Lives of the electricians

by William T. Jeans

PROFESSOR TYNDALL.

CHAPTER I.

“Precious is the new light of knowledge which our Teacher conquers for us; yet small to the new light of Love which also we derive from him: the most important element of any man’s performance is the Life he has accomplished.”—Carlyle.

The position of Professor Tyndall in the world of science is somewhat unique. He is one of our most popular teachers of physical science; he is one of our most successful experimentalists; and he is one of our most attractive writers. By his discoveries he has largely extended our knowledge of the laws of Nature; by his teaching and writings he has probably done more than any other man in England to kindle a love of science among the masses; and by his life he has set an example to students of science which cannot be too widely known or appreciated. There are men who have made greater and more useful discoveries in science, but few have made more interesting discoveries. There are men whose achievements have been more highly esteemed by the devotees of pure science, but rarely has a scientific man been more popular outside the scientific world. There are men whose culture has been broader and deeper, but who have nevertheless lacked his facility of exposition and gracefulness of diction. The goddess of Science, which ofttimes was presented to the public with the repulsive severity of a skeleton, he has clothed with flesh and blood, making her countenance appear radiant with the glow of poesy, and susceptible even to a touch of human sympathy; while amongst scientific contemporaries, though he does not rank as one of those creative minds that mark an epoch in the history of physical philosophy, he may yet be said to have “built many a stone into the great fabric of science, which gives it an ever-broader support and an ever-growing height without its appearing to a fresh observer as a special and distinctive work due to the sole exertion of any one scientific man.” He commenced his scientific career at the time when Sir William Grove began to elaborate that theory of the co-relation of the physical sciences which Newton suspected and Faraday elucidated; namely, “that the various affections of matter, heat, light, electricity, magnetism, chemical affinity, and motion are all correlative or have a reciprocal dependence: that neither, taken abstractedly, can be said to be the essential or proximate cause of the others, but that either may, as a force, produce the others; thus heat may mediately produce electricity, electricity may produce heat; and so of the rest.” Professor Tyndall has extended or simplified our knowledge of these forces. Indeed he may be said to have revealed some hidden links in the chain of causation. He has extended and consolidated our knowledge of magnetism; as an explorer and discoverer in the domain of radiant heat he stands almost alone; and as a lecturer and experimentalist he has probably done more than any other man to popularise the science of electricity.

There is a growing tendency in the present day to appreciate personal achievement more highly than ancient lineage; and it is becoming more a matter of boast in the intellectual world to say that an eminent man was self-made than to say he was of noble birth. The subject of this memoir can boast both of high descent and of lowly birth. “I am distantly connected,” he says, “with one William Tyndale, who was rash enough to boast, and to make good his boast, that he would place an open Bible within reach of every ploughboy in England. His first reward was exile, and then a subterranean cell in the Castle of Vilvorden. It was a cold cell, and he humbly, but vainly, prayed for his coat to cover him and for his books to occupy him. In due time he was taken from the cell and set upright against a post. Round neck and post was placed a chain, which being cunningly twisted, the life was squeezed out of him. A bonfire was made of his body afterwards.”

It is said that the martyr Tyndale was descended from the ancient barons of Tyndale in Northumberland, whose title eventually passed into the family of the Percies, and that the said ancestors, leaving the north during the war of the Roses, afterwards sought and found refuge in Gloucestershire. Of one of these refugees the martyr of Vilvorden was the great-grandson, and was, it is believed, born in 1484. Both family tradition and documents show that some members of the Tyndale family, who were cloth manufacturers, migrated from Gloucestershire to the county of Wexford in Ireland about two centuries ago. One William Tyndale landed on the coast of Ireland in 1670, and his descendants in later years became scattered over Wexford, Waterford, and Carlow. Their fortunes varied; but for our purpose it is sufficient to know that the grandfather of the Professor had a small estate in Wexford; and that on removing thence to the village of Leighlin Bridge on the banks of the Barrow, county Carlow, he continued to prosper until he got into easy circumstances. But throughout the whole race of Tyndale, from the Martyr down to the Professor, intellectual independence appears to have been preferred to worldly independence, and it was the exercise of this trait that cost the Professor the small patrimony which his grandfather had acquired. A high sense of rectitude and a benevolent disposition are not incompatible with excessive susceptibility to opposition; and hence persons of high principles sometimes stand like adamant on points that to worldly minds appear too trifling even for controversy, much less for self-sacrifice. Though the opinions of the Tyndales may have differed, the leading principles that governed their conduct appear to have been maintained with remarkable consistency and self-denial. John Tyndale, the father of the Professor, differed in opinion with his own father, William Tyndale of Leighlin Bridge, on some point that has long since been forgotten, but in consequence of that difference William revoked his will in favour of his first-born son, John, and left his property to two sons of a second marriage.

Leighlin Bridge, where John Tyndall was born in humble circumstances in 1820, was a thriving town of 2,000 inhabitants, forty-six miles south-west of Dublin. It was then the entrepot where the great southern road from Dublin to Waterford and Cork crossed the Barrow, and it has consequently been declining ever since the development of the railway system diverted the traffic. It was not destitute of historical associations, which to the Irish mind were of an exciting character. Nor was the country destitute of natural attractions. When Tyndall was a youth its general aspect was described as soft and agreeable, with little of forcible or imposing scenery, yet free from those harsh features which so frequently mar the effect of Irish landscape. In some parts it so closely resembled the “champaign, ornate, and agreeable districts of central England,” that it was said constantly to remind an English traveller passing through the country of the “equable, grateful scenery, the calm and soft-faced prettiness of territorial view to which his mind had been accustomed.”

Yet to the ordinary English reader its loneliness would appear to have little that was likely to fire the opening mind of the Apostle of Physical Science. It need not, however, appear an inauspicious birthplace to those who believe that it is no mere accident that has made great enthusiasts generally proceed from lonely or sterile countries.

Let us therefore look a little more into this home from which so much light was to be reflected in after years by its then youngest inhabitant. The Professor’s father, being left dependent on his own resources, early joined the Irish Constabulary force and remained in it for several years. He was regarded as a man of exceptional ability and unswerving integrity, and was respected by all who knew him. A sturdy politician and a zealous Orangeman, he preserved as a precious relic a bit of flag which was said to have fluttered at the Battle of the Boyne. In such a man Protestantism was no mere hereditary faith. It was evolved from his own inner consciousness, and was part of his intellectual being. His earnest and capacious mind had mastered the works of Tillotson, Jeremy Taylor, Chillingworth, and other writers who were not only the pillars of the Protestant faith, but still remain unsurpassed as masters of English prose. In our own day men of respectable theological attainments are content to reflect, in lunar-like scintillations, the intellectual splendour, the massive diction, the rich and glowing periods that adorn their pages; and no better evidence could be given of the fine intelligence of John Tyndall, of Leighlin Bridge, than to say that his delight was in the works of these great men. It is the fashion nowadays for critics of the “newspaper” school to sneer at their “pompous grandeur,” but it is those living writers who in elevation of thought and graces of style show the greatest affinity to them that are the most popular. It was with such works that John Tyndall, père, sought to imbue the mind of his only surviving son; and the subtle thoughts and inspiring sentiments which he gathered from such classic ground must have had an invigorating effect on his son’s susceptible mind. Besides his early familiarity with the works of these powerful thinkers, it is said that he soon knew the Bible almost by heart. This species of intellectual discipline has sometimes been pointed to as presenting a strange contrast with his excursions in later life into those regions of natural philosophy which have sometimes been regarded as antagonistic to theology. But it is more than probable that this early training did much to model and chasten the rich, transparent, simple language in which he has so beautifully expounded the laws of Nature. There is high authority for saying that he could have had no better model. Alexander von Humboldt, after reviewing the whole course of ancient literature for “images reflected by the external world on the imagination,” says that “as descriptions of nature the writings of the Old Testament are a faithful reflection of the character of the country in which they were composed, of the alternations of barrenness and fruitfulness, and of the Alpine forests by which the land of Palestine was characterised. The epic or historical narratives are marked by a graceful simplicity, almost more unadorned than those of Herodotus, and most true to nature. Their lyrical poetry is more adorned, and develops a rich and animated conception of the life of nature. It might almost be said that one single psalm (the 104th) represents the image of the whole cosmos.... The meteorological processes which take place in the atmosphere, the formation and solution of vapour, according to the changing direction of the wind, the play of its colours, the generation of hail, and the rolling thunder are described with individualising accuracy, and many questions are propounded which we in our present state of physical knowledge may indeed be able to express under more scientific definitions, but scarcely to answer satisfactorily.” Most of our great writers have acknowledged that the literature that first made a lasting impression on their mind materially influenced their style of writing, and in the writings of Professor Tyndall will be found a good deal of the beautiful simplicity and poetic feeling which abound in Hebrew literature.

