By this time Larmor was a famous man. After writing many important papers he expanded some of these (from the Phil. Trans., 1894-97) into his book on Aether and Matter (1900), which he described as "a development of the dynamical relation of the aether to material systems, on the basis of the atomic constitution of matter, including a discussion of the influence of the earth's motion on optical phenomena." In the beginning of the book Larmor harks back to Arago and Fresnel, as Hamilton and MacCullagh, and Green also, had done; and in particular to the fundamental question why the motion of the earth does not affect the laws of reflection and refraction. In the latter part, his favourite Principle of Least Action is made to constitute the "single foundation" for the mathematical treatment of the whole case. And the main ultimate conclusion is that all theories are inadequate, and must be set aside, which treat the aether as a sort of highly rarefied matter, of extremely minute density as compared with matter, and subject to dynamic laws or properties which only slightly interfere with those of matter; for the aether is, on the contrary, something fundamental, sui generis, "whose properties must be adapted so as to be consistent, by themselves alone, with the whole range of physics." Men read the book, in Cambridge and elsewhere, as eagerly as they had read Matter and Motion twenty years before. It was the deeper book of the two; for the other was but a crumb (though of the finest wheat) from Maxwell's table. Larmor had a peculiar affection for Matter and Motion; he framed his own title upon it, as Maxwell had done upon a phrase of Dr Johnson's; and he re-edited the little book in after years with additions of his own.
In Aether and Matter Larmor opened many a new door, especially to the younger physicists. He went straight back to MacCullagh, who (in 1839) had devised an "aether" to fit certain optical phenomena, and inquired how far an identical aether would serve for electricity. The "atomic" character of electricity (foreshadowed by Faraday, and embodied in Maxwell's phrase, a "molecule of electricity") became part of the story; and furthermore, "it was natural to infer that the ultimate atom of electricity is one aspect of the entity which constitutes the ultimate atom of matter." He supposed an electric charge to consist of discrete electrons, in which nuclei are surrounded by intrinsic rotational strain. He suggested that the inertia of ordinary matter might be due to such a charge, and that the material atoms themselves consisted of systems of electrons. He discussed the Kerr effect, and FitzGerald's analysis of it; and he developed in a remarkable manner (simultaneously with Lorentz) FitzGerald's fertile hypothesis of the contraction of a moving body. By this time J J Thomson was in the full flood-tide of experimental research, turning the "electron" from a bold hypothesis into objective reality; and the two rivals of the 1880 Tripos, the great experimenter and the mathematical physicist, were now the acknowledged leaders of the Cambridge School.
But times were changing very rapidly - much as they had done fifty or sixty years before, when Green and MacCullagh and Stokes made their entrance on the stage: when Green had just devised the concept of potential, when MacCullagh and Hamilton, and later Stokes, were developing the optics of Fresnel, and Kelvin and Joule, were soon to establish the theory of heat and the conservation of energy. So it happened again. While Larmor was writing his book the Zeemann effect was discovered, and he discussed it in his last pages; the Röntgen rays followed quickly, and immediately after came Henri Becquerel and Mme Curie; radium came out a few months before the book; J J Thomson discovered the electron, and Crookes showed the atom in the spinthariscope; the Quantum Theory was suggested by Planck in the year the book was published, and soon after Einstein's Relativity caught the ear and captured the imagination of the world. Larmor was open to all the new knowledge, but he had little relish for the new ideas; it was much the same with Kelvin, but Kelvin was a much older man. Larmor neither questioned nor disparaged the experimental work, but he was less sure of the mathematical. It is certain that, for one reason and another, he distrusted Einstein, and nursed a suspicion, even a hope, that some day a flaw might be discovered in his work, or its interpretation. He was laudator temporis acti, in physics as afterwards in Irish politics. The three Dublin giants, Kelvin from Belfast and his brother James ("the philosopher who plagued his pragmatical brother"), Maxwell of course, and a few bright but lesser lights like George Johnstone Stoney, another Irishman (who had helped to revive the atomic hypothesis and gave its name to the electron), and J J Waterston of Edinburgh (who "anticipated Clausius and Kelvin both,"and "ranks alongside Sadi Carnot") - these were Larmor's heroes and demigods to the end; and he could not forgive the new generation for forgetting, as he believed they did, "that Scoto-Irish school of physics which dominated the world in the middle of last century, but has now vanished from the face of the earth." His obituary of Kelvin (Proc. R. S., 1908) was a labour of love, and he remained proud of it as one of the best things he had ever done. He was proud also of the historical note he wrote (in 1929) on Sir William Rowan Hamilton as an appendix to his works, and spoke of it as "the only adequate one ever written." But he grieved especially over the general neglect of Hamilton. He looked in vain (he said) for his works in the Cambridge bookshops; a review in a French scientific journal was "pathetic in its incompetence"; and a large part of the "vast treasury" of manuscript which Hamilton left behind was not deemed worth the cost of printing.
