a vi RS ae a yi mn hes peuid he bh eis Tri i te Sh i dshee iw in Mead 5) it» fa) ane bia i ; ' y of te a eras ha rn ie in Piet: sp i Baga | eerie ant TCO ‘Boil ft i Ca! ~~ SMITHSONIAN SCIENTIFIC SERIES Editor-in-chief CHARLES GREELEY ABBOT, D.Sc. Secretary of the Smithsonian Institution BOX Published by SMITHSONIAN INSTITUTION SERIES, Inc. EW YORK GREAT INVENTIONS By CHARLES GREELEY Agport, D.Sc. Secretary of the Smithsonian Institution SMTHSOMAR MAY 12 1988 wi TAKIED VOLUME TWELVE OF THE SMITHSONIAN SCIENTIFIC SERIES 1932 ay} a3esysnqjI 07 poredaid Aypersadsa ss9M saqyyd asay yz “3Se] YORPG PY? PUB ISIG Moyad oy} YIM BuIZIE3S JIpsJO dy} UI JaYyIO 9y} UO dUO SuuTIdur ss0Jaq WO; aaissoisoid UI UONVUIIOF U9dIOS puv IOTOS DAIS SUOT}IIS Ja]JVUIS IYO dy} SvaroYyM ‘sIOTOO TTe UT pagutd ‘uoIdas pessvyus aja]duro9 94} 03 sjutod Mose ayy, *pasie[ue uoijs0d 94} ST 9iInsopsua ai1enbs yovry]q 94} ul UOI}I9S ouL “ssao0id sTyy jo UuOIJeULIOJ UI9IOS pue dn-oyew JOJ[OD dy} MOYSs 0} pesivyus Apvois useq Sey YSIYM UOIJIaS B Surhvsz40d ‘uol¥sjsnqI ssad0id Jojoo-inoy VW yIoX Mon ‘Auvdwoy Suravisuy svwWOoIyIT, 2YL Aq ssadoid CopyYRIGHT 1932, BY SMITHSONIAN INSTITUTION SERIES, Inc. [Printed in the United States of America] All rights reserved Copyright Under the Articles of the Copyright Convention of the Pan-American Republics and the United States, August 11, 1910 FOREWORD WITH THIS VOLUME the Smithsonian Scientific Series is completed. It has cost more of effort on the part of the Smithsonian Institution than was anticipated. An exact- ing standard of accuracy and interest in text and illustra- tions has required more time than was expected for the preparation of the books. It is my hope that the quality of the finished product may be found to justify the long delay in completion. As Secretary of the Smithsonian Institution, I wish to thank the subscribers for the interest which they have evinced in its work and welfare. As a direct result of this interest, a large sum has already been added through royalties from sales of the Series, to the resources of the Institution, for the furtherance of its scientific investi- gations. As Editor-in-Chief, I wish to thank the authors, editors, and collaborators for their painstaking efforts to maintain the high quality of the Series. I wish also to compliment the publishers, the Smithsonian Institution Series, Inc., for steadily clinging to a high ideal of excellence in the make-up and printing of the books. They may justly have pride in the beautiful examples of bookmaking which have resulted. C. G. Anron, Secretary fyi Ay PREFACE PRIMITIVE inventions such as the means of producing fire, the awl, the wheel, water craft, and others, which enabled man to outdistance the beasts, have already been covered in Volume 7 of this Series. Many authors of popular books, moreover, have dealt with great inventions his- torically, tracing in general terms the gradual perfecting of devices from inventor to inventor, but with little at- tempt to explain in detail the methods of operation. Several considerations have given a different scope to this volume. With the realization that there would be no room to explain their operations if all the inventions that might claim to be great were even mentioned, the number chosen here had to be sharply limited. Generally, too, to save space, neither have the first rudiments been traced nor the latest refinements fully explained. My purpose was rather to select and explain the operation in their simpler forms of a few inventions, conceived mainly in the nine- teenth and twentieth centuries, which have had the very greatest influence on our present lives. Most of the ma- chines considered may be examined as actual specimens or models in the United States National Museum. Many il- lustrations given are from that source, but in addition Iam deeply indebted to several of the great manufacturing or- ganizations for illustrative photographs, as will appear in the acknowledgments of the individual plates. In the New Hampshire farmhouse of my boyhood, our rooms were all freezing cold in winter except the kitchen and at times the sitting-room, when the great fireplace had a roaring open fire in it. Upstairs there was a library of books left by my great-uncle, who was an inventor. It PREFACE was my delight on a Saturday holiday from school to steal away into the arctic upstairs room and pore over a drab- covered book now in my library called “Elements of Technology,” being a course of lectures by Jacob Bigelow, M.D., Rumford Professor in Harvard University, Boston, 1829. On the opening page it was shown how the great pyramid of Gizeh overtopped not only St. Paul’s in Lon- don and the tower of Strassburg Cathedral, but even St. Peter’s at Rome. The things in that book which fasci- nated my young mind were the descriptions of the watch and the clock, including an account of how the clock strikes, and particularly the description of the double- acting condensing steam engine of Watt and the mysteries of its valve mechanisms. To trace out the operation of such things I was willing to shiver with cold for hours. It is with the belief that boys’ natures have not changed since I was a boy that this book is prepared. They have not reached the antiquarian stage where they care par- ticularly about the man responsible for an invention, but they do want to know how a thing works. Heroes, though very imposing to them, are few and far between, and it takes a Lindbergh of action rather than a Watt of inven- tion to be a hero in their sight. Therefore, I have dwelt little on the history of invention, but have tried to explain without forbidding technicality the operating principles of simpler types of the most important electrical and mechan- ical devices, showing by lettered diagrams and descriptions how they work. In some instances I have quoted classical original sources such as the writings of Faraday and Henry to give a vivid sense of being at the fountain head. The book is not, however, for experts. Every invention de- scribed here has many whole volumes written about it that the expert may consult. This sketch is only for those who would like to get just a little better understanding of how such things as radio differ from out-and-out miracles. CONTENTS PIONEERING IN ELECTRICITY Dynamos anp Morors ELEcTRONS AND X Rays TELEGRAPHY AND TELEPHONY Rapio TRANSMISSION . Tue Evectric LicHt Prime Movers d MECHANICAL TRANSPORTATION . HovusEHOLD AND Farm INVENTIONS OUTSTANDING MANUFACTURED PRODUCTS . THE GrapuHic ARTS INDEX oi 5 , ye ‘ ee bradlarnt' 47a hy a aoe int aoe r F ; » Peo ce 2 ee ae dg hal 9 U eal gate 4 ae ae ant 19. be ee ee oo oo ROR Pe See OOTP Sl Sa gee ILLUSTRATIONS LIST OF PLATES Four-color process illustration, ponies progressive steps in printing. et of Nera. Frontispiece Hans Christian Oersted . UAT Gs: oi f 4 Sir Humphrey Davy 5 Michael Faraday 8 Joseph Henry 9 Iron filings and lines of force ‘ 20 Field structure of direct-current mill motor . 21 Laminated field pole, armature, and shaft for ducer cureent machines 24 Direct-current motor 2 Dr. Elihu Thomson . 28 Original Thomson three- phase dynamo 29 George Westinghouse ; 36 Core and coils of a three-phase ‘transformer ; Go) Alternating-current generator . 40 Rotating field of alternator 41 Disassembled direct-current and alternating- ment Wa 44 Alexanderson high-frequency dynamo ; 46 Washington electric pumping plant 47 Modern Coolidge X-ray tube 64 X-ray picture of human head and neck 65 Henry’s Yale magnet and electromagnetic oscillating motor 72 Samuel F. B. Morse . : Semmes) Model of Morse’s sending device and first Morse message : 8a The printing telegraph sender . shy 88 Cyrus W. Field ; 89 H.M.S. Agamemnon laying the Atlantic cable in 1858 ’ 94 The 1866 cable fleet, including the Great Eastern 95 Paying-out machinery on the Great Eastern . 96 Atlantic cables of 1858, 1865, and 1866 97 Sir William Thomson (Lord Kelvin) . 98 Alexander Graham Bell wine 99 Bell’s original telephone and box telephone . Box telephone and hand telephone receiver of 1877 Working model illustrating the modern telephone Interior of a telephone exchange of $a General Electric Pliotron vacuum tube Guglielmo Marconi . Radio transmitting station, Lawrenceville, N. 1 One of the Lawrenceville radio station buildings Cape Spencer Light Station, Alaska Thomas A. Edison Edison’s basic lamp, and incandescent electric lamps of 1931 Edison Jumbo dynamo . Avie The Brush and Thomson- Houston arc ‘lamp supports Impulse water turbine ; Niagara Falls. Runner for 70,¢ 000 h. p. turbine Niagara Falls. Butterfly valve to control water flow . Niagara Falls. 70,000 h.p. turbine runner ‘ Niagara Falls. Castings being assembled to form wheel casing ; ‘ Niagara Falls. Sectional view of 70,000 h.p. turbine Niagara Falls. Interior of Schoelkopf station Conowingo power and distributing station James Watt George H. Corliss zee Ne spe Allis-Chalmers steam turbine. Parsons type First gas engine built in America, 1878 Dr. N. A. Otto b RAL SOns Liberty airplane engine . Packard-Diesel airplane engine. Fitch’s steamboat of 1787 and Fulton’s Clermont of 1807 Brazilian native balsa SU hes Coane Rs Bcd Why Full-rigged merchant ship . The Leviathan leaving New York . The locomotive Best Friend The locomotive YFohn Bull . : Early and modern passenger locomotives Heavy-duty locomotives James J. Hill . Edward H. Harriman First Duryea automobile First Haynes automobile Balzer motor wagon . Henry Ford . Wilbur and Orville Wright . Samuel P. Langley 104 105 TORS III 120 128 129 132 133 140 168 172 173 176 177 184 185 188 189 192 193 200 201 208 209 216 217 220 221 224 225 Langley model No. 5 at rest and in flight . . Manly radial engine, and Langley’s full-scale airplane Wilbur Wright at Rome Wright machine of 1908. First ‘airplane bought by any government . The Langley gold medal for aerodromics Aerial view of Langley Field, Va. N.A.C.A. propeller research tunnel N.A.C.A. full-scale wind tunnel N.A.C.A. seaplane channel Model of seaplane boat being tested . N.A.C.A. variable-density wind tunnel . Lockheed Sirius low-wing monoplane Consolidated Fleetster high-wing monoplane Douglas YO-31 high-gull-wing observation monoplane Pitcairn-Cierva autogiro Electrolux domestic absorption refrigerator General Electric domestic compression refrigerator Original Howe and Singer sewing machines : Original Wilson and modern Singer sewing machines Imitation of East African weaving, and Jacquard loom Ordinary spinning wheel, and Paddleford’s ring spinner . Ring spinning room, Amoskeag factory, Manchester, N. H. Worsted weaving room, Amoskeag factory, Manchester, Eli Whitney McCormick reaper of 1845, Modern harvester . Modern harvester-thresher Gardening by power The farm tractor The caterpillar tractor at work Machines for paper making : The ending of the paper-making process Native tapping a rubber tree . Charles Goodyear . . , Rubber gloves made by dipping ; Differences between refractories in withstanding hot glass action . Shake: Incandescent light bulb machine . View of a blast furnace plant . A Bessemer converter in action Vertical section of Wellman producer gas plant Charging side of an open-hearth furnace steel plant White-hot steel ingot being drawn from the soaking pit . 117. 118. 11g. 120. 121, 122, 123. Le A ee ee oe oe ee oo BSP PO BOT Ea Yb wv = O im) i?) W& [=| XO) A oe) 2 ae) Oo eo Cae he PYPYPYPHND OOS SON eal 2 . White-hot steel ingot being rolled in the slabbing mill Andrew Carnegie : AEA Nee NR PE The Knight and the Lansquenet. Woodcut by Albrecht Durer, 1479 «| EPO Mie ea George Eastman : : Modern method of film manufacturing : Assembling kodak shutters Pulp beater at kodak plant LIST OF TEXT FIGURES How electric current deflects magnet Zweigger’s improved galvanometer Faraday’s galvanometer : Magnetism produced by electricity 2 Faraday’s iron ring experiment Faraday’s dynamo . ‘ : Electric current and magnetic ‘polarity 5 Diagram of the Pacinotti-Gramme dynamo Alternating- and direct-current dynamo diagram Fluctuation of current in dynamo windings The electric repulsion principle Experiment illustrating electric repulsion A step-up transformer Three-phase alternating current diagram Electric discharge in high vacuum J. J. Thomson’s discovery of the electron Cathode temperature, voltage, and thermionic current strength Satay : Dushman’s “kenotron” rectifier . Cooper Hewitt mercury rectifier . Henry’s electromagnetic telegraph Morse code alphabet and later changes . : Diagram of Morse sending and receiving instruments Duplex telegraph diagram A code-punched paper ribbon : Cable operation through electric condenser . Diagram from Bell’s telephone patent Diagram from Bell’s telephone patent Carrier and modulated radio waves . Discontinuous radio wave A discontinuous-wave radio set A regenerative oscillating radio circuit Babcock and Wilcox tubular boiler . : Diagram of simple reciprocating steam engine . S50 Diagrams of various steam turbines Sectional view of a vertical gas engine Sectional view of the Stromberg carburetor . Radiobeacons guiding the pe to New York N.A.C.A. cowling The variable-density wind tunnel . The simplest of looms Spinning with distaff and plummet Penelope’s web. a Illustrating the heddle rod . A simple tapestry loom . A primitive Indian or African loom Diagram of the essentials of a plain loom Sketch of the plain English loom . Front and back designs of satin cloth Diagram of a simple draw loom The drawboy’s fork . The mechanical drawboy Front elevation of a Jacquard machine Sectional views of a Jacquard machine Detail of a Jacquard machine . Further details of a Jacquard machine Cylinder and cards for a Jacquard machine . Cross-sectional diagram of a cotton gin Restoration of McCormick reaper of 1834 Raw materials and products of the blast furnace Diagram of shape and chemistry of the blast furnace Diagram of the Bessemer converter 167 173 177 IgI 235 237 266 268 270 272 273 276 277 279 281 283 288 289 292 293 294 295 297 393 304 339 349 343 ns FOR Py, rk oieeey fee so bh Ge em i, re Nd a: CaS KE RRMA Wee) iyi sinha igh leh ht Hanate Milyy Pe ase ags Tea et i 7 | bo Rt oie AH Fy dak iL yeAcas be Petal | | ‘ : Ah Vecre yr eae | x ts. math Se Ai gle a\bk CHAPTER I PIONEERING IN ELECTRICITY One hundred years ago, in the year 1831, Michael Faraday at the Royal Institution in London, and Joseph Henry in Albany, N. Y., independently discovered that electricity can be generated from magnetism. Ten years before that a Frenchman, Arago, and an Englishman, Sir Humphrey Davy, had discovered independently that an electric cur- rent circulating around a bar of iron converts the bar into a magnet. A year before that, in 1819, Oersted in Den- mark had discovered that a bar magnet, free to turn, tends to set itself at right angles to a nearby wire carrying elec- tric current. From these discoveries come directly the dynamo and motor, the telegraph and telephone, and in- directly the electric light, radio, and almost all the appli- ances for the household, the office, the workshop, the mov- ing vehicle, or the hospital, wherein electricity nowadays serves us. Oersted, Arago, Davy, Faraday, and Henry were all interesting personalities, apart from their pioneer- ing discoveries. Hans Christian Oersted (1777-1851) was the son of an apothecary at Rudjébing on the island of Langeland. School facilities were of the scantiest. The barber taught a little German to Hans and his brother Anders, and the barber’s wife helped them to learn to read and write. As the barber knew no more of arithmetic than how to add and subtract, a school-boy friend of somewhat more ad- pa] GREAT INVENTIONS vantages added multiplication and division. The baker helped the boys to learn to draw, and the burgomaster gave them a bit of French. Finally the local surveyor added a little more mathematics. At 12 years of age Hans began to assist his father, the apothecary, and so learned a little of chemistry. Yet the boys made the most of this patchwork of educa- tion, and in 1794 both entered the University of Copen- hagen. Anders became a jurist. At that time the bent of Hans was toward literature and philosophy, and in 1797 he won the University gold medal with his essay, “On the Limits of Poetry and Prose.” His doctor’s thesis was entitled “The Architectonics of Natural Metaphysics,” a subject which would require to be “‘chewed and digested” even in the title. But the invention of the electric pile by Volta in 1800, and opportunities that came to him for foreign travel and the meeting with philosophers of Ger- many, Italy, and France, turned Oersted’s attention more and more to physics. For many years he sought to discover the intimate con- nection, which many philosophers felt must exist, be- tween electricity and magnetism. But in spite of this general expectation, Oersted’s paper, “Experimenta circum Effectum Conflictus electrici in Acum magneticum,” pub- lished in 1820, in which he announced that the electric current “exercises determined and similar impressions on the direction of a magnetic needle” near it, was so abso- lutely the first hint of certainty that, says Forbes, “There was not even, so far as I am aware, a suspicion that he had been, however remotely or dimly, anticipated.” So great was the enthusiasm over this discovery that Oersted was awarded the prize of the French Institute and the Copley medal of the Royal Society of London, and he was elected a knight of the order of Danebrog. He wrote much to popularize science. A selection of his writings entitled “The Spirit in Nature” (“Der Geist in der Natur’) was published in 1850. [2] PIONEERING IN ELECTRICITY Dominique Francois Jean Arago (1786-1853) came of an able family, and received good educational training. After attending the Ecole Polytechnique, instead of entering the army, as intended, he became secretary of the Paris Observatory, where he enjoyed association with the great Laplace. He was sent in 1806 with Biot to make geodetic observations in Spain and remained to complete the work after Biot returned to Paris. Napoleon Bonaparte’s in- vasion of Spain at this time threw Arago into great danger. Making his escape toward Algiers from the Balearic Islands, he was captured by a Spanish privateer and im- prisoned in Spain for three months. Being released by Spain at the demand of the Dey of Algiers, he spent six months in Africa before returning to Marseilles. Succeeding Lalande at the age of 23 as professor of analytical geometry at the Ecole Polytechnique, Arago became an astronomer at the Paris Observatory, and in 1830 its director, and in the same year perpetual secretary of the Academy of Sciences. Besides his greatness as a scientist, he served with distinction in the French Cham- ber of Deputies, and in 1848 became Minister of War and Marine in the Provisional Government. In this capacity he abolished flogging in the French navy and slavery in the French colonies. The counter-revolution succeeding, he resigned his post as astronomer in 1852, but Prince Louis Napoleon refused to accept his resignation. The other three great electrical discoverers were self- made, selfeducated men. Sir Humphrey Davy (1778- 1829) was the son of a wood carver at Penzance in Corn- wall. After a grammar-school education and reading with a clergyman, he was apprenticed to a surgeon. At 20 years of age he received an appointment as a laboratory assistant in Doctor Beddoes’ “‘Pneumatic Institution.” In 1800 his first scientific papers attracted so much favorable notice that in 1801 he was chosen to lecture at the Royal Institution. He became professor of chemistry there in 1802 and director in 1805. In 1807 came his great dis- [3] GREAT INVENTIONS covery of the nature of the fixed alkalies, which he suc- ceeded in decomposing by aid of the electric current. This gave him great scientific distinction. He was knighted in 1812, and made a baronet in 1818. For seven successive years, 1820 to 1827, he was elected president of the Royal Society of London, but resigned in 1827 on account of failing health. It is difficult to say whether Sir Humphrey Davy made a greater discovery in the nature of the fixed alkalies, or when, in 1812, by the brilliance of his lectures, he attracted the attention of the young genius, Michael Faraday, and later took him under his patronage. Michael Faraday (1791-1867) was the son of a black- smith, and at the age of 13 years he was apprenticed to a bookbinder and stationer. So in 1804 he began to carry around a daily news sheet to the subscribers, just about as newsboys do now, except that, having only the one copy, he had to wait at each place until it was read. Later he learned to bind books, and the handling of books gave him his opportunity for a self-made education. He acknowl- edged particular delight in Mrs. Marcet’s ‘““Conversations in Chemistry.” His attention was directed toward elec- tricity by the article in an encyclopaedia which he was employed to bind. Thus he prepared himself for his great opportunity which came at the age of 21. A friend who knew his inter- ests invited him to hear a course of lectures by Sir Humphrey Davy at the Royal Institution. Faraday took notes of a set of four lectures on chemistry, carefully wrote and bound them, and sending them to Sir Hum- phrey, so greatly interested him that when the laboratory servant was dismissed for cause a little later, he engaged Faraday as assistant at 25 shillings a week with lodgings at the Institution. Thus Faraday began his career of experi- menting under the inspiring guidance of one of the greatest chemists of the age. Indeed, an experimental physicist should always begin as a chemist. The care which he learns in making quantitative analyses with fragile ap- [4] TI] fodvorys ‘Arasnpuy puv sduaI9g Jo UINasny, pfeMuasoy ay} WO “pajssoQ UBISIIYD suLEy sae my pi a ms a i = é PLATE 2 Sir Humphrey Davy. From a print published by Agnen and Zanetti PIONEERING IN ELECTRICITY paratus gives his mind and hand a training ever useful in physical observations. In 1813 Sir Humphrey and Lady Davy began a grand tour of Europe, and Faraday was taken in the combined functions of assistant, secretary, and valet to Sir Hum- phrey. They traveled, of course, by carriage, loaded with apparatus and papers. Sir Humphrey was well known and highly honored by the Continental scientists. Thus it came about that Faraday saw the latest discoveries and met the great men of France, Switzerland, and Italy, of whom he afterwards became a valued scientific peer. On his return to the Royal Institution, Faraday’s gifts as an experimenter and lecturer became more and more apparent; so much so, indeed, that even the great Sir Humphrey Davy may have felt at times some jealousy of his brilliant colleague. In 1829 Faraday succeeded to the directorship of the Royal Institution on the death of Davy. In 1831 he made his epoch-making discovery that elec- tricity can be generated from magnetism. From that time until his death in 1867 he conducted many thousands of keen and fertile experiments on all sorts of subjects in physics and chemistry. His fame as a lecturer was so extraordinary that his lecture courses were thronged, the audiences including even royalty itself. It is conceded by the most eminent of scientific men that next to Sir Isaac Newton, Faraday was the greatest exponent of physical science that England ever produced. Joseph Henry (1799-1878) was born of Scotch ancestry in Albany, N. Y. His father died when the boy was but g years old, and his schooling was interrupted at 13 to apprentice him to a watchmaker. Although always of an ingenious, mechanical turn, Joseph Henry did not remain long at watchmaking and for a time was rather an idle boy. He had a considerable leaning toward the theater. At 16, however, he read Rev. George Gregory’s ““Lectures on Experimental Philosophy, Astronomy, and Chemistry, [5] GREAT INVENTIONS intended chiefly for the use of Young Persons.” Henry wrote, many years after, on one of its blank leaves: This book, although by no means a profound work, has, under Providence, exerted a remarkable influence on my life. It accidentally fell into my hands when I was about sixteen years old, and was the first book I ever read with attention. It opened to me a new world of thought and enjoyment; invested things before almost unnoticed with the highest interest; fixed my mind on the study of nature, and caused me to resolve at the time of reading it that I would immediately com- mence to devote my life to the acquisition of knowledge. The remarkable influence which single scientific books written for young persons exercised in the lives of Faraday and Henry may well encourage scientific men to attempt popular exposition. Awakened to greater interests, Henry resumed his education at Albany Academy with a view to practicing medicine, but in 1826 he accepted the post of teacher of mathematics and philosophy there. Pioneering electrical and magnetic experiments which he made at Albany led to his appointment in 1832 to the chair of natural phil- osophy at Princeton University. Becoming a recognized national and international figure in science, he was elected in 1846 first Secretary of the Smithsonian Institution. The following resolution of the Board of Regents indi- cates the standing which Henry had in the minds of lead- ing men of that time. Resolved, that it is essential, for the advancement of the proper interests of the trust, that the Secretary of the Smithsonian Institution be a man possessing weight of character, and a high grade of talent; and that it is further desirable that he possess eminent scientific and general acquirements; that he be a man capable of advancing science and promoting letters by original research and effort, well qualified to act as a respected channel of communication between the institution and scientific and literary individuals and societies in this and foreign countries; and, in a word, a man worthy to represent before the world of science and of letters the institution over which this Board presides. Joseph Henry deserves a place in the front rank of emi- nent Americans. His work in electricity, though notable, was not his greatest service to his country or the world. [6] PIONEERING IN ELECTRICITY As the first Secretary of the Smithsonian Institution he framed the policies which have made of it, next to the Republic itself, perhaps the greatest contribution made by America to world culture during the nineteenth cen- tury. Henry’s liberal free distribution of Smithsonian in- formation and publications; his establishment of the ny! Fic. 1. How electric current deflects a magnet. Effect first used by Zweigger for the galvanometer, a measurer of the strength of the electric current International Exchange Service, for the exchange of scien- tific literature, now made perpetual by treaties between approximately 20 nations; his collection and preservation in the United States National Museum of American fauna, flora, and ethnological data; his establishment of a na- tional weather service; his outstanding part in the organi- zation and promotion of scientific societies—these, and other measures which he took, so greatly stimulated Amer- ican science, and so closely cemented the friendly relations between the cultures of the new world and the old, that it would be difficult to give him too high a place among great Americans. Oersted’s discovery enabled all investigators of electric currents to measure, and measurement is the soul of all scientific and technical progress. Figures 1 and 2 show [7] GREAT INVENTIONS how Zweigger used Oersted’s wire and magnet to make the galvanometer, or electric current measurer.' In Figure 1 we have the simplest type, where a straight wire lies north and south under the axis of a magnetic needle suspended by a pivot. The magnet, of course, naturally points in the direction S N toward the magnetic pole of the earth. But when an electric current flows, it is deflected through an angle to a position S’N’ until the current force is balanced by the magnetic force of the earth. If the current is re- versed the needle will take up a reversed position. It occurred to Zweigger that the current force could be doubled by bringing the wire back above the magnet as Fic. 2. Zweigger’s improved galvanometer in Figure 2, for the current in the upper branch would tend to deflect the magnet in the same sense as that in the lower branch. From this it was easy to see that the cur- rent force could be still further increased by completing several loops enclosing the magnetic needle. Still greater sensitiveness of the galvanometer came about by reducing the directing force of the earth’s magnetism. This was ac- complished by attaching a second magnetic needle, with its poles reversed to those of the first, a little lower and parallel to the first. It thus became the “‘astatic” gal- vanometer used by scientists for many years. Let Faraday 1 Named after Galvani, the Italian of the eighteenth century who studied the phys- ological actions of electric currents. [8] PLATE 3 Michael Faraday. Discoverer of magneto-electricity PLATE 4 Joseph Henry. Discoverer of electric self-induction. First Secretary, Smithsonian Institution PIONEERING IN ELECTRICITY tell in his own words? how he constructed his galvanometer as illustrated in Figure 3. Possibly some of my young readers will wish to try Faraday’s experiments with the simple apparatus he describes. The galvanometer was roughly made, yet sufficiently delicate in its indications. The wire was of copper covered with silk, and made sixteen or eighteen convolutions. Two sewing-needles were magnetized and fixed on to a stem of dried grass parallel to each other, but in opposite directions, and about half an inch apart; this system was sus- Fic. 3. Faraday’s galvanometer pended by a fibre of unspun silk, so that the lower needle should be between the convolutions of the multiplier, and the upper above them. The latter was by much the most powerful magnet, and gave terrestrial direction to the whole; [Fig. 3] represents the direction of the wire and of the needles when the instrument was placed in the magnetic meridian: the ends of the wires are marked A and B for convenient reference hereafter. The letters S and N designate the south and north ends of the needle when affected merely by terrestrial magnetism; the end N is therefore the marked pole. The whole instrument was protected by a glass Jar. The experiments of Arago and of Davy amount to this, that whenever a magnetic metal such as iron, steel, nickel, 2 The quotations below are from Faraday’s ‘Experimental Researches in Electricity,” vol. 1, Bernard Quaritch, publisher, London, 1839. [9] GREAT INVENTIONS or cobalt finds itself in the proximity of an electric current, magnetism is produced in the metal, either temporarily, during the continuance of the inducing current, or perma- nently if the metal is capable of permanent magnetization. Beyond this result, moreover, they proved that a coil of nonmagnetic wire, while carrying an electric current, ac- quires the properties of a magnet even though containing Fic. 4. Magnetism produced by electricity and the enhancement of the effect by means of soft iron no magnetic metal. But the strength of such a magnetic coil is enormously enhanced by inserting therein a bar of soft iron (Fig. 4). If electric currents can produce magnetism, may not magnetism produce electric currents? This was the ques- tion which many scientists asked from 1820 to 1830, and Faraday tried several experiments unsuccessfully during that decade for the purpose of demonstrating that mag- netism can produce electricity. The experiments of Henry by which he demonstrated that electricity could be produced through magnetism, though perhaps a little earlier than Faraday’s in the mak- ing, were not published until later, and were by no means so extensive as Faraday’s. The latter conducted a bril- liant and thorough campaign to establish the relation beyond doubt, and to clear up every puzzling detail. His first inkling of the truth seems to have come from an ex- periment described in paragraph 10 of his work. He is led to suspect a temporary electrical effect, positive so long as the magnetic force is increasing, negative while it is de- [10] PIONEERING IN, ELECTRICITY creasing, and zero when it is constant. He therefore con- ducts the following train of experiments leading up to the famous experiment of the ring, performed August 29, 1831. The results which I had by this time obtained with magnets led me to believe that the battery current through one wire, did, in reality, induce a similiar current through the other wire, but that it continued for an instant only, and partook more of the nature of the electrical wave passed through from the shock of a common Leyden jar than of the current from a voltaic battery, and therefore might magnetise a steel needle, although it scarcely affected the galvanometer. This expectation was confirmed; for on substituting a small hollow helix, formed round a glass tube, for the galvanometer, introducing a steel needle, making contact as before between the battery and the inducing wire, and then removing the needle before the battery contact was broken, it was found magnetised. When the battery contact was first made, then an unmagnetised needle introduced into the small indicating helix, and lastly the battery contact broken, the needle was found magnetised to an equal degree apparently as before; but the poles were of the contrary kind. In the preceding experiments the wires were placed near to each other, and the contact of the inducing one with the battery made when the inductive effect was required; but as the particular action might be supposed to be exerted only at the moments of making and breaking contact, the induction was produced in another way. Several feet of copper wire were stretched in wide zigzag forms, representing the letter W, on one surface of a broad board; a second wire was stretched in precisely similar forms on a second board, so that when brought near the first, the wires should everywhere touch, except that a sheet of thick paper was interposed. One of these wires was connected with the galvanomenter, and the other with a voltaic battery. The first wire was then moved towards the second, and as it approached, the needle was deflected. Being then removed, the needle was deflected in the opposite direction. By first making the wires approach and then recede, simultaneously with the vibrations of the needle, the latter soon be- came very extensive; but when the wires ceased to move from or towards each other, the galvanometer-needle soon came to its usual position. As the wires approximated, the induced current was in the contrary direction to the inducing current. As the wires receded, the induced current was in the same direction as the inducing current. When the wires remained stationary, there was no induced current. [11] GREAT INVENTIONS A welded ring was made of soft round bar-iron, the metal being seven eighths of an inch in thickness, and the ring six inches in external diameter. Three helices were put round one part of this ring, each containing about twenty-four feet of copper wire one twentieth of an inch thick; they were insulated from the iron and each other, and superposed in the manner before described, occupying about nine inches in length upon the ring. They could be used separately or Fic. 5. Faraday’s iron ring experiment, whereby he first pro- duced electricity by magnetism conjointly; the group may be distinguished by the letter A [Fig. 5]. On the other part of the ring about sixty feet of similar copper wire in two pieces were applied in the same manner, forming a helix B, which had the same common direction with the helices of A, but being separated from it at each extremity by about half an inch of the un- covered iron. The helix B was connected by copper wires with a galvanometer three feet from the ring. The helices of A were connected end to end so as to form one common helix, the extremities of which were con- nected with a battery of ten pairs of plates four inches square. The galvanometer was immediately affected, and to a degree far beyond what has been described when with a battery of tenfold power helices without iron were used; but though the contact was continued, the effect was not permanent, for the needle soon came to rest in its natural position, as if quite indifferent to the attached electro-magnetic arrangement. Upon breaking the contact with the battery, the needle [12] ee eR me ~ im en a PIONEERING IN ELECTRICITY was again powerfully deflected, but in the contrary direction to that induced in the first instance. When the battery contact was made in one direction, the galvan- ometer-needle was deflected on the one side; if made in the other direction, the deflection was on the other side. The deflection on breaking the battery contact was always the reverse of that produced by completing it. The deflection on making a battery contact always indicated an induced current in the opposite direction to that from the battery; but on breaking the contact the deflection indicated an in- duced current in the same direction as that of the battery. No making or breaking of the contact at B side, or in any part of the galvanometer circuit, produced any effect at the galvanometer. No continuance of the battery current caused any deflection of the galvanometer-needle. As the above results are common to all these experiments, and to similar ones with ordinary magnets to be hereafter detailed, they need not be again particularly described. We must pass over the numerous confirmatory, though searching, tests by which Faraday, like a master experi- menter, set aside every other hypothesis than the true one, and we will pass on to his explanation of a highly impor- tant observation of Arago’s, in the course of which Faraday made the first dynamo ever invented. If a plate of copper be revolved close to a magnetic needle, or magnet, suspended in such a way that the latter may rotate in a plane parallel to that of the former, the magnet tends to follow the motion of the plate; or if the magnet be revolved, the plate tends to follow its motion; and the effect is so powerful, that magnets or plates of many pounds weight may be thus carried round. If the magnet and plate be at rest relative to each other, not the slightest effect, attractive or repulsive, or of any kind, can be observed between them. This is the phenomenon discovered by M. Arago; and he states that the effect takes place not only with all metals, but with solids, liquids, and even gases, i.e. with all substances. Upon obtaining electricity from magnets by the means already described, I hoped to make the experiment of M. Arago a new source of electricity; and did not despair, by reference to terrestrial magneto- electric induction, of being able to construct a new electrical machine, .).) 2% The magnet has been already described. To concentrate the poles, [13] GREAT INVENTIONS and bring them nearer to each other, two iron or steel bars, each about six or seven inches long, one inch wide, and half an inch thick, were put across the poles as in [Fig. 6] and being supported by twine from slipping, could be placed as near to or far from each other as was FCOMMTEE GS i) oe sis A disc of copper, twelve inches in diameter, and about one fifth of an inch in thickness, fixed upon a brass axis, was mounted in frames so as to allow of revolution . + , its edge being at the same time introduced more or less between the magne- tic poles [Fig. 6]. The edge of the plate was well amal- gamated for the purpose of obtaining a good but move- able contact, and a part round the axis was also prepared in a similar manner. Conductors orelectric col- lectors of copper and lead were constructed so as to come in contact with the edge of the copper disc. .. . Copper wires, one sixteenth of an inch in thickness, at- tached, in the ordinary man- Fic. 6. Faraday’s dynamo. The _ ner, by convolutions to the first continuous-current machine for other ends of these con- producing electricity from magnetism ductors, passed away to the and motion galvanometer. All these arrangements being made, the copper disc was adjusted as in [Fig. 6], the small magnetic poles being about half an inch apart, and the edge of the plate inserted about half their width between them. One of the galvanometer wires was passed twice or thrice loosely round the brass axis of the plate, and the other attached to a conductor, which itself was retained by the hand in contact with the amalgamated edge of the disc at the part immediately between the magnetic poles. Under these circumstances all was quiescent, and the galvanometer exhibited no effect. But the instant the plate moved, the galvanometer was influenced, and by revolving the plate quickly the needle could be deflected 90° or more. . . . . Afterwards, when the experiments were made more care- [14] PIONEERING IN ELECTRICITY fully, a permanent deflection of the needle of nearly 45° could be sustained. Here, therefore, was demonstrated the production of a permanent current of electricity by ordinary magnets. When the motion of the disc was reversed, every other circumstance remaining the same, the galvanometer needle was deflected with equal power as before; but the deflection was on the opposite side, and the current of electricity evolved, therefore, the reverse of the former. The relation of the current of electricity produced, to the magnetic pole, to the direction of rotation of the plate, &c. &c., may be expressed by saying, that when the un- marked pole is beneath the edge of the plate, and the latter revolves horizontally, screw-fashion, the electricity which can be collected at the edge of the plate nearest to the pole is positive. As the pole of the earth may men- tally be considered the un- marked pole, this relation of the rotation, the pole, and the electricity evolved, is not difficult to remember. Or if, in [Fig. 7] the circle represent the copper disc revolving in the direction of the arrows, and a the outline of the un- marked pole placed beneath Fic. 7. Electric current and mag- the plate, then the electricity netic polarity and direction of collected at 6 and the neigh- motion bouring parts is positive, whilst that collected at the centre ¢ and other parts is negative. The substance of these experiments of Faraday’s is to prove that whenever a conductor of electricity is sub- jected to an increase or decrease of magnetic force, whether by generating a magnet where none had been before; by destroying a magnet which had previously existed; by moving a magnet to or from a conductor; or finally by moving a conductor to or from a magnet—in all these cases electricity is produced in the conductor. The current [15] GREAT INVENTIONS lasts only so long as a change of magnetic force is going on, and reverses when the change of force of magnetism alters from waxing to waning. Faraday went on to prove what everybody now knows, that the effects produced by friction of fur on glass, by heating a junction of two metals, by dropping copper and zinc plates into acid, or by bringing up a magnet toward a conductor, are due to the same agency—ELECTRICITY. We have now rehearsed the fundamental investigations necessary and sufficient to anticipate the invention of the electric dynamo and motor. In the next chapter we shall trace some of the high lights in the development of these wonderful machines. [ 16 ] CHAPTER II DYNAMOS AND MOTORS THE discovery of Faraday proved to be the most fruitful of modern times. It opened possibilities as wonderful as Aladdin’s lamp. Previously the sources of electricity— frictional, thermal, and chemical—had been so puny that such a thing as the continuous electric generation of a single horsepower for the industries would have been a fantastic dream. But now emerged the germs of a method whereby any amount of mechanical power might be trans- formed into electricity, and in that state could be trans- ported by wires for long distances and then retransformed into whatever form of energy might be desired. In our own time even wires may sometimes be eliminated, and distant effects are produced by wireless and unseen agencies. Nothing but the efficacy attributed to prayer by men in all countries and all ages can compare in wonder- fulness with this great discovery. It is startling to reflect how many of our most ordinary appliances depend on the magnetic production of elec- tricity. Without it not only would the street car again be horse-drawn, but the automobile and the airplane would stop. For without electromagnetic sparking devices, how could gasoline engines function? The electric light would, of course, disappear, and with it the greatest guarantee of safety after twilight in the great cities. The telephone and telegraph would be idle, and the daily newspaper would therefore become of merely local interest. Wars might continue long after peace had been declared, as indeed happened in America, where the bloody battle of [17] GREAT INVENTIONS New Orleans occurred January 8, 1815, two weeks after the treaty of peace with Great Britain was signed at Ghent. Radiotelegraphy, telephony, and broadcasting would all disappear. Power plants would have to be as- sociated with every separate factory, because long-distance transmission of power would cease. The rivers could furnish power only to factories situated on their banks. Such metals as aluminum, and all chemicals that require electrical separations, would become rarities, and their prices would soar accordingly. Hospital practice would again be without X-ray appliances, and households would be without electric work-lightening devices. Ships in dis- tress at sea, no longer able to signal their S O S calls and no longer provided with gyrocompass, radio direction finders, or fire-signaling apparatus, would often sink, as formerly, with none to rescue or help. THE Dynamo Although no one in 1831 could have foreseen the enor- mous development of electromagnetism attained in our time, inventors were keenly alive to the opportunity af- forded by Faraday’s discovery. Electromagnetic inven- tions quickly multiplied. Pixii, in 1831, by rotating a permanent horseshoe magnet beneath a pair of fixed coils, wound upon bobbins, produced alternating electric cur- rents. At the suggestion of Ampére, the great French physicist, for whom the unit of electric current was after- wards named, Pixii introduced what we now call the com- mutator. He thus constructed his direct-current magnetic machine of 1832. Except for Faraday’s direct-current disk, shown in Figure 6, Pixii’s is believed to be the earliest continuously acting electromagnetic current generator. Without detailing the gradual improvements in the art, let us pass to the next great step, which was the substitu- tion of an electrically excited field magnet of soft iron in place of the permanent magnets of Pixii and Faraday. Such an electromagnet, separately excited, was intro- [18] DYNAMOS AND MOTORS duced by Page in 1838, but in 1848 Jacob Brett passed the direct current developed by his machine itself around his soft-iron field magnet. As yet, however, it was considered necessary to temporarily excite the field electromagnet from an independent source before the current of the machine itself should be formed. The coil system that we now call the armature had by this time advanced from a device of only two coils to one of many coils, an increase which, like the many cylinders of a fine automobile, tends to steady the output and diminish its fluctuations. It had been known for many years that more powerful permanent magnets could be produced from a given weight of metal if the metal were divided into many laminae, rather than concentrated into a single bar. But it was for quite another reason that Pulvermacher, in 1847, intro- duced the practice of laminating the iron frame on which the coils of the armature were by that date customarily being wound. For he perceived that the alternate waxing and waning of the electric current in each coil of the arma- ture tends to set up induced currents in every piece of metal nearby and especially in the metal of the armature frame itself. This not only wastes energy by producing heat, but these induced waste or eddy currents, by their secondary induction effects, hinder the full production of the coil currents themselves. Hence Pulvermacher’s im- provement, which checked the circulation of eddy currents, marked a great step forward in raising the efficiency of the dynamo-electric machine. It was not until 1867 that Wilde, Siemens, and Wheat- stone discovered independently that it is unnecessary to use auxiliary current to preliminarily excite the field magnet of a direct-current dynamo. The slight residual magnetism remaining, even in the softest iron, added to that induced by the earth’s field, is sufficient to start a feeble current as soon as the armature rotates, which rapidly augments the magnetization of the field. Several types of windings of the armature had by this [19] GREAT INVENTIONS time been devised. Possibly one of the easiest to under- stand is the ring armature type of Pacinotti (1860), used also in the Gramme and other dynamos but now generally abandoned. In the diagram, Figure 8, we shall for the sake of simplicity consider the field to be produced by a permanent horseshoe magnet. Between the poles N and S ji. iN Ge f vip Whija\inn' i . Fig. 8. Diagram of the Pacinotti-Gramme dynamo rotates the armature E’, E, E”. The ring is made of a bundle of soft-iron wires, wound with many groups of turns of insulated copper wire. All the turns are con- nected in series so as to make a continuous coil around the whole circumference of the ring. From each junction of two coils there passes radially a bar of copper to the com- mutator, C, which comprises a split tube of copper bars, separated from each other by nonconducting material, such as hard rubber. The outer surface of this com- pounded commutator tube is turned true, so that the two brushes B B’ may press steadily upon it as it rotates and draw off from it the direct current. Faraday conceived of magnets and electrically conduct- ing wires as possessing fields made up of “lines of force” spreading into the surrounding medium. These were very real to him. The conception was given mathematical and quantitative standing by Clerk Maxwell, the great mathe- matical physicist who invented that electromagnetic theory of light from which sprang our radio. The hun- dredth anniversary of Clerk Maxwell’s birth was cele- [20] PLATE mn Tron filings and lines of force. Upper: Iron filings above a horseshoe magnet. Lower: Iron filings above a short-circuited horseshoe magnet PLATE 6 Field structure of direct-current mill motor, 14 pole, 2,5 tesy of the General Electric Company 00 h.p. Cour- DYNAMOS AND MOTORS brated in October, 1931, at the University of Cambridge, immediately after the Faraday Centenary celebration at London, and was attended by many of the world’s greatest scientific men. We shall understand more clearly the action of the dynamo by adopting in our thinking the Faraday-Maxwell lines of force. Plate 5, upper, shows a photograph of fine iron filings strewed to cover thinly a plate of glass above the poles of a horseshoe magnet. This illustration shows the course of the lines of equal force as they pass from pole to pole of the magnet. It may also be shown, though less strikingly, by means of iron filings strewed on a glass plate lying at right angles to an electrically conducting wire which pierces the plate, that the lines of force form rings around the electric current. Plate 5, lower, similarly pre- pared with iron filings on glass, shows how the magnetic lines of force are altered and practically all gathered up by a soft-iron ring like the armature of Pacinotti between the poles of a horseshoe magnet. Iron, soft steel, nickel, and cobalt all possess in different degrees this property of con- centrating magnetic lines of force and stealing them away from the air, known as high magnetic permeability. The degree of concentration of a magnetic field, or in other words, its intensity, is customarily indicated as “the num- ber of lines of force per unit area.” Whenever a closed loop of electrical conductor cuts through lines of force, electric current is set up in the loop. The intensity of the current is proportional to the number of lines of force cut per second. In order to take properly into account the direction as well as the intensity of such a current, both plus and minus signs are used in electro- magnetic induction formulae. If in a coil moving at a cer- tain rate in a certain magnetic field there is induced a current C, then the coil will carry the current —C if turned to present its opposite face and again moved through the magnetic field in exactly the same manner as at first. Consider the loop shown in Figure 9 mounted so as to [21] GREAT INVENTIONS rotate on the axis XY in a uniform magnetic field indi- cated by the parallel arrows. Suppose this magnetic field to extend indefinitely above and below the plane of the paper, where the axis at the loop is shown lying. Let us now follow the current strength developed in the loop as it rotates through a complete turn of 360° starting from Fic. 9. Upper: Alternating-current dynamo dia- gram. Lower: Direct-current dynamo diagram the point N as o®. It is clear that the ends of the loop cut no magnetic lines, and merely serve to complete the cir- cuit. The two sides cut lines equally, but in opposite senses so that the current in the two sides tends to flow oppositely, as it must do to flow at all around a loop. Let the uniform angular velocity per second be represented by 9; let the uniform magnetic field be represented by / lines per unit area of cross section, and let the radius of the loop be represented by 7. [22] DYNAMOS AND MOTORS It is clear that the side 4 is cutting lines at the rate +r/ 6 as it passes the position 0°, and the side B is cutting at the rate —r f 6 at the same instant. The rate of cutting lines becomes zero for both sides at go°, and —rf@and-+rf6at 180°. To readers with a slight knowledge of trigonometry it will be plain that in any instant the side 4 is cutting Fic. ro. Fluctuation of current in alternating- and direct- current dynamo windings magnetic lines of force at the rate rf 6 cos y, and the side B at the rate —rf 6 cos ~, where g is the angle reached from o° at the instant in question. Hence the total current in the loop is proportional to 2rf6cos p at any instant whatever. In Figure 10 we see how the current waxes and wanes as the loop revolves. The curve shown there is a pure cosine curve, or, as it is more commonly called, a pure sine curve. From 270° to go° the current is positive, and from go° to 270° it is negative. Suppose now two rings, D and E£, are connected to the two ends of the loop shown in Figure g and that conduct- ing brushes, # and G, are provided to connect to an ex- ternal circuit, /HG. Thecurrent at H will then alternate in direction and strength as represented in Figure Io. Next, instead of using the two continuous rings, F and G, let there be substituted the two separated half-rings, I and J, Figure 9. Then while the current is positive, as shown in Figure 10, from 270° to go°, the brushes, J and J, will act exactly as did the brushes F and G, before. But in the other half of the rotation, where the current in the loop is reversed, brush J takes the place of brush G, and [ 23] GREAT INVENTIONS brush J takes the place of brush F. Thus the current is reversed in the outer circuit, also. Just as two negatives make one affirmative, the negative half of the cycle be- comes positive in the outside circuit, as shown by the dotted line in Figure 10. In this way the alternating cur- rent becomes always direct, though violently fluctuating in its strength. This defect is reduced by multiplying coils in the armature to make up a complete cylinder and cor- respondingly multiplying the commutator segments. Multiple poles in the magnetic field are also usual in large modern direct-current dynamos. It would lead to wasteful diffusion of the lines of force to allow them to stream quite across a dynamo several feet in diameter. Several or many poles are located around just outside the circumference of the armature, and arranged with alter- nately north and south polarity. The lines of force pursue a scalloped course from pole to pole through the armature, and each pole piece includes two sets of lines of force. Wire and electrical resistance are saved in multipolar dynamos by forming the armature coils tangentially between north and south field poles near together, instead of radially across the dynamo, as shown in Figure g. Various special forms of winding permit this arrangement. There must be a pair of commutator brushes for every pair of principal poles in a “‘lap-wound” multipolar direct-current dynamo. Sometimes small extra pole pieces are used between the main poles to promote more efficient commutation of the current. This device for preventing sparking at the brushes was invented by Richard H. Mather of Windsor, Conn., and protected by United States Patent No. 321,990, issued July 14, 1885. Plate 6, showing a General Electric direct-current motor field, indicates these supplementary pole pieces clearly. The pole pieces about which the field coils are wound are sometimes of cast steel, but often, like the armature frames, are built up of chant sheets of baal steel, punched to form and laid beside each other to make up a considerable thickness. Plate 7, upper, shows this con- [24] PLATE 7 Upper: Laminated field pole for use with compensated direct-current machines. Lower: Armature and shaft for direct-current mill motor. Type as indicated in Plate 6. Courtesy of the General Electric Company Auvdwioy II}ZD9TY [eslauasy 9y3 Jo Asajinog “dy cog‘z ‘ajod +1 ‘10,0 JUdIINI-I9IING 8 ALVI1d DYNAMOS AND MOTORS struction. In the armature frames, the thin steel punch- ings are separated by thin insulators in order to cut down the eddy currents. Several different types of coil windings for armatures are in use, some of considerable complexity. Readers particularly interested in the technical details of the modern direct-current dynamo should consult some of the excellent treatises available. Here we must confine ourselves to the inspection of Plates 6, 7, lower, and 8, which show some of the details as they have been worked out by the ablest manufacturers. Let us now mention some of the great names in Amer- ican electrical invention. Dr. Elihu Thomson of Lynn, Mass., has won world-wide fame. Born at Manchester, England, in 1853, he came with his parents to Philadel- phia as a boy of 5. He taught in the Philadelphia High School as a young man and conducted there some of his most interesting experiments. After his discovery of electric welding, he devoted himself to commercial scien- tific work, but remained always a public-spirited citizen. As a member of the corporation of the Massachusetts Institute of Technology, his influence has been of great value. He holds more than 700 patents, including some of the most fundamental in the electrical art. Among his many honors are the Rumford, John Fitz, Kelvin, and Faraday medals. He is a member of the National Acad- emy of Sciences. Dr. K. T. Compton, president of the Massachusetts Institute of Technology, says of him: More than any man now living, or in fact, more than any man in history, it seems to me that Professor Thomson has combined in a most remarkable way the constructive powers of the inventor, the thoroughness and soundness of the man of science, and the kindly balance of the ideal philosopher, teacher, and friend. Because of these qualities he is held in equally high esteem by engineers and in the most highbrow academic circles. Dr. E. W. Rice, honorary chairman of the board of the General Electric Company, tells the following little story, not less creditable to Doctor Thomson’s versatile ingenu- ity than to the extraordinary kindness of his heart. [25] GREAT INVENTIONS I regard it as the most fortunate event in my life that I met Elihu Thomson when I was young. I was but a boy in my teens when we met in the Philadelphia High School in 1876. He was still a young man of but 23, although already recognized as a brilliant teacher with a growing reputation as a lecturer and scientist. . . . I was fortunate enough to interest him in my efforts to make a telescope. Being too poor to buy one, I had resolved to build one and had read all I could find on the subject. . . . As Professor Thomson was a chemist, I thought he might be willing to tell me how to make the proper alloy, and so, rather hesitantly, I presented my problem. I shall never forget his cordial response. He acted as if the problem were of the utmost importance and of great personal interest. To my delight, he said that he too had made a telescope and had also decided upon the reflecting type, but that speculum metal was no longer used, as a mirror of glass was much better. He then told me that he had devised a new and simple way of making a glass mirror without machinery and without moulds. .. . He demonstrated the theoretical correctness of the process, and stated that the only geometrical form that could result from such a process was a section of a perfect sphere. The process was so ridiculously simple as to be incredible, but I went ahead, and by following his instructions, eventually succeeded in making a satisfactory glass mirror for a small telescope. To Doctor Thomson we owe, among his hundreds of inventions, the three-phase armature winding of dynamos patented January 13, 1880. The original specification contained a statement that this winding was connected to a commutator to produce direct current for arc lights, or to collector rings for use with alternating currents. The first machine of this type, and, in fact, the first dynamo with three-phase winding, is a machine wound by Doctor Thomson himself in 1879 at Philadelphia and now pre- served in the United States National Museum and shown in Plate 10. The great power generators of today are three-phase machines of the same principle, and the trans- mission lines are lines fed from such three-phase dynamos. The machine, as a generator for arc lights, came into very extensive use, and after the introduction of alternating current systems about 1886, it also soon became the standard form of alternating current dynamo. [ 26 ] DYNAMOS AND MOTORS One of his most important inventions was that of the magnetic blow-out, shown in the Thomson patent No. 283,167 of August 14, 1883, which applies to the use of a magnetic field to blow out any arc or disturb any arc formed on the opening of a circuit. This magnetic blow- out, practically without modification, has been very widely used. The electric street car controllers of the present time employ the magnetic blow-out, as do many other kinds of control apparatus for high-powered electric cir- cuits. Another important application, somewhat different from mere switching, is the lightning arrester, which em- ploys the magnetic blow-out, covered by patent No. 321,464 of July 7, 1885, which was filed November 8, 1884. Not only does this arrester employ the magnetic blow-out principle, but it also shows for the first time a “horn” arrester, whereby an arc or connection formed by light- ning is gradually opened or broken by the rise of the arc between wider and wider gaps between the discharge pieces. Doctor Thomson demonstrated as early as 1879 the step-down transformer for reducing the voltage of alter- nating current to the requirements of practice. The transformer system of electrical distribution did not come into commercial application until 1887, and there were interferences in the Patent Office between the claims of different inventors. Doctor Thomson received broad claims on his invention in this field in his patent No. 698,156 of April 22, 1902. One of his most important inventions was that of electric welding, now called the resistance method. He disclosed for the first time the art of joining metals by placing pieces in contact and passing through the contact a current of electricity sufficient to fuse and unite the pieces. The basic patent for this was No. 347,140 of August Io, 1886. The applications of this method have increased amazingly and are still rapidly growing in number. A more detailed statement of this invention may be found in the Research [27] GREAT INVENTIONS Narratives of The Engineering Foundation. A whole group of inventions followed the original patent referred to above—many of them of importance in the electric welding art. They formed the basis of the organization known as the Thomson Electric Welding Company. Before the practical development of the incandescent lamp by Edison, the electric arc had come into rather wide use. A number of practical arc lamps were designed by different inventors. Many thousands of arc lamps were once in operation under the patents of the Thomson- Houston system, and only in recent years has the use of these arc lamps decreased because of the introduction of large, high-power incandescent lamps made on the tung- sten gas-filled principle. The Association of Electrical Inspectors has given Doctor Thomson the name of “father of electric safety grounding”’ because the grounded secondary in the trans- former was introduced by him as a means for saving life. High-tension primary lines may become connected with low-voltage secondary lines, and it would then be very dangerous if anyone touched the apparatus while standing on a grounded surface, such as a damp floor. After the complete remedy was found in the grounding of the secondary, there was then no objection to the introduction on a large scale of the transformer system. It required more than 20 years, however, before the use of such safety arrangements as the grounded secondary became man- datory. One of the most fruitful of Doctor Thomson’s investi- gations was the discovery of the repulsion principle with alternating current—an important principle lying at the base of much of the alternating-current development of the years following. The induction motor for single-phase work and the repulsion motor and combinations of these are based on the discovery of electromagnetic repulsion by alternating currents. In 1889 there was an exhibit at the Paris Exposition of such apparatus. It 1s now housed in [ 28 ] PLATE 9 Dr. Elihu Thomson wnasnyy [euoneN oy3 ut =“6Zg1 Ul UOsWOY Ty, NYY “Aq Aq punoA, -ourvudp asvyd-sary} uoswOYy [eUIsIICG Ol ALVW Id DYNAMOS AND MOTORS the Royal Institution in London, as supplementary to the Faraday apparatus, and it was used by Dr. J. A. Fleming in a famous lecture before the Society of Arts (London), May 14, 1890, republished in the United States in the aes World, of June 14 and 21, 1890. In connection with these repulsion experiments may be mentioned what is known as the shaded pole, which was extensively in- Fic. 11. The electric repulsion principle. Diagram to illustrate Dr. Elihu Thomson’s invention of the electric repulsion motor troduced into apparatus such as meters and in fan motors run by alternating currents; a repulsion motor based on the same principles was the first alternating-current motor. The repulsion-motor principle is most striking. Refer- ring to Figure 11, suppose a current to be started in a coil, a, which of course immediately produces a magnetic field whose lines of force emanate as indicated from the soft iron core, 4. According to the principles of induction a momentary current is induced in the coil, ¢c, which in its turn sets up a magnetic field oppositely directed to that emanating from 4. Hence, there is a momentary repulsion of the coil. If now the current in a is broken, the repulsion changes to momentary attraction. If the current is again [ 29 ] GREAT INVENTIONS LAS f i fa Fic. 12. Experiment illus- trating electric repulsion started in reverse sense there is a momentary repulsion. By suitably modifying the self induction of the coil, c, the phases of the currents in a and ¢ can be so adjusted that the repulsion impulses far out- weigh the attraction impulses during the flow of an alterna- ting current in a. Doctor Thomson illustrated this by a beautiful experiment shown in Figure 12. The coil, c, 1s connected with a small incandescent lamp and im- mersed in a glass jar of water. Immediately upon starting the alternating current in a, the lamp lights up owing to the induced alternating current, and with its coil it rises toward the surface of the water until reaching such a point that gravity balances repulsion. By altering the strength of the electric current, the lamp may be made to vary in brightness and to bob up and down in a mysterious manner. The principle of repulsion was applied by Doctor Thomson in measuring instruments, electric arc lamps, and alternating-current motors. Another of his important inventions that has come into extensive use is the Thomson integrating wattmeter. The first practical device of this kind was the one which was produced in Lynn in 1889 and submitted in Paris in a meter competition, with the result that the Paris prize of 10,000 