 T)i])lomacy, how influenced by submarine telegraphy, 1 70 Direct .Spanish Telegraph Company, 1 19, 130 Brown-Allan relay adopted on, 590 Morse system used by, 581 rejjair of cables in deep water, 147 7KS iM)i:\. Dirci'l Cniicd States Cilile C'()iii|),iiiy < oiulenseis, use of, ')y, zyi (onstiiu tion of 1S74 (able, 230 duplexing' on system of, 123, (^y formation of, 12S, \2') Dividends, guarantee of, 57 Dover-Calais, rSjo, lin(-, 5-11 coniluclivity of, 22 1 construe tion of, 6, 7, 251, 313, 391 I' lendi concessions for, 5, 6, 10 insulation of, 25 1, 25.. jr2, 313 laying of, «, 72 Dover-Calais, 1851, cahk', 11 construction of, 11, 213 inner ser\int; of, 391 insulating covering, 213 laying of, 12 opening of, 1 2 sheathing for, 213 Suhmarinc Telegraph Company, worked by, 12 vitality of, 13 Draper, Mr (ieorge, secretary, Eastern Tele- graph Company, 130 Dresing, Mr I'. C. cable construction, 690 cable shore ends for rocky coasts, 116, '43 sheathing, [45 separate taping of multiple c ol■el^, 578, 690 Drums, construction and uses of, in paying- out machinery, 41, 70, 87, 95, 19S Dudley, Mr Robert, Atlantic, 1865-60, cable expeditions, 89 Duplex telegraphy, 123,635 Ailhaud's system, 124, 583, 658 aniticial line in, 639, 642, 643, 644, 645, 658 Atlantic, 1894, cables, 574 batteries used in, 640 liaggs, Isham, antl, 122 Bright, ISrolhers, patent for, 122,635,636 „ Charles, article in /uii^iiiccriiii; on, 650 condensers used in, ro,, 107, 122, 561, 583,638,639,647,651,681 differential princi])le, 635-637, 655 difficulties of, considered, 657 defined, 583, 635 "double-block," 641, 642, 655 English patents for, 635 Farmers system, 122, 636 Frischen's system, 122, 635, 636 Gintl's system, 122,635,637 Duplex telegraphy iontiiiuiil Cilocsiner's system, 122 llaruood's method, 124, 583, 657, 658 illuslratiiins and examples, 646 Jacob's, Mr Frank, methocl, 659 lantl lines, 638, 639 lectures on, by Mr I'rcece, 636 long cables, 647, 653 long circuits, directions for, 653 Maron, Mons., system of, 122, 636 modern practice, 1^43 Muirheail's method, 123, 124, 583,643. 644, 645, 64(j double block in, 650, 655 Newall's patent for, 122, 635 perfection of system, 142 I'rcece's patent, 122, 635, 636 Sabine's, Mr K., apparatus, 042 Sauty, Mr C. \'. de, system, 123, 583, 642 short circuits, directions for, 652 Siemens, Werner, and, 636 Siemens and Halske system, 636 siphim recorder and, 639 Smith's, Mr I'.eiijamin, method, 124, 656 speed obtained by, 577, 647, 6)48, 653 Stearns' system, 121, 122, 583,638,639, 640, 641, 655, 656 systems compared and discussed, 655 Taylor's, Mr Herbert, system, 123, 583, 642, 655 Thomson , Lord Kehin; system, 122 tinfoil used in, 642, 644 Varley's, Mr C. F., artificial line, 639, 655, 658 Wheatstone bridge system, 636-639, 641. 642 Dynamometer T- Sir Charles Uright's design, 42 use of, in paying-out machinery, 71, 87, 94 EAKLK, Mr C. W., on the life of a cable, 164 Earth cimnection for cables, 599 Eastern Telegraph Company, 119, 120, 130, 153, 194 Silver Jubilee of, 166 Eastern Extension, Australasia, and China Telegraph Company, 115, 120 Eastern and South African Telegraph Com- pany, 131, 135 INDEX. ■19 Easton and Amos, Messrs, inachinciy for paying out Atl,inti(, it^jK, iiiblc, 37, 41, 4:! Easton, Aiidt'isoii, and (iookUn, Messrs, 42 Ed^far, Mr Robert H., and Muirlicad's ini proved siplion recorder, C117 Edwards, Mr Francis, 6 lu/iiifiiiii;/! A'lTvVii', articles on submarine telegrapln-, 1S4 Edinl)ur}jli, Royal Society of Mr lUichanan on soundinj,'s, 134 Professor Thomson, address to, gr Eiectiic rtle^ra|)h Company, \(\ Gosport-l'ortsmoLith cable, ?4^ insulating process of the, 244 International Telegraph Company, ant! the, amalgamation of, iCi London- Manchcstci- underground line, 251 multiple-core cables of, 401 winding up of, 1 10 Electric waves, 26, 526, 527, 61/1, 697 F.lcitricdl l''.iii:;iiu-ii\ i,S;,. See Preface lilectricdl Min^tizinc, iiS3 lUcctriciil Rc7 attempts at submarine telegraphy in, 4. See " Channel Cable" English Channel, 1850, line, 6-10 ad\erse criticism on attempt to lay, 9, 10 broken by trawlers, 9 experiments for, 8, 9 failure of, 9 method of laying, 7, 8 result of attempt, io. Sec "Channel Cable " English Channi'l Submarine 'Telegraph Com pany, 6 /■'//i,'/'//C(7-, 7//1', 91, 183. See Prefacc /'.'// i,7V/(VV ///:,', I S3. See Prefai e Erlanger, liaron Emile d', 107, 120 Esselbach, Dr, Persian (ndf (able, 7'i Everett, Mr W. E. Atlantic cable gear by, 41, 43 sei\ ices on first .Vtlantic cable expedi- tion.-, (1857 ;8), 45, 49 pr\HIE, MrJ. J.- •T "A History of Electric 'Telegra|)hy to the ^■ear 1837," 1 on fault loialisation, 182 Fairbairn, Sir William, Commission on Con- struction of Submarine Telegraph Cables (18601, 59, 60 Atlantic, 1865, cable, 80 gutta-percha, experiments by, 266, 267 Factories, submarine caljie English, 132, 172 Foreign, 132, 136, 137, 139, 172 Faraday, Professor cable speed, on. 54, 81 electrical application of gutta-percha, 248 " Faraday," S.S., cable ship, 37, 161, 162 " Farad," derivation of term, 61 Farjou, application of the Moisc s\stcm by, 586 Farmer's duplex telegraphy, r22, 636 Faults localisation of, in cable, 84, 105, 182 at factory, 329 Felten and Guilleaumc, Messrs, ir, aerial telephone cables by, 690 brass taping for multiple-conductor core, 577, 57S, 690 insulating material suggested by, 351 lock-armoured cable by, 143 Ferranti, S. /. de, composition of concentiic cables by, 352 Field, Mr Cyrus — Atlantic, 1857-58, 1865 and 1866, cables, 46, 47, 78, 89 energy and interest of, in submarine cable projects, 26, 27, 28, 32, 79, 82 financial assistance secured by, for Atlantic, 1866, cable project, 91 general manager, Atlantic Telegraph Company, 79 journeys of, on cable work, 80 Trans-Pacific cable proposal by, 140 20 IMUA. K ield, Mr Josluui, first Atlantic calile ^ear, 41 1 ish, flcstnictioii of caljics by, 125, 138, \(->o, i'i4, i(;o, 208, 3S1. Sec "Teredo" itZK'crald, Professor (I. K., on leakage, 681 it/^teraUl, Sir Peter, his welcome to Sir Charles 15rij,'ht and other Atlantic cable pioneers, 48 izeaii, on the propaKation of electricity, 52(, la\, for insulating; cables, 351, 352 leniinj,', Dr J. A., Ciovernnient telephone case, 201 Icmin),', Sir Sandford, Pacific cable pr(ije( t by, 152 oochow cable, 1 1 5 orbes, Mr David, Electrical Standards and Units Comniittee, 61 orbes, Professor (Jeorjje, lectures on "Alter- nating and Interrupted Klectric Cur- rents," 563 oilhomineruin l!ay, Irish shore ends of Atlantic, 1865-66, cables, landed at, 87, 1 88, ,,7 orde, Mr II. C. ! "Anjflo" Atlantic, t894, cable, 489, 575 I " British- Indian '' cable, 108 Malta-Alexandria cable, 62, 63, 181 | joins in partnershi|) uiili Mrtiisborne, '55 joins in partnership with Mr Latimer Clark, I 56 sheathing, 60 unprotected core, 39 r breshore rights and cable landing, 179 oster, Mr A. Le Neve, gutta-percha cover- t ing machine suggested by, 302 oster, Professor (".. C, Electrical Standards and Units Committee, 61 Foul flakes," 92 burier, etpiations for jiropagation of heat ind electricity, 526, 529 ex, Sir Charles, financial promoter of tirst Channel line (1850), 6 lance, Mr J. K.— branch cable method by, 1 14 designs T.S. " Silvertown," 161 South American cables, 125 Submarine Telegraph Company, 1 1 Fran(;ois Arago," T.S., 141 rench cable to— Algiers, 60, 66 Atlantic, 107, 108 England, 194 West Indies, 137 Madagascar, 140 !'■ rench enterprise in cable work, 137 French and Cicrnian Pai ilii s( hemes, 140 Frischen, llerr C, duplex telegraphy, 122, '''35. ('/> I'roment relay, 582 C"^AL'r()N'. Douglas, Captain Sir Jf Hoard of Trade Commission M860), 59 submarine cables committee of advice /■<■ Atlantic, 1865, cable, 8(i (lalvanising process for lablu sheathing, 34, «3, 407, 4 "A 4^1, 495 ( ialvanometer - marine. Professor Thomson's, ',3, 44, 52, (>i reflecting. Professor Thomson's, 44, yy (lauge, standard wire, Appemlix I., Part 11. (iauss and Weber's reflecting telegraph ap paraius, 43 Cavey, .Mr J., experiment by, in imUutive telegraphy, 186 Ceneral Oceanic Telegraph Company, 5, 27 (ieographical .Society, Royal - .Atlantic cable routes discussed by, 79 Mr lluchanan on siu'vey and soundings, 134 German cables, 15, r 1 1, 194, 489 C.erhardi, Mr Charles, first .Atlantic i 1857-581 ( aljle expeditions, 46 Ciibson, gulta-percha covering machine, 302, 306,425, 520 (JintI, Dr, duplex telegraphy by, 122, 583,635 Ciisborne, Mr V. N., smvey and cable work by, off Newfoundland, 26 Cisborne, Mr Lionel - concessions to, for Red Sea and Hast Indian cable, 57 joins Mr H. C. Forde, as consulting engineers, 1 55 (lisborne and Forde, Messrs — cable testing by, 60 .Malta-.Alexandria cable, 63 report on breaking strain of cable mate- rials, 60 .Sue/.