Gustave Le Bon is remembered chiefly as the author of The Psychology of Crowds, but by the time F. Legge translated this work into English he had spent the better part of a decade in a laboratory, arguing that the atom is not the solid, indestructible unit that nineteenth-century chemistry had assumed. The Evolution of Matter is an expository scientific treatise — part polemic, part experimental report, part speculative cosmology — built from eight years of Le Bon’s own memoirs and published in English from the third French edition, with Legge’s introduction and notes. Its subject is nothing less than the birth, transformation, and death of matter itself.
“A public domain book is one that was never subject to copyright or whose legal copyright term has expired.”
Le Bon’s central claim is that matter is not eternal. Against the dogma running from Lucretius to Lavoisier, he holds that atoms dissociate spontaneously and under stimulation, that this dissociation releases an intra-atomic energy of staggering magnitude, and that the products of the process occupy a middle ground between ponderable bodies and the ether. The book is arranged in six Books — on the new ideas of matter, on intra-atomic energy and its forces, on the world of the imponderable, on the dematerialization of matter, on the intermediate world between matter and ether, and on the world of ponderability — followed by a second part of experimental researches. Legge notes that the conclusions provoked uproar, especially in France, and that two young Cambridge men attacked the book while conceding the theory was “in the main correct.”
How the Case for a Dissolving Atom Is Built
The Translator’s Framing and Le Bon’s Opening Claims
F. Legge’s preface sets the stage: Le Bon, already famous for The Psychology of Crowds, had turned to physical science about a decade earlier and concluded that all matter is radio-active like uranium and radium—that this activity marks a step in matter’s return to the ether, and that the disintegration slowly liberates energies of unprecedented intensity. The claims provoked uproar, especially in France; two young Cambridge men attacked the book yet conceded the theory was “in the main correct,” disputing only the sufficiency of his experiments and the originality of his doctrine. Over twelve thousand copies had sold in France since June 1905, and Legge appends his own notes under his initials.
Le Bon’s introduction presents the work as the synthesis of eight years of memoirs demonstrating the insufficiency of fundamental scientific principles. Against the doctrine that Matter and Force alone are indestructible, he argues that matter is not eternal and can vanish; that the atom holds a force exceeding all known forces, perhaps the origin of electricity and solar heat; and that an intermediate world exists between the ponderable and the imponderable. He was long alone in these views until radium’s discovery fixed attention on them, and he cites Lamarck on the difficulty of getting new truths recognized, thanking his assistants Michaux, Senechal, and Professor Dwelshauvers-Dery.
Seven Propositions Against the Indestructibility of Matter
The opening chapter traces the dogma of matter’s indestructibility from Lucretius to Lavoisier, and its erosion by cathode rays, X rays, and radio-active emissions. Le Bon had proved that phenomena thought peculiar to uranium occur in all substances, and advanced a theory of the dissociation of atoms which alone resisted criticism; Professor de Heen was the first to adopt it, and J. J. Thomson demonstrated radio-activity in water, sand, clay, and brick. Dissociating matter dematerializes through successive phases back to the ether. He lists seven propositions: matter vanishes by atomic dissociation; its products lie between ponderable bodies and the ether; matter is a colossal reservoir of intra-atomic energy; most universal forces, notably electricity and solar heat, derive from it; force and matter are two forms of one thing; dissociation converts stable matter into unstable energy forms; and chemical species, like living species, are variable. Matter, he argues, is a variety of energy, all phenomena being transformations of equilibrium; atomic equilibria resemble planetary orbits, and a slight loss of matter yields enormous energy. Simple bodies differ only by containing more or less intra-atomic energy. He invokes nebular condensation as the origin of atomic energy, seeks to abolish the duality of matter and force as Faraday attempted, and holds ether and matter to be entities of the same order.
