Becquerel-Henri · Source catalogue

Three scanned pages of Nature; Step 0 OCR'd them (the PDF has no text layer), and the deep read used the OCR text plus a page image for the numbers. Page 396 is mostly unrelated letters (ash of Lakeland leaves, an earthquake, an obituary query) and opens Becquerel's own article. Becquerel gives a first-person account of the discovery: in early 1896 he found that uranium salts emit an invisible radiation that crosses metals and opaque bodies, blackens a photographic plate, and discharges electrified bodies. He states the emission is not affected by temperature or light excitation, is not phosphorescence, is not weakened appreciably after several years, and is bound to the element uranium (metallic uranium discharges electrified bodies about three to four times faster than its salts). He reports that early experiments suggested light-like properties (straight-line propagation, 'edges of shadows') but later work showed no reflection, refraction or polarisation. He reviews the work of Kelvin, Beattie and de Smolan (1897), Rutherford (1899, ionisation of gas; alpha and beta types), Mme Curie and Schmidt (thorium, 1898), the Curies' discovery of polonium and radium (and Debierne's actinium), the induced radio-activity of bodies near radium, and the work of Giesel, Meyer and von Schweidler, Becquerel and the Curies on magnetic deviation. He describes his own magnetic-spectrum experiments: a radium source in a small lead dish on a photographic plate between electromagnet poles; the deviable rays trace elliptic arcs (a 'magnetic spectrum'), different screens (aluminium, copper, platinum) absorb different parts; absorption is the same in air and in vacuum. He reports Hrho = 1600 and a velocity about 1.6 x 10^10 cm/s (about half the speed of light) for a particular radiation, a charge-to-mass ratio of about 10^7 (electromagnetic units, matching cathode rays), deflection in an electric field (parabolic path) consistent with negative charge, and a measured current of about 4 x 10^-13 electromagnetic CGS units per square centimetre (Curies' screen experiment). From these he estimates that if the emission is material, each square centimetre of radiating surface loses about 1 mg in 1000 million years, so there is no contradiction between the apparent absence of an energy source and continuous emission. He notes the most deviable portions are stopped by bodies near the source, that radium phosphorescence intensity varies inversely with distance squared, that radium restores thermoluminescence to heated fluorspar, that uranium activity might be due to a small quantity of actinium or another active body (Crookes's uranium-X work), and concludes that 'a new order of phenomena has arisen from the study of a new property of matter - radio-activity'. The OCR and the digest garble the exponents (the digest gives 1.6x10^8 and 4x10^-7); the page image gives 1.6x10^10 (units not printed; cm/s by consistency), m/e = 10^-7 (m/e, not e/m) and 4x10^-13 emu per cm^2. Additional deep-read points: (a) Becquerel writes that the non-deviable (polonium-type) rays are 'much less penetrating than the deviable rays' (limited in air to a few centimetres), and separately reports Villard's 'very penetrating rays which are not capable of deviation'; in modern terms alpha < beta < gamma, though he does not use those names and says the non-deviable kind's 'nature is still unknown'. (b) Radium salts 'increase spontaneously in activity for some time after their preparation' while polonium salts lose activity (Curies, Giesel). (c) Giesel's deviable 'polonium' was not the Curies' (non-deviable) polonium. (d) Rutherford's thorium emanation activity can be concentrated on a negative wire and removed by hydrochloric/sulphuric acid, leaving the activity in the evaporated residue. (e) The Curies' products were 'several thousand times' as active as uranium; the 100,000 figure is not in this article. (f) The exact sentence on uranium: 'the activity of uranium is due in great part, if not altogether, to a small quantity of actinium or of another radio-active body.'

Key claims

• Uranium and its salts spontaneously emit a penetrating radiation that blackens photographic plates and discharges electrified bodies, without any prior light or heat excitation.
• The emission is bound to the element uranium (metallic uranium discharges electrified bodies three to four times faster than its salts) and is not weakened appreciably over several years.
• Radium radiation includes a magnetically deviable component that behaves like cathode rays (negative charge, m/e about 10^-7 emu, i.e. e/m about 10^7 emu/g; velocity 1.6 x 10^10 cm/s, about half that of light, for the Hp = 1600 radiation).
• The non-deviable component is a separate, much less penetrating kind (polonium-type, stopped by black paper or a few cm of air; later alpha), and Villard has shown a further very penetrating non-deviable radiation (later gamma).
• If the emission is material, the mass lost is about 1 mg per square centimetre per 1000 million years (from a measured current of about 4 x 10^-13 emu per cm^2), so continuous emission is not obviously in contradiction with the lack of an energy source (Becquerel's own argument).
• Radium salts increase in activity for some time after preparation while polonium salts decline; bodies near radium or thorium acquire temporary induced radioactivity that can be concentrated on a negatively charged wire and removed with acids.
• Becquerel suggests the activity of uranium is due 'in great part, if not altogether' to a small quantity of actinium or another radioactive body (a conjecture, based on Crookes's nearly inactive uranium and work by Debierne and Giesel).
• Radium's activity after the Curies' concentrations was 'several thousand times' that of uranium (the 100,000 figure appears only in the Harper's and Thomson texts).