francs was divided between the Thomson and Aron [30] DYNAMOS AND MOTORS meters. This Thomson recording wattmeter was used by the electrical jury at the World’s Fair at Chicago in 1893, as a standard of comparison for all other meters presented. Other pioneer inventions of Doctor Thomson, patents Nos. 428,648 and 508,654 of 1890 and 1893, relate to cool- ing of transformers by oil and by water. These principles are very widely used. The Thomson patent No. 617,546, January Io, 1899, filed February 28, 1898, was the pioneer patent for the so-called contactor system of control, which became of the greatest value in railway work and is today the practically universally adopted method of control. Besides these important inventions in the field of elec- trical production and distribution, Doctor Thomson was among the first in the study of radio waves and wireless transmission, and in high-frequency alternating-current work generally, such as the singing arcs. He also took a prominent part in X-ray development. Quite out of the electrical line was his continuous centrifugal separator for separating cream from milk, patented with his colleague, Professor Houston, in 1877. These partners founded the celebrated electrical firm of Thomson and Houston at Lynn, Mass., now a branch of the General Electric Company. Alternating-current electrical engineering owes much to Nikola Tesla, born 1857 in Smiljan, Lika, a border land of what was then Austria-Hungary. He is of Serbian stock. His father and uncle were clergymen of the Greek church. It was intended to educate Nikola also for the church, but his genius for mechanism and science was too strong, and he was allowed to attend the Polytechnic School at Gratz. It is said that while studying there the Gramme direct- current ring-armature dynamo, he felt instinctively that the commutator and brushes were unnecessary to the suc- cessful production and use of electricity. Studying lan- guages to aid him in the engineering profession, Tesla gravitated to Paris, and at length to New York. A warm admirer of Thomas A. Edison, he obtained a place imme- diately in the Edison works and afterwards in the West- 137 | GREAT INVENTIONS inghouse Company. But not for long. Tesla’s inventive genius demanded free expression. At that time, about 1885, alternating current had little general application. Few electrical engineers either used it or understood it, and the efficiency of such alternators as had been constructed was low. Tesla was a pioneer in the art. He perfected his valuable invention of the applica- tion of the polyphase rotating field to the induction motor. Of basic importance were his patents Nos. 382,279 and 382,280, granted May 1, 1888, in which he set forth the principles of this valuable type of alternating-current machine, surpassing all others in mechanical simplicity. Tesla experimented at great length with high-frequency alternating currents, and with the properties of induction, capacity, and insulation associated with them. So astonishing and novel were his demonstrations, that after an extraordinary lecture before the American Institute of Electrical Engineers, delivered at Columbia College on May 20, 1891, he was urgently invited to visit Europe to repeat his experiments before audiences there. In 1892 he gave a lecture in London before the Institution of Electrical Engineers, and by special request repeated it the next day at the Royal Institution. After that he addressed the Société Internationale des Electricians and the Société francaise de Physique in Paris. When he returned to America, so great was the fame of these lectures that when in February, 1893, after addressing the Franklin Institute in Philadelphia, Tesla repeated his lecture a week later in Saint Louis before the National Electric Light Association, 5,000 people crowded the hall. All of these lectures were illustrated with experi- mental effects so novel, astonishing, and even terrifying in the behavior of currents at frequencies of 100,000 to 1,000,000 alternations per second, wherein all the resources of induction and capacity, the arc, the spark, and the glow discharge were reinforced by sound theory and surpassing ingenuity, that the audiences were spellbound. [ 32] DYNAMOS AND MOTORS One of the most colorful personalities among great American inventors of electrical devices was George West- inghouse (1846-1914). Even his birth was surrounded with the atmosphere of successful invention. On that day his father, after an all-night inventive vigil which absorbed him so entirely that he totally forgot even his approaching parenthood, solved the last difficulty of a successful invention. Returning to his home from the shop he learned for the first time of the birth of his famous son. The last words of his wife to him in the morning had been ‘“‘Well, good luck to the new invention,” and her first words to him at night were “How does the ma- chine come on?” A railroad accident started young Westinghouse on his career. Two cars ran off the track, and his inventive mind conceived a great saving of time if a car replacer were at hand on which cars could be drawn back upon the rails by the traction of an engine. A small company was formed to make and sell his invention, and other railroad appliances were soon added to its output. It was while traveling for this company that he took the last vacant seat in the train beside a young lady so engaging that he fell in love on the spot and soon made her his wife. The marriage was wholly congenial. Mrs. Westinghouse had much executive ability and relieved him of many cares in later life. She survived him only a few weeks, and they are buried together in Arlington National Cemetery. A second railway accident, a head-on collision between two trains that could not be stopped in time with the hand brakes then in use, incited Westinghouse to his greatest invention, celebrated and used the world over— the automatic air brake. But that story must be re- served to a later chapter. Here we will mention his electrical interests and inventions, which, however, grew out of his development of the air brake. Yet we must not omit the extraordinary adventure of the gas well. [33] GREAT INVENTIONS It was after his success with the air brake, in 1884, that his son, George Westinghouse, Jr., was born in New York. As soon as prudent, Mr. and Mrs. Westinghouse were returning to Pittsburgh, then in the midst of the excite- ment over the discovery of natural gas at Murrysville. This interested Westinghouse greatly. His wife chaffed him a little on the probability of his thereafter spending all his time at Murrysville. “Not,” said he, “if I can use your garden.” Sure enough, he drilled close to the stable, and at 1,575 feet the workmen struck a gas well that blew the machinery and mud over the entire lawn with a roar that brought a crowd to the scene. The force of the gas current was so great that stones and planks brought to confine it were hurled aside like straws. But after a week of effort, Westinghouse contrived an in- vention that stopped the flow. Then he bought an old franchise broad enough to conduct any kind of business under, piped the city, invented and patented improved devices for distributing gas of high pressure and selling it at low pressure, bought other properties on which to prospect for new wells, added other public service enter- prises, and at length his “Philadelphia Company” became expanded to control nearly all the public services of Pittsburgh and its suburbs. It was his varied railroad work that led Westinghouse into the line of electrical inventions. As early as 1875 he became interested in railway signaling and safety devices, and later he combined a Massachusetts company which manufactured signal apparatus with the Interlocking Switch and Signal Company to form the Union Switch and Signal Company. Between 1881 and 1891 he ob- tained 15 patents on inventions in this field, mainly relating to combinations of electrical and compressed air elements, especially in block signaling. Among the engineers of the Union Switch and Signal Company was William Stanley, whose invention of an automatically regulating dynamo had caught Westing- [34] DYNAMOS AND MOTORS house’s attention. Another gifted young engineer who was made a member of the Westinghouse staff about this time was Nikola Tesla, whose basic inventions relating to the polyphase alternating-current and induction motors we have already mentioned. Little by little the company entered the incandescent lighting field in competition with the Edison interests. But Westinghouse, with his quick mind, perceived the advantage of the alternating-current system over the direct current, because of its cheaper transmission and the simpler mechanism required. English patents had been issued in 1883 to Gaulard and Gibbs for a system of alternating-current distribution through transformers. Westinghouse purchased several Gaulard-Gibbs transformers and set Stanley to experi- menting with them. Stanley made improvements adapt- able to alternating-current transmission for power and lighting. Westinghouse thereupon purchased the Gaulard- Gibbs rights for $50,000, and organized the Westinghouse Electric Company early in the year 1886. By the follow- ing autumn a test installation was prepared with a new constant-voltage alternating-current dynamo by Stanley, a battery of transformers, and 400 lamps operated from a 2,000-volt supply over a 4-mile transmission line. It was a ‘revolutionary move, inaugurating an era of cheap power for lighting and other purposes, so that the small towns as well as the great cities could enjoy the comfort of the elec- tric light. Great opposition was encountered from the established direct-current industry of Edison. Books, pamphlets, and news articles painted in vivid colors the terrible dangers of high-voltage transmission. In New York City, especially, the opposition to alternating-current power circuits was most bitter. Edison himself published an article entitled “The Dangers of Electric Lighting” in the North American Review; Westinghouse countered with “A Reply to Mr. Edison” in the following number. About that time, too, electrocution was introduced as [35] GREAT INVENTIONS the death penalty in New York, which tended to prejudice the public against high-voltage alternating-current trans- mission. But little by little the Westinghouse system prospered, until finally its great coup was achieved in obtaining the contract for lighting the Chicago World’s Fair of 1893. There was used at the Fair a battery of I2 great alternators furnishing the Tesla multiphase current, operating 250,000 lamps of 16 candlepower, so made as to avoid infringing on the Edison patents. Shortly afterwards the Westinghouse company con- tracted to furnish for the Niagara Falls project three great generators. The first 5,000-horsepower turbo- alternator was installed within 18 months and exceeded specifications, yielding 5,135 horsepower. Within a few years 10 such Westinghouse units were installed at Niagara, aggregating §5,000-horsepower capacity. George Westinghouse was one of the most prolific of American inventors, entering a very wide range of fields. Among his electrical patents may be cited as of basic importance United States Patents Nos. 342,553 and 366,544 covering improvements in the alternating-current transformer, and the protection of transformer insulation from humidity. He was not only an inventor himself, but the inspirer of a brilliant corps of engineers and of a loyal corps of workmen. He was also president, not only in name but in fact, of the Westinghouse group of industries, and as such managed the funds and activities with a free hand to promote the great projects which his pioneering brain conceived. The country will seldom see the equal, in inventive genius or in wide-ranging, far-seeing pioneering instinct, of the founder of the Westinghouse industries. We shall reserve the story of his great competitor, Thomas A. Edison, until we come to speak of electric lighting, and shall now continue with our account of alter- nating-current machines. [ 36] SddIAap [BI1I}99[9 Auvul puv dyviq Je 9y} Jo JO}UdAUT “OSNOYSUIISI AA, 351005) We ALV Id : Aurdwo IAJIO]Y [e4auas) ayy Jo Asaq.ino7y “SSUIDUIM YSIP PIAva]to}Ul YIIA : Boe ; B SRE usisoq] “HH adA JOWIOJsuR.y asvyd-aa143 JOJ S[IOD puv 910D :3IYSIY “sJoWIOJsuvs} asvyd-aa143 JOfF MOD 239] Node ie tans crynraeta he ed + cl ALV Id DYNAMOS AND MOTORS THe ALTERNATING-CURRENT DyNAmMo More and more in recent years the large power-genera- ting plants employ the alternating-current instead of the direct-current dynamo. On the one hand this avoids the use of the split commutator, which, though fairly efficient, is less so than the simple slip rings sufficient for the alternator. But a far more important consideration relates to long-distance electrical transmission. To understand this point we must recall that the loss of energy in transmitting electric current is due to its dissipation in the form of heat. It has been shown that the heat produced in a wire is proportional to the square of the current strength multiplied by the electrical resistance, that is, to C?R. The energy, or wattage, of the current is proportional to the current multiplied by the voltage, that is, to CV. It is clear that the energy transmitted, equaling the product CV, is the same if C=1 and V= 10,000 as when C=100 and Y=100. But in the former case the heat loss is proportional to 1 X 10,000R =10,000R, while in the latter case it is pro- portional to 100 X 100 X 100R=1,000,000R. Hence it is clear that for very long lines, ‘where the electrical resistance is unavoidably great, the only recourse to diminish the dissipation of the electric energy in useless heat is to carry a small current at high voltage. This may be accomplished easily by employing a device called the transformer, of which there are several types. The transformer comes directly from the experiments of Faraday, which were cited in Chapter I, and indeed may be said to be his invention. If two coils of wire be wound on the same iron or soft-steel magnetic circuit, of which one of the possible arrangements is shown in Figure 13, and an alternating current be passed through the primary coil, a, it will induce an alternating current in the second- ary coil, 4. If we neglect the small losses of energy due to eddy currents and other causes, the voltages of the Rey GREAT INVENTIONS secondary and primary current may be regarded as in the same ratio as the number of turns of wire in the two coils, and the current strength in the two coils as in this same ratio inverted. Hence, if it is desired to raise the voltage and diminish the current from an alternating- current dynamo by 100-fold to save heat losses in long- Fic. 13. A step-up transformer, to convert alternating current of moderate voltage to alternating current of higher voltage distance transmission, it is only necessary to introduce a step-up transformer whose secondary has about Ioo times as many turns of wire as its primary. At the place where it is to be used, the high voltage may be reduced again to a voltage suitable for lamps and other ordinary purposes by employing a device that is the reverse of the step- up transformer. Naturally much thought by many inventors has gone to the improvement of the details of this fundamentally simple device. The magnetic core circuit is, of course, laminated to reduce eddy currents. The insulation of the secondary coils from each other and from the primary coils must be high. The mechanical stresses and the [38] DYNAMOS AND MOTORS heating effects during use require careful attention. Differences of phase relations of alternation of the currents form an important branch of transformer theory. Various types of connections have been evolved to suit different problems. All of these technical details may be studied by the interested reader in many excellent treatises on the use of alternating currents. Plate 12 shows the core design and completed core and coils of a transformer built for three-phase alternating-current work. Since the transformer deals exclusively with alternating current, the alternating-current dynamo is obviously its natural companion. Alternators have therefore grown in favor rapidly within the last 30 years, during which time long-distance transmission of electricity has greatly multiplied. Another factor favorable to the alternator is the increasing use of the steam turbine as a prime mover because of its great efficiency in converting heat into power. The steam turbine runs naturally at high speeds, which are less obnoxious to alternators than to direct- current dynamos. In the alternating generator, the field magnets must be actuated by direct currents. Hence a small direct-current dynamo is usually provided as a part of an alternating machine. But for many reasons, the places of the field magnets and the armature are frequently interchanged from the usual positions in direct-current dynamos, so that the armature is outside and stationary, while it is the field within that rotates. The convenient words “stator” and “rotor” have been added to the technical language used in connection with the alternator and other similar machines, the stator being the outer, stationary part, and the rotor the inner, revolving part. Thus, with the alternating-current dynamo we may picture the prime mover, which may be a water wheel or a steam turbine, as possibly on the same shaft with the field rotor. The auxiliary direct-current dynamo sends its cur- rent into the field-rotor coils through a pair of brushes [39] GREAT INVENTIONS resting on a pair of slip rings upon the shaft. The rapid rotation of the field magnets induces in the armature coils alternating currents which flow into the primary coils of a step-up transformer. High voltage currents induced thereby in the transformer’s secondary coils may be car- ried hundreds of miles over the gracefully looping trans- mission lines which we have become accustomed to seeing crossing the country in long stretches from one steel tower to another. At the distant city, where current is needed for light and power, the step-down transformer reduces the voltage again to a safe figure. Thus the alternating generator has the advantage of mechanical simplicity, owing to the absence of the com- mutator. Electrically, however, there is a complexity so great that it is impossible to explain it in a book of this character; we can only give some slight indications of its nature. Plates 13 and 14 give a good idea of the alter- nating-current generator. Alternating-current, like direct-current dynamos are usually multipolar, and their armatures are multicoil. The conductors are shaped rods of copper inserted within slots formed by many insulated steel punchings pressed side by side. Designers give close attention to the magnetic leakage and interference, which, owing to the interaction of the moving field poles and induction of the armature currents, are very complicated problems. The number of field poles required in alternator depends mainly on the speed at which it is to be driven, and the number of cycles of alternation per second desired of the current. In America experience has led to the selection of the two rates of alter- nation, 60 cycles and 25 cycles per second, as most suitable. The former is better for incandescent electric lighting be- cause the fluctuations of current are then so rapid that the eye does not perceive flickering. Formerly 25 cycles were preferred for driving large motors and for some other uses, but the present tendency is toward 60 cycles for most pur- poses. If the prime mover drives at moderate speed it 1s [40] PLATE 13 Alternating-current generator. Approximate diameter, 6 feet. Courtesy of the General Electric Company PLATE 14 Rotating field of alternator. Approximate diameter 4% feet. Courtesy of the General Electric Company DYNAMOS AND MOTORS necessary to have rather numerous field poles, sometimes 30 or even $0, to produce a 60-cycle current. On the other hand, to operate with rapidly rotating steam turbines, alternators are usually built with 2, 4, or 6 poles. Radio alternators, to produce enormous numbers of cycles, drive at great speeds, and have many poles. Another feature of the alternating-current circuit is its phase number. If all the coils of the armature are con- nected in a single circuit with only two terminals, the machine is single-phase. If the coils are arranged in two separated groups with four terminals it is two-phase. But the most common arrangement of all is the three-phase system, in which the armature is wound in three inde- endent coils 120° apart. Plate 10 shows a machine wound by Dr. Elihu Thomson with his own hands in this manner in the year 1879. It is on exhibition in the United States National Museum, where it was deposited by the General Electric Company. This machine has a rotating arma- ture with fixed coils, and was designed to give direct cur- rent if desired, but the same general principle applies to the machines with rotating field coils. In the three-phase system, three independent equal voltages are generated during each cycle at 120° phase angle apart, as indicated by Figure 14. The three sets of armature coils will have, of course, six terminals. But it is usual to connect three similar terminals together either within or outside the armature. If a wire were connected to this common Junction it would carry no current, pro- vided the loads on other wires were well balanced. Hence the neutral wire is often omitted, leaving but three wires for the line. A load, composed for instance of electric lights, may be thrown in between any two wires of a three- wire system, or the three wires may all be used at once in the appropriate manner to operate an alternating-current motor. It is clear that the reversal of the current, how- ever many times per second it occurs, does not prevent the current from causing the glowing of incandescent lamps, [41] GREAT INVENTIONS for the wires in the lamps become hot merely because they offer a high resistance to the passage of the current in either direction. It is not the same with arc lamps, for arcs are not readily reversible. As we shall see in Chapter VI, there is usually a marked difference between the posi- tive and negative poles of the arc, which hinders their interchange. Preferably they should be used on direct Fic. 14. Three-phase alternating current diagram current. But direct current can be derived from an alter- nating-current system by the use, for example, of the mercury rectifier, described in Chapter III. THe Direct-CurrentT Moror Direct-current dynamos can be used as motors, and often are, though a machine originally constructed as a motor differs somewhat from a dynamo. Ifa line current passes through the field coils of a dynamo and actuates them, its passage through the armature requires the rota- tion of the armature relative to the field in order that the armature coils may tend to enclose a maximum number of lines of force. The same arrangements of the commutator which produce direct current in the dynamo are suitable to guide the current for the purposes of a motor. Plate 15, upper, gives a disassembled view of a direct-current motor. [ 42] DYNAMOS AND MOTORS When a machine is operating as a motor, the coils of the revolving armature cut the lines of force of the field just as they would if the machine were operating as a dynamo. This produces an electromotive force opposed to that of the line. With no load, the speed of the motor increases until the back electromotive force of the motor approxi- mately equals the driving electromotive force of the line. Beyond this speed the motor can not go. If a load is then thrown on, the motor slows, but the back electromotive force is thereby reduced, and more current is admitted from the line, which tends to speed the motor, and brings a balance at some new speed. The energy required to carry the load is then supplied by the difference between the line current and the back current from the motor. While the self-regulatory tendency just described is a very valuable one, it is not to be forgotten that it would be damaging to throw the full voltage of the line into the armature at starting before any back electromotive force had built up to moderate the current. To avoid this dan- ger, direct-current motors are equipped with a starting box in which the connections are so disposed that while the full voltage of the line enters the field coils at the first con- tact, there is a resistance interposed in the armature cir- cuit, which is gradually withdrawn to zero when full speed is attained. A magnetic clutch holds the handle in the full-speed position. If the current fails, the handle is released and flies back to the “off” position, thus avoid- ing a possible neglect of precaution in restarting the motor. In direct-current motors two methods of winding are in use for different purposes. In one type, called a shunt- wound motor, the armature and the field coils are in sep- arate circuits between the two wires of the line. In the other type, called a series motor, the field coils and the armature coils are connected together to make one circuit across the line. In a shunt-wound motor the field coils are many and of small wire, in order to produce a strong field [ 43 ] GREAT INVENTIONS with the weak current diverted from the armature. In a series motor the field coils are few and of heavy wire, so that while producing strong magnets they will interpose but little resistance to the full current of the line which passes through them and thence to the armature. Shunt- wound motors are more uniform in their speeds under dif- ferent loads but have a weak pick-up at starting. Series motors are more variable with changing loads but are strong at starting. For the latter reason they are often preferred for street cars and other electric and motor vehicles. For some purposes a combination of the two types, called the compound motor, is preferred. THE ALTERNATING-CURRENT Moror Alternating-current motors are more difficult to under- stand and less simple in operation than direct-current motors. These difficulties postponed for a time their gen- eral employment in the industry. Yet they offer certain very remarkable compensating advantages. These mo- tors are of several types. First, we may consider the squirrel-cage type of induction motor, well suited to the three-phase 60-cycle alternating current. As with alternating-current dynamos, it is preferable to construct the alternating-current motor armature as a stator outside the field rotor. Referring to Figure 14, the three-phase current coming in over the line energizes con- secutively the armature coils which are arranged in three groups, spaced 120° apart around the circumference of the armature. That is to say, when the current in group num- ber one reaches its maximum positive value, in group number two, 120° distant, the current is still negative but approaching zero, and in group number three, 120° far- ther around, the current is negative and approaching its negative maximum. The condition is often described as a revolving field. This means, not that the lines of force from the stator revolve, but that as they wax and wane [44] PLATE 15 Upper: Disassembled direct-current motor. Lower: Disassembled alternating-current induction motor. Courtesy of the General Electric Company DYNAMOS AND MOTORS in their regular progression the effect is similar to that which would be produced if the fixed armature were re- placed by a horseshoe magnet which should actually re- volve, carrying its lines of force around with it with its axis in the axis of the rotor. If this were actually the case, it is clear that such a magnet would drag with it a drum- wound rotor free to turn on the same axis. For only by turning could such a rotor avoid continually cutting the lines of force. This leads us to the squirrel-cage rotor construction. It is merely a slotted cylinder of iron with insulated copper bars in the longitudinal slots all connected to a copper ring at each end (Plate 15, lower, top figure.) There is no connection of the rotor to the line currents. All that goes on in the squirrel cage is by induction. Hence this type of motor is often called the induction motor. It is not essential to use a three-phase current with an induction motor, for a single-phase current, although it will not start the rotor, will carry the rotor around after it has once acquired speed by other means. A two-phase current, however, will start such a motor. Induction motors on no load run at a speed synchronous with the alternations of the driving current. If there are two phases in the armature, the 60-cycle current requires of the rotor 3,600 revolutions per minute. If there are eight phases, the rotor speed will be reduced to goo revolu- tions. With load the rotor speed slows down, but ordi- narily the slip of squirrel-cage rotors behind synchronous speed at full load does not exceed 4 per cent. The squirrel- cage motor is weak at starting and best at full load, but has no capacity for speed regulation. It is sometimes spoken of as the constant-speed motor. Other more complex types of induction motor exist. Plate 15, lower, shows a disassembled induction motor. Other types of alternating-current motors ‘require fuller consideration than befits this volume. The in- terested reader is advised to consult some of the excellent [45] GREAT INVENTIONS textbooks on the subject. We shall content ourselves here with a few more observations on special features of the induction motor. If such a motor 1s driven above synchronous speed by an outside power, it becomes a generator, and will supply power to the line. Full load as a generator will be delivered to the line with about the same amount of slip above synchronous speed as the machine displays when dragging behind synchronous speed with the slip accompanying full-load conditions as a motor. This property is useful in certain electrified railroad installations to return power to the line and act as a brake on down-grade stretches. The “synchronous motor”’ is essentially the same as an alternating-current dynamo. It requires direct current to actuate its rotor field. It is not self-starting, but must be brought into synchronism with the alternations of the current of the line. Once in operation it remains in step with the line at all loads within its range. Its synchronous action depends on the fact that its field is separately excited by direct current, so that the field poles are con- tinuing. They can therefore be in harmony with the re- volving field of the fixed armature only when the rotations of the field are at an equal rate with the changes in direc- tion of the armature current. As the synchronous motor will not start by itself, a short squirrel-cage winding is sometimes built into the rotor, by means of which it is brought nearly to synchronous speed with no load before the direct current is applied to the rotor. Its perfect speed regulation and its capacity to operate under a wide range of so-called “power factors” give the synchronous motor a special value in certain kinds of installations. For the uses of wireless communication, alternating currents of enormous frequency are required, ranging from 100,000 to 30,000,000 cycles per second. It is possible to attain some of these frequencies by spark gaps placed in parallel with condensers. Also alternating- current generators of enormous frequency are in use, [ 46] Auvduroy 9113 99]q [esausy ayy Jo Asoj.ino ‘siizjap MOUS 0} PaAouds do ‘UOISSIUISURI] OIDeI IOJ OWeUAD AdUdNbodIj-YSIY UOSIapULXOTY I Y ISS! ; 4 F-Yory IV Se SARRRERRBR RRS “SATE ot ALVId guvjd Suidund 91139972 UOJSUTYSE AA SS ISH * i 3 Zé. b a ps4 nod pAlsiero ot LY ALWId DYNAMOS AND MOTORS although these are now yielding to large electron-tube generators. Dr. E. F. W. Alexanderson, chief engineer of the General Electric Company, devised in 1913 an alternating generator of 100,000 cycles for long-distance wireless transmission. It comprises a large, strong, steel wheel with narrow rim in which are milled slots on the opposite faces, thus resembling a gear wheel whose teeth are not cut through to the rim of the wheel. The slots are filled with nonmagnetic material in order to present a smooth surface and thus reduce air friction. The wheel runs at high speed between two water-cooled laminated armatures, wire-wound in many open slots. As each wheel-slot in succession passes by an armature conductor it changes the induction. The field magnetic flux is carried by pole pieces through the armature laminations and the rotating wheel. The air spaces are very narrow— only 0.015 inch in width—so that great accuracy and stiffness are required in the wheel, as it revolves at some 20,000 revolutions per minute. (See Gen. Elec. Rev., vol. 23, p. 815, 1920.) In Plate 16 the device is shown with top half removed, exposing details. It is related that after one of Faraday’s lectures, in the course of which he demonstrated electrical devices, a member of the English government rather patronizingly said to him in substance: “Very interesting, Mr. Faraday, but of what practical use is it?’ “Some day, My Lord, you will tax it!” was Faraday’s reply. That day came long ago. The total generation of electric power in the United States in the year 1930 is reported by the American Institute of Electrical Engineers as 96 billion kilowatt- hours, equal to over 120 billion horsepower-hours. From 1921 to 1928 the average rate of increase per year was 11.5 per cent. Over 60 per cent of the electric power is being produced by steam-driven dynamos. The tendency in recent years is toward the combination of the steam turbine with the alternating-current dynamo. Most recently the Emmet mercury-vapor turbine, which [ 47] GREAT INVENTIONS operates at a higher temperature and with greater eff- ciency, is beginning to be associated with the steam turbine as a prime mover. In the usual engineering practice of 1920 it took, on an average, 30,000 British thermal units of heat to produce one kilowatt-hour. The average had declined in 1930 to 18,500 B.t.u. In 1930 a plant using the new Emmet mercury-vapor turbine combined with a steam turbine required but 10,180 B.t.u. per kilowatt-hour. This is an efficiency of 33-4 per cent, as computed from the total energy of the fuel. Taking account of the temperatures of the gases, 56 per cent is the maximum limit of possible conversion of the heat into mechanical energy, according to the principles of thermodynamics. These figures show the high efficiency now reached in the combined processes of combustion, heating of liquids, conversion of heat into mechanical energy, and finally into electric energy. The electric dynamo units are growing larger. For example, the United Electric Light and Power Company recently installed two 160,000-kilowatt generators in the same space that was previously occupied by two 35,000- kilowatt units, and the Brooklyn Edison Company in- stalled two 160,000-kilowatt generators in place of two of 50,000. In this country the great alternating generators are often constructed to deliver current at 15,000 to 20,000 volts potential, while in Europe there are several plants where voltages of 25,000 to 35,000 are generated. The beauty of electric power installations is well shown in Plate 17, which depicts the high-level pumping plant of the Washington Water Works. In each transverse row there are three Westinghouse motors driving Worth- ington centrifugal pumps. All are 60-cycle alternating- current machines, of 2,200 volts pressure, and from 500 to 770 horsepower. The twin pumps have each 10,000,000 gallons capacity, and the single ones on the left 20,000,000 gallons. 1 48 ] CHAPTER III ELECTRONS AND X RAYS As our story approaches the subjects of electric lighting, X rays, and wireless, we come into the field of the play of molecules, atoms, and electrons. These structures are invisible even with the most powerful microscopes. Never- theless, Sir J. J. Thomson, Lord Rutherford of Nelson, and their colleagues of the Cavendish Laboratory at Cam- bridge, England, by their ingenious experiments, have prepared a way into this enticing domain, into which many other physicists in Europe and America have pressed onward during the last 30 years. We all know of matter in three states, gaseous, liquid, and solid, as, for instance, air, water, and copper. Long ago it was found that many solids could be melted into liquids, and liquids changed into gases, if only they are heated to suitable temperatures. In the case of water, summer temperatures suffice to melt winter’s ice into liquid water, and the cook-stove turns water plentifully into steam. What we see and call steam, to be sure, is but a cloud of liquid water drops, similar to the fleecy clouds in the atmosphere. Real steam is invisible, like air itself. It occurs in the little, apparently vacant space just in front of the end of the spout of a boiling teakettle. Gases, such as air, hydrogen, oxygen, nitrogen, and the rest, behave very differently at atmospheric pressure and in vacua. For instance, at atmospheric pressure they strongly resist the flow of electricity, unless their resis- tance is broken down by high voltages, as in lightning flashes, the spark, and the arc. But when the pressure is [49] GREAT INVENTIONS reduced to 1/1,000 part of atmospheric pressure or less, an electric current at moderate voltage easily sets up a con- tinuing discharge. The coloring displayed in the discharge of electricity through vacuum tubes is very striking. Recently, es- pecially in Paris and London, but to a considerable extent in American cities also, many advertising signs have been displayed by red, yellow, and greenish-blue electric dis- charges through evacuated glass tubing. At the Colonial Exposition at Paris in 1931 a long avenue was entirely lighted at night by many 25-foot columns of such lights. Fig. 15. Electric discharge in a high vacuum (diagrammatic) Each column had six vertical glass tubes, each about an inch in diameter, with three greenish-blue and three red tubes arranged alternately. To obtain these colors the alternate tubes probably contained the gases of mercury and neon. The electric discharge through high vacuum is indi- cated by the diagram, Figure 15. The current flows from the positive pole or “anode,” 4, to the negative pole or “cathode,” C, and produces a glow which has several interesting features. For a considerable distance from the anode there is seen the beautifully colored “positive glow.” Then comes a dark space called the “Faraday dark space,” then a new region of “negative glow,” and after it the “Crookes dark space.”’ Finally comes the velvety, feebly glowing region close to the cathode. [50] ELECTRONS AND X RAYS At fairly low pressures bluish rays of light are plainly seen moving from the cathode in straight lines across the Crookes dark space. As they fall on the glass walls of the discharge tube, they excite thereon a greenish phosphor- escence. These are the so-called “‘cathode rays.” At still higher vacua the cathode discharge continues, but is invisible. THE ELEecTRON Sir J. J. Thomson, Cavendish professor of physics and Master of Trinity College, Cambridge, performed the Fic. 16. J. J. Thomson’s discovery of the electron. Cathode rays, which are electrons in motion, tending to be deflected to p’ by the magnetic field indicated by the arrows, are restored to p by the electric field, DE. From the electric and magnetic quantities involved, Thomson determined the charge and mass of the electron epoch-making experiment illustrated by Figure 16 and described in the following abstract of the account of Doctor Thomson himself in a paper entitled, “On Bodies Smaller than Atoms,” which was published in the Smith- sonian Report for the year 1901. He showed, in fact, that objects more than a thousand times lighter than a hydro- gen atom exist. These [cathode] rays are now known to consist of negatively elec- trified particles moving with great rapidity. We can determine the electric charge carried by a given mass of these particles by measuring the effect of electric and magnetic forces to deflect them. It was some time, however, before a deflection by an electric force was observed, and many attempts to obtain this deflection were unsuccessful. By reducing the pressure of the gas inside the tube to such an extent that there was very little gas left to conduct, I was able to obtain the [51] GREAT INVENTIONS deflection of the rays by an electrostatic field. The cathode rays are also deflected by a magnet. Let us adjust these forces so that the effect of the electric force just balances that of the magnetic force. From the magnitudes of the electric and magnetic forces required for such a balance it was found that to carry unit charge of electricity by the particles forming the cathode rays only requires a mass of these particles amounting to one ten-thousandth of a milligram, while to carry the same charge by hydrogen atoms would require a mass of one-tenth of a milligram. In Figure 16, the anode, 4, is perforated by a slit to allow free course to certain rays from the cathode, C. A metal diaphragm, B, containing a narrow slit, is inserted so that only a single fine pencil of rays is permitted to pass to the end of the tube. A powder of zinc blende is deposited there to reveal by its phosphorescence the exact spot hit by the rays. D and E are two plates elec- trically charged to any desired difference. Outside of the discharge tube is a uniform magnetic field indicated by the arrows. It is at right angles to the path of the cathode rays and also at right angles to the electric field between D and E. Without turning on the electric field, the rays are deflected by the magnet into a curved path leading to p’ as shown. But with a suitable electric field, D, E, the magnetic deflection can be balanced so as to bring the rays back to the straight course ending at p. Doctor Thomson continues: The exceedingly small mass of these particles for a given charge compared with that of the hydrogen atoms might be due either to the mass of each of these particles being very small compared with that of a hydrogen atom, or else to the charge carried by each particle being large compared with that carried by the atom of hydrogen. It is therefore essential that we should determine the electric charge carried by one of these particles. The problem is as follows: Suppose in an inclosed space we have a number of electrified particles each carrying the same charge, it is required to find the charge on each particle. It is easy by electrical methods to determine the total quantity of electricity on the collection of particles, and knowing this we can find the charge on each particle if we can count the number of particles. To count these particles the first step is to make them visible. We [52] ELECTRONS AND X RAYS can do this by availing ourselves of a discovery made by C. T. R. Wilson, working in the Cavendish Laboratory. Wilson has shown that when positively and negatively electrified particles are present in moist dust-free air a cloud is produced when the air is cooled by a sudden expansion, though this amount of expansion would be quite insufficient to produce condensation when no electrified particles are present: the water condenses round the electrified particles, and, if these are.not too numerous, each particle becomes the nucleus of a little drop of water. Now Sir George Stokes has shown how we can calculate the rate at which a drop of water falls through air if we know the size of the drop, and conversely we can determine the size of the drop by measuring the rate at which it falls.through the air. Hence by measuring the speed with which the cloud falls we can determine the volume of each little drop. The whole volume of water deposited by cooling the air can easily be calculated, and dividing the whole volume of water by the volume of one of the drops we get the number of drops, and hence the number of the electrified particles. We saw, however, that if we knew the number of particles we could get the electric charge on each particle; proceeding in this way I found that the charge carried by each particle was about ... 2.17 X 107? electro-magnetic units. . . . In the electrolysis of solutions . . . the atom of hydro- gen will carry a charge equal to 2.27 X 10—*° electro-magnetic units. . . . These numbers are so nearly equal that, considering the difficul- ties of the experiments, we may feel sure that the charge on one of these gaseous particles is the same as that on an atom of hydrogen in electrolysis. This result has been verified in a different way by Professor Townsend, who used a method by which he found, not the absolute value of the electric charge on a particle, but the ratio of this charge to the charge on an atom of hydrogen, and he found that the two charges were equal. As the charges on the particle and the hydrogen atom are the same, the fact that the mass of these particles required to carry a given charge of electricity is only one-thousandth part of the mass of the hydrogen atoms shows that the mass of each of these particles is only about one one-thousandth of that of a hydrogen atom.... We have obtained from the matter [occurring in the cathode rays] particles having a much smaller mass than that of the atom of hydrogen, the smallest mass hitherto recognized. These negatively electrified particles, which I have called corpuscles, have the same electric charge and the same mass whatever be the nature of the gas inside the tube or whatever the nature of the electrodes; the charge and mass are invariable. They therefore form an invariable constituent of the atoms or molecules of all gases and presumably of all liquids and solids. [53] GREAT INVENTIONS Nor are the corpuscles confined to the somewhat inaccessible regions in which cathode rays are found. I have found that they are given off by incandescent metals, by metals when illuminated by ultra- violet light, while the researches of Becquerel and Professor and Madame Curie have shown that they are given off by that wonderful substance the radio-active radium. In fact, in every case in which the transport of negative electricity through gas at a low pressure (i.e., when the corpuscles have nothing to stick to) has been examined, it has been found that the carriers of the negative electricity are these corpuscles of invariable mass. Later researches by Thomson, his associates, and others, and by Dr. R. A. Millikan, whose exact measurement of the quantity “‘e’” is described by him in the Smithsonian Report for Igt0, page 231, show that the mass of the negative corpuscle, now generally called the electron, is even smaller than Thomson indicates above. It is now accepted as 1/1,848 part of the mass of a hydrogen atom, which throughout the nineteenth century was supposed to be the smallest thing in Nature. The electron which carries (or perhaps better which is) the ultimate single unit of negative electricity, has been proved to be a constituent of every kind of material found in Nature. The hydrogen atom contains only one electron. Atoms of all other substances contain larger numbers of electrons up to 200 or more in the case of very heavy chemical elements like radium or uranium. Since the lightness and smallness of the electron equip it to be the principal actor in the flow of heat and electricity as well as in electric lighting, X rays, and radio, it has seemed proper to give this somewhat long account of its discovery as explained in the original sources. Regarding other constituents of atoms it will be suff- cient to state merely the results and not the methods which have led to present knowledge of the structure of matter. There is another entity called the proton which carries (or perhaps better which is) the ultimate single unit of positive electricity. It is electrically equal but opposite in charge to the electron. Its mass is 1,847 times [54] ELECTRONS AND X RAYS the mass of the electron, so that it is comparatively sluggish in motion and therefore, though sometimes very influential in a quiet way, takes little active part in the transfer of electricity and heat. The hydrogen atom con- sists of one electron and one proton, and, so far as we know, of nothing else. It is clear that these opposite electric charges must be held apart in the atom by some powerful force, presumably the centrifugal force of rapid orbital motion. Otherwise annihilation would ensue, as the electricities would rush together. It is believed that in the interiors of the sun and stars, where temperatures of millions of degrees and pressures of millions of atmospheres prevail, annihilation of matter is actually proceeding. Thereby the orbital atomic energy which opposes annihi- lation is being converted into radiation such as light, or rather into the short-wave forms called X rays, which by successive transformations become light at the surface of the stars. In atoms of all the chemical elements except hydrogen, protons and electrons are agglomerated into very compact central nuclei. Thus far it has proved too difficult for experiments fully to reveal how this occurs. Around the nucleus lie outside electrons at distances which, though far less than can be examined by the highest-powered micro- scope, are yet, when compared to the sizes of the electrons and the nucleus, somewhat like the distances of the planets from the sun as compared to the sizes of these heavenly bodies. Thus an atom is far from being a solid ball, as some early theories of atoms supposed. It is, on the con- trary, a lattice of rather definite total size. In such a lattice free space is almost the exclusive constituent. The electrons and the nucleus which comprise the frame of the lattice are almost as insignificant in size relative to the lat- tice as are motes compared to the volume of air in a room. As proved by Moseley, whose untimely sacrifice in the World War must ever be lamented, the number of outside electrons in the atoms increases regularly, step by step. [55] GREAT INVENTIONS Hydrogen has one, helium two, lithium three, and so on up to uranium with g2 outside electrons. Uranium stands at the end of the list of chemical elements so far as we yet know. In the larger atoms, the association of these outside electrons with the nucleus becomes very loose. Even the stability of the nucleus itself totters in some very complex atoms. In radium, thorium, and uranium a con- tinual splitting off of fragments of the atoms occurs. This process reduces these broken atoms eventually to the metal lead, with a remainder of several atoms of helium gas. Thus, in a way entirely out of man’s control, Nature herself brings true the dreams of the old alchemists who hoped to transmute one element into another. The alchemists, however, worked for gold. Nauure is satisfied, like Bassanio in ye Merchant of Venice, with base lead. Nevertheless by powerful electrical means some experi- menters appear to have broken atoms of other chemical elements, and thereby have produced something nearly akin to alchemistic transmutations. SoLips AND ELEctTRIc CONDUCTION A solid, then, is not a solid, according to the modern view. It is a bounded portion of free space wherein in- numerable ultra-ultra-microscopic particles, each carrying a definite electric charge, are huddled together as if con- strained by some immutable bond. This bond is so close that during thousands of years the sharp reliefs of ancient coins have still remained distinct. They have not yet parted with enough wandering molecules from their as- semblages to change appreciably the contours which de- limit their forms. It is then only a definitely bounded region of free space, penetrable by sufficiently small mis- siles almost without obstruction, that is the real structure of what we call a solid. The ultimate particles which com- pose it actually fill but an almost inappreciably small pro- portion of its contour. In proof of this paradoxical view, many devices now in [56] ELECTRONS AND X RAYS constant use in laboratory experiments and commercial arts depend for their operation on the penetration by electrons to and from the interiors of solids. In some apparatus, electrons pass through thin films of metals quite impervious to air. Much stranger than this is the well-known fact that electric energy may be transmitted by wire conductors practically instantaneously for great distances. Electric conduction by solids appears to depend on the looseness of connection which subsists between some of the outside electrons and the nuclei of atoms of the metals. While the major part of each atomic structure remains bound close to its original position in a wire, some of the outside electrons are often dislodged by collision or outside attraction, and have temporary intervals of freedom before reattaching themselves either to their original atoms or to others from which electrons are missing. Especially is this the case in wires and solids of all sorts at high temperatures. There is, indeed, a continual emission of electrons from hot wires which is of the utmost importance in wireless telephony and radio, because it is the foundation of the indispensable electron tube, also called the thermionic tube. An astonishing phenomenon is always before us in the conduction of electricity by metallic wires. Electrical effects are produced almost instantaneously at immense distances. With alternating currents such effects are reversed in ordinary circuits 60 times a second, and may indeed be reversed a hundred thousand times a second or even much oftener. Dr. H. M. Barlow of University College, London, contributed in 1929! a theory of electric conduction which he modestly describes as “‘an effort to provide a starting point.” Many other scientific men have previously discussed metallic conduction in some- what similar terms, but Doctor Barlow’s paper has some novel features and is one of the latest. 1 London, Edinburgh, and Dublin Philosophical Magazine, ser. 7, vol. 8, p. 289, 1929. [57] GREAT INVENTIONS He assumes that the atoms in conducting solids lie so closely together that their outer electron orbits nearly touch. Hence an electron finding itself in that part of its orbit midway between two atomic nuclei requires little expenditure of force to leave the orbit of its own atom and continue along the orbit of the adjacent atom. But no atom can thus give away an electron to a neighbor unless it receives at the same time a replacement electron from elsewhere, because electric attraction forbids. “A cur- rent,” says Barlow, “‘consists of a series of electrons passing simultaneously along a chain of atoms. In general the chain will have a zigzag form, but with a resultant direc- tion parallel with the electric force.” The astonishing rapidity of electric conductivity is seen to depend on the fact that exchanges go on simultaneously all along the wire. It is not as though each electron carried its charge from one end of the wire to the other. Its path is really infinitesimally short, and yet, short as it is, it is traversed at a velocity above 10 miles per second. These consider- ations explain the speed of transmission of electricity. Such interesting speculations as these of Barlow’s show us at least a plausible view of how the orbital structure of atoms and their possession of easily-divested negatively- charged electrons may render possible those astonishingly rapid transferences of electric stimuli for hundreds and even thousands of miles in so-called “‘solid’’ wires. THE ELEcTRON TUBE AMPLIFIER About the year 1884 Thomas A. Edison discovered a curious phenomenon which is the germ of the electron tube now indispensable to wireless telephony and many other arts. He found that if, in an ordinary electric lamp bulb with “hairpin” filament, there is introduced besides the two electrodes a third wire insulated completely from the filament when cold, and charged with positive electricity, then as soon as the filament becomes hot a current flows over from the hot filament to the charged third wire. [58] ELECTRONS AND X RAYS The current ceases when the filament becomes cold, and will not flow if the third wire is neutral or negatively charged. Dr. Irving Langmuir of the General Electric Company, making a long series of experiments on the Edison effect about 1913, showed that what we may call the Simon-pure current effect has very definite laws, but is often masked by other nearly unpredictable effects if small traces of gases are contained in the vacuum tube. With highest vacua and gas-free conductors the phenomenon is repre- sented by Figure 16. The loose association between outside electrons and the atomic nuclei permits hot wires to emit electrons in all directions. As the electrons are negative charges, their loss from the parent wire must accumulate a positive charge on that wire if it was neutral before. But as the charge, e, of a single electron is only 1.6 x 10- coulombs, a very great number of negative electrons must fly away before the positive charge caused by their loss can become measurable by instruments. Meanwhile the space sur- rounding the wire is becoming populated with negative electrons, which, repelling each other though attracted towards the positively charged wire, tend to check further emission. The surroundings are then said to have acquired a “space charge.” This phenomenon may be compared with the evaporation from a hot liquid into a closed space. Evaporation increases until the space above the liquid becomes saturated with vapor. Afterwards the balance of evaporation and condensation keeps the proportions of liquid and vapor constant so long as the temperature is unchanged. In one respect such a comparison between the hot wire and the hot liquid fails. The electrons are endowed with such high velocities that they frequently knock off other electrons from the molecules of previously neutral sur- rounding gases. Such molecules are said to be ionized. This leaves the molecular residues positively charged, and [59] GREAT INVENTIONS therefore in a state tending to capture electrons emitted from the hot wire. When such ionization is going on there may be produced faint glows like the glow of the cathode rays in a discharge tube of moderate evacuation. The “electron tube amplifier,” indispensable in radio receiving sets, has within its evacuated space a tungsten wire heated to white heat by an electric current. This causes the wire to emit negative electrons. Nearby is an electrode, preferably of tungsten or molybdenum, which is charged to a fairly high positive voltage. In this condi- tion it attracts the negative electrons emitted by the hot wire and thus causes negative electricity to flow in a cir- cuit through the hot wire toward the positive electrode. Such a flow of electricity is called a thermionic current. Between the hot wire and the positive electrode is in- serted a grid of fine wire connected to the antenna circuit. The grid therefore fluctuates in its charged condition as the electric waves produced by broadcasting come in. Increasing positive charge or, what is equivalent, a dimin- ishing negative charge, on the grid tends to clear the space around it of negative electrons, and so to increase the thermionic current, and vice versa. In certain sensitive adjustments a very small change of the grid voltage pro- duces a relatively large change of the thermionic current. Such is the operation of the vacuum tube amplifier. A primary thermionic current, thus amplified, may be ar- ranged to influence the grid of a second electron tube, thereby amplifying a second thermionic current, and so on. These elements were embodied in the “‘audion” pro- tected by United States patent No. 841,387 granted in the year 1907 to Dr. Lee De Forest on his application filed October 25, 1906. Claims Nos. 1 (in part), 4 and 6 are as follows: 1. In a device for amplifying electrical currents, an evacuated vessel inclosing a sensitive conducting gaseous medium maintained in a condition of molecular activity. .. . 4. In a device for amplifying electrical currents, an evacuated [ 60 | ELECTRONS AND X RAYS vessel, three electrodes sealed within said vessel, . .. means for heating one of said electrodes, a local receiving circuit including two of said electrodes, and means for passing the current to be amplified between one of the electrodes which is included in the receiving-circuit and the third electrode. 6. In a device for amplifying electrical currents, an evacuated vessel, a heated electrode and two non-heated electrodes sealed within said vessel, the non-heated electrodes being unequally spaced with respect to said heated electrode, a local receiving-circuit including said heated electrode and that one of the non-heated electrodes which has the greater separation from the heated electrode, and means for passing the current to be amplified between the heated electrode and the other non-heated electrode. In the earlier use of the electron tube the vacuum was not so high but that considerable ionization of the gases in the tube took place under their bombardment by elec- trons from the heated wire. This tended to magnify the thermionic current. From one point of view this was desirable. On the other hand, no two tubes were apt to be exactly alike in gaseous content, so that if one tube failed a readjustment of circuits was required when it was re- placed. The ionized gas, indeed, acted the part of a second positively charged grid, efficient to reduce nega- tive “space charge” and so to enhance the thermionic current, but not easily replaceable by the ionized gas of a second tube, almost certain to differ essentially from the first. Dr. Irving Langmuir of the General Electric Company, who studied thermionic currents extensively about 1913, described his researches in 1915 (Gen. Elec. Rev., vol. 18, P- 33, 1915). After quoting findings of previous experi- ments up to the year 1913 he says: “We see that there were the best of reasons for be- lieving that it would be impossible to get any electric discharge through a perfect vacuum, because one could not expect to get any electrons from the electrodes.” That is, previous experimenters had been led to the view that the emission by the hot wire was of chemical origin— due to the presence of gases—and not thermal. [61] GREAT INVENTIONS In summing up his own experiments, in which he used a tungsten lamp filament for the hot wire, he goes on to say: It was found that the smallness of the [thermionic] current in a lamp was not due to any failure of the filament to emit electrons, but was due entirely to the inability of the space around the filament to carry the currents with the potential available in the lamp. The explanation of this phenomenon was found to be that the electrons carrying the current between the two electrodes constituted an electric charge in the space, which repelled the electrons escaping from the filament, and caused some of them to return to the filament. . . . . . . Extremely minute traces of gas however, may lead to the formation of a sufficient number of positive ions to neutralize to a large extent the space charge of electrons, and thus very greatly increase the current carrying capacity of the space. For example, a pressure of mercury vapor of about 1/100,000 mm. has, under certain conditions, been found to completely eliminate the effect of space charge, so that a current of 0.1 ampere was obtained with only 25 volts on the anode, whereas without this mercury vapor, over 200 volts were necessary to draw this current through the space. Besides this enormous effect on the carrying capacity of the space, many gases have a great influence on the electron emission from the cathode. But in every case where the cathode is of pure tungsten the effect of the gas is to decrease, rather than increase, the electron emission. For example, it is found that a millionth of a millimeter {about a billionth of atmospheric pressure] of oxygen, or gas containing oxygen, such as water vapor, will cut the electron emission down to a small fraction of that in high vacuum. Further investigation showed that with the elimination of the gas effects, all the irregularities which had previously been thought in- herent in vacuum discharges from hot cathodes were found to dis- appear. These experiments of Langmuir’s and others have shown that these so-called thermionic currents between heated tungsten filaments and positively charged conductors, all contained in highest vacuum, are subject to definite laws. Knowing the dimensions of the conductors, the temperature of the filament, and the voltage of the [ 62] ELECTRONS AND X RAYS positive terminal, the thermionic current can be ac- curately predicted. Without giving formulae, which may be found in textbooks, we may note that, as shown in Figure 17, in a given tube at fixed positive voltage the thermionic current increases with the temperature of the filament up to a definite value, beyond which tem- perature no increase oc- 4g curs. At any given tem- perature the thermionic current rises with increas- ing voltage, but not in- 0 definitely. For at any temperature there will be — go found a critical voltage, SF beyond which no increase eo of voltage will increase § the current. . 