-Kurrachee cal)le, 58 testing apparatus by, 484 Cilass tubes as insulating envelope, 244 Class, -Sir Richard, tirm of Class, Elliot, and Co., I 56 Atlantic, 1865, cable, 85 „ 1866, „ 91,97 Ciovernment committee (i860), assisted by, 59, 60 INDl'.X. r^l (ilii^i, Sir Ki( hard— "'////"//(•;ra|)li Construe tioii Company, f<2 (ilash, Klliot, and C"(),, Messrs, 156 .\nKl"-I>ut(l) rahlf, l^i Atlantic, rS57 58, (able, 30, }}, 41 iHC-j, „ So lSf)6, ., So ( iMtM-perclia C electrical transmission, (>Sf (ioldsmid, Major-C.cncral Sir F. J., telegraph to India, 7} " C.oliath,'' steam tug, English Channel cable, 7,8 (loocli, Sir Daniel - assists Atlantic cable projects, 85, 87, 89,91 baronetcy conferred on, 101 (ioodyear, Mr Charles, on vulcanising india- rublier, 33ft Cordon, Professor Lewis, 431 (losport-l'ortsmouth, insulation of cal^le, 246 C.ott, Mr J., curb signal device, 551 Could, Mr Jay, iiromotestwo Atlantic cables, 13^ (Hiunclle, M., projjagation of electricity, 526 Granmiont, Mons., Madagascar cable, 140 Granville, Mr W. !>.— air-space core, 690 inducti\e telegraphy, 186 Crapnels - Atlantic, 1866, cable, 95, ^/> designs for, 9d, 99, 182 Cirappling ropes - construction of, 95 tests for, 487 tkaves, Mr Edward, 183 engineer to H.M. Post Ofifice, 193, 195 (liaves, Mr James, 101 curb signals for long cables, 537 on the causes of failuic of deep ■ -ea c ables, 506 dray, Mr Matthew gutta-percha covering; mac hine, 302, 30^., 320, 425 taping sheathing wires, 425, 426, 427, 428. 45« Cray, Mr K. K., 1 19 double le\er signalling key, 597, 598 engineer-in-chief to Silveriown Com pany, 1 19 I'ender Memorial. See Preface Cray, Mr M. H.. T-joint box, 126 '' Creat Eastern '' S.S., 79 Atlantic, i865-f)C), cable expeditions, 85, 88, 96, 98 cable work, suitability of, for, <>i coaling of, 98 construction and history of, 85 French Atlantic, 1869, cable, 107 payng out Atlantic, r866, cable, 98 paying-out mac liinery, c^4 pic king-up mac hinery, 94 propelling mac hinery, '/> recovery of Atlantic, i8C)5, cable, 100, 101 section of, 86, 144 speed of, ()6 (Ireat Northern Telegraijh Company, history of, 112, 115 China land lines, 1 15 core adopted by, I 13, 339 Eastern system of, 339 , extension of system, 1 13 joint-purse with Eastern Extension Com- pany, 130 Russian concessions to, 1 14 Great Western Telegraph Company, 125 Griffith, Mr S., cable machinery of S.S. "Great Eastern," fitted by, 8n Ciuille.iume, 57S, 6c;o. See ' Felten and Ciuilleaume " ( '.ulstad, brass taping for multiple-core cables, See " Dresing and GuUtad " Gutta-percha — chapter on, 248-331 cost of raw, 253 manufacture, 253 absorption of, 266, 267, 271, 277, 278, 576 age of, 275, 279, 281, 282, 325 Anglo-French cables and, 251 722 INDKX. (iutta-percha — ionlinitid average produce, 258 liolas, Mr 1"., 011 testinj;, 327 I5()nieo, superiority of, 25cS electro-static inductive capacity of, 26J, 28., 572 calemlcriiij,' into sliects, 293 C'hattertons compound and, 366 chemical ])ro])erties of, 262, 269 analysis of, 260 classification of, 254 'lean sing, 257, 286 coagulation process for, 257 coats, separate, 252 single, 313, 330 collection of, 253, 257, 269 commercial and manufactureil, 263 cooling and harilening, 310 core covering, 299. 307, 312 cost of, 253, 331 covering macliines, 45, 249, 301-309 Channel, 1850, line, 6, 1 1, 252 crack, liability of, to, 279 cultivation of, 259 damaged by marine organisms, 264 density of, 269, 276, 278 deterioration of, 349 die-covering machine, 249 durability of, 263, 301, 327 early use of, for electrical purposes, 2, 3, 4, 248, 249, 251 electrical application, 248 properties of, 265, 26S, 269, 278, 301 l-'.lcctriLal Ri'viciv on, 261 exportation of, 285 extensibility of, 215, 264 French cultivation of, 259 growth and appearance of, 255, 256 history of, 253 homogeneity of, 269, 276, 278 introduction into this country, 248 importation of, 258, 285 india-rubber combined uith, 355, 497 india-rubber and, relative merits coin- pared, 349 insulating c|ualities, 247 introduction in Englantl, 248 investigations concerning, 60 Isonandra, 253 jointing cores, 366-375 lead tubing, ertect of, on, 389 machinery for manufacturing, 204, 295 manufacture of, 285 mastication process, 269, z'iU-zi.yo, 299, 327, 328 Gutta-percha — (Vv///// /A ■(/ niechai^ical cpialities and jiropcrties of, 247, 262, 269, 297 mixtmes of, 32S moisture, effect on, 267, 280, 297, 298, 300, 310, y.-] multiple-coat covering, 312, 330 native, 262 oxidation, 265, 26f., 280, 285, 297, 528, 366 ozone, effect of, on, 265 perspiration of jointer, effect of, on, 372 physical |)roperties of, 268, 277, 302, 348 ])reservative for sheathing wire, 424 pressure, etfect of, on, 271, 278, 282, 325, „ application of, under, 331 |)urity of, 301 purifying, 266, 285, 295 raw material, 285 rejuvenation of old, 324 resistance, insulation of, 266, 270, 271, 297 scarcity of, 258 Smith's, Mr Willoughby, 'jrocess, 297, 572 sources of, 248 specific gravity of, 26J storage of, 285 straining process, 291, 292 taping, 265 temperature, effect of, on, 264, 265, 271, ^l3, 276, : 78, 282, 325 tests of, 326 tests for mixtures of, 327, 328, 348 thickness of, for covering, 82, 312 torpedo cable, used for, 347 weight and diamtter, 283 (lutta jiercha Company — Atlantic, 1857-58, cable, s'S Glass, Elliot, & Co., amalgamatio'", wiih, 82, 156 Malta-Alexandria cable, 64 Persian Gulf cable, 74 underground lines, 251 work of, 1 56 H.VIR lor insulating purposes, 351, 352 Halifax-Iiermudas Cable Company, i3'\ '47 llalpin, Captain Kobert.S.S, "( Ireat llastcin,' 88, 107 Hamilton, Captain, ll,M.S, " .Sphinx,'' 88 IXDKX. 7-3 Hamilton, Mr F. A. — lit,'lit cable by, 501 on submarine teleffrapli cables, tbeir decay and re])air, 503 unjayiii); and layiii.L; up of onlinaiy iron- slieathcd cables, 503 1 iancock Brothers' gutta-percha experiments, 24S, 251 Hancock, Mr Chailes— cable compound, 237 experiments with gutta - percha, 248, gutta-|)ercha mixture, patent of, 249 purifying system for gutta-percha, 286 Hancock, Mr Tbomas— experiments for india-rubber insulation, masticator machine. 286 \ulcanising india-rubber, 336 Hancock. .Mr Walter, |)urifying systems for gutta-percha, 248, 251, 28C) Harwood, Mr, du|)lexing method, 124, 583, 657, 058 " Hawk," .S.S., cable ship, 1 14 Hawkins, Mr Frederick — patent for taping sheathing wires, 425, 45« application of, 426, 427, 428 plan for whitewashing cable, 477 Hauling oft" completed cable at factory, 472, 473 Hearden's patent for insulation, 353 Heaton, Mr J. Henniker, M.l'., refornis pro- posed by, 1 73 Heaviside, Mr O. "distortionless cable,'' 18C), 575 proposals for the future, 185 s|)ced of signalling, 577 Hem|), use of, for cable construction, 12, iS, 83, 84, 92, 93, 382, 384. .See ".ServiuK, Outer" Henley, MrW. T., cables manufactured by— .\nglo- Mediterranean, 109 .Atlantic, 1865, shore ends, 87 iSalearic Islands, 65 Far Eastern cables for Great Northern Company, 1 1 5 {•"rcnch cables, West Indies, 137 Halifax- Hermudas, 138 Montevideo-Chuy, 127 Persian Ciulf, 74 River Plate, 127 St I'ierre-.Sydney, 107 .Sweden-Scotland, 112 Sweden-Russia, 1 12 Henley, .MrW. T., 158 galvanising wires, 408 india-rubber insulation, 346 magneto-electric instruments by, 26 outer canvas taping by, 458 ozokeritted india-rubber core, 349 sheathing process (patented) by, 432, 433 wire drawer and cable mannfactiner, 408 Henley Telegraph Works 'Jo}ii|)anv, [58. .See "Henley, MrW. T." Herbert, Sir Robert, chairman, Telegraph Construction Company, 109 I'ender Memorial. .See Preface Herz, l)r Cornelius — developments indicated by, 189 proposed international administr.ition, >77 Hertz, Professor Heinrich, on electric waves, 185, 696, 697 Highton, Mr Edward, suggested ty])e of cable, 1 1 History, utility of studying step by stej), of inventions. See Introduction Hockin, Mr Charles — electrical standards and units, 6r Messrs Clark and l''orde, 156 speed, on, 577 Holyhcad-Howth cable, 13 Hooper, Mr William Hright and Clark on core by, 339 cable core by, 337, 339 method of jointing cable, ^77 \ulcanising process for india-rul)ber, 15S, 1 59, 247 Hooper's 'rdegraph and India-rubber Works Limited, 112, 113, 160 Far Eastern cables by, 1 14 (ireat Northern Company's, 1S70-71, cables, 160 lead tubing for |)rotccting core, 389 india-rubber core, 112, 113, 346 .South American cables by, 125, 160 " Hooper," T.S., 162 Ho|)kinson, Dr John, Co\ernment telephone case, 201 Hoski.vr, Col. \'., Far Eastern cables, 1 14 House, Professor Royal, printing apparatus, 5,8,116 Houston, Prof. E. J., on low insulation cables, 692 Hudson, Captain W. L., U.,S. Frigate " Niagara," 57 \ ■ . Hughes, Prof. I). E.