Tyndall, John (DNB00)

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TYNDALL, JOHN (1820–1893), natural philosopher, son of John Tyndall and his wife Sarah (Macassey), was born at Leighlin Bridge, co. Carlow, on 2 Aug. 1820. The Tyndalls, who claimed relationship with the family of William Tyndale [q. v.] the martyr, had crossed from Gloucestershire to Ireland in the seventeenth century. The elder John Tyndall, son of a small landowner, although poor, was a man of superior intellect, and he gave his son the best education which his circumstances could afford. At the local national school young Tyndall acquired a thorough knowledge of elementary mathematics, which qualified him to enter as civil assistant (in 1839) the ordnance survey of Ireland. In 1842 he was selected, as one of the best draughtsmen in his department, for employment on the English survey. While quartered at Preston in Lancashire he joined the mechanics' institute and attended its lectures. He was at this time much impressed by Carlyle's ‘Past and Present,’ and to the stimulating influence of Carlyle's works was in part due his later resolve to follow a scientific career. On quitting the survey Tyndall was employed for three years as a railway engineer.

In 1847 he accepted an offer from George Edmondson [q. v.], principal of Queenwood College, Hampshire, to join the college staff as teacher of mathematics and surveying. Mr. (now Sir Edward) Frankland was lecturer on chemistry, and the two young men agreed respectively to instruct each other in chemistry and mathematics. But Queenwood did not yield all the opportunities they wished for, and they presently resolved to take advantage of the excellent instruction to be enjoyed at the university of Marburg in Hesse-Cassel. The decision was for Tyndall a momentous one. He had nothing but his own work and slender savings to depend on, and his friends thought him mad for abandoning the brilliant possibilities then open to a railway engineer.

In October 1848 Tyndall and Frankland settled at Marburg. Tyndall attended Bunsen's lectures on experimental and practical chemistry, and studied mathematics and physics in the classes and laboratories of Stegmann, Gerling, and Knoblauch. By intense application he accomplished in less than two years the work usually extended over three, and thus became doctor of philosophy early in 1850. Thenceforward he was free to devote himself entirely to original research.

His first scientific paper was a mathematical essay on screw surfaces—‘Die Schraubenfläche mit geneigter Erzeugungslinie und die Bedingungen des Gleichgewichts für solche Schrauben’—which formed his inaugural dissertation when he took his degree. His first physical paper, published in the ‘Philosophical Magazine’ for February 1851, was on the ‘Phenomena of a Water Jet’—a subject comparatively simple but not without scientific interest.

In conjunction with Knoblauch, Tyndall executed and published an important investigation ‘On the Magneto-optic Properties of Crystals and the relation of Magnetism and Diamagnetism to Molecular Arrangement’ (Phil. Mag. July 1850). They claimed to have discovered the existence of a relation between the density of matter and the manifestation of the magnetic force. Their fundamental idea was that the component molecules of crystals, and other substances, are not in every direction at the same distance from each other. The superior magnetic energy of a crystal in a given direction, when suspended between the poles, they attributed to the greater closeness of its molecules in that direction. In support of their assumption they showed that, by pressure, the magnetic axis of a bismuth crystal could be shifted 90° in azimuth, the line of pressure always setting itself parallel with, or at right angles to, the line joining the two magnetic poles, according as the crystal was magnetic or diamagnetic. This explanation differed essentially from that of Faraday and Plücker. In June 1850 Tyndall went to England, and at the meeting of the British Association of that year in Edinburgh he read an account of his investigation which excited considerable interest. He afterwards returned to Marburg for six months, and carried out a lengthy inquiry into electro-magnetic attractions at short distances (Phil. Mag. April 1851).

