Lectures on Ten British Physicists of the Nineteenth Century/Lecture 3
(1831-1901)
Peter Guthrie Tait was born at Dalkeith, near Edinburgh, Scotland, on the 28th of April, 1831. His father was then private secretary to the Duke of Buccleuch, afterwards, I believe, a bookseller and the publisher of a monthly called Tait's Magazine. Peter Guthrie was educated at the Grammar School of Dalkeith, then at the Circus Place School in Edinburgh, and eventually at the Edinburgh Academy, where he had Maxwell for a classmate. Of equal age and similar genius they were drawn into close friendship. They left the Academy together, and took up the same classes of mathematics and physics at the University of Edinburgh. But while Maxwell continued in his studies there for three years, and drank deeply of philosophy and natural science as well as of mathematics and physics, Tait left after one brief session for the University of Cambridge. I dare say had Tait studied philosophy and natural science as Maxwell did, his writings would have been more logical, and his mental makeup less eccentric.
When he entered Peterhouse College, Cambridge, he was 18 years of age. His private tutor was William Hopkins the most successful coach of his time. He graduated as senior wrangler in 1852, and was also first Smith's prizeman. He was immediately made a mathematical tutor to his college, and very soon a Fellow. The second wrangler and second Smith's prizeman of the same year was W. J. Steele, an intimate friend of Tait. The two friends proceeded forthwith to prepare in conjunction a treatise called Dynamics of a Particle; but Steele lived to write only a few chapters. The book was first published in 1856, and has gone through a number of editions, Steele's name remaining on the title page. Two years after graduation he was appointed professor of mathematics in the Queen's College, Belfast. Then, if not before, he became acquainted with Andrews, the professor of chemistry and vice-president of the college; a skillful experimenter, famous for his researches on the nature of ozone and on the compression of gases. It is doubtful whether Tait did any experimenting under Forbes at Edinburgh; Andiews appears to have been his guide and master in physical manipulation.
In 1853, one year after Tait's appointment at Belfast, Hamilton published his Lectures on Quaternions. The young professor had a great power of doing work; in the day time he taught mathematics and experimented with Andrews; and at night he studied the new method of Quaternions. He soon mastered it sufficiently to be able to write papers on it, which, lie published in the Messenger of Mathematics and the Quarterly Journal of Mathematics and eventually he planned a volume of examples on Quaternions. There were, however, to Tait's mind numerous obscure points in the theory, and to elucidate them he wished to correspond with Hamilton directly. His friend Andrews wrote to Hamilton asking the favor; in this way a correspondence originated which was kept up till the death of Hamilton. In 1859 Hamilton met Tait at the British Association meeting at Aberdeen, and Tait introduced another disciple, Clerk Maxwell, then professor of physics at Aberdeen. The year following Professor Forbes resigned the chair of physics in Edinburgh University; the former schoolmates, Tait and Maxwell, were both candidates; the choice of the electors fell on the energetic professor of mathematics at Belfast. This contest, it is pleasant to say, did not diminish the friendship between the two mathematicians. In his letter Tait used the symbol for Maxwell, because in thermodynamics there is the equation Maxwell addressed one of his odes to Tait as "The chief musician upon Nabla."