The Neglected Experiments and the General Law
A polarizing apparatus—a metal plate cut with fine lines and covered with Iceland spar—demonstrates double refraction duplicating lines on a photographic plate. Le Bon notes it as one of the most instructive episodes in the history of science that for three years no physicist anywhere thought of repeating Becquerel’s simple experiments on the refraction, reflection, and polarization of uranium rays; instead eminent men published ingenious theories to explain that very refraction and polarization. He compares this to the child with the golden tooth, on which scholars wrote treatises until a sceptic went to see whether the child was really born with it—concluding that in scientific matters prestige is the essential element in conviction, so the Middle Ages, which relied on Aristotle, should not be scoffed at.
Le Bon left the doctrine to its fate and continued his researches, showing that similar radiations arise not only under light but under very varying influences, especially chemical reaction; uranium’s radiations were only a particular case of a very general law. Under divers influences—light, chemical reaction, electric action, and often spontaneously—the atoms of simple and compound bodies dissociate and emit effluves of the same family as cathode rays. This generalization is now almost universally admitted, but formulating it first required courage, since nearly all physicists then admitted, on Becquerel’s authority, the polarization and refraction of these rays. Only after Giesel, Meyer, and Schweidler discovered in 1899 that radio-active emissions, like cathode rays, could be deviated by a magnet did the analogy spread; new facts arose on all sides, and Curie’s discovery of radium gave a great impetus. De Heen, Professor of Physics at Liège, was the first to accept the generalization entirely, declaring Le Bon’s experiments on a par in importance with the discovery of the X rays. Radioactivity was then sought everywhere and found everywhere, and all physicists now class cathode rays and the emissions of uranium, radium, and bodies dissociated by light or heat in the same family.
Generalization, Resistance, and Intra-Atomic Energy
Le Bon explains that the analogies were not at once accepted because generalization is at times harder to discover than the facts from which it flows, yet scientific progress derives from generalizations; he quotes Jevons on vast generalizations revealing deep and subtle analogies. The generality of dissociation would have been noticed sooner had known facts been closely examined, but they lay scattered across very different chapters of physics: the loss of electricity under ultra-violet light, Niepce de Saint-Victor’s observation that uranium salts caused photographic impressions in the dark, the discharge of electrified bodies by flame gases—all consequences of the same fact, the dissociation of matter.
Establishing that dissociation, he says, lets us penetrate an unknown world ruled by new forces, where matter loses its properties, becomes imponderable in the chemist’s balance, passes through obstacles, and possesses unforeseen properties. He has had the satisfaction of seeing recognition while still alive; for a long time he had given up such hope and more than once thought of abandoning his researches. They had been badly received in France: notes sent to the Academy of Sciences provoked absolute storms, the majority of the Section of Physics protested energetically, and the scientific press joined in chorus. People are so hierarchized, hypnotized, and tamed by official teaching that independent ideas seem intolerable. Now that his ideas have slowly filtered into physicists’ minds, it would be ungracious to complain of their criticisms or their silence; sufficient that they have availed themselves of his researches. The book of nature is a romance of such passionate interest that spelling out a few pages repays the trouble; he would not have devoted over eight years to costly experiments had he not grasped their immense philosophical interest and the perturbation they would cause to the fundamental theories of science. With the universal dissociation of matter is linked the discovery of intra-atomic energy, by which he explains the radio-active phenomena—the second the consequence of the first.
Forces Traced to the Atom, and the Origin of Electricity
Matter was formerly deemed inert, merely preserving or restoring energy given to it, yet cohesion, affinity, and osmotic attractions seemed inherent to matter and independent of external agents. Their source was inexplicable under old ideas but ceases to be mysterious once matter is known as a colossal reservoir of energy; since any energy transforms readily, all molecular forces may derive from intra-atomic energy. Electricity and solar heat, origin unknown, also find explanation by this theory.