— evidence, CJovernment committee (i860), 53 ■24 iM)i;\. Hughes, I'rof. I). E. ioiittiiiiid microphone, 201, 202 printing appaiatus, 58d telephone-teletiiaph, on, 201 Hunter, Caplain J. K., H.M.S. " X'cstal," 1 17 ICK and ii el)ergs, danj,'ers to cable from, 30, 105, 143, 148 Illustrated London Xeivs^ submarine tele- graphy, 8, 23, 34,44, 195 Imperial federation, as atiected by submaiiiie telegrai)hy, 170 India-rubber — absorption by, 335, 344, 576 age, effect of, on vulcanised, 344 air, effect on, 335, 345, 346, 34, resistance.insulating, of,327,337, 345, 350 resistance, specific, of, 337, 345, 350 speed through indi.i-rubber cables, 57S temperature, influence of, on, 344, 348 test for quality of, 343 tinneil copper for, insulation, 438 Truman's process, 354 varieties of, 332, 333 vulcanised, 158, 159, 247,336, 337,339, 340, 342, 343 water, effect of, on \ ulcanised, 3J6 where obtained, 332 India-rubber, ("lUtta-percha, and Telegraph Works Company, I 17, 157. See " Silver- town Compan\ '' Indian cable (Persian Ciulf , 73-76 Indian dovernment anil submiuine tele- graphy, 73 Indo-Kuropcan Telegraph Company — formation, i 1 1 joint-purse with Indian Telegraph De- partment and " Eastern" Company, 130 Morse system in use, ^Si Induction coils, 50, 51, 52, 161. See "Coils" electro-static and electro-magnetic, 690 metal tajiing .ind its effect on, 388 telephone, 203. See '' Transnnssion, Electrical" Inducti\e telegn'.phy, 186 Institution of Civil Engineers, submarine telegraphy pajjers read at, 81, 180, 181 Institution of Mechanical Engineers. suli- marinc telegraphy papers read at, 94, 181 Institution of Electrical Engineers — promotion of, 181 submarine telegraphy pajiers read.it, 181 Instruments, electrical, 161 Insulation, 243 See " Chatterton's Compound " cotton, 244 early methods of, 2, 4, 243, 355 electrical tests for, 76, 77. See " Tests " gutta-percha, 249. See "CiUtta-percha ' Hooper's method, 158, 159, 336, 337 imperfect, 231. See " Leaks, artificial " india-rubber. .See " India-rubber" jacobi's method, 244, 335 lead tubes, 246 - - — ^- pilch, 244 tarred yarn, 2, 245, 246 various suggestions for, 243, 245, 246, 351 INDEX. 725 In\oslme;.ts in sviljiiiarinc telegraphy, 165 1 1(111 wire — for sheathing purposes, 66, 403, 419, 420 soft, 4 1 5 telephone cable, for, 206 test of, 413, 414, 419, 420 testing machines, 415-417 Isaac, Mr Percy, device for bows of cable ships, 196 Italian Oovcrnnienl cables, 136 J.\C()I!, Mr Frank, electrician, Siemens ISrothcrs and Co., 157 duplexing method by, 659 modification of the " mirror speaker " '5y. 593 recorder suspension piece by, 619 transparent scale for reflecting instru- ments, 593 Jacobi, Professor, method of insulation, 244, 335 Janiieson, Professor .\ndrc\v — core covering suggested by, 390 duplex telegraphy, 124 " Electrical Definitions, Nomenclature, and Notation." .See Introduction grapnels, 99, 182 lightning protector for cables, 582 Pocket-book of " Electrical Rules and Formula" (Munro and Jamieson), 161, 492. See Preface Jay Could cables (1881-82), 132, 573 Jenkin, Professor Fleeming — automatic curb sender, 551 construction of submarine telegraph cables, on, 181 electrical standards and imi's, on, 61 " Electricity and Magnetism," 556 insulation resistance of gutla - percha core, 267 joins partnership with Sir William Thomson, 155 lecturei5 by, 184 light cable advocated by, 494 (Jiiiirh'r/y RcTii'ii', contributions to, on submarine telegraphy, by, 184 Spezia cable picked up by, 21 unprotected core, 391 Jersey, The Earl of, report by, on Pacific cable project, 149 "Jockeys," use of, in paying-out ajiparalus, S6, 87, 93 Johns, Mr K. M. See Preface Johnson, Mr Claude — cable machinery and apjilianccs by, 160 grapnel devised by, 99 partnership with Mr S. V.. Phillips, 160 Johnson and Phillips, Messrs- cable gear, H.M.T.S. "Monarch," 196 cable machinery and apparatus, 160 canvas tape for outer sheathing applied by, 458-460 grapnels, 99 india-rubber insulated cables, 161 measuring drum, 478 reputation of, 160 sheathing machines, 448, 458 sounding aiiparalus, 29 wire taping device, 427, 428 Joints, jointing — Atlantic, 1865 cable, 84 binding wire for metallic, 363, 364 branch cables, 126 brass, 236 Channel cable (first), 6 Chatterton's compound used in, 366 cleanliness essential for, 357, 372 conductor, 234, 360,361, 376 cooling mixture for core, 371 electric welding process for sheathing wire, 357 faulty, causes of, 54, 373, 378 gulta-percha cores, 366-375 imi)lements used for, 357, 358 importance of the operation, 356 method of making T-piece, 126 Persian (kilf cable, 76 proposal to avoid, 56 quality of gutta-percha used for, ■'i-j-', scarf, in conductor, 363, 366, 376 sea, performed at, 356, 371 sheathing wire, 435, 436 single wire, 235 tests of, 74, 372, 375, 394 time required for, 372 tin soldering in, 366 tropical climates, in, 374 vulcanised india-rubber, 376, 379 weak, 54 Jona, Signor E., author of "Cavi Telegra- phic! Sottomarini," Italian C.overn- ment cables, 136 .See Introduction Joule, Dr J. P., electrical standards and imits, 61 3D 726 INDEX. Jubilee of subiiiaiino telegraphy - commemoration proposed, 180. See Preface Judd, Mr Walter- cable relay, 679 modification of " mirror speaker," jyj Jute, 391, 392 breaking strain, 394 serving multiple-conductor cables, 392, 397, 400 specific gravity, 394 tanned, 392 tarred, protective serving for iiV(ti^anz(i on Atlantic, expedition, 89 "The Oican Telei^raph to India,'' 108 Pasley, Colonel, early experiments at Chat- ham and Spiihcad, 2, 246 Patents, utility of studying specifications. See Introduction I'aston, Sir Joseph, his interest in Mr West's Channel cable scheme, 4 Paying out — angle of cable in, 409 Atlantic, 1857-58, cable, machinery for, yi. 39, 40. 41. 45 Atlantic, i865,cal.ile, mac hinery for, 86, 87 Atlantic, 1866, cable, mac hinery for, 93, 94. 9f^ ISright, Sir Charles, apjiaratus for first Atlantic cable ex|)edition. yj, 39, 40, 41 (litiriculties of, 83, 84 difficulties of, when light, 497 Pesrod, Mr C. !•'., vibrator for ilie siphon recorder, 614 I'liillips, Mr Sanniel, sen., association with Mr Whitcliouse in first Atlantic cable and various exjieriincntal work, 46 I'hillips, Mrs. E.— partnership with Mr ('laiide Johnson, 160 cable machinery apparatus by, 161 I'liillips, Mr C. K. S., double-conduc tor < able by. 692 I'hotojjraphy, use of, su^jgested for recording; mirror sijjnals, 633 I'icard, Mons., system of transmission, 661 Fickerint4, .Mi Charles, supjiort to Atlantic, |H5,S, I able |)r(,ject, 31 I'ickinj; up - depth of water in which, attempted, 90, 109, IIJ7, 198, 410 drum for, 71 dynamometer used in, 42 failure of gear for Atlantic, 1865, cable, machinery — S..S. "Creat Kastern," 94 H.M.T..S. "Monarch," 196 sheave (or drum) for, 7 1 specific gravity, influence of. on. 408, 480 Toulon-Algiers cable, 67 I'olitical advantages, submarine telegraphy, 169, 170 " Pool " (or " joint-purse") arrangement — .Atlantic cable lines, 129, 130, r3i, 132, 136 Government lnilo-Euro|)e.in Telegraph Department, Indo-European Tele- graph Company, and " Eastern " Telegraph Company, 130 Great Northern Telegraph Company, and " Eastern Extension " Company, 130 " I'orcupine," H.M.S., Atlantic survey by (1S62), 80 Porthcurno, training school for ( able tele- graphists, log Post Office, H.M.— cable specification of, 490, Appendix III., Part II. conditions of contract for cable construc- tion for, 519 duplex telegraphy, 639 multiple-conductor cable adopted by, 401, 413 submarine cables under, 193 Pouyer-fjucrtier, Mons,, and Krench-.\tlantic (able, 131 Preece, Mr W. H.— cable imjirovements suggesteil by. r86 cable, nuiltiple-condiK tor, proposed by, for long-distance telephony, ^189, 690 core taping for multiple-conductor cables, 388 duplex telegraphy, 122, 635, 636 "Electrical Disturbances in .Submarine (."ables," on, 690 electro-static induction 7'. magnetic in- duction, (m, 578 engineer-in-chief and electrician to 1 1. M. Post Office, 193 indiK live telegraphy, experiments by, 186 lectures by, on iluplex telegraphy, 636 " Manual of Telephony," 208 Pacific cable, consulting engineer at Colonial Office conference (1896), 147 preservatives for sheathing wires, 422 signalling through space without wires, 701 .Society of Telegraph Engineers (Inst.E.E.