Tait's Quaternion project had now developed into a formal introduction to Quaternions; an announcement of the forthcoming book appeared soon after Tait removed to Edinburgh. He had now ceased to teach pure mathematics; he and Prof. William Thomson had sketched out an elaborate treatise on natural philosophy in four volumes'; for which reasons he was anxious to have the Quaternion volume off his hands. Sir William Hamilton was then engaged in the preparation of his "Elements of Quaternions" and he did not like the idea of Tait's book appearing before his own. He did not object to examples, but he wished to have the priority in all matters of principle. Tait, hearing of the situation, offered of his own accord to delay the publication of his volume until the Hamilton's Elements should have appeared. To arrange the matter more definitely Tait made a visit to Dunsink Observatory, Dublin, in the summer of 1861. Hamilton expected to publish before the end of the year, and asked Tait to wait till the year following. But the printing of Hamilton's book went on for four years longer, and was stopped only by Hamilton's death in 1865. It was published, incomplete, in 1866; and true to his promise Tait did not publish till 1867. The work then given to the public was entitled an Elementary Treatise on Quaternions. The articles which deal with the theory of Quaternions have always presented numerous difficulties to the reader; this phenomenon is explained partly by the history of the volume, and especially by Hamilton's desire that Tait should confine the work to applications. I think it unfortunate that Hamilton adopted such an attitude. It was a mistake to present the method in such tremendous volumes as the Lectures and the Elements; it was a mistake to retard the publication of Tait's volume; it was a mistake to reserve the discussion of principles and of notation. Unfortunately, Tait, in his turn, advised inquirers to leave principles and notation alone and go on to applications, from which it has come about that the method of quaternions, presenting as it does, many points of novelty to the mathematician, has never been adequately discussed; only a few have looked upon it as a very important subject for discussion. When Tait became professor of physics at Edinburgh University, laboratory teaching of physics was unknown in Scotland. It had been Forbes' custom to allow now and then a promising pupil such as Maxwell the use of the lecture apparatus, and in this as in many other customs he was followed by Tait. About ten years later Prof. Tait, following the example of Prof. Sir William Thomson of Glasgow, instituted a practical class. It was his idea that each student, taking that class, should be instructed how to make a series of measurements, and then should try some real experimental problem. Prior to the founding of the Cavendish Laboratory at Cambridge, the facilities at Edinburgh and Glasgow for gaining an experimental knowledge of physics were the best in Great Britain and this was due to the circumstance that in these twin cities of the North, the chairs of physics were occupied by twin giants in physical science. At the Scottish Universities the academic classes meet only in the winter for six months; the medical and other professional classes have a summer session in addition. In the winter session Tait lectured five times a week to the academic students, about 200 in number, and endeavored to traverse the whole range of elementary physics. Every other Saturday there was a one-hour examination; at which, following a custom of his predecessor, he did not give out printed questions, nor write them on a board, but dictated them at uniform intervals of five minutes. Having propounded his problem Tait grinned with satisfaction; if a member of the class asked a question about it Tait reminded him that he had changed for the time being from a benevolent teacher into a relentless inquisitor. The papers were afterwards returned marked with i or o or ———, the length of the dash indicating the degree of imperfection.
To help those who wished to make a more thorough study of physics he instituted an advanced class; at this work he appeared to the greatest advantage. Before entering the lecture-room he glanced for a short time at his notes; thereafter he would write out mathematical equations for an hour without referring to any notes whatever. It was astonishing to see the way in which he could " sling " the symbols. Tait was not only an intellectual, but likewise a physical, giant. I am nearly six feet high, but standing beside Tait, I used to feel diminutive. He was well-built, and muscular. He wore a long beard, the hair on the top of his -head had disappeared at an early date, and left exposed a massive forehead. To protect his head while lecturing it was his custom to wear a skull cap. On the street he wore a sack-coat and a soft felt hat, and with cane in hand, was always walking rapidly. About the time of his moving to Edinburgh he married a lady who proved a genuine helpmate. She took full charge of all the affairs of the household, so that her distinguished husband might have perfect leisure for his scientific labors; and her influence was also such as to steady his attachment to religion.
Before the year 1860, when Tait became a professor of physics, Joule had made his determination of the mechanical equivalent of heat, thus establishing the first law of thermodynamics; Thomson, Rankine and Clausius had established the second law; and Rankine had drawn the outlines of the science of "energetics." In the first edition of Dynamics of a Particle there is no mention of the doctrines of energy; it is probable that Tait's experimental work with Andrews led him to study the papers of Thomson, Joule and Rankine. Anyhow the main object of Thomson and Tait's Treatise on Natural Philosophy was to fill up Rankine's outlines, expound all the branches of physics from the standpoint of the doctrine of energy. The plan contemplated four volumes; the printing of the first volume began in 1862 and was completed in 1867. The other three volumes never appeared. When a second edition was called for, the matter of the first volume was increased by a number of appendices and appeared as two separately bound parts. The volume which did appear, although judged rather difficult reading even by accomplished mathematicians, has achieved a great success. It has been translated in French and German; it has educated the new generation of mathematical physicists; and it has been styled the "Principia" of the nineteenth century. Such was his admiration of Newton that Tait I am sure could not conceive of any higher compliment. Maxwell had facetiously referred to Thomson as T and to Tait as T1. Hence the Treatise on Natural Philosophy came to be commonly referred to as T and T1 in the conversation of mathematicians.
