We have here an implied interaction between two magnetic fields, rather a clever idea for a magnetician of the sixteenth century. In one case, the reaction is between the field of the earth and that of the moon, compelling the latter to rotate round its primary once every month; and the second, between the field of the earth and that of the sun, compelling our planet to revolve round the center of our system once every year.
Though an inefficient cause of the annual motion of our planet, this interaction of two magnetic fields had, nevertheless, something in common with the idea of the mutual action of material particles postulated in the Newtonian theory of universal gravitation.
This magnetic assumption by which Gilbert sought to defend the theory of the universe propounded by Copernicus was a very vulnerable point in his astronomical armor which was promptly detected and fiercely assailed by a galaxy of continental writers; all of them churchmen, physicists and astronomers of note. They accepted Gilbert's electric and magnetic discoveries and warmed up to his experimental method; they did not discard his theory of terrestrial magnetism, but rejected and scoffed at the use which he made of it to justify the heliocentric theory. They poked fun at the English philosopher for his magnetic hypothesis of planetary rotation and revolution, and succeeded in discrediting the Copernican doctrine. Error prevailed for a time, but Newton'sPrincipia, published in 1687, gave the Ptolemaic system thecoup de grâce. Gilbert's hypothesis of the interaction of planetary magnetic fields gave way to universal gravitation, and Copernicanism was finally triumphant.
Throughout the pages of Gilbert's treatise, he shows himself remarkably chary in bestowing praise, but surprisingly vigorous in denunciation. St. Thomas is an instance of the former, for it is said that he gets at the nature of the lodestone fairly well; and it is admitted that "with his godlike and perspicacious mind, he would have developed many a point had he been acquainted with magnetic experiments." Taisnier, the Belgian, is an example of the latter, whose plagiarism from Peregrinus wrings from our indignant author such withering words as "May the gods damn all such sham, pilfered, distorted works, which so muddle the minds of students!"
Besides his treatise on the magnet, Gilbert is the author of an extensive work entitled, "De Mundo Nostro Sublunari," in which he defends the modern system of the universe propounded by Copernicus and gives his views on important cosmical problems. This work was published after the author's death, first at Stettin in 1628, and again at Amsterdam in 1651.
Chancellor Bacon was well acquainted with this treatise of our philosopher; indeed he had in his collection the only two manuscript copies ever made, one in Latin and the other in English, a very singular and significant fact in view of the Chancellor's attitude toward Gilbert. Putting it crudely, one would like to know how he obtained possession of the manuscripts and what was his motive in keeping them hidden away from the philosophers of the day. "It is considered surprising," writes Prof. Silvanus P. Thompson, "that Bacon, who had the manuscripts in his possession and held them for years unpublished, should have written severe strictures upon their dead author and his methods, while at the very same time posing as the discoverer of the inductive method in science, a method which Gilberd (Gilbert)had practised for years before."[6]
That Bacon was no admirer of Gilbert's physical and cosmical theories the following passages will show. In the "Novum Organum" the Chancellor wrote: "His philosophy is an instance of extravagant speculation founded on insufficient data"; again, "As the alchemists made a philosophy out of a few experiments of the furnace, Gilbert, our countryman, hath made a philosophy out of the lodestone" ("The Advancement of Learning"); lastly, "Gilbert hath attempted a general system on the magnet, endeavoring to build a ship out of materials not sufficient to make the rowing-pins of a boat" ("De Augmentis Scientiarum").
One is tempted to ask how this strange disregard which Bacon entertained for the scientific views of the greatest natural philosopher of his age and country came to exist? Was it due to a feeling of jealousy that could not brook a rival in the domain of the higher philosophy, or was it because Bacon, the anti-Copernican, wanted to write down Gilbert, the defender of the heliocentric theory, in the British Isles?
When reading Bacon's depreciatory remarks we have to remember that his mathematical and physical outfit was very limited even for the age in which he lived; from which it is safe to infer that he was but little qualified to pass judgment on the value of the electric and magnetic work accomplished in the workshops at Colchester or on the theories to which they gave rise.
Bacon deserves praise for denouncing the prevalent system of natural philosophy which was mainly authoritative, speculative and syllogistic instead of experimental, deductive and inductive, but he was inconsistentand forgetful of his own principles when he belittled the greatest living enemy of mere book-learning, and the most earnest advocate, by word and example, of the laboratory methods for the advancement of learning.
To avoid misapprehension, it should be here stated that Bacon was not always censorious in his treatment of his illustrious fellow-citizen, for in several places he writes approvingly of the electric and magnetic experiments contained inDe Magnete, which he calls in hisAdvancement of Learning, "a painfull (i.e., painstaking) experimentall booke." In other places he draws so freely on Gilbert without acknowledgment as to come dangerously near the suspicion of plagiarism.