The origin of his love of nature is a problem that has exercised his own mind. “I have sometimes tried,” he says, “to trace the genesis of the interest which I take in fine scenery. It cannot be wholly due to my early associations; for as a boy I loved nature, and hence to account for that love of nature I must fall back upon something earlier than my own birth. The forgotten associations of a foregone ancestry are probably the most potent elements in the feeling.” He then accepts as exceedingly likely Mr. Herbert Spencer’s idea that the mental habits and pleasurable activities of preceding generations had descended with considerable force to him. He has, indeed, repeatedly supported the view that intellectual character is largely formed from ancestral peculiarities; and if that be so, he may surely be said to have reproduced some of the higher mental characteristics of the Irish race with marvellous exactness. “In the Celtic genius,” says Michelet, “there is a feeling repugnant to mysticism, and which hardens itself against the mild and winning word, refusing to lose itself in the bosom of the moral God. The genius of the Celts is powerfully urged towards the material and natural; and this proneness to the material has hindered them from easily acceding to laws founded on an abstract notion.... In the seventh century St. Columbanus said: ‘The Irish are better astronomers than the Romans.’ It was a disciple of his, also an Irishman, Virgil, Bishop of Saltzburg, who first affirmed the rotundity of the earth and the existence of the Antipodes. All the sciences were at this period cultivated with much renown in the Scotch and Irish monasteries.” These characteristics appear to predominate in the Irish intellect at the present day. Physical science, which is the glory of our age, owes much to Ireland. Sir William Thomson, one of the most versatile and brilliant of natural philosophers, was born in Ireland; so was George Gabriel Stokes, one of Newton’s worthiest successors in the Lucasian chair of mathematics at Cambridge as well as President of the Royal Society; Henry Smith, the greatest mathematician of his time at Oxford, who died in 1883, was an Irishman; Sir William Rowan Hamilton, the Astronomer-Royal for Ireland, was also one of Ireland’s most precocious sons; and in such a constellation of Irish genius Professor Tyndall excels as a popular expositor of the laws of nature.

At the age of seven he began to show his natural taste for the works of nature, and his father gave him glowing accounts of the achievements of Newton as

“That sun of science, whose meridian ray

Kindled the gloom of nature into day.”

A good education was the only patrimony which his father could bestow upon him. He was therefore sent to the best school within reach, and remained at it till his nineteenth year. In his earlier schooldays he preferred physical to mental exercises, and thus became expert in running, swimming, climbing, and other sports. The branch of study in which he excelled was mathematics. Under the tuition of a good teacher in an Irish national school, he acquired a knowledge of elementary algebra, geometry, trigonometry, and conic sections. His favourite “arithmetic” was the treatise of Professor Thomson, the father of Sir William Thomson, who in later years became one of his most brilliant contemporaries. At the age of seventeen he showed exceptional facility in solving geometrical problems, and on his way home from school, in company with his teacher, he would work out demonstrations on the snow in winter. But even that accessory he became able to dispense with; for he could so clearly present the relations of space to his mind without the aid of diagrams, that he was able to draw mentally the lines illustrating the solution of complex problems and to preserve this mental image so distinctly that he could reason upon it as correctly as on the diagrams drawn upon paper required by ordinary students. When he came to solid geometry he was able by means of this power of mental representation to dispense with models, which to other students were indispensable.

His powers of reasoning were not confined to mathematics. In his youth he was accustomed to debate with his father the points of doctrine that divide the Protestant from the Roman Catholic Church, reasoning high “of Providence, fore-knowledge, will, and fate.” Sometimes the son took the Protestant side and at other times the Romish side; and in either case he showed much dialectical skill and theological knowledge. He also took more than ordinary interest in the study of English grammar, which he has described as being to his youthful mind a discipline of the highest value and a source of unfailing delight.

Leaving school in April, 1839, he joined a division of the Ordnance Survey then stationed in that district, under the command of Lieut. Geo. Wynne, of the Royal Engineers, who afterwards became an intimate friend of his, and to whom he has frequently expressed his obligation for acts of kindness that promoted his welfare in after life. About that time a good deal of astonishment was publicly expressed at the mathematical powers of one of the many boys employed in calculations on the Ordnance Survey; his name was Alexander Gwin, a native of Derry, and it was reported that at the age of eight years he had got by rote the fractional logarithms from 1 to 1,000, which he could repeat in regular rotation, or otherwise. His rapidity and correctness in calculating trigonometrical distances, triangles, &c., were extraordinary: he could make a return, in acres, roods, and perches, in less than one minute of any quantity of land, on receiving the surveyor’s chained distances; a calculation which the greatest arithmetician would take nearly an hour to do, and would not be so sure of accuracy at the end of that time.

The intention of young Tyndall was to become a civil engineer, which then appeared a most attractive profession to him. As a preliminary qualification he determined to master all the operations of the surveyors. Draftsmen being the best paid, he worked as a draftsman, but applied himself so well to learning the whole business that he soon became able to do the work of the computor, the surveyor, and the trigonometrical observer. He then asked to be allowed to go on field-work, and his desire was granted. In 1841, while he was stationed at Cork, a circumstance occurred which may be described as the turning point in his career. He worked at mapping in company with a gentleman, who, assuming a paternal interest in him, one day, asked the young and promising surveyor how he employed his leisure hours. Dissatisfied with the account given, the gentleman said to him: “You have five hours a day at your disposal, and this time ought to be devoted to study. Had I, when I was your age, had a friend to advise me as I now advise you, instead of being in my present subordinate position, I should be the equal of the director of the Survey.” Pregnant words! Next morning young Tyndall was at his books by five o’clock, and the studious habits then commenced he continued for twelve years.

Next year he was in Preston, and there becoming a member of the Preston Mechanics’ Institute he attended its lectures and made use of its library. One experiment which he saw there he never forgot. In a lecture on respiration, Surgeon Cortess showed the changes produced by the passage of air through the lungs, and in order to illustrate the fact that what went in as free oxygen came out in carbonic acid, he forced his breath through lime water in a flask by means of a glass tube dipped into it; the carbonic acid from the lungs converted the dissolved lime into carbonate of lime, which being practically insoluble was precipitated. All this, he says, was predicted beforehand by the lecturer, “but the delight with which I saw this prediction fulfilled by the conversion of the limpid lime-water into a turbid mixture of chalk and water remains with me as a memory to the present hour” (1884.)

