The Infancy of Atomic Physics: Hercules in His Cradle

INDEX

INTRODUCTION

For more than half a century we have been living on the intellectual muscle built up during the twenty years that ended with the outbreak of the First World War. Our art and music, our politics—our physical science, and above all our scientific technologies are working out ideas born at the turn of the century. In a few short years old assumptions were challenged and overthrown in every field. Physics was an integral part of this revolution, no less than futurism or fauvism, the Rite of Spring or the Demoiselles d’Avignon; in science, at least, it was a time of renaissance, renewal, adventure, which it was hoped would make the twentieth century even more glorious than the nineteenth. The consequences of that scientific thrust forward have not always been as cheerful as the prophets expected. And yet, at this moment we may have to choose between nuclear energy and a simpler way of life: atomic physics underlies our science, and most hopes for a continuation of present affluence.

Why then has there been so little written in any detail about the strange birth and heroic infancy of that Hercules which is modern atomic science? Popular accounts of contemporary science do sometimes include a historical introduction to their subject, but discoveries follow in simple sequence, in regular order, as if they were so revealed to the genius of enquiry. Why trouble the reader with what have since proved to be wrong answers, however exciting they may have looked at the time, or entangle us in the personalities, and the personality conflicts, that beset them? Tell us that in 1898 Bigwig observed Bigwig’s effect, perhaps show us a formal picture of Bigwig taken when he was at last elevated to a professorial chair; tell us how Bigwig’s effect was useful in solving this or that problem, or raised a new one—but do not waste the innocent reader’s time with the man behind the picture. That is a reasonable limit if we wish only to know what science says to us now. Historians usually go too far the other way. Economic and political histories of our busy century there have been in plenty, yet they too neglect the history of its science, and show some interest only when new technologies burst noisily upon their stage. The time has come to write about the origins of that science with the same concern for events as they were lived, as would be allowed for King Edward VII or Kaiser Wilhelm, or the politicians who made headlines in the newspapers. After all, the scientists have had more influence upon our lives. And they are often more attractive people. This book is an attempt at a history of a great upheaval, as it looked at the time to those who were guiding these expeditions into the unknown, and to those who tried hard to keep up with them.

A scientist who had a goodly share in one of the great advances of twentieth-century biology has remarked that ‘science seldom proceeds in the straightforward logical manner imagined by outsiders’, but rather by stages which are often ‘very human events in which personalities and cultural traditions play major roles’.¹ But is it possible to write a Double helix of the nuclear atom? Perhaps not, but those personal and national characteristics must be brought out. The language of science changes from place to place and from generation to generation, less perhaps than the language of the street or of entertainment; but it does change, nevertheless. The science of the 1890s and the Edwardian era is now becoming remote, and some effort must be made to think ourselves back into it.

Fortunately over the past decade much fresh information has been made available to help us in that effort. There are edited collections of several of the classic papers, with commentary to steer the modern reader through them, although these have to be supplemented by other papers against which the classicism of the great ones may be judged. Historians of science have ventured at last into the twentieth century and scrutinized the work of Rutherford, Thomson, Bohr, Einstein, and the rest as carefully as they examine the writings of Darwin or Newton. In their journals, the articles of Heilbron, McCormmach, Trenn, and others give us a sense of the fine detail, the false trails as well as the fruitful, and (particularly in the journal Historical Studies in the Physical Sciences) suggest how contemporary philosophies and social or political attitudes may have modified the path of scientific thought. Many private letters dating from the crucial years of Rutherford, Bohr, and Moseley have now been published, so that we can glimpse how their ideas took shape as they confided in their closest friends and relatives.

Science is not just the knowledge of great men. In the pages of Nature, in the reports of discussions and lectures at meetings of the British Association for the Advancement of Science, say, or the Royal Institution, the contemporary picture of the physical world is articulated. Textbooks and popularizations colour in the background against which the leading actors perform; they provide an audience which may applaud—or may ignore. Nature may speak for the ordinary scientist, for the amateur and enthusiast. What of the general public? Something at least may be gleaned from posters and advertisements, from cartoons and comic rhymes in magazines like Punch; the Forsytian outlook on the world is enshrined in the columns of the Illustrated London News, which during those years published a column of ‘Science jottings’ by a Dr Andrew Wilson. They are indeed mostly on medicine and biology, perhaps suited for his readership, always worried about its health, so his comments on the more dramatic developments in the physical sciences are the more intriguing, although his judgment was shaky at times. In August 1909, after Blériot he could declare that ’it would still be long, very long before man can really fly, if indeed he ever really ‘aviates’ successfully at all . . .’ A more comprehensive view of the science journalism of the day, of the way scientific breakthroughs were reported to the public, may be found in the Annual register of world events. In 1863, the editors decided to complement their purely political record of wars and rumours of war and parliamentary debates, with sections on the major activities of the past year in literature, science, and the arts. The science section was laid out in neat disciplinary sub-sections which therefore give a very compact and well-written survey of each year’s doings on the scientific frontier with the benefit of only a few months’ hindsight at most.