Gilbert died, probably of the plague, in the sixtieth year of his age, on December 10th, 1603, and was buried in the chancel of Holy Trinity Church, Colchester, where a mural tablet records in Latin the chief facts of his life.
Dr. Fuller in his "Worthies of England" (1662) describes Gilbert as tall of stature and cheerful of "complexion," a happiness, he quaintly remarks, not ordinarily found in so hard a student and retired a person." Concluding his appreciation of the philosopher, Fuller writes: "Mahomet's tomb at Mecha[7]is said strangely to hang up, attracted by some invisible loadstone; but the memory of this Doctor will never fall to the ground, which his incomparable bookDe Magnetewill support to eternity."
Animated by a similar spirit of national pride, Dryden wrote
Gilbert shall live till loadstones cease to draw,Or British fleets the boundless ocean awe.
Gilbert shall live till loadstones cease to draw,Or British fleets the boundless ocean awe.
We shall close these remarks by Hallam's estimate of Gilbert as a scientific pioneer, contained in hisIntroduction to the Literature of Europe. "The year 1600," he says, "was the first in which England produced a remarkable work in physical science; but this was one sufficient to raise a lasting reputation for its author. Gilbert, a physician, in his Latin treatise on the magnet, not only collected all the knowledge which others had possessed on the subject, but became at once the father of experimental philosophy in this island; and, by a singular felicity and acuteness of genius, the founder of theories which have been revived after a lapse of ages and are almost universally received into the creed of science."
For well-nigh three hundred years,De Magneteremained untranslated, being read only by the scholarly few. The first translation was made by P. Fleury Mottelay, of New York, and published by Messrs. Wiley and Sons in the year 1893. Mr. Mottelay has given much attention to the bibliography of the twin sciences of electricity and magnetism, as the foot-notes which he has added to the translation abundantly prove.
A second translation appeared in the tercentenary year, 1900, and was the work of the members of the Gilbert Club, London, among whom were Dr. Joseph Larmor and Prof. Silvanus P. Thompson. It is a page-for-page translation with facsimile illustrations, initial letters and tail-pieces.
As one would infer from the numerous references contained inDe Magnete, Gilbert had a considerable collection of valuable books, classical and modern, bearing on the subject of his life-work; but these, as well as his terrellas, globes, minerals and instruments, perished in the great fire of London, 1666, with the buildings of the College of Physicians, in which they were located.
A portrait of Gilbert was preserved in the Bodleian Library, Oxford, for many years; but has long since disappeared from its walls. On the occasion of the three hundredth anniversary (1903) of Gilbert's death, a fine painting representing the Doctor in the act of showing some of his electrical experiments to Queen Elizabeth and her court (including Sir Walter Raleigh, Sir Francis Drake and Cecil, Lord Burleigh, famous Secretary of State), was presented to the Mayor of Colchester by the London Institute of Electrical Engineers. A replica of the painting was sent to the St. Louis Exposition, 1904, where it formed one of the attractions of the Electricity Building.
The house in which Gilbert was born (1544) still stands in Holy Trinity Street, Colchester, where it is frequently visited by persons interested in the history of electric and magnetic science.
Brother Potamian.
FOOTNOTES:[6]"Souvenir of Gilberd's Tercentenary," p. 6.[7]See magnetic myths, page 5.
[6]"Souvenir of Gilberd's Tercentenary," p. 6.
[6]"Souvenir of Gilberd's Tercentenary," p. 6.
[7]See magnetic myths, page 5.
[7]See magnetic myths, page 5.
As already seen, the writers of Greece and Rome knew little about the lodestone; we have now to add that the knowledge of electricity which they possessed was of the same elementary character. They knew that certain resinous substances, such as amber and jet had, when rubbed, the property of attracting straws, feathers, dry leaves and other light bodies; beyond this, their philosophy did not go. The Middle Ages added little to the subject, as the Schoolmen were occupied with questions of a higher order. The Saxon Heptarchy came and went, Alcuin taught in the schools of Charlemagne, Cardinal Langton compelled a landless and worthless king to sign Magna Charta, universities were founded with Papal sanction in Italy, France, Germany, England and Scotland, Copernicus wrote his treatise on the revolution of heavenly bodies and dedicated it to Pope Paul III., Tycho Brahé made his famous astronomical observations at Uranienborg and befriended at Prague the penniless Kepler, and Columbus gave a New World to Castile and Leon—all this before the man appeared who, using amber as guide, discovered a new world of phenomena, of thought and philosophy. This man was no other that Gilbert, whose discoveries in magnetism were described in an earlier chapter. The trunk line of his work was magnetism; electricity was only a siding. One was the main subject of a life-long quest while the other was only a digression. It was a digression in which the qualities of the native-born investigator are seen at their very best: alertness and earnestness, resourcefulness and perseverance, all rewarded by a rich harvest of valuable results. It is refreshing and inspiring to read the Second Book of Gilbert's treatise,De Magnete, in which are recorded in quick succession the twenty important discoveries which he made in his new field of labor.