It appears that the introduction of the quaternion method was a serious point of difference between the joint authors. Prof. Thomson, as you know, subsequently became Lord Kelvin and recently he wrote to Prof. Chrystal as follows with respect to the joint authorship of the Treatise. "I first became personally acquainted with Tait a short time before he was elected professor in Edinburgh; but, I believe, not before he became a candidate for the chair. It must have been either before his election or very soon after it that we entered on the project of a joint treatise of natural philosophy. He was then strongly impressed with the fundamental importance of Joule's work, and was full of vivid interest in all that he had learned from and worked at, with Andrews. We incessantly talked over the mode of dealing with energy which we adopted in the book, and we went most cordially together in the whole affair. He gave me a free hand in respect to names, and warmly welcomed nearly all of them. We have had a thirty-eight years' war over quaternions. He had been captivated by the originality and extraordinary beauty of Hamilton's genius in this respect, and had accepted, I believe, definitely, from Hamilton to take charge of quaternions after his death, which he has most loyally executed. Times without number I offered to let quaternions into Thomson and Tait, if he could only show that in any case our work would be helped by their use. You will see that from beginning to end they were never introduced."
In 1864 Tait published in the North British Review articles on "The dynamical theory of heat" and "Energy" which were afterwards made the basis of his Sketch of Thermodynamics published in 1868. The articles, mainly historical, are written from the British point of view, so much so, that he was accused of Chauvinism. To this charge he replied, "I cannot pretend to absolute accuracy, but I have taken every means of ensuring it, to the best of my ability, though it is possible that circumstances may have led me to regard the question from a somewhat too British point of view. But, even supposing this to be the case, it appears to me that unless contemporary history be written with some little partiality, it will be impossible for the future historian to compile from the works of the present day a complete and unbiased statement. Are not both judge and jury greatly assisted to a correct verdict by the avowedly partial statements of rival pleaders? If not, where is the use of counsel?"
A German physician named Mayer was struck by the amount of heat developed in the team of horses which pulled the stagecoach into his village; and he reflected on the connection between the amount of heat developed and the amount of work they 'had done. From this as a starting point he was led to investigate the nature of heat, and he arrived at the now accepted doctrine that heat is a motion of the small parts of bodies. He sought after the exact mechanical equivalent of heat, and was able to deduce it by calculation from determinations of the specific heat and some other properties of air. He had not the means for making any experiments. Tait pointed out defects in Mayer's reasoning, and minimized his contribution, because he had not made any experiments. Prof, von Helmholtz, in reply, pointed out that Mayer was not in a position to make experiments; that he was repulsed by the physicists with whom he was acquainted; that he could scarcely procure space for the publication of his paper; and that in consequence of these repulses his mind at last became affected. Tait felt that he had been taking a rather ungracious attitude towards one who had suffered much for the sake of truth in science.
It cannot be denied that Chauvinism was one of the eccentric characteristics of Prof. Tait. He had never studied on the Continent; he never traveled, I believe, beyond the narrow confines of the British Islands; and in his later years, he became something of a. recluse. What he said of the life of Rankine, applied with still greater force to his own. "The life of a genuine scientific man is, from the common point of view, almost always uneventful. Engrossed with the paramount claims of inquiries raised high above the domain of mere human passions, he is with difficulty tempted to come forward in political discussions even when they are of national importance, and he regards with surprise, if not with contempt, the petty municipal squabbles in which local notoriety is so eagerly sought. To him the discovery of a new law of nature, or even of a new experimental fact, or the invention of a novel mathematical method, no matter who has been the first to reach it, is an event of an order altogether different from, and higher than, those which are so profusely chronicled in the newspaper. It is something true and good forever, not a mere temporary outcome of craft or expediency. With few exceptions, such men pass through life unnoticed by, almost unknown to, the mass of even their educated countrymen. Yet it is they who, far more than any autocrats or statesmen, are really molding the history of the times to come. Man has been left entirely to himself in the struggle for creature comforts, as well as for the higher appliances which advance civilization; and it is to science, and not to so-called statecraft, that he must look for such things. Science can, and does, provide the means; statecraft can but more or less judiciously promote, regulate or forbid their use or abuse. One is the lavish and utterly unselfish furnisher of material good; the other the too often churlish and ignorant dispenser of it."