40 The explanation of these results is as follows: 20 Though the number of electrons emitted by a Ol gles filament tends to increase Degrees ~ Kelvin indefinitely with the tem- — Fic. 17. Cathode temperature, perature, the presenceofa voltage, and thermionic current. sufficient number of nega- The strength of thermionic cur- tively charged electrons, rent soon reaches a maximum for jean au ; any given voltage, owing to space already thrown out into charge. After Langmuir the vacuum, exerts a repelling influence which prevents the escape of more of them from the filament. This is the so-called “space charge” limitation. Again, at any given temperature a sufficient positive charge on the anode will attract a// the electrons being emitted. Therefore increasing voltage beyond this value will draw no more. On the basis of his experiments Langmuir applied for a patent on improvements of the electron tube amplifier, filed October 16,1913. A typical claim is No. 2, as follows: [ 63 ] GREAT INVENTIONS 2. A discharge tube having a cathode adapted to emit electrons and an anode adapted to receive said emitted electrons, the tube walls being fashioned or shaped to permit the direct passage of a useful pro- portion of said electrons from cathode to anode, the gas content or residue of said tube and the relation of parts of the tube being such that the tube is capable of being so operated in a range below satura- tion and materially above ionization voltages that the space current is governed or limited by the electric field of said electrons substan- tially unaffected by positive ionization. This patent application had a long, rough passage in the Patent Office, but a patent was finally issued on October 20, 1925. Meanwhile, electron tube amplifiers built according to its principles came into use to the exclusion of all others, because they were interchangeable. Such tubes gave uniform results, and were commercially produced to be interchangeable without necessity of special adjustments of the radio circuit on the substitu- tion of one for another. The De Forest Radio Company, however, contested the validity of the Langmuir patent. It was first held invalid, then reaffirmed in courts of appeal. The case reached the Supreme Court, which decided, May 265, 1931, that the Langmuir patent is “He/d invalid as not involving invention over the prior art.” The Court held that a publication of Lilienfeld, in 1910, and remarks of Fleming, in 190, indicated that the advantage of a high vacuum was known to persons skilled in the art before Langmuir; that all other elements of Langmuir’s tube were con- tained in the audion of De Forest. “That the high vacuum tube was an improvement over the low vacuum tube of great importance,” says the Court, “is not open to doubt. Even though the improvement was accomplished by so simple a change in structure as could be brought about by reducing the pressure in the well-known low vacuum tube by a few microns, still it may be invention. Whether it is or not depends upon . . . whether the relationship . . was known in the art when Langmuir began his experiments.” [ 64 ] Auvdwos 91139a[q Jesauey ayy jo Asajinod ‘eqn Avi-y adpifoog usapoyy i A a a a a a eR line Se SS es 8l ALVId PEALE 19 X-ray picture of human head and neck. Courtesy of the General Electric Company ELECTRONS AND X RAYS On this question, as we have seen, the Court decided adversely. The legal niceties and the intellectual interest of such a decision may perhaps be appreciated better by quoting a citation by the United States Court of Customs and Patent Appeals in a case decided February 25, 1931, as follows: PATENTABILITY—INVENTION. A combination of old elements, in order to be patentable, must involve invention. It must produce not only some useful but some new result which goes beyond what may be achieved by mere*mechan- ical skill in operating the elements disclosed by prior art. The Supreme Court held that Langmuir did not do this. Two other General Electric Company devices of great value depending on the properties of the high vacuum electron tube were produced immediately after Langmuir’s experiments. These are the Coolidge X-ray tubes famous in hospital practice, and Dushman’s “kenotron”’ alter- nating-current rectifier. X Rays The Smithsonian Report for the year 1897, among quite a number of extraordinary articles? on physical subjects which would well repay reading at the present time, contained a translation of Prof. W. C. Réntgen’s original observations published in 1895 on the discovery of X rays and their properties. He was not able in these first experiments to determine what they were, hence he called them “X rays,” probably because X is usually an unknown quantity in algebra. Later they were proved to be identical in nature to ordinary light. They are, in short, ? The evolution of satellites, by G. H. Darwin. Electrical advance in the past ten years, by Elihu Thomson. The X-rays, by W. C. Rontgen. Cathode rays, by J. J. Thomson. Story of experiments in mechanical flight, by S. P. Langley. Diamonds, by William Crookes. An undiscovered gas, by William Ramsay. [65] GREAT INVENTIONS waves. But whereas light waves average 50,000 to the inch in length, X rays average 100,000,000. Thus they lie far on the hither side of light rays in the spectrum as compared to radio rays, which are also of similar nature, but whose single waves range from several feet to several thousand feet in length. For lack of proper apparatus to analyze such minute waves, Réntgen did not at first discover these properties, but others have since shown that X rays may be reflected, refracted, diffracted, and polarized, just as light rays can. Roéntgen begins: If the discharge ... be passed through a... tube... con- taining a sufficiently high vacuum, the tube being covered with a close layer of thin black pasteboard and the room darkened, a paper screen covered on one side with barium-platinum cyanide . . . will be seen to glow brightly and fluoresce . . . even when the screen is removed to a distance of 2 meters from the apparatus. The observer may easily satisfy himself that the cause of the fluorescence is to be found at the vacuum tube and at no other part of the electrical circuit. It is thus apparent that there is here an agency which is able to pass through the black pasteboard impenetrable to visible or ultra violet rays from the sun or the electric arc, and having passed through to excite a lively fluorescence, and it is natural to inquire whether other substances can be thus penetrated. I have found that all substances transmit this agency but in a very different degree. He then gives many examples, including glass and several metals, among which he found aluminum very transparent, but lead very opaque. “If,” says Rontgen, “the hand is held between the vacuum tube and the screen, the dark shadow of the bones is seen upon the much lighter shadow outline of the hand.” It is of particular importance from many points of view that photo- graphic dry plates are sensitive to X-rays. . . . The retina of the eye is not sensitive to these rays. Nothing is to be noticed by bringing the eye near the vacuum tube although according to the preceding obser- vations the media of the eye must be sufficiently transmissible to the rays in question. . . Most substances are, like the air, more transmissible for X-rays than for the cathode rays. [ 66 } ELECTRONS AND X RAYS Another very noteworthy difference between the behavior of the cathode rays and the X-rays was exhibited in that I was unable to produce any deviation of the latter by the action of the most powerful magnetic fields. According to the results of experiments particularly directed to discover the source of the X-rays, it is certain that the part of the wall of the discharge tube which most strongly fluoresces is the principal starting point. The X-rays therefore radiate from the place where . . . the cathode rays meet the glass wall. If one diverts the cathode rays within the tube by a magnet, the source of the X-rays is also seen to change its position so that these radiations still proceed from the end points of the cathode rays. . . . I come therefore to the results that the X-rays are not identical with the cathode rays in the glass wall of the vacuum tube. This generating action takes place not only in glass, but as I have observed in apparatus with aluminum walls 2 millimeters thick, exists also for this metal [and others also]. Further on, Réntgen examines the differences of pene- trating power of X rays, which he found to depend on the voltage used to excite the discharge tube. Tubes very highly evacuated, or which became so by long use, requiring high voltage to force the discharge, sent out, he found, very penetrating X rays. Such tubes he called “hard” tubes and those of a less perfect vacuum “soft.” X rays also received the designations “‘hard” and “‘soft” according to their penetrating power. We know now that the “hard” X rays are of shorter wave length than “soft’”’ ones. R6éntgen also constructed tubes in which the cathode rays struck a target of metal placed at an angle of 45° to the direction of the cathode rays. From such a target the X rays could be taken out at right angles to the cathode rays. He also used tubes in which a concave mirror of aluminum was employed as the cathode, in order to focus the cathode rays upon the target. Thus, although he did not know the real nature of X rays, their discoverer within a few months conducted such a fruitful series of experiments as to adequately explore their properties, and he invented excellent means [ 67 GREAT INVENTIONS for their production. The new rays sprang at once into hospital practice. R6ntgen’s discovery has been one of the greatest boons to surgery and medicine ever found, ranking perhaps with Pasteur’s discovery of the roles of bacteria and other germs. The Coolidge X-ray tubes, by furnishing a great in- crease in intensity and available penetrating power, shortened photographic exposures, and made it possible to examine satisfactorily deep-lying human tissues which before were difficult or impossible to portray. Plate 18 shows a modern Coolidge X-ray tube, capable of using a potential of 200,000 volts, owing to the extremely high vacuum and to the considerable length of path employed. Plate 19 shows an X-ray photograph, made with a Coolidge tube, of the head and neck of a man. PracticaLt Use or PROPERTIES OF ATOMIc STRUCTURE For purposes of transmission, alternating current is far superior to direct current, as we noted in Chapter II. But for certain uses only direct current is available; hence, methods have been devised to procure direct from alternating current. One of these consists of the split commutator, as used on direct-current dynamos. The same method is also applied in the rotary transformer, which is an alternating-current motor operating a direct- current dynamo, usually on the same shaft. There are, however, two methods of procuring direct current from alternating current which depend on the properties of atomic structure. One is the Dushman “kenotron” rectifier above mentioned. This device is illustrated in Figure 18. In the high-vacuum tube, 4, spiral spring connections, @, carry taut the hot cathode wire of tungsten, J, , through the axis of the surrounding molybdenum cylinder, c, c, which, supported firmly by connectors, d, d, forms the anode. Sines the cylinder walls lie close to the tungsten filament, only a small drop of [ 68 | ELECTRONS AND X RAYS voltage occurs in forcing a thermionic current across the vacuum gap. If now an alternating current is connected from B to C, whether single or polyphase, only those intervals during which the point B is a negative pole can provide any current, for the cylinder c, c, is so thick as to be always cool and therefore unable to emit electrons. Thus the currentwhich vice though intermittent, direct. Nor is there he loss of energy except that due to the small resistance in the wire and the vacuum gap. For during the instants when the unfavorable phases occur, it is as though a switch in the circuit had been opened. There is then zero cur- rent and zero loss. Thus the efficiency of the Dushman kenotron rec- tifier is high, even at Fichter Dushman’s “kenotron” voltages as low as TOO thermionic rectifier. Only at and becomesevenhigher _ those instants when the alternat- with voltages exceeding ing current is of proper sign can 1,000. The intermittent thermionic currents pass character of the current may be smoothed out by the use of a condenser. As very high voltage currents may be rectified, the kenotron is available for penetrating X-ray tubes, sisy joined to a step-up transformer line. Many kenotrons can be used in parallel circuit together to carry large currents. Another device for extracting direct from three-phase alternating current is the mercury-arc rectifier of Cooper Hewitt. The electric arc differs from the high-vacuum tube discharge in that vapors and gases ionized by the [ 69 | GREAT INVENTIONS electric discharge, and containing not only negative elec- trons but positive ions also, form the conducting medium. The arc persists only when its cathode is at a very high temperature. Its anode may be quite cool. Hence it is not as easy to maintain even a direct-current arc between metals as it is between carbons, because the high conductivity of metals for heat tends to keep the cathode cool. Much more difficult is it to maintain an arc with alternating current between metals, because the 4 poles are alternated, and therefore the cathode has twice as long to cool. Ina vacuum the ordinary arc can not be maintained with alternating current, except with carbon poles, and then Fic. 19. Cooper Hewitt mercury rectifier. Three- phase alternating current connected to three iron elec- trodes in glass bulb, 7. When any one of them be- only with difficulty. Cooper Hewitt, however, conceived the ingenious device shown in Figure 19. The three-phase current comes positive the current flows to the mercury elec- trode at the bottom, and passes as a direct current from a4 toé through circuit, / is brought to the three iron poles within the vacuum tube, T, at the bottom of which is a pool of mercury. Having once started an arc with the mercury as cathode, by the use of a high- voltage direct current for instance, the arc continues to be maintained by the three-phase alternating current because one of the three poles is always positive. But the iron poles, being too cool, are never able to act as cathode, so that only a direct current is passed. Cooper Hewitt also invented a very simple direct- current mercury arc sometimes used for illumination, though imparting a ghastly hue to the human face. Its [70 ] ELECTRONS AND X RAYS light comes from three green lines in the mercury vapor spectrum at wave lengths 5,791, 5,770, and 5,461 Ang- stroms. There are also many mercury-vapor spectrum lines in the ultra-violet which strongly affect the photo- graphic plate. Hence the mercury arc is used very extensively in photography and for experimental purposes. The Cooper Hewitt mercury arc is contained in a long, inclined glass tube with electrodes at the bottom and top. It is started by merely tipping the vacuum tube till the liquid mercury makes contact from one electrode to the other. Afterwards the arc continues to operate over the entire tube even though the electrodes are long distances apart. There is, perhaps, not a very clear distinction between the operation of the Cooper Hewitt mercury arc and the operation of the glow tubes now coming into general use for illumination and advertising. Yet there is this differ- ence, that whereas the mercury-arc tube becomes hot and is thereby filled with mercury vapor at considerable pressure, the long glow-tube illuminators operate always at low pressure, though not at high vacuum conditions. In both cases the conductor of electricity consists of a mixture of negative electrons and ionized molecules. In Chapter V we shall see some applications of the properties of atoms to wireless signaling. [71] CHAPTER IV TELEGRAPHY AND TELEPHONY Wuite still a young teacher at Albany Academy, Joseph Henry, later to be the first Secretary of the Smithsonian Institution, made valuable inventions. He constructed electromagnets far more powerful than any that had been made before. They were of two kinds, which he called “quantity magnets” and “intensity magnets,” respec- tively. In the former the soft-iron core was wrapped with a few turns of wire carrying a strong electric current. In the latter there were very many turns of fine wire about the core, and a feebler current could then produce a powerful effect. To enable him to superpose many layers of wire without short-circuiting, he wound the copper wire with silk thread, for insulated wire as we purchase it now commercially was then unknown. Henry constructed an electromagnet for Yale College in the year 1831 (Plate 20, upper) which sustained 2,063 pounds, and later another for Princeton which sustained 3,500 pounds. Earty Work on ELeEctTric SIGNALING He was interested in the application of magnets for both the electric motor and the electromagnetic telegraph. The United States National Museum has a model of Henry’s electromagnetic oscillating motor of 1831 (Plate 20, lower). An iron core shaped like an inverted U was pivoted centrally and wound in opposite directions with two coils, whose ends could dip into mercury cups con- nected to two battery cells. Two permanent bar magnets were placed beneath the ends of the iron core, each with ee PLATE 20 Upper: Henry’s Yale magnet, which supported 2,063 pounds. Lower: enry’s electromagnetic oscillating motor TELEGRAPHY AND TELEPHONY its north pole uppermost. When the iron core was tilted so as to make contact of the ends of one coil through the mercury cups with one of the cells, it became magnetic and was immediately repelled so as to tilt toward the other cell and make contact there. So the rocking motions continued indefinitely with about 75 tilts per minute. More important than this electromagnetic engine was Henry’s telegraphic experiment. He connected an electric Fic. 20. Henry’s electromagnetic telegraph operated at Albany, N. Y., as early as 1831, through a mile of line wire battery by means of a wire a mile long to one of his horse- shoe intensity electromagnets. A permanent pivoted magnet had one of its ends between the poles of the electro- magnet, as shown in Figure 20. The other end tapped a bell when the circuit was completed. This experiment Henry made successfully while still at the Albany Acad- emy. He used a similar device after his removal to Princeton University to communicate from his laboratory to his house. Said Henry in his statement on the early history of the telegraph!: Previous to my going to Princeton in November, 1832, my mind was much occupied with the subject of the telegraph, and... I introduced it in my course of instruction to the senior class in the Academy. I should state, however, that the arrangement I have described was merely a temporary one, and that I had no idea at the 1 Ann. Rep. Smithsonian Inst. for 1857, pp. 99-106, 1858. [73] GREAT INVENTIONS time of abandoning my researches for the practical application of the telegraph. Indeed, my experiments on the transmission of power to a distance were suspended by the investigation of the remarkable phenomena (which I had discovered in the course of these experiments) of the induction of a current in a long wire on itself, and of which I made the first mention in a paper in Silliman’s Journal in 1832.2 Joseph Henry’s discoveries on electric induction and self-induction are so important for telegraphy, telephony, and wireless, that we may well summarize them before going on to Wheatstone’s and Morse’s telegraphic inven- tions and other subjects. This course is the more appro- priate in this Smithsonian Scientific Series because Henry, as its first Secretary, laid the foundations of the policy of the Smithsonian Institution and established its great reputation. His important experiments on induction and self-induction are described by him in several papers delivered before the American Philosophical Society at Philadelphia in the years 1835, 1838, and 1840, and re- published in the Smithsonian Miscellaneous Collections, Volume 30, pages 92-188, 1887. First of all, in his paper read February 5, 1835, he quotes the passage already cited announcing his discovery of 1831 as follows: In the American Fournal of Science for July, 1832, I announced a fact in Galvanism which I believe had never before been published. The same fact however appears to have been since observed by Mr. Faraday, and has lately been noticed by him in the November number of the London and Edinburgh Fournal of Science for 1834. The phenomenon as described by me is as follows: ““When a small battery is moderately excited by diluted acid, and its poles, terminated by cups of mercury, are connected by a copper wire not more than a foot in length, no spark is perceived when the connection is either formed or broken; but if a wire thirty or forty feet long be used instead of the short wire, though no spark will be perceptible when the con- nection is made, yet when it is broken by drawing one end of the wire from its cup of mercury, a vivid spark is produced. If the action of the battery be very intense, a spark will be given by a short wire; in this case it is only necessary to wait a few minutes until the action partially subsides, and until no more sparks are given from the wire; 2 Silliman’s Amer. Journ. Sci., vol. 22, p. 408, July, 1832. [74] TELEGRAPHY AND TELEPHONY if the long wire be now substituted a spark will be again obtained. The effect appears somewhat increased by coiling the wire into a helix; it seems also to depend in some measure on the length and thickness of the wire. I can account for these phenomena only by supposing the long wire to become charged with electricity, which by its re-action on itself projects a spark when the connection is broken.” 3 The above was published immediately before my removal from Albany to Princeton, and new duties interrupted for a time the further prosecution of the subject. I have however been able during the past year to resume in part my investigations, and among others, have made a number of observations and experiments which develop some new circumstances in reference to this curious phenomenon. In his experiments on electric induction Professor Henry used batteries in which copper and zinc plates were dipped in acid. In some experiments he employed a large number of battery cells. The electric current was con- ducted into wires and flat ribbons of copper, insulated when necessary to prevent short-circuits by windings of silk thread or ribbons of silk which separated the con- volutions of his coils. His accounts of his experiments are very clear and interesting but quite too voluminous to reproduce here in his own words except in a few specially important instances. Summarizing them he found the following valuable results: 1. When the poles of the battery are connected by a short wire there is no spark on making or breaking circuit unless the battery has many cells. But when a long wire is substituted, although there may be no spark on making circuit, a considerable spark occurs on breaking circuit. This is Henry’s original discovery of self-induction. His name is used for its unit. 2. If the long wire is wrapped to form a coil, the spark on breaking circuit is augmented, and still more augmented if the coil contains an iron core. But if the wire is first doubled and then wound into a coil there is no spark. 3. Employing a little spiral in which could be thrust a sewing needle, Henry readily magnetized needles by the 3 Silliman’s Amer. Journ. Sci., vol. 22, p. 408, July, 1832. [75] GREAT INVENTIONS current, and used this device to indicate currents and their directions in succeeding experiments. 4. Having a current readily made or broken in one coil, he laid thereon a sheet of glass on which he laid a second coil in no wise connected with the first coil by a metallic connection. This secondary coil could be connected with a galvanometer or the magnetizing spiral. 5. At the instant of making circuit and at the instant of breaking circuit in the primary coil, currents were pro- duced in the secondary coil. But while a current was flowing steadily in the primary coil there was no current in the secondary. 6. Two primary coils and also two secondary coils of different lengths but equal weight were employed. With the long coil of one and a quarter miles of wire as sec- ondary, the secondary current on breaking the primary circuit was so feeble that it gave no sensible magnetizing or galvanometric action, but when 56 students joined hands to complete its circuit they received a smart shock when the primary current was broken. On the other hand when the short secondary coil was used the galvanometer and magnetizing coil showed strong current effects. By ex- changing primary coils it was found that a long primary could induce large currents in a short secondary, and a short primary could induce heavy shocks in a long sec- ondary. In Henry’s own words: “This experiment was considered of so much importance, that it was varied and repeated many times, but always with the same result; it therefore establishes the fact that an ‘intensity’ current can induce one of ‘quantity’, and, by the preceding experiments, the converse has also been shown, that a ‘quantity’ current can induce one of ‘intensity’. ‘These are the principles of the step-down and step-up transformers sc important in modern engineering. 7. Henry found that secondary induction could be detected at considerable distances. He was also able to demonstrate tertiary and higher orders of induction. Thus [ 76 ] TELEGRAPHY AND TELEPHONY when the terminals of his secondary coil were brought out to a distance of several feet, he joined them to the termi- nals of another coil. Upon this he placed a glass plate, which supported a fourth coil. To this he connected a galvanometer or the magnetizing spiral and found tertiary induced currents. The same principle he extended to show induction of the fifth order. In these experiments he determined by aid of the magnetizing spiral the directions of the currents of induction. He found the inductions which occur at breaking the primary circuit took the fol- lowing directions: Primaryacurrentys2 0%. Sr aes == SECOMG ALY: CUREENE oi say syria ois. o3s . Current of the third order...... a Current of the fourth order....-+ Current of the fifth order...... These signs alternate except the first two. It is there- fore to be concluded, in the words of Henry: “During the continuance of the primary current in full quantity, no inductive action is exerted. But when the same current begins to decline in quantity, and during the whole time of its diminishing, an induced current is produced in an opposite direction to the induced current at the beginning of the primary current.” 8. Henry found that when he substituted a metal plate for the glass plate between his primary and secondary coils the shock from the secondary on breaking the primary circuit disappeared. But if he cut a radial slot in the metal plate there was no such screening effect. Nor did it return when he placed a second glass plate on the metal plate and a second slotted metal plate on the second glass with the two slots not superposed. Although shock could be screened from the secondary by a full metal plate, nevertheless the galvanometer still responded to the sec- ondary, showing that the screening was not complete. Deg GREAT INVENTIONS g. He discovered the oscillatory character of the dis- charge of a Leyden jar, of which he states as follows: The discharge, whatever may be its nature, is not correctly repre- sented (employing for simplicity the theory of Franklin) by the single transfer of an imponderable fluid from one side of the jar to the other; the phenomena require us to admit the existence of a principal discharge in one direction, and then several reflex actions backward and forward, each more feeble than the preceding, until the equilibrium is obtained. All the facts are shown to be in accordance with this hypothesis, and a ready explanation is afforded by it of a number of phenomena which are to be found in the older works on electricity, but which have until this time remained unexplained. Henry foreshadowed wireless, for he says: In extending the researches relative to this part of the investiga- tions, a remarkable result was obtained in regard to the distance at which inductive effects are produced by a very small quantity of electricity; a single spark from the prime conductor of the [frictional electrical] machine, of about an inch long, thrown on the end of a circuit of wire in an upper room, produced an induction sufficiently powerful to magnetize needles in a parallel circuit of wire placed in the cellar beneath, at a perpendicular distance of thirty feet with two floors and ceilings, each fourteen inches thick, intervening. We shall see presently the important applications of these discoveries of Henry in connection with telegraphy, telephony, and wireless. Tue First CoMMERCIAL TELEGRAPH Sir Charles Wheatstone, that great English experi- mental genius, took out a patent for the electric telegraph in 1837. With his partner, Mr. Cooke, he first worked a railway telegraph circuit on July 27, 1837, for a distance of 14% miles between Euston and Camden Town, stations near London. Though successful, neither the railway officials nor the public were at first favorably impressed, so that for several years after this the railway signals were preferably transmitted between Euston and Camden by whistling through a tube. But the Great Western Rail- way, more favorably impressed by the telegraph, erected NGccul TELEGRAPHY AND TELEPHONY a line from the Paddington terminus to West Drayton, 13 miles, in 1839, and continued it to Slough in 1841. For- tunately this line had an early piece of sensational adver- tising by the capture of the murderer, Tawell. This man, dressed in Quaker garb, killed a woman named Sarah Hart at Salt Hill, and was observed to take a slow train to London. The police telegraphed Paddington, but the word Quaker nearly baffled the telegraph, for the Wheat- stone five-needle instrument had no sign for Q. Several times the operator got as far as ““Kwa’” only to be asked to repeat. But a boy at Paddington said, “Let him finish the word.” When it was spelled out as ““Kwaker” they understood, and shadowed Tawell as he got down from the train. He was arrested, tried, and executed, and as the case showed in a spectacular way the merit of the telegraph, it hastened the spread of telegraphy in England. While Wheatstone’s telegraph was probably the first ever used for commercial purposes, many inventors had employed electricity previously to transmit signals. Sug- gestions were made indeed as early as 1753 for employing the influence of the Leyden jar, operating through many conductors, to attract small pieces of paper and thus indi- cate the letters of the alphabet. Sdmmering, Schweigger, and Coxe all worked out methods based on the chemical action of the electric current prior to 1820. Following Oersted’s discovery in 1820 of the deflection of the mag- netic needle by the electric current, there came investiga- tions by Ampére, Triboaillet, and Schilling. Cooke, Sir Charles Wheatstone’s partner, was interested by the work of Schilling and invented a three-needle instrument in 1836. Wheatstone’s first modification of Cooke’s device employed five vertical needles, each influenced by a separate electric coil, and made to point out letters on a dial. This telegraph required six line wires. Steinheil in Germany invented in 1837 a telegraph employing Fara- [79] GREAT INVENTIONS day’s principle of electromagnetic induction, and also produced an ink-printing recorder of the messages. The English Postal Telegraph system is founded largely on the work of Wheatstone, who in 1868 was knighted for his invention of the automatic telegraph, by means of which as many as 500 words may be transmitted per minute. By a development of the invention of Bain in 1846, the letters are indicated by holes punched in definite relations through a moving ribbon of paper and are printed in accord therewith by an inking device invented by Thomas John, an Austrian engineer, in 1854. In operating this telegraph, positive and negative currents are sent alternately into the line. The mechanisms used in punch- ing, sending, receiving, inking, etc., are naturally very complicated. The American commercial systems of telegraphy de- veloped, as is well known, from the work of Prof. Samuel F. B. Morse (1791-1872). He was the son of a Congre- gational minister, and grandson of Samuel Finley, Presi- dent of the College of New Jersey. He graduated from Yale College in 1810, but studied art with Washington Allston, and accompanied him to England where he had considerable success as a painter. Becoming a founder of the National Academy of Design, he was its first president from 1820 to 1845. He takes a high place among American artists. It was not until 1832 that he began to work upon the electromagnetic telegraph. The idea occurred to him while in Paris, and became his absorbing preoccupation until his success in 1844. He completed a working inven- tion in 1836 which he exhibited at the University of the City of New York, operating a circuit of 1,700 feet. Judge Stephen Vail, of Morristown, N. J., and his son Alfred Vail, became deeply interested and associated themselves with Morse. At this time Morse was in sore straits of poverty, deny- ing himself the necessities of life in order to purchase parts for his apparatus. After applying for his patent, April 7, [80] PLATE 21 Samuel F. B. Morse, who commercially developed the telegraph in America UOJSUIYSLAA OF asounjyeg “bret ‘hz Avy ‘adessour d1ydvsso]9} Is1OP SIL] :1OMO'T ‘ddIAap Surpuas s assoyy Jo papoyy :4oddq O° wt Mm (ral FER ¥ 2 wrtoy For 7 Lege soe é frperiae ma keryren.g Teesriy 10 toy ome "I~ co ALV Id TELEGRAPHY AND TELEPHONY 1838, which was granted June 20, 1840, he endeavored to obtain an appropriation from Congress to test the tele- graph on a considerable scale. Though favorably re- ported from committee, Morse’s bill did not pass until 1843. A telegraph was constructed from Washington to Baltimore, and first publicly used by him on May 24, 1844. Its first message was: “What hath God wrought?” Reissues of Morse’s patent, clarifying its specifications and claims in more terse and precise form, were granted January 15, 1846 and June 13, 1848. The following claims I, 4, 5 and 8, which were allowed, are of primary interest as expressing the extent of Morse’s invention. 1. Making use of the motive power of magnetism when developed by the action of such current or currents, substantially as set forth in the foregoing description of the first principal part of my invention, as means of operating or giving motion to machinery which may be used to imprint signals upon paper or other suitable material, or to produce sounds in any desired manner for the purpose of telegraphic communication at any distances. (The only ways in which the galvanic current had been proposed to be used prior to my invention and improvement were by bubbles resulting from decomposition and the action or exercise of electrical power upon a magnetized bar or needle and the bubbles, and the deflections of the needles thus produced were the subjects of inspection, and had no power, or were not applied to record the communication. I therefore characterize my invention as the first recording or printing telegraph by means of electro-mag- netism. There are various known modes of producing motions by electro-magnetism; but none of these had been applied prior to my invention and improvement to actuate or give motion to printing or recording machinery, which is the chief point of my invention and improvement.) 4. The combination of two or more galvanic or electric circuits with independent batteries, substantially by the means herein de- scribed, for the purpose of obviating the diminished force of electro- magnetism in long circuits, and enabling me to command sufficient power to put in motion registering or recording machinery at any distances. 5. The system of signs consisting of dots and spaces, and of dots, spaces, and horizontal lines, for numerals, letters, words, or sentences, substantially as herein set forth and illustrated, for telegraphic pur- poses. [81] GREAT INVENTIONS 8. I do not propose to limit myself to the specific machinery or parts of machinery described in the foregoing specification and claims, the essence of my invention being the use of the motive power of the electric or galvanic current, which I call “electro-magnetism,” how- ever developed, for marking or printing intelligible characters, signs, or letters at any distances, being a new application of that power of which I claim to be the first inventor or discoverer. Thus it appears that Morse recognized the existence of various other forms of telegraph in the prior art, but particularly insisted on his priority as the inventor of a printing or embossing recording telegraph. He also claims the relay, a feature indispensable to any long distance line. But the device which, far more than any other, has perpetuated the influence of Morse, is the system of dots and dashes to represent letters and numbers and code words. This feature has penetrated into every telegraphic system in all countries, excepting the limited A.B.C. telegraphic system of Wheatstone, wherein the letters themselves are indicated by a pointer upon a dial, and the needle system of Wheatstone wherein the direction of displacement, not the time of displacement, of a needle is observed. The International Morse code differs a little from Morse’s original code, so as to make provision for those letters or letter combinations, very common in foreign languages, but not in English. In the most modern practice, messages are printed in ordinary letters, so that the use of the code has diminished. Claim 8 was overthrown in one of the most important patent decisions ever rendered by the Supreme Court of the United States. In substance the Court held that no man may patent a law of nature. Certain passages from the decision follow. O’Reilly et al. v. Morse et al. We perceive no well-founded objection to the description which is given of the whole invention and its separate parts, nor to his [Morse’s] right to a patent for the first seven inventions set forth in the specifi- cation of his claims. The difficulty arises on the eighth. It is in the following words: [ 82 ] TELEGRAPHY AND TELEPHONY “Eighth. I do not propose to limit myself to the specific machinery or parts of machinery described in the foregoing specification and claims; the essence of my invention being the use of the motive power of the electric or galvanic current, which I call electro-magnetism, however developed, for marking or printing intelligible characters, signs, or letters, at any distances, being a new application of that power of which J claim to be the first inventor or discoverer.” It is impossible to misunderstand the extent of this claim. He claims the exclusive right to every improvement where the motive power is the electric or galvanic current, and the result is the marking or printing intelligible characters, signs, or letters at a distance. If this claim can be maintained, it matters not by what process or machinery the result is accomplished. For aught that we now know some future inventor, in the onward march of science, may discover a mode of writing or printing at a distance by means of the electric or galvanic current, without using any part of the process or combination set forth in the plaintiff’s specification. His invention may be less complicated—less liable to get out of order—less expensive in con- struction, and in its operation. But yet if it is covered by this patent the inventor could not use it, nor the public have the benefit of it without the permission of this patentee. Nor is this all, while he shuts the door against inventions of other persons, the patentee would be able to avail himself of new discoveries in the properties and powers of electro-magnetism which scientific men might bring to light. For he says he does not confine his claim to the machinery or parts of machinery, which he specifies; but claims for himself a monopoly in its use, however developed, for the purpose of printing at a distance. New discoveries in physical science may enable him to combine it with new agents and new elements, and by that means attain the object in a manner superior to the present process and altogether different from it. And if he can secure the exclusive use by his present patent he may vary it with every new discovery and development of the science, and need place no descrip- tion of the new manner, process, or machinery, upon the records of the patent office. And when his patent expires, the public must apply to him to learn what it is. In fine he claims an exclusive right to use a manner and process which he has not described and indeed had not invented, and therefore could not describe when he obtained his patent. The court is of opinion that the claim is too broad, and not warranted by law. Plate 22 shows a photograph of a model of the Morse sending device which he called the port rule, and a copy of the first message sent between Baltimore and [83] GREAT INVENTIONS Washington, “What hath God wrought?” Figure 21 shows how the Morse alphabet was arranged, and some later changes which have come into it. Figure 22 shows a diagram of the sending and receiving arrangements of Morse. The original receiving instrument is on exhibition in the United States National Museum. The message to Pra we Ma Sa a eee ee ee e ee eee @ e e@ @0@60@ e¢e8 @ @eees ea — 9 == ———— = @@e = @ ee eeece eo o= @ ee SET Iw A-** 1S THE PRESENT S | M——* IS THE PRESENT O et ee S Y|N- ~~ SAME Geree wi ion ise . R|O- IS THE PRESENT 1 Dee ee . « Z P osece SAME Es SAME Oe : Fees is THEPRESENT & | R°* IS THE PRESENT O G: ° - e . (e Ss oume~ . ° . F Hees SAME Yara “ : G (c=) ISSTHE PRESENT “A OU) * LF : Ww J ese « - . Cc V — . e Py T K--- SAME Wises Usd i U Lie ale Mcrae ye ce/t Fic. 21. Morse code alphabet and later changes in the international code. Morse’s “port rule” arrangement ts shown above be sent was first set up on the port rule, m. By turning the wheel, Z, the port rule vibrated the lever, P, thereby making and breaking contacts, K. The line current thus made and broken operated electromagnets, 4, which vibrated the pendulum, F, thereby marking with pencil or embossing the paper rolling from 4 over the wheel, B, to C, as drawn along by the clockwork, D. [84] TELEGRAPHY AND TELEPHONY Fic. 22. Diagram of Morse sending and receiving instruments. The “port rule” for sending, shown below, produces intermittent currents in the line. These operate a magnet, which draws over a pendulum carrying a point that embosses the paper record fed along by clockwork. A relay may be interposed to strengthen the action [85] GREAT INVENTIONS Telegraphy is a good example of our common experience that the complex leads frequently to the simple. For the embossing recording telegraph of Morse yielded generally, after the operators got experience, to the simple sounder which has held a large place in American telegraphic practice, though recently largely superseded by the type-printing telegraph. The dot and dash signals of the Morse code can be easily recognized by the experienced ear in the chattering of the lever of the simple electro- magnet as it vibrates between its stops, though these sounds are quite unintelligible to the uninitiated. The exclusively Morse features in this ordinary application of telegraphy are his dot-and-dash code and his relay.‘ The electromagnets of intensity and quantity employed in the modern telegraph come to us from Joseph Henry’s earliest inventions, and back of them lie the discoveries of Oersted, Arago, and Sturgeon. In the A.B.C. system of Wheatstone, the principle of induction, as discovered by Faraday, is employed directly to produce the line current instead of a battery or other independent current generator. Bain in 1846 employed the chemical action of the electric current to print signals by conducting the line current directly through moving sensitized paper. His recording system, though mechan- ically far simpler than those of Morse and of Wheatstone, and though it could dispense with the relay owing to its extreme sensitiveness, has never come into general use, and is employed now, if at all, only in laboratory experi- ments. A principal item of cost in telegraphy is, of course, the line. But it was early discovered that the earth, even without lakes or streams, is a return circuit of practically zero resistance. Yet the cost of a long single line is so great that ingenious devices were invented whereby first two (duplex), then four (quadruplex), and finally numer- 4 Henry was early acquainted with the principle of the relay, but no description of it appears in his publications. [ 86 ] TELEGRAPHY AND TELEPHONY ous (multiplex) messages could be transmitted over the same circuit at the same time. A system of duplexing is indicated in Figure 23. The electromagnets are doubly wound in opposite directions with equal coils. Also a second circuit is provided at each station with a resistance r, r’, equal to that of the line, 7, Then when the operator A 7 B * o- -oe s ooo Swen ne Pen ec. - -- We enncwo-?” e of : *. od 2°" Fic. 23. Duplex telegraph diagram at 4 presses the key, K, it produces no effect on his own instrument, /, because two equal currents in opposite directions are being sent. Not so, however, with the electromagnet, E’, at B, where the line only is furnishing current. If at both 4 and B the operators are sending, then the current in the line is stopped by equal and opposite impulses, leaving operative the local circuits only. Therefore the instrument, E, is affected just as long as the key, K’, at B is held down, not, to be sure, by the battery at B, but by that at 4, which, however, answers the same purpose. Similarly with the instrument at Be Multiplex telegraphy was perfected from an invention by Meyer in 1873. It depends on quite different principles [37] GREAT INVENTIONS from duplexing. If two disks at the distantly separated stations can be caused to rotate in exact unison or syn- chronism, these disks may be subdivided into a consider- able number of segments, each of which is given to one sending operator, who can send to the line while his segment is in contact. His partner, the receiving operator at the other station, receives the messages through his segment of the disk at his station. As the inertia of the telegraph instruments is considerable, the intermittent connections rapidly following each other thus established are sufficient for telegraphing. The whole difficulty lies in exact synchronism, but this has been largely overcome. In recent times multiplex telegraphy has been accom- plished in a still different way. Alternating currents of various frequencies are employed, one frequency for each operator. On the line all of these frequencies are superposed to form a very complex wave, much as white light is composed of a combination of the rainbow colors, or as the many broadcasting stations constantly send their various frequencies at the same time through the same space. At the receiving station the frequencies are again separated by tuning, much as white light is sepa- rated into colors by a prism, or, more exactly, as individual radio broadcasting stations are isolated at pleasure by the listener. In this way the numerous messages are unraveled and taken by separate operators or recording instruments. By thermionic tube amplifiers the alternat- ing current may be rectified into direct currents and amplified as desired so as to be received by ordinary telegraph instruments. The system has sometimes been described as “wired wireless.” It is duplexed and as many as IO messages each way may thus be transmitted at once by one wire. Within the last 25 years the printing telegraph has largely superseded all others in America, so that about 70 per cent of all telegraphy is printed out in ordinary letters without the use of dots or dashes. Plate 23 shows [ 88 ] PLATE 23 ee ot The printing telegraph sender. Courtesy of the Western Union Telegraph Company PLATE 24 Cyrus W. Field. Portrait by Daniel Huntington. Photograph lent by the Metropolitan Museum of Art TELEGRAPHY AND TELEPHONY the complicated instrument employed. In direct print- ing, the paper ribbon usually employed is punched with a central line of holes, making it in effect a chain to be carried without slip, like a bicycle chain. On either side of this central line are spaces of sufficient width so that the paper may be punched with any desired number of holes, up to five, along lines at right angles to its length. Each such line of holes represents a letter or symbol. According to the number of such holes and their position f=) KS iy > Eu > 4 z yuo. UEsEE -2:5352£88().,9014257;276"G NESS LOWRR ABCDEFGHIJKLMNOPQRSTUVWXYZO55. 0 i] [ © e e@e0@ ee FEED HOLES eoseeree e bs pie Seg es. 3 - 26868 Se e e r4 = e Fic. 24. A code-punched paper ribbon used in the modern printing telegraph above or below the center of the ribbon, the different letters of the alphabet are indicated. The message is thus punched on the ribbon of paper by the operator using the typewriter keyboard. As thus coded the message is sent by the automatic telegraph. From the order of the punched holes the instrument at the distant station writes out the message in ordinary letters on a ribbon of paper which may be pasted on a telegraph blank. Many inventors have contributed to this improvement, but prominent among them were Hughes, who secured the synchronous operation of the sending and receiving apparatus, and Baudot, who invented the five-punch code of letters and symbols shown in Figure 24. THE CABLE When the telegraph had become established in many countries, there arose a desire to connect the continents. But when cables began to be laid under the narrower bodies of water, various difficulties that were not very [89] GREAT INVENTIONS serious on land lines began to take on a new importance. Among the most serious were those depending on the great length between stations. First of all, as Joseph Henry’s experiments had shown, the self-induction of a conductor increases with its length, and with it the time required to build up a current and also the intensity of the shock on breaking circuit. Thus a twofold obstacle arose from self- induction. First, there was a great slowing up of each signal in the making by reason of the time required for the current to overcome the opposing current of self-induction. Second, there were the high potential sparks formed on breaking circuit. But quite as serious as self-induction was the electro- static capacity of the cable. A century before, in 1745, von Kleist, dean of the cathedral at Kamin, and Cuneus, a rich burger of Kamin, and Musschenbrock, a professor at Leyden, had all independently conceived the idea that electricity could be stored. Holding a glass jar of water in the hand, each had led into it the discharge of a frictional electric machine. Happening to touch the conducting wire with the other hand, the dean, the burger, and the professor had each received a disagreeable shock. Later, a Doctor Bevis discovered that it was not the water but the glass jar that was the storer of the electricity. All that was needed was a conductor without, a conductor within, and a thin layer of nonconductor separating them. Once charged, the conductors could both be removed, leaving the electricities of opposite sign on the outer and inner surfaces of the nonconducting layer. Thus the Leyden jar was invented. It is a glass jar with tinfoil coatings outside and inside, and a conductor leading to the inner coating. The property of storing electricity possessed by such an instrument is called capacity. Instruments of measured capacity are now made with mica, air, glass, oil, or other substances as insulators between plate con- ductors. An ocean cable has great capacity. For the water out- [90] TELEGRAPHY AND TELEPHONY side and the wires within are conductors separated by rubber insulation. Accordingly, each time a signal is in the making, the cable has to be charged as a condenser. This constitutes another hindrance to cable telegraphy. A third electrical difficulty resides in the difference of electric potential existing between widely separated stations on the earth. This produces strong earth currents through any conductor laid between them. Finally, there occurs considerable leakage of electricity in such a very long line as the Atlantic cable, surrounded as it is by salt water—a good conductor. In addition to these electrical difficulties there were encountered immense mechanical and financial difficul- ties in laying a 2,000-mile cable upon the mountainous ocean floor from ships tossed by great waves upon the surface. The electrical difficulties eventually yielded to the great ingenuity and technical knowledge of Sir William Thomson (Lord Kelvin), C. F. Varley, and others. The costly mechanical ones were overcome, after several fail- ures, owing to the undismayed enthusiasm of Cyrus W. Field of New York, Sir Charles Bright, Sir John Pender, and others in England. Millions were spent in organizing company after company, and enlisting the cooperation again and again of the governments of Great Britain and the United States. Mr. Field crossed the ocean 64 times in this enterprise, suffering severely from seasickness on each occasion. We may well pause a little to recall the plucky story of the Atlantic cable, which has meant so much in bringing the nations together, conducting inter- national business, and on countless occasions softening the anxieties of families separated by the great ocean. Cyrus West Field (1819-1892) was the son of the Reverend David Dudley Field of Stockbridge, Mass., and brother of the eminent jurist, David Dudley Field. Asa boy and young man he served as a clerk, but in 1840 he engaged in making paper in partnership with E. Root & Company in New York. The firm failed, however, and [91] GREAT INVENTIONS Field then formed a partnership with his brother-in-law, made money, paid off the debts of Root & Company, and retired in 1853, a fairly wealthy man. In 1854 he became interested in the project of F. N. Gisborne, an able English engineer, for a telegraph from America to New- foundland. Then he conceived the idea of a transatlantic cable, and after obtaining the favorable reports of Prof. S. F. B. Morse and of Matthew F. Maury, the astronomer and navigator, he acquired all the advantageous cable- landing sites available, and organized the first of his cable companies in 1854. Then he went to England and made an agreement in 1856 with J. W. Brett and Mr. (afterwards Sir Charles) Bright as follows: “Mutually and on equal terms we engage to exert ourselves for the purpose of forming a company for establishing and working of electric telegraphic communication between Newfound- land and Ireland, such company to be called the Atlantic Telegraph Company, or by such other name as the parties hereto shall jointly agree upon.” The enterprise proved far more attractive to English than to American subscribers. Although Field exerted himself to the utmost he could raise in America only about one twelfth of the capital sum of £350,000 thought necessary for the first venture. Similarly in the subse- quent attempts, which finally won out in 1866, the funds subscribed were almost wholly raised in Great Britain. For although Field aroused great enthusiasm in various American cities, the enthusiasm was backed by very few subscriptions. The governments of both nations aided extensively by furnishing naval vessels for long periods to lay cable and act as tenders and guards. For the success- ful cables laid in 1866, however, the Great Eastern of 22,000 tons burden, an enormous ship for those times, was employed to lay the cables from coast tocoast. The cable- laying ships were attended by a warship, which on several occasions proved of great service in firing shots to warn off merchantmen who came near to causing disasters [92] TELEGRAPHY AND TELEPHONY through ignorance of the necessity of the cable ship going steadily ahead. The first cable was begun in England in February, 1857, and its halves were loaded on board the British warship Agamemnon and the American warship Niagara in July, 1857. It was intended as an act of international good will that the Niagara, beginning at Valencia in Ireland, should lay to the ocean’s center, and the American end should there be spliced on and laid to Newfoundland by the Agamemnon. The cable was landed at Valencia on August 5, and everything wentwell until the cable snapped in about 2,000 fathoms at 3:45 o’clock, August 11. The disaster was attributed to inexpert handling of the brake mechanism. Three hundred and eighty miles of cable had been laid. It was not so easy to raise £100,000 additional capital for the second trial. The chorus of pessimism and ridicule had become very loud. However, the company went on, improved its machinery for paying out the cable, con- structed a large additional supply of cable, made a trial cable-laying trip in the Bay of Biscay, and finally left Plymouth on June 3, 1858. It was now intended that the vessels should proceed together to mid-ocean, splice the cable there, and lay both ways at once. But on the way a frightful storm arose. The heavily loaded Agamemnon, smaller than the Niagara, suffered greatly, and on many occasions during the 10-day gale was in extreme danger of foundering. At one time it seemed almost necessary to heave overboard a large coil of the cable. A great length of it was snarled. A hundred tons of coal was carried away from its storage and slid to and fro upon the decks, injuring many. Forty men were in hospital. Water flooded the ship. But at last all the vessels reached the rendezvous in calm weather. The splice was made, but a break came before 10 miles of cable had run out. A second trial was made at once, but after 40 miles had been laid a new break came. For the third time the ships returned, respliced the cable, and [93 ] GREAT INVENTIONS agreed that if more than 100 miles should have been laid by either ship, and a new break should then come, they would return to Great Britian. This time things went for a time more successfully, but the fatal break came again after 146 miles had been paid out by the Agamemnon. She feared the Niagara might not return to England on so close a margin to 100 miles as this, and though short of coal beat back to the rendezvous. But the Niagara was not there, and after several days of waiting all the ships returned to England. At the meeting of the board of directors there was evinced a feeling of despair. The chairman of the board recommended liquidation. But bolder counsels prevailed. The chairman resigned, and was succeeded by Mr. Stuart Wortley. As it was still summer and there was still enough cable, the ships were dispatched once more on July 17, 1858. The rendezvous was reached on July 28, and cable- laying was begun at 12:30 o’clock on July 29. Electrical communication was suspended a little while at about 8 o’clock owing to trouble with the apparatus on the Niagara. This caused great consternation on the 4gamem- non. The cable was cut and respliced in attempting to locate the break, but in the midst of the excitement com- munication returned, and the voyages continued. Plate 25 shows the 4gamemnon engaged in cable laying in 1858. A gale sprung up on July 31, and only by the most un- remitting care could the cable be preserved during the next few days. With various disturbing incidents, but no disasters, the ships proceeded, until on Thursday, August 5, the ends of the first successful cable were landed in the Old World and the New. Its total length was 2,022 miles. The chief engineer, Charles Bright, telegraphed the directors: ““Valencia, August 5th. The Agamemnon has arrived at Valencia, and we are about to land the end of the cable. The Niagara is in Trinity Bay, Newfoundland. There are good signals between the ships.” [94] Aatpnq yraqoy Aq Sunuieg ‘duly ay} SUISSOID JTVYM YW “Seg Ul s[qvo onuEPYy sy) Sutky] uoumauvsp “SH S¢ HLV Id 9? ALV Id en TELEGRAPHY AND TELEPHONY Great Britain and America went wild with rejoicing. Bright was immediately honored with knighthood. Preparations were begun for intercommunication by public officials between the two countries. Unfortunately the chief electrician, Mr. Whitehouse, thought it neces- sary to work with high-potential currents, and even used 2,000 volts ineffectually. After a week of these experi- ments, during which the cable was ruined, a return was made to the delicate methods of Sir William Thomson which had been used during the cable-laying. In this way the following messages, the first ever to be com- municated officially by telegraph between America and Europe, were transmitted. August 16,1858. From the Directors in England to those in the United States: Europe and America are united by telegraphy. Glory to God in the highest, on earth peace, good-will toward men! Then followed: From her Majesty the Queen of Great Britain to his Excellency the President of the United States: The Queen desires to congratulate the President upon the successful completion of this great international work, in which the Queen has taken the greatest interest. The Queen is convinced that the President will join with her in fervently hoping that the electric cable, which now already connects Great Britain with the United States, will prove an additional link between the two nations, whose friendship is founded upon their common interest and reciprocal esteem. The Queen has much pleasure in thus directly communicating with the President, and in renewing to him her best wishes for the prosperity of the United States. This message was shortly afterward responded to as follows: Washington City. The President of the United States to her Majesty Victoria, Queen of Great Britain: The President cordially reciprocates the congratulations of her Majesty the Queen on the success of the great international enterprise [95] GREAT INVENTIONS accomplished by the skill. science, and indomitable energy of the two countries. It is a triumph more glorious, because far more useful to mankind than was ever won by a conqueror on the field of battle. May the Atlantic Telegraph, under the blessing of Heaven, prove to be a bond of perpetual peace and friendship between the kindred nations, and an instrument destined by Divine Providence to diffuse religion, civilization, liberty, and law throughout the world. In this view will not all the nations of Christendom spontaneously unite in the declaration that it shall be forever neutral and that its communications shall be held sacred in passing to the place of their destination, even in the midst of hostilities? James Buchanan. But the first successful Atlantic cable had been spoiled by the high voltages that had been used in the first week. Communication grew weaker and weaker and ceased entirely on October 20, 1858, after transmitting 732 messages in all. An inquiry was made into the causes of its failure, which definitely proved the high voltages to have been fatal. In 1865, after the American Civil War, the cable project was renewed, this time as a contractor’s venture. The Great Eastern was used by them as cable ship with the same able navigator, Staff Commander H. A. Moriarty, R.N., who had so successfully navigated the 4gamemnon. Plate 26 shows the Great Eastern and the cable fleet and Plate 27 the paying-out machinery on the deck of the Great Eastern. A much heavier cable than that of 1858, as recommended by Sir Charles Bright, was constructed. Several times the cable developed faults but was picked up by means of newly invented devices and spliced. But after 1,186 miles had been laid, a new fault developed, and in picking it up from a depth of 2,000 fathoms the cable parted. Several attempts were made unsuccessfully to recover it, but at length the project had to be abandoned for that year. Yet the promoters were not discouraged. Field secured the support of Sir Daniel Gooch, M.P., of the Great [ 96 ] PLATE 27 wt we Painting by Robert Dudley Paying-out machinery on the Great Eastern. youve Jo uolzdes v pue YISuay Joys WY *gggI PuL “SggI “gSgr Jo satquo onURpY “S981 TG ¥o ULNVILY FHL PROT Wans shinow 1 ¥Y ° “AY3A0I34 SHE NI GISN © : SWOH ied O56] JO Hidid ¥ NI yr ata “VANdVUD 30 1idOWS : = SOR TTAVO OLLNVILVeee TO NINN GNA AUS Pan THVT N Ree! HLONG1 > Pa S3TLW TVOILIYN Bele HLONIT +f LIV) OTENYULY 8¢ ALVId TELEGRAPHY AND TELEPHONY Western Railway, who contributed £20,000. Led by his example other large subscriptions came in, and the Telegraph Construction Company, which had made the cable and undertaken its laying, agreed to take stock in large amounts in compensation. A complete new cable was ordered, and plans were made to recover and splice the cable of 1865. Many new grappling devices were prepared for this purpose. With minor accidents, all went well this time. Starting on July 13, 1866, from Foilhommerum Bay, Ireland, in 14 days the Great Eastern arrived at Heart’s Content, Trinity Bay, Newfoundland, having laid 1,852 nautical miles of Atlantic cable. She then put back to sea, and after 24 days of grappling, distressing slips occurring again and again, the cable of 1865 was at last recovered. A signal brought great joy to the patient but downhearted watchers in Ireland on a Sunday morning. The message came: “Ship to shore. I have much pleasure in speaking to you through the 1865 cable. Just going to make splice.” On September 8, 1866, the 1865 cable was finished to Newfoundland, with a total length of 1,896 nautical miles. So much for the triumphant overcoming of the financial and mechanical difficulties. On the electrical side, to avoid disturbing earth currents Varley had introduced the idea of interrupting the cable as it approached the receiving end with a plate condenser, as shown in Figure 25. Under these circumstances, on making a signal the entering current charges the first-met plate of the con- denser, which induces across the insulation layer the opposite charge on the other plate, and drives from that plate through the receiving instrument to earth an electric charge equal in quantity and sign to that which the current had brought to the first-met plate. For telegraphy the effect is exactly as though the line were continuous, but the disturbing earth current can not flow at all across the break into the line, after once producing its 197] GREAT INVENTIONS steady state within the condenser. Indeed, condensers are placed at both ends of the cable, so that no direct current enters the line at all. The cable is duplexed also, so that telegraphy becomes merely the creation of a succession of electric surges against the walls of the condensers. It was found that owing to induction and capacity the Atlantic cable would be very slow if time were allowed to Fic. 25, Cable operation through electric condenser fully complete each signal. Also the disaster of the cable of 1858 had proved that the cable could not bear currents strong enough to work ordinary telegraph relays. For both these reasons it was necessary to substitute some form of instrument sensitive enough to indicate the first beginnings of an effect at the receiving station. The current could then be immediately reversed to discharge the line, and make a signal by the contrary deflection of the instrument. For this purpose Sir William Thomson invented the reflecting galvanometer. This instrument has no material pointer like the older galvanometers. Its pointer is a beam of light reflected from a little mirror fastened to the system of magnets which hangs between [ 98 ] PLATE 29 Sir William Thomson (Lord Kelvin) PLATE 30 Alexander Graham Bell TELEGRAPHY AND TELEPHONY the coils. Such a galvanometer is described on page 80 of Volume 2 of this Series. As it was desirable to make a record of the signals, Sir William Thomson later in- vented another device called the syphon recorder, in which a fine electromagnetically deflected glass syphon spurts minute droplets of ink upon a moving paper. THE TELEPHONE Alexander Graham Bell (1847-1922) was of the third generation of a family of Scotch experts in the science of speech. His father, Alexander Melville Bell, and his uncle, David Bell, published in 1860 a work entitled “Bell’s Standard Elocutionist,” which has gone to some two hundred editions and is still used in Great Britain asa textbook. Melville Bell also invented a remarkable system called “Visible Speech,” according to which any sound of any language may be so accurately described that it can be imitated by an adept even if he has never heard it spoken. Graham Bell and his brother, Melville James, were thoroughly taught in their father’s system of “Visible Speech.” Says a friend of the family, the Reverend David Macrea: When Bell’s sons had been sent away to another part of the house, out of earshot, we gave Bell the most peculiar and difficult sounds we could think of, including words from the French and the Gaelic, following these with inarticulate sounds as of kissing and chuckling. All these Bell wrote down in his Visible Speech alphabet and his sons were then called in. I well remember our keen interest and astonishment as the lads— not yet thoroughly versed in the new alphabet—stood side by side looking earnestly at the paper their father had put in their hands, and slowly reproducing sound after sound just as we uttered them. Some of these sounds were incapable of phonetic representation with our alphabet.s At 17 years of age Alexander Graham Bell became a partner in his father’s business as a teacher of elocution in London. A little later the family emigrated to Canada, 5 From Alexander Graham Bell, by Catherine MacKenzie. Houghton, Mifflin Com- pany, 1928. [99] GREAT INVENTIONS and Melville Bell gave a series of lectures in Boston. As a result he was invited to extend the series, but being obliged to return to his business in Canada, he recom- mended his son in his stead. The Boston School Board appropriated $500 for this purpose, and at the age of 23 Alexander Graham Bell came to Boston, in April, 1871, for his first engagement. In October, 1872, he returned to Boston and opened a school of vocal physiology for the correction of stammering and other defects of speech. A child of Thomas Sanders of Haverhill had been born deaf, and was then 5 years of age. Bell undertook to supervise the education of the boy, who came to live at Bell’s boarding house and grew to love him tremendously. George Sanders’ father became Bell’s financial supporter in the telephone development. Another guiding influence in Bell’s life was Gardiner Green Hubbard, a wealthy Boston lawyer, whose little daughter Mabel had lost her hearing at 4 years of age. She was in some degree Bell’s pupil, and later became his wife. Hubbard was frequently in Washington in attendance on Supreme Court cases and resided there in later life. He became a Regent of the Smithsonian Institution, February 27, 1895, and served until his death, December 11, 1897. He was succeeded by his son-in-law, Alexander Graham Bell, January 24, 1898, who served as Regent until February 20, 1922, shortly before his death. There is a particular appropriateness in the fact that the inventor of the speaking telephone and his backer were both Regents of the Smithsonian Institution. On March 1, 1875, Bell had come to Washington in the interest of a patent application for his harmonic telegraph (a device for multiplex telegraphy which did not in the end become adopted). He called on Joseph Henry, then an aged man, who had been for almost 30 years Secretary of the Smithsonian Institution and a leader in American science. Bell told Henry, with that tremendous enthu- siasm which always characterized him, of his harmonic [100 | TELEGRAPHY AND TELEPHONY telegraph. Then he mentioned a curious experiment which he had made with an intermittent current of electricity and a helix of wire, which produced a sound. Secretary Henry was interested, and asked if he could demonstrate it. Bell made an appointment for the next day. Joseph Henry sat for a long time with the coil at his ear listening to the sound. This so much encouraged Bell that he deter- mined to ask Henry’s advice regarding his idea of the electric speaking telephone which he had then been experimenting upon for about a year. He explained the germ of his idea, and then added, “Which would you advise me to do: Publish it and let others work it out, or attempt to solve the problem myself?” “You have the germ of a great invention,” said Secre- tary Henry. “Work at it.” “I replied,” says Bell, “that I recognized that there were mechanical difficulties, and that I felt that I had not the electrical knowledge necessary to perfect the invention. His laconic answer was, ‘Get it’. I can not tell you how much these two words encouraged me.” Bell was at that moment particularly discouraged. His multiplex telegraph was dragging. His love affair with Mabel Hubbard seemed hopeless, and the telephone was as yet but a dim idea. Secretary Henry, the leading American scientist of that day, had listened to him cor- dially, and had given him a tonic of encouraging advice. As long as he lived Bell never forgot his obligation to Henry, or refused to listen to any young inventor in his turn. “But for Joseph Henry,” said he, “I should never have gone on with the telephone.” It was on June 2, 1875, that Bell for the first time got a really fruitful idea of how to vary an electric current by the speaking voice. With his instrument maker and admiring friend, Thomas A. Watson, he was tuning certain receiving parts of his harmonic telegraph to the pitch of the transmitting apparatus, operated by Watson 60 feet away. Suddenly Bell rushed over to Watson and [ ror | GREAT INVENTIONS exclaimed, ‘What did you do then? Don’t change any- thing! Let me see.” What had happened was that the make-and-break points of the transmitter had stuck together, so that when the spring was snapped the circuit had remained unbroken while the magnetized steel vibrating over the pole of the electromagnet had set up vibratory electrical currents in the circuit which Bell had recognized as sound at the receiver. “Before we parted that night,” said Watson, “Bell gave me directions for making the first electric speaking telephone.” The instrument now in the United States National Museum is shown in Plate 31, upper. The WAHESSES : Inventor: Fic. 26. Diagram from Alexander Graham Bell’s telephone patent mouthpiece is covered with stretched goldbeater’s skin. Attached to the center of the skin is an iron piece pivoted at the side, and close above the iron piece is an electro- magnet connected to the line. Watson strung a wire down two flights of stairs. That night he and Bell tried out the first electric speaking telephone. Bell could not hear Watson, but Watson heard Bell and rushed upstairs. “I could hear you!” he shouted. “I could hear your voice! I could almost make out what you said.” The delay until February 14, 1876, in filing Bell’s patent application almost cost him priority, for Elisha Gray filed a caveat on a system of electric speaking [ 102 ] TELEGRAPHY AND TELEPHONY telephony only two hours after Bell’s application was filed. The delay occurred in this way. Bell went home to his father in Canada in the summer of 1875 and interested a wealthy acquaintance there, George Brown. A con- tract was made whereby Brown was to apply for foreign patents on the telephone and share 50-50 in their profits. For this he and a friend agreed each to pay Bell $25 a month for six months to promote the experimentation, but stipulated that no patent application should be made Witnesses Invernlor: SE Fee ¥T, Wutcbaisenn 4, ally, y Fic. 27. Diagram from Alexander Graham Bell’s telephone patent in the United States until after he had reached England and filed one there. Brown delayed his sailing, and even after reaching England delayed filing. Bell held to his contract. But Gardiner Hubbard, without Bell’s knowl- edge or consent, filed, on February 14, the application which Bell had signed on January 20, 1876. It was allowed almost without change, and the patent issued March 7, 1876. As this is said to be financially the most valuable patent ever issued, so much of it as is needful to our understand- ing is here quoted. Two of Bell’s illustrations are shown in Figures 26 and 27. [ 103 ] GREAT INVENTIONS ALEXANDER GRAHAM BELL, OF SALEM, MASSACHUSETTS IMPROVEMENT IN TELEGRAPHY Specifications forming part of Letters Patent No. 174,465, dated March 7, 1876; application filed February 14, 1876. To all whom it may concern: Be it known that I, ALEXANDER GRAHAM BELL, of Salem, Massachusetts, have invented certain new and useful Improvements in Telegraphy, of which the following is a specification: My present invention consists in the employment of a vibratory or undulatory current of electricity in contradistinction to a merely intermittent or pulsatory current, and of a method of, and apparatus for, producing electrical undulations upon the line wire. It has long been known that when a permanent magnet is caused to approach the pole of an electro-magnet a current of electricity is induced in the coils of the latter, and that when it is made to recede a current of opposite polarity to the first appears upon the wire. When, therefore, a permanent magnet is caused to vibrate in front of the pole of an electro-magnet an undulatory current of electricity is induced in the coils of the electro-magnet, the undulations of which correspond, in rapidity of succession, to the vibrations of the magnet, in polarity to the direction of its motion, and in intensity to the ampli- tude of its vibration. There are many ways of producing undulatory currents of elec- tricity, dependent for effect upon the vibrations or motions of bodies capable of inductive action. A few of the methods that may be em- plcyed I shall here specify. When a wire, through which a continuous current of electricity is passing, is caused to vibrate in the neighbor- hood of another wire, an undulatory current of electricity is induced in the latter. When a cylinder, upon which are arranged bar-magnets, is made to rotate in front of the pole of an electro-magnet, an undu- latory current of electricity is induced in the coils of the electro-. magnet. Undulations are caused in a continuous voltaic current by the vibration or motion of bodies capable of inductive action; or by the vibration of the conducting-wire itself in the neighborhood of such bodies. Electrical undulations may also be caused by alternately increasing and diminishing the power of the battery. The internal [ 104 ] PLATE 31 SS ea Upper: Bell’s original telephone. Lower: Bell’s original box telephone PLATE 32 Bell’s box telephone of 1877 with hammer c alled ““Watson’s ephone receiver TELEGRAPHY AND TELEPHONY resistance of a battery is diminished by bringing the voltaic elements nearer together, and increased by placing them farther apart. The reciprocal vibration of the elements of a battery, therefore, occasions an undulatory action in the voltaic current. The external resistance may also be varied. For instance, let mercury or some other liquid form part of a voltaic circuit, then the more deeply the conducting- wire is immersed in the mercury or other liquid, the less resistance does the liquid offer to the passage of the current. Hence, the vibration of the conducting-wire in mercury or other liquid included in the circuit occasions undulations in the current. The vertical vibrations of the elements of a battery in the liquid in which they are immersed produced an undulatory action in the current by alternately increasing and diminishing the power of the battery. In illustration of the method of creating electrical undulations, I shall show and describe one form of apparatus for producing the effect. I prefer to employ for this purpose an electro-magnet, A, [Fig. 26] having a coil upon only one of its legs 4. A steel-spring armature, ¢, is firmly clamped by one extremity to the uncovered leg d of the magnet, and its free end is allowed to project above the pole of the covered leg. The armature c can be set in vibration in a variety of ways, one of which is by wind, and, in vibrating, it produces a musical note of a certain definite pitch. When the instrument A is placed in a voltaic circuit, g be f g, the armature c becomes magnetic, and the polarity of its free end is opposed to that of the magnet underneath. So long as the armature ¢ remains at rest, no effect is produced upon the voltaic current, but the moment it is set in vibration to produce its musical note a powerful inductive action takes place, and electrical undulations traverse the circuit gbefg. The vibratory current passing through the coil of the electro- magnet f causes vibration in its armature 4 when the armatures c h of the two instruments A I are normally in unison with one another; but the armature / is unaffected by the passage of the undulatory current when the pitches of the two instruments are different. I desire here to remark that there are many other uses to which these instruments may be put, such as the simultaneous transmission of musical notes, differing in loudness as well as in pitch, and the telegraphic transmission of noises or sounds of any kind. One of the ways in which the armature c¢, [Fig. 26] may be set in vibration has been stated above to be by wind. Another mode is shown in [Fig. 27], whereby motion can be imparted to the armature by the human voice or by means of a musical instrument. [ 105 ] GREAT INVENTIONS The armature c, [Fig. 27] is fastened loosely by one extremity to the uncovered leg d of the electro-magnet 4, and its other extremity is attached to the center of a stretched membrane, a. A cone, JZ, is used to converge sound-vibrations upon the membrane. When a sound is uttered in the cone the membrane a is set in vibration, the armature ¢ is forced to partake of the motion, and thus electrical undulations are created upon the circuit E 6 ef g. These undulations are similar in form to the air vibrations caused by the sound—that is, they are represented graphically by similar curves. The undulatory current passing through the electro-magnet f influences its armature 4 to copy the motion of the armature c. A similar sound to that uttered into 4 is then heard to proceed from L. Having described my invention, what I claim, and desire to secure by Letters Patent is as follows: 1. A system of telegraphy in which the receiver is set in vibration by the employment of undulatory currents of electricity, substantially as set forth. 