His diligence in study he was soon able to turn to good account. On one occasion there was a dearth of men capable of making trigonometrical observations when such observations were required. Tyndall offered his services in that department; but the offer was not readily accepted. His superiors hesitated to intrust him with a theodolite on account of his inexperience in work of that description: and indeed there were bets made against his chances of success. However, being allowed to try his hand at it, he at once took his theodolite into an open field, where he examined all its parts, and studied their uses. He then made the trigonometrical observations prescribed to him, and when they were compared with the measurement previously made on a larger scale, his work was pronounced to have been successfully done. When he quitted the Ordnance Survey in 1843 he had practically mastered all its operations.

The pay upon the Ordnance Survey, however, was very small, but having ulterior objects in view, he considered the instruction received as some set-off to the smallness of the pay. In order to “prevent some young men from considering their fate specially hard, or from being daunted, because from a very low level they had to climb a very steep hill,” he has stated that on quitting the Ordnance Survey in 1843, his salary was a little under twenty shillings a week, adding, “I have often wondered since at the amount of genuine happiness which a young fellow, of regular habits, not caring for either pipe or mug, may extract even from pay like that.”

In 1844 affairs in this country did not look very tempting to him, and he therefore resolved to go to America, whither some relatives had emigrated early in the century. He had actually made preparations for going there before some of his friends succeeded in dissuading him from it. A sudden outburst of activity in railway construction at the same time opened up a brighter prospect at home. After a pause, he says, there came the mad time of the railway mania, when he was able to turn to account the knowledge he had gained upon the Ordnance Survey; in Staffordshire, Cheshire, Lancashire, Durham, and Yorkshire especially, he was in the thick of the fray.

As a workman at that period he has been highly spoken of by his contemporaries. One of them has stated that “Extreme caution and accuracy, together with dauntless perseverance under difficulties, characterised the performance of every piece of work he took in hand. Habitually, indeed, he pushed verification beyond the limits of all ordinary prudence, and, on returning from a hard day’s work, he has been known to retrace his steps for miles in order to assure himself of the security of some ‘bench mark,’ upon whose permanence the accuracy of his levels depended. Previous to one of those unpostponable thirtieths of November, when all railway plans and sections had to be deposited at the Board of Works, a series of levels had to be completed near Keighley in Yorkshire, and Manchester reached before midnight. The weather was stormy beyond description; levelling staves snapped in twain before the violent gusts of wind; and level and leveller were in constant peril of being overturned by the force of the hurricane. Assistants grumbled ‘Impossible,’ and were only shamed into submissive persistence by that stern resolution which, before nightfall, triumphed over all obstacles.”

Of these stirring scenes the Professor has given a graphic account. He says:—“It was a time of terrible toil. The day’s work in the field usually began and ended with the day’s light, while frequently in the office, and more especially as the awful 30th of November—the latest date at which plans and sections of projected lines could be deposited at the Board of Trade—drew near, there was little difference between day and night, every hour of the twenty-four being absorbed in the work of preparation. Strong men were broken down by the strain and labour of that arduous time. Many pushed through, and are still among us in robust vigour; but some collapsed, while others retired with large fortunes, but with intellects so shattered that, instead of taking their places in the front rank of English statesmen, as their abilities entitled them to do, they sought rest for their brains in the quiet lives of country gentlemen. In my own modest sphere I well remember the refreshment I occasionally derived from five minutes’ sleep on a deal table, with Babbage and Callet’s Logarithms under my head for a pillow. On a certain day, under grave penalties, certain levels had to be finished, and this particular day was one of agony to me. The atmosphere seemed filled with mocking demons, laughing at the vanity of my efforts to get the work done. My levelling staves were snapped, and my theodolite was overthrown by the storm. When things are at their worst a kind of anger often takes the place of fear. It was so in the present instance; I pushed doggedly on, and just at nightfall, when barely able to read the figures on my levelling staff, I planted my last ‘benchmark’ on a tombstone in Haworth Churchyard. Close at hand was the vicarage of Mr. Brontë, where the genius was nursed which soon afterwards burst forth and astonished the world. It was a time of mad unrest—of downright money mania. In private residences and public halls, in London reception rooms, in hotels and the stables of hotels, among gipsies and costermongers, nothing was spoken of but the state of the share market, the prospects of projected lines, the good fortune of the ostler or potboy who by a lucky stroke of business had cleared £10,000. High and low, rich and poor, joined in the reckless game. During my professional connection with railways I endured three weeks’ misery. It was not defeated ambition; it was not a rejected suit; it was not the hardship endured in either office or field; but it was the possession of certain shares purchased in one of the lines then afloat. The share list of the day proved the winding-sheet of my peace of mind. I was haunted by the Stock Exchange. I became at last so savage with myself that I went to my brokers and put away, without gain or loss, the shares as an accursed thing.”

When in Halifax in 1845 he attended a lecture which was delivered by Mr. George Dawson, and which appeared to make a lasting impression on his mind. That popular lecturer then defined duty as a debt owed; and with reference to the Chartist doctrine of “levelling” then in vogue, he said: Supposing two men to be equal at night, and that one rises at six while the other sleeps till nine, what becomes of the gospel of levelling then? The Professor regarded these as the words of Nature, and there was, according to his impression, “a kindling vigour in the lecturer’s words that must have strengthened the sense of duty in the minds of those who heard him.”

It was while working in Yorkshire about that time that he first met Mr. T. A. Hirst, then an articled pupil, who became one of his most intimate friends, and who afterwards became Professor of Mathematics in University College, London. At that time, too, Sir John Hawkshaw, who afterwards was Prof. Tyndall’s successor as President of the British Association, was chief engineer on the Manchester and Leeds Railway, and it was in his Manchester office that Tyndall spent the last days of his railway life. A calm followed the storm of competition just described; work became scarce, and the prospects of engineers were once more overcast.

In these circumstances he accepted, in 1847, an appointment as a teacher in Queenswood College, Hampshire. The well-known Socialist reformer, Robert Owen, and his disciples built that college—a fine edifice occupying a healthy position—and called it Harmony Hall, as it was meant to inaugurate the millennium; the letters “C. of M” (commencement of millennium) being inserted in flint in the brickwork of the house. Around this college were large farms, where lessons were given by Prof. Tyndall to the more advanced students on the subjects which he had mastered in his previous labours. With teaching he combined self-improvement. The chemical laboratory was under the charge of Dr. Frankland, with whom he soon became friendly. In order to spend part of his time in study in the chemical laboratory, Tyndall relinquished part of his salary, and there he laid the foundations of that knowledge of physical science which was destined afterward to be his own passport to fame and to afford delight to many thousands of his fellowmen. He was also very successful as a teacher in Queenswood College. He is said to have exercised a kind of magnetic influence over his students, and such was their faith in him that when any disturbances arose among them he was invariably called upon to settle them, and he did so merely by the power of moral influence and force of character. As to his impressions of life at Queenswood, the Professor says:—

“Schemes like Harmony Hall look admirable upon paper; but, inasmuch as they are formed with reference to an ideal humanity, they go to pieces when brought into collision with the real one. At Queenswood, I learned, by practical experience, that two factors went to the formation of a teacher. In regard to knowledge he must, of course, be master of his work. But knowledge is not all. There might be knowledge without power—the ability to inform without the ability to stimulate. Both go together in the true teacher. A power of character must underlie and enforce the work of the intellect. There were men who could so rouse and energise their pupils—so call forth their strength and the pleasure of its exercise—as to make the hardest work agreeable. Without this power it is questionable whether the teacher could ever really enjoy his vocation—with it, I do not know a higher, nobler, and more blessed calling than that of the man who, scorning the cramming so prevalent in our day, converts the knowledge he imparts into a lever, to lift, exercise, and strengthen the growing minds committed to his care.”