Fig. 9Gilvert's "Versorium" or Electroscope
At the very outset, he found it necessary to invent a recording instrument to test the electrification produced by rubbing a great variety of substances. This he appropriately called aversorium; we would call it an electroscope. "Make to yourself," he says, "a rotating needle of any sort of metal three or four fingers long and pretty light and poised on a sharp point." He then briskly rubs and brings near his versorium glass, sulphur, opal, diamond, sapphire, carbuncle, rock-crystal, sealing-wax, alum, resin, etc., and finds that all these attract his suspended needle, and not only the needle, but everything else. His words are remarkable: "All things are drawn to electrics." Here is a great advance on the amber and jet, the only two bodies previously known as having the power to attract "straws, chaff and twigs," the usual test-substances of the ancients. Pursuing his investigations, he finds numerous bodies which perplex him, because when rubbed they do not affect his electroscope. Among these, he enumerates: bone, ivory, marble, flint, silver, copper, gold, iron,even the lodestone itself. The former class he calledelectrica, electrics; the latter was termedanelectrica, non-electrics.
To Gilbert we, therefore, are indebted for the terms electric and electrical, which he took from the Greek name for amber instead of succinic and succinical, their Latin equivalents. The noun electricity was a coinage of a later period, due probably to Sir Thomas Browne, in whosePseudodoxia Epidemica, 1646, it occurs in the singular number on page 51 and in the plural on page 79. It may interest the reader to be here retold that we owe the chemical termaffinityto Albertus Magnus,barometerto Boyle,gasto van Helmont,magnetismto Barlowe, magneticinclinationto Bond, electriccircuitto Watson, electricpotentialto Green,galvanometerto Cumming,electro-magnetismto Kircher,electromagnetto Sturgeon, andtelephoneto Wheatstone.
Gilbert was perplexed by the anomalous behavior of his non-electrics. He toiled and labored hard to find out the cause. He undertook a long, abstract, philosophical discussion on the nature of bodies which, from its very subtlety, failed to reveal the cause of his perplexing anomaly. Gilbert failed to discover the distinction between conductors and insulators; and, as a consequence, never found out that similarly electrified bodies repel each other. Had he but suspended an excited stick of sealing-wax, what a promised land of electrical wonders would have unfolded itself to his vision and what a harvest of results such a reaper would have gathered in! From solids, Gilbert proceeds to examine the behavior of liquids, and finds that they, too, are susceptible of electrical influence. He notices that a piece of rubbed amber when brought near a drop ofwater deforms it, drawing it out into a conical shape. He even experiments with smoke, concluding that the small carbon particles are attracted by an electrified body. Some years ago, Sir Oliver Lodge, extending this observation, proposed to lay the poisonous dust floating about in the atmosphere of lead works by means of large electrostatic machines. He even hinted in his Royal Institution lecture that they might be useful in dissipating mists and fogs, and recommended that a trial be made on some of our ocean-steamers.
Gilbert next tries heat as an agent to produce electrification. He takes a red-hot coal and finds that it has no effect on his electroscope; he heats a mass of iron up to whiteness and finds that it, too, exerts no electrical effect. He tries a flame, a candle, a burning torch, and concludes that all bodies are attracted by electrics save those that are afire or flaming, or extremely rarefied. He then reverses the experiment, bringing near an excited body the flame of a lamp, and ingenuously states that the body no longer attracts the pivoted needle. He thus discovered the neutralizing effect of flames, and supplied us with the readiest means that we have to-day for discharging non-conductors.
He goes a step further; for we find him exposing some of his electrics to the action of the sun's rays in order to see whether they acquired a charge; but all his results were negative. He then concentrates the rays of the sun by means of lenses, evidently expecting some electrical effect; but finding none, concludes with a vein of pathos that the sun imparts no power, but dissipates and spoils the electric effluvium.
Professor Righi has shown that a clean metallic plate acquires a positive charge when exposed to the ultraviolet radiation from any artificial source of light, but that it does not when exposed to solar rays. The absence of electrical effects in the latter case is attributed to the absorptive action of the atmosphere on the shorter waves of the solar beam.
