Tyndall-John · Source catalogue

Tyndall's own research paper (primary source) on the invisible, extra-red radiation of the electric arc and what it can do. Part 1 measures the distribution of heat through the prismatic spectrum of the arc (50 Grove cells) with a linear thermopile and a rock-salt optical train: heat is already 44.6 per cent of the maximum at the extreme red, the maximum lies in the dark beyond the red, and the invisible part outweighs the visible part by 7.7 times (planimetry of the mean of more than a dozen curves, Fig. 3). The sun's invisible radiation is given as about twice the visible (Muller), the difference being ascribed to absorption by atmospheric water vapour. Part 2 describes the filter that makes the rest possible: iodine dissolved in bisulphide (disulphide) of carbon, which stops all visible light but passes the extra-red. A 2-inch bisulphide cell passes 94.8 per cent of the arc's heat (after conversion from galvanometer degrees by an unpublished calibration table); the iodine absorbs 11 per cent (50 cells) or 13.2 per cent (40 cells), which he takes to be the luminous share, so invisible/visible = 89/11, about 8, agreeing with the spectrum-area result 7.7. Table III (taken from his Nov 1864 Phil. Mag. paper) shows the iodine absorbs nothing from dark or red-hot sources and 10 per cent from the arc. Part 3 reports what the filtered 'dark' beam does when concentrated by mirrors, flasks or lenses: it lights matches and gunpowder, pierces and inflames black paper, fuses non-refractory metals, burns zinc and magnesium, and raises platinized platinum foil, carbon, silver and copper leaf to red or white heat, in air and in vacuo (so not mere combustion). Controls against stray light include an alum cell (passes light, blocks dark heat) and an undefended-eye test (a platinum plate placed where the retina had been glowed vividly while the eye saw no light; footnote: 'I do not recommend the repetition of these experiments'). A bisulphide prism shows the white-hot platinum glow to have a complete spectrum from red to violet. Tyndall interprets this as raised refrangibility: heat-rays transmuted into light-rays by the platinum, the reverse of Stokes's fluorescence, and names it 'calorescence'. Lime-light gives the same effect, and the Sun's dark rays (3-foot mirror at the Royal School of Mines and at Chislehurst; hollow lens; Mayall's photographic lens at Brighton) gave only a bright red heat. He failed to fuse platinum ('hitherto without success'), attributing this to loss of the absorbing platinum-black layer. Other items: a paper-colour table (black pierced and set ablaze, red paper barely charred: dark colour is not always the best absorber); a coloured-glass table; an 'extremely remarkable' pink glow of the platinum behind certain blue glasses, which he leaves unresolved ('further experiments ... are necessary to satisfy my own mind'); the observation that carbon black glass can transmit 63 per cent of the arc's heat, from which he concludes that black-bulb thermometers are defective; a carbon-disulphide fire on 2 November (apparently 1864) that engulfed the lamp, twice repeated. The assistant Mr. Barrett executed the numerous experiments.

Key claims

• In the arc-lamp spectrum (50 Grove cells) the maximum heat lies beyond the red in the dark, and the invisible radiation is about 7.7 times the visible by area, 8 times by the filter-subtraction method.
• The sun's invisible radiation is about twice its visible radiation (Muller's curve), and the lower ratio is due to aqueous vapour in the atmosphere (Tyndall's inference; passing the arc beam through a water layer reproduces a solar-like distribution).
• A solution of iodine in bisulphide of carbon (about 2.3 inch layer) stops all visible light yet transmits about 87-89 per cent of the arc's total heat; the iodine absorbs 0 per cent from dark and red-hot sources, 3-4.6 per cent from flames and white-hot platinum and 10-13 per cent from the arc.
• The filtered, concentrated dark rays ignite combustibles, fuse non-refractory metals and raise platinum, carbon, silver and copper to red or white heat, in air and in vacuo.
• This glow is a conversion of heat-rays into rays of higher refrangibility ('calorescence'), the reverse of Stokes's fluorescence rule, and the white-hot platinum shows a complete spectrum from red to violet.
• Platinum could not be fused with the dark rays of the arc (100 cells, two lamps), but was brought to the verge of fusion with a lampblack coat; the sun's dark rays gave only a bright red heat.
• Black paper absorbs the dark rays most and red paper almost none, and white absorbs more than red; the popular notion that dark colours are the best absorbers is not generally true.
• Carbon-black glass can transmit 63 per cent of the arc's total heat, so black-bulb thermometers made with it do not absorb all solar radiation.
• Behind certain blue glasses the calorescent platinum glows pink, which (if confirmed) would mean a gap in the calorescent spectrum with platinum vibrating in red and blue periods only; Tyndall himself says this needs confirmation.
• No discontinuities (maxima and minima) were found in the electric-light heat spectrum, unlike Herschel's drying-power spots in the solar spectrum.