Among the cultural peculiarities revealed by enquiry into the face that science then presented are the curiously national styles in physics at the turn of the century. New paths might be trodden in one country, while the others hung back for a while; or in some controversy the majority in one country were to be found on one side, in a neighbouring land on the other. Why should this be so? Germany and the Germans are no doubt composed of protons, neutrons, and electrons identical to those of Britain or France. Yet if nature is the same, the approach to it was different.

It was a nationalistic epoch in which the language of racial competition and the imagery of war and soldiering came easily to the tongue. Behind the internationalism of science lay a simple array of loyalties which scientists usually shared, or at least very seldom tried to question. Internationalism was certainly regarded as a birthright of science. When nations were at loggerheads, their scientists could still happily coexist. On the only occasion when the British Association for the Advancement of Science rated a full page Punch cartoon, for its joint meeting with the parallel French organization at Dover in 1899, when Britain and France were quarrelling over their claims to various chunks of Africa, the two scientific gatherings are depicted as two girls playing happily together collecting shells on the beach. Scientific collaboration was common and many scientists trained for a period in foreign laboratories to broaden their minds. Yet a young Hungarian colleague of Rutherford’s wrote to him in 1913 on the contrast between the British Association meeting at Birmingham that September, and a similar congress held at Vienna straight after: ‘altogether it was more knowledge in Vienna but far more ingenuity at Birmingham’. A few months later another young colleague, Henry Moseley, described a visit from the eminent French chemist Urbain from whom he learnt that ‘the French point of view is essentially different from the English—where we try to find models or analogies, they are quite content with laws’.

At the 1909 British Association meeting when J.J. Thomson was President of the Association and Rutherford of the Physics Section, it is interesting that both make a point of stressing the value of models. Men of exceptional ability as mathematicians kept insisting that mathematics must be the servant and not the master of theory. However important mathematics might be—and Thomson was keen to get more mathematics into the training of British scientists—equations were not enough. They were somewhat platonic for most, whereas a model however grossly mechanical was easier to handle and more fruitful. Rutherford too asserted that general abstract principles would not do—what he wanted was a concrete idea of the mechanism at work. That, he added, is an attitude of mind that appeals very strongly to the Anglo-Saxon temperament. Both shared a love of improvisation, practicality, above all of simplicity—theories, and the apparatus designed to test them had to be genial, simple, homespun. All the same, did not England have her abstract philosophers too? Alfred Whitehead and Bertrand Russell were bringing out their Principia mathematica in 1910-13, when Rutherford and Thomson were in the thick of their debate on the nature of the atom. Russell andThomson were both Fellows of Trinity College, Cambridge at the time—although neither Russell nor Thomson mention each other in their autobiographies.

Perhaps the difference lies not in the kind of philosophy, but in the role of philosophy within the British culture. In Britain it was regarded as something specialized, too abstruse and difficult for the adolescent mind, and suitable only for those subtle wits who enjoy telling the rest of us why we do not really know what we suppose we know. In most continental countries, philosophy had long been a school subject begun by fifteen or sixteen years of age. In Germany all the sciences apart from those strictly connected to medicine were part of the faculty of philosophy. One leading German physicist, Max von Laue, reflected on the time and thought he had devoted to Kant’s Critique of pure reason since he had been at school; even physics he believed to derive its true dignity only from the fact that it provided an essential resource for philosophy, the centre of the sciences. Einstein was introduced to Kant at thirteen by a medical student who was visiting his family. Thomson in contrast met Kant only when a candidate for a Trinity College fellowship. He was expected to choose a non-mathematical topic for his examination; ‘don’t suppose I really understood Kant’s work’, he wrote, ‘but I enjoyed reading it’.