\ early promotion of, 180 Presidential Address (1880) to, 183 telejihony, on, 202, 205 tests, telephonic , by, 203, 204 "The Maintenance and Durability of •Submarine Cables in Shallow Waters," 181 Toynbee Hall lectures, on telegraphy without wires, 189 telephone- telegraph evidence by, for Crown, 201 wireless telegraphy, 691 Preece and Sivewright, " Texi-liook of Tele- graphy," 582 Prescott, Mr C.eorge, ''Electricity and the Electric Telegraph." See Preface Pressure — atmospheric, 104, 273 effect on gutta-jiercha, 277, 331 gutta-percha applied under, 331 Chatterton's compound under, 315 tests on cables, 63, 64, 85 water, effect of, 104, 272, 273 water, and insulation resistance, 279 Price, Mr W. A.-- transmitting key by, 597 automatic sending apparatus, 673 Preedy, Captain (.'•. W., captain H.M.S. "Agamemnon," receives C.15., 49 w 733 INDl'A. I'iDich I aitoon on 1S50 Clianiicl line, 22 I'lipin, I'rofcbsor M. I., ( ondcnscrintcrpoliiicil for speed on sci lions of lonj,' < allies, 681 Q'c. I'ADKIU'LKX telegraphy, iX^o, (>6i Oi/in/i'r/y A'l'T'/tTi', '/'//(', telej,'iapli literature in, 184 R I ACOON," H.M.S., escort Atlantic catjle, 1866, expedition, 96 Rae, l)r John. North Atlantic ( able s( licme, 79 Raikes, Ri>;lii Hon. II. C, jubilee of tele- graphy ' i887\ 200 kanibaud-.MorbC relay, 586 Rankine, I'rof., stranded ( ondiu tor, 27, 28 Rawson, Mr Philip, 120 Rayleijjh, Lord, (lovernment telephone case, 201 Raymond- Harker. .Mr K. - cable leaks, .'S.' (able relays, 679 curbing, 551, 55^ signallinj; through cables. 543 manual translation swiic h, 627 suspended coil mirror, 595 Red .Sea ( ablcs, 57 Red Sea and Indian Telegraph Com|)an5' ■ formation of. 57 assistance by hritish (loNernnient to, 57 Reed, Sir K. J.. Fortnu^litly AVt'/Vtc, article by, 189 Reid, Mr Wni., sen., contractor, English Channel cable, 10 early land telegraphs, 24^ original type of cable suggested by, 1 1 pressure tank, 271 testing apparatus by, 63, 84 Relays (Morse system) and discharging coils-- Hrown-Allan, 118, 229, 579, 582, 587, 590 Coleman's, 587 D'.'Vrlincourt's, 582, 586 Farjou, 586 , Froment, 582 Lacoine's, 586 Relays (Morse systein) and discharging coils-- (W/ //////<•(/ mirror or siphon re< order, 679 polari^ed, Siemens', 68, 579, 580, 584, 588, 590, 591 |)<)larised, Stroll's, 582, 591 Rambaud's, 586 Willot, 586 Repair of cables, 105 in deep water, 109 Report of Joint Commission (i860) on Sub marine Cable Construction, 60 Resistance coils, 122 Resistance, electrical, staml.ird of, 63 Resistance, conductor alloys and ele( trical, 217 copper, 221 diameter of wire and. 232 I how governed, 232, 233 I increased by foreign substances in co|)|)er, 2 1 7 purity of material and, 82, 214, 2^,2. 2^3, 283 reduction of, means suggested for, i8fi signalling speed depending on, 232, 326, 537. ?''''''> 5'''7. 57''i. 577 temperature and, 224 tests, preliminary, and cakulations for, 222 22 ^ test for, after core niaiuifactiue, 324 Resistan( e, diclei tri( - ( onditions affecting, 268, 269. 283 cotton, insulating properties of, 244 current, electric, effect of, on, 546, 681 gutta-pen ha, of, 270 tests for, 28 r under pressure, atmospheric, 273 when submerged, and, 267, 275 increased l)y pressure, 271, 272, 275 moisture, and its effec :t on, 327 temperature, and, 273, 275 thickness of covering and, 273 india-rubber, specific of, '^'Sl low, and speed, 326 measurement of, 323 rec|uirenients, 326 Resistance, w.iter, used in signalling c ircuit, 5'H Retardation, 26 effect on electrical ])ulsations, 80, S45. 546 how jjioduced in telephone cable, 203, 688 Reuter's Agency, 107, 173, 175 Rhine cables, 251 i\|ii:\. 7ii Kitarcio, Mi John l.cwis, ( liiiirinati, Illeitric Telegraph Company, 241; Kirharils. Kcai-Adiniial Sird. H., 'I'elcjjrapli Coiislnic lion Company, icx; kicldlf, Mr lulwaril, l'"aliiioiilli-l.i-il)(in < al)le, ru4 Ki(;hli, Professor, nK)(lifi< ation nt lliTt/ radiator, (>')(> Kivers, suital)lc type of (able for, 14', Ko(ks frii lion of cable on, vfi'cit of, 57, y2 shore ends for rocky coa. I. 1 Kp, 143 Ronalds, .Sir Francis— insulatin); plan, 244 bei|uest to .Society of 'I'ele^raph Kn- ^ineers (Inst. K,E.\ liSo Kope for KrapplinR. construction of, 95 Rouillard, Mons., Queensland -New Caledonia cable, 140 Royal iiistitutioi., lekf^raphii papers read before, 184 Rue, Mr Warren l)e la, (io\ eminent tele- phone cpse, 201 Russell, Sir \V. H.— All.'intic cable expediiion, 9, 89, 97 " The Atlantic Telegraph," 89 Russell, >lr S<:ott, constructing "f S.S. " Cireai Eastern," 85 Russell. Mr Smart, " Kle( trie Light Cables,'' Rymer-Jones, Mr John, curb signal device, 55' cable leaks, 68,1 improved mirror speaker, 593-595 SAIUXK, Mr Robert- duplexing apparatus, 642 " Electric Telegraph, The," 52 "Electrical 'Cables and P'ormula" (Clark and Sabine), 493. See Preface first Atlantic cable, on, 52 pressure and resistance, 271 publication of Wheatstone's drawing for Dover-Calais cable, 3 velocity of electric waves, 526, 527 weight of iron wire in cable construction, 456 Wheatstone automatic transmitter, ex- jjcriments with, 663 Saha, early suggestion of submarine tele- graphy, I Saunders, .Mr II. A. C. - Atlantic cable, 1857-58, i8C)5-C)6, expedi- tions, 46, 89 curb signal dev i( p. 551 ( urb transmitler (automatic key), C173 double le\er keys, f)Oo lightning guard, 582 suggested c ore covering, 390 .Sauty. Mr C. V. dc Atlantic c;ible. 1857-58, i8'')5,e\|)editinns, ■\(\ 8c; duplex telegraphy, 123, 583, 642 Malta .MexanMria c able, 63 relays for mirror system, 679 .Saward, Mr ( leorge, secretary, Atlantic Tele- gjaph Company, }}, 79 .Schilling, e;iil>- investigations and experi- ments, I Siri/iihr'.'! .\/■ cable, 3'M< 3VS quality of, 398 quantity of, 3c;c;, 400 Serving, outer, 455 liright and Clark's compound, 45c;, 461, 464 canvas, method of apjjlying, 458-4C)o jute yarn applied externally, 468 lay in, 488 object of, 458, 465, 468 .Silvertown Company's method, 470 ta|)es and yarns for. relative merits of. 465 taping, 458, 460, 464 yarns and hemp cords in, 393, 466, 469, 471. 497 Serullas, Mons., on gutta-percha collection. 260 Shaffner, Colonel '1". P., proposals for North Atlantic cable sclieme, 79 734 iMii:x. .Shar|H'. Mr John Kobi'it, early f\|)criinL'iUs liy, for ■>iil)iiiarinc lelenrupliy, 2 Sheathing;. 3S0 abrasion, to wiihslaml, 404, 407, 410, 430 liesseniur steel uscti in, 404 brcakiiiK strain, f)0, 403. 404-407. 414, 4«2, 4«v -i')') l!rij,'ht's aluniiniinn 1 alik', 507 ilosc, 107, I iS (iee|)-si-a < allies, 41J, 430, 454. 471. 488 elongation of, wire, 414, 415 f^alvanisinK wire for, (j2, 407. 40.S, 42 1 K'aiiLje of wires, 452, 453 (iray anil Hawkins' taped wires for, 237, 4^5- 4^:7 lica\y laljles. 404 inner, 13, 4t 1 intcrniediate cable, 405, 406, 410, 413, 454 iron wire for, 66, 82, 403, 404, 419, 420, 445. 576. 577 Johnson and Phillijis' inipro\e(l nia- 1 hinery, 427, 44S "killing' process in wire f()r, 430 kinks in, wire, 430 lay, direction of, 430, 433, 450 length of, 451, 453 opposite for inner and outer, 450, 4S8 lij,dit cables, 1 r 1, 449, 494 marine >;rowths and animal life, effect on, 406, 410, 421 open ty|)e of, 489 ordinary (able, 403 overla|)i)ing wires, 452 oxide of zinc, test for, 407 packin)4 Ijetweeii, 41 1 picklinj^ process for wires, 424 preser\ative for wires in, 422 process of, 431 ipiality of wire for, 403 rij^idity of, 412 sea-water, and its effect upon, 421 shallow-water cables, 430 shore-end types, 76, 84, 93, 398, 404, 405, 406, 411, 412 skeleton-cylinder machine for, 434 spiral lay in, 430 specimens of, 454 speed of laying- wire, 433 steel, 407, 413, 488 straight wires for, 428-430 stretch of wire during, 418 .Sheathing— I (V/////«iv/ »up|)orl of wire, 391 taping separate, 331, 425-42';- 455 taping, outer, 460 tensile strain during, 404, 408, 413, 416, 431, 48 2, 484 testing wire for, 413-419 torsion test f, 345, 365. 394 .Sheathing of ( ables dis( ma< hinc, 442, 444 double sheathing, 434 hauling-off drum, 442, 472 improvements in, 448 machinery for, 427, 428, 431-433, 440, 441. 44^. 