After pursuing their scientific studies together for some time, both Tyndall and Frankland began to think of extending the range of their scientific culture. But that could not then be done in England. In 1845 a man could not easily get first-class instruction in practical chemistry and the other physical sciences that were then making great strides forward. Between 1840 and 1850 Germany assumed the lead in these sciences. In that country science then organised itself on a vast scale, and from that time to this it has been growing there at a most extraordinary rate; indeed, Prof. Huxley declared in 1884 that in the whole history of the world there has never been such a tremendous amount of organised energy bestowed in the development of physical science as in Germany.

“At the time here referred to,” says Professor Tyndall, “I had emerged from some years of hard labour the fortunate possessor of two or three hundred pounds. By selling my services in the dearest market during the railway madness the sum might, without dishonour, have been made a large one; but I respected ties which existed prior to the time when offers became lavish and temptation strong. I did not put my money in a napkin, but cherished the design of spending it in study at a German university. I had heard of German science, while Carlyle’s references to German philosophy and literature caused me to regard them as a kind of revelation from the gods. Accordingly, in the autumn of 1848, Frankland and I started for the land of universities, as Germany is often called. They are sown broadcast over the country, and can justly claim to be the source of an important portion of Germany’s present greatness.

“Our place of study was the town of Marburg, in Hesse-Cassel, and a very picturesque town Marburg is. It clambers pleasantly up the hillsides, and falls as pleasantly towards the Lahn. On a May day, when the orchards are in blossom, and the chestnuts clothed with their heavy foliage, Marburg is truly lovely. It is the same town in which my great namesake, when even poorer than myself, published his translation of the Bible. I lodged in the plainest manner in a street which perhaps bore an appropriate name while I dwelt there. It was called the Ketzerbach—the heretics’ brook—from a little historical rivulet running through it. I wished to keep myself clean and hardy, so I purchased a cask and had it cut in two by a carpenter. That cask, filled with spring-water over night, was placed in my small bedroom, and never during the years that I spent there, in winter or in summer, did the clock of the beautiful Elizabethekirche, which was close at hand, finish striking the hour of six in the morning before I was in my tub. For a good portion of the time I rose an hour and a-half earlier than this, working by lamp-light at the Differential Calculus when the world was slumbering around me. I risked this breach of my pursuits and this expenditure of my time and money, not because I had any definite prospect of material profit in view, but because I thought the cultivation of the intellect important; because, moreover, I loved my work, and entertained a sure and certain hope that armed with knowledge one can successfully fight one’s way through the world. I ought not to omit one additional motive by which I was upheld at the time here referred to—that was the sense of duty. Every young man of high aims must, I think, have a spice of this principle within him. There are sure to be hours in his life when his outlook will be dark, his work difficult, and his intellectual future uncertain. Over such periods, when the stimulus of success is absent, he must be carried by his sense of duty. It may not be so quick an incentive as glory, but it is a nobler one, and gives a tone to character which glory cannot impart. That unflinching devotion to work, without which no real eminence in science is now attainable, implies the writing at certain times of stern resolve upon the student’s character: ‘I work not because I like work, but because I ought to work.’ At Marburg my study was warmed by a large stove. At first I missed the gleam and sparkle from flame and ember, but I soon became accustomed to the obscure heat. At six in the morning a small milch-brod and a cup of tea were taken to me. The dinner hour was one, and for the first year or so I dined at an hotel. In those days living was cheap in Marburg. Dinner consisted of several courses, roast and boiled, and finished up with sweets and dessert. The cost was a pound a month, or about eightpence per dinner. I usually limited myself to one course, using even that in moderation, being convinced that eating too much was quite as sinful, and almost as ruinous, as drinking too much. By attending to such things I was able to work without weariness for sixteen hours a day. My going to Germany had been opposed by some of my friends as quixotic, and my life there might, perhaps, be not unfairly thus described. I did not work for money; I was not even spurred by ‘the last infirmity of noble minds.’ I had been reading Fichte, and Emerson, and Carlyle, and had been infected by the spirit of these great men, the Alpha and Omega of whose teaching was loyalty to duty. Higher knowledge and greater strength were within reach of the man who unflinchingly enacted his best insight.”

Even a statue was capable of impressing this truth upon him. But it was the statue of the man who said of his own features: “This is the face of a man who has struggled energetically”—the man of whose portrait Carlyle says: “Reader, to thee thyself, even now, he has one counsel to give, the secret of his whole poetic alchemy. Think of living! Thy life, were thou the pitifullest of all the sons of earth, is no idle dream, but a solemn reality. It is thy own; it is all thou hast to front eternity with. Work, then, even as he has done and does—Like a star, unhasting yet unresting.” Equally impressive was the effect produced on Professor Tyndall by even the sight of the form of such a man. Finding himself one fine summer evening standing beside a statue of Goethe in a German city, the contemplation of this work of art, which he considered the most suitable memorial for a great man, excited a motive force within his mind, which he thought no purely material influence could generate. “There was then,” he says, “labour before me of the most arduous kind. There were formidable practical difficulties to be overcome, and very small means wherewith to overcome them; and yet I felt that no material means could, as regards the task I had undertaken, plant within me a resolve comparable with that which the contemplation of this statue of Goethe was able to arouse.”

From his youth Tyndall appeared to have a remarkable power, not only of attracting friends, but of retaining them. The circumstances under which he early became acquainted with his life-long friends, General Wynne and Professor Hirst, have already been mentioned. Hirst was scarcely sixteen years of age when he became acquainted with Tyndall, who was ten years older. Though they stood in the relation of pupil and teacher, their intimacy ripened into an enduring friendship which separation heightened rather than dissolved. An incident that occurred while Tyndall was studying at Marburg affords honourable evidence of this fact. The death of a relative in 1849 made Hirst the possessor of a small patrimony, which he determined to divide between himself and his former teacher. He accordingly pressed Professor Tyndall to accept one half of his small fortune, but much to his disappointment Tyndall would have none of it. Entreaties to accept it for friendship’s sake were unavailing, but friendship, like necessity, can invent strange means for attaining its end. Hirst took counsel with a German banker as to a way of conveying the money to his friend, and soon a device was carried out, by means of which the devotee of science had to sacrifice his self-denial on the altar of friendship. While at work one morning in his lodgings in Marburg the postman brought him a heavy roll closely packed and sealed, which, to his astonishment, contained all sorts of German coins amounting to 20l. sterling, a considerable gratuity for a student to receive in those days. He had no alternative but to accept it. On a subsequent occasion when Tyndall left Marburg to visit England another friend of his youth, General Wynne, offered to replenish his exchequer, which he feared must be nearly empty, but the offer was declined with assurances that such generous assistance was unnecessary.

CHAPTER II.

“No man ever yet made great discoveries in Science who was not impelled by an abstracted love.”—Sir Humphry Davy.