Relevance: Primary source: the discoverer's own 1901 summary of radioactivity. It shows the state of the field in 1901 (before the Rutherford-Soddy transformation theory was widely accepted) and the first quantitative energy-budget worry about spontaneous emission. Central document for claims 1-5.

Mainstream conflict: None for the core findings, which are the foundation of nuclear physics. The 1901 framing (material emission of corpuscles at negligible mass loss, no known energy source, 'induced radio-activity' as a separate property, possible actinium impurity in uranium) was later superseded by nuclear decay and mass-energy equivalence.

Twelve-page web printout (dated 1/17/2020) with a good text layer; a good text layer; digest of all pages, with spot checks against the full text; figures not examined as images. A popular account for general readers, with a florid, quasi-religious opening. Describes Becquerel's family of physicists, the lead-up from Roentgen's X-rays and Niewenglowski's calcium sulphide experiment (rays from sunlight-exposed phosphor penetrating metal), then Becquerel's uranium experiment on a photographic plate wrapped in black paper (copper cross, aluminium medal). It says Becquerel found emission was spontaneous, independent of prior light exposure and of phosphorescence, and that metallic uranium emitted most. It narrates the Curies' search for the source of pitchblende's extra activity (4x uranium; fractions up to about 100,000x), with the discovery of polonium, radium and actinium; radium never isolated, exists as a new element by Demarcay's spectrum; less than a gram exists, worth about $10,000 per gram. It lists the properties: penetration depends on density, phosphorescence of diamond, ruby, fluorspar; self-luminous radium; light seen through closed eyelids; radium burns on Pierre Curie's arm and in Becquerel's pocket; electroscope discharge by ionisation of air; induced radioactivity of nearby bodies; chemical effects (ozone, glass colouring, phosphorus conversion). It describes the magnetic deflection experiment (lead trough on plate between electromagnet poles, polarity reversed), a 'spectrum' of unequally deviable rays, and a deviable plus non-deviable split. A property table concludes that deviable rays equal cathode rays and non-deviable rays equal X-rays. The author argues radio-activity is a natural intrinsic property of matter, not a property of condition. Corpuscles from radium travel at '60 to 90 million miles per second' (an apparent unit slip: that exceeds the speed of light; the Nature file gives about half light speed), and he quotes Huxley on evolution of elements from primitive matter. It ends with Mme Curie's speculation that radium receives its energy from radiations traversing all space ('sympathetic vibration', 'harp of life'), a rhetorical flourish presented as uncertain ('Heaven only knows'). Corrections to the digest (checked against the text by QE): it is Pierre Curie who applied radium to his arm for about 1.5 hours (a sore lasting over three months) and Becquerel who carried radium in his pocket; 'less than a gram' of radium exists (not 'fewer than 3 grams'); magnetic deflection belongs to the deviable rays only.

Key claims

• Radio-activity, the spontaneous emission of penetrating rays by uranium and radium, is a natural intrinsic property of matter, not a property of external conditions like light-induced phosphorescence.
• Becquerel rays from radium are a mixture of a magnetically deviable component identical in properties to cathode rays and an undeviable component identical to X-rays.
• The particles in the deviable component are corpuscles smaller than atoms and are fragments of decomposed atoms; the passage quotes Huxley that the elements may have evolved from a primitive form of matter.
• Bodies placed near radium acquire a temporary induced radioactivity that cannot be washed away.
• Mme Curie suggested radium may draw its energy from radiations that traverse all space (speculation, unsupported).
• The Curies' fractions reached about 100,000 times uranium's activity (a Harper's figure; Becquerel's own 1901 text says 'several thousand times').

Relevance: Shows how the discovery was understood and popularised in 1902, including the energy-source puzzle and the Curie 'space radiation' idea that later alternative-science readers sometimes cite as precedent for external-energy explanations.