44'^ |)oinls of construction, 452 shore end, 447 multiple-core cable, 412, 6(;o .Shi|)s having sometime ;ing director, Tclc- ;^raph Con-itriK lion Company, 109 .Siemens' curb signal device, 551 Morse receiver, modillcation of, 6or plate lixlitninK mi.irds, 5SJ |)()l;irised relay, 68, 579, 582, 584, 588, 590, 591 recorder, permanent niaynet, 1 18 transmiltinK instrinnent, 141 Siemens, I)r Wcrner- '■ Contributions to the I'heory of Siib- nierjiin^ and Testing Submarine Telegra|)lis," 128 core-covering ma<]iine, 301 early experiments in sul)marine tele- graphy, 4, 251 continuity, experiments for, by, 21 duple.K telegraphy, 636 Ciovernment Committee of In(|uiry, evi- dence l)y, 59, 60 gutta-percha insulated wire, 4, 5. 156, 248, 250 Kiel harbour, early telegraphic ex|)eri- ments in, 4, 251 paying-out apparatus, on, 20 .Suez- Kurrachee cable expedition, ac- companies, 58 Siemens, Sir C. W. — breaking strain of cable materials, ex- periments by, 60 chairman, .Siemens Brothers and Co., 157 conductor, solid - strand, devised by, duplex telegraphy, 122 electrical standards and units, 61 Sientens, .Sir C. \V. tonliniicii electrical tests employed during the ( on- strui tion of the Malta and Alex- andria telegraph, and on insulating and protecting subinarinc < ables, 63, 181 " Faraday," T..S., designed by, 162 giitta-|)eri ha, introduc tion of. for in- sulation, 250 india-rubber, mac hine for covering tele- graph wires, 181 lead tubing for protecting core, 389 light c .ible, 498 paying out, 72 pressure, efl'ec t of, 271, 272 resistance thermometer, 27c; .Society of 'l'elegra|)h Kngineers (Inst. I'".. !•■..), part founder of, 180 I'residenti.il .Address ( 1 87 1 ,), 183 Siemens, .Mr Alexander- Director of .Siemens lirothers, 157 Royal Institution Lecture on Amazon River C.d)le, 128 .Siemens lirothers and Co., .Messrs, 157 Amazon River cable, 127, 388 .Anglo-Ccrman cables (18c/)), 489, 4CJ0 .Atlantic cables, 132, 136, 141, 154, 573 br.inc-hes of, 157 Mr Carl .Siemens, chairm.an of Comp.iny, '57 "Commercial," i8<;4, cable. 141,574, 575 Direct United States cable, 129, 230,232 duplexing, 659 gutt.i-percha c(>\ering machine, 316 Cireat Northern Company's Far Eastern cables, 1 14 india-rubber msulation, 346 india-rubber, machine for applying, 336, Indo-Kuropcan line, ill, 112 Jay Could cables, 132, 573 London- I'aris telephone line, 207 Mexican cables, 133 I'aris - New N'ork .Atlantic cable 11879), 131 pressure, testing system of, 85, 274, 321;, 330 permanent magnet relay. 632. 633 reput.ition of, 132 " Western and Brazilian.'' and other South .American cable systems, 127 Siemens and Halske, 156, 157 duplex telegraphy, 635, 636 gutta-percha insulation, early application of, by, in Prussia, 249, 250, 301 73(i IN1>K.\. Siemens and Ilalskc- iYV//////^iv/ Morse receiver, inociification of, h)\ 64 Oran-Carta;,'ena cable, iiianufacturers of, 68 .Suez-Kvirracliec cable, electricians of, 58 Signalling apparatus, 50, 141 Ader, recorder, 633 liriglu's Bells, 1 iS Bclz and lirahic's machine transmitter, 141 Cooke and Wlicitsione's, <>, 25, [43, 200, 2-1 + Crookes radiometer, 602 Delany's working-through system, (ijG Edison's carbon transmitter, 201 Edgar, improved si|)hon recorder, 617 Gauss and Weber, reflecting telegraph, 43 Hughes' printing ajjparatus, 586 Keys (mirror or siphon recorder system) and ordinary double -le\er transmitter, 597. 598 Dickenson's, 617, 628 Gray's, 597 Peeling and Davis'. C130 .Saunders', 600 I.auritzen's undulator. 1 iS. 631 Marconi's transmitter and receiver, 696, 698 Morse system, 581, 603 auxiliary discharging coil^ and re- lays for, 5S4, 585, 586 flag and lamp system, 77, 100 mirror receiver, 592, 593, 602. .See also '■ Mirror .System " Muirhead's improved siphon lecorder. Cii6, 617 direct writing recorder, 623 photography and its use for, 633 permanent magnet recorder, 621, 622 liunching, automatic (I)e;irlo\e'si, 6S0 Saunders, Mr H. A. C— - curb signal device, 557 curb transmitter, 673 double lever key, 600 suspended coil mirror, 595 Raymond- Barker's, 595, 627 Sullivan's galvanometer as a mirror speaker, 594 suspension piece, 616-619 Thomson's siphon recorder, 604-630. See "Sijjhon Recorder" translation (manual) switch or com- mutator — Benjamin Smith's, 625-627 Raymond- Barker's, 627 Signalling apparatus lontimicd. Wheatstone's receiver, 1 18, 631, 662 transmitter, 234. 551, 631. .See also "Transmission, .Automatic Ma- chine," " Transmission, Elec- tric al " Signalling through space, 186, 189, 695 Signals, siphon recorder, under \arying conditions, .Appendix, Part 111. Silver, conducli\ ity of, 214, 217 Silver, Messrs, and Co., 4, 157 Silvertown Company — cable covering characteristics of, 470 cables constructed by - •America, West Coast of, 1 30 .South, 139 Central and South American, 133 E.i.st .'.frican, 135 Marseilles-Algiers (1871), 119 Marseilles- Barcelona. 130 Mexican, 133 .Spanish National. 134 West Indian, 1 17 Wexford, 425 duiik'xing by, 659 india-rubber insulation, 336, 338, 346 position and work of the, 1 57 submarine survey system, 29 water resistance, 594 "Silvertown," T.S.. 161 Siphon recorder — advantages of, 604, 605 battery cells, 621 cable and land wires, u^e of, in c onnec- tion with, 677 clockwork, 61S coils, 607, 608, 639. 640 commutator, 620, 625-629 construe tion of, 606, 613, 614 cost of, 605 cradle, 610, 619 Cuttriss' modified, 61 5 description of, 6oc;, 610 drawing-off apparatus, 61 1 du|)lex work, with the, 639 electric mill, 612. 617, 622 electric motor system, 617, 61 8, 624 electro-magnetic, 607, 608, 620 French modifications, 608, 617, 622 gravity cells. 619 improvements of. 604 ink for, 610, 622 installation of, 619 inlerruptor, 6f8 Jacob's susjjcnsion piece, 619 INDEX. /J/ Siplion recorder — continued Kelvin's, Lord, invention, 105, 118,590, 604, C)o5 keys and switches, 625-630 moistine, etTect of, on, 614 Miiirhead's direct writing, 623 universal transmitter for the, 67S imjjroved, 616 paper strips, 61 1, 612, 622 permanent magnet, 621, 622 quadrupk'x telegraphy with the 124 record of signals, 60S resistances, 619-621 signals, under varying conditions. Ap- pendix, I'art III. speed of working, 57S, 579, 624 suspen-^ion piece f Muirhead's), 617-619 switch, manual translation — Henjamin .Smith's, 625-627 Raymond- Harker's, 627 vibrator for, 614-619 .\shs, 6 [6 Cuttriss', 61 5 Dickenson's, 616 Muirhead's, 617, 618 Pcscod's, 614, 615 .Siemens', 616 whip-cord used in, 611 White's pattern, 624 Sivewright (and Freece), "Tc\i-i!ook of Telegraphy," 582 .Smith, Mr IJenjamin — commutator or switch hy, 625 duplexing method, 1 24, 656 first .Atlantic cable, 1858, 46 \ manual translation system, 124, 626, 627 ; Smith, Mr Hu'knall, on "Wire," 419 Smith, .Mr John, part guarantor and pro- moter of .Anglo - .American Telegraph i Company, 91 Smith, .Mr Willoughby— Atlantic. 1865-66, cables, 89, 96, 97 • English Channel line, 1850, 10 " Chatterton's compound," 65, 237, 314 core capacity, on, 1 59 covering suggested by, 390 " Early Days of Electric Telegraphy, ' 6, 35 "The Rise and Extension of Submarine Telegraphy." .See Preface electro-static capacity of gutta-percha, 57« Ciovernment Commission on Submarine Telegraph Cables, 60 gutta-percha process, 109, 297, 572 Smith, Ml- Willoughby— (.('W/zV/wtv/ induction plates used by. 539 inducti\e telegraphy exjjeriments by, 186 insulation process and dielectric resist- ;mce, 327 joint testing method, 74, 394 joins Elliott Brothers, 161 light cables, 501 Malta - Alexandria cables (1861 .and 1868), 64, 107 Presidential .Address, Inst.E.E. (1884), l)y, 183 pressure test of core, 330, 331 sheathing wire, patent for preserving, 1 1, 424 speed of signalling, 573, 578 tanned hejnp or jute, introduction of, 74, 75. 392 teredo ravages, on, 383 test of recovered .Atlantic cable, 1865, 101, 102 working of long submarine cables, 182, 539 Smith, Mr W. C)., manager of Elliott Brothers, 161 Smith, Mr Willoughby S. - air-space core, 690 experiments in inductive telegraphy. 186 manager of the (Guttapercha Works, Telegraph Construction Company, 186 Snell, Mr C. Scott, cable defence scheme, 150 Societa I^irelli, cables by, 136 Societe du Cable Transatlanti(|ue Krani;ais, 107 " Societe en Commandite," 6 Societe Cieneralc dcs Telephones, 137 Society of Telegraph Engineers (Institution of Electrical Engineers) — founding of, 181 submarine telegraphy papers at, r8i Soldering, test for cfficiencv of. 364 Sommering, early experiments by, 1 Soundings - .Atlantic, 20, 28, 29, 39 Buchanan, Mr J. Y., on, 134 Pacific, by H.M.S. " Penguin," 147 .Stallibrass, Mr Edward, on. [84 West .African Coast, 134 Spagnoletti, Mr C. E.. Institution of Elec- trical Engineers, I'residential Address (.883), 183 ^3^^ INDEX. Specification, 1894, "Anglo" Atlantic cable, Appendix II., Part II., 514, ,[5 1891, Ani^lo-Clcrnian calile, .Appendix III., I'art U., 51^,-522 Speed- Brown-Allan relay, 591 by automatic machine transmitters, 674 calciiiation.s for, 570, 573, 575 definition of, 567, 368 •• KK ' Law, 206, 354, 566 Delany's transmitter and, 670 electrical and mechanical qualifications for, 25, 81, 106. 