At the time when Professor Tyndall was studying at Marburg University, the principal figure there was Bunsen, who had been appointed Professor of Chemistry in 1838. He was a profound chemist, and his fame as a lecturer was so eminent as to attract many foreign students. A prolific discoverer, and peculiarly happy in his manner of demonstrating his scientific teaching, he soon fascinated the ardent minds of the two students from Queenswood. For two years Tyndall attended his chemical lectures. Indeed he learned German chiefly by listening to Bunsen. He has himself stated that Bunsen treated him like a brother, giving his time, space, and appliances, for the benefit of his studies. The subject which most attracted Tyndall’s attention was electro-chemistry, upon which Bunsen delivered an admirable course of lectures in 1848. The whole principle of the voltaic pile was thus explained to him in a masterful manner. He also made himself acquainted with chemical analyses, both quantitative and qualitative. He displayed no less zeal in the study of mathematics. For a considerable period he got private lessons from Professor Stegmann, under whose tuition he worked through analytical geometry of two and three dimensions, the Differential and Integral Calculus, and part of the Calculus of Variations.

His first scientific paper was a mathematical essay on screw surfaces, respecting which he says:—“Professor Stegmann gave me the subject of my dissertation when I took my degree: its title in English was, ‘On a Screw Surface with Inclined Generatrix, and on the Conditions of Equilibrium on such Surfaces.’ I resolved that if I could not, without the slightest aid accomplish the work from beginning to end it should not be accomplished at all. Wandering among the pine wood and pondering the subject, I became more and more master of it; and when my dissertation was handed in to the Philosophical Faculty it did not contain a thought that was not my own.”

But the man whose acquaintance at Marburg appeared to exercise most influence over his career was Dr. Knoblauch, who had just come thither from Berlin as extraordinary Professor of Physics, and who had already distinguished himself by his researches in radiant heat. He illustrated his lectures with a choice collection of apparatus brought from Berlin; and he not only suggested to Tyndall an exhaustive series of experiments bearing on a newly-discovered principle of physics, but supplied him with the necessary apparatus, and placed his own cabinet at his disposal for that purpose. The subject of investigation was diamagnetism.

Faraday’s discoveries and experiments in magnetism were then attracting the attention of the scientific world. He had shown in 1830 that by moving a magnet within the hollow of a coil of copper wire an electrical current was produced in the wire. This was a startling and pregnant discovery. Taking six hundred feet of insulated copper wire and winding it into a large vertical coil, he arranged the two ends of the wire into a small coil a little distance away from the large coil, and immediately above this small coil he suspended a balanced compass needle by a silk thread. Then, on dropping a bar magnet, or piece of iron magnetised, into the large coil, the needle, which was pointing towards the North Pole, instantly swung round, evidently impelled by magnetic force; when, again, the bar magnet was raised out of the hollow of the large coil, the needle moved round in the opposite direction; while it remained motionless so long as the bar magnet was at rest either inside or outside the coil. It thus appeared that an electrical current could be produced by the movement of the bar magnet—by dropping it into the coil or taking it out; and the current so produced he called an induced current. This operation is called magneto-electric induction. In 1845 Faraday greatly extended his magnetic discoveries. He not only established the magnetic condition of all matter by showing that every known body or thing could be influenced by magnetism, but he discovered a new property of magnetism, which he called diamagnetism. This was considered his greatest discovery.

By suspending bodies of an elongated form between the ends or poles of powerful magnets, he found that every substance was attracted or repelled from the magnetic poles; and he divided all bodies into two great classes, called magnetic and diamagnetic. The way in which a piece of iron is attracted by the poles or ends of a horseshoe magnet is a familiar illustration of the action of magnetic bodies, and the position that such bodies assume, pointing in a line from one pole to the other, he termed axial. On the other hand, diamagnetic bodies were those which, when freely suspended within the influence of the magnet, assumed a position at right angles to the line joining the poles of a magnet, or to the magnetic meridian; in other words, magnetic bodies pointed axially from pole to pole, or north and south; while diamagnetic bodies pointed east and west, or in an equatorial direction. Bismuth is a conspicuous example of diamagnetic substances. Scientific curiosity soon became excited as to the exact nature of the diamagnetic force in relation to crystals, some of which behaved in a mysterious manner between the poles of a magnet. Professor Plücker, of Bonn, discovered that some crystals formed of diamagnetic substances were not subject to the diamagnetic force; and to account for this he attributed to crystals an optical axis, upon which the poles of a magnet exercised a peculiar force. Plücker brought this theory before the British Association in 1848, and called it a new magnetic action. At the close of the same year, Faraday told the Royal Society that he had often been embarrassed by the anomalous magnetic results given by small cylinders of bismuth, and after investigation he referred these effects to the crystalline condition of the bismuth. In concluding his lecture on this subject, Faraday said:—“How rapidly the knowledge of molecular forces grows upon us, and how strikingly every investigation tends to develop more and more their importance, and their extreme attraction as an object of study. A few years ago, magnetism was to us an occult power affecting only a few bodies: now it is found to influence all bodies, and to possess the most intimate relations with electricity, heat, chemical action, light, crystallisation, and, through it, with the forces concerned in cohesion.” He thought there was in crystals a directive impelling force distinct from the magnetic and diamagnetic force.

Frequent conversations on this subject took place between Knoblauch and Tyndall in Germany during 1849. Knoblauch suggested that Tyndall should repeat the experiments of Plücker and Faraday; and as this operation was proceeding they agreed to make a joint inquiry into the deportment of crystals under the diamagnetic force. They laboured long at the problem before attaining any encouraging success. They examined the optical properties of crystals as well as made magnetic experiments with them, a great many experiments being made without discovering any new fact. Eventually, however, they found that various crystals did not act in accordance with the principles enunciated by Plücker, and the more they worked at the subject the more clearly it appeared that the deportment of certain bodies under the influence of magnetism was due, not to the presence of some force previously unknown, but to the crystalline structure of the substance under investigation, or as Tyndall put it, to peculiarities of material aggregation. For example, he showed that while a bar of iron attracted by a magnet sets itself in a line from pole to pole, an iron bar made of an aggregate of small bars sets itself in the opposite direction. Tyndall showed that the cause of the latter bar assuming an equatorial position was simply its mechanical structure, the small plates composing the “aggregated” bar setting from pole to pole. He found that the same law regulated the magnetic deportment of crystals, whose mechanism or structure, however, was generally less evident.

In 1849 eminent natural philosophers were studying this subject in England, France, and Germany, and it was expected that the investigation of diamagnetic phenomena would rapidly throw some new light upon the molecular forces which determine the conditions of the material creation. In allusion to this expectation, Tyndall said in 1850, that as nature acts by general laws, to which the terms great and small are unknown, it cannot be doubted that the modifications of magnetic force, exhibited by bits of copperas and sugar in the magnetic field, display themselves on a large scale in the crust of the earth itself, and as a lump of stratified grit, though a magnetic material, could be made, on account of its planes of stratification, to act as if it were diamagnetic, he suggested that this element might have some influence in determining the varying position of the magnetic poles of the earth—a subject which still perplexes the scientific world. Not only has the north magnetic pole gradually been changing its position, as shown by the records of three centuries, but, according to Barlow, every place has a magnetic pole and equator of its own; and according to Faraday the earth is a great magnet, whose power, as estimated by Gauss, is equal to that which would be conferred if every cubic yard of it contained six one-pound magnets; the sum of the force being thus equal to 8,464,000,000,000,000,000,000 such magnets. “The disposition of this magnetic force is not regular,” said Faraday, “nor are there any points on the surface which can be properly called poles: still the regions of polarity are in high north and south latitudes; and these are connected by lines of magnetic force (being the lines of direction), which, generally speaking, rise out of the earth in one (magnetic) hemisphere, and passing in various directions over the equatorial regions into the other hemisphere, there enter into the earth to complete the known circuit of power.”