At Easter 1851 Tyndall finally left Marburg and went to Berlin, where he became acquainted with many eminent men of science. In the laboratory of Professor Magnus he conducted a second investigation on ‘Diamagnetism and Magne-crystallic Action’ (ib. September 1851), which formed a sequel to that previously undertaken with Knoblauch. A paper describing his results was read at the Ipswich meeting of the British Association. He showed that the antithesis of the two forces was absolute: diamagnetism resembling magnetism as to polarity and all other characteristics, differing from it only by the substitution of repulsion for attraction and vice versa.

The question of diamagnetic polarity was much discussed. Its existence, originally asserted by Faraday and reaffirmed by Weber in 1848, had been subsequently denied by Faraday, who still continued doubtful. To meet all objections, Tyndall, at a later date, again took up the subject, and in three conclusive investigations, the second of which formed the subject of the Bakerian lecture delivered before the Royal Society in 1855, he put the polarity of bismuth and other diamagnetic bodies beyond question (ib. November 1851; Phil. Trans. 1855; ib. 1856, pt. i.) Five years were devoted by him to the investigation of diamagnetism and the influence of crystalline structure and mechanical pressure upon the manifestations of magnetic force. The original papers (with a few omissions in the last edition) are collected in his book on ‘Diamagnetism’ (see below).

Before leaving Marburg in 1851, Tyndall had agreed to return to Queenwood; this time as lecturer on mathematics and natural philosophy. Here he remained two years. The first of the three investigations just alluded to was carried out at Queenwood, as was also a series of experiments on the ‘Conduction of Heat through Wood’ (see ‘Molecular Influences,’ Phil. Trans. January 1853). On 3 June 1852 Tyndall was elected fellow of the Royal Society.

While at Queenwood he applied for several positions which offered a wider scope for his abilities. On his way to Ipswich in 1851 he had made the acquaintance of T. H. Huxley, and a warm and enduring friendship resulted. They made joint applications for the chairs respectively of natural history and physics then vacant at Toronto, but, in spite of high testimonials, they were unsuccessful. They also failed in candidatures for chairs in the newly founded university of Sydney, New South Wales. Meanwhile, soon after Tyndall's departure from Berlin, Dr. Henry Bence Jones [q. v.] visited that city, and, hearing much of Tyndall's labours and personality, caused him to be invited to give a Friday evening lecture at the Royal Institution. The lecture, ‘On the Influence of Material Aggregation upon the Manifestations of Force’ (Roy. Inst. Proc. i. 185), was delivered on 11 Feb. 1853. It produced an extraordinary impression, and Tyndall, hitherto known only among physicists, became famous beyond the limits of scientific society. In May 1853 he was unanimously chosen as professor of natural philosophy in the Royal Institution. The appointment had the special charm of making him the colleague of Faraday. Seldom have two men worked together so harmoniously as did Faraday and Tyndall during the years that followed. Their relationship from first to last resembled that of father and son. Tyndall's ‘Faraday as a Discoverer’ bears striking testimony to their attachment. Other sketches of Faraday by Tyndall are in his ‘Fragments of Science,’ and in the life of Faraday in this dictionary.

Tyndall's career was now definitely marked out. To the end of his active life his best energies were devoted to the service of the Royal Institution. In 1867, when Faraday died, Tyndall succeeded him in his position as superintendent of the Institution. On his own retirement in the autumn of 1887 he was elected honorary professor.