141, 221. 233, 566, 579, 666. 674 electro-static capacity of cable and. 232, 566, 567 increase of, by novel devices, 283, 681, 682 law for, 186. 203, 205, 206, 354, 566 length of words and, 567, 568 limit v-f, on long cables, 662 resistance (conductor) of cable and. 2^2, 567, 5''>8 solid-strand conductor and, 227 tables for, Clark and Forde'.s, 578, 579 Dearlove's, 578 Whitehousc, Mr E. C). W., cvpcrimcnts for, 26 Speed, data and examples Algiers- Tort X'endres lable, 68 .Atlantic, 1865, 82 Anglo-American, 1S94, Atl.intic, 141, 14^. 574 "Commercial,'" 1894. 141, 142 Malta-.Alexandria, 64, 107 French, 1869, Atlantic, 107, 556 Suez-Kurrachee, 58 "Sphinx," H.M.S., escort to .Atlantic i able ex))edition, 1865, 88 Splicing cables, 44, 45, 126. See also "jointing'' Stallibrass, .Mr Edward I ore co\ ering suggested by, 390 |)aper on " Deep-.Sea Soundings in con- nection with Submarine Tele- graphy," 182, 184 Queensland - Xew Caledonia cable, 140 Standards and units, electrical reports by British Assoc iation Conmiittee on, 61,62, 324, 325 Statham, Mr Samuel— Dover-Calais, 1851, cable, 12, 252 death of, 89 patent for a return wire, 21, 600, 6S5. .See Preface Statham, Mr .S.imuel — continued Statist^ T/n\ telegraph statistics, 177 statistics, mileage and financial, 153 Stearns, Mr J. H., du|)lex telegraphy. 121, 122, 583,638, 639, 655, (.:'. Steinheil — ' |)oint alphabet, 533, 603 Wafson, Dr, metallic circuit, adoption of, 21. See Preface Stephenson, Mr Robert, consulted on Malta- Alexandria cable, 62 (iovernment Commission on Construe tion of Submarine Telegraph Cables (i859\ 59 Stevenson, .Mr Charles, experiments in in- ductive telegraphy, 186 .Stewart, Mr Halfour, British Association Electrical Standards and Units Com- mittee, 61 Stewart, Colonel Patrick, Dircc tor-Cieneral of Indian Telegraphs, jt, .Stokes, .Sir Ci. tJ. — the velocity of electricity, on, 526 Stowage of cables, 476, 477, 478 tanks, 36 Stranding, advantages of, 27, 28 length of c:oils, 239 machinery, 236, 238 method of, 236, 239. See also "Cables"' and " .Sheathing " Stroh, Mr Augustus- polarised relay, 582, 591 W'hcatstone automatic transmitter, 663 Stubbs, Mr .A. J., " Manual of Telephony," 208 Submarine telegrajjhy advantages of, 22, 50, 167 liritish enterprise in, no, 167, 172 capital invested in, 153, 154 civilisation |)romoted by, 166 commercial influence of, 171, 172, 525 Danish enterprise in, if 5, 1 16 diplomac y influenced b\', 170 future of, 189, 685 French enterprise, 132, 115 H.M. Post Office, under, 193-208 investments in, 153, 154, 165, 496 improvements in speed, 168 international administration of, 177 international arbitration and, 170 journalistic ad\antages conferred b\', 1 6c;, 173, 174 judicial definition of telephone and tele- graph, 201 literature on, 181 INDEX. 739 Submarine telegraphy - conliinicd nuniljcr of persons employed in, 167 past and fiitmc, 189 political cftects of, 109 retrospect of, r45, 184 shares of companies, value of, 153 State control and acquisition, 193, 195 statistics, 177 societies and institutions interested in, iSi, 182 Sullivan, Mr H. W.— artificial cable leaks, 684 galvanometer, 594 Survey, Atlantic, by British C.overnment, 79 Silvcrtown Company's method of. See '■ Soundings " "Challenger" survey expeditions, 134, 184 "Sustiuehanna," I'.S. paddle frig.Ue, escorts first Atlantic cable expedition, 38 Switch (or commutator) for manual transla- tion — Benjamin .Smith's, 625-627 Raymond- Barker's, 627 Symbols, electrical, methods of. See Intro- duction. 1 at cable factories, 64, 85 cable ships. 36, 72, 76. 8fi. '^'-. '^'3. -?• on H.M.T.S. "Monarch.'' 199, 200 on 'I'.S. " Silvertown," 162 Taping, coie, 381 388 Bright's, Messrs, method of, 383 ClifTord's, Mr H., methotl of, 384, 385 early use of, 383 joints, 236 machine for, 386 Munt/ metal, 385, 388 multiple-conductor cable, 388 objections to, considered, 389 phosphor-bronze for, 385 present-day applications of. 385 protection to cable, 381 separate brass taping multiple core, 388, 578 Telegraph Construction Company s method. 386 Silvertown Company's method, 386 Taping iron sheathing wire, 425-429 Cray and Hawkins' patent, 425, 458 application of, by, 426, 427, 428 Johnson and I'hillips", 428, 429 Taping completed cable, 458-461 Johnson and I'hillips' patent canvas tape, 458 • application of, 460, 461 prejjaration of, 459 Tar, its use in cable construction, 2, 3, 74, 315, 352, 421, 423, 456, 459. 466 Tariff of charges for cablegrams, 143, 14.). 149, 168, 173' '75- 176- 178 Taylor, F. Alexander, on artificial leaks in cables, 684 Taylor, H. A. — "Anglo" Atlantic, 1894, cable, 489, 575 automatic transmitter, 141, 574, 666, 671 cable relays, 679 duplex telegrajihy, 1 23, 583 leaks (artificial) in cables. 682 partner, Messrs Clark, Forde, and Tay- lor. 156 Tebbets, Mr, promoter of New \'ork and Newfoundland Telegra])h Company, 26 Telegraph Act, [870, acquisition of land lines by State, 110, 193. See also "II.M. Post Office " Telegraph Construction and Maintenance Company adoption of Clifford's brass tape for core. 384 construction of cables for — "African Direct " system, 135 Atlantic (1865), 85 Atlantic (1866), 81, 82 Atlantic ([873-74), 128 Atlantic (1880), 128. 129. 424 Atlantic (1894), 141, 230, 575 Anglo- Mediterranean, 109 Black Sea, 121 Brest - St Pierre, 107 " British-Indian." 109 '' British-Indian Extension," 109 Brazilian Submarine system, 128 Lisbon- Madeira, 128 Chuy-Santos, 127 " Direct Spanish '' system, 1 19 " Eastern and South African " system, 131 " Europe and Azores'' system, 140 Malta-.Mexandria, 64, 107 Mauritius, 131 Pernambuco, 1 28 Porthcurno- Lisbon, 128 St \'incenl (Cai)e Verde Islands), 128 financial promotion of Atlantic scheme, 1866, 91 740 IXDKX. Telegraph Construction and Maintenance Company — cfliiliiiiieiL india-rubber insulation h\\ 346 lengths of (able laid by, 154 Mr Willoughby Smith, gutta-percha in- sulation metliod ado|)ted by, 297 I'cnder, Sir John, first cliairman of, 32 The rclei:;)(!phii Journal, 183 '[■(■lephony, 182, 201 i5russels and Berlin, 20S Buenos Ayres - Montevideo, 205, 206 carbon transmitter (Edison's), 201 cost of using, 207 conijiared with submarine telegraphy, 201, 204 " cross talk," 204 Felten and ( luilleaume's aiirial telephone cable, 590 ("ilasgow-Belfast line, 20S l.ondon-l'aris cable, 205, 207 capacity of, 207 cost of using, 207 instruments used for, 207 .. amber of messages, 208 long distance, 689 " Manual of Telephony,' I'reece and Stubbs, 208 ocean, 185 I'reece's (Mr \V. H.) proposed cable, 689, 690 tests applied to, 204 Temijerature, 104 effec t on gutta-percha. 273, 274, 279 insulation resistance of dielectric effected by, 224, 226, 279 method of calculating for resistame, 575 Temple, Mr John- Atlantic, 1865, cable expedition, 89 Atlantic, 1866, cable expedition, 97 recovery of 1865 cable, 99, 100 Teredo, damage to cables from attacks by, 118, 125, 381, 382, 389, 423, 500. See also " Fish " "Terrible," H.M.S., escort to Atlantic, 1865-66, cable expeditions, 88, 96 Tesia, Mr Xikola, on wireless telegraphy, 701 Tests and testing, electrical — conductivity, 76, 222, 234, 235 core, 323, 324, 327 " Electrical Testing,'" by Mr H. L. Webb, 184 gutta-percha, 327 insulation, 76, i-,, 323, 324 Tests and testing, electrical- contiiuifd joint, 74, 372, 375. 394 Malta-Alexandria cable, 63 Persian Culf cable, 85, 92, 329, 330, 331 pressure tests and, 85, 92. 329, 330, 331 records of, 326 resistance coils for, 65 Tests and testing, mechanical completed cable for lireaking strain, etc., 60, ■]■], 224, 484 Brown and Lenox apparatus for. 485. 487 Ciisborne. Forde. and Siemens' ap- paratus for, Oo, 63, 484 grappling ropes, 487 iron sheathing wire for tension, elonga- tion, torsion, etc.. 413. 420 Clark, Forde. and Taylor, and. 420 wire-testing machine. Carringlon's. 416 Denison's. 115. 416. 417 Kitchen's. 416 Thomas. Mons. H., "Traite de Telegraphic Klcctric|ue." Sec Introduction Thomson. Professor Sir William. See " Kelvin, Lord " Thomson, IJeut. A. S. See Preface Thompson. Professor Silvanus — cable proposed by. 183, 686 "Ocean Tele])hony." 685 Thompson. Sir Wyville. reports of the "Challenger Expedition.' 