2. The combination, substantially as set forth, of a permanent magnet or other body capable of inductive action, with a closed circuit, so that the vibration of the one shall occasion electrical un- dulations in the other, or in itself, and this I claim, whether the per- manent magnet be set in vibration in the neighborhood of the conduct- ing-wire forming the circuit, or whether the conducting-wire be set in vibration in the neighborhood of the permanent magnet, or whether the conducting-wire and the permanent magnet both simultaneously be set in vibration in each other’s neighborhood. 3. The method of producing undulations in a continuous voltaic current by the vibration or motion of bodies capable of inductive action, or by the vibration or motion of the conducting-wire itself, in the neighborhood of such bodies, as set forth. 4. The method of producing undulations in a continuous voltaic circuit by gradually increasing and diminishing the resistance of the circuit, or by gradually increasing and diminishing the power of the battery, as set forth. 5. The method of, and apparatus for, transmitting vocal or other sounds telegraphically, as herein described, by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound, substantially as set forth. In testimony whereof I have hereunto signed my name this 20th day of January, A. D. 1876. ALEX. GRAHAM BELL. [ 106 | TELEGRAPHY AND TELEPHONY A part of Elisha Gray’s caveat filed two hours later is also given. SPECIFICATION To all whom it may concern: Be it known that I, Elisha Gray, of Chicago, in the county of Cook, and State of Illinois, have invented a new Art of Transmitting Vocal Sounds Telegraphically, of which the following is a specification :— It is the object of my invention to transmit the tones of the human voice through a telegraphic circuit, and reproduce them at the re- ceiving end of the line, so that actual conversations can be carried on by persons at long distances apart. To attain the objects of my invention, I devised an instrument capable of vibrating responsively to all the tones of the human voice, and by which they are rendered audible. My present belief is, that aes most pene method of providing an apparatus capable of responding to the various tones of the human voice, is a tympanum, drum or diaphragm, stretched across one end of the chamber, carrying an apparatus for producing fluctuations in the potential of the electric current, and consequently varying in its power. In the drawings, the person transmitting sounds, is shown as talking into a box or chamber A, across the outer end of which is stretched a diaphragm a, of some thin substance, such as parchment or gold- beaters’ skin, capable of responding to all the vibrations of the human voice, whether simple or complex. Attached to this diaphragm is a light metal rod A’, or other suitable conductor of electricity, which extends into a vessel B, made of glass or other insulating material, having its lower end closed by a plug, which may be of metal, or through which passes a conductor 4, forming part of the circuit. This vessel is filled with some liquid possessing high resistance, such for instance as water, so that the vibrations of the plunger or rod A’, which does not quite touch the conductor 4, will cause varia- tions in resistance, and, consequently, in the potential of the current passing through the rod A’. Owing to this construction, the resistance varies constantly, in response to the vibrations of the diaphragm, which although irregu- lar, not only in their amplitude, but in rapidity, are nevertheless transmitted, and can, consequently, be transmitted through a single rod, which could not be done with a positive make and break of the circuit employed, or where contact points are used. [ 107 ] GREAT INVENTIONS The obvious practical application of my improvement will be to enable persons at a distance to converse with each other through a telegraphic circuit, just as they now do in each other’s presence, or through a speaking tube. I claim as my invention the art of transmitting vocal sounds or conversations telegraphically, through an electric circuit. ELISHA GRAY. Hubbard had an official position at the Philadelphia Centennial of 1876 and urged Bell to exhibit his telephone. Bell was so late in getting the exhibit ready that it could not be placed in the electrical section, but occupied a very inconspicuous corner in the educational section. Bell himself was occupied with the annual examinations of his speech classes when Hubbard telegraphed him to come to Philadelphia, so as to demonstrate the telephone to the judges. Bell felt it impossible to go, but his fiancée, Mabel Hubbard, and her mother at last persu- aded him. He was present in Philadelphia to meet the judges on a very hot Sunday, June 25, 1876, and had arranged to return to Boston that same night. Among the judges was Sir William Thomson, the great English expert who had made the Atlantic cable work, and accompanying the judges was Dom Pedro, Emperor of Brazil. They were tired and hot, and intended to finish their examinations for the day just before reaching Bell and the telephone. Fortunately the Emperor, Dom Pedro, who had discussed the problems of speech with Bell in Boston, happened to see the inventor, and where the Emperor went the com- mittee of course followed. It was only a moment before their discomfort from the heat was forgotten when they heard for the first time human speech transmitted elec- trically. Sir William Thomson was especially enthusiastic. He introduced Bell’s telephone a little later in a lecture in Scotland as the most astonishing invention of the times. Before he left America he visited Bell in Boston, where a telephone demonstration was made. Plate 31 shows the [ 108 ] TELEGRAPHY AND TELEPHONY box telephone in use at that time, now deposited in the United States National Museum. During the summer of 1876, Bell arranged a demonstra- tion over a 5-mile line at his father’s home in Canada. An improvement of Bell’s telephone was patented by him in England in November, 1877, and Bell was presented at Court on January 16, 1878, where he demonstrated the telephone to Queen Victoria. Plate 32 shows a box-type telephone and a hand receiver of that period. Bell’s telephone was offered to the Western Union Telegraph Company but was declined. Instead, that company bought the patents of Elisha Gray and engaged Gray, Edison, and Dolbear to design a telephone for them. The American Speaking Telephone Company was formed as a subsidiary of the Western Union, and it entered into competition with Bell and his associates. Edison had in- vented the variable resistance carbon microphone trans- mitter, so that for a time the Western Union interests had the advantage in equipment. But the Bell interests brought suit for infringement of the Bell patents and also fortunately secured the microphone invented by Emile Berliner and improved by Francis Blake, which put their instruments fully on a par with those of the Western Union. Emile Berliner (1851-1929) was born in Hanover, Germany. At the time he invented the microphone he was a dry-goods clerk in Washington. It was in the year of the Philadelphia Centennial that he became interested in Bell’s telephone and tried to make one without knowing the details of Bell’s devices. From a friend interested in telegraphy he learned that a telegraph key must be pressed down hard to send a crisp message. That led him to the secret of the loose contact microphone. With a soapbox, a screw, and a button he made one that enabled him to talk down the stairs of his boarding house. Berliner wrote out a caveat covering the loose contact transmitter. It was filed and dated in the United States [ 109 ] GREAT INVENTIONS Patent Office on April 14, 1877, just two weeks before Edison’s application for the loose contact carbon micro- phone. Berliner applied for his patent in 1877, but it was not finally granted until 1891. As it covered basically all loose contact microphones, including Edison’s carbon transmitter, this patent of Berliner’s, then owned by the Bell Telephone Company, extended their monopoly from 1891 for 17 years. Suit to annul the Berliner patent was brought by the United States and carried to the Supreme Court. But that court, by a decision of six judges against one, upheld its validity, and dismissed the suit of the Government. To return to the suit with the Western Union: Making an end of the litigation between the Bell interests and the Western Union, George Gifford, counsel for the Western Union, informed his client that Bell was unquestionably the first inventor and advised a settlement with him. The patent rights of both contestants were pooled, with the ownership vested four fifths in the Bell interests, one fifth in the Western Union. In December, 1879, the Bell stock sold at $995 a share, though up to that time it had never paid a dividend. Many suits involving various claimants were instituted later against the Bell patent, of which several reached the Supreme Court. Bell’s position as the original inventor was invariably sustained by the courts. The telephone, as now constructed, is well shown by a working sectional model donated by the American Tele- phone and Telegraph Company to the Smithsonian Insti- tution in 1928 for exhibition in the United States National Museum. It is illustrated in Plate 33. The vocal speech is prepared for the line by the loose carbon granule micro- phone at 4. The diaphragm, a, is made to vibrate by the voice, and in vibrating alters the pressure on the carbon particles at 4. This alters the electrical resistance offered by these particles. Accordingly the current from the source, ¢, varies in strength as the electrical resistance of the carbon transmitter fluctuates with the vibrations of the Pune | umnasnyy [BUOReN ey} Ul “auoydayay uJapour dy) Suljvsysnqiy! Popow BUIYIONA e€ ALV Id asuvyoxe suoydaya3 v Jo JO1sO}UyT re ALVId TELEGRAPHY AND TELEPHONY voice. This fluctuating current, passing through the primary windings of the induction coil, d, induces an alter- nating current in the secondary windings. The alternating current passes through the line and variably energizes the distant coil, e. As this coil rides upon the pole pieces it alters the magnetic attraction of the magnet, f, for the iron diaphragm, g. In this way the air which adjoins the diaphragm, g, is caused to vibrate so as to reproduce at B the vocal speech spoken at 4. Telephony has advanced with great rapidity, particu- larly in the United States, which in 1929 had about 60 per cent of all the telephones in the world. Their numbers in the United States increased from about 50,000 in 1880 to 1,350,000 in 1900, 13,300,000 in 1920, and about 20,000,- 000 in 1929. The problem of connecting the immense numbers of subscribers in the large cities to the central exchanges is naturally a difficult one. Plate 34 shows the interior of a telephone exchange. Improvements have reached the point where nearly 2,000 wires are enclosed in a single metal-sheathed cable. Cross-talk by induction from one circuit to another is prevented by twisting the wires according to certain patterns. The exchanges, formerly entirely hand-operated, are growing more and more to be automatic. About one fourth of them are now of this class. The automatic switchboard is far too com- plicated to be explained here; it was developed from the invention of A. B. Strowger in 1889. There were 64,000,000 miles of wire operated by the Bell system in the United States in 1929. Long circuits be- tween the East and the West, such as are now used with perfect clearness, were made possible by Michael I. Pupin’s invention in 1900 of the “loaded line.” This con- sists in the insertion at certain computed intervals along the circuit of definite quantities of self-induction, supplied by so-called “loading coils.” The invention by G. E. Elmen, of “permalloy” which is an alloy of about 80 per herr | GREAT INVENTIONS cent of nickel with 20 per cent of iron has been of ad- vantage for the cores of loading coils. Like a telegraph line, the telephone must be relayed occasionally to produce sufficient volume of speech on very long lines. The early attempts at mechanical relays were not very satisfactory. The invention of the high vacuum thermionic amplifier described in Chapter III has solved the problem, for it can amplify the volume tre- mendously without much distorting the quality of the voice. This device has even made possible transoceanic telephony. The ocean transmission is accomplished by wireless repeating. It is now possible to carry on telephone conversations from any part of the United States to most of the countries of the world. [112] CHAPTER V RADIO TRANSMISSION In Volume 2 of this Series readers will have found the story that visible and invisible rays tell of the sun and stars. Distance, size, motion, temperature, pressure, magnetic condition, and chemical composition of these immense bodies, millions, trillions, and quadrillions of miles away, are made known to us by the study of their radiation. In this study the leading instrument is the spectroscope, which may be regarded as merely a wireless radiation receiver of exceptional selectivity, operating on rays of 2,000,000 times the highest frequencies now used in short-wave wireless. Light is but a wireless ray of shorter wave length. Whether we meditate on the marvels of the one or the marvels of the other, we must be lost in admiration of that essence, common to them both, which on the one hand reveals the secrets of the universe, and on the other can communicate around the world the voice and features of a friend. In a recent conversation with the writer, Doctor Jewett, Vice President of the American Telephone and Telegraph Company, remarked that though his position required him to be familiar with every step of progress in communication and to understand fully the details of the apparatus used, nevertheless the present perfection of wireless telephony still seemed to him almost magical, unbelievable. For instance, some one might pick up an ordinary desk telephone in Sweden, get his wire connection to the coast, thence by ocean cable to England, and again by wire to the transatlantic radio station. There his voice [113] GREAT INVENTIONS is changed and committed to ethereal vibrations and amplified up and up until the soundless waves can carry it across the Atlantic. Again it is retransformed and sent by land lines to the Pacific Coast. Wireless again takes it and flings it across to Hawaii. Another transformation is made, and the person called, seated at his desk with an ordinary telephone, not only understands the message, but recognizes his friend’s voice in far-off Sweden, as if he were in the next room. This is no fortunate discovery of one man. The boon came to the world little by little, as the genius, hard work, and financial sacrifices of many scientists, inventors, experimenters, and business men combined to accomplish the miracle. We commonly speak of messages “on the air.” The air is indeed useful in wireless, but only as a convenient construction material, like iron or copper, for parts of the apparatus. Air is not the conveying medium for wireless, as it really is for ordinary speech. Wireless messages travel like light by ethereal waves, and can travel quite as well in vacuum as in air. In fact wireless waves are very much like light waves in their true nature. They differ only in wave length, or, if we prefer, in frequency, which is the reciprocal of wave length. All waves, both of wireless and of light, travel approximately at 186,000 miles (300,000,000 meters) each second. Hence as a wave of green light is 5/10,000,000 meter long, it requires 10,000,000/5 x 300,000,000 such waves to carry light forward as far as it travels each second. The frequency of green light is therefore 600,000,000,000,000 waves per second. Radio waves are immensely longer, those ordinarily used ranging from I meter to 1§,000 meters in length. Their frequencies are therefore much slower, ranging from 300,000,000 down to 20,000 waves per second. Yet all of these radio frequencies are too rapid to operate an ordinary telephone. Even if the telephone [114] RADIO TRANSMISSION diaphragm could respond to them, the ear of the listener could not. To bring wireless waves into telephonic reception these rapid I wave trains are either modulated or broken up, in sending or re- ceiving, into trains of groups of vibrations. In effect, as indicated in Figure 28, these groups of radio-fre- I quency waves are the individual elements of audio-frequency waves forming parts of a se- ries of vibrations slow enough to move the na telephone diaphragm and to impress our Gafs.«, Pigure’,23,,..J, shows what is called a carrier wave of radio frequency. Figure 28, II, indicates the vibra- tions of the letter “A”’ as in “father’’ spoken in the ordinary tele- phone. Figure 28, III, shows how, by im- pressing it on the car- WA A ALA " HAT HT iil uli | ul i ball lag rl i st ii | ty | ta Fic. 28. Carrier and modulated radio waves. A carrier wave of rier wave, a modulated wave is produced which can be heard in the telephone. We referred above to Joseph Henry’s dis- covery in 1842 that radio frequency is indicated by I, though in waves billions of times the true radio wave length. In II is shown the form of the sound wave of “a” as in “father”. In III is shown the modulated wave produced by impressing the tele- phoned “‘a” on the carrier wave [115] GREAT INVENTIONS the discharge of a Leyden jar (or any other kind of elec- tric condenser) is oscillatory. It is not, he says, “‘a single transfer . . . from one side of the jar to another, [but] a principal discharge in one direction, and then several reflex actions backward and forward, each more feeble than the preceding until equilibrium is obtained.” During his experiments on this subject he found that “a single spark . . . of about an inch long, thrown on the end of Fic. 29. Discontinuous radio wave a circuit of wire in an upper room, produced an induction sufficiently powerful to magnetize needles in a parallel circuit of wire placed in the cellar beneath, at a perpen- dicular distance of 30 feet, with two floors and ceilings, each 14 inches thick, intervening.” There are two kinds of actions which electricity can bring to pass at a distance. The first is such as sets up an electric current in a free coil whenever a current nearby is changing its strength. This is called mutual induction. Of the same nature is the force opposing its own charge which an electric current produces in its own conductor. This is called self-induction. Effects of electric induction fade out rapidly with distance. The fading is proportional in many cases to the inverse cube of the distance. If induction were the only available means to propagate electric action through space, wireless communication could go but short distances. But electricity produces another effect, capable of traveling great distances. Whenever a high-frequency oscillatory discharge of a condenser takes place it sets up [116 ] RADIO TRANSMISSION electromagnetic radiation which travels, as we have said, 300,000,000 meters per second. In long paths above the earth this radiation weakens only in direct proportion to the increasing distance, not proportionally to the cube of the distance, as does induction. Electromagnetic waves can not travel in conductors, but only in insulators. The upper part of the earth’s atmosphere is an ionized vacuum, and like any high vacuum is a conductor and a reflector of radio waves. This property of the upper atmosphere CO Oo —_ <> = —_ = S oe, << —_ 7 Fic. 30. A discontinuous-wave radio set was suggested by Heaviside, so that we speak of the “Heaviside layer.” Radio waves are reflected by it and by the earth, both being good conductors. Therefore, in- stead of going out into space and being lost, radio waves travel round and round the earth in the space occupied by the atmosphere between these two conducting layers. Electromagnetic waves were the effects which Joseph Henry produced by the spark above mentioned. He was dealing then not with induction, but with radiation. It easily leaped the 30 feet of distance from the experimental room to the cellar of his laboratory. Wave trains of wireless waves may be either continuous or discontinuous. Discontinuous waves comprise suc- cessions of similar groupings of highly damped waves as shown in Figure 29. In Figure 30 is shown one kind of Par7 GREAT INVENTIONS apparatus for producing damped discontinuous wave trains. The alternating dynamo, a, is connected to the primary of the step-up transformer, 4. From its secon- dary, c, a high voltage charges the condenser, d, alter- nately positively and negatively as the current alternates. The short spark gap at e has not sufficient resistance to hold back the full charge of the condenser, d. Hence the spark passes at every plus and at every minus phase of the current wave. But, as Joseph Henry discovered, the spark is oscillatory and goes through several very quick oscilla- tions before subsiding. These oscillations are of radio frequency and may be communicated by a sending antenna to great distances. The individual groups of waves themselves, like those illustrated in Figure 29, succeed one another only twice as fast as do the cycles of the alternator, a. If the alternator is, for instance, of 500 cycles per second, the groups in the wave train will repeat 1,000 times per second. If broad- cast and received by antennas, this frequency will produce in a listening telephone a singing note of about the pitch of B natural of the high soprano register. Hence the sender needs only to interrupt the current, according to Morse’s dot and dash alphabet, to communicate a wireless telegraphic mes- sage, received in the form of singing notes and silences. The explanation of the action of the antenna in propa- gating and receiving the oscillations set up by a spark dis- charge or other high-frequency wave source, leads us to the important subject of resonant electric circuits. A con- denser, as we have remarked, is any electric device in which an insulating medium lies between and separates two electric conductors. The earth is a conductor, and so, too, is the antenna, which, as is well known, is insulated from the earth. Between them lies the air. This is the insulating medium, or as it is called, the “dielectric,” which completes the group of three necessary parts of a condenser. From the sending antenna to the earth is con- nected a wire in which is often inserted a low-resistance coil. [118 ] RADIO TRANSMISSION This wire and coil, together with the antenna, constitute an electric system which has not only a small resistance, but also, like every extended electric connection, has the prop- erty of self-induction discovered by Joseph Henry. It has been shown both by theory and experiment that in a circuit comprising both a condenser and an inductance, there is an opposition called reactance to the flow of an alternating current. The reactance may easily be millions of times as great as the electrical resistance of the circuit. In such a case it is a complete bar to the current. On the other hand, except for the ordinary ohmic electrical re- sistance itself, the reactance in the circuit may be reduced to zero. This condition is called resonance. It holds only for waves of a particular frequency. Since this is so, all other waves but those for which the circuit is resonant are excluded by reactance. This constitutes “tuning.” Resonance or tuning is possible because the reactance due to the capacity of a condenser is opposite in nature to the reactance due to induction. To find the total react- ance of the circuit one must take account of the reactance of resistance additional to that of induction, but must diminish their combined effect by reason of the reactance of capacity. Now it is true that the reactance of induction increases in direct proportion to the wave frequency, but the reactance of capacity decreases numerically in direct proportion to the wave frequency. To see how the two influences neutralize each other at certain wave frequency, consider the following table, appropriate to a circuit whose capacity is 0.005 microfarads, and whose inductance is 500 microhenrys, and whose resistance is neglected. Frequency Reactance Reactance Reactance cycles of induction of capacity Total per second (ohms) (ohms) (ohms) 60 0.19 — 530,000. 530,000 1,000 3-14 — 31,840. 31,837 100,700 316.2 = 9 TO fo) 1,000,000 a tA. a oGte 3,110 [119 ] GREAT INVENTIONS This particular circuit is in resonance for a frequency of 100,700 cycles per second, corresponding to a wave length of 300,000,090/100,700 or 2,980 meters. For any fre- quencies far removed from this one, the reactance of this circuit becomes very great, and prevents the passage of appreciable currents. Circuits may be tuned to given frequencies by alter- ing either the inductance or the capacity. The capacity ts very simply varied in ordinary radio sets by rotating a handle which carries on its axis a set of parallel metallic plates much longer than they are wide. As they rotate they interlockingly enter between a corresponding set of parallel metallic plates. When the two sets of plates are wide apart the air gap is so large that the capacity of the condenser is very small. As the plates interweave, the air spaces become narrow, and the electric capacity increases. Near the condensers in the cabinet of a radio receiver are coils of wire wound on paper cylinders; these are the induc- tion coils with which the condensers are in tune. Figure 30 shows a diagram of a simple but complete radio telegraph. The alternating current, of perhaps 500 cycles per second, indicated as originating at 4, actuates the primary coil, 4, of a step-up transformer. The high voltage secondary coil, c, charges the condenser, d, above the discharging point of the spark gap, e, at each maxi- mum of positive and negative phase in the alternating cycle. Thus there are produced a group of damped oscilla- tions of radio frequency perhaps 100,000 per second, as each spark occurs (see Fig. 29). With the 500-cycle alter- nator there will be 1,000 such groups of oscillations each second. The induction coil, f, is adjustable in its induc- tance so that at the radio frequency of the oscillations set up by each spark, the circuit, d, e, f, is in resonance. Simi- larly the antenna, 7, and induction coil, f, together with the ground connection, 4, are also adjusted at 7 to be in resonance for oscillations of this frequency, which, as we suggested, may be 100,000. At g a hot-wire ammeter, or, [ 120 ] PLATE 35 The author examining the General Electric Pliotron vacuum tube and other tubes RADIO TRANSMISSION more simply still, a glow lamp, indicates by a maximum current when the tuning of the antenna circuit is correct. The receiving antenna, with its inductance, /, and ground connection, ™, is tuned to resonance with the in- coming waves. A second resonant circuit is formed by the induction coil, 7, and adjustable condenser, 0. By the inductive coupling shown, the impulses in the coil, /, in- duce oscillations in the circuit, 7, 0. These Aes ledune vary the charge on the grid, 7, of the electron tube (see Chapter III), g, p, r, whose filament, q 1} is heated by an auxiliary battery, 4. Through the circuit of the plate, 7, go amplified trains of groups of oscillations of audio- frequency 1,000, as the successive sparks pass at e. These are suitable to produce a singing note in the telephone, s. The energy of the current which actuates the telephone, 5, is given by the battery, B, but is governed by the oscillatory voltage on the grid, p. This voltage in turn is governed by the distant key, &. As they key in the transmitting circuit ticks off its Morse code language, the telephone in the receiving circuit responds by singing notes and silences. Nature has provided and men have discovered a truly remarkable combination of elements which unite as just stated to make extensive wireless communication possible: First, the ethereal waves which travel 300,000,000 meters each second. Second, the rapid vibratory electric dis- charge of any instrument adapted for storing electricity. Such a discharge, like the pendulum, is not quieted at the zero status, but carries on past zero to a negative depar- ture almost as great as the original positive one, and so continues a whole train of oscillations until the gradual effects of damping bring quiescence. Third, the ability of such oscillatory electric discharges to set up ethereal waves. Fourth, resonance made possible by the counter- acting influence of inductance against capacity, whereby the opposition to the current, created by that electric capacity without which waves could not be produced, is [ 121 ] GREAT INVENTIONS reduced to zero. Fifth, the narrow range in wave lengths to which this compensation of reactances called resonance extends, thereby making it possible to extract a single message undisturbed from space filled simultaneously with other messages carried by waves of other frequencies. Sixth, the constant discharge of negative electrons from a heated wire, which is the basis of the electron tube, the soul of modern radio. Seventh, the ingenious device of the grid between the heated wire and the positively charged plate. For the easy modification of the voltage of the grid, in association with the feeble, inconceivably rapid oscillations of the wave trains received, produces a faith- fully copied fluctuation on a highly amplified scale in the flow of electrons to the plate, which we call the plate cur- rent. Eighth, and finally, the ingenious but relatively sim- ple devices of the telephone, which, in combination with these other elements, produce and carry to receptive ears the messages of this wireless age. Thus far we have dealt with damped waves, but ocean elephony and broadcasting are founded on systems of continuous undamped wave trains. As inventions have occurred, three principal sources of continuous wave trains have come into wide use. These are the mercury arc, often called the Poulsen arc, after a noted Danish inven- tor; the high-frequency alternator, often called the Alex- anderson alternator, already mentioned; and the electron tube, also already mentioned. At the present time the electron tube has outdistanced the others completely in the extent of its application, though Io years ago it was the mercury arc which held the field. We shall restrict our description of continuous-wave generation to the electron tube. This instrument has an enormously wide range of possible frequencies, from one to several hundred million cycles per second. Plate 35 shows three different types of vacuum tubes, representing extremes reached in recent development. The large tube in the center is a Pliotron, generating [ 122 RADIO TRANSMISSION 100,000 watts of radio-frequency power, sufficient to supply the output of a modern high-power broadcasting station. The copper cylinder (cut open to show the interior structure) is the anode, and is surrounded by a water jacket for cooling when in operation. The small tube on the right is a split-anode magnetron capable of generating several watts of ultra-high-frequency power, operating readily at 400,000,000 cycles per second. The small tube at the left is a low-grid-current Pliotron, used in the amplification and measurement of extremely minute direct currents, being capable of detecting a I current of =. ampere—a flow ofonly 100,000,000,000,000,000 60 electrons per second. In an ordinary household electric lamp about 3,000,000,000,000,000,000 electrons pass in a second. The use of an electron tube as an oscillating generator depends on the principle of regeneration. This principle bears a close analogy to the clock. In the clock we have a weight which furnishes abundant power to move the wheels and hands and a pendulum or balance wheel which restrains the action by making a certain number of vibrations per second. The pendulum or balance wheel would soon stop, owing to friction and air resistance, and the weight would then be unable to move the hands if it were not arranged that a very small amount of power from the weight is diverted from the hands to keep the pendulum or escapement moving at the required rate. Figure 31 shows the principle of the regenerative oscillating circuit applied to continuous-wave generation, and with it a device to modulate the wave train by a microphone, so as to transmit speech. All to the right of the dotted line XY 1s the radio-frequency circuit, that to the left of XY is the audio-frequency circuit. Beginning at the lower center of the figure, @ is a direct-current generator or battery, whose negative pole, at the left, is directly connected to the junction, 4, of which we shall 23 GREAT INVENTIONS make mention repeatedly. From the positive pole of the generator the connection passes through the iron-cored induction coils, ¢ and d, and the “choke coil,” e, to the plate, f, of an electron tube. Thence the connection continues to the condenser, g, and the inductance, 4. To the latter is attached the antenna, /, through an ammeter, Fic. 31. A regenerative oscillating radio circuit with modulated continuous wave propagation A, and also the ground, 7. Tracing the connection further, we come to the oscillating circuit including the induct- ance, k, and variable condenser, /. The regenerative impulse is provided here. It will be noted that the in- ductance, k, is so near the inductance, 4, that when currents are made in / they produce by induction currents in k. The inductance, k, and the condenser, /, are adjusted to be a tuned circuit of the desired frequency. Oscillating in harmony with them is the antenna circuit. From the condenser, /, the connection branches. One branch goes through the condenser, m (about which is shunted the large resistance, 7, called a “grid leak”), and ending with the grid, 0, of the electron tube. The other connec- tion from / continues to the junction point, 4, but on the [ 124 ] RADIO TRANSMISSION way throws off the hot-filament circuit, p, of the electron tube, which has a small battery, g, of which the negative pole is on the left. Being directly connected to the junction, 4, this pole of the battery, g, is at the same potential as the negative pole of the generator, a. Confining our attention at first to the radio-frequency part of the diagram, just described, let us see how it works. The making of the circuit to furnish power at a, at once gives a current impulse through the coil, 4, and this induces a small current in the coil, &. But the circuit, k, /, is resonant, so that this sets up in the circuit k, /, an oscillation of the desired frequency, which is com- municated through the condenser, m, to produce an oscillating voltage on the grid, o. Thereby an amplified oscillation of the same frequency is produced in the current from the filament, p, through the plate, f. This oscillating high-frequency current can not pass through the choke coil, e, or the iron-cored induction coils, d and c, to set up surges in the generator, a, which might spoil its insulation. However, the condenser, g, offers little impedance to it and it builds up oscillations in the antenna circuit. By induction these oscillations strengthen the feeble oscillations in the tuned circuit, k, 7. Thus the oscillations intensify more and more, at the expense, of course, of power furnished by the generator, a. At length (and though it takes long to tell it, and the time “at length” measured by number of oscillations is enor- mous, yet the time “at length” measured by the clock is only a fraction of a second), the intensity of oscillation reaches a maximum, and continues unchanged thereafter, so far as the radio-frequency circuit is concerned. To complete the story of the radio-frequency circuit, the grid, 0, which is of the same average potential as the junction, 4, and the filament, p, captures negative electrons in the positive half of every oscillation. Thus it tends to become more negative. But this tendency, which if unchecked would stop the oscillation, is nullified by the [125 ] GREAT INVENTIONS grid-leak resistance shunt, 7, which allows the excessive negative charge on 9 to be dissipated. The ammeter, 4, is merely for the purpose of noting when the circuit is so attuned as to give the maximum antenna current. Turning now to the audio-frequency circuit, the microphone, r, of the ordinary telephone type, when spoken into, sets up current changes in the primary, s, of the step-up transformer, whose secondary, ¢, impresses the accompanying voltage fluctuations on the grid, uz. This grid is normally more negative in potential than the junction, 4, and the hot filament, 2, by the whole voltage of the battery, w, whose negative pole is on the left. Hence, without capturing any negative electrons itself, the fluctuations of the grid voltage cause amplified fluctuations of streams of negative electrons to pass between the filament and the plate, y. Owing to the iron-cored choke coil, d, the voltage changes thus produced on the plate, y, are hindered from being freely dissipated in plate-current changes. These audio-frequency fluctua- tions go over as surges of voltage through the air-cored coil, e, effective as a choke coil only at the much higher radio frequencies, and so modulate the voltage of the plate, f. Accordingly the oscillations in the antenna change from a uniform continuous wave train like I of Figure 28 to a modulated wave train as shown at III. The generator, a, it will be seen, plays a part in the audio-frequency circuit. It maintains a high positive potential on the plate, y. As rapid fluctuations of voltage of the generator would introduce disagreeable modulations in the antenna current, the iron-cored coil, c, and con- denser, z, are introduced as a filter. They smooth out rapid fluctuations of the direct-current generator which might arise from inequalities of the commutator. Heterodyne and superheterodyne reception are terms often heard. It is not possible to perceive with a telephone a uniform continuous radio-frequency train of waves, nor are irregular breaks made by telegraphic signals of the [ 126] RADIO TRANSMISSION Morse dot and dash system directly recognizable in such waves. But if at the receiving station a local uniform continuous wave train of equal amplitude but differing slightly in frequency is superposed on that coming from a distance, beat waves, comparable to the beats listened for by piano tuners, are produced, having a frequency equal to the difference in frequencies of the two original sets of waves. If, for instance, the distance wave is of 300 meters, or 1,000,000 cycles in frequency, and the local wave of the frequency 1,001,000 cycles, a third wave of audio frequency of 1,000 cycles will be produced by the beats. If now, the wave train from the distant station is interrupted by dots and dashes of the Morse code, then the audio-frequency beat wave will be inter- rupted by silences every time the sending is interrupted. This is called heterodyne reception, but is unnecessary in wireless telephony, because the modulation of waves produced by the microphone take its place. However, it is found unsatisfactory to amplify greatly the exceedingly high frequencies, up to 20,000,000 cycles per second, or more, now used in ocean telephony. These may first be reduced to moderate radio frequencies by heterodyne methods before amplifying. After amplifica- tion in this intermediate radio frequency, the message may be reduced to audio frequency and again amplified. The same device is used in some broadcasting receiving sets to improve the tone quality. It is called super- heterodyning. It would be too complex to trace the improvement of radio communication further. Crystals that expand and contract in unvarying rhythmic vibration are used as master oscillators to standardize the frequency of broad- casting stations. Amplifying electron tubes are applied in cascades to step up the intensities of radio-frequency and audio-frequency waves. The resources of the theory of sound and of electricity are applied by expert mathe- maticians and experimenters to improve the quality of brz7 | GREAT INVENTIONS the sounds received and to eliminate disagreeable blemishes. It is said that the eminent conductor of the Philadelphia orchestra, Stokowski, finds the broadcasting of his music so perfect that he is unable to distinguish at the broad- casting station whether the sound comes to him directly through the air or indirectly by radio transmission. It is not to be supposed that a perfection so complete at the source is retained in the many receiving sets in distant States where his concerts are enjoyed. Yet more and more, in rapid advance, the art of radio transmission and reception is being improved. Even now it must be a critical musical ear that fails to receive great pleasure from radio rendition of a symphony. When we trace the steps of radio development, we find that the number of discoverers and inventors is so great and their contributions so outstanding that it is impossible in a brief space to do justice to them. Starting from the experiments which led Henry to infer the oscillatory character of the spark in 1842, we should note that in 1853 Sir William Thomson (Lord Kelvin) demonstrated it from theory and gave formulae suitable for computing the frequency of oscillation. His work was beautifully confirmed by the experimental demonstrations of Feddersen a few years later. At nearly the same time, 1864, Clerk Maxwell predicted from theory that electric waves must radiate from every system whereby such oscillations are produced and must travel in all dielectric media with the velocity of light and with other char- acteristics analagous to those of light. Maxwell’s theory incited Heinrich Hertz, in the decade 1880-90, to a brilliant series of world-renowned experi- ments. Hertz was able to demonstrate Maxwell’s waves experimentally, and to measure their reflection, refraction, polarization, diffraction, and wave lengths by experimental means analagous to those which show similar properties of light. Hertz used mainly the principle of resonance [ 128 | PLATE 36 Guglielmo Marconi. Courtesy of Maj. William J. Hammer of New York PLATE 3if es ee © Scaggs GONE) We Back a : et ee , Lawrenceville, N. J. Courtesy of the American Telephone and Telegraph Company. Photograph by Fairchild Aerial Surveys, Inc. itting station . Radio transm RADIO TRANSMISSION for detection. Then came Branly and Lodge with the coherer, a tube of metal granules which, under the influ- ence of waves, arranges its particles so as to become more highly conducting. This instrument was improved by Marconi, and made the basis of his earlier successes in developing Hertzian waves for wireless signaling. For a man so famous, unusual difficulty is encountered in finding an adequate biography. The following sketch of Signor Marconi’s early career is translated and abridged from “Nuova Antologia,” pages 482-487, January- February 1916. Guglielmo Marconi, a senator of the Kingdom of Italy by virtue of a statute which includes those who “by eminent services or merits will have made the country famous,” was born at Bologna on April 25, 1874, of an Irish mother, Annetta Jameson, whom his father, Giuseppe Marconi, had taken as his second wife in 1864. Having spent his childhood in Bologna, he completed his first studies at Florence in the Cavalleri Institute and at Leghorn in the Ferrini Institute, where he had Professor Vincenzo Rosa as teacher of physics. “In reviewing the history of my improvement of radiotelegraphy,” said Marconi in a lecture delivered before the Royal Academy of Sciences at Stockholm when in 1909 the Nobel Prize for physics was conferred upon him, “I desire to mention that I have never studied physics or electricity in a regular manner, although from my youth I have always been intensely interested in those sciences. “Moreover, I took a course of lessons in physics under the lamented Professor Rosa at Leghorn, and I believe I can say that I was very well acquainted with the publications of that time which treated of scientific subjects, including the work of Hertz, Branly, and Righi. “In my house near Bologna, I began early in 1895 to make trials and experiments with the object of determining by means of the Hertzian waves the possibility of transmitting telegraphic signs and symbols to a distance without the aid of connecting wires. “After some preliminary experiments with the Hertzian waves, I very soon became convinced that if those or similar waves could really be transmitted and received at considerable distances, a new system of communications would be possible, which would present enormous advantages over the luminous and optical methods of signaling, that are dependent upon the clearness of the atmosphere for their success.” The house was the Villa Grifone near Pontecchio about to kilos from Bologna, the property of his father. His father had assigned to [129] GREAT INVENTIONS him for his experiments a room located in the upper part of the house, and there Guglielmo Marconi worked, “trying and trying again,” and with very moderate means constructed apparatus conceived by him. As the first support of his antenna he employed a “broom handle” which is still preserved as a valuable relic. With a rudimental antenna he at last succeeded in transmitting a signal from one end of his labora- tory to the other. He repeated the experiment over a greater distance between the Villa Grifone and the Mountain of the Cross near Mon- techiaro in the Tenuta Malvasia about one kilo distant. A cross which stands upon that hill served him as a support for the antenna. . . . In September, rg1o, a little more than 15 years after his first ex- periments in which he succeeded in transmitting to a distance of a few meters, he was able to receive signals at a distance of 10,000 kilometers on the Italian liner Principessa Mafalda in port at Buenos Aires. In February, 1896, Guglielmo Marconi went to England, making his first experiments at Westbourne Park. On June 2 of the same year, he made his first application for a patent for radiotelegraphy, which was granted a few months afterwards under the number 12,039 of 1896. In July, 1896, Guglielmo Marconi was introduced to the Chief Engineer of the English Telegraphs, Sir William Preece, who listened attentively to the young man, assisted in his experiments, and was a great help to him. It was in fact at the desire of Preece that Marconi made some successful experiments between the Central Post Office in London and the distant Thames. In December, 1896, Preece delivered a lecture in Toynbee Hall, London, on “telegraphy without wires,” which Marconi illustrated by experiments. New records were made in May, 1897, in the canal of Bristol between Lavernock and Flatholm, and then between Lavernock and Brean Donn. across the canal to a distance of about 15 kilometers. In July, 1897, Marconi, called to Italy by the Ministry of the Marine, gave the first demonstration of his invention to the Italian authorities in the Ministry of the Marine, and then in the Quirinal in the presence of their Majesties King Humbert and Queen Margaret. On July 18 experiments were made between the arsenal of Spezia and the cruiser San Martino, reaching a distance of 16 kilometers. At the arsenal of Spezia a station was erected on the land and two warships were kept in constant communication with the coast. On his return to England, Marconi tried new experiments between Salisbury and Bath, reaching a distance of 55 kilometers. That led to the organization of a financial company to utilize the Marconi patent. It took the name of “Wireless Telegraph and Signal Company, Ltd.,” changed*in March, 1900, to that of “Marconi’s Wireless Telegraph Company, Ltd.” To that company Marconi ceded all his patents for [ 130 ] RADIO TRANSMISSION all the countries in the world, except for Italy and the Italian colonies, desiring to reserve liberty of action regarding his own country, in order to be able to yield his patents on preferential conditions whenever they might be able to serve in the defense of Italy. At that period two permanent stations were erected on the Isle of Wight and the experiments were happily continued in very stormy weather as his birthday approached. In May, 1898, a demonstration of apparatus tor wireless telegraphy took place in the House of Commons. A little while afterwards, in July, what was probably the first experiment in its practical applica- tion took place. The newspaper “Express” of Dublin published every day the report of the Kingstown yacht regattas by means of radio telegrams, which demonstrated the utility and the facility of using the new system for commercial purposes. Later on, Marconi established a communication between the Osborne residence of Queen Victoria and the royal yacht Osborne. In 1899, after a lecture at the Institute of English Electrical Engineers, he visited the United States. That year is noteworthy from the fact that the Marconi apparatus was installed on some warships of the English navy. Two years later, in Igol, a distance of more than 400 kilometers was attained, and soon afterwards the first signals were transmitted between Poldhu in Cornwall and St. John’s, Newfoundland. After numerous experiments between Nice and Corsica, in February, 1902, Marconi received good messages on board the steamboat Philadelphia at a distance of about 2,500 kilo- meters. In December, 1902, the station established at Cape Breton, Nova Scotia, by the Government of Canada was put in communica- tion with the station of Poldhu in Cornwall, England, and on its inauguration messages were sent from America to the King of England, to the King of Italy, to the “Times” and to the warship Carlo Alberto, which by the courtesy of the Italian Government had aided Marconi in his experiments. The great English steamship Lucania successfully made the first trial of permanent communication in the passage between Europe and America in October, 1903, and every day a bulletin of radio- telegraphic news was published on board. That service was then regularly adopted beginning with June 4, 1904. At the same time the stations of Bari in Italy and Antivari in Montenegro were established with a view to instituting a public telegraphic service between Italy and the Balkan peninsula. Finally, in 1907 the great station of Clifden was erected on the west coast of Ireland, but had to be reconstructed in Ig10 on account of a fire. Since April of that year it has worked regularly in the service between Europe and America and every day sends and receives messages for the whole world, corresponding with the station at Glace Bay in Canada. [131] GREAT INVENTIONS The great inventor did not fail to encounter both struggles and difficulties; but now the glorious discovery has been confirmed in history and the name of Marconi will go down to posterity with the admiration and the gratitude of the most remote generations. In the meantime the greater universities of Europe have conferred academic degrees upon him, the principal governments have accorded him the highest honors. and in 1909 the Nobel Prize for physics was awarded him. Sir William Preece, the eminent English telegraph engineer, ob- served: “It is said that Marconi has not found anything new. It is true that he has not discovered any new rays and that he has made use of the Hertzian waves, that his transmitter is the oscillator of Righi, and the essential part of his receiver is a coherer; but even Columbus did not make the egg and taught only how to make it stand upright.” During his long residence in other countries Marconi has never forgotten that he is an Italian, nor has he ever given up his Italian citizenship. He has also served his country, like all his fellow-citizens, by rendering military service in the Royal Navy, and he has reserved for Italy unconditionally the use of his patents for military purposes. Marconi has the credit of having saved, thanks to his invention, thousands and thousands of human lives, persons who without the desperate appeal for help thrown out by the radiotelegraphic apparatus of the ships in danger, would have perished miserably. The English Prime Minister justly remarked before Parliament after the wreck of the Titanic that the safety of the 700 persons rescued was due to a single man—Guglielmo Marconi. The same thing may be said of the Republic (January 23, 1909), of the S/evonia (1909), of the Delhi (December 13, 1911), of the Veronese (January 1, 1913), of the Templemore (September 30, 1913), of the Volturno (October 10, 1913), to mention only the earlier, more important ones. So the work of Guglielmo Marconi displays a cnaracter not only economic but highly humanitarian and his name will be revered and blessed in all the generations. We still remember the great emotion with which a traveler, accustomed to crossing the ocean, related to us the impressions of his first voyage on a steamship equipped with the Marconi telegraph. He felt as if connected with his family, with his business, with terra firma, and with all ships sailing in the entire world; and it seemed that a new sense of security and of pleasure ac- companied him across the seas. As Italians we must feel particularly proud of him, of his name, of his work, endorsing the general and enthusiastic approval with which the senate received the words of Major Ferraris, who in the meeting of December 16, 1915, calling to mind the recent discourse of Marconi, thus expressed himself: “To him I convey the sentiment of my devotion as an Italian, because wherever [132] Aurduroy ydeasoya y, pue auoydaya 7 UvVITIOUY 9 jo Asaqinoz “UOTIEYS opel 9[[FAIIUOIM eT xy} jo ssurpying 9y} Jo sud) 8€ ALVId qusujivdaq Aavyy sayv3ig payuyg oy3 Aq ydeisojoyg “vysepy “UONnrIS WysrT 1.uadg adeg 6 ALVId RADIO TRANSMISSION and under whatever quarter of the heavens I may find myself, his name today is the symbol of an Italy which works, studies and produces for the benefit of humanity.” The progress of radio in the last 20 years is so wide- ranging and technical that it is not possible to give a fair account of it without extensive use of the principles of mathematics and physics. We must, therefore, be content here to name without further explanation some of the great inventions and their makers. Lee De Forest, who invented the three-electrode tube, also applied it as a generator of high-frequency oscilla- tions, in which use it is now preeminent over the arc and the alternator. De Forest and E. H. Armstrong inde- pendently invented the feed-back or regenerative vacuum- tube receiver. Litigation on priority eventually reached the Supreme Court, where De Forest was finally adjudged the first inventor. I. Langmuir and H. D. Arnold independently discovered the properties of the high-vacuum electron tube. Priority was decided in favor of Langmuir by the Court of Appeals of the District of Columbia. Eventually the Supreme Court held there was no invention in the patentable degree over the prior art. | E. F. W. Alexanderson invented the tuned cascade radio-frequency tube amplifier. F. A. Kolster invented the coil direction finder. L.tA. Hazeltine introduced neutralization of tube capacity in the radio-frequency amplifier. J. H. Hammond, Jr., developed distant control by radio. E. H. Colpitts introduced modulation of high-frequency oscillations for voice transmission. W. G. Cady proposed the use of piezo-electric crystal vibrations as a control for oscillator frequency. J. H. Rogers invented underground antennas. P. D. Lowell and F. W. Dunmore jointly introduced alternating-current energization of radio receivers. [ 133 ] GREAT INVENTIONS G. Marconi developed directive or beam radio trans- mission. Many other valuable improvements should perhaps be mentioned, but the list is already long. We must close here this brief account of the principles and progress of the most astonishing of the arts which the discoveries of modern times have made possible. Plates 37 and 38 show the great installation for short- wave radio telephone transmission at Lawrenceville, N. J. The general view in Plate 37 shows in the short line of towers running approximately east to west, the supports of three antennas employed in the South American telephone service. The longer line of towers, running approximately northwest and southeast, supports nine antennas employed in the three short-wave circuits to Europe. The two buildings shown inside the antenna “WV” each contain transmitters—one for South America and three for Europe. Three antennas each for different wave lengths are provided for each transmitter. Since this photograph was taken an additional South American antenna has been constructed and an antenna and transmitter added for the Bermuda service. The re- ceiving stations for these circuits are located at Netcong, N. J. In order to give a more just idea of the enormous magnitude of this installation, we show in Plate 38 one of the two transmitting stations barely visible in the general view. Plate 39 is a view of the Cape Spencer Light Station, Alaska, where is located one of the radiobeacons that add so greatly to the safety of travel at sea. [ 134] CHAPTER VI tHE, ELBC TRIG LIGHT, WHEN Abraham Lincoln educated himself by the light of the flickering fire and of the tallow candle, these were the common light sources. The scholar’s “midnight oil,” furnished by the sperm whale, was a luxury. Kerosene had hardly come into use, and gas lighting, though used in cities, was not generally available. All of these kinds of light, which in their times have lighted the composition of some of the greatest poems, speeches, and books that the world has ever known, and have helped the ambitious boys of former days to become great lawyers and states- men, are now largely discarded. Electric lighting, based upon the fundamental discoveries in electromagnetism of Faraday and Henry, is now well-nigh universal. Some use was made of electricity for arc lighting as early as 1850, but little real progress in the modern sense came until about 1875, when the Jablochkoff candle and William Wallace’s arc lights came into use. Shortly after this, both Edison’s incandescent lighting system and electric arc lighting began to make rapid progress. It is true that Sir Joseph Swan as early as 1860 became convinced that the most practicable source of illumina- tion for the future would be the incandescent carbon fila- ment glowing within a glass bulb that had been evacuated, thus depriving it of air to prevent combustion of the fila- ment. He constructed such a lamp in 1860, in which carbonized strips of paper were caused to glow by electric current from primary batteries. At that time, however, there were no air pumps that could produce even an ap- [135] GREAT INVENTIONS proximate vacuum, so that the life of such a filament was short. In 1865 Sprengel’s mercury pump for producing high vacua appeared. Swan continued his experiments, but not until February, 1879, did he exhibit his improved glow lamp at a meeting of the Newcastle Chemical Society. In October, 1880, he conducted a