GEORGE FORBES: CARBON BRUSH INVENTORFrederick W. Duthie

Morganite Incorporated, Dunn, NC 28334

INTRODUCTIONThe year of 1985 was particularly significant in that it was

the 100th anniversary of two major inventions. In 1885 Gott-lieb Daimier and Karl Benz separately produced vehicles dri-ven by gasoline internal combustion engines. In the sameyear, the first patent on the application of carbon as a currentcollector for rotating electrical machines was granted toGeorge Forbes.

George Forbes received very little publicity and minimal fi-nancial reward for this epoch making innovation. The carbonbrush was only one of his many significant contributions tophysics and education. Forbes had no interest in commercial-izing his ideas and unfortunately did nothing to record hislife's work for posterity, preferring instead to preserve thewritings and books of his father.

This paper attempts to re-create "flesh on the bones" ofGeorge Forbes, review historical developments in brush de-sign and materials, and offer suggestions to motor manufac-turers and users to enhance brush life. Professor George Forbes

In researching Forbes, the writer uncovered a great deal of M.A., Hon. LL.D., F.R.S., F.R.S.E., F.R.A.S., M. Inst.information not previously brought together. For the sake of C.E., M.I.E.E.; Russian Order of St. George;posterity, the author has written more than originally antici- French Legion of Honourpated regarding Forbes; however, in the manner of Forbes,the author will make no apology in the anniversary year.

George Forbes, The Man. What was Forbes like as a per-GEORGE FORBES son? Judging from the following, he was at least a very color-

George Forbes was born in Edinburgh, Scotland, April 5 ful individual.Writing about Forbes, William Gfimson, Senior Fellow of1849. The lineage of both his distinguished parents was that Christ's College, Cambridge, mentions, "Mr. Forbes is aof ancient Scottish races. He was one of five children of gentleman in mind and manners with abundant energy andJames David Forbes, D.C.L., LL.D, F.R.S., Principal of St. zeal, and a decided love for his favorite studies" [4].Andrew's University, who was himself famous for his geolog- Professor P.G. Tait writes, ". . . highly conscientious andical research, particularly his theory on glaciers. His grand- having a strong sense of duty . . ."[5]father was Sir William Forbes, a close friend of Sir Walter According to Sam Mavor, "George Forbes, the best type ofScott and Samuel Johnson [1, 2]. Scottish gentleman, of tall and handsome appearance, splen-

George Forbes was educated at Edinburgh Academy did physique and athletic bearing, had a singularly attractive(twelve years after Maxwell and Tait), St. Andrew's and personality, fine character, a brilliant intellect and the mannersCambridge Universities [Il. of a courtier. His versatile abilities distinguished him as engi-

Forbes was elected a member of "The Institution of Electri- neer, inventor, astronomer, traveller and philosopher, and thecal Engineers" in 1881, a member of Council from 1891- breadth of his knowledge and experience and gift of conversa-1893, and Vice President from 1894-1895 [3]. tion made him a delightful companion" [6].

Forbes, however, was probably somewhat unpopular with

This paper in expanded forn with the title *-Long Life Brushes-100 Years," Americans who read his writing in Blackwood's Magazine:appeared in the Proceedings of the 1985 Coil Winding Meeting of ICWA. "There are two great mistakes commonly made as to Ameri-0885-8985/86/0400-0002 $1.00 © 1986 IEEE cans. One is, that they are original inventors; the other is, that