Of course Gilbert permits himself some speculation as to the nature of the agent with which he was dealing. He thought of it, reasoned about it, pursued it in every way; and came to the conclusion that it must be something extremely tenuous indeed, but yet substantial, ponderable, material. "As air is the effluvium of the earth," he says, "so electrified bodies have an effluvium of their own, which they emit when stimulated or excited"; and again: "It is probable that amber exhales something peculiar that attracts the bodies themselves."
These views are quite in line with the electronic theory of electricity in vogue to-day, which invests that elusive entity with an atomic structure. It is held that the tiny particles or electrons that are shot out from the cathode terminal of a vacuum tube with astounding velocity are none other than particles of negative electricity, pure and simple. They have mass and inertia, both of which properties are held to be entirely electrical, though quite analogous to the mass and inertia of ordinary, ponderable matter.
History shows that scientific theories have their periods of infancy, maturity and decay. When they have served their purpose, like the scaffolding of a building, they are removed from sight and stored away, say, in a limbo of discarded philosophy, for use of the historian of science or of the metaphysician writing on the nature of human knowledge. Such was the fate of Gilbert's"effluvium" theory of electricity, of the fluid theories of Dufay and Franklin, and the ether-strain theory of recent years. "Each physical hypothesis," says Prof. Fleming, "serves as a lamp to conduct us a certain stage in the journey. It illumines a limited portion of the path, throwing light before and behind for some distance; but it has to be discarded and exchanged at intervals because it has become exhausted and because its work is done."
It is a little surprising that the phenomenon of electrical repulsion should have escaped the attention of one so skilled in experimentation as Gilbert. Yet such was the case; and Gilbert even went so far as to deny its very existence, saying, "Electrics attract objects of every kind; they never repel." This error reminds one of Gilbert's own saying that "Men of acute intelligence, without actual knowledge of facts, and in the absence of experiment, easily slip and err." Just twenty-nine years after Gilbert had penned this aphorism, there appeared in Ferrara an extensive work on electric and magnetic philosophy, by the Jesuit Cabeo, in which this electrical repulsion was recognized and described. Having rubbed one of his electrics, Cabeo noticed that it attracted grains of dust at first and afterward repelled them suddenly and violently. In the case of threads, hairs or filaments of any kind, he observed that they quivered a little before being flung away like sawdust. This self-repelling property of electricity, described in the year 1629, opened up a new field of inquiry, which was actively explored by a number of brilliant electricians in England and on the Continent.
This was especially the case after the building of the first frictional machine by Otto von Guericke in 1672. The burgomaster of Magdeburg had already acquired European fame by the original and sensational experiments on atmospheric pressure which he made in presence of the Emperor and his nobles in solemn diet assembled (1651). Von Guericke seems to have been of a mind with Gilbert concerning writers on natural science who treat their subjects "esoterically, miracle-mongeringly, abstrusely, reconditely, mystically"; for he affirms that "oratory, elegance of diction or skill in disputation avails nothing in the field of natural science."
Von Guericke's machine consisted of a ball of sulphur, with the hand of the operator or assistant as rubber. Some years later, the sulphur ball was replaced by Newton (some say Hauksbee) by a glass globe, which, in turn, was exchanged for a glass cylinder by Gordon, a Scotch Benedictine, who was Professor of natural philosophy in the University of Erfurt. In 1755, Martin de Planta, of Sus, in Switzerland, constructed a plate-machine which was subsequently improved by Ramsden of London. The frictional machine, as it was rightly called, has been superseded by the influence machine, a type of static generator which is at once efficient, reliable and easy of operation. The best known form for laboratory use is that of Wimshurst (1832-1903), of London.
Andrew Gordon, the Scotch Benedictine to whom reference has just been made, was a man of an inventive turn of mind. Besides, the cylindrical electric machine which he constructed, he devised several ingenious pieces of electrical apparatus, among which are theelectric chimesusually ascribed to Franklin. They are fully described in hisVersuch einer Erklärung der Electricität, published in 1745. On page 38, he says that he was led to try an electrical method of ringing bells; and then adds: "For this purpose I placed two small wine-glasses near each other, one of which stood on an electrified board, while the other, placed at a distance of an inch from it, was connected with the ground. Between the two, I suspended a little clapper by a silk thread, which clapper was attracted by the electrified glass and then repelled to the grounded one, giving rise to a sound as it struck each glass. As the clapper adhered somewhat to the glasses, the effect on the whole was not agreeable. I, therefore, substituted two small metallic gongs suspended one from an electrified conductor and the other from a grounded rod, the gongs being on the same level and one inch apart. When the clapper was lowered and adjusted, it moved at once to the electrified bell, from which it was driven over to the other, and kept on moving to and fro, striking the bell each time with pleasing effect until the electrified bell lost its charge." In the illustration,ais connected with the electrified conductor;bis the insulated clapper;cthe grounded gong.