demonstration of incan- descent lighting by this method, and a month later read a paper on “The Subdivision of the Electric Light,” showing its suitability for domestic lighting. Sir Joseph Swan continued in the lighting field, and invented a method of squirting cellulose by hydraulic pressure through a die, thereby producing the raw material for the fine, regular lamp filaments which gave place to tungsten only about 20 years ago. He was, besides, a fruitful inventor in other fields. His addition of gelatin in the copper-plating bath made possible far greater rapidity and improved quality in the electrolytic deposi- tion of copper. He also made great improvements in photography, including the invention of the first really fast dry plates, and he devised methods of photographic repro- duction still used. Sir Joseph, who came of a family of inventors, early showed a taste for chemistry and was ap- prenticed in the chemical business of Mawson in New- castle. He became a partner in that firm, and after a long and useful life, in the course of which he received many honors, he died, at the age of 86 years, on May 27, 1914. Thomas A. Edison (1847-1931) was born at Milan, Ohio, but spent most of his boyhood at Port Huron, Mich. He was a very enterprising boy, highly interested in chemis- try. To earn money for his chemical experiments, he obtained a concession for a paper route on the Grand Trunk Railway. He also started two stores in Port Huron, one for periodicals, the other for vegetables, and hired a newsboy to work the Detroit train. All this before he was 15 years old! To report the battle of Shiloh in 1862, he borrowed enough money of the editorial office of the Detroit Free Press to buy a thousand papers, and sold [ 136 ] THE ELECFRIC LIGHT them all from the train, some at 25 cents a paper. He fixed up a part of a baggage car for chemical experiments, and also set up there a small printing press. As reporter, editor, printer, and news agent he himself published a sheet called ‘““The Weekly Herald,” and sold over 400 copies a month. Unfortunately a stick of phosphorus among his chemicals took fire one day and threatened to burn the baggage car, whereupon the conductor of the train ejected boy, laboratory, and printing plant. The deafness that affected Edison throughout his whole life was caused about the same time by his being lifted into his box-car laboratory by his ears by a well-meaning friend. That same year, 1862, young Edison was so fortunate as to save the life of a little son of Mr. Mackenzie, a sta- tion agent. Out of gratitude, the father taught Edison more of the art of train telegraphy, of which he already knew something. His first job in telegraphy was at Port Huron, and soon after, at 16 years of age, he was made night operator at Stratford Junction, on the Grand Trunk Railway in Ontario. Owing to a narrow escape from an accident, which was thought by officials to involve some blame on Edison’s part, he left Canada and soon after obtained work as a night operator at Adrian, Mich. Thence he went from place to place, working up speed and ex- perience, till at length he entered the employ of the Western Union Telegraph Company at Indianapolis. Edison became an exceptionally fast telegraph operator, but again by his chemical experiments he caused trouble and was discharged. He next went to Boston and there got telegraphic work which kept him from starving while he began his inventive career. His first considerable invention was a stock ticker, to dispose of which he removed to New York. His Ingenuity attracted attention, and he soon formed the partnership of Pope, Edison & Company to develop some of his inventions. For his improvements on the stock ticker, Edison was paid $40,000 by the Western [ 137] GREAT INVENTIONS Union Telegraph Company, and then, in 1870, he opened a large shop in Newark, N. J., to make stock tickers for the Western Union. Thus, at only 23 years of age Edison was a successful inventor and manufacturer. His telegraphic experience gave the bent to his early inventions. Improvements on the printing telegraph and duplex and quadruplex telegraphy occupied him till 1873. His quadruplex invention was bought by Jay Gould for $30,000. After his first marriage in 1871, Edison removed in 1876 to Menlo Park, N. J., a little town ever to be celebrated as the scene of his famous demonstration of the practicability of the incandescent electric light. Despite the skeptical attitude of many able physicists and engineers, Edison was firmly convinced that the future of electric lighting lay not in the powerful and unwieldy arc, but in the small incandescent lamp, adapted to replace gas lighting in dwellings and offices, and like the gas Jet, capable of being turned on and off at pleasure. After familiarizing himself with the whole state of the art of lighting, both by elec- tricity and gas, and the best means of furnishing electric power, he began his experiments. Edison had gathered about him a devoted band of young assistants, whom he did not hesitate to drive day and night by his own example. Of powerful and enduring physique, he seemed able to go almost without sleep, yet could sleep instantly at any time he pleased. For many years his working schedule averaged more than 18 hours a day. Many a night he merely lay down upon a table top for a few minutes, and then pressed on with his work. His indefatigability in experimentation, in the course of which he would try everything that could be tried, was finally rewarded by success. Fdison first tried innumerable experiments with fibers of carbonized wood and other organic substances in evacuated glass bulbs. But these fibers proved in this series of experiments to be so short-lived as to be worthless. [138] THE ELECTRIC LIGHT Then he went over to refractory metals—platinum, irid- ium, and alloys. In association with them he tried bobbins of rare earths, and in this series he made 1,600 tests of various materials. He gained experience in producing high vacua, but no real success in lamps, and finally he went back to carbon. On October 21, 1879, a carbonized cotton thread in high vacuum attained a life of 40 hours. This was hopeful, but the lamp was too fragile to be com- mercially successful. He went on carbonizing substance after substance. Filaments of Bristol board cut to form, and carbonized by prolonged baking at high temperatures, gave so great a measure of success as to bring out the famous news article in the New York Herald of Sunday, December 21, 1879. EDISON’S LIGHT The Great Inventor’s Triumph in Electric Illumination A SCRAP OF PAPER it Makes a Light, Without Gas or Flame, Cheaper Than Oil TRANSFORMED IN THE FURNACE Complete Details of the Perfected Carbon Lamp FIFTEEN MONTHS OF TOIL Story of His Tireless Experiments with Lamps, Burners and Generators SUCCESS IN A COTTON THREAD The Wizard’s Byplay, with Bodily Pain and Gold ‘Tailings’ HISTORY OF ELECTRIC LIGHTING The near approach of the first public exhibition of Edison’s long looked for electric light, announced to take place on New Year’s Eve at Menlo Park, on which occasion that place will be illuminated with the new light, has revived public interest in the great inventor’s work, [139] GREAT INVENTIONS and throughout the civilized world scientists and people generally are anxiously awaiting the result. From the beginning of his experiments in electric lighting to the present time Mr. Edison has kept his labora- tory guardedly closed, and no authoritative account (except that pub- lished in the HERALD some months ago relating to his first patent) of any of the important steps of his progress has been made public—a course of procedure the inventor found absolutely necessary for his own protection. The HERALD is now, however, enabled to present to its readers a full and accurate account of his work from its inception to its completion. A LIGHTED PAPER Edison’s electric light, incredible as it may appear, is produced from a little piece of paper—a tiny strip of paper that a breath would blow away. Through this little strip of paper is passed an electric current, and the result is a bright, beautiful light, like the mellow sunset of an Italian autumn. “But paper instantly burns, even under the trifling heat of a tallow candle!” exclaims the sceptic, “and how, then, can it withstand the fierce heat of an electric current?” Very true, but Edison makes the little piece of paper more infusible than platinum, more durable than granite. And this involves no complicated process. The paper is merely baked in an oven until all its elements have passed away except its carbon framework. The latter is then placed in a glass globe con- nected with the wires leading to the electricity producing machine, and the air exhausted from the globe. Then the apparatus is ready to give out a light that produces no deleterious gases, no smoke, no offensive odors—a light without flame, without danger, requiring no matches to ignite, giving out but little heat, vitiating no air, and free from all flickering; a light that is a little globe of sunshine, a veritable Aladdin’s lamp. And this light, the inventor claims, can be produced cheaper than that from the cheapest oil... .... The Herald’s account of “lights strung on wires” so caught the public fancy that the fame of the “Wizard of Menlo Park,” already noted for his phonograph, was greatly enhanced. The Pennsylvania Railroad ran special trains to Menlo Park to see Edison’s marvel of the incandescent electric light. Plate 41, left, shows one of the earliest forms, now on exhibition in the United States National Museum. Yet carbonized paper did not seem to be quite the thing for filaments, and it occurred to Edison that the bamboo [4c] PLATE 40 Thomas A. Edison. Courtesy of F. A. Wardlaw, Secretary, Edison Pioneers £61 Jo sduryy 5143999 Jusdsapuvout Aw3Ad pur s9}suoW Sty dePq Pesousy sys ‘oggr ‘Lo Asenurf pajuazeg *unasnyy [PUOHE NY 943 Ul paziqryxe Mou sruIsoB yy *durvy 914999[9 JUsdsapuLduT payuazed sIseq SUOSIPY :3Ja] Wy ALVId THE ELECTRIC LIGHT rim of the ordinary palm-leaf fan might furnish the lamp fiber he had so long sought. Upon being tested, it proved to be much superior to all preceding substances. Not content, he ransacked the world’s original sources for the species of bamboo most suitable for his lamps. He spent $100,000 in expeditions and tests. A Japanese farmer got a contract to supply the kind of bamboo finally chosen. One of Edison’s emissaries named McGowan, who searched Peru, Ecuador, and Colombia for vegetable fibers, after traveling for 98 days through jungles swarm- ing with wild beasts, venomous snakes, and insects, at length returned at the end of 15 months to New York. After giving his friends an account vivid with adventure, he bade them good night at a New York restaurant and vanished, never again to be seen. The following extract from the New York Evening Sun of May 2, 1889, gives a glimpse of McGowan’s experiences. Going up the Amazon you meet nothing but yellow water and dense forests. The banks of the river are lined with alligators. Fifty-two alligators were shot one morning from the steamer’s deck. In former years grape shot was sometimes fired on Indians assembled on the river banks. Now matters are much reversed. The Indians amuse them- selves by making a target of the Brazilian gunboats and literally deluge them with showers of arrows. The Indians shoot these arrows with such terrific force as to send them through the steamship’s hull. I shall never forget my own experience. It was like peril dropping out of aclearsky. We were lazily engaged one sunny afternoon in dragging out an existence on the steamship’s deck, when suddenly from out of the forest came a volley of arrows. Some of these arrows penetrated the woodwork. Their bows are at least eight feet long and at the middle are as thick as my wrist. I could not bend one of them. The strings are made of the bark of trees. The arrows are about five feet in length and are invariably tipped with poison. From Iquitos I struck out on foot across the country accompanied by three Inca Indians. I carried 300 South American silver dollars under my arm in a tin box that weighed about twenty-five pounds. Every time those coins jingled I noticed the Indians exchange significant glances, and I was in mortal dread to go to sleep nights. Once I was [341 ] GREAT INVENTIONS suddenly awakened by a fierce growl. Dancing about me I saw one of the Indians, who pulled and tugged at me roughly, and pointing into the forest said in Spanish, “Big tiger!’ The following morning we reached the Napo river and poled up the stream in canoes many miles. At night we camped on the shore, sleeping on the wet banks. Twelve times during our journey the river rose so high that our party was washed off the banks while sleeping. In going down the River Santiago we encounterea river snakes fifteen feet long and six inches in diameter. It was now the rainy season and we could not sleep at night, for every two hours or so we had to bail out the canoes. The temperature was 100 to 102 and our clothes fairly steamed from moisture. We encountered millions of sand flies which got in our eyes, ears and hair. The river is full of fish, and frequently in the morning we found fish in the bottom of the canoe which jumped in during the night. I struck out on one trip for the Western Cordilleras, where I went into camp for twenty-seven days. A party of Peons accompanied me. I had the greatest difficulty in holding them, as they were terribly afraid of wild animals, and the woods were full of them. At night we were obliged to keep an immense fire blazing to keep them off, and even then we could hear them roaring uncomfortably near us. At midnight June 29, 1888, we were rudely shaken in our sleep by an earthquake. It made the mountains tremble. The Peons were instantly up and on their knees praying to their patron saint. Much of my valuable material which I collected for Mr. Edison was found in the Cordilleras, and I do not begrudge the hardships I endured. In Edison’s first successful lamps, the oval loops of carbonized paper were secured by little platinum clamps to platinum wires sealed through the glass. The early lamps were of uneven life but averaged 300 hours. The first considerable installation of them was made at the request of Henry Villard on the steamship Columbia for the Oregon Railway and Navigation Company, of which Villard was president. She carried 115 lamps of 10 candlepower, and made the journey round the Horn to Oregon, arriving July 26, 1880, with the new illumina- tion proved to be a great success. The first lamps required 4-9 watts of energy per candle. A modern Mazda C lamp, gas filled, uses from 3/10 watt per candle upwards, depending on the power, and has a life of 1,000 hours. We shall trace some of the steps in this improvement. [ 142] THE, ELECTRIC LIGHT Among the most perfect accessories of the incandescent lamp was the Edison screw socket, which became nearly universal not only for lamps, but for all sorts of electrical appliances. Various other lamp-supporting devices were’ invented by other makers to avoid the Edison patents, but they have nearly all disappeared. In later con- structions, cheaper metals and welded joints were sub- stituted for the costly platinum lead wires and screw clamps. The carbonized bamboo filaments continued till 1894, when carbonized squirted cellulose replaced them. These, in turn, were replaced about 1908 by tantalum and later tungsten, of which another story must be told. Hardly had the search for a fiber reached success before Edison and his band of workers turned with the same untiring ardor to prepare the means for providing and subdividing the current. Not content with the direct- current dynamos then available, Edison constructed a type characterized by very long electromagnets for the field, as shown in Plate 42. He obtained a high efficiency for that time, though greatly improved dynamos came from other inventors about the same time. He had preferred fibers of high electric resistance for his lamps because that made possible economy in copper. His idea was to provide a central electric power station, from which would go out conductors to convey the current to the lamps in houses and offices. In order to avoid rela- tively great loss of power in long transmission lines, the resistance of such lines had to be small compared with the resistance of the lamps. If the lamps had small resistance, the copper wires would have to be of large diameter and costly. On the other hand, if the lamps had a very high resistance, a dangerously high voltage would be required to make them incandescent. As a compromise, Edison fixed on 110-volt circuits, which voltage has remained the standard to this day. The device of the three-wire system occurred to him as another means of saving copper. It was, of course, necessary for [143 ] GREAT INVENTIONS practical reasons to have the lamps connected in parallel as the rounds of a ladder are connected to its two sides. For if in series, like a ring of people joining hands, all the lamps would have to burn at once—if one failed the whole series would be in darkness. In the three-wire system, the two outside mains were 220 volts apart. The middle wire acted both as negative pole for one bank of lights and positive pole for the others. If the lights were of equal numbers in the two banks, no current at all would flow in the middle wire. Even if the numbers of lights were not quite equal, the current in the middle wire was so much less than those in the two outside mains that a much smaller middle copper wire would serve. During 1880 and 1881, Edison was assembling engines, dynamos, lamps, underground feeders and mains, switches, meters, sockets, and the thousand and one accessories for the first central lighting station in New York. This he located on Pearl Street, and arranged to supply from it a square mile extending from Spruce to Wall Street and from the East River to Nassau Street. On September 4, 1882, the current was turned on for the first regular dis- tribution of light. Thirty-five years later a bronze tablet was placed on the building at 257 Pearl Street bearing this inscription: 1882 1917 IN A BUILDING ON THIS SITE AN ELECTRIC PLANT SUPPLYING THE FIRST EDISON UNDERGROUND CENTRAL STATION SYSTEM IN THIS COUNTRY AND FORMING THE ORIGIN OF NEW YORK’S PRESENT ELECTRICAL SYSTEM BEGAN OPERATION ON SEPT. 4, 1882 ACCORDING TO PLANS CONCEIVED AND EXECUTED BY THOMAS ALVA EDISON TO COMMEMORATE AN EPOCH-MAKING EVENT THIS TABLET IS ERECTED BY THE AMERICAN SCENIC AND HISTORIC PRESERVATION SOCIETY THE NEW YORK EDISON COMPANY [144] PLATE 42 ONT aR RL tN renieaenemeincemsencet te TES we fv) Edison Jumbo dynamo, as used at the Pearl Street, New York, station, 1881. In the National Museum ysoddns dwiry s4¥ uojsnopy-uoswoy F, ay], ys ‘ysoddns duryy s1e ysnig ayy :3yerT fF ALVId THE ELECTRIC LIGHT At the present time nearty a billion incandescent electric lamps are in use in the United States, and they have nearly driven arc lighting from the field. But the tremen- dous increase of incandescent lamps in late years has been due to the improvements in tungsten filament lamps, to which we will now turn. From Edison’s manufacturing enterprises grew the General Electric Company with headquarters at Schenec- tady, N. Y., and many branches and connections in the United States and abroad. This company established a great laboratory where many improvements in electrical appliances and discoveries in pure science have been made under the inspiring direction of Dr. Willis R. Whitney. It was Dr. William D. Coolidge of the General Electric Labor- atory who made tungsten available for electric lighting. It will be recalled that Edison in 1878 and 1879 had made many experiments with wires of the platinum group, including osmium, iridium, and others. The metal tung- sten does not fall in the group with platinum but is, next to uranium, the heaviest element of that group of chemical elements which contains oxygen and chromium. Tung- sten melts at 3400° C. while platinum melts at 1755°. Hence as a lamp filament, tungsten runs none of the dan- ger of melting when brightly incandescent, which, to- gether with costliness, made platinum impossible. Tungsten had been known since about 1780, but naa been little used except in alloys of steel. As a metal it was known to be extremely hard, but so brittle that it seemed quite impossible to draw it into wire. Two Austrian chemists, Just and Hanaman, had indeed pre- pared incandescent tungsten filaments in 1904, by mixing tungsten dust with organic matter, carbonizing the latter, and sintering the tungsten particles together by heat and pressure in presence of hydrogen. These lamps, though very fragile, were of high luminous efficiency, and imme- diately became popular after their general introduction in 1907 and 1908. [145 ] GREAT INVENTIONS W. D. Coolidge, assistant director of the General Elec- tric Laboratory, after several years of experimenting, aided by his associates, succeeded about 1912 1n producing ductile tungsten which could be drawn into the finest of wires, and wound in close spirals. As nearly all modern incandescent lamps and electron tubes are constructed with ductile tungsten filaments and grid wires, this dis- covery is one of the most useful of recent times. The process invented by Coolidge and his associates of the General Electric Company is as follows: First of all, it is desirable to begin with exceptionally pure tungsten. The ductility of tungsten is greatly dimin- ished by very slight admixtures of impurities. This also holds true with other metals. Gold, for instance, that when pure may be beaten almost inconceivably thin, is rendered brittle by as little as 0.05 per cent of lead, bis- muth, or tin, and is no longer malleable when it contains no more than 0.0003 per cent of antimony. Hence the first step toward ductile tungsten is purification. Tung- sten may be prepared from its ores by first converting them to tungstic acid, a heavy yellow powder. From this substance is prepared ammonium tungstate, which must be purified to the highest degree by recrystallization. When this product is heated to a certain degree, the ammonia is driven off, and tungstic acid in purest form remains. By heating this for five hours in a crucible of the proper composition, alumina and silica as desirable impurities are added to the extent of about one per cent. The tungstic acid is then reduced to metallic tungsten by heating gradually to redness in a current of hydrogen. The metal has normally a bright metallic luster like platinum, but when finely powdered, it is black. The material is made up into rods by pressing the powdered metal into molds and raising it in a hydrogen atmosphere to a bright red heat. This consolidates the powder so much that it can be heated electrically in a hydrogen atmosphere to blinding white heat, and thus [146 ] THE ELECTRIC LIGHT sintered firmly into a billet for mechanical working. The metal can now be worked mechanically at high temperatures. As the working process proceeds by the forcing of the billet through swaging dies, the ductility increases. At length, at lower and lower temperatures, the metal may be drawn out into fine wires. The die used for this process is drilled diamond. The wires produced are so pliable that they may be wound in small spirals and used for any kind of bends. Indeed, the tensile strength of tungsten in this form is as great as that of steel. Some time after the general introduction ot tungsten filaments for incandescent electric lamps, Langmuir discovered the advantage of introducing nitrogen or argon gas into the bulb. Either gas is inert and does not destroy the filament as atmospheric oxygen would destroy a carbon filament, for instance. In such a gaseous medium the evaporation of the tungsten filament is diminished. Hence, the time when the lamp bulb is darkened by deposited tungsten is postponed and the life of the lamp extended. On the other hand, the amount of current required to maintain a certain brilliance is increased, because the gas carries away the heat by convection. Langmuir’s device is most efficient for high-candlepower lamps, because with filaments of larger diameter, other losses are greater in proportion to convective losses than with small filaments. In small lamps with fine filaments, the loss in light efficiency tends to overbalance the gain in longer life. As remarked above, the advent of the high-candlepower gas-filled incandescent tungsten lamp greatly reduced the field of arc lighting, which 25 to 50 years ago monopolized the illumination of streets, stores, factories, and large halls. From 1877, when the arc system of Charles F. Brush appeared, and in 1878 when the Thomson-Houston arc was introduced, the electric arc for illumination was more and more improved in its regulation and efficiency [ 147 | GREAT INVENTIONS by numerous inventors. Plate 43 shows the Brush and Thomson-Houston arc supports. The tight enclosure of the arc in a glass globe, introduced by L. B. Marks in 1893, increased manyfold the duration of the carbons and decreased accordingly the care of maintenance. Prior to that time the carbons were rapidly burnt away by the free attack of the oxygen of the air. In Germany, Bremer in 1898 produced the flaming arc, in which the carbons were impregnated by calcium fluoride. Other chemical salts have been used to increase the luminosity of the arc, and with particularly notable success by the Sperry Company. For searchlights, the are will probably never be displaced, and at the present time very high efficiency in this field is obtained. [148 | CHAPTER’ VII PRIME MOVERS THE machine age is an age of power. Man power, horse power, the leisurely overshot water wheels found here and there in brooks and small rivers a couple of genera- tions ago, and even the reciprocating steam engines of those days are largely superseded. Swifter and stronger genii such as the gasoline engine, the water turbine, and the steam and mercury turbines have been called forth to excite the master spirit, electricity, that does nearly all things in our time. Some think machinery is a curse, and praise the good old days. The curse is found in three aspects of the wide-spread use of machinery, which no doubt will be removed in the future. These are: the noisy rush; the subdivision of labor into partial operations, senseless by themselves, which take away the pride of craftsmanship; and the suffering which comes when labor-saving machines throw workers out of employment. Inventions and the segregation of noisy operations can mitigate the hubbub. The evils of the subdivision and of the superseding of labor will both be cured sometime by social reorganization. Progress is needed more in this field than in any other at the present time. The machine age has advanced too rapidly to allow the required changes in social organization to keep pace with it. Evils grow to large proportions before their cure is discovered and applied. A century hence, the historian may be able to trace the steps which led society from the difficulties attending the first rapid rush of the introduc- [149 ] GREAT INVENTIONS tion of new forces in our time to their happy solution by the following generations. In principle, the progress of invention and the bounty of nature, both tending to diminish necessary labor, are good. We do not work for work’s sake, but for the sake of the comforts it brings, the mental pleasure it affords, and the physical well-being it promotes. If invention and nature’s fertility together could relieve the world of nine tenths of the present work, interesting occupations might still be retained. Handi- crafts, for instance, could be preserved, not because they are indispensable, but because they are enjoyable exercises of skill, productive of exceptionally fine artistry. Athletic occupations would be retained because they develop health. But under a proper social system for the dis- tribution of goods to all who need them, the abolition of nine tenths of the world’s work ought not to produce suffering. Nor in the society of the future ought indi- viduals to be forced to do one sort of drudgery throughout their working lives. A rotation of occupations ought to be provided. Other societies have existed happily with all their wants supplied without much labor. Consider, for instance, the birds that sing and frolic in the air. Man ought not to be so dull that a plentiful supply of good things merely multiples poverty and suffering for a large portion of his race. In the year 1931 mechanical energy amounting to about 92,000,000 horsepower was produced in the United States, of which one third was hydroelectric and two thirds came from the combustion of coal and oil. Of the 61,000,000 horsepower produced by fuel, about nine tenths came from coal and one tenth from oil and gas. These immense quantities of power were produced mainly by the water turbine, the reciprocating steam engine, the steam turbine, and the internal combustion reciprocating engine. Prime movers may use energy of position or energy of [150] PLATE 44 Impulse water turbine. Bucket wheel for 56,000 h.p., 2,200-feet head, 250 r.p.m. Courtesy of the Allis-Chalmers Manufacturing Company Auvdwoy JOMO S][B J BIvSVINY 243 Jo Asajyinoy ‘autqin3 ‘d-y ooofoL sof Jauuns ay} ‘ a ‘ Pe. 2 Stee il baum | C00 Othe ~ Sidon cy ALVId PRIME MOVERS motion or both. To illustrate, in the old overshot water wheel a very large diameter was used. The water from the surface of the pond came over the top of the wheel into its buckets, which were gradually lowered to the bottom as the wheel turned. Practically all the energy of the high position of the water was thus given over to turning the wheel and its connected machinery. In the old undershot wheel, on the other hand, the water spurting out at the bottom of the dam gave up most of its energy of motion to the paddles of the wheel. WATER PowER Power from flowing water is now produced principally either by the Pelton wheel or by impulse or reaction water turbines. There is little difference in principle be- tween the Pelton wheel and the impulse turbine, though the latter has a plurality of nozzles for the impinging water. The Pelton wheel is particularly adapted to small streams falling great distances. In Switzerland there are found such installations with a head of more than a mile in the fall of water. A pipe to confine the water brings it to the wheel, where the pipe is constricted to a nozzle out of which the water issues with great velocity. It then impinges on shovel-like blades or buckets of specially designed curvature set radially on the outside of the wheel. Plate 44, illustrating an impulse turbine wheel, shows the peculiar shape of the buckets. The area of the buckets is about 10 times the area of the cross-section of the water jet. The curvature of the buckets is such that the water does not splash or spatter excessively but is gradually slowed up nearly to zero velocity as it turns the wheel. A rule usually followed is to make the diameter of the wheel in feet not less than the diameter of the nozzle in inches. Theoretically, the speed of the wheel at its circumference should be one-half the speed of the jet. In practice, a well-designed Pelton wheel has a peripheral st GREAT INVENTIONS speed of 0.47 of the jet velocity. From 75 to 85 per cent of the energy of the jet is made available by a modern Pelton wheel. The regulation of the water to suit variations in the load is somewhat difficult. The flow can indeed be checked by screwing forward a needle valve so as partially to close the nozzle. But a quick reduction of flow would be apt to produce a dangerous water hammer in the pipe, somewhat similar in nature to the water hammer often heard in steam radiators in which water is condensed, but far more powerful. To avoid this, the jet is often arranged to be deflected so as not to impinge centrally upon the wheel buckets. The deflection and the valving are made to co- operate so that the rapid adjustment to suit a quick diminution of load is first made by deflecting the jet, and then the appropriate reduction of the water flow by the valve is made slowly, with a simultaneous gradual restora- tion of the jet till it again impinges centrally. When the head of water is more moderate and the volume of the flow is large, as at Niagara, some other form of water turbine is usually preferred. Turbines are classed as reaction or impulse, according to whether, they operate by steady pressure, or (like the Pelton wheel) by the energy of the flow of water. In reaction turbines the water is de- flected by a complete encirclement of curved fixed guides onto curved vanes fastened to the circumference of a rotating wheel called the runner. The runner and deflec- tors are encased in a steel casing tightly fitting so that all the water must flow past the vanes. In most machines the axis is vertical, and the water may either flow vertically down the axis or radially inward or radially outward to produce its effect on the curving vanes. In the first case the shape of the vanes is somewhat like that of a screw propeller. In certain mixed types the water flow enters radially inward from the fixed vanes, is curved downward by the upper rotating vanes, and leaves the runner nearly vertically between screw-shaped lower rotating vanes. big? | PLATE 46 ee , > r) o » . > 2 ’ ’ 2 he Wet Ne, pecs .* Niagara Falls. Butterfly valve to control water flow. Courtesy of the Niagara Falls Power Company Q ; cya fo . 5 stpS Auvduiosy IOMOd ST[PH BIVOEIN] 94} jo Asaqinosy JOUUNI surging d Y oooSol ST[PH BIVOBINT sega soso _ sts Rigen | ‘ * a et 3 ¥; ee ail LY ALV Id Aueduio7 Jamog S][ey BIVSVIN' 943 Jo Asazinoy ‘punossyoeq ay} ul UMOYS YoJsUag *jaef Lh sJOJOUIVIP aTOYAA ‘yoog $1 Suruado puvy-asay fo Jajawiviq] “Sursvd paayM WIOJ 0} payquiasse Bulaq sSuysvg ‘syfey wavsviny 8h ALVWId Auedwioy saMog Slee] BIVSLIN' 9Y} JO Asajyinod *autqing ‘d-y ooofod JO MATA [BUONIAG “STV vAIVBINT = 6b ALVId PRIME MOVERS The inward-flow turbine is preferred on account of the greater compactness of construction of its runner. In the vertical-reaction turbine the passages are filled with water at all times. However, the outflow tube, called the draft, is of enlarged size and of a downward curving siphon form, so that a partial vacuum may be produced beneath the runner. Yet the machine works nearly as efficiently when fully submerged. Thus it is adaptable to great differences in the water level of the discharge, such as occur with the spring freshets. The impulse turbine differs from tne Pelton wheel only in that it operates by the impinging of many jets of water from fixed guides onto curved vanes all around the cir- cumference of the runner. It can not work submerged but must be so high that it is never reached by the level of the discharge. In the United States the impulse turbine is little used, for under the circumstances most favorable to it the Pelton wheel is preferred. Among the great hydroelectric power installations the most interesting on account of location is at Niagara Falls. The Governments of the United States and Great Britain, solicitous to preserve the grandeur of the Falls and the navigation of the Great Lakes, prohibited any increase in the volume of water diverted for power purposes for sev- eral years after 1905 until an international committee should report on the subject. In accord with the findings of the International Waterways Commission in the Boundary Water Treaty of 1g10 between the United States and Great Britain, “the high contracting parties agree that it is expedient to limit the diversion of waters from the Niagara River so that the level of Lake Erie and the flow of the stream shall not be appreciably affected.” Having regard for vested rights in diversions already made, the treaty provides that the limit of diversions for power purposes shall be 20,000 cubic feet per second from the American side and 36,000 cubic feet per second from the Canadian side. [153] GREAT INVENTIONS These limitations force the operation of the present power plants at considerably below their combined capac- ity. The Edward Dean Adams plant on the American side, with a capacity of 105,000 horsepower, is idle, held in reserve for emergencies. The total capacity of all the active plants is now: American side, 452,500 horsepower; Canadian side, 1,098,950 horsepower. A considerable part of the power manufactured in Canada is used in the State of New York. The active American-side power plants are the three units of the Schoelkopf Station of the Niagara Falls Power Company, named after Jacob F. Schoelkopf. He, with associates, organized the Niagara Falls Hydraulic and Manufacturing Company, the forerunner of the pres- ent company, and purchased in 1877 the hydraulic canal which had been constructed by Woodhull, Bryant, and others about 1853. This canal, starting near Port Day, above the American Falls, runs across the country about a mile to a point on the Gorge about a mile below the Falls. Originally a small canal, it has been broadened and deepened to 100 feet wide and 20 feet deep. In ad- dition, a tunnel 32 feet in diameter runs from Port Day to Schoelkopf 3C station. Inclined penstocks lead down to the bottom of the Gorge to the turbines of the three Schoelkopf stations. They contain, respectively, thirteen 10,000-horsepower units, three 37,500-horsepower units, and three 70,000-horsepower units. The turbines are double-runner Francis type, horizontal-axis machines, operating under about 210-feet head. They actuate direct-connected generators furnishing 12,000-volt, three- phase, 25-cycle alternating current. Power from American and Canadian sources is transmitted as far south as Bradford, Pa., and as far east as Syracuse, N.Y. On the Canadian side the Toronto Power Company, the Ontario Power Company, and the Hydro-Electric Power Commission of Ontario have a combined capacity of 869,- 350 horsepower. The Hydro-Electric Power Commission [154] Auvdwios saMog sy[ey vavseryy ayi Jo Asazinod “var ay} 3 ‘d-y coool Jo da1y} “punoisai0j ayy ul sioyesouas ‘dey oosL€ sary, “YOnRIS jdoypaoyog Jo solazUy “STP vAILSVINT 0S ALV Id PLATE 51 Conowingo power and distributing station. Model in the National go } - Museum of 378,000 h.p. hydroelectric station on the Susquehanna River PRIME MOVERS has the latest and by far the most powerful of all the plants. They take the water from near the mouth of the Welland River and transmit it by canal 8 miles to a point on the lower Niagara Gorge only 2 miles above Queenston. In this way they obtain a head of 305 feet. Their installa- tion comprises five 5$5,000-horsepower units and four §8,000-horsepower units of vertical shaft, single-runner Francis turbines, driving five 45,000 and four 55,000 KVA direct-connected generators of 12,000 volts, three- phase, 25 cycles. The voltage is stepped up to 110,000 volts, and current is supplied to municipalities in Western Ontario under public ownership auspices. Plates 45-50 illustrate some of the interesting features of the hydroelectric power installations at Niagara Falls. Plate 51 shows a model in the United States National Museum of the Conowingo hydroelectric installation on the Susquehanna River. Heat Power The conversion of heat energy into mechanical energy is accomplished through the expansion of gases. Heat may be developed by an outside boiler, or within the engine by explosion. Water heated by coal is used principally in the former case, and fuel oil or gasoline in the latter. Water boils at higher and higher temperatures as the pressure upon it increases, as is shown by the following table which starts with atmospheric pressure. 336 428° 106 332° Pressure, lbs. per sq. in. | 196 | 258 430 452° 23 236° fs) 308° 145 356° 15 212° 35 260° 52 Boiling temperature F. 284° 380°! 404° Steam in presence of boiling water at whatever tem- perature is called saturated steam, and it contains droplets of water thrown up by ebulition. Engine boilers usually have special pipes in which the steam is superheated to evaporate the contained water, and the steam freed from [155] GREAT INVENTIONS ainssoid wies}s SurysoA spunod $1£ ‘aovyzins JopIog 3005 orenbs o61'S ‘xayo3s a3vIS UTeYD *6761 Jo UOTIETTeISUT yeadky, ‘mousing fo 4719 "g's woy SsapIoq sepnqn3 xXoojIAA Pue yoooqeg “zl ‘ong yeryouds Buiatup 124045 quawzsedwos ydea jo pua yea ye saduieg © spy syeug uieyD) - smauas Bunsnfpe yax20udg 8c-61 | BP | mars ee Jofonuoy “Ayuapuadapur psyesedo quawypedwias ysea ‘suadwep jenpiaipul Aq pajjouqu0> J Si yoea UI iy “saxog ysejq © JJOM-apis Woy spUauedwWod IU We BE O©VOOOOD ‘wsiueyray . ~ TEAOwad sy Buryesado uax035 4 SOXOD W024 = 1PM APIS , X08 JeEM } 1PM SOP f Iq uoladsLy poumpuey fq payeusdo =a ele erel @a1nag Buigyr 3je9 “UUO) 440-M0/g i 7 fc Wemespy pou Burjeuado. wing Pri ; NM 9PM, ANRA HEY) Pej xOguiy4ex0}5 —f = 400g aqny yuosy ot om dnouB: ucqejnBay pue $305! MTA se sean sug i . opis Jeau | “WUO’ 440-Mo} | Sree wrsg pus) || RG ee odes aajen ozs paad| | | i 0} voyeinBayuazem@AN\ SY sazeig i Plu] wears oes woy adid paay} ¥f) ysems EF Jeqeaysedng sadigdugin i sojeinBay Fes 4 6.2009 gn, ueey (-----L--= 2 : Re of A N, LY . Suapeay snonuts ays 7Yyona4y4 JozeM P2ad i 5 | ee BNA M2849 pai ae f = aSeg uszoy/ Te FSO wg 437e2M 7B wWee}s saqny Buizejnoury ueg keds Je 4jEjNGay paay bee sane, Mayes xajdwig 2 adiy Aig AAIRA WeS]S ULeYy [ 156] PRIME MOVERS water is called dry steam. Condensation by cooling within the engine is one of the difficulties in steam engineering. Steam boilers are of two types, called water-tube and fire-tube boilers. In the former the water to be boiled is contained in part in the bottom of a nearly horizontal cylinder, in which the steam occupies the top. The re- mainder of the water is contained in a circulatory system of numerous inclined pipes which are bathed by the heated air and other gases from the fire. Figure 32 shows a Babcock and Wilcox tubular boiler of this type photographed from the collection of the United States National Museum. In the fire-tube boiler there are no water tubes. The heated gases are drawn by strong draft through and through tubes which honeycomb lengthwise the cylinder containing the water and steam. This type is used on locomotive engines. Steam under the high pressure produced by the high temperature of the boiler contains much potential me- chanical energy. It is like a drawn bow ready to let fly the arrow. When a fixed quantity of steam is admitted and allowed to expand against a piston within a cylinder, the useful work is measured by the product of the pressure into the change of volume. But since the pressure con- tinually falls as the steam expands, the measurement of work is not a simple matter of arithmetic, but involves calculus. We shall, therefore, refer interested readers to treatises on thermodynamics for the demonstration of the curious and important formulae which lie at the basis of steam engineering, and indeed of internal combustion engineering also. Yet there are certain conclusions of great interest which we can hardly pass over. All heat engines are subject to the law proved a century ago by the distinguished French physicist, Nicholas Leonard Sadi Carnot, who died in 1832 at the early age of 36 years. His ‘“Reflexions sur la puissance motice du feu,” published in 1824, contained the demonstration of his famous “‘cycle,” wherein he shows what is the maxi- [157] GREAT INVENTIONS mum possible efficiency for the absolutely perfect heat engine, which, of course, is not reached by actual heat engines of any kind. In a later expression of it, after Sir William Thomson had introduced his absolute tempera- ture scale, the maximum efficiency is stated as the differ- ence between the temperatures of heat received and heat rejected divided by the absolute temperature at which heat is received by the working medium used in the engine. To illustrate, suppose a steam engine receiving steam at 600° F. or 1060° Abs. F. rejects its steam by condensa- tion at 100° F. or 560° Abs. F. Then if the engine were absolutely without losses by friction or mechanical in- efficiency of any sort, its highest possible efficiency in the use of the steam to produce mechanical work would be 1060— 560 1060 internal combustion engines would not be subject to Carnot’s principle, but actually they are. All heat engines of whatever nature are limited in their maximum efficiency by this consideration of temperatures. It is clear, therefore, that the higher the temperature from which an engine can work, and the lower the tem- perature of its exhaust, the greater its possible efficiency. High initial temperature of their exploded gases is one cause of the high efficiency of gasoline and oil engines. Another favorable factor for the economy of fuel in these engines is the combustion of fuel within the engine itself, instead of in a separate boiler, so that no loss occurs in heat transportation. Recently Doctor Emmet of the General Electric Company has devoted much time and thought to the successful development of a new form of turbine engine in which mercury vapor is employed instead of steam and used at a much higher initial temperature than will ever be possible with steam, because steam dissociates at 700° F. In this way Doctor Emmet has obtained an efficiency practically as high as that of the gasoline engine, cr even the Diesel oil engine. [158] , or 47 per cent. It might be supposed that PRIME MOVERS Good bituminous coal produces about 14,000 British thermal units of heat per pound, and gasoline and heavy fuel oils produce from 18,500 to 20,500 of these heat units per pound. This is equivalent to saying that to burn completely a pound of coal will produce heat enough to warm 14,000 pounds of water 1° F. It was shown by the experiments of Prof. H. A. Rowland, of Baltimore, about the year 1875, that 1 British thermal unit of heat is produced by the expenditure of 777.5 foot-pounds of work. A horsepower is equal to 550 foot-pounds of work per second. The best recent engine practice employs a combination of the mercury turbine and steam turbine so as to use advantageously for steam the heat rejected from the mercury. A mercury steam installation has recently produced mechanical energy at the rate of 2,600,000 foot-pounds per 7,000,000 foot-pounds mechan- ical equivalent combustion value of coal. This gives 37 per cent efficiency—comparable, as we shall see, with the Diesel oil internal combustion engine. STEAM ENGINES Prior to the inventions of James Watt the steam engine (then called fire-engine) had been constructed by Thomas Newcomen for pumping. In Newcomen’s device, steam at about atmospheric pressure pushed upward a piston in a vertical cylinder. At the top of the cylinder a jet of cold water was thrown into the steam within the cylinder under the piston, thus condensing it, and the weight of the atmosphere brought the piston down. At the bottom, steam was again allowed to enter, driving out the water and raising the piston a second time. James Watt (1736-1819), having been engaged to repair a Newcomen engine, perceived the great waste of heat involved by cooling the cylinder and piston with water each time the steam was condensed. His patent of 1769 is so revolutionary and so clearly expressed that [159] GREAT INVENTIONS it will be of prime interest to quote from it the first four and the last claims. My method of lessening the consumption of steam, and consequently fuel, in fire-engines, consists of the following principles:— First, That vessel in which the powers of steam are to be employed to work the engine, which is called the cylinder in common fire-engines, and which I call the steam-vessel, must, during the whole time the engine is at work, be kept as hot as the steam that enters it; first by enclosing it in a case of wood, or any other materials that transmit heat slowly; secondly, by surrounding it with steam or other heated bodies; and, thirdly, by suffering neither water nor any other substance colder than the steam to enter or touch it during that time. Secondly, In engines that are to be worked wholly or partially by condensation of steam, the steam is to be condensed in vessels distinct from the steam-vessels or cylinders, although, occasionally communi- cating with them; these vessels I call condensers; and, whilst the engines are working, these condensers ought at least to be kept as cold as the air in the neighbourhood of the engines, bv application of water or other cold bodies. Thirdly, Whatever air or other elastic vapour is not condensed by the cold of the condenser, and may impede the working of the engine, is to be drawn out of the steam-vessels or condensers by means of pumps, wrought by the engines themselves, or otherwise. Fourthly, 1 intend in many cases to employ the expansive force of steam to press on the pistons, or whatever may be used instead of them, in the same manner in which the pressure of the atmosphere is now employed in common fire-engines. In cases where cold water cannot be had in plenty, the engines may be wrought by this force of steam only, by discharging the steam into the air after it has done its OiiGe: < ets Lastly, Instead of using water to render the pistons and other parts of the engine air and steam tight, I employ oils, wax, resinous bodies, fat of animals, quicksilver and other metals in their fluid state. Thus we see that Watt introduced the separate, cooled condenser, and the vacuum applied thereto. He also introduced the insulated steam jacket to retain the heat of the cylinder. He also suggests the use of steam to force back the piston after it has made its upward stroke, i.e., the double-acting engine, and proposes both condensing and noncondensing engines. We still see in the modern locomotive a noncondensing engine. He also avoided [ 160 | PLATE 52 James Watt PLATE 53 1SS ge H. Corl Geor PRIME MOVERS sroysiqnd “ouy ‘suog 29 AaqiAA uyof puv sJoyjne ay jo uorssiwsod Ag ,,*Sulsoausuq [eoUeYyoeTW,, SPY “WM “JOD “IMerT Wor ‘auidue wea3s Suyvoosdioas ajduns yo wesseiqg “ff ory g 2 Ee Jou t fe | [meme wwe fk tp SSE NO EG [ 161 ] GREAT INVENTIONS the use of water to seal the piston. A little later he turned pure reciprocating motion into the circular motion of a shaft and flywheel. Watt never used high pressure steam, hardly indeed as high as atmospheric pressure. The science of thermodynamics was unknown until nearly a century later, so that he probably was quite unaware that the efficiency of the engine increases greatly with the increase of temperature of the boiler steam. Oliver Evans in America and Richard Trevithick in England, however, employed high pressure steam about 1795 to 1800, though of course unacquainted with the theoretical basis on which its advantage rests. A simple reciprocating steam engine works on the principle shown in the diagram, Figure 33. At the posi- tion of the piston, a, as shown, steam is just entering the left-hand end of the cylinder to drive the piston toward the right. At the point, 4, the slide valve, c, moving to- ward the left, closes the port and stops further entry of steam. That already in the cylinder continues to expand and push the piston toward the right. During all this time, the steam has been escaping to the vacuum condenser from the right-hand end of the cylinder out of the exhaust port, d. But as the valve moves farther to the left, the exhaust port is closed to communication with the right- hand end of the cylinder, and the residue of steam there begins to be compressed, tending to slow the piston to prepare for stopping. Still further motion of the valve to the left opens the right-hand end of the cylinder to the live steam from the steam chest, e, and at about the same time opens the exhaust port for the escape of steam from the left-hand end of the cylinder. The piston now reverses, and the valve presently reverses also. The return stroke is made after a similar manner. The remainder of the engine, including pitman, f, crank, g, flywheel, 4, and valve linkage, 7, 7, is clearly indicated in the diagram. Such an engine is about four times as wasteful of steam as the best reciprocating engines. The slide valve develops [ 162 |] PRIME MOVERS much friction owing to the heavy steam pressure upon its back; the steam wasted into the exhaust still contains most of its power; the compression of residue steam at the ends of the stroke takes energy, and many other losses occur. George H. Corliss (1817-1888) in 1849 invented valuable improvements in the steam-engine valve mech- anism, which added greatly to its efficiency. He is re- garded as the third great contributor to the improvement of the reciprocating steam engine, following James Watt and Richard Trevithick. Unlike most of the discoverers and inventors mentioned in this book, George H. Corliss had no occasion for a youthful struggle with poverty. His father, Dr. Hiram Corliss, was a skillful and successful physician and surgeon, intellectual in his tastes and of strong religious character. His son George was born at Easton, N. Y., but Doctor Corliss removed to Greenwich, N. Y., when George was 8 years old. Though the family was in good circum- stances, George Corliss obtained employment in a general store as soon as he had completed his common school edu- cation. He soon considered it desirable, however, to carry his studies further. This he did for three years at Castle- ton, Vt., but with rugged independence, he preferred to earn his way there by his own work. At 21 years of age he became the proprietor of a general store at Greenwich, where he sold clothing, groceries, hardware, etc., for some years. The failure of the seams in a pair of boots he had sold led him to attempt the in- vention of a boot-sewing machine. This he developed and patented in 1843, some years before the famous sewing machine invention of Elias Howe. Corliss’ machine in- volved more complex devices than Howe’s and did not come into general use. It was his attempt to construct and dispose of his sewing machine which led Corliss into the engine field. Having spent much time and money fruitlessly in this effort, he accepted work as a draftsman and designer in the shop of [ 163 ] GREAT INVENTIONS Fairbanks, Bancroft & Company at Providence, R. I. Within a few years Corliss bought a share in the business, and, on reorganization, the firm became Corliss, Nighten- gale & Company. At 40 years of age, in 1857, he became sole owner, and the company became known as the Corliss Steam Engine Works. After this, Corliss lived 21 years, a man of the highest integrity, honored and trusted by all, kindly to men and animals, deeply religious, and promi- nent in good works and liberal benefactions. The Corliss valve mechanism, patented March 10, 1849, led to an improvement of about 25 per cent in steam- engine efficiency. Its construction ensured perfect control of the steam consumption by the engine governor without waste of steam, which prior to that time had been prodigal. Instead of rigidly coupling the steam valves to the exhaust valves as in the simple slide-valve device shown in Figure 33, Corliss provided four separately operating valves at the four corners of the cylinder section. Moreover, he used a linkage of such a character that each valve re- mained nearly stationary during the comparatively long part of its cycle when there was no occasion to move it. This reduced greatly the friction loss produced by the heavy steam pressure on the backs of the valves. Also his linkage was adapted to move each valve very quickly when the time arrived to move it. This gave definite, quick cut-offs of steam with proper timing. Finally, the engine governor, whose balls rise by centrifugal force when the engine runs too fast, was connected by a linkage with the steam valves in such a manner that the higher the balls rose the earlier the cut-off, so that less steam was ad- mitted to the cylinder. The mechanism was further im- proved, as specified in the Corliss patents of July 29, 1851, and July 6, 1859. The Corliss engine mechanism would require more space to make its action and advantages fully clear than we can well allot to it in this book. So certain was Corliss of the advantage of his engines that he sometimes consented to install them under con- [ 164 ] PRIME MOVERS tract to accept nothing in payment but the amount saved in a certain number of months through their economical use of fuel. In one instance a purchaser who had made the contract to pay the amount saved during two years was glad to settle for twice the market price of the engine, instead of the much larger sum demanded by his contract. At the international exhibition held in Vienna in 1873 George H. Corliss received for his engine the Grand Diploma of Honor, although he had made no exhibition there of machinery of any kind. While others were making great fortunes out of war contracts, he constructed at exact cost for the United States Government the great iron ring on which the turret of Ericsson’s Monitor re- volved in its famous fight with the Merrimac. For the Centennial Exposition of 1876 at Philadelphia, he con- structed gratuitously at a cost to himself of about $100,000 a 1,400-horsepower steam engine which furnished the en- tire power for the exposition. He stipulated, however, that the exposition should not be open on Sundays, as he considered that a desecration of the day. We may conclude our notice of George H. Corliss with the following quotation from London Engineering in 1888, only 40 years after Corliss’ first engine patent. The quotation shows how very quickly the merit of the Corliss engines brought out in the fifties forced the recognition of foreign engineers. By the death of George H. Corliss, America has lost the best known engineer she ever produced. In all the countries of the world where steam engines are employed, the name of Corliss has been heard, and ranks next in familiarity to that of Watt. Indeed it has become so much a part of our technical vocabulary that many engineers will learn with surprise that little over a month ago the owner of it was not only alive, but was the active head of the Corliss Steam Engine Works, of Providence, R. I. Many men verging on middle age found the Corliss engine an established fact when they entered on their apprenticeships, and hence they have been disposed to class its invention with the events of ancient history, and its inventor with those who are dead or superannuated. [165] GREAT INVENTIONS The device of multiple expansion in the reciprocating steam engine is very old. J. C. Hornblower constructed and patented in England an engine of two cylinders, in which the steam entered first a smaller cylinder in which it was partially expanded, and from the exhaust passed over into the larger cylinder and was further expanded. Hornblower, however, could not compete successfully with the Watt and Boulton Company. Later on, in 1804, A. Woolf employed a two-cylinder engine. These inventors recognized the mechanical advantage of dis- tributing the thrust of the piston more uniformly during the cycle by the use of two cylinders. But a principle on which the advantage of multiple expansion over single expansion mainly rests could not have been known until after the development of the science of thermodynamics by Joule, Clausius, Sir William Thomson, and Rankine, after 1849. As we have stated above, expansion is necessarily attended by cooling, and cooling of the steam draws heat from the walls of the cylinder and piston. Accordingly, after the exhaust occurs these walls are much below the temperature of the incoming high-pressure steam. But if that steam is saturated, then any lowering of its tem- perature by contact with cooled metal produces con- densation to the form of water, with loss of expansive force. By subdividing the expansion between several cylinders, the difference of temperature between the metal and the entering steam in all the cylinders is diminished, and consequently the condensation is reduced. Two other devices to reduce losses by condensation are the steam jacketing of cylinders introduced by Watt, and the superheating of steam by exposure to the furnace gases, in pipes well separated from the water circulation, before conveying the steam to the engine. Furthermore, a part of the gain in efficiency in the Corliss engines came about from locating the steam valve well apart from the [ 166 ] PRIME MOVERS ssoysijqnd “ouy ‘suog 2 AIIM UYOL puv Joye 143 jo uoisstuad Ag ,,"Sursoursuyq peorueyoeyA,,, SJ[PYOITAL “V “M “TOD “3Ner] wor “ourqiny wes3s SuCsIey jo wieiseiq ‘) ‘oUIgIn} WEd3s SI}AND Jo WeIsvIg ‘gq ‘sUIqINy UIva}s [BART aC] JO weisviq "y ‘rl ‘ong 9 z:) v Ht | o9 5 QR re x ms & 8 noe g ry mh fw ‘ + > Ss ee * 8 Ve OINSSIID UEDLS a8 & % % Se Se eo g< YS aS § % G BS > OMNSSIAS G os WEIS N ie % 2 Ly SWAY TITLLTTL CL JAVA a 1 SS SS SS aunssasd SS == 15 Si anssasd PRS | 1671 GREAT INVENTIONS cold exhaust valve, thus diminishing the loss caused by condensation of the hot steam. Many inventors have attempted to avoid the recip- rocating motion of the piston in its cylinder, but the development of rotary steam engines did not advance until the application of the turbine principle. As there are reaction and impulse water turbines, so are there reaction and impulse steam turbines. Applying the principles of thermodynamics, Gustaf de Laval about 1889 computed the form of nozzle which would cause steam to issue at maximum velocity from a chamber at given pressure and temperature. He then employed this high- speed steam issuing with a velocity of some 4,000 feet per second to drive an impulse wheel with numerous curved blades upon its circumference, much after the method of the Pelton water wheel as shown in Figure 34 A. Several such jets may be situated opposite different sectors of the wheel. This device has for most purposes the disadvantage that it produces too high speeds of the wheel to be readily available for driving machinery. However, relatively small losses in reduction gearing of certain designs make possible such applications. In a modification of the impulse steam turbine by Curtis the steam first issuing from many nozzles in high-speed jets is directed tangentially against moving blades of a special crescentlike curvature. Thence the jets issue in a contrary direction against oppositely curved crescent- shaped fixed blades, which again reverse the jets toward a second set of moving blades. The same device is again repeated. The issuing stream, now at lower pressure, may be collected and directed through a new series of nozzles upon a second series of movable and fixed blades. The scheme is shown in the diagram, Figure 34 B. The advantage of it is that much less speed is imparted to the rotor, and the friction of the steam on the blades is much less than with the De Laval turbine. In large sizes, Curtis turbines are much used to drive electric generators, [ 168 | PLATE 54 Steam turbine, Parsons type. Top view. Capacity 30,000 kilowatt, 1,800 r.p.m. Courtesy of the Allis-Chalmers Manufacturing Company PRIME MOVERS and they have an efficiency quite equal or perhaps even superior to the best triple-expansion reciprocating engines. The reaction turbine invented in 1884 by Sir Charles A. Parsons (1854-1931) antedated the De Laval impulse turbine by about six years. Sir Charles inherited his engineering genius. He was the fourth son of William Parsons, third Earl of Rosse, whose seat, Birr Castle, Parsonstown, Ireland, is famous as the site of his 6-foot reflecting telescope, which he completed and mounted there in the year 1845. Sir William Herschel had been the principal maker of reflecting telescopes of speculum metal before Lord Rosse, but his largest useful one was of 18 inches diameter. He left no account of his methods of casting and figuring specula. Lord Rosse, therefore, began anew about 1825 working out experimentally the best composition of the metal, which he fixed at four atoms of copper to one of tin, or by weight 126.4 parts copper to 58.9 parts tin. He then invented and developed a grinding and polishing machine which he described in 1828, and in 1839 completed and mounted a 3-foot reflecting telescope in which he built up the mirror of many thin plates backed by brass of equal expansibility. Not satisfied, he improved the methods of casting specu- lum metal, and after casting a solid 3-foot mirror in 1840, he accomplished the casting of the great one of 6 feet diameter in 1842. It was completed as a telescope in 1845, and was used with great success to reveal the forms of excessively distant nebulae, till then unknown. All the work of this difficult metallurgy and engineering was performed under Lord Rosse’s direction by the tenants and laborers on his estate. Less spectacular than his father’s great telescope, but of immense practical value to industry, was Sir Charles Parsons’s invention of the steam turbine. As stated by his son, Robert H. Parsons, in the London Times of September 21, 1931: “To any engineer conversant with power station practise the statement that without the [ 169 ] GREAT INVENTIONS steam turbine the electrical supply industry as we know it today simply could not exist is a mere truism.” He goes on to point out that the Parsons turbine exceeds the best multiple-expansion large reciprocating engine in coal efficiency; that in London 185,000-kilowatt turbo- generator capacity had been installed in space intended for a maximum of only 55,000-kilowatt capacity with reciprocating engines; that turbines are adaptable to any steam pressure from the very highest to the very lowest, their range far exceeding the possible range of pressures adaptable to reciprocating engines; and finally that while the largest reciprocating engine units do not exceed 10,000 kilowatts capacity, steam turbines in units of 150,000 kilowatts are already in use, and no limit to their capacity is yet reached. Figure 34C gives a sectional diagram showing the principle of the Parsons steam turbine. Steam, entering at high pressure, flows through alternate rows of moving and fixed oppositely curved blades, fastened circum- ferentially in the rotor and the casing. Clearance is only about 30/1,000 inch, so that leakage of steam is not large. As the steam expands, larger and larger passages are provided by a combination of two expedients. The diameter of the rotor grows larger, and the radial exten- sion of the blades grows greater. To balance the tendency always to push the rotor toward the exhaust end, as many equal enlargements of the rotor diameter are provided at the left as there are enlargements of the rotor at the right, and steam passages are provided between the balancing enlargements. Thus the pressures are equalized in opposite directions. On account of the smallness of the clearance, exact end- thrust devices must, of course, be prepared at the ends of the axis to prevent the rotor from touching the casing. These machines, contrasting with the De Laval impulse turbine, may be constructed for comparatively low speeds, that they may be direct-connected with the propellers in [170 ] PRIME MOVERS steamships. In order to back the ship, however, auxiliary turbines running oppositely are provided. Turbines may be used at any steam pressure and have been employed with great success to save the steam rejected by the exhaust of reciprocating engines, working at pressures from below one atmosphere downward. Double the out- put for the same amount of coal may thus be obtained in association with a noncondensing reciprocating engine, and §0 per cent additional power may sometimes be produced by the combination of a turbine with a con- densing engine. The Parsons turbine operates with from 75 to go per cent of the coal required for the same power in the best reciprocating engines, and gives a total effi- ciency in the best installations of about 36 per cent, equaling the Diesel internal-combustion oil engine. Plate 54 shows a top view, with casing removed, of a 30,000-kilowatt capacity steam turbine of the Parsons type, driving 1,800 revolutions per minute. INTERNAL ComMBuUSTION ENGINES We have been considering engines for which the working gas is prepared under high pressure in separate devices, generally in boilers. We take up now those in which liquid or gaseous fuel is sprayed or sucked, together with the proper amount of air for complete combustion, into the en- gine cylinder itself. Pressure 1s developed within the engine cylinder by the explosion of the mixture. In their earlier history such engines operated generally with ex- plosive mixtures of illuminating gas and air. In modern practice it is more common to use as fuel either gasoline or some heavy oil prepared from the crude oil products of the wells. Gas distilled from coal is also used. . A pioneer gas engine was devised by W. Cecil in 1820, but the earliest gas engines used to any extent commer- cially in England were those of Samuel Brown, beginning about 1823. A very valuable improvement was made in 1838 by William Barnett, who discovered the importance [171] GREAT INVENTIONS of compressing the explosive charge before ignition. Yet Barnett’s plan was not generally followed. As late as 1860, Lenoir, in France, began to build gas engines operating without