2 IEEE AES Magazine. April 1986

they are humorous. Neither of these propostions is true . . ." rather pathetic old gentleman, who lived in a fabulous abodeTo explain this apparent paradox, he goes on to interpret the called the "Shed" in Pitlochry when not with us" [10].difference between designing and inventing: "Invention and Forbes was staying with the Stockdales when he deliveredhumour require a gift of imagination, the same gift that shows the David Elder Lectures on Astronomy [6].itself in poetry and letters, in music, painting, and sculpture; In the late seventies, he was suffering from loss of memoryand in no one of these directions has this gift of imagination and failing sight. Forbes had to undergo an expensive opera-been found to predominate largely amongst Americans." He tion to remove an eye [11].continues to "charm" American readers, ". . . in that coun- Forbes, in his later years, went through a period of finan-try the manners and customs, as seen by the ordinary travel- cial hardship. "He should have made a lot of money in hisler, are governed by the average man, who is not a good time, especially in consultancy work. But he was relativelyspecimen. He is apt to be the most awful "bounder," has no poor" [9]. "George Forbes thought much of his work and lit-taste, and does not know the meaning of the word "repose"; tle of his reward. When he ceased to read because his eyesbut you need never meet this type except in railway trains and grew dim, piety and honour forbade him to sell his father'shotels. But the refined American is quite different, and quite books, and he gave them all to St. Andrew's University.like an English gentleman. These are mostly met in Washing- These books, some four thousand in number, are of greatton and the South. An Englishman in America should always value . . . The sale of these books would have brought himtry to retain his Englishness-otherwise in a year or two he comfort, almost wealth, but money had no place in hiswill be reduced to the level of an average American. Where thoughts" [1]. In 1928, his friend and colleague, D'Arsyall men think themselves equal, individuality is at a pre- Thompson, successfully petitioned the government, organiza-mium" [7]. tions and associates for financial assistance to rescue Forbes

In 1882-1890, we find that Forbes had a residence in Lon- from his plight. At this time, Forbes resided at 11 Littledon at 34 Great George Street, Westminster. During this pe- College Street in Westminster, London, and was thus able toriod, he was working with private industry. spend time at his club-the Athenaeum.

In 1906, Forbes built, largely by his own efforts, a home In about 1934, Forbes moved to a small hotel at 13,near Pitlochry, in Scotland, to house the books and memora- New-parade, Worthing. His health had been deteriorating.bilia of his father, who died in 1868. Forbes liked to call his Jean Stockdale would have been interested to know that thehouse "The Shed," a large wooden structure which had an fur coat her mother detested had stood the test of time andobservatory on the upper story overlooking Loch Faskally and was still being worn by Forbes. During his time in Worthing,the hydro-electric scheme which he had first proposed in the he employed William Earnest Kirby as companion attendantearly 1900's. It was felt that reference to his home as a shed [12].was to emphasize his relative poverty. "Fell in Front of Fire/Burns Accelerate Death" is the col-

At the age of 61, Forbes boards a tramp steamer, the S.S. umn heading of The Worthing Gazette on the inquest of hisHasland, in Cardiff. While in the Gulf of Lyons, very rough death on October 22, 1936. The verdict was death by misad-weather is experienced and the ship is foundering when venture. The primary cause of death was bronchial catarrhForbes considers what items he should save. "Tobacco was and laryngitis, accelerated by the shock of burning. Forbesthe first necessity: it supplies the place of food, drink, had been sitting close to a gas fire when he appears to havewarmth, dry clothing, and sleep" [8].Amongst other items slipped off the chair. He was unable to pull himself up, andsaved are a fur coat and a fur rug-these may be the very consequently one leg was burned. He died early next morn-ones mentioned later in this paper! Exactly why Forbes made ing. The funeral took place at Durrington Cemetery, the serv-the trip to the Mediterranean is not clear. ice being conducted by the Vicar of St. Andrew's (the Rev.

Dr. John A. Cranston writes that Forbes was "very individ- W. Fowell Swann) [12].ualistic and tetchy." He was a confirmed Tory. In an election Forbes never married-in fact, there appears to be no refer-in the early twenties, Dr. Cranston asked Forbes whether he ence to an association with anyone of the opposite sex. Thishad voted. "Voted! Even the Tories are all damn Socialists" is perhaps surprising since it was stated at the inquest that[9]. "he always wanted somebody about him as he dreaded being