184 Times, Tlu\ newspaper— first English Channel cable, on, 9 early .\tlantic cable expeditions, on. 44. 46, 47, 48, 89 Timm, Mr Julius, automatic transmitter. 666 Tory Island cable. 312 Transmission, automatic machine — advantages of, 662, 674 application of. in practice. 674. 675 automatic curb sender (Jenkins). 557 ISelz-Braliic system. 141. 662 Cuttriss' device, 673 Uelany system, 574, 667, 670. 671 Muirhead and .Saunders'. 673 Muirhead's Universal, 678 Price's electrical contact apparatus, 597. Saunders'. 673 Stroh's perfected Whcatstone. 663 Taylor's automatic cable transmitter. 141, 574, 666, 671 Taylor and Dcarlove's. 671 '■\ INDEX. 741 Transmission, automatic macliine~cw////7«c leakage, effect of, on, 681 manipulation of instruments, 599 manual curb key, 55 1 mathematical calculations. 528, 530 metallic circuit, influence of, 2 1 propagation of an electrical impulse in a cylindrical conductor considered, 5^« mirror and, systems, 536 retardation of cable, etifect on, 545 curbing, eff'ect on, 541, 542 speed im|)ulse increased by condensers at both ends of cable. 547 condensers used in. 541 of signalling, 25, 566-575 shunting condensers. 539, 540 siphon recorder circuits. 539 siphon recorder signals, curljed and un- curbed, 552 alphabet, 533 station installation, 596 theory of, 525 Thomson's (Lord Kelvin) cur\eof arrival, 531 Transmission, electrical — contiiuiCii See " Signalling Apparatus,'' " Trans- mission, Automatic Machine," " Du- jjlex Telegraphy'' Transvaal, influence of submarine telegraphy on affairs in the, 174 Trinity liay. Telegraph House, 30, 56 Trott, Captain Samuel — cable repairs by, 501 light cable, 501 " Submarine Telegraph Cables, their Decay and Renewal," paper on, 503 wringing action of ordinary iron- sheathed c.ibles, on, 503 Trotter, Mr A. 1'.. on earth connections, 600 Truman. Mr Edwin — india-rubber dielectric by. 354 masticator machine by, 289, 290 process of, for core, 82 Tupper, Sir Charles, on Pacific cable project, 152 Twceddale, Marquis of (Lord Wdham Hay), first vice-chairman of Eastern Tele- graph Company, present chaiiman, 120 chairman of Pender Memorial. See Preface Tyndall, Professor, Government telejihone case, 201 , UNITED States and Newfoundland cable, 26 United States ("lovernment lend "Niagara" to nseist Atlantic cable expedition, y] United States telegraph companies and in- ternational administration. 179 United Telephone Comp.iny, 201, 202 V.VES, dujilex telegraphy, 122 Valentia Hay, landing place, Irish shore end, Atlantic cables, 30, 87 '•Valorous," 11. M.S.. pilot ship for Atlantic cable, 1858, 47 Van Uosc. temperature in copper conduc- tivity, 225 Van Kysselberghe's anti-induction system, 661 74^ INDKX. X'arley, Mr Cromwell Fleetwood — artificial line, 639, 658 Atlantic, 1865, cable, 50, 53, 85, 89 r866, „ 97 British Association Committee on Elec- trical Units and Standards, 6r condensers, 539, 540 duplexing by, 583, 655, 656, 658, 659 earth connections, 600 induction plates, 539, 540 insulation, imperfect, 231 joins Sir William Thomson as consult- ing electrician, 155 Joint - Committee (i860) on Submarine Telegraphs, assisted by, 53, 59, 60 lecture at the Royal Institution (1867) on the "Atlantic Telegraph,'' 536 light cables recommended by, 494 machine signalling apparatus, 612, 613 testing methods, 96, 122, 329 \'arley, Mr S. Alfred- artificial line for duplexing, 639 " Electrical Qualifications requisite in Long .Submarine Telegraph C.ibles," paper on, 81, 181, 537, 566 lightning protectors for cables, 697 speed of signalling, conditions for. 566 "The Practical Hearing of the Theory of Electricity in Submarine Tele- graphy," paper on, 566 \'ibratory theory discussed, 277 Visual telegraphy, 100 V'ivarez, Mons.,silicious bronze conductor,226 Vivian and Sons, Messrs, copper smelting process by, 220 Vogel, Sir Julius, Australia - New Zealand cable, 120 von Chauvin, Mr G., 1881, Jay Gould cables, 132 Vulcanised india-rubber, 158, 159, 3j(\ 339, 340 application of, to core, 341, 342 WALES, The Prince of- guest at Silver Jubilee of Eastern and Western cables, 166 messages from, to India and Colonies, 166 Walker, Mr C. V.— editor, Elcdriail Mai^aziiu', 183 English Channel cable, 5 Walker, Mr C. \ .—continued experimental line off Folkestone by, 5, 251 Society of Telegraph Engineers, part founder, 180 Presidential .Address (1875), 180 Walker, Mr F. P., \ ibrator for siphon re- corder by, 6 r 5 Wallich, Dr, on route for Atlantic cable, 71) War- code messages in time of, 175 dangers to submarine cables during, 171, 179, 187, 188 defence scheme for cables during, 150 possible interruptions by, 150, 179, 187, 188 Warren, Mr liruce, india-rubber core by, 345 Watson, Sir William. 21, 47. See Preface Weatlierall, Mr T. E., marine galvanometer, 594 Weaver, Mr Henry — manager, .-Vnglo - American Telegraph Company, 143 word rate system by, 144 Webb, Mr E. March, articles in Electrical Revieii.' concerning gutta-percha, 261 Webb, Mr F. C.-- Atlantic Telegraph Company, assistant engineer to, 36 buoying cable route, on, 7 Direct Spanish cable, 1 19 dynamometer fitted by, 70 gear for cable ships, design for, 16 Government Committee on .Submarine Telegraphs, 1859, evidence by, 59,60 lay, on designation of, 450 metal tube sheathing, patent for, 436 " Old Cable Stories Re-told," by, 3T, 58 Persian Gulf cable, 76 "The Practical Operations connected with Paying-out and Repairing Submarine Telegraph Cables," 181, 502 wire, method for finding length of single convolution of, 451 Webb, Mr F. H., secretary, Society of Tele- graph Engineers, 180 Webb, Mr Herbert Laws— " Electrical Testing," 184 literature by, 184 on Pacific cable project, 1 52 Webber, General C. E.— early promotion 01 Society of Telegraph Engineers, 180 Presidential Address (1884), 183 iM)i;x. 743 Webster niul Ilorsfall, Messrs, liomotjeneous iron wire by, 83 Weight of ciible, 7, 13, 14, 18, 21, 22, 28, a, 34, 50, 58, 62, 65, 73, 74, 76, 82, 83, 1 16. 142, 197, 231, 232, 402, 480, 481 West. Mr C. V.— early experiments in !^)rtsniouth Ilar- l)our, 4 india-iuijbcr insulation, 4, 335 proposed Dover-Calais cable Ijy, 4 West Indian cables, 116, 117 construction of, 1 17 difficulties, 118 " Western and lirazilian" cable?, 125, 582 duplex system on, 659 mirror instrument used by, 5S3 Wexford cable, 425 i Wheatstone, Sir Charles — Atlantic, 1865, cable, 80 automatic transmitter and speed, 141, 234. 55'- 631. (>(^^ British Association Klcctrical Standards and Units Committee, 61 cable proposed, 2, 3, 4, 245, 246 English Channel cable project, 2, 3, 4, 245, 246 experiments by, in Swansea r>ay, 3 Dover - Calais cable, proposals for, by, 2 Government Committee on Submarine Telegraphs, assistance by, 59, 60 multiple-core cable, 3 gutta-percha, early use of, by, 3, 4 insulation method, 2, 3, 4, 246 machinery, elevations, and section of cable by, 3 receiver and transmitter, 118, 631 single needle apparatus, 553 speed of electricd transmission, 25, 234, 526 submarine telegraphy and its practic- ability, 245, 246 Whitworth, Sir Joseph, consulted on Atlantic, 1865, cable, 80 Whitehouse, Mr Wildman— Atlantic, 1857-58, cable, experiments and work in connection with, by, 25, 26, 30, 46, 48 Atlantic Telegraph Company, electrician to, 32, 33 curbing signals, 538 intensity of electric currents, 52 tJovernment Committee (1859), evidence by, 59, 60 induction coils, 50 Whitehouse, Mr Wildman — continued Malta-Alexandria cable, 63 metallic circuit, patent for, 21, 600, 685. See Preface speed of signalling, 53, 537, 566 Whitewash for newly-manufactured cables, 75 White's direct - wi iting siphon recorder, 624 "Widgeon," H.M.S., assists ih laying first English Channel line, 7 Wilkins, Mr J. W., on inductive telegraphy, 186 Wilkins and Weatherly, Messrs, manufacture of English Channel cable (1850-51) com- menced by. 1 1 Wilkinson, Mr H. D., on " Submarine Cable Laying and Repairing,' 16, 195, 324. See Preface and Introduction "William Cory," S.S.Atlantic, 1866, cable, 97 Williamson, Professor, Electrical .Standards and Units (British .Association) Com- mittee, 61 "Willing Mind," S.S., Atlantic, 1858, cable 39 Willot, Morse relay, 586 Wilmot, MrT. J., automatic curb transmitter by, 141, 560, 672,673 Window, Mr F. R., paper on "Submarine Electric Telegraphs," 181 Winter, Mr (>. K., on quadruplcx telegraphy, 124, 660 Wire- galvanised, 12 gauge, 18, 21, 240. .Appendix I., Part II. homogeneous, 83 Kiiper's suggestion of, for cables, 1 1 sheathing, 18, 21, 27, 58, 82 solid and stranded, conductor, 227 Wire-rope, litigation by Newall and Co. as to patent for, 1 1 "Wireless" Telegraphy — Marconi's system, 1S9, 695 company formed to work. See In- troduction general review of, 700 general working of, 699 patent, 701. See Introduction principle of, 695 receiver, the, 697, 698 transmitter, the, 696 Wollaston, .Mr Charles, engineer. Submarine Telegraph Company, 6, 7, 11 744 INUKX. Woodhouse, Mr Henry — assistant engineer, Atlantic Telcj;rapli Conipan)'. 