In 1854, after attending the British Association meeting at Liverpool, Tyndall visited the slate quarries of Penrhyn. His familiarity with the effects of pressure upon the structure of crystals led him to give special attention to the problem of slaty cleavage. By careful observation and experiments with white wax and many other substances which develop cleavage in planes perpendicular to pressure, he satisfied himself that pressure alone was sufficient to produce the cleavage of slate rocks. On 6 June 1856 he lectured on the subject at the Royal Institution (see appendix to Glaciers of the Alps). Huxley, who was present, suggested afterwards that the same cause might possibly explain the laminated structure of glacier ice recently described in Forbes's ‘Travels in the Alps.’ The friends agreed to take a holiday and inspect the glaciers together. The results of the observations made during this and two subsequent visits to Switzerland are given in Tyndall's classical work ‘The Glaciers of the Alps’ (see below). The original memoirs are in the ‘Philosophical Transactions’ for 1857 and 1859. Tyndall, assisted by his friend Thomas Archer Hirst, made many measurements upon the glaciers in continuation of the work of Agassiz and Forbes. He discussed, in particular, the question as to the conditions which enable a rigid body like ice to move like a river. He showed very clearly the defects of former theories, proving by repeated observations on the structure and properties of ice the inefficacy of the generally admitted plastic theory to account for the phenomena. Through the direct application of the doctrine of regelation he arrived at a satisfactory explanation of the nature of glacier motion. The veined structure he ascribed to mechanical pressure, and the formation of crevasses to strains and pressures occurring in the body of the glacier. In assigning to Rendu his position in the history of glacier theories, Tyndall gave offence to James David Forbes [q. v.] A controversy followed, in which the fairness of Tyndall's attitude was fully vindicated.

The expedition to Switzerland, undertaken for a scientific purpose, had a secondary outcome. Tyndall was fascinated by the mountains, and from that time forward yearly sought refreshment in the Alps when his labours in London were over. He became an accomplished mountaineer. In company with Mr. Vaughan Hawkins he made one of the earliest assaults upon the Matterhorn in 1860. He crossed over its summit from Breuil to Zermatt in 1868. The first ascent of the Weisshorn was made by him, in 1861. Tyndall's descriptions of his alpine adventures are not only graphic and characterised by his keen interest in scientific problems, but show a poetical appreciation of mountain beauties in which he is approached by few alpine travellers.

The very important series of researches on ‘Radiant Heat in its relation to gases and vapours,’ which occupied him on and off for twelve years, and with which his name will be always especially associated, were begun in 1859. He was led from the consideration of glacier problems to study the part played by aqueous vapour and other constituents of the atmosphere in producing the remarkable conditions of temperature which prevail in mountainous regions. The inquiry was one of exceptional difficulty. Prior to 1859 no means had been found of determining by experiment, as Melloni had done for solids and liquids, the absorption, radiation, and transmission of heat by gases and vapours. By the invention of new and more delicate methods Tyndall succeeded in controlling the refractory gases. He found unsuspected differences to exist in their respective powers of absorption. While elementary gases offered practically no obstacle to the passage of heat rays, some of the compound gases absorbed more than eighty per cent. of the incident radiation. Allotropic forms came under the same rule; ozone, for example, being a much better absorbent than oxygen. The temperature of the source of heat was found to be of importance: heat of a higher temperature was much more penetrative than heat of a lower temperature.

The power to absorb and the power to radiate Tyndall showed to be perfectly reciprocal. He also established that, as regards their powers of absorption and radiation, liquids and their vapours respectively follow the same order. Thus he was able to determine the position of aqueous vapour, which, on account of condensation, could not be experimented upon directly. Experiments made with dry and humid air corroborated the inference that as water transcends all other liquids, so aqueous vapour is powerful above all other vapours, as a radiator and absorber. These results, questioned by Magnus and by a few later experimenters, but fully established by Tyndall, explained a number of phenomena previously unaccounted for. Since Wells's researches on dew, no fact has been established of greater importance to the science of meteorology than the high absorptive and radiative power of aqueous vapour. Many years later an experiment made in his presence by Mr. Graham Bell suggested to Tyndall a novel and interesting method of indirectly confirming his former results. (See ‘Action of Free Molecules on Radiant Heat, and its Conversion thereby into Sound,’ Phil. Trans. 1882, pt. i.).