preliminary compression. The more efficient Otto and Langen engine, though mechanically inferior, drove Lenoir from the field. Gas engines are generally, though not always, single acting—that is, all the gas expansion takes place on only one side of the piston. Almost immediately after Lenoir’s first constructions, Beau de Rochas in Paris in 1862 enunciated the fundamental order of events of the ordi- nary gas engine, which is the famous four-stroke cycle, often called the Otto cycle. This cycle comprises: (1) Suction of a charge of the explosive mixture into the cylinder during the first out-stroke; (2) compression of the mixture to several atmospheres pressure in the first in-stroke; (3) ignition accompanied by sudden pressure increase near the dead point, followed by expansion in the second out-stroke, which is the working stroke; and (4) expulsion of the burnt and expanded gases in the second in-stroke, which is the fourth and last of the cycle. Many gas engines have only a single cylinder, open at one end, and the connecting rod connects directly from the piston to the crank pin. Thus it vibrates through a considerable angle within the open end of the cylinder instead of being attached to a piston rod sliding in fixed guides to and fro, as is usual in steam engines. In the four-stroke cycle there is but one working stroke in four. The crank shaft makes two full rotations impelled by only one explosion in each cycle. To make the rotation of the crank shaft nearly uniform, despite the wide separation of the driving impulses, a heavy flywheel 1s fixed to it, or sometimes two such wheels. Two valves are provided in the closed end of the cylinder, one for the entrance of the charge, the other for the expulsion of the burnt and expanded gases. These [172] Lgi ‘eouaury ul 4ying aurlSua sv3 ysu 848 I V ul dying sul MH ss ALVId 56 PLATE Otto Dr. N. A. PRIME MOVERS h Tee 7, —— ar [ios en m= —— ee ay! > ab Gireduin. A oN ee Gas GES AN OZ inh G47 i ee A lta We 227 ee : ——___ Ai DVR as poral ( i s 167 ea YE \ 77a uu ee sco i a arf of a Zea iN Al ee ae, | __Vae Zs. ball) Zee Na : S MZ Ge." aid pA Pome z NOW BION ARS? Soe cae AIT lo : S4ixing Valve U = AE eZ aot 77 & | (©) Za Perl Ph } Z Asa AIP ai G =e —T aia’ Glam iy, 2a™ q z SS | % = ei) = 4 G SSH Wnt ISSSSS LL St le ~ EI AIA N \ Bae B\E ee N Pee] N er ud fT Th SSS KAA Wel \ Sie Sas SS mame lh SSS SSS SESS ESE SESE SEES SSS NAAAMANRAARRAASARRAAARAAAAAARAA NS Pa A MNS ARMREST PSE Po A EN Fic. 35. Sectional view of a vertical gas engine. From Lieut. Col. W. A. Mitchell’s “Mechanical Engineering.” By permission of the author and John Wiley & Sons., Inc., publishers [173 ] GREAT INVENTIONS valves are usually of the conical type, forced to their seats by springs and opened by rods called tappet rods, operated at the proper times by cams upon a cam shaft geared to the driving shaft. The firing of the explosive. mixture may be done by several methods. A flame or a hot tube connecting with the cylinder was formerly used, but the firing now is usually electrical. Either spark plugs with a spark gap, as in an automobile, or circuit breakers inside the cylinder head give the igniting sparks. In either case the igniting device is connected to the second- ary coil of a small transformer. Proper timing, which is very essential, is accomplished by a cam mechanism geared to the driving shaft. A gas engine operating on the principles just described is shown diagrammatically in Figure 35. On the shaft of the flywheel, a, is the crank, 4, from which goes the con- necting rod, c, to the piston, d. Rings are let into the piston at e to make a tight closure with the cylinder, f, which is water jacketed as indicated by the spaces, g, g, in order to keep the lubricating oil within the cylinder from burning too rapidly. Forced lubrication (not well shown in the figure) is usually resorted to between the piston and cylinder. The conical valve, 4, admits gas and admixed air when forced down against the pressure of its spiral spring, 7, by the lever, 7, operated by the rotating cam, k&. The exhaust port, /, is operated by the tappet rod, m, against the pressure of the spiral spring, x, when forced by the rotating cam, 0. The cams, & and 0, are timed to suit the four-stroke cycle by gearing (not shown) connected with the flywheel shaft. Plate 55 shows an engine constructed in 1878, the first gas engine built in America. With certain modifications the type of gas engine just referred to is used in multiple form with liquid fuel for automobiles and airplanes. These applications involve the use of the carburetor, a device to produce a proper mixture of liquid fuel and air. More elaborate timing [174] PRIME MOVERS devices are also required to ignite the explosive mixtures in all the cylinders at the right instants, and cooling devices, combining air and water as cooling agents, are arranged to prevent injurious effects of the waste heat. Otherwise, these gasoline engines follow closely the type of the four-stroke cycle gas engine just explained, which was devised by Dr. N. A. Otto (Plate 56), of Cologne, Germany, about the year 1876. There is, however, another type of internal-combustion engine suitable for employing both light and heavy oils without the use of a carburetor or sparking device. It was invented in 1892 by Dr. Rudolph Diesel (1858-1913). It will be recalled that oils such as kerosene and heavier distillates from the cruder oils of the wells have a critical temperature known as the “flash point.” If heated in air above that temperature they take fire spontaneously. In the Diesel engine, temperatures above the flash point of the oil used as fuel are obtained by high compression of the air introduced for combustion. A four-stroke cycle in such an engine would run as follows: On the first out-stroke air is drawn into the cylinder. By the first in-stroke the air is compressed to perhaps 500 pounds per square inch. Near the end of the stroke or dead point, oil is forced by very high pressure through atomizer nozzles into the compressed air. The jets of oil are placed so as to set up in the air a great turbulence which thoroughly mixes the fuel spray with the air. Owing to its high compression, the air is very hot and the fuel spray therefore ignites. On the out- stroke the cut-off of fuel is a little delayed so that during part of the working stroke the spray still continues to be forced into the air, burning as it enters. Thus the ex- pansion continues through the remainder of the working out-stroke. At the end of it the exhaust port opens, and the products of combustion begin to escape. The exhaust port still remaining open, the in-stroke begins and the products of combustion are nearly all swept out of the [175 ] GREAT INVENTIONS cylinder. The cycle is thus completed and then repeats itself. There are several variations from the Otto and Diesel cycles. Two-stroke cycles are sometimes used instead of four. In such cases the piston overruns the ports for the entrance and escape of gases, so that the piston acts like a slide valve in a simple steam engine. In certain engines two pistons, working in opposite directions, are used in a single cylinder. The mixture is exploded between them when they are nearest together. Several cylinders are frequently employed instead of one. Internal combustion engine cylinders must be cooled in order that they may be lubricated, and the cooling is usually accomplished by water circulation. For this pur- pose the cylinder is often cast with a hollow wall to contain the water. Some engines are double acting, the cylinder being closed at each end. In that case the piston rod is made hollow, and the piston itself is provided with canals through which water is forced. It is shown by thermo- dynamics that the efficiency increases with compression. As the advantage of high compression is very great, the pistons must fit without sensible leakage, and for this purpose they are encircled by expansive rings. Since no water is present on the cylinder walls, in contrast with steam engines, adequate provision must be made for oiling the parts. For this purpose either a forced circulation or a splash circulation of oil is provided, so that at every cycle the piston and cylinder are well lubricated. Although internal combustion engines are much used in manufacturing, their greatest applications, of course, are in automobiles and airplanes. Special forms have been invented for these purposes, in which extraordinary light- ness has been combined with extraordinary durability and certainty of action. As it was found unpleasant to ride with an engine of one cylinder, the automobile en- gines were very early constructed with four, then with six, and now sometimes with eight, twelve, or sixteen cylin- [176] PLATE 57 In the National Museum Liberty airplane engine. PLATE 58 Packard-Diesel airplane engine PRIME, MOVERS ders, so as to give a steady motion with a flywheel of only moderate inertia. The same multicylinder practice, even accentuated, was carried over into airplane engineering, i> SA pect arm aA) = | S ») Hloat } Needle Valve ) Flat (EY Ria ve Lach \ “y Float Needle Valve Seat ; y Oo} Ke SHaneree ? Bod KASASSSASSSASSYS pou JvoH pue asvlIIVs SUIMO} Sulmoys MIIA JOLIJUT ‘auUBYS auvydvas VOVWN £8 ULV Id SOTNVUOIOY IOfj 99} TUTWIO*) AIOSIAPY [BPUOTIE NT nee! jo Asajino7 “po9}soy Suisq vod aurjdvas jo TPPPW $8 ALVW Id MECHANICAL TRANSPORTATION Secretary Walcott of the Smithsonian Institution and others. The members (May, 1932) are: Josepn S. Ames, Ph. D., President of Johne Hopkins University, Baltimore, Md., chairman. David W. Taylor, D. Eng., Admiral (retired) U.S. N., Washington, D. C., vice chairman. Charles G. Abbot, Sc. D., Secretary of the Smithsonian Institution. George K. Burgess, Sc. D., Director of the Bureau of Standards. Capt. Arthur B. Cook, United States Navy, Assistant Chief of the Bureau of Aeronautics, Navy Department. William F. Durand, Ph. D., professor emeritus of mechanical en- gineering, Stanford University, California. Maj. Gen. Benjamin D. Foulois, United States Army, Chief of the Air Corps, War Department. Harry F. Guggenheim, M. A., American Ambassador to Cuba. Charles A. Lindbergh, LL. D., New York City. William P. MacCracken, Jr., Ph. B., Washington, D. C. Charles F. Marvin, M. E., Chief of the Weather Bureau. Rear Admiral William A. Moffett, United States Navy, Chief of the Bureau of Aeronautics, Navy Department. Brig. Gen. Henry C. Pratt, United States Army, Chief of the Matériel Division, Air Corps. Edward P. Warner, M. S., editor of Aviation. Orville Wright, Sc. D., Dayton, Ohio. The Honorable C. A. Woodrum of Virginia, Chairman of the Subcommittee of the House on the Independent Offices Appropriation Bill, made the following remarks on April 6, 1932: The National Advisory Committee for Aeronautics is composed of 15 members appointed by the President and serving without com- pensation. In order to insure that this body shall be thoroughly representative of all concerned with the advance of aviation, the law requires that there shall be 7 representatives from the Army, the Navy, and three other governmental agencies, and 8 members from pri- vate life who are eminent scientists or aeronautical authorities. This organization is charged by law with the supervision and direction of the scientific study of the problems of flight. It not only conducts scientific investigations in the laboratories provided by the Congress for its own use, but it coordinates the use of existing facilities of the Army and Navy air organizations, the Bureau of Standards, and educa- tional institutions in aeronautical research so as to use facilities to the best advantage and to prevent unnecessary duplication of effort. [ 233 ] GREAT INVENTIONS The continued development of aviation in progressive countries emphasizes its increasing relative importance for national defense and for purposes of commerce and transportation. The quiet effective work of the National Advisory Committee for Aeronautics is the most fundamental constructive activity of the Government in the develop- ment of American aeronautics, and is reflected in the continuous improvement in the safety and efficiency of American aircraft. The committee’s research programs embrace all the fundamental problems of military, commercial, and private airplanes. The committee’s research facilities are unequaled in any other laboratory in the world. Substantial progress will continue to be dependent largely upon well organized and directed scientific research on these fundamental problems. The United States is engaged in aviation upon a scale little realized by the Congress and the public. The following chart is illuminating: AGI, ocr isn ucoyeistoes SORE Mem sien Sees oy cere rae $70,677,406 NEW g MeR RA aoe aR ee San Bl Pee ar eee tree bec hc Si 9! 57,563,923 Post (OM Cee 2-- Md. ctliere Bh o Polat. LBS. DRAG AT 100 M. z O S bs < O di ie QO t) a er = ‘a “— fi y Cord E — Necking cords F — Comber board G — First leash f each repeat H — Shows an ruled fee) The effect u/ling down O simpre cord A Fic. 49. Diagram of a simple draw loom. Courtesy of the Royal Society of Arts separate leash is hung. Each leash has a long, thin lead weight at its bottom end; and in its center, instead of a string loop, a glass eye called a mail, through which a warp thread is entered. The comber board in the diagram is only pierced with 72 holes; consequently it is only for a warp of 72 threads. [ 283 ] GREAT INVENTIONS If it were for 72,000 threads of fine silk, it would not take appreciably more space in the loom. The drafted design at No. 2 is made on 18 lateral squares, so that it would repeat four times in the width of the web to be woven. In this comber board there are holes for four repeats of 18 leashes, but only six leashes of each repeat are shown in position, as more would confuse the drawing. The bottom board of the triangular box, C (Fig. 49, 1), is pierced with 18 holes, the same number as that of the threads in each repeat of the design. Let us suppose the comber board to be filled with leashes, one suspended in each hole; also that 18 cords are hanging through the holes in the triangular box at D. The monture builder now connects, with fine cord, the first, nineteenth, thirty-seventh, and fifty-fifth leashes, which are the first in every repeat, with the first hanging cord at D. He next takes the second leash in each repeat, and con- nects it in like manner with the second cord at D. He proceeds thus in regular order to connect leashes and top cords until he reaches the last of the repeats, leashes 18, 36, 54, and 72. When this work is done it is apparent that if any one cord at D is drawn up into the triangular box the corre- sponding leashes in every repeat will be drawn up through the comber board to a corresponding height. Moreover, if 72 threads of warp are entered in the leash eyes, the selected leashes as they rise will raise the threads neces- sary for the formation of the pattern shed. This is the essential portion of the draw loom, and so far is it from being obsolete that all the pattern-weaving looms of today, whether worked by hand or power, are identical with it. Thus the immense textile industry of modern times is indebted to and linked with the invention and industry of ancient China. I resume the explanation of the diagram of the draw loom, Figure 49, at the point, D, where the 18 cords are seen to enter the triangular box, C. This box is fitted up [ 284 ] HOUSEHOLD AND FARM INVENTIONS with pulleys, 18 in number. Each cord passes over a pulley and is seen again at E. The collection of 18 cords, called the tail of the monture, is then securely fastened to the wall of the workshop, or some convenient strong post. Between F and F another series of 18 cords, called the simple, is tied to the tail series and fastened to the ground. A simplified diagram, showing one cord in all its parts, is given in No. 4. Now, it will at once be seen that if the cord, 4, be pulled down by an assistant standing at the side of the loom, the eyes of the leashes, G, through which the warp threads pass, will be pulled up. It is necessary, then, in the simple, to have as many cords as there are threads or groups of threads in each repeat of the comber board. And it is possible to weave on the loom any design, of whatever length, that can be drawn on the number of threads arranged for in each repeat. If we turn to the design No. 2 we shall see that it is drawn on 18 squares, and if we compare the design with the loops tied from the large guiding cords to the separate cords of the simple, we shall see that they agree. The black squares in the design represent a tie. Take the first line, beginning at the left-hand side. Here are six black squares. If we follow the dotted line to the first cord of the simple, a group of six ties will be found. Then passing over six cords, a group of four ties are found which corre- spond with the four black squares in the third division of the sketch. By means of these loops the drawboy, as he was called, selected the cords for pulling down, and, having gathered them together on the prong of a large fork, to which a lever was attached, he pulled the lever and drew the leashes up, thus opening the shed for the weaver’s shuttle. The design had to be tied up on the simple cords line by line before weaving could commence; but when this was once done the drawboy had only to pull the cords, [ 285 ] GREAT INVENTIONS in regular sequence, in order to repeat the design con- tinuously in the length of the web. On this mounting of the loom entered with single threads of warp any possible interlacements of warp and weft can be worked out. It may well be called, therefore, the most perfect loom. Its only limitation is in the size of the design. It would require a simple of 400 cords to tie up a design one inch wide for a silk web 400 threads to an inch. ill. THE JACQUARD MACHINE; POWER-DRIVEN LOOM In the early part of the eighteenth century, weaving, as a handicraft, reached in Europe its point of highest perfection. France, England, and Italy were the chief countries in which it was practiced. At that time, in England particularly, the condition of the textile crafts- man, of whatever grade, seems to have been better than at any other period of which we have record. The weaver of the eighteenth century was a prosperous and respect- able tradesman, whether working in the secluded country village, in the suburbs of the great towns of the north and east, or near the metropolis in the pleasant district of Spitalfields, notable as the silk-weaving quarter of London. This happy condition of the weaver in the eighteenth century declined to one of misery in the nineteenth. The economic causes of this change are not far to seek, but form not part of my subject. I only refer to this period of prosperity, as it marks an important stage and change of direction in the development of the loom. Hitherto the motive of inventors was to increase the scope and perfection of the loom as a pattern-weaving tool. The perfection attained and the care bestowed on loom construction are shown in the beautiful illustrations of Diderot’s Dictionary and other technical works of the period. During the latter portion of the eighteenth century, and since, the chief purpose of invention has [ 286 ] HOUSEHOLD AND FARM INVENTIONS been, not excellence of work and extended capacity of the loom, but economy of time and cheapening of production. The first indication of the coming change in the broad- weaving trade was given as early as 1687, when Joseph Mason patented a machine which he described as “an engine by the help of which a weaver may performe the whole work of weaving such stuffe as the greate weaving trade of Norwich doth now depend on, without the help of a draught-boy, which engine hath been tryed and found out to be of greate use to the said weaving trade.” It is necessary to the understanding of the mechanism of the important machine which superseded it, to have a general idea of this drawboy machine. In order to give this idea, however, I must first describe the work of the human drawboy. In a rich silk loom there were often as many as two or three thousand lead weights, called lingoes, hanging three to each leash of the monture. These weighed altogether a couple of hundredweight. On an average half of them had to be drawn up at every line of the design. Moreover, their dead weight would be so increased by the friction of the multitude of cords and pulleys that the boy would have to raise and hold for several seconds a weight equal to a hundredweight and a half. This would, of course, be impossible but for some mechanical help. The implement devised for the boy’s assistance was called the “drawboy’s fork.” This is shown in Figure 50. The vertical lines in this diagram represent the cords of the simple. To the left is a solid stand having two broad uprights joined together at the top by two parallel bars. 74 is a block of hard wood, which fits between the bars, and is held in position by four pairs of small wheels. These not only support it but allow it to run freely from end to end of the stand. This block with the fork and lever attached, is shown separately at HE. The fork and lever are hinged to the block at its top and can be moved from the vertical [ 287 ] GREAT INVENTIONS to a horizontal position. When about to be used the block is moved till the points of the fork are just beyond the backmost cord of the simple, the lever being in an upright position. By means of loops tied to the simple, the required cords are drawn forward and the upper prong of the fork inserted in the opening thus made, as shown Be D Fic. 50. The drawboy’s fork. Courtesy of the Royal Society of Arts in Figure 50. Then, grasping the lever, the boy draws it down and holds it. The result of this is that the selected lingoes and leashes are drawn and held up. At No. 2 three sections of the simple are shown lettered B, C, and D. At B the cords are at rest. At C some cords have been selected and the fork inserted. At D the lever has been pulled over and the cords drawn over with it. Figure 51 shows the mechanical drawboy, a machine invented in the seventeenth century and improved during the eighteenth. It was attached to the pulley cords of the loom, on which, when the machine was used, the tie-up [ 288 ] "H ON “dozsayouryy ‘Auvdwos SuLnjovjnuvyy Svaysouy “QUIYIVUL BULAVIM Pd}SIO AA Lo ALV Id HOUSEHOLD AND FARM INVENTIONS of the design was made, instead of on the simple. The active part of this machine is the pecker, which by means of two treadles and some little mechanical arrangements had two movements: (1) It rocked from side to side; (2) it moved, as it rocked, along the machine from one end to the other. Through holes in the side cross-pieces of the frame strong cords terminating in heavy weights were hung. To the tops of these cords the loops of each row of Fic. 51. The mechanical drawboy. Courtesy of the Royal Society of Arts tie-ups were attached in regular succession. Only two rows are shown connected in the diagram to prevent con- fusion of lines. The pecker had a deep notch cut in its points and was of such a size that as it rocked the cord toward which it inclined caught in the notch. At the center of [ 289 ] GREAT INVENTIONS the cord a large bead was fixed. When the rocking pecker came in contact with this bead it pushed it and its cord down and held it until the second treadle moved the pecker in the opposite direction. As the pecker traveled along the shaft each cord was drawn down in its turn, thus opening the shed, line by line, for the working out of the pattern. The number of lines in the length of a design, of course, had to correspond with the number of cords in the ma- chine. The drawboy machine was not to any great extent used for the purpose for which it was intended, viz., to supersede the drawboy of the compound figure weaving loom. I suspect the boy was useful in many ways about the loom, and, moreover, his wages would be no great matter. But late in the eighteenth century, and well into the nineteenth, the machine received a good deal of at- tention and was improved and adapted for use with the treadle hand loom. It enabled the weaver to work any complicated system of heddles, for small-pattern fancy weaving, with only 2 treadles instead of 20 or more. Further improvements were made later, but it was finally superseded by the famous machine which was perfected by Joseph Marie Jacquard, and known in England as the “Jackard” machine. There can be no doubt that it is to Jacquard that the credit of rendering this machine thoroughly practical is due, although it has been proved that the fundamental idea of it, which consists in substituting for the weaver’s tie-up a band of perforated paper, was first applied to the draw loom in 1725, while in 1728 a chain of cards was substituted for the paper and a perforated cylinder also added. But it was reserved for Jacquard to carry the machine to such perfection that, although many slight improvements have since been made in it, it remains to- day practically the same as he introduced it in 1801, not- withstanding the astonishing development of textile ma- chinery during the nineteenth century and the universal [ 290 } HOUSEHOLD AND FARM INVENTIONS adoption of the machine both for hand and power weaving. May I here repeat and emphasize that the invention of the Jacquard machine did not alter in the least the draw- loom method of pattern weaving? It only took the place of the drawboy and the pulley box, and substituted the endless band of perforated cards for the weaver’s tie-up. The designs, too, drafted on ruled paper, would be worked out in precisely the same manner, whether for tying up on the cords of a simple or for punching in a set of Jacquard cards. Each card, in fact, takes the place of one row of loops of the tie-up. The term Jacquard weaving, then, which one so often hears used, is a misnomer. It should be draw-loom weav- ing with a Jacquard machine, the machine being only an ingenious substitute for a less compact and manageable adjunct of the draw loom, an adjunct, moreover, which, as we have seen, has continually varied from the time of the invention of this form of loom. After the draw loom itself I should class the Jacquard machine as the most important invention in textile mechanism. It therefore claims a careful description. Figure 52 is a drawing of the front elevation of a 400 Jacquard machine. The number 400 refers to the number of needles and hooks with which the machine is fitted up. These needles and hooks answer to the number of the simple cords of the draw loom. A design is still technically spoken of as being drafted for so many cords. The position of the machine in the loom is at the top, where it is fixed on a solid frame just over the comber board, usually with its end to the front of the loom, so that the elevation shown in the figure is parallel with the side of the loom frame. The machine frame is oblong in shape. It is made of hardwood for hand looms and of iron for power looms. But in either case it needs to be of great strength. To the principal frame a smaller one is hinged at the top, so that it can be raised like a flap. In this drawing 50 wire hooks are seen standing upright [ 291 ] GREAT INVENTIONS on the bottom board of the machine. The bottom board is perforated with as many holes as there are hooks in the machine, in this case 400. The hooks represented are only one rank out of eight, which the machine contains. Each hole in the bottom board has a dent or groove cut across the top, in which the bent end of the wire hook rests. This } HHA avai Et se EH A bay i A HOH AE r i i] ail HOWE BH RUHOT | i i nog ae HI i } \ H CD \y eet RA au'n'ale } =r aaa Tien tn Fic. 52. Front elevation of a Jacquard machine. Courtesy of the Royal Society of Arts a H Wi Hue oes : : l : q l a A UHHAV ROW ROW y HAH DOU Wied wih 4 eA | eH BG AV WOH | PHVA AU QRMURH UR =| Duuy t OH ROTA WU RRMA OU AE HN A wat WAH Hl HW Wi HH WAV | HAA RAH GU if 4 \ M H nih i! AHN f Hi H Ht aut} { i i! WEG i ah 6 i} | He ea at aa va HAGE H i Han Wk H I N| i i i Hi nny i) i tl KULLU Piaihes | } UE STITT sy) i keeps the hook firmly in position, especially when the necking cords of the harness are brought up through the holes and looped on to the wire. Figure 53 gives two sections of the machine, one showing it at rest and the other showing it in action. In both sections 8 hooks are drawn, 1 from each rank of 50. The hooks have the necking cords attached at the lower ends, and just below the small hook at the top may be seen a set of eight wires crossing them at right angles. Each of [ 292 ] HOUSEHOLD AND FARM INVENTIONS these wires, called needles, is bent into a loop or eye, where it crosses one of the hooks, and it is because the hook is passed through this eye that it is retained in an upright position. Figure 54 will show this arrangement quite clearly. Each hook thus resting on the bottom board, and held down by the weight of the leashes of the harness, Se BAAS LING NW te Pye = Fic. 53. Sectional views of a Jacquard machine. Courtesy of the Royal Society of Arts though supported at the top by the eye of the needle, through which it passes, is still free to rise and raise with it the leash or leashes to which it is attached. Leaving the hooks thus standing, let us consider the arrangement for lifting them. Above the hooks the sec- tion of a solid block of heavy wood or iron is shown. This block runs from end to end of the machine, and has pro- jections at its ends which fit into the narrow spaces be- [ 293 ] GREAT INVENTIONS tween the two pairs of uprights of the machine frame in such a manner that the block can be caused to slide up and down steadily but freely. Now, let us look at the block in the drawing of the front elevation (Fig. 52) and then at a drawing showing the block in detail, separately. The lever for raising the block, being extended to a convenient length, is connected by a rope to a treadle worked by the weaver’s foot in the hand loom, or by any ordinary mechanical arrangement in the power loom. Figure 55 gives us details of the block (1) as seen in front elevation; (2) from above; and (3) from the end. Fic. 54. Detail of a Jacquard The block, the machine. Courtesy of the Royal lever, and the arrange- Society of Arts : are ments for sliding up and down are already explained. But hanging from the block is a kind of gridiron, called by the weaver a “‘griffe,”’ which requires careful notice. Near each end of the block a flat plate of iron 1s firmly fixed. The shape of the plate is shown at No. 3, and between the plates, eight bars of hoop iron are fitted, as at No. 2. These bars are placed diago- nally (see No. 3) and their top edges are sharpened so as to fit under the carefully made small hooks at the top ends of the upright wires as they stand in their several rows. The first section of Figure 53 shows the block at its lowest position, with the hooks caught on the bars of the griffe. Should the block now be raised the whole of the 400 hooks will be drawn up and the whole warp will rise with them. When released, of course, all will fall together, pulled down by the lead weights. Again, if the projecting ends of the needles are pushed inward, the needle eyes will deflect the hooks and remove them from the griffe, which [ 294 ] HOUSEHOLD AND FARM INVENTIONS will then, if the block be raised, rise by itself, leaving the hooks, leashes, and warp all down, as in section 2. In section 2 the points of the needles are seen to pass through and project beyond the surface of an accurately Fic. 55. Further details of a Jacquard machine. Courtesy of the Royal Society of Arts perforated board fixed to the front of the machine frame opposite the needles. Hung in the frame, hinged to the top of the machine, is a four-sided revolving bar, or cylin- der, each side being perforated so as to match exactly the perforations of the needle board. If the flap, with the cylinder in it, be pressed against the board, and the block raised, nothing different will happen, because the points of the needles will have been free to enter the holes in the cylinder. If, however, a card cover- ing all the holes be fixed to one side of the cylinder and the cylinder then be brought close up, presenting each side in regular succession, every time the card comes in con- tact with the needle points the needles will be pressed inward, push the hooks off the bars of the griffe, and the block will rise without them. [295 ] GREAT INVENTIONS It follows, then, that if we interpose between the needle points and the side of the cylinder, as it presses the needle board, a card perforated according to an arranged design, wherever a hole is covered by the card a needle will be pressed in, and consequently a hook will be pushed off the griffe bar and left down as the block rises. Each card, therefore, affects, in one way or another, every hook in the machine with its necking cords and leashes; and these, of course, determine the rising or remaining down of every thread of the warp from edge to edge of the web. At the back of the machine a shallow box is fitted, containing 400 small spiral springs, one for each needle. When, therefore, any needle is pressed inward by the card on the cylinder, its opposite end is forced into the spring box, but as soon as the pressure is relaxed the needle, driven back by the spring, regains its normal position, holding the hook upright. The mechanical contrivances by means of which the cylinder is moved, pressed against the needle board and rotated as the block rises and descends, are most in- genious, and subject to a great deal of variation. They are, however, not essential to the principles of the ma- chine and can be passed over. But the method by which the perforated cards are adjusted to the cylinder and interpose between it and the needle board must be explained. Figure 56 shows a detached cylinder and four cards punched with a pattern called a four-lined twill. This pattern repeats on every four lines; accordingly only four cards are needed to weave it. At the ends of the cylinder, close to the perforations, pegs are fixed and holes matching these pegs in size and position are punched in the cards. These pegs hold the card in its proper place, so that its perforations correspond exactly with those of the cylinder. Each side of the cylinder as it rotates, being covered [ 296 | HOUSEHOLD AND FARM INVENTIONS with a card held close to it by two elastic bands will press against a different set of needles at each of its four move ments. The fifth movement, of course, brings the first set of needles again into play. When, however, as is generally the case, more than four lines of design are required, the Fic. 56. Cylinder and cards for a Jacquard machine. Courtesy of the Royal Society of Arts cards have to be laced together in an endless band hung upon a rack at the side of the loom, and carried around the cylinder. The most striking advantage of the use of the Jacquard machine in the textile arts is the facility it gives for a fre- quent change of design. It is only necessary to take down [ 297 ] GREAT INVENTIONS one set of cards and hang up another in order to change the pattern. The result of this facility was that the early part of the nineteenth century witnessed a perfect orgy of fantastic ornamentation. The manufacturers of all sorts of ornamental silk and fine woolen textiles vied with each other in the number and originality of the designs they could produce. The profession of designer may almost be said to be an outcome of the invention of Jacquard. Previously to this time the master weaver, or some person in practical touch with the looms, had arranged the design, and when once tied up on the loom it was good for a lifetime. But with the introduction of the new draw engine, as the machine was called, all this was altered, and restless change of pattern and fashion was the result. Plate 94, right, shows a Jacquard loom on exhibition at the United States National Museum. At first the machine was only adopted in the silk trade for the weaving of rich brocades and other elaborate materials for dress or furniture, but ever since its intro- duction its use has been gradually extending, all kinds of plain and ornamental textiles being now made by its means, whether on hand or power looms. As a work of mechanism it is truly wonderful. It can be made to govern all the operations of the loom except throwing the shuttle and actuating the lever by which it itself works. It opens the shed for the pattern, however complicated, regulates the length of the design, changes the shuttle boxes in proper succession, rings a bell when certain points in a design requiring special treatment are reached, regulates the take-up of the woven cloth on the front roller, and works out many other details, all by means of a few holes punched in a set of cards. Its great defects are the dreadful noise it makes, the ease with which it gets out of order, and the difficulty of putting it right. These render it only suitable for factory use, where noise does not seem to matter, and where a machinist is con- stantly at hand to keep the mechanism in good order. [ 298 ] HOUSEHOLD AND FARM INVENTIONS In order to find the earliest recorded attempt to weave by power we must carry our imagination back to the latter part of the sixteenth century and look in on the fathers of the city of Danzig in council chamber solemnly assembled. They are deciding the fate of a prisoner accused and found guilty of the crime of inventing a very ingenious machine for weaving narrow tape several breadths at a time. The council, having carefully con- sidered the machine, and bearing in mind the state of the trade, were “‘afraid that by this invention a great many workmen might be reduced to beggary.” They, therefore, mercifully ordered the machine to be suppressed and the inventor of it to be privately strangled or drowned! The operations of the loom in weaving are four in number: To open the shed, to throw and catch the shuttle, to beat the weft together, and to wind up the woven cloth. All these, except the second, are comparatively easy to arrange for, even in broad weaving, by means of a power-driven turning shaft furnished with cranks and eccentrics, fitted up in some convenient position in the loom. In narrow weaving the spaces of warp are so small that the passing through of the several shuttles presents no difficulty; consequently the invention of a practical automatic machine loom for narrow weaving was an early one. Many attempts were made in the seventeenth and early part of the eighteenth century to weave broad webs by power, but they all failed to solve the problem of the shuttle. It has been partially overcome since, but the great defect of the machine loom today is in the driving and catching of the shuttle. The invention which par- tially solved the difficulty and eventually rendered the machine loom practicable was the fly shuttle, intended by John Kay, its inventor, for use on the hand loom. Its purpose was to enable the weaver to weave, without the aid of an assistant, wider webs than he could manipulate with the hand shuttle. [ 299 | GREAT INVENTIONS Previously to this invention all attempts to pass the weft through the shed in machine looms failed to achieve anything like the speed of the hand-thrown shuttle; con- sequently they could not compete with the hand loom. Even when the fly-shuttle method was adopted the difficulty of catching the shuttle baffled the skill of inventors for many years. It was not till 1786, when Dr. Edmund Cartwright devoted himself and his fortune to mechanical invention, that a practical broad-weaving power loom was evolved. Doctor Cartwright established a weaving and spinning factory at Doncaster, but after spending £30,000 and nine years in experiments he was obliged to give it up. He had, however, succeeded in devising a power loom for plain weaving, which it was believed could compete with the hand loom. Plate 97 is a room filled with modern power looms for worsted weaving at a modern textile factory. You will notice at once how the levers for driving the shuttle, and the shuttle boxes, have increased in size and strength. It was found that in order to catch the shuttle and prevent it rebounding, its entry into the opposite box had to be resisted. This rendered it necessary that the shuttle itself should be enormously increased in weight, and that great force should be used in driving it. Half the power expended in actuating the machine loom is required thus to drive the shuttle into the opposing box. The addition and adaptation of the Jacquard machine to the power loom was not attempted till late in the nineteenth century, but when that was done the loom had arrived at the point of development at which we find it today. INVENTIONS CONCERNED WITH AGRICULTURE Of the many nineteenth century inventions that reduced farm labor, including plows, harrows, manure spreaders, corn planters, grain seeders, cultivators, mowers, horse rakes, tedders, hay loaders, fruit pickers, [ 300 ] HOUSEHOLD AND FARM INVENTIONS milkers, cream separators, and many more, none were so revolutionary in their influence on the productivity of American agriculture as the cotton gin, the harvester, and the applications of mechanical power. At the close of the Revolutionary War cotton was sparsely raised in the South, but the labor of separating the fiber from the seeds was so great that flax, hemp, wool, silk, and fur were far more important sources of clothing and textiles. Radical was the change produced by Eli Whitney’s invention of the cotton gin. It is estimated that it increased the productivity of the worker a thousandfold. In open court, Federal Judge Johnson of Georgia stated its importance thus: Is there a man who hears us who has not experienced its utility? The whole interior of the Southern States was languishing and its inhabitants emigrating for want of some object to engage their atten- tion and employ their industry, when the invention of this machine at once opened views to them which set the whole country in active motion . . . Our debts have been paid off, our capitals have increased, and our lands trebled themselves in value. We cannot express the weight of the obligation which the country owes to this invention. Eli Whitney (1765-1825) was a native of Westborough, Mass. After graduating from Yale he became a private teacher in Georgia, in the family of Gen. Nathaniel Greene, of Revolutionary fame. His ingenuity attracted the attention of Mrs. Greene, and she directed his thought to the problem of separating the cotton seeds. A neighbor, Phineas Miller, also from New England and a graduate of Yale, became interested, and entered into a partnership with Whitney to promote the j invention. The experiments were carried on in Miller’s house. Whitney had only the most primitive implements, but in the course of the winter of 1793 he advanced so far as to be assured of success. Generally a great invention has to create its market by laborious promotion of its advantages. In this case the result was quite the reverse. When it became known that Whitney was making a machine to gin cotton, crowds threw fairness to the winds, broke into the work- [ 301 ] GREAT INVENTIONS room, and carried the machine away. Before patent proceedings could be completed by the partners, dozens of pirate cotton gins had been put to use in the cotton fields. The simplicity of Whitney’s cotton gin worked against the recovery by the partners of fair compensation for their efforts. In principle it comprises merely a cylinder armed with numerous fine-toothed circular saws operating through slots leading into a box of seed cotton. The saw teeth catch and draw away the fibers, but the seeds are excluded by the sides of the narrow slots. A second, more rapidly rotating cylinder armed with brushes removes the cotton lint from the saw teeth. Figure 57 gives a cross-section of a gin showing one of the saws and accessories. Many suits were instituted by Whitney and Miller to protect their rights under the patents, but they were often unsuccessful. It is said that juries were more alive to local interests than to doing justice to the inventor and his partner, natives of distant States. A fire destroyed Whitney’s factory in New Haven, with all his gins and papers. In 1803 Phineas Miller died without ever having received adequate compensation for his share in the intro- duction of the invaluable cotton gin. Whitney succeeded in persuading the legislatures of South Carolina, North Carolina, and Tennessee to appropriate some money in payment for rights to use the cotton gin within those States. But he never received from his invention any adequate return. He amassed a competency later by manufacturing arms for the Government. He died at the age of 60, seven years after his very happy marriage. Several of the features of the successful reapers of McCormick and of Hussey were included in partially successful British inventions of Joseph Mann, 1820; Henry Ogle, 1822; and Patrick Bell, 1826. Mann, like McCormick, had the main traction wheel directly behind the horse. Ogle had the vibrating cutter-bar, the reel, the platform, and the divider to separate the swath from the [ 302 ] PLATE 98 Eli Whitney, inventor of the cotton gin grgi ‘Avy oR N ‘Aueqry ,,fowanyng syy,, wong “Sgr jo sodvar yorws0joyy “BUNSIAIBLY JO 9POUL UOWIUO9 IY} I9AO osuadxe Jo || aalwaaya AiaA & ST UW “patsy uaeq sey yr WoYyM Aq sou) Sutavs jeaiS & 1e pur ‘Aep & ut ulei3 jo saaoe Apuam) 01 JO Se]PoOj4v0 snOdownNuU ay} WOd odpnf Avul am Jt pur U2aYY WO INO O} PAUBNeM St auryoeL 9) 1eY] Uaas || ‘uoLUA ey] JO saywIg Surmors ureas ay1 jo jsoul ut pasn oq I[[M jf “toquinu sty] ul puNnoy aq 0} ‘juaWastjJeape |] Ajaaisuajxe Ueeq sey jy “wIulsarq ‘“—————— Jo ‘wow SOMA “Ap 07 aouosajor AG “qusuratdwe siqunyea pur |] -xog.w “H '9 Aq “CPST ul pajueazed seas aur yoru SILT, “UGdVdaH S.HOINUOO.WN ae SPST ag LINGLVd ~~ _ mS SN ANA \ \\ $,AOWWIIOD IW We xs alts rTM [91 YOLVAILTOO FHL ‘OP8T 66 ALV Id HOUSEHOLD AND FARM INVENTIONS uncut grain. Bell also had the reel and the divider, and he foreshadowed a feature of the modern harvester, for he had an endless canvas belt to remove the cut grain from the platform, depositing it in an orderly row along the ground. Waa Ss é l, S APs V Fic. 57. Cross sectional diagram of a cotton gin. Courtesy of John Wiley & Sons, Inc., publishers The McCormick reaper, patented by Cyrus Hall McCormick in 1834, was first used in substantially that form in the harvest of 1831 at several farms in Walnut Grove, Rockbridge County, in the Valley of Virginia. [303 ] GREAT INVENTIONS Prior to that, Robert McCormick, father of Cyrus, had made several partially successful reapers. He had a blacksmith shop and tools for working both wood and iron. The successful reaper was made by the hands of the two McCormicks, father and son. Figure 58 shows a restoration of it, as indicated by the patent of 1834. The traction wheel is directly behind the horse, and the grain is cut at the side, so as to avoid trampling. A Fig. 58. Restoration of McCormick reaper, 1834. Drawing from patent specifications of C. H. McCormick, omitting the pusher device vibrating cutter-bar with plain or serrated cutting edge lies horizontally a few inches above the ground. A series of curved fingers at intervals along the blade hold the stalks of grain for the sawing action of the vibrating knife. A reel of four slats, revolving above the cutter-bar, bends the grain toward it to promote cutting, particularly in case the grain is “lodged,” or the wind blowing it forward so that it is not vertical. Behind the cutter-bar is a plat- form on which the cut grain falls parallel to the horse. A man, walking behind, periodically rakes the grain off the platform in bundles, called gavels, for binding. On the [ 304 ] Auedurod TOJSIAIC LY [BeuOTRUIIIUT eur jo Asa3.ino7) “TIJSIOAIBY ULIPO TA] SRO EN 001 ALVId Aurdwio sasaaivyy [euonvusszuy aya Jo Asaqyinoy *AOYSATYI-J9ySoAIVY BULIBOC]-YIWIOJ IIA TOL ALVW Tc HOUSEHOLD AND FARM INVENTIONS outer end of the platform is a divider with pointed front to separate the grain to be cut from the grain standing beyond. In the year 1833 Obed Hussey, in Ohio, invented and constructed a reaper which he patented in December, 1833, a little before the McCormick patent was issued. His machine was carried like a modern mowing machine on two equal traction wheels, with a vibrating cutter-bar at the side. On a platform behind the cutter-bar rode a man with a rake, whose duty it was to bend the standing grain toward the cutter, and push it off the platform to the ground when cut. The Hussey cutter-bar was his principal improvement. Like a modern mowing machine, it had a series of adjacent triangular knives, sliding be- tween the sides of divided pointed fingers. But instead of a single bevel, his knives were beveled both from below and from above. This feature Hussey later changed to the single bevel sliding closely upon the lower finger plate. In 1847 he improved the lower finger plate by a slot to clear it of chaff and leaves, so that he then reached prac- tically the standard cutter-bar construction of modern mowing and reaping machines. Keen competition quickly arose between McCormick and Hussey. Both made many improvements in their ma- chines as time passed. During the years 1839 to 1847 the Hussey machine was manufactured in Baltimore, and the McCormick at Walnut Grove, Va., by Robert McCormick. After 1845 Cyrus McCormick employed also certain other manufacturers. However, only a few hundred reapers had gone into use. In 1844 and 1845 Cyrus McCormick traveled through the Middle West to introduce his machine, and he aroused considerable interest among farmers there. Robert McCormick, the father, dying in 1846, and relations with the several manufacturers em- ployed not being altogether satisfactory, in 1848 Cyrus McCormick established a factory in Chicago under the partnership McCormick, Ogden, and Jones. In 1849, [ 305 | GREAT INVENTIONS Ogden and Jones retired, and the firm name became McCormick & Company. Leander and William McCor- mick, younger brothers, joined in the enterprise. Cyrus was a very able and enterprising business man, and pushed the sales greatly. Leander was in charge of the manufac- turing end of the business, and William attended to the financial end. Thousands of the improved McCormick reapers were made and sold, so that Cyrus McCormick be- came a millionaire, and honors were heaped upon him. In 1878 he was even elected a corresponding member of the French Academy, cited as “having done more for the cause of agriculture than any living man.” Between 1848 and 1860 he entered into a number of law suits against competitors, but not always successfully, and he failed in his attempt to have his original patent ex- tended. Nevertheless his enterprising business methods and the excellence of the McCormick machine, led to this enormous success. The advantage of reapers was demon- strated to be so tremendous for the harvesting of wheat and other grains, that not only the McCormick but the Hussey, Mann, and other reapers were sold in thousands. As already stated, in the early machines of McCormick and Hussey, the grain, as it was being cut, fell upon a platform a little behind the traction wheel, and a man walking behind the platform, or in later constructions riding near the platform, raked the grain intermittently in a direction parallel to the cutter-bar, so that it fell on the ground in orderly heaps called gavels, ready for bind- ing. Plate 99, from a McCormick circular of 1845, shows the raker in his seat. From time to time there were in- vented various self-rakes, operated by the traction wheel, to do this work instead of the man, but even as late as 1855 the McCormick reaper held its own against the self- rake reapers. But in 1858, C. W. and W. W. Marsh, of Illinois, patented a device wherein the platform became an end- less belt. It had also a continuation in an elevating belt [ 306 ] ainjpNUsy jo Jusuniedagq sajiwig paiuy sy} Jo Asaqinog ‘samod Aq Suruapsey - ~ - 1 = SATE Bg gt PS ee 7% a Se ES . Ay, Se Seth gee atin vs, we oa FED "oat cOl ALW Id dIN}[NILIBY JO qusujsedaq S9}BIS podtuy) 93 jo Asa}ino7 “TOJIVIY Uudey FUL os og CCL REE Sy £01 ALVId HOUSEHOLD AND FARM INVENTIONS like the side of a letter A, which carried the grain up over the traction wheel and deposited it in a receiving box ready for binding by two men who rode on the machine. From the Marsh harvester has been perfected the modern self-binding harvester. Various automatic binding devices using wire, twine, or straw were invented soon after, but the modern form de- veloped from the cord binder of John P. Appleby, per- fected about 1876, which combined the good points of preceding devices, and especially the knotter of Jacob Behel patented February, 1864. The automatic binder merely takes the place of the two men who rode on the side of the Marsh harvester, but it is of such complication that one can hardly understand a description without seeing the machine itself in opera- tion. Plate 100 gives a view of the modern self-binding harvester. Various slightly differing machines, all with their good points, are manufactured by different com- panies. It would be difficult to exaggerate the importance of the harvester for the food supply of the world. In the last few decades the harvester-thresher machines have to a considerable extent superseded the self-binding harvester. Plate 101 shows how the grain is gathered and threshed by such machines in those areas where the conditions are favorable for allowing the grain heads to dry on the stalks. In other less favorable regions the so- called windrow harvester is used to cut off the grain tops, leaving them in windrows to dry several days. Then the harvester-thresher, with pick-up attachment, goes over the field and threshes the grain without the necessity of handling it. According to the American Thresherman it appears that in 1929 about 65,000 self-binding harvesters and about 37,000 harvester-threshers were built by all makers. The former machines had a factory value of about $10,600,000, the latter of $50,600,000. The increase of grain acreage in the United States in 1921-1930 over that of 1902-1905 was more than 20,000,000 acres. [ 307 | GREAT INVENTIONS The enormous increase in the population of the civilized countries of the world in the nineteenth and twentieth centuries is in great measure due to the discovery of bacteriology by Pasteur and the modern improvements in sanitation, in preventive and curative medicine, and in allied sciences. It has thrown a very great burden on agriculture, which could hardly be carried without the long list of modern labor-saving machines, some of which are enumerated above. These machines require much power, which until about 40 years ago was supplied ex- clusively by animals, mainly horses and mules. These animals consume much food but are not usually con- sidered available for human food, as were the slow oxen that preceded them. Therefore it has been of marked relief to the demands upon agriculture for food produc- tion that machine traction is largely superseding animal traction in all lines, from transportation to power driving of agricultural machinery. Besides this, the greater speed resulting from mechanically powered operations has led to increased productiveness of farm labor. Four types of power auxiliaries to farming stand out. Most important of all are automobiles and trucks, for providing rapid transportation and for marketing prod- uce of all sorts. Second comes the multitude of indi- vidually motored tools and appliances for gardening, cul- tivating, dairying, water hoisting, and small power re- quirements of many kinds. The automobile and the small power unit are of use to every farm, large or small. Third, there are the powerful wheeled tractors, used on large farms to drag gang plows, harrows, cultivators, and har- vestors where large, fairly level acreage is in cultivation. Finally, there is the caterpillar tractor which can go any- where and pull anything. This was made familiar by its introduction in the World War as the motive power of the tanks. Plates 102 to 104 illustrate three of the applica- tions of mechanical power to agricultural uses such as we have considered. [ 308 | aunjqNosy Jo quaujsedaq SI}BAS poytuy) 3y} jo Asaqinos “YIOM Ye IOJIVAR Jeypidsayes I4UL aie vOl ALVId CHAPTER OUTSTANDING MANUFACTURED PRODUCTS In earlier chapters we have been dealing mainly with machines. Let us now consider four typical products of a manufacturing age, constantly produced in immense quantities—paper, rubber, glass, and steel. From its slow hand-production, sheet by sheet, for writing purposes, a thousand years ago, paper has come to be manufactured by the millions of tons. Not only rags, grasses, and straw, but the forests of whole countries are used for its raw material. From its early function of pro- viding the sheets on which the quill pen laboriously wrote, it has come to supply the material for the armies of clicking typewriters and the inconceivably intricate, rushing presses which flood the world with letters, records, adver- tisements, newspapers, books, and periodicals. In the form of newspapers and wrappings, paper enough to cover Ohio three times over is used every year in the United States. Boxes made of paper fill the shelves of groceries and stores of all descriptions and have displaced wooden boxes for shipping goods. Picnic parties strew their paper dishes and paper napkins from Maine to California. Exhibition buildings, statues, car wheels, dolls and play- things of many kinds have been made from paper, and even nature’s flowers are imitated in paper in all but their fragrance. More than 60 years ago James Parton! made out an impressive list of articles which the world then enjoyed as the fruit of the life-long inventive sacrifice of Charles Goodyear to the cause of India rubber. Mentioning things 1 Famous Americans of recent times. Ticknor and Fields, Boston, 1867. [ 309 ] GREAT INVENTIONS as various as machine belting, valve packing, and artificial teeth supports, he recalls to his readers through their recollections of the sufferings of the then recent Civil War, the following enumeration of the blessings of rubber. Some of our readers have been out on the picket-line during the war. They know what it is to stand motionless in a wet and miry rifle-pit, in the chilling rain of a Southern winter’s night. Protected by India-rubber boots, blanket, and cap, the picket-man performs in comparative comfort a duty which, without that protection, would make him a cowering and shivering wretch, and plant in his bones a latent rheumatism to be the torment of his old age. Goodyear’s India-rubber enables him to come in from his pit as dry as he was when he went into it, and he comes in to lie down with an India-rubber blanket between him and the damp earth. If he is wounded, it is an India-rubber stretcher, or an ambulance provided with India-rubber springs, that gives him least pain on his way to the hospital, where, if his wound is serious, a water-bed of India-rubber gives ease to his mangled frame, and enables him to endure the wearing tedium of an unchanged posture. Bandages and supporters of India-rubber avail him much when first he begins to hobble about his ward. A piece of India-rubber at the end of his crutch lessens the jar and the noise of his motions, and a cushion of India-rubber is comfortable to his armpit. The springs which close the hospital door, the bands which exclude the drafts from doors and windows, his pocket-comb and cup and thimble, are of the same material. From jars hermetically closed with India-rubber he receives the fresh fruit that is so exquisitely delicious to a fevered mouth. The instrument-case of his surgeon and the store-room of his matron contain many articles whose utility is increased by the use of it, and some that could be made of nothing else. His shirts and sheets pass through an India-rubber clothes- wringer, which saves the strength of the washerwoman and the fibre of the fabric. When the government presents him with an artificial leg, a thick heel and elastic sole of India-rubber give him comfort every time he puts it to the ground. An India-rubber pipe with an inserted bowl of clay, a billiard-table provided with India-rubber cushions and balls, can solace his long convalescence. To all these uses for rubber, how many more could be added today! The dental and hospital uses; the chemists’ and photographers’ tubes and trays; the Mhalloone that soar for science in peace and for information of enemy dispositions in war; the insulation of countless miles of [310] OUTSTANDING MANUFACTURED PRODUCTS wire in cables and in electrical appliances; its employment to give resiliency to golf balls, tennis balls, and baseballs, and to contain air in footballs; the uses of hard rubber, called ebonite, for elegant finish or electrical insulation; the use of great quantities of rubber in floor and roof coverings; the millions of miles of rubber hose; and besides a thou- sand cther uses too many to enumerate, the manufacture of tons and tons of rubber into the tires of the automobiles not even dreamed of by Goodyear or Parton. Of glass there is scarcely any need to recall its value. How few of my readers past middle life could dispense with reading lenses! Yet prior to A.p. 1300 it is doubtful if the failing vision of any one in the world’s history was ever aided by glasses. Very early, it is true, in China, Egypt, Rome, Greece, and the ancient world generally, glass was known and used for decorative purposes. Long before it was an aid to vision, the beautiful glasses of cathedral windows bore testimony to the skill of the crafts- men and the esthetic culture of the artist. Not until modern times, however, could the ordinary man afford to use glass for welcoming the sunlight and repulsing the wind and cold in his dwellings. Nothing of its use for optical instruments in the forms of lenses, prisms, and mirrors was known until about the year 1600. In our day glass is everywhere. Homes are lighted by its use; the factories have scarcely any other walls; the chemist has his tubes and retorts; billions of electric lights shine through it; bottles by the trillions bring pure materials, germless preparations, and preserved foods to the plainest of homes; electricity is carried safely in millions of miles of wire through the use of glass insulators, and the scientist with his optical instruments searches every problem from those of the heavens to those of the atoms by the aid of glass. If glass requires little to recall its value, steel is uni- versally known to be indispensable. All the machines which are described in these pages are largely built of [331] GREAT INVENTIONS steel, and the machines by which they are made and as- sembled are made of steel and used along with tools of steel. Weapons of war and instruments for the crafts of peace alike are fashioned of steel. Steel locomotives run on endless tracks of steel and draw their long trains loaded with structural steel, out of which are fashioned those towering buildings that make up a skyline like New York’s. PAPER Discovered at least two centuries before Christ by the Chinese, the secret of the manufacture of paper reached western Asia about the eighth century a.p. Though paper manuscripts have been found in Egypt dating from about A.D. 1075, western Europe saw the first manufacturing of paper about the middle of the twelfth century under the auspices of the Moorish conquerors in Spain. Then, and for more than six centuries afterward, paper was made by hand, sheet by sheet. Some of the choicest paper both from Oriental and Western sources is still hand-made. ‘The first machines for paper making were invented in 1798 by Louis Robert, an employee of the Essonne Paper Mills in France, but have been improved by many inventors in Europe and America toward their present degree of perfection. The machine process follows closely the hand method, except that it proceeds continuously by the aid of carriers and rolls so as to manufacture paper in endless lengths of fixed width instead of single sheets. The earlier steps in paper making are intended merely to clean and bleach the materials, to remove all substances other than plant fiber, and to reduce the remaining fibers to short lengths, finely divided and held in suspension as a smooth watery pulp free from lumps. These steps are accomplished first by beating the rags employed (if a rag stock is being made), sucking away the dust, and reducing them to small-sized pieces. Then, whether rags, esparto, or straw, the stock is boiled in alkaline solution under steam 2124 Auvduwioy sadeg puv ding viursit, 3S 44 9Y3 JO Asa}Inod «“Suryeu soded Joy souryseyy we wees ase £ eee s oe ae ; col ALVId Auvdwoy sadeg pue ding viuidit, 4s2A44 243 Jo Asazinog = ‘ssao0id Suryew-saded ay3 jo Surpue ay f, SELES i 901 ALV Id OUTSTANDING MANUFACTURED PRODUCTS pressure for hours. After being washed, the mass is reduced to pulp by a revolving drum armed with many knives and working close to a set of parallel steel bars. When the fibers are thoroughly teased apart in this way the pulp is bleached with chlorine compound and after being washed is ready for paper making proper. A very large quantity of paper is made partly or wholly of wood pulp. Fir, spruce, poplar, and aspen from Scandinavia and Canada are the principal staple woods for paper making. The logs are furnished in 4-foot lengths; the bark and knots are first removed, and then the logs are cut into tiny chips by a power cutter. These chips are bruised between iron rolls and screened to remove dust, after which they are boiled for hours, either in caustic soda or sulphurous acid under 6 to Io atmospheres steam pressure. After being bleached, the wood pulp is washed and is then ready for paper making. The pulp, whether of rags, straw, or wood, is not yet fine and smooth enough for matting on the wire cloth. It goes to a beating engine or refiner, one type of which consists of a hollow conical cylinder armed within with steel bars and containing a rotary grooved conical grinder which can be adjusted to fit closer and closer within the enclosing conical sheath. As the pulp is forced into this machine while the grinder revolves at high speed in close proximity to the steel bars, the pulp is reduced to a fine, even suspension. Paper, however, unless it be blotting paper or coarse wrapping paper, requires more or less of resin, glue, or other kind of sizing to prevent the ink from sinking i in and spreading. Such materials, and sometimes china-clay, are next added as required, together with any dyes which may be desired for color. In the old days of hand paper making a sufficient quantity of the prepared pulp would be dipped from the vat to make a sheet of paper of the thickness desired and spread evenly on a fine wire sieve. To keep the charge in place on the sieve, a frame of wood called the deckle [313] GREAT INVENTIONS was laid over it. To form the water mark, certain designs would be woven so as to be raised slightly above the general surface of the wire cloth. When the screen was lifted from the vat, the water would run away leaving the fibers matted down on the wire. The deckle was then removed and the screen turned over upon a flat sheet of felt, to which the paper pulp adhered so that the screen could be removed. After a number of sheets of pulp were piled up alternately with felts, the whole pile was strongly compressed to squeeze out the water. The felts could then be removed and the paper sheets could be more strongly pressed, dried, and sized. The machine process is based on the hand method. From the vat the pulp runs through tortuous channels armed with baffles to catch the lumps, and thence onto a table to distribute it evenly. Thence it flows onto an endless wire-cloth belt carried forward by rollers and fenced on either side by rubber deckle strips. Suction is applied at the farther end of the wire cloth belt to dry the pulp, and there, too, the water mark is impressed from above by the “dandy-roll.”” Then come the couch rolls covered with felt, which compress the pulp enough so that it can leave the wire cloth. And now the paper goes on, being dried and compressed by felt-covered rolis heated by steam from within, the heat being applied sometimes by rollers above, sometimes from below. While still a little moist, the paper passes between polished iron rolls to smooth it and give it surface. It is thus calendered between as many sets of rolls as necessary to suit the purpose intended, and then wound upon a roll. For certain grades of paper intended for writing or illus- trating, the necessary sizing to keep the ink from spreading may be applied after the paper is formed by leading it from the dryers through a vat of hot gelatin solution with a little alum, after which it is calendered between hot rolls. Plates 105 and 106 show paper making. In Plate 105 the pulp tanks and forming wire screen are shown in [314] OUTSTANDING MANUFACTURED PRODUCTS the foreground, and the drying rolls beyond. In Plate 106 we see