Relevance: The foundation of the invisible-radiation experiments and of the term calorescence; the iodine-bisulphide filter and the 7.7/8 ratio recur in On Radiation (1865), Heat (1868) and Six Lectures on Light (1872-73). It is the best-documented primary experimental record in the folder for the dark-focus and raised-refrangibility claims.

Mainstream conflict: The measured facts (large invisible share of a hot source, ignition at an infrared focus, strong infrared transmission through carbon black glass) are consistent with modern radiation physics [memory, high]. The interpretation as 'raised refrangibility' of the incident rays is not the modern reading: a body heated to incandescence by absorbed infrared emits its own thermal spectrum [memory, high]; the paper itself carries both a thermal-emission picture (p.3, p.7) and the raised-refrangibility picture (pp.17-18) without reconciling them (reader observation in the deep read). The luminiferous-ether language is outdated. The pink-glow result is unexplained by Tyndall.

Tyndall's popular statement (primary source, his own words) of the radiant-heat programme to a Cambridge audience, in 16 numbered sections. Sections 1-3 give the vocabulary: the optic nerve responds to a narrow band; hotter bodies add shorter waves while the longer ones persist; light and radiant heat are wave motion in the luminiferous ether; an atomic theory implies that combined and uncombined atoms behave differently toward the ether. Section 4 and the Table 'Radiation through Gases' (air = 1, gases at 1/30 atmosphere, copper-plate source, compensated thermopile, rock-salt windows): oxygen, nitrogen, hydrogen and air 1; carbonic oxide 750; carbonic acid 972; hydrochloric acid 1005; nitric oxide 1590; nitrous oxide 1860; sulphide of hydrogen 2100; ammonia 5460; olefiant gas 6030; sulphurous acid 6480. The elementary gases are 'practical vacua' to radiant heat although all the gases are transparent to light. Sections 5-9 and 16 recapitulate the dark-focus work: the iodine filter (shown at the Royal Institution early 1862), combustion at dark foci, 'a kind of Matterhorn of heat' beyond the red, the statement that the electric light's visible rays would give one-ninth of the heat at the unseen focus, calorescence, the undefended-eye test (platinum at the retina's position red-hot; no sensation of light or heat), and ox-eye measurements (18 per cent of the obscure rays reach the retina). Section 10 reports Draper-type persistence tables (obscure radiation rising by a factor of about 440 from dark to intense white). Sections 11-15 are the vapour, perfume, atmosphere and reciprocity results: vapours of volatile liquids at 1/30 atmosphere (bisulphide of carbon 47 to acetic ether 612); perfumes carried by dry air (patchouli 30 to aniseed 372 times the air); atmospheric vapour 'would certainly be an understatement' at 100 times air and perhaps 200 times; a 10-foot column of ordinary air intercepts 10-15 per cent of obscure heat; the dry-climate cooling argument (India, Himalaya, Central Asia, Australia, Sahara); a two-inch shell of air saturated with sulphuric-ether vapour would intercept 35 per cent of the earth's radiation ('proved by experiment', no experimental detail given); water-layer comparison ('one-tenth of an inch passes the sun's rays; half that thickness stops every terrestrial ray'). Reciprocity: absorptive and radiative power go together, with the 'dynamic radiation' technique; carbonic acid absorbs 60 per cent of a CO flame's radiation at 1/10 atmosphere in a 4-foot tube; dried human breath absorbs 50 per cent, and the physical (thermopile) analysis of breath CO2 (4.58, 5.22 per cent) is compared with Frankland's chemical analysis (4.66, 5.33). He concludes that period alone does not explain the differences and that molecular shape, size and complexity matter. It closes with a piano/voice analogy and the line 'thus is sentient man sung unto by Nature'.