It was in connection with his investigations on this subject that Prof. Tyndall first saw Prof. Faraday. Returning from Marburg in 1850, he called at the Royal Institution and sent in his card, together with a copy of a paper he had prepared, giving the results of his experiments on magne-crystallic action. Prof. Faraday conversed with him for half-an-hour, and being then on the point of publishing one of his papers on magne-crystallic action, he appended to it a flattering reference to the notes which Tyndall had placed in his hands.

Tyndall went back to Germany, where he worked for another year. In the beginning of 1851 he went to Berlin, where, he says, Prof. Magnus had made his name famous by physical researches of all kinds. “On April 28th, 1851, I first saw this Professor on his own doorstep in Berlin. His aspect won my immediate regard, which was strengthened to affection by our subsequent intercourse. He gave me a working place in his laboratory, and it was there I carried out my investigations on diamagnetism and magnecrystallic action published in the Philosophical Magazine for September, 1851. Among the other eminent scientific men whom I met at Berlin was Ehrenberg, with whom I had various conversations on microscopic organisms. I also made the acquaintance of Riess, the foremost exponent of frictional electricity, who more than once opposed to Faraday’s radicalism his own conservatism as regarded electric theory. Du Bois-Reymond was there at the time, full of power, both physical and mental. His fame had been everywhere noised abroad in connection with his researches on animal electricity. Du Bois-Reymond became perpetual secretary to the Academy of Sciences, Berlin. From Professor Magnus, and from Clausius, Wiedemann, and Poggendorff, I received every mark of kindness, and formed with some of them enduring friendships. Helmholtz was at this time in Königsberg. He had written his renowned essay on the “Conservation of Energy,” which I afterward translated. Helmholtz had, too, just finished his experiments on the velocity of nervous transmission, proving this velocity, which had previously been regarded as instantaneous, or, at all events, as equal to that of electricity, to be, in the nerves of the frog, only 93 ft. a second, or about one-twelfth of the velocity of sound in air of the ordinary temperature. In his own house I had the honour of an interview with Humboldt. He rallied me on having contracted the habit of smoking in Germany, his knowledge on this head being derived from my little paper on a water-jet, where the noise produced by the rupture of a film between the wet lips of a smoker is referred to. He gave me various messages to Faraday, declaring his belief that he (Faraday) had referred the annual and diurnal variation of the declination of the magnetic needle to their true cause—the variation of the magnetic condition of the oxygen of the atmosphere. I was interested to learn from Humboldt himself that, though so large a portion of his life had been spent in France, he never published a French essay without having it first revised by a Frenchman. In those days I not unfrequently found it necessary to subject myself to a process which I called depolarisation. My brain, intent on its subjects, used to acquire a set, resembling the rigid polarity of a steel magnet. It lost the pliancy needful for free conversation, and to recover this I used to walk occasionally to Charlottenburg or elsewhere. From my experiences at that time I derived the notion that hard thinking and fleet talking do not run together.”

Prof. Tyndall was exceptionally fortunate in getting so easily and so early into the friendship of such eminent men of science. In those days to form such eminent acquaintances was no small achievement for a young Irishman; but on the other hand, he had fully earned this distinction by the vigour and originality with which he attacked the latest and most perplexing problem of that time. During the five years that had elapsed since Faraday discovered diamagnetism, the subject had been investigated by the greatest scientists in England, France, and Germany, and no one had done so much to elucidate it as Prof. Tyndall. In order to master that subject he began in November, 1850, an investigation of the laws of magnetic attractions. The laws of magnetic action at distances in comparison with which the thickness of the magnet vanishes, had long been known, but the laws of magnetic action at short distances, where the thickness of the magnet comes fully into play, had not previously been subjected to reliable experiments, and were therefore at that time a perplexing matter of speculation. That desideratum he now supplied. He found, among other things, that the mutual attraction of a magnet and a sphere of soft iron, when both are separated by a small fixed distance, is directly proportional to the square of the strength of the magnet, and that the mutual attraction of a magnet of constant strength and a sphere of soft iron is inversely proportional to the distance between them.

Next year (1851) he published the results of further investigations into the relations between magnetism and diamagnetism. He found that the laws which govern magnetism and diamagnetism are identical, that the superior attraction or repulsion of a mass in any particular direction is due to the direction in which the material particles are arranged most closely together, that the forces exerted are attractive or repulsive according as the particles are magnetic or diamagnetic, and that this law is applicable to matter in general.

A paper on “The Polarity of Bismuth,” which might be regarded as a temporary instalment of his diamagnetic researches, ended with the remark that during this inquiry he had changed his mind too often to be over-confident now in the conclusion at which he had arrived. Part of the time he was a hearty subscriber to the opinion of Faraday that there existed no proof of diamagnetic polarity; and if, he said, “I now differ from that great man, it is with an honest wish to be set right, if through any unconscious bias of my own I have been led either into errors of reasoning or mis-statements of fact.”

The theory of diamagnetism was still an apple of discord in the scientific world; and although Prof. Tyndall used the language of deference rather than of doubt, he did not allow the subject to remain in a state of uncertainty. He continued his researches in Berlin, in the private laboratory of Prof. Magnus, who afforded him every possible facility for carrying on experiments, and took a lively interest in the investigation. The result was the confirmation of his previous impression that the action of crystals within the range of a magnet’s influence (technically called the “magnetic field”) was due to peculiarities of molecular arrangement. He found, for example, that a crystal of carbonate of iron, which, when suspended in the magnetic field, showed a certain deportment, could be pounded into the finest dust, and the particles could be so put together again that the mass would exhibit the same deportment as before.

Dr. Bence Jones, the Secretary of the Royal Institution, who had heard of Tyndall in Berlin in 1851, afterwards invited him to give a Friday evening lecture at the Royal Institution. “I went,” he says, “not without fear and trembling, for the Royal Institution was to me a kind of dragon’s den, where tact and strength would be necessary to save me from destruction.” The lecture, which was delivered on February 11th, 1853, was “On the Influence of Material Aggregation upon the Manifestations of Force,” and it gave a beautiful and simple exposition of the principles of magnetic and diamagnetic action discovered by himself, the chief being that the line of greatest density is that of strongest magnetic power. In the course of his lecture he pointed out that anything which increases density increases magnetic power; and upon that principle he contended that the local action of the sun upon the earth’s crust must influence in some degree the diurnal range of the magnetic needle, which Faraday, on the other hand, attributed to the modification of our atmosphere by the sun’s rays. While thus endeavouring to upset Faraday’s theory, he concluded by saying: “This evening’s discourse is, in some measure, connected with this locality, and thinking thus, I am led to inquire wherein the true value of a scientific discovery consists? Not in its immediate results alone, but in the prospect which it opens to intellectual activity, in the hopes which it excites, in the vigour which it awakens. The discovery which led to the results brought before you to-night was of this character. That magnet was the physical birthplace of these results; and if they possess any value they are to be regarded as the returning crumbs of that bread which in 1846 was cast so liberally upon the waters. I rejoice in the opportunity here afforded me of offering my tribute to the greatest worker of the age, and of laying some of the blossoms of that prolific tree which he planted at the feet of the great discoverer of diamagnetism.” At the conclusion of the lecture Faraday quitted his usual seat, and crossing the theatre to the corner where the lecturer stood, cordially shook him by the hand and congratulated him on his success. A second lecture was delivered by him on June 3rd, 1853, “On some of the Eruptive Phenomena of Iceland,” and a month later he was unanimously elected Professor of Natural Philosophy in the Royal Institution.