the end of the process and the paper wound on the enormous roll ready for use. Heavily glazed paper for half-tone illustrations must be made very smooth and even in surface. This is accom- plished on coated paper by heavy pressure and friction between polished rolls. In the machine called the super- calender the rolls are alternately of chilled iron and compressed cotton or paper, and they drive at unequal rates so as to produce friction to smooth the surfaces. Paper deteriorates at very different rates according to its composition, chemical treatment, and texture. Stand- ards of quality are now set up and enforced by Govern- ment departments in order to assure sufficient permanence to important documents. Money and bonds are printed only on paper made of the most durable materials and containing certain inconspicuous identifying threads very difficult to imitate. About one twentieth of the cut timber of the world is now used for paper, besides all the rags, straw, esparto, and other substances available. The United States manu- factures and uses more than half of the world’s paper production. In 1927 the production in the United States exceeded 10,000,000 tons. RuBBER India rubber, like Indian corn, potatoes, and tobacco, was a New World discovery, though it is now made also from several Old World trees and vines. Its common compound name betokens its earliest use by the South American Indians, and also its earliest use in civilized lands to erase lead pencil marks. Several families of trees and vines furnish the milky latex which yields rubber, but the best of these sources is the Hevea brasiliensis, a tree which grows naturally in Brazil to a height of nearly 100 feet and a diameter of 3 or 4 feet. From the latex of this tree, a fluid somewhat like that of the milkweed or [315] GREAT INVENTIONS the dandelion, comes Para rubber. Much first-quality Para rubber is collected by the native Indians according to their traditional methods, but plantations of Hevea brasiliensis have been set out in Africa, the Malay Penin- sula, and other tropical regions, which now furnish almost all of the world’s rubber. The latex holds the rubber particles in suspension as the cream is held in cow’s milk. By cutting in the bark a long vertical Y-groove almost through to the wood of the tree and joining to it herringbone patterns of short inclined V-grooves about 12 inches apart, the latex is caused to run down into a cup at the bottom of the tree. Preferably only the lower 6 feet of the tree is thus tapped, and a herringbone pattern usually occupies only one fourth of the circumference of a young plantation tree. Nearly every day a fine shaving is cut from the lower side of the herringbone grooves to keep the flow running. After about a year of continued slicing, all the bark between the slots is removed. One-fourth of the tree being thus stripped of bark, the opposite quadrant is employed for the next year. After this another quadrant is used and finally the fourth. But in the four years that have elasped new bark has grown on the original area, and the process can then be repeated. The average yield of rubber from 10-year-old trees is about 2 pounds per tree per year. Plate 107 shows a native engaged in tapping. Various methods are used to extract rubber from the latex. Some varieties need only centrifuging, the method by which cream is extracted from milk. Others yield to heat and time. In most plantations acetic acid is used to promote the separation. Natives in some countries use the juice of certain astringent vines to coagulate the latex. The natives of South America heat and smoke the latex on a stick, the hot astringent smoke drying out and coagu- lating the latex into rubber. Each day’s collection is added to the stick and gets its smoking in turn, until a [ 316] OUTSTANDING MANUFACTURED PRODUCTS large lump of rubber has been made. In the plantations the rubber, after being washed, is squeezed dry between rolls, and before shipment it is further dried by hanging it in dark sheds, or by vacuum driers. Rubber can also be made by the chemist from the products of coal tar by a combination technically called polymerization of the molecules of several terpenes, especially isoprene. This is a substance composed of eight atoms of hydrogen and five atoms of carbon per molecule. Rubber, however, is much more complex, for its molecules each contain probably eight or ten molecules of isoprene. Although the synthetic production of rubber from isoprene was accomplished more than 25 years ago, it is not profitable as compared to collecting rubber, either from the wild trees of South America and Africa, or from the rubber plantations now abundant in many parts of the tropical world. During the World War Germany was forced by the blockade to the synthetic production of rubber and manufactured several thousand tons of it. Botanical sources are now relied on altogether, however, even in Germany. Rubber was used to some extent to shed water more than a century ago. The name Mackintosh for a rubber coat comes from the use of rubber sheets by one Mack- intosh, about 1820, for producing waterproof fabrics. To prevent stickiness, he placed his rubber sheet between two thin layers of cloth. No general use of rubber in the modern way was possible until the discovery of vul- canization by Goodyear in 1839, for whatever was made of natural rubber in winter melted under the warmth of summer. Charles Goodyear and his family were martyrs to rubber. Born in 1800, Goodyear learned about 1833 of the failure of a prosperous company which had been organized shortly before in Roxbury, Mass., to exploit a supposed valuable method of curing rubber for use in shoes and coats. Millions had been spent by that com- [317] GREAT INVENTIONS pany, but the summer heat had ruined the shoes and gar- ments sold, and the company itself, the stock of which had at first a spectacular rise, had totally failed. From 1833 until his death in 1860 Charles Goodyear thought of nothing but rubber, experimented on rubber, borrowed and begged for rubber, wearied his friends by his talk of rubber, wore rubber, went to prison for debts many times on account of rubber, pawned his wife’s clothes for rubber, sold his childrens’s school books for rubber, nearly starved for rubber, allowed a child to die for rubber, crossed the ocean for rubber, engaged in lawsuits for rubber, and in a word lived for rubber. Without Charles Goodyear’s sacrifice for rubber it is improbable that the world would ever have used it. The process of vulcanization by admixture with sulphur is not likely to have ever been discovered had Goodyear not stumbled upon it and spent his life in bringing it to perfection. Yet though he gave the world this great boon, he died penniless, leaving no provision for his family. It was in 1836 that Goodyear got the first inkling of the value of sulphur in curing rubber, when he observed superficial vulcanization of rubber by the action of sulphuric acid. He at first believed then that he had the full secret, and began to do a prosperous business in shoes and coats. The process was indeed successful for very thin goods, but his success was turned into costly failure when 150 mail bags, made for a government order, melted down in the heat of autumn. His acid curing was merely superficial. From a man in his employ he next bought a patent method for combining sulphur with rub- ber in sunshine, which again he thought to be the secret, but which proved of little use. It was by a lucky accident that in 1839 he laid a rubber sheet partially cured with sulphur against a red hot stove. Certain areas of the sheet were converted into hard rubber which we now call vulcanite, and certain other areas were cured into a rubber more elastic than the [ 318 ] PLATE 107 rubber tree ga Native tappin PLATE 108 Charles Goodyear OUTSTANDING MANUFACTURED PRODUCTS crude product, free from stickiness under all temperatures below boiling, and impervious to acids and oils. But many obstacles yet remained before full success came. To perfect processes for the satisfactory vulcanization of rubber surely and evenly, Goodyear reduced himself and his family to penury in the following years. Not until 1844, after the expenditure of many thousands of dollars by his brother-in-law, William De Forest, who at last came to Goodyear’s assistance, was the process of vulcanization finally made uniformly successful. So poor a business man was Goodyear that he sold the right to make rubber shoes for a royalty of only one-half cent a pair. But the licensees under his patent expended, it is said, $25,000 to retain Daniel Webster in its defense, against Rufus Choate, counsel for the infringers, in the famous suit Goodyear v. Day which was decided for the Goodyear patents in 1852. Even after this success, Good- year was imprisoned several times for debt in America and France, and he died in 1860 a poor man. Nearly 700,000 tons of crude rubber are now manu- factured annually, of which less than 50,000 tons comes from wild sources, the remainder being from plantations, chiefly in Malaysia. A large amount of reclaimed rubber is also used. Most of this latter material is prepared by the process of A. H. Marks, patented in 1889, whereby the scrap is ground up and heated for 12 hours or more to about 350° F., with dilute caustic soda. This, of course, takes away all cloth or vegetable fiber used in previous manufactures. Large quantities of reclaimed rubber are used with crude rubber. Various substances are com- pounded therewith in order to produce resistance to wear, acids, steam, or oils. In addition, the flowers of sulphur are added to produce vulcanization. Most goods require from 3 to § per cent of sulphur, but hard rubber contains from 10 to $0 per cent. Compounded rubber becomes soft and pliable by repeated rolling between cool rolls. Great care must be used in thoroughly mixing and blending the [319] GREAT INVENTIONS compositions. This is done by rolls cooled by water, lest the intense heat of friction vulcanize the mixture. Plastic rubber can be rolled by calender rolls into smooth sheet form, and a very great deal of rubber manu- facture involves this step. Rubber bands, for instance, are made by first cementing up rubber tubes from sheets and then cutting off narrow sections of the tubes. Cloth is used alternately with rubber to prevent the rubber sheets from adhering to each other. Frequently two- and three-ply goods are made in this way. Calendered products may be of uneven thickness. Tire treads and footwear, as well as ordinary rubber cloth, are calendered. Soft rubber may be squeezed into the meshes of cloth by calender rolls. Often thin sheet rubber is caused to ad- here as a coating to a background of cloth into which rubber has thus been forced. Plastic rubber may be extruded under great pressure from dies of proper forms to make seamless tubes and lengthy articles of many sorts. Inner tubes for tires, tire treads, hose pipe, strap rubber, and a great variety of other shapes may be made in this way. Molds are also much used, many of them having the makers’ names, numbers, lettering, or other designations incised therein so as to print the rubber with raised symbols. The curing of plastic rubber containing the requisite sulphur is done by heating either with steam or hot water, or dry heat, according to conditions. Molded articles are stacked in hydraulic presses and cured with hot steam from one to eight hours, according to the mass of rubber contained. Hollow articles, including bulbs, tennis balls, and many other forms, are forced into their molds by inside pressure of steam and thus vulcanized. Rubber shoes on perforated lasts are forced against their molds by steam pressure. Garden hose is cured by steam from without, which sends its heat through a temporary lead sheath, and at the same time by hot water under pressure from within. [ 320 ] OUTSTANDING MANUFACTURED PRODUCTS The addition of flowers of sulphur and the application of heat are not the only means of curing rubber. Surgeons’ gloves, finger cots, and many other thin articles are made on forms dipped in a cement made from crude rubber without foreign admixtures. They are vulcanized in the cold after the evaporation of the solvent, by leaving them for a sufficient time in vapor of sulphur monochlo- ride. Plate 10g shows rubber gloves being made by dipping. This process of vulcanizing by sulphur mono- chloride was invented in 1846 by Alexander Parker, of Birmingham, England. Another method of vulcanization, suitable for thin goods, was devised by S. J. Peachy, of London. He employed sulphur dioxide gas, following that treatment after some time by hydrogen sulphide gas. In recent years the advantage has been recognized of manufacturing certain goods directly from latex, instead of from rubber. But two-thirds of the latex being water, the cost of transportation of the fluid from the Tropics to the factories would be a serious drawback. Various means of concentration are employed, such as filtration, evapora- tion, and centrifuging. The vulcanization of latex may be accomplished by stir- ring powdered sulphur into the fluid and heating the mix- ture to 140° C. Also the mere evaporation of latex to dry- ness gives a strong film of vulcanized rubber, providing a very simple method of making rubber cloth. Metal as well as cloth may thus be coated firmly with rubber, and latex may even be deposited electrically on metal somewhat as silver is plated on baser metals. Many kinds of hollow rubber goods as well as rubber-plated goods are deposited electrically, the electrical action depending on the fact that the latex particles are negatively charged and there- fore migrate to the positive pole when electric tension is applied. Latex-made goods are stronger than those made from rubber. The magnitude of present-day rubber manufacture is very great. In 1925 the United States produced about [ 320 | GREAT INVENTIONS ,000,000 pairs of rubber boots and 53,000,000 pairs of rubber shoes and overshoes, besides rubber-soled tennis shoes and rubber heels well up in the millions. The rubber industry is one of the largest in the United States. It exceeded 134 billions of dollars in 1925 and was rapidly growing. GLass At least 1,400 years before Christ the Egyptians prac- ticed decorative artistry in glass. They did not, it 1s true, use the blowpipe, with which such intensely interesting feats are now accomplished, but they wound their rods and threads of glass about sand molds and welded them into vessels and ornaments. Their colorless glass con- tained approximately, according to the analysis of Neu- mann, silica 64 per cent, lime 8, magnesia 4, soda 23, with traces of potash, alumina, and iron. Already they were familiar with the coloring of glass by the use of oxides of copper, iron, and manganese. Their craft was so well de- veloped that we must suppose it had its beginnings much earlier. By 1200 B.c. the Egyptians used molds and made pressed glassware. In the luxurious times of the Roman rule of the world, glass artistry was in great demand. Specimens of the work of about the beginning of the Christian era have come down to us which can hardly be surpassed in beauty. Among them is the celebrated Portland vase in the Gold Room of the British Museum, a blue body covered with opal glass, decorated with beautiful figures in relief. Venetian glass of the thirteenth to the eighteenth cen- turies is justly famed for its wonderful embodiments of skill in form and embellishment by patterns of lace, filigree, and enamel. Saxony and Bohemia became famed centers of art glasswork about the sixteenth century, and remain so to this day. Their use of potash rather than soda helped to give luster to their work. The introduction of lead oxide in English glass in the seventeenth century [ 322 ] Suiddip Aq spew saaoja Joqqny 60T ALV Id OUTSTANDING MANUFACTURED PRODUCTS gave a highly lustrous surface that enhancea the beauty of English crystal. The basis of glass is quartz sand, known to chemists as silica, or the oxide of silicon. In pyrex, that notably heat- resisting glass invented in America at the Corning Glass Works, it runs to nearly 81 per cent. Other common glasses have less silica, 60 per cent or less in some cases. In cer- tain special optical glasses there is a much smaller pro- portion of silica, even as little as 20 per cent in very dense flint, which has 80 per cent of lead oxide. The two com- mon alkalies soda and potassa, the oxides of sodium and potassium, make up in combination from Io to 25 per cent of most glasses. In the ancient glasses, soda was used almost exclusively, and it still occupies the more prominent place as the alkali in glassmaking. But for certain optical glasses and for lustrous ware, potassa is preferred. Next in importance are the oxides of calcium and barium, alkaline earth metals. Calcium oxide, well known as lime, is by far the more common of the two in glass, but barium gives a higher elasticity and toughness and besides 1s largely used in optical glasses to give cer- tain desired refractive values. Lead oxide increases the luster, and 1s much used in fine table ware and cut glass. It also is of great value for optical glasses of certain types. Alumina, and zinc and magnesium oxides are also used for imparting certain desired properties. Boric acid, from which comes sodium borate, commonly known as borax, is used for certain optical glasses and to increase the tough- ness of glasses subject to sudden changes of temperature, such as lamp chimneys and thermometers. Though not particularly objectionable for bottle and window glass, the 4éte noire of fine glassmaking is iron oxide, which is invariably found in the sand and also in the clay used for the melting pots. Iron oxide imparts a green color to the glass and diminishes its transparency, as may be seen by looking edgewise through a sheet of win- dow glass. Accordingly, the world has been searched for [323] GREAT INVENTIONS sands and clays as free from iron oxide as possible. The best European sand is that of Fontainebleau in France, but during the World War a search for American sand suitable for optical glass led to the discovery of a sand at Rockwood, Mich., even freer from iron than that of Fontainebleau. The effect of contamination of the melt by iron in the pots may be reduced by glazing the inside of the pots at a very high temperature before using them for the melt. It has been the practice for many centuries in fine artistic glassmaking to cover up the green color due to iron impurity by imparting certain nearly com- plementary colors. For this purpose small quantities of the oxides of magnesium, selenium, nickel, and cobalt are sometimes used as decolorizing agents. They can not cover the effects of large quantities of iron, and they do not, of course, prevent the loss of transparency but rather augment it. Sulphur, which often enters with the potassa, is another troublesome impurity in fine glasses. It tends to cloud the glass and diminish transparency. On the other hand it is intentionally introduced in the amber glasses used for decorative purposes. The various constituents required to produce a certain desired quality of glass are thoroughly mixed together in a powdered dry condition before melting. In making opti- cal glass, during melting and until the glass nearly solidi- fies, the mass is stirred by infusable rods in order to keep a uniform mixture and to eliminate bubbles from the melt. Glass may be regarded as a solid solution. That is to say, there is not an inseparable chemical union of the con- stituents in definite proportions such, for instance, as in the union of sodium and chlorine i common salt, but rather a mere mixture of constituents as of alcohol with water. The constituents tend to separate, owing to their unequal specific gravities. Some glasses also tend to crystallize at about the solidifying temperature, which would destroy not only their transparency but the finished [ 324 | OUTSTANDING MANUFACTURED PRODUCTS smoothness of their surfaces and make them more apt to dissolve into contained liquids. Pots used for melting glass are built up by the ancient art of the potter from fire clay. It takes a great while to prepare a pot. After the bottom is made, only a part of the sides can be built up at first. Time must be allowed for partial stiffening before further building, which requires several operations with drying periods between. When finally complete, the pot must rest about two months to become thoroughly dried out and seasoned before firing. The heat must be applied gradually, so that the firing of a pot occupies some two weeks. Glass in pots or tanks is usually melted by so-called “producer gas,” prepared at the works by incomplete combustion of soft coal in a closed furnace. This gas includes some carbon dioxide and much nitrogen as neutral diluents. Its heating properties depend mainly on carbon monoxide and hydrogen, which together may make up about one third of the mixed gases given off. Some- times this mixture is enriched by the addition of ‘“‘water gas,” made by blowing air and steam through hot coal or coke. Such a gas may consist of over go per cent hydrogen and carbon monoxide contained in about equal propor- tions. In modern warfare both naval and land artillery are required to make hits on targets 10 or 15 miles away which are invisible to the gunner. Others must observe by accurate methods and apprise him of the required pointing. This involves range finders, telescopes, field glasses and many optical devices of high accuracy. Prior to the World War, the United States had imported from Europe almost all the optical glass manufactured here. When war was declared by the United States in the spring of 1917, very few pounds of optical glass were in the country, there were facilities available for production of only perhaps 2,000 pounds a month, and a demand for 2,000 pounds a day was looming up. [325] GREAT INVENTIONS In these anxious circumstances the matter of producing optical glass was placed in the care of Dr. Arthur L. Day and his associates of the Geophysical Laboratory of the Carnegie Institution of Washington. All the staff and facilities of that laboratory were placed by the trustees of the Carnegie Institution at the disposal of our Government for the duration of the war. Associated with them were members of the staff of the United States Bureau of Standards. What happened may best be described by quotations from an account by Doctor Day entitled “Optical Glass and its Future as an American Industry,” presented at a joint meeting of physicists and chemists with the Ameri- can Chemical Society, March 25, 1920, and printed in the Journal of the Franklin Institute for October, 1920. . . . In 1912 the Bausch & Lomb Company, who were the largest manufacturers of instruments of precision in the United States, de- termined to control their own glass supply, and with the aid of a Belgian expert began making optical glass in their plant at Rochester. A factory fire soon afterward consumed the building and some delay occurred, but in 1914 very creditable samples of optical glass were produced in this plant. Because of the demands of the great war this industry flourished and the initial small pot furnace was soon replaced by other larger ones, and at the period when this record begins (March, 1917) this company was engaged upon large contracts for field glasses for the Canadian Government and for the British Field Service, in which the glass used was in part, at least, of American manufacture. The total output of this plant which might be con- sidered available for American use at this critical moment was perhaps as much as 2000 pounds per month, a quantity sufficient in their expert hands for a considerable number of optical instruments. At the time when our situation was most critical (March, 1917) the experimental work of the Bureau of Standards had not proceeded far enough to be of great assistance. Their experimental work with pots was not finished and only one type of optical glass (a borosilicate crown) had been successfully made. During this period also, and more or less in collaboration with the Bureau of Standards, Mr. Carl Keuffel, of the firm of Keuffel & Esser, had erected at the works of his company in Hoboken a small furnace [ 326 ] OUTSTANDING MANUFACTURED PRODUCTS in which also a successful attempt had been made to produce this type of glass, using pots of his own design and manufacture. In the year 1916 the Spencer Lens Company, of Buffalo, erected a small plant at Hamburg, N. Y., and also began the manufacture of optical glass with a view to replace the foreign sources of supply already closed by the war. The capacity of the plant, as operated during the late months of 1916 and early 1917, was not above 200 pounds per month, and actual production was considerably less than this, being uncertain both in quantity and quality. The chemist of the Hazel-Atlas Company, Washington, Pa., Mr. Duval, who was also reputed to have been a successful maker of optical glass in Europe in earlier years, had already set up an ex- temporized furnace in this country and had melted a single pot of glass of such quality as to win favorable consideration from a firm as exacting in its requirements as the John A. Brashear Company, of Pittsburgh. It also appeared that in 1915 the Pittsburgh Plate Glass Company, at its plant in Charleroi, Pa., had begun making considerable quantities of spectacle glass and other high grade special glasses not particularly intended for optical instruments, but nevertheless of excellent com- mercial quality. Incidentally, this plant proved to be the largest in the United States which might be deemed immediately available for the production of optical glass, and if it should be possible to improve the quality up to the standards of the army and navy, might contribute much to relieve the immediate need. . . . It appeared clear that all of the sources of optical glass avail- able in May, 1917, could together produce only about half of the quantity required, assuming that all of the glass produced was of quality suitable for war equipment. At that time the Bausch & Lomb Company [where several of the Geophysical staff were engaged] alone were producing glass of such quality. Moreover, it was estimated that they might, by extending their plant, carry approximately one- half of the war load. To maintain the other half there appeared to be but a single course open, namely, in some manner to make the Charleroi plant of the Pittsburgh Plate Glass Company available and to place someone in charge of it who should have sufficient knowledge of the requirements and technique to raise the quality of glass produced there to the standard which the Government required and which they had not hitherto attained alone. In practice there was some disappointment in carrying out this plan. At the close of the year 1917 the Bausch & Lomb Company was producing in Rochester at the rate of about 40,000 pounds per month, while the Pittsburgh Plate Glass Company had not been able [327] GREAT INVENTIONS in the eight months interval to provide any glass which would pass the Government inspection standards. At that time Mr. Raymond, General Manager of the Pittsburgh Company, decided that the basis upon which they were producing was not destined to prove successful, and application was made to the Geophysical Laboratory to divide its force at Rochester and to permit a number of the chemists who had been successful there to take up the Pittsburgh problem. This was practically laying the entire load upon the Geophysical Laboratory, because only one month previous (December 4, 1917) the Laboratory had taken the responsibility for production in the third of the optical plants, that of the Spencer Lens Company, of Buffalo, and every man of its force was occupied to the limit of his capacity. ... . . . Sixteen furnaces were available which had already been used for glassmaking, and others which might be turned to the task should circumstances require, but all of the furnaces were of an old type without regeneration and without means for controlling the tem- perature in individual furnaces within 100 degrees centigrade, whereas it was already established by our experience at Rochester that a control as close as 5 degrees must be continuously maintained in each individual furnace to insure success. The Pittsburgh Company was liberal in its plans and the Govern- ment placed a large contract, amounting to 100,000 pounds, with the company in order to afford an incentive to press forward as rapidly as possible the improvements which were needed. Certain specified improvements were even authorized to be charged against cost of the glass delivered. Nevertheless production lagged, and it was not until the following July that the output contemplated in the original plan was attained. In the intervening months the average production had been from 3000 to 6000 pounds per month, which afforded a modest contribution in addition to the production elsewhere, but it amounted to scarcely 10 per cent of the production of the Rochester plant through- out the spring months. Ordinary spectacle glass in its conventional use appears clear and white, but if it is held so as to permit looking through the glass edgewise considerable color may usually be detected, so that it might occur to one as doubtful whether it would be possible to see clearly through the same glass if the thickness were represented by the width of the glasses rather than by their shortest dimension. For optical purposes, notably in the case of prisms used in range finders and periscopes, very much greater thicknesses than this are common, and a glass for such a purpose must be optically perfect throughout its thickness, which may often reach four or five inches. [ 328 | OUTSTANDING MANUFACTURED PRODUCTS The qualities assigned for test in establishing standards of inspec- tion for optical glass, very briefly, are these: (1) Homogeneity, by which is meant uniformity in chemical com- position, freedom from striation, bubbles, inclusions and crystallization. (2) A constant refractive index and a constant dispersion ratio throughout. (3) Freedom from color. (4) High transparency. (5) Both physical and chemical stability, by which is meant dura- bility under exposure to the weather, chemical fumes, etc., as well as toughness and hardness for protection against misuse. (6) Physical homogeneity, by which is meant freedom from strains or internal stresses caused by uneven cooling of the molten glass. To produce glasses with these qualities the first obvious requirement is high chemical purity in all the ingredients of the glass itself and the second either an insoluble pot in which to melt it, or one in which the ingredients entering the glass from the pot shall not impair the development of the above qualities. The search for such materials, which was immediately instituted by the Geophysical Laboratory when it was first authorized to take up the optical glass problem, yielded the following results: mi After a search of the sand quarries from the State of Washington to Florida, including more than forty-five different localities, a sand was finally located at Rockwood, Mich., of which the analysis indicated greater purity than that from any known source of supply, even in- cluding in the comparison the wonderful sand of Fontainebleau (France) which has been used both in France and England for artistic glassware for a hundred years. A number of sources of potash were canvassed, in the course of which much disappointment was experienced. Not only were the efforts, which were first put forth in this country to make potassium carbonate, less successful than might be wished, but the cost of manufacture was almost prohibitive. European potash was laid down in New York before the war at six cents per pound, while the major portion of the American-made potassium carbonate used in the manufacture of optical glass cost the Government in the neighborhood of $1.00 per pound. This fact is of some importance as an indication of the outlook in store for an independent optical glass industry in this country now that the war has closed. It is to the credit of the Armour Company, of Chicago, that the first potassium carbonate of adequate purity was produced in this country. Subsequently it was found possible to substitute the nitrate for the carbonate, either in part or altogether, and so to obtain a salt which was equally good and much more generally available. But [ 329 ] Les GREAT INVENTIONS even so, the necessary provision for potash in some of the glasses remained to haunt us throughout our entire experience of glass manu- facture without reaching an altogether satisfactory final solution. Sulphur and chlorine, one or both, were very often found, and a small percentage of either is usually sufficient to give a milky cast to the finished product. In view of the long period of time needed (about four months) to manufacture, to dry, and to burn the pots which must contain the glass during melting, to which allusion has been made above, this investigation also was never quite satisfactorily concluded. In the beginning it was of course necessary to purchase in the open market such pots as were then available. These had not been made with a view to their use in the manufacture of glass of high purity, and in general were found to contain about one hundred times as much iron per cubic centimeter as could safely be permitted in the finished glass (2.0 per cent., compared with 0.02 per cent.).... Nevertheless our pot makers, with a single exception, put forth a splendid effort to meet the situation by conducting experiments simultaneously in several plants, and it proved possible within four or five months to obtain containers in which the raw material was sufficiently free from contaminating elements so that glasses of a purity comparable with the best European glasses could be obtained. This conclusion was aided considerably by the discovery that if the pot was first burned in a furnace at a temperature considerably higher than any which would be required for melting the glass, burned even until the side walls showed signs of sagging and the surface became more or less glazed, then the solution of pot material in the glass was very greatly diminished... . . . . It should be borne in mind that a glass solution is never in equilibrium, but is constantly changing in composition. Lead oxide and the alkalies are somewhat volatile, while the containing vessel continually contributes alumina, silica, and usually iron. It is there- fore necessary for the student of glass melting who wishes above everything to attain to a prescribed chemical composition, to establish precise data upon the rate of evaporation at particular temperatures of those ingredients which pass out of the furnace and, at least approxi- mately, the rate of solution of the pot in the glass. Knowing these quantities and the time of exposure necessary to mature a glass which is free from stones (that is, completely dissolved) and free from tiny bubbles, of which there is constant danger with every shift in the temperature, it is possible to produce successful pots of glass of accu- rately uniform composition and so to define and to reproduce definite optical constants. The general relation between composition and optical constants [ 330 ] OUTSTANDING MANUFACTURED PRODUCTS is obviously the main issue in optical glass manufacture, and is there- fore very conspicuous by its almost complete absence from the litera- ture of the subject. Much of the optical glass technique has been enveloped in profound secrecy in all the three countries where it has been mainly produced, and although more or less freedom has been permitted in the publication of technical details of temperature, of stirring, and even of chemical composition, the manner of varying optical constants in any desired way through changes in composition has remained a trade secret up to the present time. In this connection it is perhaps interesting to remark parenthetically that at the time when the French Liaison Commission visited this country after our entry into the war, to aid us with their experience in the production of war material, it was not permitted to divulge any details regarding the manufacture of optical glass upon the ground that the integrity of the existing glass monopoly in France had always been respected by the Government and must be so still, in spite of the war pressure. ... It became necessary therefore to proceed much as a scientific man is accustomed to proceed in other unknown fields, by varying quanti- tatively each ingredient present and plotting the results in curves through which the effect of each ingredient on the optical constants of the resulting glass might be determined. This was done system- atically and very successfully, so that within a period of three months from the beginning of our efforts it became possible for Dr. Fred E. Wright, who was in charge of the work at Rochester, to write formulae for any of the typical glasses required for war service without advice from the glass expert employed there, and indeed to prepare new glasses directly from the optical specifications when needed. A special heavy flint, for example, which was desired by the Government, was made with no more than two trials. To properly appreciate just what this progress means, it may perhaps be recalled that in the days of rule-of-thumb glassmaking, as many as I50 essays were necessary before a glass of predetermined optical constants resulted. This kind of knowledge applied intelligently commanded for the Laboratory workers the immediate respect and confidence of the workmen who had hitherto believed these things to be shrouded in impenetrable mystery, and contributed in no small degree to the rapid progress and whole-hearted cooperation obtained. . - - Most of the optical glasses in general use fall into two types, generally designated as flint and crown, both of which when melted form viscous mixtures which give little difficulty except in maintaining homogeneity. The barium crowns and flints, on the other hand, appear almost as thin as water in comparison and possess the dis- advantage that they are taken up by the pots almost as rapidly as [331] GREAT INVENTIONS coffee is taken up by a lump of sugar. The most serious question encountered in connection with the barium glasses therefore was not to discover the composition appropriate to the prescribed optical constants, but to provide a suitable container in which the ingredients could be melted. [See in Plate 110 the improved resistance offered by Fulcher’s new product against solvent action in the glass furnace.] There is one other problem to which allusion should be made which is on the whole the most persistent and difficult problem encountered in the entire glass technique; it is the question of obtaining a homo- geneous product. By this the glassmaker understands primarily freedom from striations or cords. It is fairly obvious that in a mixture, parts of which are volatile and into which other ingredients are entering through the solution of the containing vessel, inhomogeneity is con- stantly to be feared. Moreover, in the heavier glasses the differences of specific gravity among the ingredients amount to as much as three or four to one. These are the causes of the glassmaker’s cords and striations, of which traces are found in the finest product of the glass- maker’s art. It is to meet this situation that stirring is resorted to at several stages of the process. Theoretically, if the stirring were vigorous enough, homogeneity would result except for the losses due to evaporation and the accessions (chiefly of alumina) from the pot wall; practically, this result is not so simply attained. Practically, indeed, perfect homogeneity in glass melts is unobtainable. Alumina in particular, even when present in very small quantity, yields a glass of lower refractive index than the surrounding mass and becomes immediately conspicuous. Incomplete solution of silica grains will sometimes leave a train through the mixture resembling a comet’s tail. Such striations are very persistent and require stirring, either constantly or at frequent intervals, not only during melting but during the cooling, in order to diminish, so far as possible, the convection currents or other migration within the melt. Even with all the precautions taken which the experience at the several factories suggested to us, rejections by Government officials were mainly on account of striations. Toward the close of the war a new scheme of melting was developed, partly in the hope of providing a quicker process than the normal one and partly in order to render the striations innocuous by orienting them perpendicular to the plane of light transmission. . . . It also proved practical to carry out the entire melting process within a period of 24 hours. Where before the war two weeks was not an uncommon period through which to nurse the melting operation in order to secure the best results, a 24-hour schedule was worked out by Doctor Morey at the Spencer Lens Company’s plant under which [332] OUTSTANDING MANUFACTURED PRODUCTS glass equal in quality to any which was supplied to the Government during the war period was produced. I venture to remark that before the beginning of this experience at the Bausch & Lomb plant no member of the group of men who under- took the war work there had ever followed a pot of glass through the process of melting. Moreover, with the long record of secrecy continuously maintained in two of the glass-producing countries, and in the third also, except for a portion of its early history, no informa- tion was available from without. Here asin many other cases, however, when the details are finally brought to light by time, the maintenance of secrecy has frequently been shown to be a cloak to cover limitations rather than profound knowledge. The processes of glassmaking are simple and the traditions of the glass-house are as often the result of cumulative superstition as experience. The heart of the whole matter lies in the relations between the ingredients at the various tempera- tures through which they pass and their reaction velocities. The solution of these relations is not a task for the glass-house, but rather for the most exacting application of silicate chemistry at high tem- peratures. The Geophysical Laboratory has published freely the results of its experience in the glass industry, and in so far as this experience was not available before, it is now for any individual or group who may wish to make a beginning of a permanent optical glass industry in this country. It remains true to-day, as it did during the war period, that the cost of several of the necessary ingredients is necessarily greater in this country than in European countries where similar products originate. In quality our raw materials are equally good, our experi- ence in technique is adequate if not equally extensive with some of our European contemporaries, but the cost of potash, for example, will always lay a burden upon the American product, and other in- gredients might be mentioned which fall in the same category. If there were a market sufficient to stimulate production on a very large scale these difficulties could be overcome by improved technique and organization, as in the case of other conspicuous American industries, but the demand for optical glass will probably never be large, and the incentive to large-scale processes and cheaper production will therefore probably always be lacking unless the Government determines upon a definite program of preparedness. The instrument maker may find it advantageous to make his own glass for the reason that he can then arrange for the precise optical constants which he wishes to use in his instrument, and he may have them within a period of a few days [333 | GREAT INVENTIONS instead of weeks or months, but the trade itself will perhaps never furnish sufficient incentive to build up a large industry in this country. The total quantity of glass supplied by various firms from April 6, 1917, to November 11, 1918, the war period, is approximately 650,000 pounds,? divided as follows: Bausch & Lomb Optical Company... .450,000 pounds, approximately Spencer Lens, Company oa: cejacks rie 75,000 pounds, approximately Pittsburgh Plate Glass Company...... 125,000 pounds, approximately In addition to this production the Bureau of Standards supplied a little more than 19,000 pounds. Except for occasional shipments of a few pounds from the Parra Mantois Company, in France; from the British Government plant at Derby, and that produced by the Keuffel & Esser Company, of New York for their own contracts (about 9,000 pounds for the period of the war), no other optical glass was available to the Government for war operations. The varieties of glass are so different that the manu- facture of the various types may almost be regarded as separate industries. To illustrate: there is transparent sheet glass for windows, cases, and mirrors; colored sheet glass for artistic decoration of cathedral windows and elsewhere, in which transparency is secondary to color effects; cheap hollow ware, such as bottles, used mainly for containing and keeping free from contamination fluids, medicines, and other substances; fine quality decorated hollow ware, such as goblets, pitchers, wine glasses, and shades; electric light bulbs; pressed and molded glass, including electrical insulators, trays, tum- blers, decorative articles, etc.; chemical glass, including tubing, beakers, and flasks; and finally optical glass, the highest product of the glassmaker’s art. The greatest contribution of America to glassmaking has been in the invention and development of automatic machines for drawing sheet glass, plate glass grinding, tube drawing, bulb making, and other processes. Several of the foremost American glass companies have already 2Informal records of the Geophysical Laboratory. [ 334] SIO M SSP) SUIUIOZD eyy jo Asaqinoy yes dovVUINg eur jo JO}UID eyy Adno20 SYOOTG IP ][MU ySVIOIZI9][9 JOYI[NY IY, “YOHSe sse]s JOY Suipuvjsyjyim UL SALIOJIVIJOI UIIMJIq SOOUIIOHIC Y Oll ALV Id OUTSTANDING MANUFACTURED PRODUCTS been mentioned in Doctor Day’s account. Another of the progressive glass producers in the United States is the Corning Glass Works, which owns plants at Corning, N. Y., Wellsboro, Pa., Kingsport, Tenn., and Central Falls, R. I. This company was formed in 1868 and early appreciated the advantage of scientific research. It has been a leader in introducing scientific and automatic methods of production. Among its best known products is pyrex, a high-melting-point glass of such composition as to give it a very small coefficient of temperature expansion. Accordingly it is much used, not only in the household, but also especially for laboratory purposes. In conclusion, let us consider one of the most remarkable of automatic glass machines. Plate 111 illustrates the Corning bulb machine, designed by David E. Gray, chief engineer of the Corning Glass Works. It is the culmina- tion of a series of more and more automatic glass-blowing machines made by this company to produce incandescent electric light bulbs. This single machine, which is fully automatic, can turn out accurate bulbs at the rate of 400,000 per day. An excellent description of it by F. W. Preston may be found in the journal, The Glass Industry, for August, 1931. A glass fairly high in alumina is melted in a tank of special form with a capacity of 40 to 50 tons per day. The bulb machine, which is provided with a wheel base, is run up under the forehearth of the tank, where it remains from two to three days before being withdrawn for reconditioning. When the machine is in place, a steady stream of molten glass falls between a pair ot rollers which make of it a ribbon loaded at intervals of 3.9 inches with glowing red buttons of glass, each of which is just large enough to become a lamp bulb. A conveyor of steel plates corresponding in position to the glass buttons, each plate perforated in its center, carries the glass ribbon with its load of buttons along. Every button falls centrally over the hole in its steel [335] GREAT INVENTIONS plate, and begins to sag through it. But within one or two seconds a second conveyor drops onto each glass button, as it comes opposite, a blow head for forming the bulb. The blow heads are all under air pressure of about two thirds of an atmosphere, and they quickly blow the buttons into elongated test-tube-like sacks, still red hot. Next there shuts upon each glass sack a mold form made in two halves exactly the shape of the bulb to be. These molds are carried by a conveyor, more complicated than those above mentioned, with devices which not only shut and open the molds but also rotate them while in place so that no mark such as may often be seen on a molded bottle will be left on the bulbs. When in place, a second part of each blow head delivers within each bulb a pressure of one tenth of an atmosphere, which forces the bulbs to shape. Now the shaped bulbs are in free air, still hot, but connected to the glass ribbon which has been drawing them along. But as the bulbs arrive at a certain place, a flap of metal, which oscillates synchronously with their arrival, gives just the proper knock to separate each bulb from its place on the ribbon, and the bulbs drop onto a belt which lands them successively in an annealing machine whereby any strains in their texture are to be relieved. Each bulb drops, neck first, between two narrow steel ribbons on edge, of which one goes faster than the other, thus causing the bulb to rotate as it moves forward. Flames play upon the neck of the bulb to soften it enough to remove the strains, and_ finally the bulbs drop on a belt which carries them by easy stages to room temperature. STEEL There is so little difference between some forms of commercial iron and steel that iron and steel men have found it hard to define. Doctor Sauveur, professor of [ 336 | OUTSTANDING MANUFACTURED PRODUCTS metallurgy at Harvard University, points out that ingot iron should not contain more than 0.03 per cent carbon, nor more than 0.05 per cent manganese, while the mildest steel contains not less than 0.05 per cent carbon and usually not less than 0.15 per cent manganese, so that chemically and physically, as well as historically by method of production, steel can readily be differentiated from iron. From the mildest steel of 0.05 per cent carbon the steels advance in hardness to some very high carbon steels of 1.7 per cent carbon. Above this limit we find cast iron, and iron pigs cast directly from the blast furnace, with carbon contents rising from 1.7 to 5.0 per cent. The iron ore from which steel is made may have various chemical compositions, but by far the richest American ore is red hematite from the Lake Superior region, whence comes over 80 per cent of the iron ore mined in the United States, and 40 per cent of that produced in the whole world. The National Geographic Society has informed us how near the United States came to losing the Lake Superior iron ore. At the time the treaty of Paris was drawn, closing the Revolutionary War, Dr. Benjamin Franklin was par- ticularly interested in copper because of his electrical experiments. He had heard that copper had been found on Isle Royal on the northwest shore of Lake Superior; hence he insisted on including that island within our boundary. Thus it came about that not only Isle Royal but also the Mesabi iron field became a part of the United States. Mesabi ore is largely red hematite, the oxide of iron whose chemical symbol is Fe,.O3._ The molecules of hema- tite each have two atoms of iron and three of oxygen. If pure, this ore would contain 70 per cent of metallic iron. Alabama ore is also red hematite but has a larger admix- ture of lime. Although on this account it is a lower grade ore than Mesabi, its contained lime is useful for flux in the [337] GREAT INVENTIONS reduction processes and takes the place of lime which otherwise would have to be added, so that Alabama ore is also of high value. In ancient days rich iron ore mixed with charcoal was heated in holes in the ground on the sides of hills where the prevailing winds produced a blast of air. In this way small pasty masses of iron mixed with slag resulted, which were worked with the hammer into wrought iron. The reaction consisted merely in the removal of the oxygen from the iron oxide by the hot carbon of the charcoal to produce either carbonic acid gas (COz2) or the poisonous gas, carbon monoxide (CO), or a mixture of both. Most of the slag was left in the resulting wrought iron. The wrought iron of the present day also contains much slag. Modern methods are much the same in principle, but aim to purify the iron more completely, and to give definite proportions of alloying elements such as carbon and manganese in order to fit the product for its intended uses. Charcoal has ceased to be a very important reducing agent, its place having been taken by coke which is made by the distillation of coal. Formerly beehive coke ovens were exclusively used, and no care was taken to save any of the volatile products of coal distillation, but since 1920 most of the coke has been made in by-product ovens, from which the volatile products are saved. From Pennsyl- vania coal, a by-product oven yields about 75 per cent coke. A considerable proportion of the disengaged gas is used as fuel to furnish the heat required for the distilla- tion. The residue of the volatile products saved are found to contain the following substances in approxi- mately this proportion: (1) coal tar, 10 gallons; (2) sul- phate of ammonia, 25 pounds; (3) surplus combustible gas, 6,500 cubic feet; (4) refined benzol products, 234 gallons. In recent years about 50,000,000 tons of coke have been produced annually for iron and steel production in the United States. Both iron ore and coke contain impurities, including [ 338 | SYIOAA SSU[ Surusod ay3 Jo Asajyunog -*Aep sod sqjnq coofcot sMolg ‘auTyovUT ging 3YHI] yUsdsapuvoUT m5 pes saa TR RSD GILSON EE ema a earner ee | aaieenenell Se oe es Wt ALVId cll ALV Td OUTSTANDING MANUFACTURED PRODUCTS silica, phosphorus, sulphur, and others, which must be separated. It is found that most of them, if combined with lime, become readily fusible and will float as a layer of liquid slag on the surface of the melted iron. To ac- complish this result, a certain weight of lime as great as, or greater than, the weight of coke is added to the charge of ore. A fourth reagent is air, which must be supplied in greater weight than all the rest of the charge combined. The production of a ton of iron in the blast furnace re- quires fully 4 tons of heated air. The main function of the STLMAN Spat: RAW MATERIALS i) 5000 10000 15000 | GASES 13211 PRODUCT =] PIG IRON 2240 = 25] SLAG 1120 Fic. 59. Raw materials and products of the blast furnace. From Prof. H. M. Boylston’s “Metallurgy of Iron and Steel.” By permission of the author and John Wiley & Sons, Inc., publishers air is to support the partial combustion of the coke to carbon monoxide and thereby to sustain the high tem- perature required. The diagram, Figure $9, gives a fair idea of what goes into the blast furnace and what comes out to produce a ton of pig iron. The reduction of the iron ore is effected in part directly by hot coke itself, which takes oxygen from the iron oxide and thereby burns to carbonic acid gas or to carbon mon- [ 339 | GREAT INVENTIONS oxide. A considerable part of the work is done, however, by carbon monoxide produced by partial combustion of the coke in the air blast, which, taking oxygen from the iron oxide, burns to carbonic acid gas. Some of the car- bon monoxide escapes conversion to carbonic acid gas in these furnace reactions and formerly was lost into the atmosphere. In modern blast furnaces, however, the hot gases from the furnace top are saved and pumped back to the ground level, helping to warm the entering air as they pass. After being cleaned of dust and washed, they are burned as fuel to help make power for running the air pumps and also as fuel for the stoves which heat the enter- ing air stream. Figure 60 shows the construction and the reactions of a blast fur- Erica nace. The bottom and her sides are lined with re- fractory fire brick as free dem as possible from trouble- ios aes some impurities. A cen- tury ago, when furnaces were small, it was cus- Dissociation Sener tomary to feed them by hand from the top with naeur ore, coke, and lime, but 2C0= COr¢C the modern furnace stands nearly 100 feet high, and in making 500 Reduction of [ees restioee | to "700 tons: of pig iton eee me un) daily, nearly “2,00; tons \ —DMolten sl: . sii ey ee of solid matter must be } — Molten iron fed in each day. Hence, Fic. 60. Diagram of shape and mechanical conveyors chemistry of the blast furnace. have been devised which From Prof. H. M. Boylston’s tare the place of hand- “Metallurgy of Iron and Steel.” ee a: By permission of the author and WOT or this purpose. John Wiley & Sons, Inc, Furnace lids of dome publishers shape have also been [ 340 ] OUTSTANDING MANUFACTURED PRODUCTS introduced to prevent the loss of the hot gases. These lids have to be lifted to allow the solid charge to be admitted, and are made in pairs on the vestibule principle in order to reduce the loss of gas during the feeding operation. It was found that a uniform distribution of the different-sized lumps making up the charge was necessary to avoid unequal heating around the stack. Hence the feeding mechanism has been so devised as to distribute the charge evenly. Plate 112 gives a view of a portion of a blast furnace plant. The nearer furnace, although half obscured by conveyors, feed mechanism, etc., shows some of the features described above. When the liquid slag floating on the molten iron has risen to a certain level above the hearth, it is drawn through the vent prepared for that purpose. About once in five hours the molten iron is tapped off by drilling out its vent hole and allowed to stream out into the pig molds. These may be made in the sand floor or they may be iron molds carried on an endless conveyor belt and presented one after another under the flowing stream of iron. The molds pass through water to solidify the pigs, which fall from the molds at the proper place into the cars provided to take them away. In many cases the molten iron is run into a large vat or mixer, from which it goes directly into the steel-making operations. Almost 60 per cent of the blast-furnace iron made in the United States is used directly to make steel in this way, and is never cast as pig iron at all. The chemical composition of pig iron varies greatly, but on the average it may be considered as containing about 92 to 9§ per cent iron, 3 to § per cent carbon, and other constituents which may vary as indicated below: Silicon, Sulphur, | Phosphorus, | Manganese, Designation | per cent per cent per cent per cent No. 1 Foundry | 2.5 to 3.0 | under 0.035 | 0.5 to 1.0 under 1.0 Bessemer 1.0 to 2.0 | under 0.050 | under o.1 under 1.0 Basic Bessemer | under 1.0 | under 0.050 | 2.0 to 3.0 1.0 to 2.0 [ 341 | GREAT INVENTIONS The total United States output of pig iron, either as cast pig or used directly for steel production, has in recent years been of the order of 50,000,000 tons a year. Excessive percentage of carbon in pig iron is the principal thing to be corrected in converting it to steel. From 0.05 to 0.10 per cent carbon in wire and wire nails, steel ranges to from 1.