Fig. 10Gordon's Electric Chimes, 1745
Gordon's book was published in Erfurt in 1745, while the year 1752 is that in which Franklin applied the chimes to his experimental rod to apprise him of the approach of an electric storm, an application which was original and quite in keeping with the practical turn of mind that characterized our journeyman-printer, philosopher and statesman. Unquestionably, Franklin had all the ingenuity and constructive ability needed to make such an appliance; but there is no evidence that he actually invented it. Though Franklin neither claimednor disclaimed the chimes as his own, all his admirers would have preferred less reticence on his part when the discoveries and inventions of contemporary workers in the electrical field were concerned. He had attained sufficient eminence to permit him to look appreciatingly and encouragingly on the efforts of others.
Gordon also invented a toy electric motor in which rotation was effected by the reaction of electrified air-particles escaping from a number of sharp points. One of these motors consisted of a star of light rays cut from a sheet of tin and pivoted at the center, with the ends of the rays slightly bent aside and all in the same direction. When electrified, Gordon noticed that the star required no extraneous help to set it in motion. It was a self-starting electric-motor. In the dark, the points were tipped with light, and as they revolved traced out a luminous circle which "could neither be blown out nor decreased."
The reader will recognize in this description taken from Gordon'sVersuch, page 45, theelectric whirlof the lecture-table; Gordon's name is never associated with it, but that of Hamilton (Hamilton's "fly" or Hamilton's "mill") sometimes is!
This irrepressible monk seems to have been one of the earliest electrocutors, for it is said that many an innocent chaffinch fell victim to discharges from his machine; and we would be disposed to think of him as a wizard on learning that he ignited spirits by using an electrified stream of water, to the astonishment and mystification of the spectators.
Abbé Menon was kinder to the feathered tribe than his black-cowled brother of Erfurt; he did not subject them to a powerful discharge, but rather to a gentleelectrification for the purpose of determining what physical or physiological effect the agent would have on the animal system. The Abbé found that cats, pigeons, sparrows and chaffinches lost weight by being electrified for five or six hours at a time, from which he concluded that electricity augments the slow, continuous perspiration of animals. The same was found to take place with the human body itself. The reader will remember that Stephen Gray in 1730 suspended a boy by means of silken cords for the purpose of electrification; Abbé Nollet did the same, and doubtless his friend Abbé Menon adopted a similar mode of insulation for complacent electrical subjects. An easier mode of operating would have been to make the child stand on a cake of resin, the insulating property of which had been discovered by Stephen Gray.
About this time, 1746, Franklin appears on the scene, and though he devoted but nine years (1746-1755) of his life to the study of electricity, he made discoveries in that fascinating branch of human knowledge that will hand his name down the centuries.
Franklin's life is interesting and instructive on account of the difficulties which he met and overcame, for his strength of will, tenacity of purpose, the philosophy which he followed, his devotedness to science, and the success which he achieved.
Our philosopher's moral code comprised the thirteen virtues of temperance, silence, order, resolution, frugality, industry, sincerity, justice, moderation, cleanliness, tranquility, chastity and humility. To each of these virtues Franklin attached a precept which makes edifying reading even at the present day:temperance, eat not to dullness, drink not to elation;silence, speak not but what may benefit others or yourself, avoid trifling conversation;order, let all your things have their places, let each part of your business have its time;resolution, resolve to perform what you ought, perform without fail what you resolve;frugality, make no expense, but do good to others or yourself,i.e., waste nothing;industry, lose no time, be always employed in something useful, cut off all unnecessary actions;sincerity, use no hurtful deceit, think innocently and justly, and if you speak, speak accordingly;justice, wrong no one by doing injury or omitting the benefits that are your duty;moderation, avoid extremes, forbear resenting injuries so much as you think they deserve;cleanliness, tolerate no uncleanliness in body, clothes or habitation;tranquility, be not disturbed by trifles or accidents common or unavoidable;chastity(no remark);humility, imitate Jesus.
This last virtue seems to have given Franklin very much concern; for he admits that he had the appearance of humility, and immediately adds that in reality there is no passion of the human breast so hard to subdue as pride. He is shrewd enough to say that "even if I could conceive that I had completely overcome it, I should probably be proud of my humility." Like many another, the virtue which gave him the most trouble wasorder, and this never became conspicuously apparent at any time of his long life.