Key claims

• At 1/30 atmosphere oxygen, nitrogen, hydrogen and air absorb almost no radiant heat, while ammonia absorbs 5460, olefiant gas 6030 and sulphurous acid 6480 times as much as air (copper-plate source).
• Elementary gases are practical vacua to radiant heat; chemical union of the same atoms (nitrous oxide 1860) raises absorption enormously although the compound is as transparent to light.
• The electric light's visible rays would, if converged, give only one-ninth of the heat of the invisible rays at the unseen focus.
• Atmospheric aqueous vapour acts on radiant heat about 100 to 200 times as strongly as the air carrying it, and a 10-foot column of ordinary air intercepts 10-15 per cent of heat from an obscure source (rough estimate with no experiment cited in the lecture).
• Dry-climate temperature extremes (India, Himalaya, Central Asia, Australia, Sahara) are caused by the absence of aqueous vapour that otherwise checks the earth's heat loss; this vapour 'wrapping the earth like a warm garment' makes the planet's mean temperature higher than distance from the sun alone would give.
• A two-inch air shell saturated with ether vapour would intercept 35 per cent of the earth's radiation; the order of absorption of ten liquids is the same as that of their vapours, so water must be the strongest absorber (inferred, no direct water-vapour measurement in the table).
• Radiative power equals absorptive power: gases and vapours that absorb strongly radiate strongly when heated, including 'dynamic radiation' of gases warmed by compression or collision.
• Differences between molecules are not explained by vibration period alone; the shape, size and complexity of the molecule also matter.
• Carbonic acid gas in a 4-foot tube absorbs 48 per cent of the radiation of a carbonic-oxide flame at 1/30 atmosphere and 60 per cent at 1/10 atmosphere.
• Physical analysis of dried human breath by radiant-heat absorption (4.58 and 5.22 per cent CO2) agrees with Frankland's chemical analysis (4.66 and 5.33 per cent).

Relevance: The shortest complete statement of the gas, vapour and atmosphere programme, with the water-vapour climate argument already in its popular form. Together with Heat (1868) chapters X-XII it is the primary source for the greenhouse-type claims. Several of its numbers differ from the 1868 text (see deep read section 12).

Mainstream conflict: The measured contrast between N2/O2/H2 and polar or polyatomic gases, and the role of water vapour and CO2 in absorbing terrestrial infrared, are consistent with modern atmospheric physics [memory, high]. Differences from modern practice: ether-based explanation; the one-tenth-inch water statement is stronger than Heat's own data; the 35 per cent ether-shell and 10-15 per cent ten-foot figures are stated without experimental detail in this lecture.