36 Molyliead-Kowtli cable, 13 Woods, Mr Nicholas- Atlantic cable cxpeditionP, '/'//(■ 7'iiin's' correspondent, 46 extravaganza bx', 89 Wool, use of, for insulation purposes, 351, 352 Word rate system, Mr Henry Weaver's, 144 Wortlcy. Rijilit Hon. James .Stuart chairman, Atlantic Telegraph Coni])any, So member of (iovernmcnt Committee, (1859) on .Submarine Telegra])hs, 59 honours declined by, 103 Wray, insulating composition, 353 Wright, Mr E. I'ayton, cable designed by, 498 Wright, .Messrs J. and E., serving for sheath- ing wire by, 66 Wiinschendorli', Mons. E. — See Title-page .Sec Preface Wiinschcndorff, Mons. Y..— continued. auvili.iry discharge coils, 586, 58S Dran cable, 1 39 author "Traitc de Telegraphie Sous- Marine," 69, 139. See Preface WykI, Mr, pro])osal b\', for North Atlantic cable route (i860), 79 YEAMAN, Mr C. H., " Electrical Instru- ments and Measurements." See In- troduction Young, Mr j. E., "Electrical Testing for Telegraph Engineers," 324, yi2. See Introduction ^'oung, Sir .Allen, North .Atlantic cable scheme (i860), 79 'ETSCHE, duplex telegraphy, 12: I'riiiled at THE Darien Press, Jiristo Place, Eiliiihur^h. mu .,a iXx^y cl; 1 UB.U* m 100-106 cjknm'M ' 97 BOil :iRVAM> & ELECTRICAL ^' CABL SiibmarSrut. Subterranean >!*•-■-; * DYNA^^OS ALL Ei TRlCAt ^A^US SILVERTOWM ifti>Oli, E. PERSAN-BEAWi^^'>WT. FHANCE. Tel: . Addresses: ■^?i;inl (;iit;inerr, A-.tnui' Tele lioiyliP.id Hontl- Woods, Mr Nicholii- A'.lantjc c;il)le expctliu I'orresijondcnt, 4^' i;i\aj(anra by, 89 \\ ,■ r.,.. ,,w J., 4.;. I ■ I .iivl' Word riiic iVh.iciii; Mi iu.r.ty \-. .avor -, ; i; Worttcy, Rit;hl Hon. James Stuait - tliairman, Atlantic Tdegraph Coiniui So ,,,cin' ' iivernmcnt Comniittci (i;-,c,c/> 1. 1, .'■itilimarme Teleyrapl' hotiouri declined by, 103 Wrav., insulatinjr composition, 353 Wright, Mr E. Fayton, cable designed by, 4*^' W liKht, Messrs J. and E., scr\ ing for sheath inji vvirp by, f)(> Wunschcndortf. Mons. E.— Ser Titlc-pagc 'V " Elecu . r.nib Kii Printed AD VEK TISRMF.NTS. Cfjc ):ntiux l\ublTci\ battel |JtrdjiT, antr Ctlcgvaplj 9,9.tarlis Compana ittr. HEAD OFFiCESt 100-106 CANNON STREET, LONDON. 97 BOULEVARD SEBA8TOPOL, PARIS. ELECTRICAL ENGINEERS. CABLES Submarine, Subterranean, and Aerial. DYNAMOS INSTRUMENTS, BATTERIES, AND ALL ELECTRICAL APPARATUS. WORKS t SILVERTOWN, LONDON, E. PERSAN-BEAUMONT, FRANCE. Telegraphic Addresses : "CRAYSILYER," LONDON. "INDIA-RUBBER," PERSAN. ,U)V/:/iT/sr,.\f/:xTS. SIEMENS BROTHERS & CO. LIMITED, Electrical and Telegraph Engineers. SUBMARINE, SUBFLUVIAL, SUBTERRANEAN, AND AERIAL CABLES, IRON POSTS, INSULATORS, INSTRUMENTS, BATTERIES, And all Appurtenances for Telegraph and Cable Stations. Seven out of the Eleven Living Atlantic Cables were made and laid by Siemens Brothers & Co. Limited. ELECTRIC LIGHTING AND TRANSMISSION OF POWER, DYNAMOS, MOTORS, ALTERNATORS, ELECTRIC RAILWAYS AND TRAMWAYS, CENTRAL STATIONS. Head Office--12 QUEEN ANNE'S GATE, LONDON, S.W. BRANCHES: 21 GRAINGER STREET WEST, NEWCASTLE-ON-TYNE. 261 WEST GEORGE STREET, GLASGOW. 65 PITT STREET, SYDNEY, N.S.W. 46 and 48 MARKET STREET, MELBOURNE. Works— WOOLWICH, KENT. Cable Address— "SIEMENS, LONDON. Codes— "A.B.C,' •■Al,' ■Engineering," "MOREING & IVI'CUTCHEON. .7 1) I El^ TISEMENTS, 111 SOME SUBMARINE TELEGRAPH CABLES I^ci]:iufa.ctti]:*e ctll PuK'poses. SUBMARINE TELEGRAPH CABLE. Gutta-Percha Insulated with Double Sheathing of Round Galvan- ised Wires. PATENT TELEPHONF CABLE, With Paper and Air Space Insulation, Capacity 0.065 IVlicrofarad per Mile, for Submarine use, sheathed with Flat or Locked Wires. For Electric Lighting and Transmis- sion of Power. PATENT FLEXIBLE HICH PRESSURE WATER PIPE For Overhead, Underground, and Submarine Use. Supplied in any lengths in one piece on Reels similar to Cables. The only high pressure flexible Pipe in long lengths thus far produced Tested for pressure up to 50 atmospheres. Indispensable for conveying Steam or Water over long dis tances where Pipes \ cannot be laid, or only 'with great difficulty, heavy cost and loss of time, crossing rivers, marshes, and connect ing Isles and Light houses with the shore. Sole Amenta €ov the United Kingdom W. F. DENNIS & CO., 23 Billiter Street, LONDON, E.G. AD VERTISEMENTS. PIGKING-UP AND PAYING-OUT GEAR, AND COMPLETE OUTFITS A*'^ CABLE SHIPS, /4?^«' As fitted on SS. MONARCH, SS. JOHN PENDER, S.S. VIKING, SS. GREAT NORTHERN, SS. CHILTERN, SS. ELECTRA, SS. RETRIEVER, SS. MAGNETA, S.S. DUCHESS OF MARLBOROUGH, SS. RECORDER, SS. SHERARD OSBORN, SS. RELAY, SS. GRAPPLER, S.S. CITA DE MILANO, S.S. OKINAWA WARU, S.S. TUTANEKAI, S.S. CONTRE AIVIIRAL CAUBET. VI . / /> / EN TISIIMENTS. ADVERTISEMENTS. vit Telegraphic Address-" MUIRHEADS, LONDON." MUIRHEAD & CO., Electrical Engineers & Manufacturers nf Electrical Apparatus. SPECIALITIES. CONDENSERS. STAIMRD CONDENSERS (with Dr Muirhead's Certificate of Value). STANDARD CELLS (Dr Muirhead's Patent Portable Eorm, as supplied to the Board of Trade). PORTABLE TESTIN& SETS (for Electric Light Engineers). SUSPENDED COIL CtALVANOMETERS (Taylor, Ayrton-Mather, Deprez-d' Arson val, and other Forms), TESTIN& KEYS, RESISTANCE COILS, KELVIN and VARLEY'S SLIDES (Muirhead's Portable Form and other Forms). &ALVANOMETERS, ELECTROMETERS, VOLTMETERS, and AMMETERS (Recorder Coil with Muirhead's Double Spiral Directive Force, and other Forms), and other Apparatus required for Electrical Testing. MANUFACTURERS OF The well-known "WESTMINSTER DYNAMO," MOTORS, ARC LAMPS, SWITCHBOARDS, TWITCHES, ELECTRIC LIGHT FITTINGS, &c. &c, ELECTRICAL MEASURING INSTRUMENTS of every description, PATENT AMMETERS, VOLTMETERS, WATTMETERS, k. COMBINED OIL OR GAS ENGINE AND DYNAMO for the Lighting of Telegraph Stations, LAND-LINE MATERIAL. Muiiliead Cciinpound Wrought- Iron I'olcs. Insulators. Ii'on and Copptr W'uw Insulated Wires, iS;c, TELEPHONE MATERIAL. I'oles and Fittings for House-tops, Switchboards, and (!omi)lLle Fittings lur ■J'ele|)honL' l-'xchnngt's. i.oud-t.TJking TLl(,'i)honcs, liattcries for Tran^niitlcrs, JMrc Alarm System wilii Telephones. SUBMARINE TELEGRAPH APPARATUS. Condensers. Siphon Kerorders (1 )r Muirhiad's l'(irm), Apparatus lur I)uple\ I'llegraphy on C!al)lcs with I )r Muir- head's laiisi impni\emenls, .\utoniatir (!url) 'I'ransmitters, iVe. LIGHTNING GUARDS. Lodge's, lor Cable Stations and I'llectric Light Stations; Saunders', lor Cable Stations : Hright's, fur Cable .Stations. STORES FOR SUBMARINE CABLE SHIPS. -Siallibrass' Sounding lubes; Stallibrass' Improved Centipede Cii,i[)nel. biinlers' Tools, Hrigiil's junction l!o.\es for Cables. \e. \;(', CENTRAL STATIONS AND PRIVATE INSTALLATIONS Designed and l''ittL'd 11]) complete ; Houses and Shi|)s Wired; Dr iio])kinson's I'atcnt .Automatic Kegul.iting Switclies. CONTRACTORS FOR THE LAYING OF ELECTRIC LIGHT MAINS. Ofrices-54 OLD BROAD STREET, LONDON, EX. Works— ELMERS END, KENT (adjoining S.E. Railway Station) viii .•/ /; / ER r I Ml. MEN IS. THE ELECTRIC CONSTRUCTION COMPANY LIMITED, BUSHBURY, WOLVERHAMPTON. Manufacturers of all Descriptions of ELECTRICAL PLANT, DYNAMOS, MOTORS, ALTERNATORS. TRANSFORMERS, SWITCHBOARDS, METERS, ARC LAMPS, &c. Contractors for CENTRAL STATION EQUIPMENT FOR PUBLIC & PRIVATE LIGHTING, ELECTRICAL RAILWAYS AND TRAMWAYS EQUIPMENT, ELECTRO DEPOSITION & POWER TRANSMISSION. List of some Electric Traction and Lighting Contracts carried out by the Electric Construction Company Limited. TRACTION. Blackpool Tramways; Birmingham Central Tramways; South Stafford- shire Tramways ; Liverpool Overhead Railway . Madras Tramways ; Hartlepools Tramways ; Halifax Tramways ; Isle of Man Tramways, &c. &c. TOWN ligh:ting. Bath; Chelsea District, London; Durban, South Africa: Johannesburg. South Africa : Halifax ; Manchester ; Morley ; Oxford ; Shoreditch Vestry, London ; Wolverhampton, &c. &c. 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