The Emanations and Their Strange Behaviour
Rutherford’s “emanation” is the next object of scrutiny: a non-electrified product that represents the early stages of dissociation and renders nearby bodies radioactive. It has been studied in radium and thorium; uranium yields too little, though Thomson found that most bodies—water, sand—give off emanations. The emanation is obtained by solution or by red heat, condenses with liquid air (thorium at 120°C, radium at 150°C), and solids emit only a hundredth of what the solution gives. Heating radium drives the emanation off, and its lost activity returns in about twenty days; after red heat a quarter of the activity remains, due solely to alpha particles until the beta rays reappear. The emanation’s activity decays at wildly different rates: actinium in seconds, thorium in minutes, radium over three weeks, halved in four days. Rutherford counts five or six successive emanations. Emanation causes three-fourths of radium’s heat, raising it 3–4°C above ambient; Ramsay found helium spectral lines appearing in it, though the author doubts any radium-to-helium transformation, noting that helium accompanies all radioactive minerals and that this derivative seems to vanish spontaneously. He argues the emanation is semi-material—condensable, dissolvable, yet vanishing into electric particles—an intermediary between matter and ether. Rutherford showed it first yields alpha particles, later beta and gamma; the author finds a purely positive emission hard to conceive. Rutherford compares the emanation’s energy to three million times that of the hydrogen-oxygen explosion. MacClelland confirmed the emanation is uncharged, which the author says demands a re-examination of alpha particles, ninety-nine percent of the emission.
Induced Radioactivity and the Dissociation of All Bodies
Induced radioactivity—emanation projecting particles onto nearby bodies—is blocked by a glass enclosure, produced only by beta and gamma rays, and persists a long time; a negatively charged plate can become ten thousand times more active than thorium, white heat releases it, and Curie found bismuth in a radium bromide solution active for three years. The author compares this to his own phosphorescence experiments, where sulphide of calcium radiated for eighteen months, and rejects the magnet analogy in favour of Villard’s “magnetons.” He concludes that the stages of dissociation are numerous, leading progressively toward the ether. A new chapter opens with his claim that all bodies dissociate, confirmed by Thomson’s emanations from water, sand, clay, and brick; he rejects Elster and Geitel’s “radium everywhere” explanation, citing tin and mercury made active by admixture. Detection relies on particles discharging electroscopes and on magnetic deviation; ninety-nine percent of radium’s emission does not affect plates, and polonium emits only such rays. Light dissociates metals, producing effluves like cathode rays whose charge Thomson measured; ultra-violet is most active, and extreme ultra-violet would make life impossible without atmospheric protection. Solar light cannot dissociate gases, possibly stripping atmospheres like the moon’s. Chemical reactions produce effluves—zinc in sulphuric acid, sodium amalgam, calcium carbide, oxygenated water with manganese dioxide, and quinine sulphate hydration, phosphorescent on heating and radioactive on cooling for minutes, his first chemical-reaction discovery. Kalahne confirmed it; Rutherford’s pupil Miss Gates verified but attributed the activity to ultra-violet light, which the author refutes since phosphorescence outlasts radioactivity. Electric actions produce weak effects; combustion is a maximum source, with Thomson’s incandescent carbon emitting electrons, possibly solar electrons causing the aurora borealis. Heat below 300°C dissociates through a limited emanation-like provision recuperated by repose. Spontaneous dissociation is universal but slow. The invariability of atomic weight, he concludes, is an illusion of insensitive balances, contradicting Lavoisier. Dissociation may cause atmospheric electricity, clouds, and rainfall, dust condensing vapour in Aitken’s experiment. Finally he photographs equilibria of dissociated particles from electrified points, producing lines, prisms, and cells—momentary “materialization”—composed of ions around electric atoms.
Why Slight Causes Can Dissociate Matter
How can stable atoms be dissociated by a mere ray of light? Invisible ultra-violet radiations can dissociate the atoms of a steel block untouched by mechanical forces because they act as a stimulant to which matter is sensitive; the retina does not perceive this stimulant, so light capable of dissociating steel has no action on the eye. Matter insensitive to important actions can be sensitive to minute ones, and imponderable traces of substances may powerfully modify the equilibria of other bodies. On current ideas every atom is a small solar system with a central part orbited by at least a thousand particles of great kinetic energy; disturb their trajectory, or let centrifugal force exceed attraction, and peripheral particles escape along the tangent—radioactivity, offered as a provisional hypothesis. The notion that instability follows from great atomic weight vanishes before his researches: metals with the feeblest atomic weight, magnesium and aluminium, become most easily radioactive under light, while gold, platinum, and lead are weakest. Radioactivity is independent of atomic weight and probably due to chemical reactions of an unknown nature; mercury and tin are weakest under light, yet mercury becomes extraordinarily radioactive when traces of tin are added. The mechanism remains unknown.