Using a dark solution of iodine in bisulphide of carbon as a ray-filter, Tyndall was able approximately to determine the proportion of luminous to non-luminous rays in the electric and other lights. He also found that the obscure rays collected by means of a rock-salt lens would ignite combustible materials at the invisible focus; while some non-combustible bodies, exposed at the same dark focus, became luminous or calorescent. The astounding change in the deportment of matter towards heat radiated from an obscure source which accompanies the act of chemical combination, and many other points of equal importance, were first established by these researches, for which Tyndall received the Rumford medal in 1869. Nine memoirs on these subjects were published in the ‘Philosophical Transactions,’ and many additional papers in other journals. They have been gathered together in ‘Contributions to Molecular Physics in the Domain of Radiant Heat’ (see below). This volume also includes a series of striking experiments on the decomposition of vapours by light, in the course of which the blue of the firmament and the polarisation of sky-light—illustrated on skies artificially produced—were shown to be due to excessively fine particles floating in our atmosphere.

While engaged upon the last-mentioned inquiry, Tyndall observed that a luminous beam, passing through the moteless air of his experimental tube, was invisible. It occurred to him that such a beam might be utilised to detect the presence of germs in the atmosphere: air incompetent to scatter light, through the absence of all floating particles, must be free from bacteria and their germs. Numerous experiments showed ‘optically pure’ air to be incapable of developing bacterial life. In properly protected vessels infusions of fish, flesh, and vegetable, freely exposed after boiling to air rendered moteless by subsidence, and declared to be so by the invisible passage of a powerful electric beam, remained permanently pure and unaltered; whereas the identical liquids, exposed afterwards to ordinary dust-laden air, soon swarmed with bacteria. Three extensive investigations into the behaviour of putrefactive organisms were made by Tyndall, mainly with the view of removing such vagueness as still lingered in the public mind in 1875–6, regarding the once widely received doctrine of spontaneous generation. Among the new results arrived at, the following are noteworthy: bacteria are killed below 100° C., but their desiccated germs—those of the hay bacillus in particular—may retain their vitality after several hours' boiling. By a process which he called ‘discontinuous heating,’ whereby the germs, in the order of their development, were successively destroyed before starting into active life, he succeeded in sterilising nutritive liquids containing the most resistant germs. This method, since universally adopted by bacteriologists, has proved of great practical value. The medical faculty of Tübingen gave Tyndall the degree of M.D. in recognition of these researches. The original essays, written for the ‘Philosophical Transactions,’ are collected in ‘Floating Matter of the Air’ (see below).

In 1866 Tyndall had succeeded Faraday as scientific adviser to the Trinity House and board of trade. He held the post for seventeen years, and it was in connection with the elder brethren that his chief investigations on sound were undertaken, with a view to the establishment of fog signals upon our coasts. Many conflicting opinions were held as to the respective values of the various sound signals in use when Tyndall began his experiments at the South Foreland (19 May 1873). Very discordant results appeared at first, but all were eventually traced to variations of density in the atmosphere. Tyndall discovered that non-homogeneity of the atmosphere affects sound as cloudiness affects light. By streams of air differently heated, or saturated in different degrees with aqueous vapour, ‘acoustic flocculence’ is produced. Acoustic clouds, opaque enough to intercept sound altogether and to produce echoes of great intensity, may exist in air of perfect visual transparency. Rain, hail, snow, and fog were found not sensibly to obstruct sound. The atmosphere was also shown to exercise a selective and continually varying influence upon sounds, being favourable to the transmission sometimes of the longer, sometimes of the shorter, sonorous waves. Tyndall recommended the steam siren used in the South Foreland experiments as, upon the whole, the most powerful fog signal yet tried in England. His memoir on the subject, presented to the Royal Society on 5 Feb. 1874, is summarised in the book on ‘Sound’ (see below). Passing mention should be made of the beautiful experiments on sensitive flames described in the same volume.

It was likewise in his capacity of scientific adviser that Tyndall was called upon, in 1869 and on many subsequent occasions, to report upon the gas system introduced by Mr. John Wigham of Dublin, the originator of several important steps in modern lighthouse illumination. Tyndall's inability, during a long series of years, to secure what he considered justice towards Mr. Wigham led him eventually to sever himself from colleagues to whom he was sincerely attached. He resigned his post on 28 March 1883 (see Nineteenth Century, July 1888; Fortnightly Review, December 1888 and February 1889; New Review, 1892).