Mainstream conflict: Superseded details: the claim that undeviable rays are X-rays and the deviable are the cathode-ray (electron) type is partly right (beta = electrons) but omits alpha particles and gamma rays; the 'energy from space radiation' and 'decomposed atoms' ideas conflict with the later nuclear-decay explanation; the quoted speeds exceed light speed and are a unit or transcription error.

Six-page web printout with a good text layer; full text read. Thomson, discoverer of the electron, gives a lay account. He recounts Becquerel's cloudy-weather accident: uranium put in a drawer gave a stronger image, and Becquerel's dark dissolve-and-recrystallise test showed the emission was intrinsic. He says Becquerel at first thought his rays refracted and polarised, but later work showed otherwise. He states Becquerel rays are a mix of Roentgen and cathode rays (beta = deflected, carrying negative charge; alpha taken as Roentgen-like) and says cathode rays are corpuscles with charge and speeds up to over 120,000 miles per second (consistent with Becquerel's Nature value). Thorium was found active by Schmidt. He recounts the Curies' extraction of polonium, radium (with Bemont) and actinium (Debierne). He computes that radium's emission of charge implies a mass loss of about one-thousandth of a milligram per million years per square centimetre, and an energy output enough to melt a quarter-mile layer of ice in a million years, and asks where the energy is stored. He gives the Rutherford-Soddy answer: thorium continually produces active thorium X, which decays; growth and decay half-times match (the 'infants' analogy), so the substance is transforming to a lower-energy state. He mentions Becquerel's barium-precipitation experiment (activity moved to barium, regained by uranium after twelve months), Crookes's separation of uranium into an active and inactive part, thorium emanation (inert gas), the link to helium, induced activity from emanations, and Elster and Geitel's finding that negatively charged wires in open air become radioactive. Thomson then offers his own alternative explanation: positive ions accumulate on a negatively charged body and pull electrons out as cathode rays, so objects can become radioactive without radioactive substances; he concludes lightning-rod points and leaves are cathodes discharging cathode rays into air. Deep-read additions: Becquerel's barium result is reported as an accident ('fortunately he kept his solutions'): about twelve months later the uranium solution 'had recovered all its former activity' and the barium was 'absolutely inert', with no numbers given. The Rutherford-Soddy test is a stated criterion (time to lose half the activity equals time to regain half), 'satisfied with great exactitude' but with no figures. The helium remark is only that helium 'may be very closely connected with' the emanation. The rain finding (freshly fallen rain radioactive for about an hour) is credited to C. T. R. Wilson, not Elster and Geitel; Elster and Geitel found that negatively charged bodies in open air become radioactive within hours. Thomson's own ion-layer hypothesis comes with no data, only 'some experiments' he 'recently made', and hedges ('I think', 'in all probability'). His energy figures for radium rest on Curie's charge data with no working shown. Thomson says radium freshly prepared is not nearly as active as it later becomes.

Key claims

• Radioactivity is the spontaneous transformation of a substance into one with less energy, and the energy carried off by radiation comes from that transformation (Rutherford and Soddy's thorium X experiments).
• The rate of loss of activity of a separated product equals the rate of recovery of the parent, as tested by Rutherford and Soddy 'with great exactitude'.
• Radium's radiation carries away mass and energy at a rate (about 0.001 mg per million years per cm^2; enough to melt a layer of ice a quarter-mile thick per million years) that implies a large internal energy store.
• Induced radio-activity on negatively charged bodies in open air is produced by positive-ion layers pulling out cathode rays, without any radioactive substance present (Thomson's own hypothesis).
• Beta rays are cathode-ray corpuscles; alpha rays are Roentgen-like (a 1903 position, later corrected).
• Uranium's activity, transferred to barium by precipitation, returned to the uranium solution after about twelve months while the barium became inert (Becquerel; reported by Thomson without numbers).
• Helium may be closely connected with the gaseous emanation of radioactive substances (a suggestion, no experiment).

Relevance: Documents the key 1902-03 shift from 'mysterious inexhaustible emission' to 'energy stored in the atom and released by transformation', and contains a rare wrong turn by a Nobel laureate (induced radioactivity without radioactive sources) that is instructive for the review.

Mainstream conflict: The Rutherford-Soddy transformation theory is mainstream. Thomson's ion-layer 'cathode' hypothesis for atmospheric radioactivity and the identification of alpha rays as Roentgen rays were later superseded: alpha rays are helium nuclei, and the induced activity from open-air wires is explained by deposition of decay products of radon (emanation) [memory: high confidence].