Some in those days found a difference between the German and other schools in the requirement of a thesis, which British scientists claimed would exaggerate the value of minute and trifling questions. Since the theme of the dissertation has to be narrow enough for the student to master it completely in the time available, he becomes absorbed in the details. Accuracy becomes an end in itself instead of a means to an end—students miss the wood through counting every twig on the trees. However to some bred in the German system, like the physical chemist Ostwald, the benefits were more obvious. The Ph. D. Thesis, he wrote in 1897, ‘trains the student how to master unsolved problems, how to pass from the known to the unknown’. If French science had in his view become too conservative, he considered it was mainly due to the failure of the French to use the dissertation properly. They wasted too much time on examinations. ‘If one has spent the best years of one’s life and most vigorous years of one’s life in assimilating the thoughts of others, it requires unusual energy to give oneself to original thought in later years.’

The French in turn were convinced that their methods were best. Alfred Picard in the Bilan d’un siècle, a retrospect of the achievements of the nineteenth century published as a memento of the 1900 Paris exhibition, declared his pride in French science; ‘Noblesse oblige!’ France must keep her place in the front rank ‘by conserving intact as a sacred heritage the tradition of the national genius, that is to say the spirit of synthesis, simplicity and clear precision’. These virtues the patriot could contrast either with the haphazard fact-finding sorties of the British, who wanted to turn everything into wheels within wheels, or to grandiose woolly theorizing, and niggling accumulations of useless data piled up in German theses and treatises.

Once a young research student at the Cavendish laboratory in the 1920s found the place too much concernd with apparatus and experiment for his taste. ‘And what kind of physics does interest you?’, asked Rutherford, then head of the laboratory. ‘Theories, principles, ideas’ replied the student. To which the professor suddenly asked, ‘Are you by any chance Scotch?’ ‘Yes’ ‘Then go and join the continentals!’ And there’s an irony for you. I might rather say that when discussing the British style in physics—for British read Scottish. For physics in England from the 1870s to the end of the nineteenth century had been made in Scotland—was taught by men, who had gone through the Scottish educational system, out of textbooks written by Scots-Kelvin, Tait, Rankine. The infant English physics was guided in its first steps by Kelvin’s great work on natural philosophy, Maxwell’s on electricity and magnetism; Kelvin, born in Belfast, was educated in Glasgow, and Maxwell in Edinburgh, his native town. Kelvin² declared more than once that he could only truly understand a thing if he could produce a mechanical model; until then it remained to some extent obscure. Both he and Maxwell were very fond of introducing such models, all rods and wheels, into the most abstract realms of physics.

An even purer form of Scots operationalism may be observed in David Forbes, who taught Maxwell, and other teachers of physics of that generation—Stewart, Tait, Rankine—at Edinburgh University. He protested at a natural philosophy that would be ruled by higher mathematics and stood firm by a more elementary and geometrical view of nature. Are the results of experiments and observation, he asked rhetorically, to become ‘mere pegs on which to suspend festoons of algebraic drapery?’³ To a Doric mind, all these refinements were like the swags and tassels of fashionable decoration: they but concealed and spoilt the rugged simplicity of nature. When in after years a French physicist on a visit to Britain complained that instead of a ‘tranquil and ordered temple of reason, we find ourselves in a factory’, he did not realize that neither the taste for geometrical models, picturing every theory as an interaction in three-dimensional space—nor the operational approach that sprang from it—were homegrown at Cambridge. Originally, these habits of thought were no more English than tartan or porridge.

Fig. 1. Distribution of the contributors to science of radioactivity up to 1921.

These ethnic tastes were, of course, not exclusive. Theory and experiment, models and mathematics, were everywhere expected to be in balance: it is just that the balance proved to differ a little from one country to the next. If there sometimes appeared to be a rivalry between these pairs, they were intended to complement each other like the opposed forearms of baby Hercules. Is there anyway too much Eurocentric bias in these comparisons? At that time, although individuals from around the planet were already making their contribution to the international treasury of science—resented by some, the imperial powers of Western Europe still ruled the intellectual as well as the political world. In 1921 a British scholar published a brief history of radioactivity which shows how that science was concentrated in a few countries. At the end of his article he gives data which are summarized in Fig. 1.⁴ The choice of radioactivity does rather distort the comparative ratios of major to minor workers, for example:

In other expanding fields of research, such as X-radiation, relativity, and electrons, ratios more favourable to the German-speaking lands would probably have been found. But then, radioactivity had been the way into the heart of the atom and its energy, the highroad of the new physics.