As a lecturer Tyndall was famed for the charm and animation of his language, for lucidity of exposition, and singular skill in devising and conducting beautiful experimental illustrations. As a writer he did perhaps more than any other person of his time for the diffusion of scientific knowledge. By the publication of his lectures and essays he aimed especially at rendering intelligible to all, in non-technical language, the dominant scientific ideas of the century. His work has borne abundant fruit in inciting others to take up the great interests which possessed so powerful an attraction for himself. In ‘Heat as a Mode of Motion’ (see below), which has been regarded as the best of Tyndall's books, that difficult subject was for the first time presented in a popular form. The book on ‘Light’ gives the substance of lectures delivered in the United States in the winter of 1872–3. The proceeds of these lectures, which by judicious investment amounted in a few years to between 6,000l. and 7,000l., were devoted to the encouragement of science in the United States.

His views upon the great question as to the relation between science and theological opinions are best given in his presidential address to the British Association at Belfast in 1874, which occasioned much controversy at the time (reprinted, with essays on kindred subjects, in ‘Fragments of Science,’ vol. ii.) The main purpose of that address was to maintain the claims of science to discuss all such questions fully and freely in all their bearings.

On 29 Feb. 1876 Tyndall married Louisa, eldest daughter of Lord Claud Hamilton, who became his companion in all things. In 1877 they built a cottage at Bel Alp, on the northern side of the Valais, above Brieg. There they spent their summers amid his favourite haunts. In 1885 they built what Tyndall called ‘a retreat for his old age’ upon the summit of Hind Head, on the Surrey moors, then a very retired district. Sleeplessness and weakness of digestion—ills from which he had suffered more or less all his life—increased upon him in later years, and caused him to resign his post at the Royal Institution in March 1887. His later years were for the most part spent at Hind Head. Repeated attacks of severe illness, unhappily, prevented the execution of the many plans he had laid out for his years of retirement. In 1893 he returned greatly benefited from a three months' sojourn in the Alps. But a dose of chloral, accidentally administered, brought all to a close on 4 Dec. 1893.

Tyndall's single-hearted devotion to science and indifference to worldly advantages were but one manifestation of a noble and generous nature. A resolute will and lofty principles, always pointing to a high ideal, were in him associated with great tenderness and consideration for others. His chivalrous sense of justice led him not unfrequently—irrespective of nationality or even of personal acquaintance, and often at great cost of time and trouble to himself—to take up the cause of men whom he deemed to have been unfairly treated or overlooked in respect to their scientific merits. He thus vindicated the claim of the unfortunate German physician, Dr. Julius Robert Mayer, to have been the first to lay down clearly the principle of the conservation of energy and to point out its universal application; and succeeded in obtaining his recognition by the scientific world in spite of eminent opposition. The same spirit appeared in his defence of Rendu's title to a share in the explanation of glacier movement, and of Wigham's services in regard to lighthouses.

Tyndall took a warm interest in some great political questions. He sided strongly with the liberal unionists in opposing Mr. Gladstone's home-rule policy.

Tyndall was of middle height, sparely built, but with a strength, toughness, and flexibility of limb which qualified him to endure great fatigue and achieve the most difficult feats as a mountaineer. His face was rather stern and strongly marked, but the sharp features assumed an exceedingly pleasing expression when his sympathy was touched, and the effect was heightened by the quality of his voice. His eyes were grey-blue, and his hair, light-brown in youth, was abundant and of very fine texture. He had generally, like Faraday, to bespeak a hat on account of the unusual length of his head. A medallion of Tyndall, executed by Woolner in 1876, is perhaps the best likeness that exists of him.