Tyndall's own textbook-lecture series (primary source; 724 numbered paragraphs, 14 chapters, dedicated to Bunsen). It carries the dynamical theory of heat and, in Chapters IX-XIV, the radiant-heat research. Chapters I-III: demonstrations that friction, percussion and compression make heat and expansion consumes it; the material (caloric) versus dynamical theory; Rumford's cannon-boring memoir (cylinder of 113.13 lb gun-metal, 837 grains of dust, water in the box 60 F to boiling in 2 h 30 min, heat equal to 26.58 lb of ice-cold water to boiling) and Davy's friction-melting of ice; Mayer-style calculation of the mechanical equivalent from the expansion of a cubic foot of air (2,160 ft-lb through one foot; 9.5 lb minus 6.7 lb = 2.8 lb of water-degrees; 771.4 ft-lb per lb per degree F) set beside Joule's results (1843 values 587-1,040; paddle wheel 890; 1849 means 772.692, 774.083, 774.987; fixed at 772), and Clausius's molecular speeds (O2 1,514, N2 1,616, H2 6,050 ft/s). Chapter VI: snow, glaciers, regelation (Faraday, June 1850), the pressed-ice experiments; Tyndall grants ice a viscous-like behaviour under pressure but not under tension, cites 'the most delicate experiments' that failed to detect stretching (no source given), and argues that ancient glaciers show the action of heat (vapour supply) as much as cold. Chapter IX: inverse-square law for radiant heat (Melloni's cone explanation), Leslie's cube (radiation depends on surface substance, not colour, for obscure heat), reciprocity of radiation and absorption, Melloni's diathermancy tables (25 solids, 19 liquids; rock salt 92.3 per cent), thinning plates, 'sifting'. Chapter X (core experiment): a 4-foot polished brass tube with rock-salt windows, a boiling-water cube as source, a second face of the pile balanced by a compensating source, so that a tubeful of dry air gives about 1 degree and olefiant gas gives 70 degrees. Galvanometer degrees are turned into heat units by a calibration (30 deg = 30; 40 = 47; 50 = 80; 70 = 211; 75 = 276; Melloni shunt method in the appendix). Tables: olefiant gas by pressure (1 inch 90 ... 10 inches 193); proportionality at very small doses; sulphuric ether 214-330; carbonic oxide; radiation equals absorption (CO 12/18, CO2 18/25, N2O 29/44, olefiant gas 53/61); relative absorption at 30 inches (CO2 90, olefiant gas 970, ammonia 1,195) and at 1 inch (CO2 972, ammonia 5,460, olefiant gas 6,030, sulphurous acid 6,480); vapours at 0.1, 0.5 and 1.0 inch (bisulphide 15/47/62 ... acetic ether 590/980/1,195; boracic ether 620 at 0.1 inch); open-air vapour swings. Air value is assumed (1 degree), not measured; Tyndall says 'tens of thousands' of trials were needed and that drying agents and cork dust spoiled results. Chapter XI (deep-read part): aqueous vapour. Room air acts 72 times as strongly as dry air (48 degrees = 72 units); 70 times for air from seven country and seaside sites; 90 times for purified air humidified with distilled water; first result 'fifteen times' rose as the dry-air reference was purified. He answers six listed objections (brine film on the rock salt, invisible film, caprice, London soot, wall condensation, the tube itself) with a closed tube, an open tube with a gentle air displacement and free-air tests (saturated air 5 deg toward opacity, dry 10 deg toward transparency); a humid-air table 5-30 inches Hg (16-98) shows proportionality to the amount of vapour. Absorption in a 4 ft 3 in open tube is 7.9 per cent; in a 4-foot polished tube over 10 per cent on an average-dry day, from which he infers 'at least 10 per cent' of the earth's heat is intercepted within ten feet of the ground. Per molecule he gives 16,000 (80 x 200). He cites Strachey's night-cooling series (vapour tension 0.888 to 0.435 inch; night fall of the thermometer 6.0 to 16.5 degrees), Leslie's aethrioscope anomaly, Martins and Bravais (24 F against 10 F difference between radiating and shielded thermometers on Mont Blanc and Chamouni), Hooker, Livingstone, Jevons/Sturt, the Sahara ('Ice has been formed in this region at night' - no source), tropical rain, cumulus, the 'blanket' and 'dam' images. Magnus is the named critic ('it was evident beforehand that such vapour could exert no sensible action'). No numerical split between water vapour and CO2 is given; CO2 is about 0.05 per cent and water vapour 0.45 per cent of the air in his round figures; Frankland's demonstration showed vapour a better radiator than CO2. Chapter XI paragraphs 435-466 (deep read, QE): perfumes (17 oils, patchouli 30 ... aniseed 372 times the air; herbs 32-53), ozone from electrolytic cells (20, 34, 47, 65, 85, 136 times the carrying electrolytic oxygen, rising as electrodes shrink and with cooling; ozone amount unmeasured), 'dynamic radiation and absorption' (gas heated by entering air radiates; chilled by pumping absorbs; 11 vapours, radiation 14-70 against absorption 6-43, same rank order), boracic ether diluted to about 1/151,875,000,000 atmosphere still giving 10 