Jean Stockdale, daughter of a past director of the Univer- alone" [11].sity of Strathclyde, gives her opinion of Forbes in notes enti-tled "Professor George Forbes as he Appeared to a School- PROFESSOR GEORGE FORBESgirl." Forbes, at the time, was in his early seventies. "He SCIENTIFIC ACHIEVEMENTS & EXPLOITSappeared to me as a tall, thin, aristocratic old gentleman, who After graduating, Forbes, at the age of twenty-four, was ap-could look straight through you. He used to wear tailored silk Afted g r of at Phe at Anden 's ap-shirts with soft collars and loose woven, rather light colored pointed Professor of Natural Philosophy at Anderson's Uni-tweeds of ancient vintage. I have a strong suspicion, that if it versity (subsequently known as the Royal Technical Collegehad not been for the attention of my mother's darning needle, and now as the University of Strathclyde) in Glasgow. Duringhis needs would have seen the light of day! He liked at least hls eight years' association with Anderson's College, he trav-three pairs of blankets on his bed, over which he placed a elled extensively.large fur rug, rather moth eaten and pock marked with to- The Transit of Venus. It was in 1874 that Forbes set out tobacco burns as he would smoke in bed. He also wore a long lead a team of scientists in a mail steamer to Valparaiso,fur coat in similar state, which nearly reached his heels and thence by HMS Scout to Hawaii. The objective was to spendwhich my mother would dearly have loved to send to the six months studying the transit of Venus to determine the so-cleaners! We were to understand that coat and rug had been lar parallax and distance [1,13]. The next transits will be Junepresented to him by some Russian, I think, aristocrat and 8, 2004 and June 6, 2012.were the last word, which neither age, moth nor lighted to- On the morning of Friday, November 20, Forbes and abacco could alter. These are a few of my memories of Prof. Mr. Lambert were swimming off Kailua. Lambert got intoGeorge Forbes whom we came to look upon as a eccentric, difficulties when high waves and a strong undercurrent devel-

IEEE AES Magazine, April 1986 3

oped. It is recorded that Forbes made noble, but unsuccessful, conform himself to the established rules. Tiflis, June 5-17,efforts to save his friend, coming very close to losing his own 1877."life in the process [6,141. Forbes actually becomes involved in the conflict. For his

Journey through China and Russia. Instead of retumning leadership and numerous acts of bravery, he is awarded the

home after his successful observation in Hawaii, Forbes Russian Order of St. George and several gifts [16].writes, "My work there was finished in six months and I was Velocity of Light. Back home in Scotland, Professor Georgemeditating about my journey home by India or North America Forbes resumes with Dr. J. Young, F.R.S., research on thewhen I was told it might be possible to go by Siberia from velocity of light based on a modification of Fizeau's method.Peking. I happened at the time to be unhampered by consider- Their work, concluded in 1880, established a figure ofations of time and money, and as I should have less chance 301,382 km/sec [1]. (Author's note: This is very close to theafterwards of travelling by this route than by the others I de- currentfigure of 299,792 kmlsec.)termined to try it, and my ignorance of the countries and their Astronomy. This was one of Forbes' favorite fields, nolanguages made me the more anxious to try." Thus began an doubt from the influence of his father. In 1880, Forbes pre-adventure that few men would have undertaken. His trip in dicted the existence of a trans-Neptunian planet (Pluto) from1875 by foot, camel, tarantass, and boat, through China, evidence relating to families of comets attached to planetsMongolia, and Russia is on record. From Shanghai, he then [17,181.travelled to Peking, Changkiakow, Ulan Bator, Kyakhta,Irkutsk, Krasnoyarsk, Tomsk, Perm, Kazan to Moscow and Electric Traction. During his time at Anderson's College,Leningrad and thence to Scotland-a journey of four months Professor Forbes advocated in his lectures the use of electricand some 5,000 miles. traction. In 1879, Forbes commissioned to report on how the