In his endeavors after the higher life, he seems to have been animated with the earnest spirit of the ascetic who binds himself to strive after perfection as laid down in the maxims and counsels of the Gospel. It is not without surprise and perhaps a feeling too of self-condemnation, that we read the means which headopted to reach a high moral standard. Taking for granted that he had a true appreciation of right and wrong, he did not see why he should not always act according to the dictates of conscience. To improve himself morally and advance in the higher life, he adopted a means that should have proved effective. Taking the first of the thirteen fundamental virtues, he applied himself to its acquisition for a whole week together, after which he took the second, then the third, and so on with the rest. He thought that by making daily acts of the virtue, it would become habitual with him at the end of the week. When the last of the thirteen virtues had received its share of attention, he returned to the first one on the list and proceeded round the cycle again. Being a man of purpose and tenacity, he completed the circle of his chosen virtues four times a year; subsequently he extended the time of individual practise so as to take a whole year for the course; and later on, he devoted several years to the completion of his list.
As an aid in this work of self-betterment, Franklin examined himself daily, registering his failures in a little book which was ruled for the purpose, a column being allowed for each day and a line for each of the thirteen virtues. He naively tells us the result of this exercise of daily introspection in these words: "I am surprised to find myself so much fuller of faults than I had imagined; but I had the satisfaction of seeing them diminish."
The evening examination of conscience was always concluded by the following prayer written by Franklin himself: "O powerful Goodness! bountiful Father! merciful Guide! increase in me that wisdom which discoversmy truest interest. Strengthen my resolutions to perform what that wisdom dictates. Accept my kind offices to Thy other children as the only return in my power for Thy continual favors to me."
An extensive reader, Franklin found in Thomson's poems some lines that appealed to him very strongly by the beauty of the sentiment expressed. He called them "a little prayer," which he recited from time to time:
"Father of light and life, Thou Lord Supreme,Oh, teach me what is good; teach me Thyself.Save me from folly, vanity and vice;From every low pursuit; and fill my soulWith knowledge, conscious peace and virtue pure;Sacred, substantial, never-failing bliss!"
"Father of light and life, Thou Lord Supreme,Oh, teach me what is good; teach me Thyself.Save me from folly, vanity and vice;From every low pursuit; and fill my soulWith knowledge, conscious peace and virtue pure;Sacred, substantial, never-failing bliss!"
His was a praiseworthy attempt at emancipating himself from the thraldom of passion and raising himself to the high plane of perfection required by the Master when He said "Follow Me." Doubtless, as time wore on, he must have felt as many before and since, that the spirit is willing but the flesh is weak.
In his autobiography, Franklin attributes his success in business not only to his self-control, uniformity of conduct, philosophical indifference to slight or pique, but also to his habits of frugality, the result in part of his early training. "My original habits of frugality continuing," he says, "and my father having frequently repeated a proverb of Solomon, 'Seest thou a man diligent in his business? he shall stand before kings,' I from thence considered industry as a means of obtaining wealth and distinction, which encouraged me, tho' I did not think that I should ever literallystand before kings, which, however, has since happened." Ouraged philosopher proceeds to tell us of his good fortune with a little bit of pardonable vanity, to which, by the way, he was never a great stranger, despite his philosophy, acquired virtue, and staid character. Referring to the kings of the earth, he informs us that he "stoodbefore five, and even had the honor ofsitting downwith one to dinner."
An important event in Franklin's life was the founding by him of the first public library in the country in the year 1732. Though but twenty-six years of age, he seems to have been as well aware as any of the millionaire philanthropists of to-day, of the good that may be accomplished among common people by providing them with suitable reading matter. He watched with eagerness the progress of his experiment and was pleased with the success that crowned it. He observes that such libraries "tend to improve the conversation of Americans and to make common tradesmen and farmers as intelligent (well-informed?) as most gentlemen from other countries."
Peter Collinson, Fellow of the Royal Society of London, who had dealings with some Philadelphia merchants, was led to take an active interest in the library. This he did by sending over a number of books and papers relating to electricity together with an "electrical tube" with instructions for its use.
These literary and scientific contributions sent from London from time to time, excited much interest among the charter members of the Library Company, and principally that of Franklin himself. He had heard something of the new order of phenomena which was just then engaging the attention of European physicists. In the summer of 1746, while on a visit to Boston, hisnative place, he assisted at a lecture on electricity by a certain Dr. Spence, a Scotchman, who sought to illustrate the properties of electrified bodies by such experiments as could be made with glass tubes and suitable rubbers, the rudimentary apparatus available at the time. Franklin was impressed by what he saw and heard, even though he indulged in a little destructive criticism when he said that the experiments were "imperfectly made," because the lecturer was "not very expert." When Franklin wrote those words, he knew by repeated and painful experience the difficulty of getting satisfactory results from rubbing glass tubes or rotating glass globes, owing to the provoking attraction which plain, untreated glass has for moisture. Knowing this, he might have been less severe in his strictures on his friend, the peripatetic electrician.