His next book was written in conjunction with Prof. Kelland, An Introduction to Quaternions, 1873. Kelland was the professor of mathematics, and it was his custom to expound to his senior class the elements of quaternions along with advanced algebra. Tait, so far as I know, never lectured on the subject at the University of Edinburgh. The volume in question grew out of Kelland's lectures, and was revised and supplemented by Tait. Kelland was much the older man, and had stood to Tait in the relation of instructor. In the preface, which was written by Kelland, light is thrown on the relation between the joint authors and colleagues: "The preface I have written," Kelland says, "without consulting my colleagues, as I am thus enabled to say what could not otherwise have been said, that mathematicians owe a lasting debt of gratitude to Prof. Tait for the singleness of purpose and the self-denying zeal with which he has worked out the designs of his friend Sir William Hamilton, preferring always the claims of the science and of its founder to the assertion of his own power and originality in its development. For my own part I must confess that my knowledge of Quaternions is due exclusively to him. The first work of Sir William Hamilton—Lectures on Quaternions—was very dimly and imperfectly understood by me and I dare say by others, until Prof. Tait published his papers on the subject in the Messenger of Mathematics. Then, and not till then, did the science in all its simplicity develop itself to me."
Tait had now co-operated with Steele in writing Dynamics of a Particle, with Thomson in a Treatise on Natural Philosophy, and with Kelland in the Introduction to Quaternions. There was still a fourth literary partnership to follow; this time with Balfour Stewart, professor of physics at the Owens College, Manchester. In 1875 a volume called The Unseen Universe, having as a sub-title "Physical Speculations on a Future State" appeared anonymously; but to a physicist it was evidently inspired by Tait's Sketch of Thermodynamics and Stewart's book The Conservation of Energy. It was asserted in the Academy that Tait and Stewart were the authors; and a subsequent edition appeared with their names on the title page. It was to most people a matter of surprise that one who had been denouncing metaphysics in season and out of season, should turn out to be part author of a book described as "physical speculations on a future state." Did not Kant say that the three problems of metaphysics are God, freedom, and immortality? What is metaphysics but speculation based upon physical science concerning things which can never be reached directly by the methods of physics? The Unseen Universe was metaphysics of the best or worst (however you may view it) kind; it was full of Carnot's reversible engine, the mechanical equivalent of heat, vortex-atoms and so forth. In subsequent editions, and there are many, the physical basis disappeared more and more; and the book took more of the appearance of a philosophical and theological essay.
In my lecture on Clifford[2] I explained how an anagram had appeared in Nature in 1874 and how that later the anagram was explained in The Unseen Universe as follows: "Thought conceived to affect the matter of another universe simultaneously with this may explain a future state." The kernel of the book is this so-called discovery. Preliminary chapters are devoted to a survey of the beliefs of ancient peoples about the immortality of the soul; to physical axioms, to an exposition of the doctrines and hypotheses concerning energy, matter and ether; and to the biological doctrine of development; it is only in the last chapter that we come to the "unseen universe." What is meant by the "unseen universe?" Matter, according to the authors is made up of molecules, which are supposed to be vortex-rings made of the luminiferous ether; the luminiferous ether is in turn supposed to be made of much smaller molecules which are vortex-rings of a second ether. These smaller molecules with the ether in which they float constitute the unseen universe. The authors see reason to believe that the unseen universe absorbs energy from the visible universe and vice versa; in this way a communication is established between them. The human soul is a frame made of the refined molecules and exists in the unseen universe, although in life it is attached to the body. Every thought we think is accompanied by certain motions of the coarse molecules of the brain; these motions are propagated through the visible universe, but a part of each motion is absorbed by the fine molecules of the soul. Consequently the soul as well as the body has an organ of memory; at death the soul with its organ of memory is simply set free from association with the coarse molecules of the body. In this way, the authors considered that they had shown the physical possibility of the immortality of the soul. So far the book may be considered to be a legitimate and interesting metaphysical speculation. But the authors proceeded further to apply their speculation, to explain the main doctrines of Christianity. Hypotheses about the nature of matter may change, and have changed wonderfully since 1875, and no one cares to see sacred truths placed on so precarious a foundation as the vortex theory of matter.