While in Kyakhta, on the Mongolian/Siberian border, City and South London Railway should be powered. Forbeswhere few foreigners ever set foot, he is introduced to a girl recommended electrification. The London Underground (tube)of 17 years from an old Scottish family. Miss Campbell asks might have been operated by cables had it not been for theForbes to assist her return to Scotland, to which he agrees. suggestions of Prof. Forbes I19,311.They travel together to Irkutsk (close to Lake Baikal) wherethey become associated with some exiles from the Polish rev- Industry Manager. In 1882, George Forbes joined the pri-olution of 1863. Miss Campbell falls in love with a Josef vate sector for the first time and moved to London.Szlenker, but the government prohibits the wedding unless she He was appointed manager of the British Electric Lightpromises never to try to escape from Russia. The promise was Company, producers of carbon filament and arc lamps. Whilegiven and the ceremony took place in the Roman Catholic working with this finm, he made improvements to arc lampschurch in Irkutsk. Forbes travels home alone with some mis- and invented a meter for alternating current measurement. Ingivings about leaving the couple behind. While in Leningrad, 1883 and 1884, Forbes was granted patents 3115 and 11244he attempts audience with the Tsar to plead for the release of respectively, on "Dynamo Electric Machines." In 1884, hethe couple but is not successful. Having previously met the exhibited a unit of his own design at the Philadelphia Electri-Duke of Coburg (was the Duke of Edinburgh until he married cal Exhibition.the only daughter of the Tsar), Forbes wrote to him and was It is probable that his involvement with carbon productsthis time successful in obtaining the Szlenkers' release [151. and dynamo development with this firm led in 1885 to patent

WAR NEWS IN 1877-WITH THE RUSSIANS. The :preceding is the heading in The Times of February 21, 1930.In 1877, George Forbes was in Germany when war broke out -between Russia and Turkey. "On the declaration of war mylove of adventure determined me to act as war correspondentwith one of the two armies for some London newspaper. Ihurried home from Germany and wrote to editors direct, as I 4|l ihad no journalistic friends who could use any influence."

Forbes received an interview with Delane, the great editorof The Times, and eventually is assigned as the only Britishwar correspondent with the Russian army in Asia.He writes, "I spent one night in Warsaw with the two

Siberian exiles whose freedom I had secured a year or twobefore. They gave me a letter of introduction to a General atthe front." No problems were encountered until the town ofTiflis (now know as Tbilisi) is reached when a delay of nearlysix weeks is encountered. The Russians had suspected Forbesof being a spy. In desperation, Forbes contacts Prince Swiati-polk Miski who asks if he is related to Principal James DavidForbes. When Forbes reveals that this was his father, thePrince is elated, for he had much admired the father's contri-butions to science. Within two days, Forbes receives a letter:"The Prince Swiatipolk Miski has the honour to inform Mr.Forbes that his highness the Grand Duke, General-in-Chief of Elthe army of the Caucasus, has been pleased to grant him per- - -:.mission to the camp of the Russian troops, either before Kars Forbes' Patent #1288or in the Kobaulete. It is understood that Mr. Forbes must

4 IEEE AES Magazine, April 1986

#1288, "Improved Means for Establishing Electric Connec- Other Hydroelectric Projects. During his term with thetion between Surfaces in Relative Motion Applicable to the Niagara project, Forbes was involved in 1893 in an advisoryCollectors of Dynamo Machines." This was the first patent on capacity to the Indian government on the utilization of thethe use of the carbon brush. G.L. Addenbrooke writes, "He power rendered available by the Peryar Irrigation Works in thealways referred to this work with much modesty, buy there Madras Presidency [13].can be no doubt that almost without acknowledgement he pre- Forbes supports Sir William Thomson's proposal to harnesssented to the world an idea of great engineering and commer- tidal energy for conversion to electrical power [24].cial value, the importance of which he does not seem to have Forbes now appears to have earned himself an excellentfully grasped at the time" [20]. reputation as a consulting engineer. We find him making sur-