degrees against 7 for air alone, and the long/short column test (olefiant gas keeps 0.62 of its radiation in a 3 inch tube, the ethers 0.17-0.21). Chapter XII (deep read, QE; image-checked): liquid absorption table (0.02 inch: bisulphide 5.5 ... water 80.7 per cent), vapours at common pressure, the 'equal quantity' correction (para 512-515: liquid and vapour rank order identical for ten liquids; water vapour could not be examined, so water is an inference), source-temperature tables (absorption of every vapour falls as the platinum spiral is heated; a 212 F Leslie cube is absorbed most; formic and sulphuric ether swap order), flames, and the hydrogen-flame series: undried laboratory air in a 4 ft polished tube absorbed 17.2 per cent of the hydrogen flame's heat (20.3 per cent some days later, on a 'humid day'), 5.8 per cent of a glowing platinum spiral and 8.6 per cent of the spiral plunged in the flame; CO-flame series (CO2 48.0 ... 74.3, olefiant gas 23.2 ... 65.5 per cent at 1 ... 10 inches), breath CO2 by radiant heat (three pairs against Frankland's chemistry: 4.311/4.00, 4.66/4.56, 5.33/5.22), hydrogen-flame heat through water layers (0.02 inch transmits 5.8 per cent; 0.27 inch 0.0), the 'olefiant gas shell' (1 inch absorbs 26 per cent) and the 'ether shell' (2 inch layer cuts 'fully 35 per cent' of planetary radiation; 'I find', no table) argued against a work that held the distant planets uninhabitable, and the hydrogen flame's extra-red spectrum. Internal inconsistencies printed in the book itself are listed in the deep read (formic and sulphuric ether values swapped between p.416 and p.423; hydrogen-flame water transmission 2.8/1.1 on p.434 against 5.2/2.0 on p.436). Chapter XIII (deep read, QE): luminous fractions of the radiation (white-hot platinum 1 part in 24 [the table gives 4.6 per cent absorbed by iodine, about 1 in 21.7], coal-gas flame 1 in 25, electric light 1 in 10 and, with 50 Grove cells, 89 transmitted/11 absorbed, so 'eight times'), Tyndall's test of Melloni's alum assumption (concentrated alum transmitted 20 per cent of the obscure heat that had passed the iodine; this corrects Melloni's alum method, not the iodine or prismatic-area figures), the ox-eye result (one fifth of the obscure rays of the electric light reach the retina; nearly two-thirds of the total radiant energy reaching the retina cannot excite vision), and the solar trials (only one dated: 15 November 1864, cloudy London; the sun's invisible heat about twice the visible is Muller's ratio at the ground, after atmospheric absorption). Chapter XIV: Herschel's and Pouillet's measurement of solar heat (0.00728 inch of ice per minute; 25 per cent atmospheric absorption at the zenith; 40 per cent over the illuminated hemisphere), the sun as a coal block burns away in 5000 years, Mayer's meteoric theory (impact speeds 390 and 276 miles/s), Thomson's 8000-year gun-cotton reductio and 20-million-year 1862 view, Helmholtz contraction (17 million years), tidal heat, Bischof's 350-million-year cooling of the earth. Tyndall gives no age or temperature for the sun, and says of the meteoric theory 'I do not pledge myself to this theory'. The closing chapter ties energy to life (Mont Blanc climb, animal power) and the limits of science. Chapter XIV paragraphs 647-684 (deep read, QE): the meteorological evidence beyond Strachey is other people's: Wells's 1818 dew experiments (Surrey; wool bundles gaining 14 grains on a propped board against 4 beneath; a thermometer on grass 12 F colder than the air, falling to 2 F colder when clouds cross), Glaisher's table of relative chilling by height (long grass 1000, one foot 129, six feet 52), Pouillet's swansdown (chilling 7.1 C in April, 7.21 C in June), Melloni's 2 C limit and 'cold aerial bath', Melloni's lunar-heat deflection of 3-4 degrees. Tyndall's own part is interpretive: the 'dry-air supplement' to Wells on Bengal ice pits (para 655: from one remark of Sir Robert Barker, 'very little dew appears after midnight', and the wet-straw practice; no humidity measured), the mechanism that vapour must shed the heat of more than 100 times its mass of air, the attribution of Pouillet's 25 and 40 per cent solar absorption to aqueous vapour ('Doubtless'; solar, not terrestrial, absorption), and an unsuccessful conical-reflector attempt on lunar heat. None of the borrowed data carries a humidity measurement. Magnus on gaseous conduction (paras 291-295, PDF pp.250-254): Magnus held that hydrogen conducts heat 'like a metal' (platinum wire in a narrow hydrogen-filled tube; a heated vessel top with cotton wool or eider down); Tyndall replied that convection was not excluded and the question 'is still an open one'. Closing Note (p.533): Magnus had published a paper controverting Tyndall's views on aqueous vapour, 'by which I am not convinced'; no content, date or reply is given in the book. Tyndall also concedes (p.293) that 'all the merit of priority rests with Count Schaffgotsch' for singing flames [digest].