Such was the immediate success of the book, from the point of view of sales, that the authors were induced to venture on a novel Paradoxical Philosophy: a Sequel to the Unseen Universe. The hero is a Dr. Stoffkraft, who goes to Strathkelpie Castle to take part in an investigation of spiritualistic phenomena. He begins by detecting the mode in which one young lady performs her spirit-rapping, but forthwith falls into an "electrobiological" courtship of another, and, this proving successful, he is persuaded by his wife and her priest to renounce the black arts in the lump as works of the devil; and then settles down to compose an "Exposition of the Relations between Religion and Science," which he intends to be a thoroughly matured production. He advocates various materialistic views, but the other guests at the castle, who compose the Paradoxical Club, have read The Unseen Universe, and work discomfiture on Dr. Stoffkraft by arguments drawn from it.
About this time, 1876, Tait published a volume entitled Lectures on Recent Advances in Physical Science. These lectures, prepared at the request of a number of professional men, chiefly engineers, were delivered in the physics theater of the University. They were edited from the report of a stenographer, and they give a very good idea of Tait's style as a lecturer. He was in his time considered the finest lecturer of the Edinburgh University. On reading these lectures, published only twenty-five years ago, one is struck by the greatness of the advances made since, especially in the domain of electricity. In them there is no mention of the telephone or microphone, of the dynamo or incandescent lamp; electric waves and X-rays are yet undemonstrated. The advances treated of are the doctrine of energy, spectrum analysis, the conduction of heat, and the structure of matter. Prof. Tait was accustomed to spend his vacation at the ancient city of St. Andrews, on the sea coast where there is a magnificent course for golf. On one occasion soon after these lectures were published both he and a Glasgow professor of theology, a metaphysician of the Hegelian school, were invited to a dinner in that city. Tait was very naturally drawn out to talk about the subjects on which he had been lecturing, and he did so largely and to the delight and edification of everyone except the Hegelian, who when he could stand it no longer, gravely put the question: "But, Mr. Tait, do you really mean to say that there is much value in such inquiries as you have been speaking about?" After that the subject was changed, and during the rest of the evening the mathematician and the metaphysician did little else than, as one of the company expressed it, "glour at each other."
We have seen that Tait attended the meeting of the British Association at Aberdeen in 1859; but he was not a frequent attendant, for he said that there was too much jabber and talk, and that he did not care for great "spreads." At one of the Edinburgh meetings (1871) he was president of the section of mathematics and physics, on which occasion he delivered an address on Hamilton's Calculus of Quaternions and Thomson's Principle of the Dissipation of Energy. When the Association met in Glasgow in 1876, he was requested on short notice to deliver one of the popular lectures. He took for his subject Force, he made a plea for the accurate use of terms in mechanical science, a reform which has progressed much since that time. He says that force, defined as the rate of change of momentum in a body is also the space-variation of potential energy. Another point he insisted on is that matter and energy are things—have objective existence, because their quantity in the universe is constant; force on the other hand cannot be a thing, or have objective existence, because its quantity is indeterminate. "It is only things," he said, "which can be sold." In view of this dictum it is interesting to observe that some courts have held that an electric current cannot be stolen, as it was not a thing. But what is stolen is the energy of the current, and according to Tait's ideas energy is a thing.