Harness."In October 1889, the Niagara Falls veys with a view to hydroelectric power conversion in SouthHawernessiangNagara. Africa in 1895, at the Huka Falls in New Zealand in 1896,Power Cm any was or to carriu thegratworko and at the cataracts of the Nile in the years 1897 and 1898. It

utilsin thNigarFals n s giantc ascae tat ll re-was Forbes who suggested to Lord Kitchener the use of elec-vious attempts to use water power at once sank into insignifi- tri loc oes o thegrilwath was beng tructcance" [7]. A panel was established of engineers and physi- acr otheNuinDe rom Wad Ha tonAbuHaedcists from the UK, France, Switzerland, and America, with hacross the Nuban Desert from Wadi Halfa to Abu Hamed for

Lord Kelvin as chairman. Forbes was invited to join the panel ithe campatgn aganst the Khallfa. At the same time he was

and, at first, refused. When he considered that all designs waystoelestnc ityof31].

tendered would not be satisfactory, he accepted the challenge. ways by electricity [19,31].Several significant contributions were made by Forbes during Electricity as a Motive Power. As mentioned elsewhere,the period 1891-1895 when he was consulting electrical engi- Forbes proposed electrically powered trains. One of the mainneer on the project. In the design of the generating equip- attractions, according to Forbes, was the application of a mo-ment, he eliminated the need for a flywheel, and thus reduced tor to every wheel of a train. Such an arrangement would al-the stress on the supporting bearings. Locating the rotational low greater acceleration (particularly important with closepart of the equipment on the outside was a total reversal of proximity stations), greater traction on uphill grades, lessdesign practice until that time. The final design was a com- wear and tear on tracks, better stability on curves, and wouldpromise between his ideas and those of Westinghouse, who be economically feasible. Of passing interest is Forbes' com-built the generating equipment. ments on the use of batteries to power tram-cars (street cars),

Forbes, against most opinions at that time, advocated high boats, or tricycles. "I think that it would be far more eco-voltage alternating current, instead of direct current, for long nomical to use compressed air engines. Ever since 1865,distance power transmission. His absolute determination that when I examined the compressed air tram-car of Scott Mon-he was right on this and on other matters of policy, despite all crieff, which ran so successfully in Glasgow, I have felt sureobstacles, had a great deal to do with the success of the that this must become eventually the motive power for tram-scheme [7]. cars, and I have not yet seen any thing to lead me to alter my

Forbes, lecturing in 1893, stated, "All direct current dyna- opinion" [24].mos except the unipolar ones are the combination of an alter- Range Finders. Professor Forbes, in 1901, invented an in-nator and a commutator, and every advocate of the continuous fantry range finder. During the South African War, Forbes vis-current that there ever has been, and there are bigoted advo- -ited South Africa in 1902 to perfect the instrument [6]. Prof.cates, would have been convinced in favor of the alterating Forbes also devised a formula whereby the range table of acurrent dynamo, alternating current and transmission, if youcould have told him that you would put a commutator at the untcaniber c e th gfar end of the line instead of at the place where you generated different caliber [20].your current" [21]. Naval Projects. In 1903-1906, Forbes was engaged by theThe plant was designed to have a total capacity of British Admiralty to develop a gunsight range finder for the

100,000 hp. Each of the alternators supplied 2,250 volts, two navy [1].phase at 50 Hz. The directly coupled turbines, built by the "During World War I, he invented a method of signallingI. P. Morris Co., rotated at 250 r/min. between submarines utilizing the principle of converging

Reflecting on the project, Forbes writes, "In conclusion, it beams of light. The admiralty also placed a cruiser at his dis-is difficult for me to say who were the boldest, the capitalists posal to enable him to carry out trials on the scraping of bar-who embarked on the scheme before any plans were matured, nacles from the bottom of ships to save the necessity of com-or the manufacturers who moved their factories to this field ing into dry dock. He subsequently applied to patent this andbefore a single result had been achieved. The action of both found to his annoyance that a patent already existed whichwas typically American, but their confidence was not mis- had been taken out by the captain of the naval cruiser" [9].placed. Their success is now assured" [22].The project was not without some controversy. Ferranti al- CARBON BRUSH DEVELOPMENTS

leges that Forbes' design of alternator incorporated features ofa design submitted by C. E. L. Brown. Brown (subsequently Early Current Collectors. Michael Faraday in 1832 usedformed Brown-Boveri) himself did not make this claim, but copper rods wetted with mercury for the conveyance of cur-was critical of the low generated frequency, that the external rent to a rotating disc. Mercury alone in the form of "pools"rotating field gave poor ventilation and that the armature was was used by several inventors including Forbes. Laminatedtoo inaccessible [23]. copper or brass foil was also frequently employed. In 1870,