The only thing we can remember of the infancy of Hercules is that tale of how he strangled twin serpents sent to kill him in his cradle. Our Hercules led a quiet life until his adult years, and nobody sought to suppress him. Yet even in his cot, enthusiastic midwives foresaw the tremendous powers he would exert one day, when he would realize ‘what for the past hundred years have been the daydreams of philosophy’. For a hundred years only? No, the fantasies of all the generations have been given material form; seeing through solid barriers, speaking across the expanse of sea or empty space, changing one substance into another, a source of power and light that seems never to waste away. Hercules or Superman—the atom would fulfil the legends of all time.

The new physics had an intellectually destructive side, almost from the start. Its proponents found themselves engaged in a dispute not only with their own predecessors, but with other branches of science, whose exponents felt threatened by the dissolution of their fundamental principles. There was a curious dualism about the natural philosophy of the late nineteenth century. Nature was made of two kinds of substance: atomic, ponderable Matter, studied by chemists, and continuous, weightless, all-pervading Ether studied by physicists. Young Hercules had first to cast down this dual nature, not so much by strangulation and assault as by absorption, so the two became one, rather as Moses’ rod-turned-snake swallowed up those of rival seers and took their substance into his own. For the scientist, the dream of philosophy was not mighty, magical forces, but the resolution of this difference: throughout that belle époque he sought in this new knowledge ‘the eventual formulation of a theory embracing all phenomena accessible to our senses’.

NOTES

1

Watson, J.D. The double helix, Preface. Atheneum, New York (1968).

2

William Thomson was knighted in 1866 for his work on the Atlantic cable, ennobled as Lord Kelvin in 1892 for his services to physics—the first physics peer. D.S.L. Cardwell remarks that there have been many Thomsons but only one Kelvin. There are obvious possibilities of confusion with Sir Joseph Thomson, who is one of the heroes of this book. So I propose to follow Cardwell’s precedent and speak of Kelvin hereafter, although it is strictly anachronistic to call him so in Chapter 1 and 2.

3

Quoted (from a review article of 1858) by G.E. Davie in The democratic intellect, p. 184. Edinburgh University Press (1961).

4

Lawson, R. The part played by different countries in the development of the science of radioactivity. Scientia XXX 257-70 (1921). Perhaps it is fair to count the British Empire as one unit, when so many Britons taught at colonial universities, and so many colonials worked in the home country, although his category does include Indians. Yet in that case Germany and Austria should be treated as one, since their scientific communities were no less interchangeable. Swiss too often worked in Germany. Lawson used the pre-war borders when Hungary, Czechoslovakia, and much of Poland (including Lwow, an active centre of this kind of research) were all part of the Austrian Empire.

1

MYSTERIOUS ATOM IN MYSTERIOUS ETHER

‘I was brought up to look at the atom as a nice, hard fellow, red or grey in colour according to taste’ said Rutherford once. In colonial New Zealand in the 1880s the atom of the schoolroom had not changed all that much since the days when Newton wrote that matter had probably been formed in the beginning ‘in solid, massy, hard, impenetrable, movable particles’, cannoning off one another in an endless cosmic snooker game. For they were ‘incomparably harder than any porous bodies compounded of them; even so very hard as never to wear or break in pieces; no ordinary Power being able to divide what God himself made one in the first Creation’. These indivisible indestructible atoms were summoned in the seventeenth century from the oblivion in which they had lain since the decline of the Greek philosophy which had first posited them, and they were recalled for much the same purposes as those ancient Greeks had originally conceived them. They were to provide a model of the structure of matter which would enable us to reduce the multifarious qualitative changes of the world to the movements of bodies devoid of all qualities whatsoever save those which can be expressed geometrically. So all the variations and alterations of colour, temperature, texture and shape, growth and decay, action and reaction can be reduced to spatial ones. Behind this lies a problem that has troubled minds since the first Ionian philosophers began to query nature, if not before; what Plato called the opposition between the Same and the Different. What is it that survives unperturbed through all the manifold fluctuations and flickerings of nature? Is there some substrate that does not change, whose movements can explain the variety and instability that we see? The arguments of early atomic physics mark one stage in this ancient debate—but it is only a stage upon the road. Einstein’s vain search for a unified field theory, which occupied much of the latter part of his life (to his friends’ regret) is also part of this quest for an underlying unity, so too is the hunt for the elusive quark or some other sub-sub-particle, which will make sense and Sameness out of the excessive Difference of all our present particles.