In the same lecture Tait gave a succinct statement of his philosophy of knowledge. "In dealing with physical science" he said, "it is absolutely necessary to keep well in view the allimportant principle that Nothing can be learned as to the physical world save by observation and experiment, or by mathematical deductions from data so obtained. On such a text volumes might be written, but they are unnecessary, for the student of physical science feels at each successive stage of his progress more and more profound conviction of its truth. He must receive it, at starting, as the unanimous conclusion of all who have in a legitimate manner made true physical science the subject of their study, and, as he gradually gains knowledge by this—the only—method, he will see more and more clearly the absolute impotence of all so-called metaphysics or a priori reasoning, to help him to a single step in advance. Man has been left entirely to himself as regards the acquirement of physical knowledge. But he has been gifted with various senses (without which he could not even know that the physical world exists) and with reason to enable him to control and understand their indications. Reason, unaided by the senses, is totally helpless in such matters. The indications given by the senses, unless interpreted by reason, are utterly unmeaning. But when reason and the senses work harmoniously together, they open to us an absolutely illimitable prospect of mysteries to be explored."
What, it may be asked, is this reason which interprets the indications of the senses? Is it not the very a priori knowledge which the rational philosophers have ascribed to the mind? If so, why all this tirade against so-called metaphysics and a priori reasoning? To one who held that all knowledge came through the senses, such procedure would be logical, but not to the savant who uttered the above theory of knowledge. The speculations in the Unseen Universe assume the truth of the vortex theory of atoms. According to the ancient idea of the atom, it is a hard incompressible sphere. Boscovich removed the idea of hardness, and reduced the atom to a mere centre of force. Rankine, we have seen, supposed the point surrounded by a vortex, whirling round an axis passing through the point. Helmholtz investigated the properties of a vortex-ring such as skillful smokers emit. The whirling is round the core of the ring, and is associated with a progressive motion. Thomson replaced Rankine's vortex-atmosphere with Helmholtz's vortex-ring; and showed that the properties of the vortex-ring in a perfect fluid would account for the indestructibility, elasticity and difference in kind of the atoms. The simplest kind oi vortex is the unknotted ring. Suppose that one knot is put on the ring before the ends are tied; this will give the trefoil knot. It has three crossings, and was supposed to figure an essentially different kind of atom.
Professor Tait investigated all the essentially different forms up to nine crossings, and contributed his results to the Edinburgh Royal Society. "Clever," some said, "but what is the use of it." The application was obvious; to elaborate the vortex-ring theory of atoms. Since then, however, electrical investigations have thrown more light on the subject of the atoms, so that Lord Kelvin is for going back to Lucretius.
In the discharge of his duties as a teacher, Tait was a model to his colleagues. The lecture always began punctually at seven minutes past the hour, and did not end till the clock struck the next hour. Lecturing to undergraduate students he never obtruded his own researches, still less made them the subject of lectures; he had a conscientious desire to teach them thoroughly the appointed subjects. He was also punctual in his attendance at the laboratory. In the summer term he came about 11 o'clock, would discuss results and plans with the researchers, take up his own investigation, and generally leave about 2 o'clock. In those days the physical laboratory did not remain open for long hours—from 10 to 3. He had little liking for the general business of the University, and in later years he was to be found only in his lecture room, or laboratory at the University, in his library at home, or in the hall of the Edinburgh Royal Society. For many years he was general secretary, and did Herculean work for the Society. He never sought fellowship in other scientific societies, and the scientific honors he received were not in proportion to the greatness of his scientific achievements.
In the summer time, after the close of the University session, it was Tait's invariable custom to spend the vacation on the links at St. Andrews. He was an enthusiastic golfer, and exemplified the harmony of theory and practice. He investigated by observation and experiment the various physical phenomena, the chief of which is the long time during which the golf ball remains in the air notwithstanding the slight elevation of its path above the ground. To investigate the path and velocity of the ball he made a drive and bunker in the basement of the University building. He communicated his results to the Royal Society of Edinburgh and there stated definitely the longest distance to which a golf ball could possibly be driven. One of his sons, Frederick Guthrie Tait, acquired great skill as a golfer. He was a lieutenant in the famous regiment called Gordon Highlanders, and also the champion amateur golfer of the British Islands. Such was his fame and prowess that to the general public Tait, the eminent mathematician, became known to them from being the father of the champion golfer. Prof. Tait enjoyed his son's success immensely for the buoyant and sanguine temperament of youth remained his throughout life. But the champion golfer upset his father's calculations of the greatest possible distance by driving a ball five yards further!