Larmor was a man of varied learning and tireless industry. About the year 1933 the grievous malady of pernicious anaemia began to rob him of his strength, but modem treatment held it at bay and Larmor kept on reading and meditating to the end. He enjoyed writing short articles, mostly to Nature, on all sorts of subjects. "I find," he wrote me once, "that letters to Nature attract attention in America and elsewhere, whereas my experience of papers to societies is that they are just ignored, unless they happen to be in the vein of the moment." In another letter (in 1941) he said: " Years ago I discovered that it was not possible nowadays for me to obtain a hearing in scientific journals, being drowned in the avalanche of voluminous research." With certain modern forms of "research" and "team-work" he had little patience and less sympathy. "We are both alike convinced," he wrote to me, "that if civilisation is to survive, education must be rescued from the clutches of research." He found some solace in metaphysics, as old men are apt to do. "I have been wallowing," he wrote in 1939, "in metaphysics, thus wasting my leisure, which will not last long. But I think I touch bottom in places, as all metaphysicians do!" He is unusually outspoken in the same letter about relativity: "It becomes more and more strange that the Einstein scheme has survived so long - largely by ignoration of values."
He did not lack interest in biology, and he discussed innumerable points with me when I was writing Growth and Form, a quarter of a century ago. He had discussed mitosis with Loeb and E B Wilson, "not to say Arrhenius." It remained a mystery, which he never hoped to understand; but he thought we should go on detecting superficial phenomena in connection with it, and "should certainly be able to classify these under the laws of dead matter." "I am a vitalist," he wrote, "with the intensification that vital agency acts so as to enlist all the physical forces to its aid. I once thought that Hans Driesch approached my ideas; but a long lecture from him some years ago nearly buried me under long words which I did not understand!"
Among the many miscellaneous articles which he wrote in his retirement at Holywood is one on the origin of the zodiacal light - a curious article, suggesting a sort of tenuous Saturn's Ring around the sun; another on the physiological potency of dilute drugs, drawn from his own sad experience; others on viscid threads; on the radioactivity of the ocean floor; on the equilibrium, or "isostasy," of mountain-ranges, and how the question bears on glacial climates, on the distortion of strata, and many other geophysical phenomena. He talked of many other subjects besides these in his frequent letters: for instance, why the herring left the Baltic Sea - he had been reading H A L Fisher on the Hanseatic League! Again he was interested in the aesthetic senses of bees and moths, and wondered why they were attracted by the same flowers as seem beautiful to mankind. But always of recent years two great subjects seemed uppermost in his mind (as they had been in Hamilton's): the mystery of Time was one of these, and that of Mind the other. He thought much but wrote little on these twos cognate mysteries; but one of his few utterances was in the shape of a review, in the Journal of Theological Studies (1937), of A A Robb's Geometry of Time and Space - Robb being one of the few critics of Einstein. Larmor spoke here of Universal Mental Time, such as might be supposed to conform to a "universal and unique Mental Cosmos." He was drawn in his old age, if not all his life long, to the contemplation of supra-mundane things; theology, rather than religion, was never far away; he studied Time and meditated on Eternity. He looked beyond Aether and Matter to the Beginnings of things, and to the ultimate and basic Fact of all. "The intellect," he said in the same article, "is fully engaged in profitably adjusting and organising the more regular features of the wrack cast up on the shore of human experience, from the unfathomable ocean of existence beyond." In one of his letters he said: "I am occupying my reflections by constructing a sort of commonplace book on the relation of Time, as closely scrutinized, to Natural Theology, and how it leaves Hume and Kant somewhat bogged in imperfect ideas, while your Aberdonian Thomas Reid has earned congratulation which is never far absent from commonsense principles." And in another letter he hoped that his reflections on this theme might bear fruit "when the present phase has worn off, and people are willing to consider ideas not based on the negation of the great age of mathematical physics."
Many honours and distinctions, including the Copley Medal, came Larmor's way. One of the highest of these was his Corresponding Membership of the French Institute. He prized it greatly; but with characteristic modesty he ascribed it, not to his world-wide reputation, but "to a recent laudation of Sadi Carnot." His knighthood came in 1909. He was elected an Honorary Fellow of our Society in 1910. It is an open secret, which he never told, that with all his honours he was a disappointed man - all for the want of the one honour which he would have prized above all the rest, the Mastership of his College.
Neat and dapper in his person, he became careless of his appearance, even of his personal comfort, under stress of sickness and old age. His brother's death left him alone in the world. He grew "more and more solitary-minded," as he called it; and towards the end perhaps his only pleasure was to write long letters to a few old friends. These letters were almost illegible, but his handwriting had been clear and even beautiful when he was young. When he died, in 1942, he was eighty-five years old; Kelvin had died thirty-five years before, at eighty-three; and Clerk Maxwell at forty-eight, sixty-three years before.
Larmor made few friends, perhaps; but while he lived, and they lived, he lost none.