Radium, Phosphorescence, and the Chemical Reaction
In radium and thorium no external cause seems to operate. The author has always maintained these phenomena arise from special chemical reactions akin to phosphorescence, between substances one of which is in infinitesimal proportion. Quinine salts, not radioactive, become so and remain phosphorescent when slightly hydrated after desiccation. The disintegration of matter implies changed equilibrium within the atom—intra-atomic change, whereas ordinary chemistry is extra-atomic: chemistry varies the disposition of stones, dissociation transforms the materials themselves. The quantities involved are infinitely small and the energies liberated extraordinarily large, the opposite of ordinary reactions. Pure sulphides of calcium and strontium are never phosphorescent; mixed with small quantities of other bodies they become so. Rutherford and Soddy are quoted as adopting this conception: a radioactive body is in course of transformation, and atoms that have lost something are new atoms. His experiments on invisible luminescence showed phosphorescent bodies retaining, in the dark for two years after sunlight exposure, the property of continuously radiating invisible light that impressed photographic plates. Estimates of radium’s duration vary absurdly—Becquerel a thousand million years, Curie a million, Rutherford a thousand, Crookes a hundred. Dr. Heydweiler, after direct weighings, estimated the loss in five grammes at .02 milligrammes in twenty-four hours, one gramme in 137 years. The author holds even these too high, since spreading the substance over a large surface increases radioactivity; he concludes five grammes probably lose a fifth of their weight in twenty years, a gramme lasting a hundred—exactly Crookes’s figures. Even Rutherford’s thousand years would mean spontaneously radioactive bodies existing in geological epochs would have vanished, supporting his theory that rapid spontaneous radioactivity appeared only since such bodies entered peculiar chemical combinations.
Colloid Metals and the “Inorganic Ferments”
Bredig’s method, plunging gold or platinum rods into distilled water and driving an induction coil between them, throws off a spark that clouds the liquid and leaves it coloured. Beyond the filterable metallic dust, something else appears—a product of metallic dissociation that ordinary chemistry cannot classify. Run the apparatus too long and the formation stops, as though the water were saturated. These colloid metals behave nothing like the metals they came from: a fraction of a milligramme per litre acts with extraordinary energy, the liquid passes through filters unchanged, and no microscope reveals a particle, so the granules must lie below the wavelengths of light. The ionic theory calls them charged granules, yet colloid metal keeps no trace of the original metal; its atoms have likely begun to dissociate. Colloidal platinum is no longer platinum. It resembles the ferments—colloidal platinum decomposes oxygenated water as blood ferments do, turns alcohol into acetic acid like mycoderma aceti, while colloidal iridium breaks down formiate of lime like certain bacteria; prussic acid and iodine paralyse these metals exactly as they poison organic ferments. Garrigou credited mineral waters with their properties through such bodies; Robin injected five to ten cubic centimetres of the solution in typhoid and pneumonia, raising organic exchanges and the output of urea and uric acid, though the solutions alter quickly. Le Bon saw no radio-activity in them, reasoning it need not appear when matter is already dissociated. Protoplasm, he suggests, may be just such a mixture.
Toxins, Catalysis, and the Actions of Presence
Diastases, toxins, and enzymes belong to the same family: chemically unknown, acting by their mere presence, poisonous in imponderable doses. Two drops of tetanus toxin, ninety-nine parts water, will kill a horse; a gramme would kill seventy-five thousand men. Toxins stay active after the bacteria are filtered out, and yeast killed by heat still yields zymase capable of fermentation—so phenomena credited to micro-organisms belong to non-living chemical substances they fabricate, and these bodies lose their powers when deprived of trace mineral matters bordering on the colloidal state. Catalytic actions of presence have long been known: platinum black lets oxygen and sulphurous acid unite into sulphuric acid without taking part, and absorbs eight hundred times its volume of oxygen. Water vapour in tiny doses decides everything—dry acetylene is inert on hydride of potassium but reacts violently with a trace of humidity; traces of steam make dried quinine salts phosphorescent and radio-active. Le Bon’s hypothesis: catalysing bodies undergo commencing atomic dissociation and act as liberators of energy, and platinum black and colloid metals are worn out by use.