Key claims

• Dry air, oxygen, nitrogen and hydrogen are practically transparent to radiant heat from a 100 C source (about 1 degree on a 30-degree scale), while olefiant gas intercepts about 80 per cent (211 of 276 units) of the beam and ammonia is 'as black' as ink or pitch.
• At one atmosphere CO2 absorbs 90 times and olefiant gas 970 times as much radiant heat as air; at 1 inch pressure CO2 is 972, ammonia 5,460, olefiant gas 6,030 times air.
• Absorption by a gas is proportional to its amount only for small doses; strong absorbers saturate (olefiant gas: first inch 90, second inch 33, tenth inch 3).
• Radiation and absorption go hand in hand: CO 12/18, CO2 18/25, N2O 29/44, olefiant gas 53/61 (radiation swing/absorption) while air, O2, N2 and H2 show neither.
• Atmospheric aqueous vapour absorbs radiant heat 70-90 times as strongly as the air carrying it; at least 10 per cent of the earth's radiated heat is intercepted within ten feet of the surface; the vapour is a 'blanket' and 'dam' whose removal for one summer night would kill English plants capable of being killed by frost.
• Night cooling on clear nights is governed by the amount of invisible vapour (Strachey's 1850 series: tension 0.888 inch gives 6.0 degree fall, 0.435 inch gives 16.5 degrees), and dry regions (Sahara, Tibet, Australia, mountains) have large daily ranges.
• The objections to the vapour result (brine film, impurity, London soot, wall condensation, the tube) are answered by experiments in a plate-free open tube and in free air.
• The electric light's invisible radiation is about eight times its visible radiation; the iodine-bisulphide filter transmits 89 per cent of the arc's heat while quenching all light; the dark rays calorescence platinum.
• Heat is a mode of motion: Rumford's cannon-boring showed an inexhaustible heat source (so not a material substance) and Davy's friction-melting of ice was the first experiment proving the immateriality of heat (Tyndall's characterisation).
• The mechanical equivalent of heat is 772 ft-lb per lb of water per degree F (Joule); Mayer's method reconstructed with Tyndall's data gives 771.4, and the agreement 'relieves the mind of every shade of uncertainty' (the result is a difference of two nearly equal numbers and shifts by about 3 per cent with unrounded intermediates).
• Radiative power and absorptive power of a body are reciprocal; for obscure heat the radiation from a cube depends on the surface substance (gold, silver, copper low; varnish, earthenware, glass, lampblack, whiting, carmine, velvet high) and not on colour.
• Glacier ice shows regelation (fracture then refreezing at contacts) rather than viscosity under tension; ice behaves like a viscous body only where pressure acts.
• Ancient glaciers imply large vapour supply (hence strong solar action) plus effective condensation, not a weaker sun.
• The sun's heat cannot come from chemical combustion (burn-away in 5000-8000 years); gravitational/meteoric supply and Helmholtz contraction (17 million years of present emission from contraction to earth density) are offered; Tyndall hedges ('I do not pledge myself to this theory').
• Hydrogen-flame series (Heat paras 530-534, 4 ft polished tube): undried laboratory air absorbed 17.2 per cent of the radiation of a hydrogen flame (20.3 per cent on a later humid day), against 0 for dry air, but only 5.8 per cent of a platinum spiral glowing about as brightly as a wire plunged into the flame (8.6 per cent for the spiral inside the flame); humidity is not stated for any run.