Professor George Forbes felt that he deserved a knighthood Z. T. Gramme employed collectors comprised of a bunch offor his work on the Niagara project. In December 1894, he wires, which, when worn, took on the appearance of a shav-wrote to the person he thought would do him most good- ing brush. In 1884, 0. Schulze patented metal gauze brushes.Lord Playfair [13]. Unfortunately for Forbes, there was to be All of the above suffered from a major disadvantage: exces-no recognition in the form for which he had hoped. sive wear of the current collecting components. Various lubri-

IEEE AES Magazine, April 1986 5

cants, including graphite, were employed. It is understood no single thing has had a greater or more direct influencethat some of the collectors made from laminating copper were upon the technical success of railway machinery than the in-coated with lampblack, possibly by holding them over a burn- troduction of the carbon brush as a substitute for the variousing candle. forms of metal brush, many forms of which had been tried

previously on railway motor commutators but without evenThe First Carbon Brushes. The original carbon brushes did the beginning of success. Simple as this substitution was, the

not look at all like those we are familiar with today. The ac- results are of the greatest importance. The pioneers in electrictual brushes employed by Forbes had, until recently, been railway work had been struggling with the many problemsstored in a handmade soldered tin container, with pull-off lid. presented, not the least of which was to get a motor commu-On the outside of the box was affixed a label, the wording on tator to run under varying loads without spark, to run in eitherwhich had badly faded. By means of ultraviolet light, the cur- direction without trouble, and without need of changing thesive script read, "The first Carbon brushes / used for dynamo lead, and above all to endure for a reasonable time.electric / services. These ones supplied to the Forbes / "All forms of metal brush had been tried and become ac-

......... . . . er dynamo." The dots indicate indecipherable knowledged failures. They were only calculated, under theletters [251. It is possible that the missing word is "homo harsh conditions, to be ground and to grind the commutatorpolar." into dust at a rapid rate (such dust being scattered by the

pound along the line of way), with the production, at thesame time, of a flickering greenish illumination under the car,an illumination all the more ghastly on account of the havocknown to be going on and of which it was an unfailing index.It is not too much to say that before the carbon brush wassubstituted there was in prospect inevitable failure; disasternot unforeseen, but all to evident.

"But how did it come about? I do not know that the cir-cumstances have ever been detailed in print, and it shall bemy present purpose to fill this gap in the history of electricrailways and, at the same time, to pay tribute to the memory

liT t| hi, ama a T l~ w of Mr. Chas. J. Van Depoele, truly a pioneer in this art and tom0X}t A .: 8 t \: 0 t L t4 + 4 whom was due the suggestion of the use of carbon as a brush

for railway motors."

Forbes' Brushes

A detailed examination of the brushes has been conductedby Morganite researchers [26]. The actual collector, madefrom retort carbon, was comparatively thin. According to Pat-ent #1288, it was Forbes' intention that the carbon portion beas thin as possible to reduce the resistance of the contact,while strengthening the "plates" by attaching them to a cop-per backing. The carbon was copper plated and soldered tothe metal backing. Initially, the carbon was produced frombattery plates or arc lighting electrodes. In the case of non-polar dynamos, Forbes engaged the copper backing in slots in MR

the stator and applied spring pressure to the center at a reac-tion angle to the direction of rotation of the disc. The purposeof the blind hole in the backing is not absolutely clear. In onebrush, there remained traces of what may have been braidedcopper conductors. It is concluded that the holes may havehad alternative functions: to align the spring or to provide awell into which a connection was soldered.