It is evident, however, that the experiments which he witnessed surprised and pleased him, for, having shortly afterward received some electrical tubes together with a paper of instructions, from his London friend, Peter Collinson, he set to work for himself without delay. We may well say of him that what his right hand found to do, he did calmly, but with all his might. A twelve-month had not elapsed before he wrote: "I never was engaged in any study that so totally engrossed my attention and time as this has lately done; for, what with making experiments when I can be alone and repeating them to my friends and acquaintance who, from the novelty of the thing, come continually in crowds to see them, I have had little leisure for anything else." (1747.)
Here we see the calm, persistent character of the philosopher united with the affability and communicativeness of the gentleman.
For the sake of encouraging others as well, perhaps, as through a sense of personal relief, Franklin had a number of long tubes of large bore blown at the local glass-house, which tubes he distributed to his friends that they, too, might engage in research work. In this way, rubbing and rubbing of an energetic kind became quite an occupation in the Franklin circle. Kinnersley, whose name still survives in works on static electricity in connection with an electric "thermometer" which he devised, was among the band of ardent workers who ungrudgingly acknowledged Franklin's superior acumen, comprehensive grasp of detail and wondrous insight into the mechanism of the new phenomena. If we say that Franklin was not a genius, it is only for the purpose of adding that even in those early electrical studies he displayed an uncommon amount of the unlimited capacity for taking pains which is said to be associated with that brilliant gift. He tested all his results with great care and in a variety of ways before accepting any of them as final; and considered his explanations of them provisional, being ever ready to modify them or give them up altogether if shown to conflict with the simple workings of nature.
As early as 1733, the refined and tactful Dufay, in France, showed by numerous experiments on woods, stones, books, oranges and metals that all solid bodies were susceptible of electrification. This was a notable advance which swept away Gilbert's classification of bodies into electrics and non-electrics. The French physicist soon drew from his observations the conclusion that electrification produced by friction is of two kinds, to which he applied the terms vitreous and resinous, theformer being developed when glass is rubbed with silk and the latter when amber or common sealing-wax is rubbed with flannel. He noticed, too, that silk strings repelled each other when both were touched either with excited glass or sealing-wax; but that they attracted each other when touched one with glass and the other with sealing-wax. From these observations, he deduced the electrostatic laws, that similarly electrified bodies attract while dissimilarly electrified bodies repel each other.
The law of distance was discovered later by Coulomb, who, in 1785, showed that the law of repulsion as well as of attraction between two electrified particles varies inversely as the square of the distance. In the year 1750, the law of the inverse square for magnets was stated by John Michell, who expressed it by saying that the "attraction and repulsion decrease as the square of the distance from the respective poles increases." Michell was fourth wrangler of his year (1748-9), Fellow of Queen's College, Cambridge, and inventor of thetorsion balance, which, however, he did not live to use; but which, in the hands of Cavendish, yielded important results on the mean density of the earth. Coulomb probably re-invented the "balance" and applied the practical, laboratory instrument which he made it, to the study of the quantitative laws of electricity and magnetism.
To observe and correlate phenomena is the special work of the physicist; to speculate on ultimate causes is the privilege of the philosopher. Dufay was both. The theory which he offered was a simple one, even if untrue to nature. It was a good working hypothesis for the time being.
According to this theory, there are two distinct, independent electrical fluids mutually attractive but self-repelling. With that postulate, Dufay was able to offer a plausible explanation of a great many phenomena that puzzled the electricians of the time.
Franklin, however, held a different view; rejecting the dual nature of electricity, he propounded his one-fluid theory, which was found equally capable of explaining electrical phenomena. A body having an excess of the fluid was said to bepositivelycharged, while one with a deficit was said to benegativelycharged. The sign plus was used in one case and the sign minus in the other; and just as two algebraical quantities of equal magnitude but opposite sign give zero when added together, so a conductor to which equal quantities of positive and negative electricity would be given would be in the neutral state. The Franklinian theory was welcomed in England, Germany and Italy, but it met with opposition in France from the brilliant Abbé Nollet and the followers of Dufay.
Each of the rival theories affords a mental conception of the forces in play and also a consistent explanation of the resulting phenomena. Their simplicity, and, at the same time, the comprehensiveness of explanation which they afford, will continue to give them a place in our text-books for many years to come.