• Liquid and vapour absorb in the same rank order when equal quantities of matter are compared (ten liquids, red-hot platinum spiral source, Heat paras 512-515); water vapour could not be examined unmixed with air, so its place is inferred from the liquid; the rank of vapours changes with the source (chloroform/iodide of methyl, formic/sulphuric ether).
• Breath CO2 by radiant-heat absorption agrees with Frankland's chemical analysis in three pairs: 4.311 chemical / 4.00 physical, 4.66 / 4.56, 5.33 / 5.22 per cent (Heat para 540-541; On Radiation prints only the last two); Tyndall calls the agreement 'very fair'.
• A layer of air 2 inches thick saturated with sulphuric ether vapour would let the sun's rays pass but 'cut off fully 35 per cent' of planetary radiation ('I find'; no table or source given), and a 1 inch layer of olefiant gas absorbs at least 26 per cent of obscure heat, so an atmosphere can keep a distant planet warm (Heat paras 545-546, argued against an unnamed work on the uninhabitability of the outer planets).
• Of the radiation of a white-hot platinum spiral 1 part in 24 is luminous, of a coal-gas flame 1 in 25, of the electric light 1 in 10 (later 11 per cent absorbed by iodine, so invisible 8 times visible) (Heat paras 583-587).
• Melloni's alum method is in error: concentrated alum transmitted 20 per cent of the obscure heat that had passed the iodine solution (Heat paras 641-643); Tyndall's footnote on Melloni's oil-flame 10/90, platinum 2/98, alcohol 1/99 shares calls the alum assumption 'an error'.
• One fifth of the obscure rays of the electric light reach the retina through the ox-eye vitreous humour, so nearly two-thirds of the radiant energy reaching the retina is incompetent to excite vision (Heat paras 643-644; single unpublished-in-detail measurement).
• Dynamic radiation and absorption: a gas or vapour heated by entering air radiates, chilled by pumping it absorbs, with no external source; eleven vapours show identical rank order of radiation (14-70) and absorption (6-43), ratio 0.40-0.61; in a 3 inch tube vapours keep 0.17-0.21 of their 33 inch radiation and olefiant gas keeps 0.62 (Heat paras 446-466).
• Ozone from electrolytic cells absorbs radiant heat 20 to 136 times the electrolytic oxygen carrying it, increasing as the electrodes shrink and when the cell is cooled; its amount is unmeasurable; Tyndall concludes ozone is oxygen atoms packed into oscillating groups (Heat paras 440-445).
• Pouillet: the atmosphere absorbs 25 per cent of the sun's heat at the zenith and 40 per cent over the illuminated hemisphere; Tyndall ascribes it chiefly to aqueous vapour ('Doubtless', his inference) (Heat para 684).
• Wells (1818) and Glaisher show chilling of grass and thermometers by radiation to a clear sky and its prevention by screens and clouds; Tyndall's own addition is that Bengal ice-making needs dry as well as clear air (Heat para 655, from one remark of Sir Robert Barker); none of these records contains a humidity measurement.
• Magnus held that hydrogen gas conducts heat like a metal; Tyndall replied that convection was not excluded and gaseous conduction 'is still an open' question (Heat paras 291-295); a later Magnus paper contesting Tyndall's vapour results is noted, unanswered, on p.533.