Newton made old atomism more realistic by introducing the concepts of mass and force, in addition to size and shape which were all that his ancient predecessors had at their disposal. A hundred years after Newton, John Dalton gave fresh meaning to the atom: he showed how physical sense could be made of the new chemical elements, if it be supposed that these elements, by definition forms of matter that defeat analysis, are composed of Newton’s indestructible atoms, each element having its own particular kind of atom. Then it should be possible to calculate atomic weights by relating the different weights of equal volumes of those elements. By the end of the nineteenth century an immense amount of successful work in chemistry seemed to rest upon this view of atoms, differing in weight alone, yet resisting absolutely any attempt to break them up.

Consider the Periodic System, which helped so wonderfully to impose a straightforward pattern on the confusion of elements. When Dalton’s idea was first accepted, there were about three dozen elements. By 1860 the number had nearly doubled, and as the century drew on more continued to be discovered. Many chemists hoped to find some principle of classification that would reduce the variety. During the early 1860s, laws of octaves, zigzags, and spirals were proposed, to express the repetition of certain characters in groups of elements. Perhaps all had evolved from seven or eight original types, which would match in the organic world that evolution of organisms, whose laws were even then being demonstrated by Darwin and his friends. Among those influenced by such objectives was Dmitri Mendeleev, appointed Professor of Chemistry at Saint Petersburg in 1867. In his new post, he was impressed with the need for a logical system to teach his students about elements. In March 1869 he suddenly found his key, arranging them in order of atomic weight; at every eighth place there was a periodic return to the same chemical properties, particularly those forming compounds with other elements. When Mendeleev was able to predict three elements to fill gaps in his table, which were duly discovered, and possessed the weights and properties he said they should, the utility of his scheme was made obvious. Its reputation was confirmed by his insistence that the weights of some of the elements already known would have to be adjusted in order to fit; for fresh measurements were to prove his estimates right. But was this system merely useful—an aid to discovery, and an aid to memory? Since it depended on weights—and so on mass—it might make more sense if some of the heavier elements were compounds. Yet how could a certain increase of mass bring an element back into line with one much lighter? If chemistry depends on the indivisibility of elements, it must equally depend on the indivisibility of atoms, a ne plus ultra beyond which no man can pass.

Still, however convenient, the atom remained something of an ad hoc proposition. Its very existence was debated throughout the nineteenth century. By the standards of the day no one could produce direct evidence that there were any such things. They might help us picture the basic unities of nature to the mind’s eye—but were they really there? A few were bold enough to argue that all such talk was but a name to cover our ignorance. Relative weights and proportions we know, so they claimed, but not the nature of these atoms, which as individuals we can never perceive. Some still hankered after a prime matter, and thought the larger atoms would turn out one day to be compounds of the smaller. At the outset of the century a London physician, William Prout, had proposed that all were aggregates of hydrogen, the lightest element, but his hopes were disappointed when more precise analysis showed that atomic weights could not be whole number multiples of hydrogen. Whatever might be chosen as the unit, every atomic weight involved a fraction. There might be a remote chance that some lighter form of matter would be discovered, of which hydrogen itself, and all the other elements, would prove to be constructed. So models of the atom were put forward which were more sophisticated than the kind of red or grey (i.e. black and white), billiard ball picture called up by Rutherford’s recollection. The traditional view was certainly still accepted by most scientists, and taken for granted by ordinary educated people who thought they understood the world as science taught it. In their eyes atoms were ‘infinitesimally small, but still finite units of matter impenetrable, indivisible and endowed with enormous energies . . . floating like buoys in an ocean of ether’.¹ So Samuel Laing, ex-MP, ex-railway magnate described the atom, when in old age, in 1889, he sat down to expound his rationalist and agnostic philosophy of man and the universe. For such men, this atom was the sure foundation of material things in an uncertain world. True, he knew of alternatives, and in the end the real nature of the atom remained for him a ‘problem for the future’, still somewhat hard to comprehend.