Commercialization of the Carbon Brush. Forbes tried to in- Charles J. Van Depoeleterest a British firm to employ the brush in their electrical ma-chines. After three months of experimenting, the company"acknowledged their great merit, but never thought of tryingtoinrdc thmfrgnrlus_21 "It came about this way. We had been trying to use on the

to introduce them for general use . . . " [27]. first roads installed by the Thomson-Houston Co. (Author'sForbes sold his American rights to the patent for a mere

2,000 pounds sterling (at that time equal to $8,000) to West- note: now GE) in 1888, various forms of copper and otheringhouse [271. Forbes no longer appears to be associated with metal brushes, all of which, however, had soon been con-

the carbon brush, either in product development or commer- demned as either quite worthless for the purpose or so nearlycialization. No mention has been found of any royalties being worthless as practically to be so. A discussion of the matter

paid by any UK manufacturers. between Mr. Van Depoele and myself, attended as it was bymany expressions of misgiving as to the fate of electric rail-

The First Application of the Carbon Brush. The first com- way work unless a radical change for the better could soon bemercial application of the carbon brush occurred in 1888. The made in the commutators, led him to remark in substance: 'Istory is best told by Elihu Thomson: "It is, I think, true that have used a plate of carbon as a brush, on a stationary motor,

6 IEEE AES Magazine, April 1986

which carbon brush worked well, and I think it might answer Peter Mitchell, Nobrac Carbon Ltd., UK.the purpose here.' My colleagues at Morganite Incorporated.

"The trial was made and was at once so eminently success- Charles G. Wood, MA, M.Litt, FLA, of Doune, Scotland,ful that scarcely any time elapsed before the metal brush be- formerly University Librarian, the University of Strathclyde.came a thing of the past, not only on the Thomson-Houston James S. McGrath, MA, DAA, University of Strathclyde,railway motor apparatus, but on others also as soon as the Glasgow, Scotland.news got abroad. We called the new brushes "carbonbrushes," though of course they have very little of the brush Dr. George Wise, General Electric Co.

prpr bu te. Charles Ruch, Westinghouse Electric Corp.proper about them.D"I remember inspecting one of the first carbon brushes ap-plied in railway work to a motor commutator after it had hada reputed run of 5,000 miles. It had only worn down to a REFERENCESmoderate extent and the commutator retained its smooth blackpolish. Then it was that we knew that the difficulty, at one 1. Obituary Notices of Fellows of the Royal Society, Vol. 2, pp. 283-286:time so serious and exasperating, had been removed and ourreputations as skilful electrical engineers saved for the time." 2. Dictionary of National Biography, Vol. 19: 1889Thomson continues: "The first proposal to use carbon as a 3. The Institution of Electrical Engineers, letter to Albert E.S. White:

current collecting brush for dynamos was made by Prof. June 5, 1985.George Forbes, in a British patent of 1883" [28]. (Author's 4. Testimonial by William Grimson in G. Forbes' papers at St. Andrew'snote: The year was in fact 1885.) University: Aug./Sept. 1872.The preceding article, written six years after the fact, men- 5. Testimonial by Prof. P.G. Tait in G. Forbes' papers at St. Andrew's Uni-

tions that Van Depoele had previously tried carbon for a brush versity: Aug./Sept. 1872.with successful results. Thomson does not appear to challenge 6. Sam Mavor, Memories of People and Places, University of Strathclyde,the originating source of the carbon brush, nor explains why M201/18, pp. 61-68.Van Depoele delayed suggesting that carbon be tried! 7. G. Forbes, "Harnessing Niagara," Blackwood's Magazine, Sept. 1895

According to Holm [29], A. L. Rohrer, an engineer with 8. George Forbes, F.R.S., "Shipwrecked," Blackwood's Magazine, pp.the Thomson-Houston Co., had made written notices to the 322-343, Sept. 1895.effect that between 1881 and 1885 Van Depoele had unsuc- 9. Conversation with Dr. John A. Cranston, University of Strathclyde:cessfully experimented with carbon as a brush material. This June 15, 1967.reference contradicts Thomson! 10. Jean Stockdale, "Professor George Forbes as He Appeared to a School-To add further to the controversy, another reference states: girl," University of Strathclyde, Feb. 1968.