§ to 1.7 per cent carbon in such very hard tools as files and metal-saw blades. Silicon up to I or 2 per cent is not prejudicial in steels, and manganese up to I or 2 per cent is advantageous, because it tends to prevent the formation of iron oxide, and also because it keeps the sulphur in a harmless state as manganese sulphide. Phosphorus and sulphur are the injurious impurities, and in good steel neither is allowed to exceed 0.1 per cent. Excessive sulphur makes steel brittle at high temperatures, and excessive phosphorus makes it brittle at low temperatures. The two principal steel-making processes are that of Sir Henry Bessemer and the open-hearth process of Sir William Siemens. The Bessemer process prevailed in the United States from about 1865 until about 1g10, when the open-hearth process took the lead; the latter now exceeds its rival in productivity more than five to one. The Bessemer process, in an imperfect state, was first developed by William Kelly, an American, who secured patents in 1857. Sir Henry Bessemer independently developed the method a little later than Kelly and carried it to much greater success. Their conflicting legal interests were eventually compromised, and Kelly dropped out of the development. The process consists primarily in forcing cold air through melted pig iron. The consequence is that the carbon is almost completely burned to carbonic acid gas and escapes with the blast. The reader may think that the process might be stopped at such a stage as to leave the desired proportion of carbon, but it proceeds very fast and is usually carried beyond this point to its finish, when the melt is recarburized to the desired [342] uonviodi07 ]293S SIJEYS poestuy) ey} jo Asaq.no7 “UOT}OR ul JI9JIQSAUOS TIWISSI V 444 He + ae Se ,* * = te « > ms a, = a a . * - - « “ > Bae sa eee 2. fll ALV Id PLATE 114 Vertical section of Wellman producer gas plant. Courtesy of the Wellman Engineering Company OUTSTANDING MANUFACTURED PRODUCTS percentage. Two principal difficulties were encountered by Sir Henry Bessemer. At high temperatures the steel was apt to be found brittle. This defect was cured by adding manganese, which through its superior attraction for oxygen overcame the tendency to produce iron oxide in the melt and also, by producing manganese sulphide, rendered the sulphur innocuous. He also found it impossible to produce good steel from pig iron high in phosphorus, limiting the pig iron suitable for the Bessemer process to that containing not more than o.1 per cent phosphorus. Figure 61 is a diagram of a Bessemer converter. Itisa Gen WF Y SQ SSK S SS G7; Zi = cd lid led bid bd a <3 = f , aa, Z IN : ro y Ses WZ Fic. 61. Diagram of the Bessemer converter. From Prof. H. M. Boylston’s “‘Metallurgy of Iron and Steel.” By permission of the author and John Wiley & Sons, Inc., publishers [ 343 | GREAT INVENTIONS pear-shaped vessel lined with blocks of ganister, a highly refractory quartzite rock, and supported on two trunnions so that it may be rotated to pour at the proper time. Air is forced through one trunnion and enters the melted pig iron through numerous apertures at the bottom. Immediately it begins to oxidize the silica and manganese, producing a dull-red smoky flame, which lasts about 4 minutes. The silica acts, indeed, as the fuel for raising the temperature of the melt to the point where the carbon begins to burn. As the carbon starts to oxidize, the flame turns yellow and lengthens, with tongues reaching up 30 feet or more. The melt boils, and the slag containing the oxidized silica is thrown off in showers of glowing sparks. When the carbon is almost all consumed the flame sud- denly drops. The operator then cuts off the air blast and turns the converter on its side. Long experience 1s needed to decide just the proper moment for ending the blow. The following graphic description is by the late Secretary S. P. Langley, from his book, “The New Astronomy.” The “converter” is an enormous iron pot, lined with firebrick, and capable of holding thirty or forty thousand pounds of melted metal; and it is swung on trunnions, so that it can be raised by an engine to a vertical position, or lowered by machinery so as to pour its con- tents out into a caldron. First the empty converter is inclined, and fifteen thousand pounds of fluid iron streams down into the mouth from an adjacent furnace where it has been melted. Then the engine lifts the converter into an erect position, while an air-blast from a blowing-engine is forced in at the bottom and through the liquid iron, which has combined with it nearly half a ton of silicon and carbon,—materials which, with the oxygen of the blast, create a heat which leaves that of the already molten iron far behind. After some time the converter is tipped forward, and fifteen hundred pounds more of melted iron is added to that already in it. What the tempera- ture of this last is, may be judged from the fact that though ordinary melted iron is dazzlingly bright, the melted metal in the converter is so much brighter still, that the entering stream is dark brown by comparison, presenting a contrast like that of chocolate poured into a white cup. The contents are now no longer iron, but liquid steel, ready for pouring into the caldron; and, looking from the front down into the inclined vessel, we see the almost blindingly bright interior [ 344 | OUTSTANDING MANUFACTURED PRODUCTS dripping with the drainage of the metal running down its side, so that the circular mouth, which is twenty-four inches in diameter, presents the effect of a disk of molten metal. . . . The “pour” is preceded by a shower of sparks, consisting of little particles of molten steel which are projected fully a hundred feet in the direction of the open mouth of the converter. Plate 113 shows a Bessemer converter in action. Not only have the silicon, carbon, and manganese been oxidized in the first part of the process, but considerable oxidation of the iron itself has taken place. This must be reduced to prevent blowholes and imperfections in the steel castings and forgings. The carbon also is to be restored to the desired proportion to suit the uses for which the steel is being prepared. These two objects are accomplished in one operation by adding manganese and carbon in the form of spiegeleisen or of ferro-manganese, which substances contain manganese and carbon in the proportions 314 to 1 and 12 to 1, respectively. This process is called recarburization, and is effected by adding the correcting substance to the melt within the converter just before pouring, as described above by Langley, or else in the ladle after pouring. The Bessemer process just described is incompetent to convert pig iron high in phosphorus or sulphur into good steel. Messrs. Thomas and Gilchrist in England about 1880 worked out a modification adapted to handle ore richer in phosphorus and sulphur. Instead of the acid converter lining of ganister they substituted dolomite, a magnesian limestone, and also added some lime to the charge. With these modifications, the blow goes on much the same as in the usual Bessemer process, but at a higher temperature, and is continued six or seven minutes longer, during which time the phosphorus is changed to calcium phosphate and goes into the slag. Recarburiza- tion is done in the ladle. As we have noted, both Bessemer processes have yielded for the most part in the United States to open-hearth steel making. [345 | GREAT INVENTIONS In the open-hearth process the carbon of the pig iron is oxidized by oxygen supplied by fresh pure iron ore added to the melt. In order to get a temperature high enough for this reaction the charge is boiled in a regenerative furnace fed by gaseous fuel. The reaction proceeds much less rapidly than in the Bessemer process, requiring several hours for completion. This permits the condition of the carbon to be tested from time to time by taking samples, cooling them, breaking them to study their fracture, and even by chemically analyzing them. When the percentage of carbon has been diminished and ad- justed to that desired, the process is stopped. Sir William Siemens invented the regenerative or reverberatory furnace but did not immediately adapt it to the steel industry. It consists of a rectangular, boxlike hearth, with a roof of silica brick at the proper height to condense the heat. Fuel gas and air enter the box in combustion at one end, and the hot gases of combustion leave at the other end, passing through a checker work of fire brick before reaching the stack. About once every half hour the direction of the gases is reversed. In this way they come to combustion at a hotter temperature with each reversal, so that the temperature within the hearth rises higher and higher until the proper heat is attained. The gaseous fuel used in the reverberatory furnace is usually the so-called producer gas, made from soft coal. It consists of about 25 per cent carbon monoxide, 12 to 15 per cent hydrogen, a little marsh gas and other hydro- carbons, and some §§ per cent of noncombustible gases, mostly nitrogen. Producer gas is made in special retorts with fire-brick linings, wherein the soft coal is fed me- chanically from the top through an air-tight trap and kept in partial combustion by a blast of air and steam forced up from the bottom. The ash is removed by automatic machinery through an air-tight trap at the bottom. The hot producer gas is drawn off at the top [ 346 ] uoljyesodi07 [9939S $9IvIg payUy dy Jo Asaq.1n07 yuryd Jeeqs aovuIny yaavay-uado uv Jo opis suisivys va) < " z Sep te eae = esti oe = . Jee s = oli vie - . es . ot ah Sn 7 . - STl ALVTd uorqzvsodi07 903 $23¥Ig patUy) P43 Jo Asaqinoz “yid Suryvos oy) WO} UMBIP Bulg JOSUI [9938 JOY-OITY AA OTT ULV Id OUTSTANDING MANUFACTURED PRODUCTS through a pipe leading to the open-hearth furnace. Plate 114 illustrates a vertical section of a producer gas plant. Open hearths are built both with acid linings of silica brick and with basic linings of magnesite or dolomite brick. In the former case, as there is no removal of phosphorus or sulphur, these objectionable elements must be kept well below 0.1 per cent in the charge. From 1 to 2 per cent of manganese and about 0.5 per cent of silicon are included in the charge. These metals, by their strong affinity for oxygen, prevent much oxidation of the iron, which, if allowed to take place, would tend to make defective spots in the steel. Of course, the oxidation of the manganese and silica add to the heat available to make the melt. When so large a proportion of scrap steel is used in the charge that the available carbon 1s in- sufficient, coal or charcoal may be mixed into the charge to supply the deficiency. As the furnace is kept hot continuously, the charge is inserted by mechanical means, comprising steel charging boxes carried on long rams into the furnace and dumped there. When hot metal direct from the blast furnace is to be charged, it is poured from the ladle into the furnace door through a trough. Toward the end of the melt, special substances such as carbon, manganese, aluminum, and silicon are added in such proportions as tests and experience dictate to improve the composition and casting quality of the steel. Plate 115 shows the charging side of an open-hearth steel plant. In the basic open-hearth furnace, lime is added to the charge. The charge must be low in silicon and in sulphur, because the former would neutralize the basic action of the lime, and the prejudicial influence of the latter can be corrected only partially by the use of manganese toward the end of the melt. But ores high in phosphorus can be used with the basic open hearth, because phos- phorus unites with the lime and goes into the slag. Care [ 347 ] GREAT INVENTIONS must be taken only to keep the slag strongly basic by addition of more lime from time to time if necessary. Tilting furnaces, though more costly, are preferable for open hearths, especially of the basic sort, because the slag can be run off at any time to avoid recontamination of the steel by its injurious constituents. In recent times a considerable proportion of the steel manufactured in the United States has been melted in elec- tric furnaces. In foreign countries ore is also smelted electrically, but that process is too expensive in this coun- try. Both basic and acid steel-making processes are con- ducted electrically. Melted steel, however produced, is poured into open- ended ingot molds about 6 feet high, resting on heavy iron plates at their bottoms. They are nearly 2 feet square at the bottom, and tapered to a smaller section at the top, so that the molds may readily be lifted off the ingots when the outer shells of steel have solidified in the molds. The ingots are then placed in the so-called “soaking pits,” which are closed, heat-insulated chambers, where the cool- ing of the steel becomes more uniform until the solidifica- tion is complete. In Plate 116, we see an ingot, still white- hot, being drawn from the soaking pit. From the soaking pits they go to the rolling mills and forges, where the ingots are formed into “blooms” and “‘billets” and, by further working, into rails, bars, and commercial shapes. These processes are conducted on both hot and cold steel, the temperature selected for working depending on the carbon content and on the shape desired. In rolling and drawing processes the cross-section of the steel is gradually reduced by successive steps until the final shape is at- tained. This can often be accomplished in the cold. Plate 117 shows a white-hot ingot being rolled out in the slabbing mill. The picturesque figure in the history of steel making in the United States is Andrew Carnegie (1835-1919), the son of a hand weaver in Dunfermline, Scotland. The [ 348 | OUTSTANDING MANUFACTURED PRODUCTS introduction of machinery deprived his father of an occupation and drove the family to emigrate to the United States in 1848, aided by a small loan from a friend for passage money. The boy Andrew was then in his 13th year and attended school no longer, except for night school during one winter in Pittsburgh, where the family settled. There the father began weaving tablecloths and selling them from door to door. The mother took in shoes to bind, and Andrew got a job at a dollar and twenty cents a week as bobbin boy in a cotton factory. The hours of labor lasted in winter from before dawn till after dark. From this small beginning he was soon advanced to a position paying two dollars a week with a Scotsman, for whom he did all sorts of jobs, from running a small steam engine and firing the boiler to bathing wooden bobbins in oil. As he was good at figures, he sometimes helped to make out bills. The turn in Andrew Carnegie’s fortune came in 1850, when he was engaged to deliver messages from the tele- graph office. Here he wore his Sunday suit to make a good appearance, and every Saturday night, no matter how late he might return from delivering messages, his mother washed these clothes and ironed them, so that he could put them on fresh for Sabbath morning. He felt that the telegraph office job was his opportunity, and concentrated his attention on learning streets and business addresses throughout Pittsburgh. He also took pains to learn the faces of the business men themselves, so that he would be able to deliver a telegram on the street if he happened to meet the recipient. In these ways Andrew Carnegie became more and more efficient and better and better known. Such men as Edwin M. Stanton, afterward Lincoln’s famous Secretary of War, William Thaw, the business man and philanthropist, and many others of Pittsburgh’s most substantial men came to know the little Scotch boy. He also took every oppor- tunity to learn and practice telegraphy. [ 349 | GREAT INVENTIONS Col. Thomas Anderson had opened his private library to working boys, but at first boys employed as messengers and in clerical jobs were not admitted. Andrew Carnegie wrote a letter to the Pittsburgh Dispatch urging that this distinction be removed. It was removed. Every week he drew out a book and thus read history and literature. Later in life he presented to the city of Allegheny a monument to Colonel Anderson, and the generosity of this man was instrumental in influencing Carnegie later on to give millions of dollars to establish libraries all over the world. Occasionally the Scotch messenger had a telegram to deliver to the theater, and in return he was given a seat in the second balcony. In this way he came to know and appreciate the plays of Shakespeare and others. Continually improving himself and his efficiency, in about a year he was promoted above all the other mes- senger boys and received $13.50 a month. One morning, before the regular operators came, he took a message from Philadelphia, and little by little was called on afterward to watch the instrument when someone was called away. Some operators were learning to read Morse by sound, and Andrew Carnegie was one of the earliest to master it. Soon an operator 30 miles from Pittsburgh was called away for two weeks, and Carnegie, though but a boy, supplied his place. From that beginning he was soon promoted, while yet in his 17th year, to be an assistant operator. Then came the great opportunity that started his career. In February, 1853, he was selected by Thomas A. Scott, superintendent of the Pittsburgh division of the Pennsylvania Railroad to be clerk and operator, at an initial salary of $35 a month. As Scott advanced, Carnegie advanced, succeeding to the superintendency of the Pittsburgh division when Scott became Vice President of the Pennsylvania in 1859. Soon after came the Civil War, and Scott and Carnegie [350] PLATE 117 Courtesy of the © States Steel Corporation rolled in the slabbing mill. g JInited Bai White-hot steel ingot bein PLATE 118 Andrew Carnegie. Photograph by Davis and Sanford OUTSTANDING MANUFACTURED PRODUCTS went to Washington to organize the immense railway and telegraph expansion of the War Department. Through this experience Carnegie came to know well Stanton, Grant, Cameron, and other powerful leaders. Carnegie’s health was injured by strenuous work in the great heat of southern summer, so that in 1862, after being recalled to the Pennsylvania Railroad, he revisited his native Scotland with his mother. The tremendous impression this made upon him he describes most vividly in his autobiography. Indeed, his love for Scotland and _ his home town of Dunfermline was always a master passion. After his retirement from active business, he purchased property in Scotland and spent a part of each year there. Many gifts he gave to Scotland, and he nourished her old customs. Always in his Highland mansion the piper led the way for the family and guests to dine. Carnegie was one of the first to see the need of the sleeping car on American railroads. He joined with the inventor, T. T. Woodruff, in forming a company to con- struct sleeping cars for the Pennsylvania Railroad. Later on he combined with George M. Pullman in forming the Pullman Palace Car Company. These were very profit- able investments. Another profitable venture was the organization with Thomas N. Miller in 1866 of the Pittsburgh Locomotive Works. In 1906 its $100 shares sold at $3,000, an appre- ciation of thirtyfold. Carnegie was quick to see also that the day of wooden bridges was passing, and with four associates he organized the Keystone Bridge Company in 1863. They built many cast iron bridges in the early days, but Carnegie soon realized the advantage of Bessemer steel for bridges and rails. His long service with the Pennsylvania Railroad had shown him the weakness of iron rails. In 1873 Carnegie and others organized the Edgar Thomson Steel Company at Brad- dock, Pa. The business of the Pennsylvania and Baltimore & Ohio railroads as well as other lines flowed in. Mills [351] GREAT INVENTIONS were added to mills, and the great firm of Carnegie, Phipps and Company was created. Mines and transpor- tation were taken into their enormous steel industry which at last merged in the United States Steel Corporation. Carnegie also had a profitable part in the development of oil in Pennsylvania. About 1870 he removed to New York with his mother and took part in great financial operations, involving such powerful organizations as the firms of Pierpont Morgan and Company, the Barings in London, and others. In short, Andrew Carnegie was not only the great steel magnate, but the great man of affairs, exercising a powerful national and international influence for many years. In April 1887, at the age of 52 years, he married Louise Whitfield, with whom he lived a most ideally happy life. In 1go1, having built up an immense fortune, Andrew Carnegie retired at 66 years of age, and devoted himself to giving this fortune away. To his friends, the workmen in the steel mills; to Carnegie Libraries; the Carnegie Hero Fund Trusts; Carnegie organs; the Carnegie Institute at Pittsburgh; the Carnegie Institution of Washington; the Pan American Union Building at Washington; the Peace Palace at the Hague; the Carnegie Corporation of New York; the Carnegie Trust for the Universities of Scotland; the Carnegie Dunfermline Trust; the Carnegie United Kingdom Trust; the Carnegie Foundation for the Ad- vancement of Teaching; the Carnegie Endowment for International Peace—gifts to all these philanthropies organized during his lifetime involved the expenditure of $3 50,000,000. CHAPTER XI THE, GRAPHIC: ARTS Pictures have always been considered valuable as an aid to the printed word but never to the extent that they are at present. In olden times their rarity must have made them doubly precious. The beauty of the ancient handwork lends great charm to early manuscript books. Woop AND STEEL ENGRAVING At the time of the invention of printing from movable type, ascribed to Johan Gutenberg of Mainz (1398-1468) about the year 1450, the art of wood engraving was already available for crude illustrations. Indeed from the time wood carving was begun, prints of a sort must have been made. In its simplest form, the removal of the wood from around a letter or image drawn upon its surface leaves in relief a structure which, if inked, will print itself reversed, left for right. But such a print is only a black mark on a white ground. The next step is to make shading. This is done by cutting lines, parallel or crisscrossed in parallels, across the raised structure. If the incised lines are thin, the black print is but little lightened, but if the lines are wide, so as to cut away a large proportion of the raised structure, a light shade results in the print. Thus all varieties of shade can be made in a woodcut by altering the proportion of printing structure cut away by incising lines across it. The work of illustrating by woodcuts naturally divided itself between two artists, the draughtsman who composed the picture, and the engraver who reduced it to a printing [353] GREAT INVENTIONS form. It was easy for the engraver, if he had little artistic imagination, or but little skill, to spoil the choicest composition of an artist. Some men combined the two professions in their own persons. Thus Albrecht Direr (1471-1528), who has been called “the typical artist of the German nation” was at the same time a great painter, a great wood engraver, and a master of copper engraving. Plate 119 is an example of his work. Boxwood cut across the grain and smoothed to a fine flat surface was the usual medium of the woodcut. The drawing could be made directly on such a surface, but it was an improvement to coat it first with Chinese white. Then the drawing stood out as if on white paper. The artist might indeed indicate the degree of shading by drawing every line the engraver was to incise, but this was too laborious in general, and the shading was merely indicated by broad sweeps, leaving its execution to the skill of the engraver. A very long time was required to illustrate a book by these methods, a single large engraving sometimes occupying the craftsman for a month. Accord- ingly, it was customary to saw the block containing the picture into sections, each to be engraved by a different workman, and all finally joined together for printing. Copper and steel were used for printing pictures about as early as wood. But here we find the opposite applica- tion of the ink. For it remained in the incised lines and was wiped from the smooth surface. By heavy pressure the paper was forced into the incised lines and carried away the ink therein. The deeper the lines, the more ink they carried and the darker the shade produced on the print. Copper was easier to engrave, but steel was more durable and hence more suitable when numerous copies were to be struck off. Not only Durer, but other great painters, as Rubens and Raphael, favored the metal en- graving, and some of them became adepts in the art. Like the woodcut, steel engraving has become nearly obsolete, except for works of pure artistry and for the engraving of [354] THE GRAPHIC ARTS business and calling cards and certificates of various kinds. We have mentioned two contrasting classes of engrav- ing. Wood engraving is an example of printing surfaces produced in relief, steel engraving an example of the intaglio, wherein incised lines hold the ink. There are, besides, methods of lithography in which the printing surface is neither raised nor lowered, but selected by chemical preferences. Lithography, as its name indicates, arose from the use of hard, flat, polished limestone as the printing surface. This stone was selected by Alois Senefelder (1771-1834), the inventor of lithography, at Solenhofen in Bavaria. No better stone for lithography has ever been found elsewhere, but, in recent years, aluminum or zinc is substituted for stone. A drawing may be made in a special kind of ink resistant to the action of acids. The remainder of the surface not inked, may then be etched away to a certain depth with acid leaving the inked parts as a printing structure in relief. This was the original method of Senefelder, though he devised and practiced nearly all of the varieties of lithography known even at the present day. If the stone is fine-ground, but not quite polished, drawings may be made upon it with greasy crayon. If the whole stone is dampened, the ink from an inking roller will adhere to the greasy portions but not to the others. Thus there is produced a printing surface neither raised nor lowered. In the several methods of reproduction thus far men- tioned, left and right become reversed in printing, so that if the drawings are made directly on the printing surfaces to be engraved, they must be drawn with this in mind. It is possible, however, to make a drawing on paper in natural form with such inks or crayons that when the drawing is inverted and pressed down upon the litho- graphic stone or the wooden block it will be printed in greasy lines in the inverted form required. Then the en- graving process may be carried out on the duplicated drawing as thus reversed, left for right. [355] GREAT INVENTIONS Compared with wood or steel engraving, lithography is much less expensive and, at the same time, more rapid. It lends itself well to color work. For this purpose, a number of stones are prepared, each containing only those parts of the picture to be printed in the same color. An outline of the picture is prepared on a stone called the key, and the patches to be printed in different colors are carefully outlined thereon. Each color-stone is then prepared in exact duplication of only those parts of the key which are to be in the particular color selected. All the contributing color-stones are then printed one after another with exact superposition or, as it is called, register. A great advantage of lithography, and that which particularly appealed to Senefelder, is the facility and cheapness with which drawings may be multiplied by it. Any line drawing or sketch if made in an ink rubbed up in linseed oil, giving it a greasy quality, may be trans- ferred to stone by mere impression, leaving the drawing itself unimpaired. The stone, first dampened, may be “rolled up” in any color of printing ink. The ink will adhere only in the greasy lines, and impression after impression may be taken from it by merely repeating the dampening and “rolling up.’”’ As the stone carries a negative image in greasy lines, all the impressions from it are positives, and are exact duplicates of the original drawing or sketch. PHOTOGRAPHY The art of illustrating has been entirely revolutionized in the last half century by the introduction of photographic methods. It will be convenient to defer further descrip- tion of the illustrative processes of the present day until we have mentioned the discovery and development of photography. It is said that the gradual blackening of silver and its compounds was known to the ancient Egyptians. It was [ 356] PLATE 119 NN | y) The Knight and the Lansquenet. Woodcut by Albrecht Durer, 1479. Courtesy of R. P. Tolman THE GRAPHIC ARTS Heinrich Schulze, however, who published in 1727 the proof that it was not air or heat, but light, that had the power to blacken the salts of silver. He exposed to sunlight paper moistened with silver solutions under stencils cut with words and sentences, and found that the parts on which the stencils permitted light to fall were blackened. In 1777 the great Swedish chemist, Carl Wilhelm Scheele, exposed silver chloride to light for a long time, until it became thoroughly blackened. Then he removed what was left of the unchanged silver chloride by dissolving it in caustic spirit of sal ammoniac. A black powder remained. This, he was able to prove, was metallic silver. Thus the action of light was proved by Scheele to consist in the reduction of silver salts by the separation of metallic silver. Although the sensitiveness of the salts of silver to the action of light is by far the most important fact in photog- raphy, it was not the basis of the first practical photographic process—that invented by Joseph Nicéphore Niepce (1765-1833). For his light-sensitive coating he used the bitumen of Judea, a kind of asphaltum, dissolved in the essential oil of lavender. This he spread thinly as a varnish on a glass or silver plate and warmed it upon a heated iron till the varnish ceased to simmer. After a sufficient exposure in the camera, often six or eight hours, a very faint outline became visible. The image was developed in a solution of one part by volume of essential oil of lavender in ten parts of the oil of white petroleum. When the image had sufficiently developed, the plate was washed in running water and dried. But the picture had to be protected from the action of light and humidity. Copies of engravings could be made with long exposure to light by pressing them upon the varnished glass plates already described or on varnish laid on polished silver. The silver could afterward be etched with acid to prepare it for printing if desired. After some years Niepce adopted the improvement of darkening the silver plate with [357] GREAT INVENTIONS iodine, and this led the way to the true beginnings of modern photography in the beautiful work of Louis Jacques Mandé Daguerre (1789-1851). In January, 1839, six months before Daguerre published his process, William Henry Fox Talbot (1800-1877) communicated to the Royal Society of Great Britain his method of preparing sensitive photographic paper by alternately dipping it in a weak solution of common salt and applying to one side only a weak wash of nitrate of silver. The chloride of silver thus formed upon the surface of the paper proved very sensitive to light, so that Talbot was able to get good images of objects with exposures in the camera of a half second. He found that the sensitiveness could sometimes be enhanced by setting the paper aside for several weeks, and then again washing it with silver nitrate. Niepce, having learned of the experimental work of Daguerre, made a partnership with him in 1829, continued after Niepce’s death in 1833 by his son, Isidore Niepce. Daguerre’s invention was not reported until 1839, when he and Niepce were pensioned for life by the French Govern- ment. Daguerreotypes were made on polished silver- plated copper. The polishing must be done immediately before the next operation of sensitizing the surface with the vapor of iodine. The action of the iodine vapor was continued in a closed box until the silver had taken on a golden-yellow color, which, depending on the prevailing temperature, occurred in from § to 30 minutes. Only weak light could be admitted for viewing the condition of the plate. Exposure was then made in the camera and continued from 3 to 30 minutes, according to the light. The plate was then inclined face downward in a tight box, and exposed to the vapor of mercury. In a few minutes the picture was developed, but still had to be withheld from the light. After being washed in water, the image was finally fixed by rocking the plate face [358 | THE GRAPHIC ARTS downward in a bath of a weak solution of sodium hypo- sulphite. When all the yellow color disappeared, the plate was carefully washed and all drops of water blown from its surface. The shadows in the daguerreotype are given by the polished silver, the lights by the adhering mercury. As discovered by the Swedish chemist, Scheele, metallic silver was thrown down in the silver iodide coating under the influence of light. The metallic silver grains alloyed with mercury produced the high lights. Glass covers were placed over daguerreotypes to protect their surfaces. Their beauty is proverbial. Fox Talbot improved his paper-coating process by substituting the iodide for the chloride of silver, and patented it in 1841. It was called the calotype process, and was repeatedly improved by him to secure great sen- sitiveness. He accomplished instantaneous photography in 1851. By that time he was using as the surface to be sensitized a glass plate coated with albumen, which, when dry, he dipped in an alcoholic aqueous solution of silver nitrate and again dried it. The nitrate seemed to unite with the albumen in a chemical union, resulting in a hard insoluble surface. The plate was next washed to remove the excess of silver nitrate. To an aqueous solution of the protoiodide of iron was added an equal volume of acetic acid and 10 volumes of alcohol, and after standing several days the preparation was ready for use. The plate was dipped therein for a few seconds only. All the preceding operations could be done in weak light, but when the plate was then dipped in a weak solution of silver nitrate to which acetic acid had been added, it became highly sensitive and was placed in the camera without delay. To develop the image, it was dipped in a solution of the protosulphate of iron, where- upon the image quickly appeared. After being washed, the plate was dipped for a minute in a solution of hypo- sulphite of soda and then again washed. [359] GREAT INVENTIONS Here we find for the first time Fox Talbot using a glass plate coated with an organic substance as the carrier for the sensitive silver salt, but he was not its earliest user. Its invention is ascribed to Niepce de Saint-Victor, a nephew of the elder Niepce, in 1848. Collodion, and later gelatin, were substituted for albumen, but the practice of using a wet plate in photography was continued, as in Fox Talbot’s experiments, for many years. It was inconvenient and entirely unsuitable for the use of the traveler. Fox Talbot had by this time invented the process of silver printing, so that pictures could be in- definitely multiplied. In 1864 W. B. Bolton and B. J. Sayce introduced dry plates, the improvement which revolutionized photog- raphy. Prior to this time the collodion films in use were first impregnated with the bromide or iodide of potassium or sodium. Corresponding silver salts were thrown down in the film by immersion of the plate in silver nitrate. Silver iodide was still preferred, but Bolton and Sayce turned to silver bromide as the sensitive salt and found it possible to prepare it in a state of fine suspension with collodion. When the glass plate was coated with this preparation it could be used wet, as usual, but it was also effective when dry. Carey Lea, of Philadelphia, greatly improved this emulsion process and increased its sensitiveness. By this time the discovery had been made of the action of alkaline developers to bring out the image. During the decade of 1870-1880 many investigators improved the dry plate, substituting gelatin for collodion in the emulsion, and increasing the rapidity of the film till it became about 100,000 times as fast as the original daguerreotype. The next decade saw another revolution in photography, brought about by the devotion of a bank clerk amateur. What Thomas A. Edison was to incandescent electric lighting, and Henry Ford to automobiling, George [ 360 ] PLATE 120 Courtesy of the Eastman Kodak Company George Eastman. Aurdwo sy YEPOy UBUUASE 2p! Jo Asaq.ino7 *suuyy yepoy SULINJOvJNULUI jo poyjyou UJIIPOTNY ig SE y ~~ ==" —_—G Wel HLVId THE GRAPHIC ARTS Eastman (1854-1932) was to photography. He made it universal. Even more, not content with making every traveler and vacationist his own photographer, he created the largest and most all-embracing photographic business in the world. There is no ramification of the art, from astronomical photography to moving pictures, that has not received scientific advancement, leading to important commercial values, from the Eastman Kodak Company of Rochester, N. Y. In that gigantic business enterprise George Eastman made a huge fortune, but, like Andrew Carnegie, he gave it nearly all away before he died. His known benefactions to educational and human- itarian projects, as listed by the Associated Press and quoted in the Literary Digest for March 26, 1932, ex- ceeded $75,000,000. George Eastman, son of George W. Eastman, who conducted a business training school called Eastman’s Commercial College, was born at Waterville, N. Y. His father’s income, though sufficient, was small, and when he died in 1862, Mrs. Eastman was forced to resort to taking in boarders. Thus, like Carnegie, George Eastman knew poverty as a boy. In 1868 he left school to go to work with an insurance firm, and began at once to keep a cash book. At the end of the year he made this entry: ! Recapitulation 1868 1868 Rec’d during Year ($) 131.00 (paid Clothes 39.00 Board 20:92 Sundries 16.35 Shoes 8.05 Underclothes, etc. 3.03 Hats 3-35 92.00 39.00 Assets 1868—Mar. 2d ($) 5. 1869—Jan. I 39. Increase ($) 34. 1 George Eastman, by Carl W. Ackerman. Houghton, Mifflin Company, Boston, 1930. [ 361 | GREAT INVENTIONS Early in 1869 he began to make entries recording the purchase of photographic materials. In April, 1874, he received the post of junior bookkeeper in the Rochester Savings Bank, and in 1876, then receiving a salary of $1,400, he relieved his mother of all financial responsi- bilities. By January 1, 1877, he had saved $3,600. Toward the end of that year, he became so much interested in photography that he purchased the then cumbersome outfit required for picture making and took lessons of a local photographer. It was the wet collodion plate process. Eastman records that his outfit, which included only essentials, comprised a good-sized camera, a heavy tripod, a large plate holder, a dark tent, a nitrate bath, and a jug of water. He says: “Since I took my views mostly outdoors—I had no studio—the bulk of the paraphernalia worried me. It seemed that one ought to be able to carry less than a pack-horse load.” Then he learned that dry plates could be made, and he attempted to make them, at first with little success. But working long hours at night he found a coating of gelatin and silver bromide that worked successfully. Then he thought, “I will sometime give up the bank and go altogether into the photographic business, making and selling dry plates.” He asked his uncle Horace Eastman to help him start in this venture as a partner, but his uncle declined. But George Eastman was not discouraged. He took his own savings and began working outside bank hours. In 1879 he invented an improved process for coating dry plates, and registered the patent in England and France as well as in the United States. He went to England to push the introduction of his process, and in December, 1879, sold the English rights for about £500. In 1880 he invented a second radical improvement in dry-plate making, and by the end of that year he had a well-established, widely known business, with foreign connections in several principal countries. Just at the end of 1880, Col. Henry A. Strong joined [ 362] THE GRAPHIC ARTS him as a partner, and in September, 1881, George Eastman gave up his position with the bank to devote himself entirely to photography. Eastman first conceived the idea of the transparent photographic film, independent of a glass backing, early in 1884. A modern method of manufacturing kodak film is shown in Plate 121. He made many experiments in that year by coating glass and also paper with solutions of nitrocellulose, stripping the film from the glass or paper when solidified. But at first his nitrocellulose films were too thin for camera exposures if used alone. Therefore he decided to leave the film on the paper until after exposure. A patent on the new product was applied for in March, 1884, and shortly afterward its adjunct, the roll-holder, was worked out by Eastman and W. H. Walker in a form adapted to be used in any camera instead of glass plates. The film was wound on spools and moved by a clock key from outside. Rolls containing 24 exposures were supplied. On October 1, 1884, the Eastman Dry Plate and Film Company of Rochester was incorporated with a paid up capital of $200,000. There were 14 stockholders. The officers were Henry A. Strong, president; J. H. Kent, vice president; George Eastman, treasurer; and W. H. Walker, secretary. The paper-backed film, though successful, was not what Eastman wanted, and in November, 1886, he engaged a young chemist, Henry M. Reichenbach, to try to develop the film that could be exposed alone. About this time he bought a patent of a young Dakota farmer, David H. Houston, which was a visible indicator and film-puncturing device, suitable to point out when a length of film had reached the required position for exposure. Reichenbach solved the film problem in 1889. By dissolving nitrocellulose in wood alcohol and adding camphor, fusel oil, and amyl acetate to the solution, the film when dry came out firm, transparent, and flexible. [ 363 | GREAT INVENTIONS Eastman invented the roll devices for exposing these films, and patents were applied for March 3, 1889. The patents covered the chemical formula, the mechanical processes for making and coating films, and the apparatus for holding and exposing them in the camera. Even before this, in September, 1888, the kodak had been born. The word and the camera it signifies were both of Eastman’s invention. The word was his coinage of a name that was short, incapable of being misspelled to destroy its identity, vigorous in sound, and able to meet foreign trademark requirements. Kodak Camera No. 1 was a box 634 by 334 by 334 inches, producing a circular picture 2% inches in diameter and loaded with a stripping film roll for 100 exposures. The camera had to be sent back to Rochester by the user, where the film was unloaded, developed and a new film inserted. In his advertisements Eastman coined the slogan “You press the button—We do the rest.”’ It took like wildfire, even penetrating into the Gilbert and Sullivan opera, “‘Utopia.” Two modest maidens carrying kodaks amid a chorus of kodakers sing: Then all the crowd take down our looks In pocket memorandum books. To diagnose Our modest pose The kodaks do their best: If evidence you would possess Of what is maiden bashfulness, You only need a button press— And we will do the rest. Amateur photographers multiplied all over the world so fast that the company could not increase facilities fast enough to meet their demands. Soon after Reichenbach’s film came out, Edison, who was working on his moving picture inventions, began to order films. Later on, when the Edison invention came into popular vogue, after 1900, the moving picture film business became a principal line of the Kodak Company. | 364 | PLATE 122 Assembling kodak shutters. Courtesy of the Eastman Kodak Company Auvduioz yepoy uvuysey ayy jo Asayinod = soded s1ydess0j0yd ojur speur oq 0} djnd Sutredaid ssjvog fc} ALVId THE GRAPHIC ARTS A far-reaching commercial arrangement was entered into by many of the movie producers with Edison and Eastman. As business in all photographic products and associated lines was added to the kodak industry, the great establish- ment in Kodak Park at Rochester was built up. Plates 122 and 123 show the assembling of kodak shutters and a beater preparing pulp to be made into photographic paper. A great factory was also established at Harrow, England. So extensive became the ramifications of the Kodak Company that the Government, during Woodrow Wilson’s administration, attacked it in suits under the Sherman Act. These suits were pending over a long term of years but were held in abeyance during the World War, while the exertions of Eastman and the company were a powerful support to the Government and the Allies. Eventually the antitrust suit of the Government prevailed, and some of the subsidiaries of the company were excised. Eastman was a pioneer in building up his production and executive staffs with men of technical school or college training. He had obtained several first-rate men from the Massachusetts Institute of Technology, one of whom, Frank W. Lovejoy, is now a vice president and the general manager of the Kodak Company. Dr. Richard MacLaurin, the revered president of the Institute, whose untimely death was so greatly deplored, explained to Eastman his visions of what the future growth of Tech- nology demanded. Greatly to MacLaurin’s surprise and delight Eastman entered enthusiastically into these large enterprises, and only stipulating that his name should be concealed, in a period of several years he gave toward the establishment and development of the great institu- tion now on the bank of the Charles River no less than $19,500,000. Many other educational enterprises en- listed Eastman’s attention during the latter years of his life, to which he gave not only much thought and time, but, as has been said, very large sums of money. [ 365 | GREAT INVENTIONS The introduction of photography had an enormous effect on the arts of illustration. The camera could reproduce any view almost instantly, with far greater fidelity of detail than the most skillful artist. To be sure the photograph might fall short of the drawing or painting in artistic feeling, but when an automatic process was found for transferring the photograph to the printed page, the final result might be more artistic than a copy of the artist’s sketch if unskillfully reproduced by hand en- graving. PHOTOENGRAVING Photographic engraving came in about 1860. It is based on a curious property of albumen, gelatin, and other colloidal substances. When a suitable film of gelatin (or gelatin and albumen), impregnated with po- tassium bichromate, is exposed to light, the film tends to become insoluble in water. The degree of indifference to water, roughly speaking, is proportional to the intensity and duration of the exposure to light. In applying this discovery, which was made by one Mungo Ponton, to the reproduction of line drawings, India-ink cartoons, and similar figures, which have only narrow blacks and whites but no half tones, a contrasty negative photograph of the desired size is first made. As it is convenient to strip off the negative film from the glass plate, the photoengraver uses special plates of strong contrast adapted to the film stripping required. Usually the object gained by removing the film is merely to have left and right interchanged. Otherwise the reproduction would be a mirror image of the original. If left and right were to be exchanged in the next step of the process without stripping the film, it would be necessary to print with the glass side next to the bichromated film, which would give blurred indistinct lines. A prepared zinc or copper plate having been coated with the gelatin-albumen-bichromate film, the stripped [ 366 | THE GRAPHIC ARTS negative is closely pressed thereon under glass and printed by suitable light exposure. Hardly any visible effect is produced, but the clear spaces, which in the negative represent the lines going to make up the drawing or cartoon, give hardened insoluble reproductions in the bichromatized film. The dark parts of the negative, on the contrary, are unaffected, and remain soluble in water. The metal plate is next “rolled up” with an ink roller carrying acid-resisting ink, and then soaked in cold water, which softens the parts not exposed to light till they can be washed away. After the plate is scrubbed it is next etched with nitric acid in order to leave the parts covered by the insoluble film in relief. After the etching has gone deep enough to clearly mark the drawing, the plate is dusted with asphaltum or with dragon’s blood, a product of a West Indian plant, and warmed so that the sort of varnish thus produced may more effectively protect the lines which now represent the drawing or cartoon from undercutting by further etching. After several such treatments all large etched areas are “‘routed out’ deeper with a mechanical cutter. The plate is then mounted on a wooden block, type-high, and is ready to be inserted in its place in the page for printing. When large editions are to be printed, printers do not rely on the original blocks and type, but only use them (slightly dirtied to prevent adherence) as negative poles in an electroplating bath, thereby making an exact negative of the printing surface. This in turn is used as a negative pole, and upon it is deposited a copper replica of the original printing surface, exact in every detail. This surface, suitably backed, is used for printing. Such a process of line engraving by photography came into use more than a half century ago and speedily dis- placed wood engraving, except for especially artistic work. But it was not immediately applicable for views containing large areas of continuous shade and grays, [ 367 ] GREAT INVENTIONS rather than blacks. Some means of breaking up such half tones and shades into narrow blacks and whites was required. This was furnished by the invention perfected by Frederic E. Ives, of Philadelphia. Imagine a flat glass plate, coated with an acid-resisting film, to be scratched with parallel lines, about 150 to the inch, so that it becomes alternately transparent and opaque. This glass plate is etched with hydrofluoric acid to deepen the transparent lines, and then the film is removed and the incised lines are filled with opaque. Ives combined two such screeens at right angles, by pressing the two screens together face to face and cementing them to- gether. The device then becomes a uniform black ground pierced with a great number of regularly spaced pinholes. When such a screen is placed within the copying camera, close to the plate on which a negative of a picture is to be made, the result is to break up all the half tones and extended whites of the negative by inserting thereon a multitude of black dots. Such a negative may be used as already described for photoengraving, and the shades will appear to the unaided eye as if continuously printed. Under a microscope every half-tone engraving shows the multitude of dots by means of which it was produced. It is a matter of great nicety to adjust the distance of the half-tone screen from the negative, the size and shape of the aperture of the camera lens, and the length of the exposure so as to produce a negative capable of giving the most satisfactory reproduction of a picture. Owing in part to the irradiation and diffraction of light, the cone of rays which diverges from one of the pinhole apertures of the screen toward the negative is enlarged. It is the more enlarged the larger the lens aperture, the longer the exposure, the greater the separation of the screen from the negative, and the brighter the light. The high lights from the picture produce on the negative dots of the shape of the diaphragm of the lens, which are so large as almost to coalesce and blacken the negative. Medium [ 368 | THE GRAPHIC ARTS shades produce smaller dots, and the dark shades produce very small ones, leaving most of the negative in their region clear. When the negative is printed on bichroma- tized gelatin, the parts corresponding to high lights on the original picture receive little light, and nearly wash away. Those corresponding to deep shades are strongly illuminated. In these regions, the gelatin 1s hardened and washing does not remove it. Therefore, when the plate is etched and printed, we find the same sort of shading as in the original picture, but the accuracy of the repro- duction depends on the skill of the engraver in his adjust- ment of the items mentioned above. Where several printings are made for color work, the dot-lines of the screen are inclined at different angles to the vertical in each, so as to avoid interference of the dots. A great deal of modern illustration involves color. Prof. James Clerk Maxwell showed in 1861 that any desired color may be reproduced by a proper mixture of three well-chosen primary colors. The colors required may be chosen in several ways, but are often taken as red, jyellow;, and) blue.) In \1881, Frederic, E. Ives, of Philadelphia, perfected a modification of the half-tone photoengraving process adapted for color printing. He was able to produce three filters, which, when interposed before the negative, cut off, respectively, all the light from the object not red, all not yellow, and all not blue. Such filters may be made of transparent colored glass, coated glass, or colored water cells. Taking then, through appropriate color screens, three equal-sized negatives, printing plates could be made from them by the ordinary process. Then, choosing inks of correct colors, by three superposed printings the approxi- mate coloration of the original object or painting could be reproduced on the printed page. In many of the col- ored illustrations of the Smithsonian Scientific Series the colors of the originals have been imitated by the use of not three, but many more than three printings. With [ 369 ] GREAT INVENTIONS this meticulous care, and skillful choice of filters and inks, almost exact color reproduction is possible, but, of course, very costly. PHOTOLITHOGRAPHY J. W. Osborne of Melbourne, Australia, patented in 1859 his process of photolithography. It is not directly applicable to shaded pictures, and is based, like almost all photoengraving processes, on the peculiar action of light on bichromatized colloids. First, a negative is made of the picture to be reproduced. A film of bichromated albumenized gelatin is prepared and printed from the negative. As usual, the bichromated film is hardened in proportion to its exposure to light and is also rendered insoluble in water in a proportional degree. A flat zinc plate is “rolled up” with transfer ink, and the print is then pressed face down upon it, thus becoming inked all over. Next the film is floated, back downward, in water a little below the boiling temperature. The heat coagu- lates and hardens the albumen as it does the white of egg, and makes it tenacious enough to withstand the rubbing process to follow. The hot water penetrates the film and dissolves out the bichromate in the regions little affected by exposure to light. Next the print is scrubbed with water, which leaves the transfer ink adhering in the parts where there has been exposure to light. Transfers are then made to lithographic stones or metal plates, in the manner already described, and from these stones impressions may be struck off indefinitely as desired. A very large collection of photolithography and specimens of other photoengraving processes, the gift of J. W. Osborne, is on exhibition in the division of graphic arts, United States National Museum. Photolithography may be extended to shaded and colored subjects by first photographing the originals through appropriate line screens and color screens as if for process engraving. Seven or eight color stones are [370 ] THE GRAPHIC ARTS often printed to represent a single original subject by the lithographic method. PHOTOGRAVURE This development of intaglio engraving is much used. The so-called rotogravure section of the Sunday news- paper is one application of it. Let us first consider the carbon tissue process. ‘Thin tissue-backed films of gelatin, impregnated with lampblack or color to different degrees of shade, are prepared and sold to the trade. When bathed in bichromate solution they become light-sensitive. Such a film, when mounted on glass and exposed under a reversed stripped positive photographic film, becomes hardened and insoluble in water in its high lights, but not in its shadows. A copper plate is given a reticulated ground by dusting it with bitumen or resin and warming it so that the dust adheres. The gelatin film is mounted thereon, and its tissue and soluble parts are scrubbed away with warm water. Then the copper plate is etched with acid. The acid percolates but slightly through the hardest parts of the gelatin, but more freely through the half-tone spaces, and most freely through the clear parts. In this way the shades of the original are reproduced as incised corrosions varying in depth and size according to the degree of shade. Several successive etchings may be needed, stopping out parts too much affected if necessary. Impressions are made on damp paper with soft backing, which sucks away the ink that fills the incised pockets and pits in the metal. This process was developed by Karl Klietsch of Vienna, who removed to London and there adapted it to cylinder printing, as used in the rotogravure newspaper section of today. Its application to rotogravure is nearly identical with the process just described. Instead, however, of depending on aquatint ground for the reticulation, a crossed screen of 150 to 175 lines is printed on the carbon [371] GREAT INVENTIONS tissue film, in addition to the reversed positive. After being soaked in cold water, the film is squeegeed onto a chemically cleaned copper cylinder. Then water at 104° F. is applied until the carbon tissue, bichromate, and unaffected gelatin are removed. After this the cylinder is etched with acid. When printed, the cylinder revolves through a trough of ink. The excess of ink is scraped off cleanly by a razorlike blade called “the doctor,” and the cylinder prints as from an etching as the soft moistened paper absorbs the ink from the incised lines. Color engraving may be done by these photogravure processes. Separate plates or cylinders are then prepared, corres- ponding to each color printed. The colors are selected by photographing the subject through color screens, and the inks for printing are chosen by persons skilled in the art so as to give, when all are superposed, the most satisfactory color reproductions. OTHER PROCESSES A very ingenious and curious method of engraving was perfected by Walter Woodbury about 1864. He printed his negative on bichromated gelatin, and washed away the parts unhardened by light. Thus a structure was formed in which parts corresponding to the high lights of the original subject were washed away, and those parts corresponding to deep shadows were in relief. By hydraulic pressure he forced this structure into suitable soft metal, as lead or type metal. Thus he made a shallow mold into which was pressed warm gelatin impregnated with lampblack, or other more or less opaque powder. The warm gelatin was backed by white paper, which adhered to the gelatin and removed it from the mold when set. It will be seen that the white paper would shine through and make high lights where the mold was shallow, and would be obscured by the opaque gelatin where the mold was deep. These areas would correspond to the original high lights and dark shadows of the [372] THE GRAPHIC ARTS subject. Good reproductions were made in this way, but it was a costly process and never came into general use. We have spoken of the relief process depending on etching away the ground; of the planographic process depending on chemical affinity and rejection of the ink; and of the intaglio processes where the ink is contained in incised lines or pits of greater or less depth below the printing surface, and is sucked out under high pressure by the soft, moist paper on which the impression is made. One other important type of engraving remains to be men- tioned. It is the collotype or photogelatin method, which exists In numerous variations called albertype, autotype, artotype, heliotype, etc. A film of bichromated gelatin mounted on glass or metal is exposed under a photo- graphic negative, and then washed until it slightly swells. As in the Woodburytype, the film takes on a relief struc- ture of different degrees of relief and hardness depending on the exposure to light. Moreover, as the film dries, it cracks in innumerable directions, so as to produce a reticulation akin in its printing possibilities to that produced by a half-tone screen. The quality of these reticulations also varies with the exposure to light. The parts most exposed and hardened are insoluble, and there- fore in lowest relief. They are most receptive of ink, while the parts most swelled by water are least receptive of ink. Accordingly when “‘rolled up” with ink, the gelatin film prints a reproduction of the lights and shades of the original subject. These gelatin collotype processes give the most exact reproductions of fine detail of any of the methods of engraving, and their prints are very pleasing in appearance. Furthermore they, like the others, are susceptible to color methods, and in much the same way. Very beautiful color reproductions are thus produced. The collotype processes began with Poetevin in 1855, were improved by Motay and Marechal about 1865, by A. Albert of Munich a little later, and by Ernest Edwards about 1872. £373. GREAT INVENTIONS Like other processes, they awaited the introduction of color screens (about 1880), and many variants of them have been devised in more recent years. In conclusion, we must recall the useful expedient for laying on tints in drawings and engravings devised by Benjamin Day in 1879. It consists of a flexible, trans- parent film, as of celluloid or other similar substance, on the lower side of which is contained a reticulated surface of some sort. Many varieties of such patterns are avail- able commercially, from cross-hatching and double cross- hatching of few or many lines per inch, to curved and waved lines and irregular reticulations. In short, the available screens cover everything in degree of shade and character of pattern that the artist might desire to place upon his drawing. The Ben Day screen, chosen as required, may be inserted in a hinged frame which can be adjusted to lie upon a drawing or engraving plate in the making. If shading is desired in a drawing, a diaphragm of thin paper is fastened temporarily upon it, out of which are cut the shapes within which the shading is to be included. The Ben Day screen is “rolled up” with ink of the proper color, and then let down into contact with the drawing. By means of rubber rollers of different sizes, burnishers and other special appliances, the screen is pressed down onto the paper, and prints the desired shading on the drawing everywhere it is needed and nowhere else. Still other uses are found for the Ben Day screens. From a drawing a photographic negative of the desired size for printing is made. From this negative a faint image is printed on sensitized zinc. Those parts not requiring to be shaded are stopped out by painting with gamboge. On the remainder the Ben Day screen, after being “rolled up” with acid-resisting ink, may be im- pressed. Then, after washing off the gamboge, the plate is etched with acid according to usual methods of zinc etching, and used for printing as desired. [374 | “THE, GRAPHIC. ARTS The Ben Day shading methods are much used for color work in children’s books and for funny pages of the Sunday papers. They may even be used for fairly good four-color engraving, although by no means as precise in their outlines, or as delicate in gradations of shading, as other methods already mentioned. Examples of most of the modern processes of reproduc- ing illustrations will be found in the volumes of this Series. All of the plates in this volume except the frontispiece are reproduced by the half-tone process, and the text figures are line engravings. The frontispiece illustrates the vari- ous stages and the final product of the four-color process. In volume g, plates 28, 41, 70, 83, 94, and 104 are ex- amples of color lithography, and reproductions by the photogravure process appear in volume 2 as plates 6, Io, KQ.g25.) 35,137) §3,,and 72. The entire text matter and text illustrations of volumes 5, 7, and 8 have been repro- duced by the lithographic offset process. In every kind of engraving, great skill and long ex- perience are indispensable for choice results. Very many fine points well known to the experts have necessarily been neglected in this brief account, but it is the hope of the author that enough has been indicated to stimulate interest in methods of illustrating in readers who have known little of engraving processes. Indeed, the same reflection is in the author’s mind regarding all the subjects treated in this volume. He begs the indulgence of expert critics, and asks them to consider that it is not for them, but for the general reader unfamiliar with electricity or machines that the book was written. The author’s object will be attained if the book leads young people to a greater interest and better under- standing of many of the ingenious inventions which have multiplied by a thousandfold the opportunities and comforts of modern life. [375] Lt yeas men haere Love te a ote nul: ah i. ied) bul bie anit i Ail Maeha ee ‘i) AY gh ety hak fbi rey . nee } aw ig fe hilo an fa ud iy. Hhastaiii uh Wadia vy ee ‘ 4 eset pooh Se a: CRRA) Whit) eats nate: hs *. Me Dadaist fi a “4 ide Moor wit 7. Ay INDEX A Aeronautics, National Advisory Committee for, 232-236 Agriculture, inventions for, 300- 308 power applications, 308 Air brakes, 196-198 Airplane, 225 early flights, 225-230 engines, 177, 179 testing of, 236 Alexanderson, E. F. W., 47 alternator, 122 American Telephone and Tele- graph Company, 110, 113 Ammonia, properties, 240 Amplifier, electron tube, 58,60,112 Arago, Dominique Frangois Jean, I, 3, 13, 86 Arc, 70 Arc lighting, 147 Arkwright, spinning rollers, 274 Armatures, 19, 20, 21, 24-25, 26 Atom, construction, 54-55 Autogiro, 238 Automobile, 214-225 engines, 176-178, 179 Aviation, statistics of, 234 B Baldwin, Mathias W., locomo- tives, 193 Balzer, Stephen M., 179, 222, 226 Bell, Alexander Graham, 99-106, 108-109 patent suits, 110 Ben Day process, 374-375 Berliner, Emile, 1og—-110 Bessemer, Sir Henry, process, 342-345 Blast furnace, 340-341 Brakes, train, 195 air, 196-198 Bright, Sir Charles, 92, 94, 96 Byrd, Admiral Richard Evelyn, 232 Cable, Atlantic, 92-97 ocean, 89-go Carburetor, 178-179 Carnegie, Andrew, 349-352 benefactions, 352 Carnot, Nicholas Leonard Sadi, Hy) cycle, 157-158 Chinese silk weaving, 275-276, 280-281 Cierva, Juan de la, 238 Clermont, America’s first success- ful steamboat, 187 Coal and coke, use in reducing ore, 38 Coal, oil, and water power, 150 Coal, thermal value, 159 Collotype engraving, 373 Commutators, 18-20, 24, 26 Compass, gyroscopic, 190 Compression, in gas engine, 172, 176 Condenser, electric, 90, 98, 118 Conduction, electric, in solids, 56 in gases, 49 [ 377 ] INDEX Coolidge, W. D., 145 X-ray tube, 68 Cooper Hewitt, mercury arc, 70 mercury-arc rectifier, 70 Corliss, George H., 163-165 valve mechanism, 164 Corning Glass Works, 335 Cotton gin, 301-302 Couplings, train, 198-200 Crompton, mule spinner, 275 Crystal oscillators, 127 Curie, Professor and Madame, 54 Current, alternating, 23, 32, 35 direct, 23-24 polyphase, 32 thermionic, 60, 61-63 three-phase, 26, 41 Curtiss, Glenn, 227, 232 Cycle, Carnot’s, 157 Otto four-stroke, 172 D Daguerre, Jacques Mandé, 358 Daguerrotypes, 358-359 Daimler, Gottleib, 215 Davy, Sir Humphrey, 1, 3-4 Day, Arthur L., 326 De Forest, Lee, audion, 60, 64, 133 De Laval, Gustav, 168 turbine, 168 Diesel, Rudolph, engine and cycle, 175 Discharge, oscillatory, of Leyden jar, 78 Drawboy, 285, 287-288 mechanical, 287, 288-290 Direr, Albrecht, 354 Duryea, Charles E., 216-219 Dynamo, 18-42 alternating, 37-42 direct-current, 24 early development of, 18-24 Faraday’s, 14 theory of, 21-24 E Eastman, George, 361-365 Edison, Thomas A., 109, 136-144 and electron tube, 58 early life, 136-138 first central power station, 144 incandescent electric light, 138- 144 bamboo filament, 141-142 paper filament, 139-140 Efficiency, of heat engines, 180 maximum of, 157-159 Egypt, cloth of, 271 Eiffel, Gustave, 232 Electricity, early discoveries in, I-16 from magnetism, I-2, 10-16 Faraday’s dynamo, 14-15 Faraday’s iron ring experi- ment, 10-13 Oersted’s discovery, I, 2 measurement of, 7-10 Faraday’s galvanometer, 9 Zweigger’s galvanometer, 8 Electrolux Company, refrigera- tors, 244 Electromagnets, 72-73 Electron, 51-56 charge, 54, 59 tube, as wave source, 123 Edison’s, 58 Electrotype plates, 367 Emmet, W. L., 158 Engines, internal combustion, 171-180 automobile, 176-178, 179 Diesel, 175 airplane, 177-178, 179, 236 Manly’s airplane, 179, 226 Otto cycle, 172 pioneer, 171-172 radial, 179 single-cylinder, 172-174 [378] INDEX Engines, steam, 159-171 Corliss, 163, 164-165 multiple expansion, 166 simple reciprocating, 162 turbine, 168, 169 impulse, 168-169 reaction, 169-171 Watt, 159-162 Engraving, color, 369-370 half-tone, 368-369 intaglio, 355 photogelatin, 373-374 planographic, 355 relief, 355 steel, 354-355 wood, 353-354 Ericsson, John, 188 F Faraday, Michael, 1, 4-5, 37, 86 dynamo, 13-15 galvanometer, 9 iron ring experiment, 10-13 Field, Cyrus W., 91-92, 96 Films, bichromatized, 366-367, gf? photographic, 360, 363 Fitch, John, steamboats, 181-183 Ford, Henry, 215, 222-224 Fulton, Robert, steamboats, 185- 188 Furnace, blast, 340-341 electric, 348 reverberatory, 346 G Galvanometer, Faraday’s, g Zweigger’s, 8 Gas, producer, 346-347 Gases and refrigeration, 239-242, 243-247 General Electric Company, 31, 41, 475 595 61, 65, 145-146 refrigerators, 245-247 Generators, three-phase, 26, 41-42 Gibbs, James, 260 sewing machine, 260-261 Glass, composition, 323-325 history, 322 manufacture, 324-325, 334-336 optical, for World War, 325-334 homogeneity, 332 manufacture, 329-331 qualities, 329 varieties, 331 uses of, 311 Goodyear, Charles, 317 experiments on rubber, 318-319 patent suit, vs. Day, 319 Gray, Elisha, 102 telephone specifications, 107- 108 Great Eastern, 92, 96, 97 Great Northern system, 204-205, 206 Grid, 60 Grover, William O., 261 and Baker Company, 262-263 sewing machine, 261-262 Gutenberg, Johan, 353 Gyroscopic compass, 190 H Harriman, E. H. 205-206, 207-214 Imperial Valley, saving of, 209- 214 Lucin cut-off, 208 San Francisco relief work, 208 Harvester, 307 Haynes, Elwood G., 219-222 Heat and refrigeration, 240-241 Heaviside layer, 117 Heddle rod, 271-272 Henry, Joseph, 1, 5-7, 10 and Alexander Graham Bell, 100-101 discovery of mutual and self- induction, 74-78 [379] INDEX Henry, electromagnet, 72, 86 oscillatory discharge of Leyden jar; 78,116 telegraphic experiment, 73 Hertz, Heinrich, 128 Heterodyning, 126-127 Hill, James J., 201-207 and Great Northern, 203-205 and Northern Pacific, 205-206 Hot-wire emission, 59, 60 Howe, Elias, 250-255 patent suits, 257, 262, 263 sewing machine, 251, 252-254, 255, 257 Hubbard, Gardiner G., 100, 103, 108 Hunt, Walter, 248-250 inventions, 249 sewing machine, 249-250 Hussey, Obed, reaper, 305, 306 I Imperial Valley, saving of, 209- 214 Induction, mutual and self-, 74- 78, 98, 116, 119 Insulation, 72 Ionization, 59-60 Iron, composition, 337, 342 manufacture, 338, 341 ores, 337-338 reduction, 338-339 Ives, Frederic E., 368, 369 J Jacquard, Joseph Marie, 290 Jacquard machine, 286-298 advantage of, 297 description, 291-297 Janney, Eli H., coupler, 199-200 Jervis, John B., swivel truck, 193 Jewett, F. B., 113 K Kelvin, Lord (Sir William Thom- son), 91, 95, 99, 108, 128, 158 Kleitsch, Karl, 371 Kodak, 364 L Langley, Samuel P., 225 airplane experiments, 225-226, 92%, gold medal, 232 laboratory, 234, 236 Langmuir, Irving, and electron tube, 59, 61-62, 63-64 and gas filled lamps, 147 Levassor, automobile, 215 Leyden jar, 90 oscillatory discharge of, 78, 116 Light, electric, 135-148 arc, 135, 147-148 incandescent, 138, 142, 145 Edison’s, 139-143 Swan’s, 135-136 Lighting, incandescent, 35-36 Lilienthal, Otto, 225 Lindbergh, Col. Charles A., 232, 238 Lithography, 355 Locomotive, 192-195 Loom, 265, 266, 269, 277, 278 draw, 282-286 Indian, 276-277 modern, 277-280 power-driven, 299-300 primitive, 265-272 Egyptian, 271 European, 269-270 simplest, 266-267 tapestry, 272 Lucin cut-off, 208 M Machinery and society, 149-150 Magnetic lines of force, 20-23 Magnetism from electricity, 10, 12 [ 380 ] INDEX Manly, Charles M., 226, 227, 232 airplane engine, 179, 226 Marconi, Guglielmo, 129-133, 134 Marsh harvester, 306-307 Maxwell, J. Clerk, 20-21, 128 McCormick, Cyrus H., and Com- pany, 305-306 reaper, 303-305, 306 Millikan, R. A., 54 Morgan, J. Pierpont, 205, 206 Morse, Samuel F. B., 80, 92 code, 82 patent suit, 82-83 telegraph, 80-85 Moseley, H. G.-J., 55 Motor, repulsion, 28-30 Motors, alternating, 44-46 direct-current, 42-44 synchronous, 46 N National Advisory Committee for Aeronautics, 232-236 Navigation, aids to, IgI-192 Niagara Falls, power, 36 power plants, 153-155 Niepce, Joseph N., 357, 358 O Oersted, Hans Christian, 1-2, 86 Open-hearth steel making, 346-348 Osborne, J. W., 370 Otto, N. A., 175 cycle, 172 P Paper, manufacture, 312-315 uses of, 309 Parsons, Sir Charles A., 169 reaction steam turbine, 170, 17! Patent suits, Bell patents, 110 Goodyear vs. Day, 319 Howe vs. Singer, 262 Patent suits, Langmuir vs. De Forest, 64-65 O’Reilly vs. Morse, 82-83 Pelton wheel, 151 Photoengraving, 366-370 Photography, 356-366 discovery and development of, 356-360 daguerrotypes, 358-359 dry-plate, 360, 362 film, 363-364 instantaneous, 359 Photogravure, 371-373 Photolithography, 370-371 Pixii, dynamo, 18 Power, heat, 155-159 use of, in America, 48, 150 water, 151-155 Propeller, screw, 188-189 Proton, 54-55 Pupin, Michael I., “loaded line,” III R Radiation, electromagnetic, 110- III wonders of, 113 Radio, antenna, 118-119 foundations of, 121-122, 128- 129 recent progress of, 133-134 telegraph, 120-121 telephone, 123-126 tuning, 119-120 waves, 114-118 Radiobeacons, 134 Radium, 54 Randolph, Epes, 211 Reactance and resistance, 119-120 Reaper, 302-306 Rectifier, vacuum-tube, 68-69 mercury-arc, 69-70 Refrigeration, 239-247 commercial, 242-244 principles of, 239-241 [ 381 | INDEX Refrigerators, absorption type, 244-245 compression type, 245-247 domestic mechanical, 244-247 Regeneration, principle of, 123- 124 Relay, telegraphic, 82 Resonance, electric, 119 Rontgen, W. C., 65 X rays, 65-68 Roosevelt, Theodore, 207, 212, a1 Rosse, Lord, telescope, 169 Rotogravure, 371-372 Rubber, 315-322 manufacture, 316-317, 319-321 magnitude of, 319, 321-322 sources, 315-316, 319 uses of, 310-311, 317 vulcanization, 318-319, 321 Rutherford, Lord, 49 S Salton sink, 209 San Francisco earthquake and fire, 208 Selden, George B., 216 Senefelder, Alois, inventor of lithography, 355 Separator, cream, 31 Sewing machine, 247-265 essentials of, 264-265 trust, 263 Ships, clipper, 188 iron, 189 Siemens, Sir William, 342, 346 Silk thread, 267, 276 weaving, 278, 279, 280-281, 282 Silver salts, light action on, 357 Singer, Isaac M., 256 sewing machine, 256-257, 258 Sleeping-car, 351 Smith, Donald (Lord Strathcona), 202 Space charge, 59, 63 Spindle, 268-269, 272, 273, 274, 275 Spinning, 265, 268-269, 272-275 Stanley, William, 34, 35 Steamboat, 181-192 Steam boilers, 157 engines, 159-171 properties of, 155 Steel, 336-352 composition, 337, 342 manufacture, 342-348 Bessemer process, 342-345 open-hearth process, 346-348 uses of, 311-312 Stephen, George (Lord Mount Stephen), 202 Stevens, John, steamboats, 183- 185 Swan, Sir Joseph, 135-136 Af Talbot, William Henry Fox, 358, 359 Telegraph, 73-74 first commercial, 78-89 Morse’s, 80-85 Wheatstone’s, 78-80 printing, 88-go wireless, 120-121 Telegraphy, duplex and multiplex, 87-88, 138 Telephone, 99-112 wireless, 115, 123-126, 134 Tesla, Nikola, 31-32, 35 Thimonnier, Barthelmy, 247-248 Thomson, Elihu, 25-26 discovery of repulsion principle, 28-30 inventions of, 26-28, 30-31 Thomson, J. J., 49 discovery of electron, 51-54 [ 382 ] INDEX Thomson, Sir William (Lord Kelvin), 91, 95, 99, 108, 128, 158 Traction, locomotive 194-195 Transformer, 27, 34, 36, 37-39 Transmission, long distance, 37 wireless, 113 Tungsten, ductile, 146 Tungsten filaments, 145-147 Tuning of electric circuit, 119-120 Turbine, mercury-vapor, Em- met’s, 48 steam, impulse, 168 reaction, 168-171 water, impulse, 151-152, 153 reaction, 152-153 U Union Pacific system, 206, 207, 208 V Vacuum, discharge in, 50-51 Ww Walcott, Charles D., 227, 233 Wallace, William, arc light, 135 Watt, James, steam engine, 159- 162 Wave length, 66, 114 Waves, 114 Waves, carrier, 115 continuous, 122 discontinuous, 117-118 modulated, 115 Weaving, 265, 272, 276-282, 286 early examples of, 265, 267, 269-271 pattern, 280-282, 286 power, 299-300 Webster, Daniel, 319 Welding, electric, 27-28 Westinghouse Electric Company, 35-36 Westinghouse, George, 33-36 air brake, 196-197 Wheatstone, Sir Charles, electric telegraph, 78-80, 86 Whitney, Eli, cotton gin, 301-302 Wilson, Allen B., sewing machine, 258-260 Wood and steel engraving, 353- 356 Woodburytype, 372 Wright, Orville, 225, 230-231, 233 Wright, Wilbur, 225, 228-230 X X rays, 65-68 Z Zweigger, galvanometer, 8 [ 383 ] i ‘ieee . me | “ak A eid mt A, aay . nt ees m a en i a ie hi ‘ion rv ie as i vy | a v Wie a aa 7 eft nite ty A yy i af ue ina ie ie ee ei fh TR PRL 7 mn at . me i a ; wt ry) ; ' nm a aa ' : olen “hs - on | iis ms an a ae ' i Ny i ru a ie one By ae vie br “ay ae ih ite ay yi i: yr, ‘ ve Wi: - a ms Hh iv 7 fl i “ ‘ ve ‘ur oy Mey} ui en ne ih ee if , 7 A “ on 1" j Pe TaN i ; } a 7 my D ie ee oe ) ; Pt 0 ee hay a Hy i bial ro ; : i ri ane Me a ih maar rey ee s', Shane ih ; 90rt i ; i Teen ae. 2 hi: Hy oa A : ca 2, : et cara i H ; - 1X a7 rey | ay rt ae nie 7 ile " ay, is a ay i, ao ey i - os A Ti fe q aad -' vine Le ‘) i Lae iY . 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