Efforts are being made to apply theelectronictheory to the various phenomena of electrostatics, the electron being the smallest particle of electricity that can have separate, individual existence. It is many times smaller than the hydrogen atom, the smallest of chemical atoms, and it possesses all the properties of negative electricity. By the loss of one or more electrons, a body becomes positively electrified, whereas by the acquisitionof one or more electrons it becomes negatively electrified. The electron at rest gives rise to the phenomena of electrostatics; in motion, it gives rise to electrical currents, electromagnetism and electric radiation.
We do not know what led Franklin to call positive the electrification of glass when rubbed with silk, and negative that of sealing-wax when rubbed with flannel. If he meant to imply that positive is the more important of the two, he erred, for many reasons can be given to show the preponderating influence of negative electricity; but it is too late now to change the terminology.
If asked to point out differences between the physical effects of positive and negative electrification, we would refer to the positive brush, which is finer and much more developed than the negative; to the Wimshurst machine, with its positive brushes on one side and negative "beads" on the other; to the positive charge acquired by a clean plate of zinc when exposed to ultraviolet light; to the ordinary vacuum tube in which there is a violet glow at the cathode end or negative terminal; to Crookes's tubes, X-ray tubes and other high vacuum tubes, in which electrified particles, Kelvin'smolecular torrent, are shot out from the negative electrode with great velocity; and to arc-lamps using a direct current in which the plus carbon is hollowed out crater-like, has the higher temperature and wastes away twice as fast as the negative.
The year 1746 is anannus mirabilisin the history of electricity, for it was in the January of that year that an attempt to electrify water by Musschenbroek, of Leyden, led to the discovery of the principle of the electrostatic condenser. Whatever may be thought of theclaim for priority put forward in favor of Dean von Kleist, of Cammin in Pomerania, or of Cunæus, of Leyden, it is certain that the discovery became known throughout Europe by the startling announcement and sensational description given of it by Musschenbroek, a renowned professor of a renowned university. He was not only surprised but terror-stricken by the effect of the electric energy which he had unconsciously stored up in his little phial; for after telling his French friend Réaumur, the physicist, that he felt the commotion in his arms, shoulders and chest, he added that he would not take another shock for the whole kingdom of France! A resolution destined to be broken, like so many others before and since.
Fig. 11Modern Form of Leyden Jar with Movable Coatings
Very different was the sentiment of Bose, Professor of Physics in the University of Wittenberg, who is credited with saying that he would like to die by the electric shock, that he might live in the memoirs of the French Academy of Sciences.
The Leyden jar became at once the scientific curiosity and universal topic of discussion of the time; and not only was it the curiosity, but also thecruxof the day, puzzling investigators, perplexing philosophers and giving rise to animated controversies. The mystery was soon dispelled, however, when Franklin began in 1747 his searching inquiry into the electric conditions of each element of the jar. Nothing escaped his subtle mind and nothing was left undone by his deft hand. The evidence of experimentand the logic of facts carried at last conviction even with Londoners and Parisians, who were wont to look upon Americans as mere colonists, who had neither time nor opportunity for scientific pursuits, being obliged to hew their way through virgin forests or drive the roving Indian back from their frontiers into the wilds of the West. The theory of the Leyden jar given by Franklin 160 years ago has stood the test of time. It has met with universal acceptance; and, despite our manifold advances, but little of permanent value has been added to it.
It is very interesting to follow the main lines of this magnificent research. Franklin electrifies, in the usual way, water contained in a small flask, complaisantly taking the shock on completing the circuit. To find where the charge resides, whether in the hand of the operator, as some said, or in the water, as others maintained, he again electrifies the water and pours it into another flask, which fails, however, to give a shock, thus showing that the charge had not been carried over with the water. Convinced that the charge was still somewhere in the first phial, he carefully poured water into it again; and found, to his intense satisfaction, that it was capable of giving an excellent shock. It was now clear to him that the energy of the charge was either in the hand of the experimenter or in the glass itself, or in both. To determine this nice point, he proceeds to construct a "jar" which could easily be taken to pieces. For this purpose, he selected a pane of glass; and, laying it on the extended hand, placed a sheet of lead on its upper surface. The leaden plate was then electrified; and when touched with the finger, a spark was seen and a shock felt. By the addition of another plateto the lower surface, the shocking power of this simple condenser was increased. In this efficient form he had a readily dissectible condenser, which allowed him to throw off and replace the coatings at will, and thereby to prove beyond cavil that the seat of the stored-up electric energy is not in the conductors, but in the glass itself. This was a discovery of the first magnitude and one destined to associate the name of Franklin with those of the most eminent electricians down the ages. Fig. 11 shows the modern form of the jar with movable coatings.