Some years previously he had read in a serial publication an account of Davy’s experiments on radiant heat at the Royal Institution, and he remembered ever after the longing then excited in him to be able to do something of the same kind. Now he was to occupy a position in which he should use, in his own lectures, the same apparatus of which illustrations were given in the magazine article that had fired his youthful ambition. To that position he was promoted on the recommendation of Faraday, and respecting his appointment he himself said: “I was tempted at the time to go elsewhere, but a strong attraction drew me here. It was his (Faraday’s) friendship that caused me to value my position here more highly than any other.”

While the controversy respecting magnetic and diamagnetic hypotheses was still raging, Faraday delivered a lecture at the Royal Institution early in 1855 with the express object of cautioning the investigators of scientific truths against placing too much confidence on any hypothesis. He stated that every year of increased experience had taught him more and more to distrust the theories he had once adhered to; and his present impression with regard to existing Magnetic and Electrical hypotheses was, that they were very unsatisfactory, and that the propounders of them had been following in a wrong track. As an instance of the obstacles which erroneous hypotheses throw in the way of scientific discovery, he mentioned the unsuccessful attempts that had been made in this country to educe magnetism from electricity, until Oersted showed the simple way. He said that the identity of magnetism and electricity had been strongly impressed upon the minds of all: when he came to the Royal Institution, as an assistant in the laboratory, he saw Davy, Wollaston, and Young trying by every way that suggested itself to them to produce magnetic effects from an electric current; but, having their minds diverted from the true course by their existing hypotheses, it did not occur to them to solve the point by holding a wire, through which an electric current was passing, over a suspended magnetic needle—the experiment by which Oersted afterwards proved, by the deflection of the needle, the magnetic property of an electric current.

Such cautions, however, did not deter Professor Tyndall from defending the position he had taken up with regard to magnetism and diamagnetism. He still maintained that the influence of structure was supremely important,—that under the influence of magnetism or electricity a normal diamagnetic bar always exhibits a deportment precisely antithetical to that of a normal magnetic bar; but that, by taking advantage of structure, it is possible to get diamagnetic bars which exhibit precisely the same deportment as normal magnetic ones, and magnetic bars which exhibit a deportment precisely similar to normal diamagnetic ones. He showed numerous experiments before the British Association in support of his contention that the diamagnetic force is a polar one, with a direction opposite to that of the force in ordinary magnetic bodies. Professor William Thomson, who witnessed the experiments, certified the success of every one of them; and stated that Professor Tyndall’s discoveries in this domain of science had cleared away a mass of rubbish and set things in their true light, adding that in many cases he had repeated and varied Tyndall’s experiments, and had found them to be true.

In 1855 he delivered the Bakerian lecture, in which he gave an elaborate account of his latest researches respecting the phenomena of diamagnetism. He was now firmly convinced, he said, that the force that repelled a body was similar in character to that which attracted a body; in other words, that diamagnetic bodies possess the same kind of polarity, but in the opposite direction to that of magnetic bodies. But the opponents of diamagnetic polarity, who were not yet satisfied by the evidence he adduced, said that his experiments were made with electrical conductors in which induced currents could be formed that might account for the attractions and repulsions. Professor Tyndall thought it would tend to settle the question if he were to use a new kind of apparatus that would obviate that objection. He therefore wrote to Professor Weber, of Göttingen, whom Professor William Thomson described at the time as the most profound and accurate of all experimenters, asking him to devise more delicate and powerful means than had hitherto been used in experimental tests. Weber not only devised a greatly improved apparatus, but had it constructed under his own superintendence at Leipsig.[2] With this apparatus Professor Tyndall was able to satisfy the severest conditions proposed by those who discredited the results of previous experiments. He then silenced doubt by demonstrating that magnetism and diamagnetism stand, in respect of polarity, on the same footing, with this difference, that the one polarity is the inversion of the other. This diamagnetic polarity, previously established in the case of bismuth, he showed to exist in slate, marble, calcspar, sulphur, &c. He also established the polarity of liquids, magnetic and diamagnetic. At the Royal Institution in February, 1856, he showed that prisms of the same heavy glass as that with which Faraday discovered the diamagnetic force, behaved under the magnet in the same way as bismuth; and this evidence was admitted to be conclusive by the opponents of diamagnetic polarity. The controversy thereafter subsided.

His chief papers recording his most important investigations in connection with diamagnetism were afterwards collected into a volume entitled Researches on Diamagnetism and Magnecrystallic Action.

In 1855 Professor Tyndall was appointed Examiner under the Council for Military Education, and an incident which occurred shortly afterwards illustrated the confidential relations into which his intimacy with Faraday had ripened, as well as the independence of character which distinguished both. Being strongly impressed with the advantage of increasing the knowledge of physical science given to artillery officers and engineers, Professor Tyndall advocated a more liberal recognition of scientific attainments in their examinations. At that time a committee of the British Association was endeavouring to get the British Government to recognise the claims of science; and in reply to inquiries made by that committee as to the expediency of offering inducements for the acquisition of science and of offering orders and decorations as rewards for proficiency, Professor Faraday said: “I cannot say that I have not valued such distinctions; on the contrary, I esteem them very highly; but I don’t think I have ever worked for, or sought after, them.” Lord Harrowby, in his address as President of the British Association, said that the State had till recently done absolutely nothing for the promotion of science; and it was remarked as a strange circumstance that though there were then in the Cabinet the President and President-elect of the British Association, it was considered too hazardous to apply to the Government for money for scientific purposes. While this neglect of science was being freely discussed a number of well-instructed young men were sent from Trinity College, Dublin, to compete at the Woolwich examinations in 1856 for appointments in the artillery and engineers, and their scientific knowledge appeared so creditable that Professor Tyndall thought it unnecessary to say anything about it. His colleagues, on the other hand, sent in as usual brief reports with their returns calling attention to the chief features of the examination, and a leader in the Times pointed out that the concurrent testimony of the examiners was that, both in mathematics and classics, the candidates showed a marked improvement, but that on other points they broke down. This appeared to Professor Tyndall an unjust reflection upon their scientific attainments, which were thus ignored. He accordingly wrote to the Times simply stating that “in justice to the candidates for commissions in the artillery and engineers examined by me in natural philosophy and chemistry, you will perhaps permit me to state that the general level of the answers in the last examination was much higher than that attained in the first; many of the papers returned to me gave evidence of rare ability, and if during their future career the authors of these papers continue to cultivate the powers which they have shown themselves to possess, they will, I doubt not, justify by their deeds the high opinion entertained of them.” This modest statement, intended to put the students right, put himself wrong. The Secretary of State for War promptly informed him that an examiner appointed by the Commander-in-Chief had no right to appear in the public papers as Professor Tyndall had done without the sanction of the War Office. To this reproof he at once wrote a firm but respectful reply, which, however, he submitted to Faraday before despatching it. Faraday pointed out that the consequence of sending such a reply would be dismissal. Professor Tyndall said he knew that, but he would not silently accept the reproof of the War Office. “Then send the reply,” said Faraday; and it was sent. Henceforth Professor Tyndall was in daily expectation of receiving his discharge. After a delay, the length of which surprised him, he received a reply, the contents of which still more surprised him. His explanation was “deemed perfectly satisfactory” by the Secretary for War, and he therefore continued for many years afterwards in the service of the Council for Military Education.