"The patent itself did not seem to possess much value, for we 11. Trotter correspondence, MSS 19709-19734, St. Andrew's University.soon find the carbon brush being used freely by others, nota- 12. Worthing Gazette, Oct. 28, 1936.bly by Sprague in 1887 for his railway motors for the Rich- 13. G. Forbes' letter to Lord Playfair, KCB, Dec. 3, 1894.mond trolley installation" [30]. If this information was cor-rect, it would give Sprague, not Van Depoele, credit for the 14. "Transit of Venus Expedition," Extract of Mr. Forbes' Journal, Nov. 20,first practical application of the carbon brush! Sprague was re-sponsible for the very first complete system of electric street 15. Forbes' handwritten notes, Box XI No. 12, St. Andrew's University.car, operating in Richmond, VA, in 1878 [31]. 16. The Times, London, Feb. 21 and 22, 1930.

While Forbes can unquestionably claim the first carbon 17. Arthur V. Howard, Dictionary of Scientists, London, Chambers, 1958.brush patent, the credit for successfully implementing the idea 18. Dr. John A. Cranston letter to G. F. of Mar. 1, 1968, M201/17, Univer-is with Van Depoele or Sprague. All were great men, and sity of Strathclyde.who was first is not really that important. 19. The Times, London, Oct. 24, 1936.As E. W. Rice, Jr., President of G.E. Co., stated in his 20. "Obituary Notices," Proceedings Philosophical Society, #49, pp. 698-

address to the Society of Electrical Engineers in 1914, "I 700, 1937.sometimes wonder whether the present generation of electrical 21. International Electrical Congress, Chicago, p. 451: Aug. 21-25, 1893engineers have any conception of the wonderful revolution 22. James E. Brittain, "Tuming Points in American Electrical History,"which was produced in the electrical industry both in design IEEE Press, pp. 126-130.and operation of electrical machinery, by the advent of the 23. James E. Brittain, "Turing Points in American Electrical History,"carbon brush. I have no hesitation in saying that, in my 23. PresE . 129i13c sjudgement, it was the most wonderful and valuable advance IE rs,p.1910judgement,aitwasevermadenthemst wo erfulatond v lc taince 24. Prof. George Forbes, "Electricity as a Motive Power," Van Nostrand'sthat was ever made in the art with relation to commutating Engineering Magazine, #29, pp. 161-172: 1883.machines. There is no other single element of design that 25. Charles G. Wood, MA, M. Litt, FLA, letter to F.W. Duthie of April 3,compares with it in importance . . ." [32]. 1985.

(At this point the author's paper continues with a review of 26. AES. White inter-company letter to F. W. Duthie of May 31, 1985.methods of improving brush life and the factors affectingsame-Ed.) 27. Forbes' letter to Prof. D'Arcy W. Thompson, MSS 19709-19734, St.

Andrew's University.

ACKNOWLEDGEMENTS 28. Elihu Thomson, "How the Carbon Brush Came into Use," The Electri-The author wishes to express appreciation to the following 29. Ragnar Holm, Electrical Contacts Handbook, pp. 398-401:1958.

who have helped immensely in the preparation of this paper: 30. The Journal of the Franklin Institute, Oct. 1926.My wife, Ann, without whose support this paper would not 31. G. Forbes, "Application of Electric Power in Trunk-line Railways," Thehave been written. Engineering Magazine, pp. 1-11, Oct. 1897.Tony Ford, Albert White and Rob Taylor of Morganite Elec- 32. E. W. Rice, Jr., "The Beginning of the Carbon Brush," Extract fromtrical Carbon Ltd., UK. address at MIT: April 29, 1914.

IEEE AES Magazine, April 1986 7