But the great Maxwell, asked to explain the basic principles of physics for the Encyclopaedia Britannica in 1875, declared that in the atom ‘we have something which has existed either from eternity or at least from times anterior to the existing order of nature’. Indeed the constant masses of each particular kind of atom, and their constant relationships with others, to form molecules, suggested to him the molecules too were permanent. No atoms are now being formed; none now break down. They neither come into being nor change their shape or size; ‘till not only these worlds and systems, but the very order of nature itself is dissolved, we have no reason to expect’ that fresh ones will be manufactured. No less constant were they in their vibrations, and their effects upon others. How could they be made up from random agglomerations of smaller parts, if all were so completely identical, ‘like the nuts and screws of some locomotive or gun factory’, as Laing put it. All the same, could atoms somehow have an internal structure which might explain the details of physics and chemistry? A handful of eccentrics thought so. By now, the number of elements had grown to over eighty. If each had its own atom, how were they distinguished? If an atom of gold is almost four times the weight of an atom of iron, and differs in that alone, is it not four times the size? Why then is it impossible to break down the gold, which can easily be imagined as split into four? Or, of course, assemble a gold atom out of those of iron . . . No, said the great majority, let us dismiss such teasing notions as the fond dreams of alchemy, unsuited to this age of rational common sense.

On Thursday 2 September 1886, the Chemical section of the British Association for the Advancement of Science sat down to hear their President deliver his address. They could expect an exciting display of imagination and agility from William Crookes—editor of Chemical News, director of the Electric Light and Power Company, analyst of London’s water supply, gold-mine owner, fertile inventor, speculative businessman, ardent Theosophist and leading member of the Society for Psychic Research. Always ready with ingenious ways to exploit theoretical discoveries, he was by far the most flamboyant character in British science. With the waxed points of his long moustachios perpendicular over his square grey beard, his very appearance was more showman or magician than sober scientist. His enterprises, like his hypotheses, often failed. Enough succeeded to give him a handsome livelihood, and even left him free to dash in where academics feared to tread. From such a president the audience could hope for fireworks; he always spoke in a blaze of florid metaphors and literary quotations from high romantic verse. They were not disappointed. As the orderly array of atomic elements had grown so very complicated, he began, might not most of them be modifications of some simpler nature? Otherwise confusion would continue to grow worse—or rather, as such a prosy statement was not in Crookes’s style, ‘they extend before us as stretched the wide Atlantic before the gaze of Columbus, mocking, taunting and murmuring strange riddles, which no man has yet been able to solve’. Lamentably he had no evidence that any of them had yet been transmuted to another, but still he felt sure that they were complex. Perhaps if no known elements could be added together to make up the remainder, there was some element of negative weight, possibly the ‘etherial fluid’, which could be subtracted when necessary. Or it may be helium, then known only in the solar spectrum, would turn out to have a weight only a fraction of that of hydrogen. Crookes looked with a kindly eye on these and similar fancies. But the nub, as he saw it, was to conceive this aggregation as an evolution on best Darwinian lines.

In the beginning, so his vision ran, some basic stuff existed—the ‘protyle’ or first matter—in an ultra-gaseous state. ‘This vast sea of incandescent mist’ would be indescribably hot; but then some process akin to cooling makes the scattered particles of the ‘fire mist’ come together. As their coherence requires energy, they must drain it from their neighbourhood, and so chill it down still further. So the protyle over long ages has gradually hardened, first into the lighter elements, successively into the heavier ones. Where they cooled slowly, these elements would be quite distinct. But when they did so rapidly, a group would be born with a close family resemblance, such as the iron-nickel-cobalt group, a little like Darwin’s animal genera, for those that have numerous species resemble one another more than do the species of genera with few.

Fig. 2. William Crookes with Crookes tube.

Crookes’s prime example was the cluster of rare earths. Over the years since Mendeleev had published his table, several had been discovered. No other elements so upset its tidiness, for they just did not fit his columns properly: all were too alike; were to be found only in samples of a handful of rare minerals dug out of a few sites; and no one could guess how many there might be. Crookes himself had devoted much of his time to frustrated efforts to sort them out. Almost every year somebody claimed to have discovered a new one. Usually, he was wrong. Now Crookes could explain this as the curious effect of particularly rapid refrigeration, so these earths had not had time to become true species. The ores which contain them are ‘the cosmical lumber room where elements in a state of arrested development . . . are aggregated’—he means, like chemical Neanderthal men, surviving in odd corners like some Guyanese plateau of Conan Doyle’s Lost World.

As well as the loss of heat, the formation of matter would also bear the impress of electric force, if you imagine that as you descend (in the cooling) you also move from side to side (as in a spiral staircase), swinging across a