One of the next subjects that occupied his attention was the cleavage of slate rocks. It is a question of great importance in connection with geological problems, and hitherto only speculative solutions had been offered of what appeared to be one of the most mysterious but grandest operations of nature. For twenty years previously geologists were mostly content to accept on trust the suggestion of Professor Sedgwick, that crystalline forces had rearranged whole mountain masses so as to produce a beautiful crystalline cleavage. In 1854 Professor Tyndall visited the quarries of Cumberland and North Wales, where the question of cleavage came prominently before him. When at Penrhyn Quarry he was told that the planes of cleavage were the planes of stratification lifted up by some convulsion into an almost vertical position. But a little observation satisfied him that this view was essentially incorrect; for in certain masses of slate in which the strata were distinctly marked, the planes of cleavage were at a high angle to the planes of stratification. A little experiment, he said, demonstrated that the cleavage of slate was no more a crystalline cleavage than that of a hayrick. An elaborate examination of all the conditions of the phenomena led him to the conclusion that cleavage was the result of pressure, and that this effect of pressure was not confined to slates. In a lecture delivered in 1856 he stated that for the previous twelve months the subject had presented itself to him almost daily under one aspect or another. “I have never,” he said, “eaten a biscuit during this period in which an intellectual joy has not been superadded to the more sensual pleasure, for I have remarked in all such cases cleavage developed in the mass by the rolling-pin of the pastrycook or confectioner. I have only to break these cakes and to look at the fracture to see the laminated structure of the mass.” He exhibited some puff-paste baked under his own superintendence, and explained that while the cleavage of our hills was accidental, in the pastry it was intentional.

Among those who heard the lecture upon slaty cleavage was his friend Professor Huxley, who suggested that probably the principles then enunciated might account for the structure of glaciers, another subject that had long perplexed scientific observers. The greatest authority on glaciers at that time was Professor J. D. Forbes, of Edinburgh University, who in 1842 declared that a “glacier is an imperfect fluid or viscous body, which is urged down slopes of a certain inclination by the mutual pressure of its parts,” and who detected in glaciers a veined structure which he explained as fissures produced by particles of ice in motion sliding past each other, leaving the fissures to be filled with water and to be frozen in winter. On examining the published observations of Forbes, Professor Tyndall was struck with the probable accuracy of Professor Huxley’s suggestion, and in order to examine the matter more thoroughly, the two advocates of the cleavage theory arranged to visit together the glaciers of Grindelwald, the Aar, and the Rhone. This personal investigation and subsequent reflection confirmed Professor Tyndall in his views. He found that glaciers were formed by the property of ice which Faraday called regelation; that is, the freezing together of two pieces of ice by simple contact and slight pressure. It is the same property that enables boys to make snowballs and snow men when the snow is beginning to melt, or when the warmth of the hand raises its temperature to the point at which regelation takes place. Professor Tyndall found that when two confluent glaciers united to form a single trunk, their mutual pressure developed the veined structure in a striking degree along their line of junction. In his lectures on the subject at the Royal Institution he ingeniously illustrated the processes of Nature which make and unmake the glacier. To show that ice only becomes compressed into a solid mass at a temperature near that of freezing water, he cooled a mass of ice by exposing it to the action of the coldest freezing mixture then known. He then crushed this cooled mass of ice into fragments, and applied pressure to the fragments for the purpose of making them cohere, but they did not show the slightest cohesiveness. Very different was their action when their temperature was raised to the freezing point. When placed in a wooden cup and pressed by a hollow wooden die a size smaller than the cup, the pieces of ice became united into a compact cup of nearly transparent ice. Glaciers, he contended, were formed by a similar operation. As particles of snow or ice descend the mountain side, the pressure becomes sufficiently great to compress the particles into a mass of solid ice, which eventually assumes the magnitude of a beautiful glacier. He observed that in the laboratory of Nature it was exactly at the places where squeezing took place that the cleavage of the ice was most highly developed. In fact, he said, the association of pressure and lamination was far more distinct in the case of the glacier than in the case of the slate rock, and as it was now known that pressure caused the lamination of slate rock, he contended that it was the same cause that produced like effects in glaciers.

In a lecture delivered early in 1858, he gave an account of some beautiful phenomena of the glacier. In the preceding September and October he examined the effect of sending a beam of radiant heat through a mass of ice. When sunbeams condensed by a lens were sent through slabs of ice, the path of the beam was instantly studded with lustrous spots like brilliant stars, and “around each the ice was so liquefied as to form a beautiful flower-shaped figure, possessing six petals. From this number there was no deviation. At first the edges of the liquid leaves were clearly defined: but a continuance of the action usually caused the edges to become serrated like those of ferns. When the ice was caused to move across the beam, or the reverse, the sudden generation and crowding together of these liquid flowers, with their central spots shining with more than metallic brilliancy, was exceedingly beautiful.” By means of the electric light and a piece of ice prepared for the purpose he was able to exhibit these lovely ice-flowers to a delighted audience at the Royal Institution.

During the years 1857 and 1858 Professor Tyndall continued his observations of glacier phenomena amid the solitude of the Alps. In the summer of the latter year he betook himself to the mountains with the view of settling once for all “the rival claims of the only two theories, which then deserved serious attention, namely, those of pressure and of stratification.” Again his former views were completely confirmed. It is difficult, he said, to convey in words the force of the evidence which the glacier of Grindelwald presents to the mind of the observer who sees it; it looked like a grand laboratory experiment made by Nature herself with special reference to the point in question. The squeezing of the mass, its yielding to the force brought to bear upon it, its wrinkling and scaling off, and the appearance of the veins at the exact point where the pressure began to manifest itself, left no doubt on his mind that pressure and structure stood to each other in the relation of cause and effect.

The conclusions at which he arrived as to the structure and movement of glaciers brought him into collision with Professor Forbes, whose views, enunciated fifteen years previously, were then widely accepted as the most scientific exposition of the subject. Forbes seemed rather sensitive about his own theory, and complained that he had to some extent been misrepresented. But in the conflict of opinions Professor Tyndall invariably referred to Professor Forbes’s labours in connection with the subject in the most appreciative and complimentary language. For instance, in 1858 he said he would not content himself with saying that the book of Professor Forbes was the best that had been written upon the subject; “the qualities of mind, and the physical culture invested in that excellent work, were such as to make it, in the estimation of the physical investigator at least, outweigh all other books upon the subject taken together.” That is more generous language than Professor Forbes ever used respecting Professor Tyndall. In 1865, after the heat of controversy had been dissipated, Forbes wrote that “Dr. Tyndall’s so-called proofs that it is through ‘fracture and regelation’ that a glacier moulds itself to its bed are to my mind no proofs at all;” and that he regarded Mr. Hopkins’s mathematical demonstrations about glaciers as “irrelevant mathematical exercitations.” Nevertheless, Professor Tait, the friend and scientific biographer of Forbes, said in 1873: “To say that Forbes thoroughly explained the behaviour of glaciers would be an exaggeration; but he must be allowed the great credit of being the Copernicus or Kepler of this science.” As the subject still continues to exercise the intellect of the scientific explorers of the Alps, suffice it for the present to say that if time ratifies the position which Professor Tait has assigned to Professor Forbes, his greatest and boldest successor in the same field may be described as the Newton of glacier phenomena.