Tyndall's works have been translated into most European languages. In Germany (where Helmholtz and Wiedemann undertook the translations and wrote prefaces) they are read almost as much as in England. Some thousands of his books are sold yearly in America, and a few translations have been made into the languages of India, China, and Japan. In the Royal Society's catalogue of scientific papers 145 entries appear under Tyn- Tyndall's name between 1850 and 1883, indicating approximately the number of his contributions to the ‘Philosophical Transactions,’ the ‘Philosophical Magazine,’ the ‘Proceedings’ of the Royal Society and of the Royal Institution, and other scientific journals. A great variety of subjects besides those glanced at above occupied his attention. They are for the most part dealt with in the miscellaneous essays collected in ‘Fragments of Science’ and ‘New Fragments.’ The essence of his teaching is contained in the following publications:

  1. ‘The Glaciers of the Alps, being a Narrative of Excursions and Ascents, an Account of the Origin and Phenomena of Glaciers, and an Exposition of the Physical Principles to which they are related,’ 1860; reprinted in 1896; translated for the first time into German in 1898.
  2. ‘Mountaineering in 1861: a vacation tour,’ 1862 (mostly repeated in ‘Hours of Exercise’).
  3. ‘Heat considered as a Mode of Motion,’ 1863; fresh editions, each altered and enlarged, in 1865, 1868, 1870, 1875; the sixth edition, 1880, was stereotyped.
  4. ‘On Sound,’ a course of eight lectures, 1867; 3rd edit., with additions, 1875; 4th edit., revised and augmented, 1883; 5th edit., revised, 1893.
  5. ‘Faraday as a Discoverer,’ 1868; 5th edit., revised 1894.
  6. ‘Researches on Diamagnetism and Magne-crystallic Action, including the question of Diamagnetic Polarity,’ 1870; third and smaller edition, 1888.
  7. ‘Fragments of Science for Unscientific People: a series of Detached Essays, Lectures, and Reviews,’ 1871; augmented in the first five editions; from 6th edit., 1879, in 2 vols.
  8. ‘Hours of Exercise in the Alps,’ 1871; 2nd edit. 1871; 3rd edit. 1873; a reprint is now in hand (1898).
  9. ‘Contributions to Molecular Physics in the Domain of Radiant Heat’ (memoirs from the ‘Philosophical Transactions’ and ‘Philosophical Magazine,’ with additions), 1872.
  10. ‘The Forms of Water in Clouds and Rivers, Ice, and Glaciers’ (International Scient. Ser.), 1872; 12th edit. 1897.
  11. ‘Six Lectures on Light, delivered in America in 1872–3’ (1873); 5th edit. 1895.
  12. ‘Lessons in Electricity, at the Royal Institution,’ 1876; 5th edit. 1892.
  13. ‘Essays on the Floating Matter of the Air in relation to Putrefaction and Infection,’ 1881; 2nd edit. 1883.
  14. ‘New Fragments,’ 1892; last edit. 1897.
  15. ‘Notes on Light: nine Lectures delivered in 1869,’ 1870.
  16. ‘Notes on Electrical Phenomena and Theories, seven Lectures delivered in 1870,’ 1870.

[A life is being prepared, based upon the materials, in the possession of Mrs. Tyndall, used in the above article. Among many contemporary notices (in some of which are slight inaccuracies) are: Proc. Roy. Soc. vol. lv. p. xviii, and Proc. Inst. Civil Engineers, cxvi. (session 1893–4), ii. 340, both by Sir Edward Frankland; Proc. Roy. Inst. (special meeting, 15 Dec. 1893), xiv. 161–8, by Sir James Crichton Browne; ib. xiv. 216–24, by Lord Rayleigh; Nineteenth Century, Jan. 1894, by Prof. Huxley; Fortnightly Rev. Feb. 1894, by Herbert Spencer; Times, 5 Dec. 1893; Journal Chemical Soc. lxv. 389; Physical Rev., i. 302. See also on Tyndall's retirement, Times, 8 April and 30 June 1887 (appreciation by Sir George Stokes).]

L. C. T.