In the course of his long career Tait was engaged in many polemical discussions. Look over the columns of Nature, and you will find controversies with Tyndall, Proctor, Zöllner, Poincaré, Gibbs, Heaviside and many others. He was apt to take an exaggerated view of men—Newton was nothing short of a god, Leibnitz nothing better than a devil; whereas the truth is that Newton and Leibnitz were both men of many virtues but also of some failings. Tait himself was a man of many heroic virtues, mixed with a few inconsistencies. In these polemical discussions he used exaggerated language, which was probably taken more seriously than he intended. Anyhow a stranger introduced to him in his retiring room at the University, found a very genial and buoyant gentleman, very different from any idea imagined from reading his controversial letters. As regards those who attended his lectures, he commanded their respect and admiration, while the attitude of his research students can be expressed only by veneration and love.
In 1897 his health began to break down before the end of the arduous winter session; but it was recuperated by a vacation on the links at St. Andrews. He had a splendid physique; but it had long been his custom to remain in his library to very late hours, reading, or writing at a plain wooden desk (which he did standing); these long hours of study and mental work eventually told upon his health.
Lieutenant Tait, the champion golfer, was ordered with his regiment to the field of action in South Africa. His regiment (the Black Watch) suffered heavily in the engagements at the Modder River, directed by the unfortunate Lord Methuen. It was reported that Lieutenant Tait had been killed, but his fate remained uncertain for six weeks. He was killed at Koodoosberg, where a white cross now marks his grave. The story of his life has appeared in a book F. G. Tait: a record. The loss was a serious blow to Prof. Tait, already in failing health. Early last year he was unable to attend to any of the duties of his chair, and he sent in his resignation. It was hoped that, freed from teaching duties, his health might recover. At the beginning of July, 1901, he went to the seashore near Edinburgh to spend some days at the house of his friend Sir John Murray, editor of the "Challenger" reports. On July 4, he spent the afternoon in the garden and filled a sheet of foolscap with a quaternion investigation; in the evening he suddenly became ill and died in the course of a few hours, aged 70 years and one month.
Before his death two volumes of his Collected Works had been published and a third will follow. At the time of his retirement those who had been trained by him in research took steps to prepare an illuminated address, but as they were scattered over all the world this was not fully finished at the time of his death, and it was presented to his widow. The address is surrounded by designs emblematic of his principal labors; there is a scroll on which are inscribed certain quaternion equations, a portrait of Newton, a thermo-electric diagram, a deep-sea thermometer, a Crookes' radiometer, and a profusion of knots. There are 63 signatures to the address which reads as follows:
"Dear Professor Tait: We need hardly tell you how deeply we share the universal feeling of regret with which the announcement of your resignation of the chair of Natural Philosophy in the University of Edinburgh has been received. Your tenure of the chair has extended over a most momentous period in the advance of knowledge; and no small part of the progress of physical science, which has been so characteristic of that period, has been the result of your own work. By your investigations and writings you have placed the whole scientific world in your debt, and have added prestige to a chair already rendered illustrious by your distinguished predecessors. The many thousands who have gained from your direct personal teaching a real insight with the processes of nature, and a training in accuracy of thought and of language, will always recall with pleasure and pride that you were their teacher. We whose privilege it was to come into closer touch with you in classroom or in laboratory, have had our life-work in many cases determined and in all cases influenced by the inspiration and guidance received there; and no words can fully express the feelings of reverence and affection which we entertain towards you. Yet, however feeble the expression, we ask you to accept it as our tribute of appreciation and of gratitude for all you have been to us as an intellectual stimulus and as a moral force. Your retirement is an irreparable loss to the University; but if, by relieving you from the arduous duties of the chair, it enables you to devote yourself more entirely to investigation and research, the world will without doubt have the greater gain. We wish you many years of health and strength both for the enjoyment of a well-earned leisure and for the further exercise of an unusually fruitful scientific activity."
But it was not to be.