Oscillating Equilibria and the Threshold of Intra-Atomic Chemistry
These reactions defy definite and multiple proportions. Bodies, Le Bon argues, are equilibria between internal and external elements, and beyond mass, pressure, and temperature, elements from atomic dissociation create mobile equilibria destroyed and regenerated under slight influences, liberating intra-atomic energy. His phosphorescence studies led him here: pure substances glow only after heating with traces of bismuth or manganese, which provokes dissociation; a blue ray lights a zinc sulphide screen in a tenth of a second, a red ray destroys the glow as fast, repeatable indefinitely. Chemistry stands on the threshold of intra-atomic reactions, where a loss of substance no balance can detect may free great energy. He admits the hypothesis lacks sufficient justification, yet it explains facts hitherto unexplained.
The Birth and End of Matter
Forty years earlier, no scientific line could be written on atomic origins; for two thousand years atoms had been indestructible and eternal. Now matter vanishes slowly. Spectrum analysis answers how: as temperature rises a body’s spectrum reaches further into the ultra-violet, its maximum brilliancy shifting likewise, and Watteville showed potassium’s spectrum changes with the flame region. Nebulae showing only permanent gases are the first phase; condensing, they form stars of varying ages—the whitest and hottest, like Sirius and α Lyrae, almost pure incandescent hydrogen; cooler red and yellow stars show magnesium, calcium, silicium; gold, silver, platinum appear only in the coldest, having lost their intra-atomic energy. Heat may not be the sole cause, for Deslandres showed pressure alters spectral rays. Le Bon cannot name the forces condensing ether into atoms, but the stars prove they exist; Laplace’s nebula, with its rotating nucleus detaching rings into planets, may be mirrored in the atom as a miniature solar system. Only the ether qualifies as cosmic starting point, where worlds are born and return to die. The ultimate term of dematerialisation is the ether itself; electricity is the general form of dematerialisation, and the final products of radio-active dissociation are atoms of electricity.
Sensitising Bodies to Radiation
Bodies otherwise insensitive can be made sensitive. Mercury and tin alone respond faintly; add one-thirtieth of tin to mercury and it becomes a fine reagent for the ultra-violet, responding to hour, day, and season; at ten per cent tin it answers nearly the whole remaining spectrum. Three classes emerge: cadmium, tin, silver, lead sensitive only below 0.295μ; gold, platinum, copper, iron, nickel, organic substances and salts only below 0.252μ. Lamp-black discharges twenty degrees a minute, black paper nearly as much, living leaves least of all. In the solar ultra-violet gold is almost inactive, some five hundred times less than aluminium, yet in the extreme ultra-violet of electric light it nearly matches aluminium. Cleaning matters enormously—uncleaned metals discharge two hundred times more slowly. With condenser sparks, aluminium points produce nearly three times the dissociation of gold points, though Eder showed gold’s spectrum reaches as far as aluminium’s and photographic tests show steel electrodes giving the stronger impression—precisely opposite to their dissociating power. The spectrum of metals, it seems, contains something besides light with which we are unacquainted.
The Vanishing Solar Ultra-Violet
Working in apparently identical weather at the same hour, Le Bon saw the electroscope’s action swing wildly. Only the composition of sunlight remained as a cause, and spectroscope photography of the invisible region confirmed it: from one day to another, sometimes within the same day, the greater part of the solar ultra-violet from the L or M rays abruptly disappeared, always coinciding with slowness of discharge. Bright weather sometimes brought the disappearance, a cloudy sky sometimes left the ultra-violet constant. Had the eye been sensible only from H to U rather than A to H, we should now and then, in full sunshine, be plunged in darkness.
Flames, Effluves, and the Exhaustion of Metals
Branly’s precise research on flames identified their active parts as emitted gases: a platinum wire at dark red heat gave a negative discharge far above the positive, equalised at bright red heat, suggesting ions formed at different temperatures carry different electricities. Le Bon’s electroscope at varying distances from a candle in a closed lantern showed discharge falling from sixty degrees in thirty seconds at ten centimetres to four degrees at thirty, which he attributes to the extreme diffusion of ions. J.
The Atom as a Reservoir of Energy
The intellectual engine of the whole argument is the idea that matter is a colossal storehouse of force. Le Bon reasons that cohesion, chemical affinity, and osmotic attraction — forces the old physics could only describe as inherent to matter — become intelligible once the atom is understood as a reservoir of intra-atomic energy. From this reservoir he derives electricity and solar heat, the two forces whose origin had most baffled his contemporaries. Electricity, on his account, is a constant manifestation of dissociation: matter dissociating liberates intra-atomic energy in electrical form, which is why every chemical reaction turns out to be electrical and why a falling drop or a heated wire can generate a charge. Solar heat follows the same logic — if atoms at the sun’s origin possessed enough energy, a dissociation far faster than radium’s would keep a star incandescent for ages, and the cooling of stars becomes a story of reserves running down.
The objection he takes most seriously is the one Henri Poincaré and Paul Painlevé raised independently: a combination that is extraordinarily stable and extraordinarily endothermic seems contrary to established fact. Le Bon’s answer is that the laws of molecular chemical equilibria simply do not apply to intra-atomic equilibria. The atom is at once very stable, surviving chemical reactions unchanged in weight, and very unstable, since a ray of sunlight can begin its dissociation. The amount lost is a shovelful from a mountain; special phenomena require special laws.
Between Matter and the Ether
Running through the book is a conviction that the sharp line classical physics drew between ponderable matter and the imponderable ether cannot hold. Le Bon describes emanations from thorium and radium that can be condensed like a gas and sealed in a tube, yet in certain phases vanish by transforming into electric particles — a substance half-material, condensable and dissolvable, yet dissolving into electricity. He treats electricity itself as a semi-material substance, and he follows the electron theory back to Faraday and Helmholtz, using the image of a small electrified metal sphere to show how rest, motion, and acceleration of electric particles can produce static attraction, the magnetic field, induction, and the electromagnetic waves that constitute light. Zeeman’s splitting of spectral lines in a flame, yielding the same charge-to-mass ratio as cathode particles, becomes for Le Bon the experimental bridge between ordinary fire, cathode rays, and radio-active bodies.
Chemical Species Are Not Fixed
The biological analogy in the title is deliberate. Le Bon argues that chemical species, like living species, are variable — that the fixity of the elements was an illusion of insensitive balances. The rare-earth metals, distinguishable only by physical properties and separable only by fractionation, blur the boundary between elements; allotropism, once thought exceptional, becomes a general law, with white and red phosphorus differing in melting point, toxicity, and appetite for oxygen while yielding the same acid. He extends the argument to crystals, which he presents as beings intermediate between brute and living matter, passing through a cellular infancy to a crystalline adulthood and showing both spontaneous generation and generation by affiliation. Colloid metals — platinum and gold so finely divided that they act as “inorganic ferments,” decomposing oxygenated water like blood ferments — carry the point further: their atoms have probably begun to dissociate, and they are no longer quite gold or platinum.
What the Book Meant
Legge’s preface records that over twelve thousand copies sold in France within two years, and that Le Bon, long isolated, lived to see the facts on which his theories rested accepted. The book’s historical interest lies in that vindication and in its cost: Le Bon describes notes sent to the Academy of Sciences provoking “absolute storms,” and remarks that people are so hypnotized by official teaching that independent ideas seem intolerable. Some of his positions have not aged well — he doubted that radium would ever be isolated and questioned the transformation of radium into helium — but the wager that matter is mutable, that the atom holds forces exceeding any known, and that the boundary between matter and ether is porous, is the wager modern physics would take up. The book is a record of a scientist arguing against a consensus, and of the consensus slowly giving way.