Relevance: The largest single source in the folder and the primary record of the gas-absorption and water-vapour experiments behind Tyndall's priority in showing that water vapour, CO2 and other polyatomic gases absorb terrestrial heat, with his own account of the objections and rebuttals. Also the standard statement of the 1860s dynamical theory and the Mayer/Joule/Rumford evidence. The deep reads record that several digest figures were OCR errors (see claims.md corrections).

Mainstream conflict: The tabulated gas contrast (N2, O2, H2 versus CO2, H2O, NH3, hydrocarbons) and the main role of water vapour in radiative cooling are consistent with modern infrared physics [memory, high]. Dated or non-modern elements: luminiferous ether; caloric language; 'rays of cold' dismissed correctly; the equivalent 771.4 uses a specific-heat ratio of 1.42 where the modern 1.40 gives about 797 (deep read arithmetic); gaseous conduction left open; the ethers-of-the-Sun theories; the claim that 'the first three gases never have been liquefied' was true in 1868 and is no longer. No apportionment of the vapour/CO2 effect is given; whether Tyndall's dry-air reference (1 degree assumed) fully excludes CO2 is an inference to check against the earlier drying apparatus.

A book of lectures given to American audiences (primary source, Tyndall's own words, for a general audience). Lectures I-IV and VI are standard optics of the period: rectilinear propagation, reflection, Snell's law, total reflection, velocity of light (Roemer, Bradley, Fizeau, Foucault), Descartes's rainbow, Newton's analysis and synthesis of white light and colours of bodies; the emission and wave theories (Young, Fresnel), interference, thin films, Newton's rings, diffraction, Huygens's principle; polarity, crystallisation, refraction and double refraction by the wave theory, polarization, Nicol prisms, colours in polarized light, strain and unannealed glass, circular polarization, Faraday's 'magnetization of light', and the blue of the sky, with the artificial-sky cloud experiment; spectrum analysis, Bunsen and Kirchhoff, solar chemistry and prominences. A closing address defends original research against purely applied work and has an Appendix (New York send-off speeches by Barnard, Draper and White; wavelength measurement; spectra of polarized light; water crystallization letter from Joseph Henry). Lecture V (deep-read) restates the radiant-heat work for the lecture hall: electric-beam burning, an ice lens that ignites black paper and gun-cotton (Scoresby precedent), the claim that heat is always the result of absorption (a red ribbon in green light is warmed by the light quenched), Newton's comet of 1680 estimate used to argue temperature depends on absorption rather than nearness, the combustion of a diamond in oxygen by a terrestrial source in a platinum hood (Faraday's 1814 Florence account quoted; Tyndall states the combustion 'had never been effected by radiant heat from a terrestrial source' before his), the iodine ray-filter, dark-focus combustion, calorescence, air at the dark focus 'as cold as ice', boiling water at the invisible focus, the hoar-frost melted by dark rays (inferred role in glacier-fed rivers), and the identity of light and radiant heat shown by reflection, total reflection, invisible images, polarization (crossed Nicols), mica, quartz, double refraction in Iceland spar, and magnetization of an obscure heat beam (Faraday's experiment adapted, with a compensating source). The identity is explicitly 'such as subsists between one colour and another', not complete. The section on the heat spectrum repeats the 7.7 (spectrum-area) and 8 (filter-subtraction) result for the electric light, for more than twelve series. Lecture IV also gives Faraday's magnetization of light with the biquartz demonstration and a statement that the magnet 'acts upon the ether contained within the heavy glass'.

Key claims

• Light and radiant heat are 'identical' in the sense that one colour is identical with another: they behave alike in plane and total reflection, refraction, double refraction in Iceland spar, polarization, depolarization by mica, circular polarization by quartz, and magnetization.
• A magnet excited in the path of a polarized obscure heat beam, with the light quenched by the iodine ray-filter, deflects the thermopile needle, 'exactly as in Faraday's experiment it opened a door for the light'.
• The invisible emission of the electric lamp is 7.7 times the visible by spectrum area and 8 times by filter subtraction; no two methods are more opposed 'and hardly any two results could better harmonize'.
• Heat is always a result of absorption; light quenched by a coloured ribbon appears as heat 'exactly equivalent' to the light extinguished (stated as fact, no measurement given).
• A lens of ice focuses the electric beam and ignites black paper and gun-cotton, showing that a beam can retain heating power after crossing a very cold substance.
• Newton's estimate of the comet's temperature (more than 2,000 times molten iron) cannot be inferred from nearness to the sun; low absorptive power could let the comet carry 'the temperature of stellar space'.
• A diamond in a platinum hood can be burnt in oxygen by the electric-beam focus, reproducing Faraday's solar-lens experiment of 27 March 1814 with a terrestrial source (Tyndall's priority claim).
• Dark ultra-red rays melt hoar-frost and boil water at the invisible focus, which Tyndall extends to the melting of glacier ice and the evaporation of the tropical ocean; no solar measurement is given.
• The blue of the sky is due to scattering by very small particles (an artificial sky was made from light-decomposed vapour), with polarization like the real sky.
• Faraday's magnetization of light is the rotation of the plane of vibration of light by a magnet acting on the ether in the heavy glass; Tyndall gives no numbers or equation.

Relevance: Shows the mature, public form of Tyndall's radiant-heat programme in 1872-73 (the identity of light and radiant heat, the 7.7/8 ratio, calorescence, the iodine filter) and the physical optics background (interference, polarization) used in the reader's learning. The Lecture on light scattering belongs to the colour-of-the-sky work that the folder otherwise lacks.

Mainstream conflict: The optics (reflection, refraction, polarization, interference, diffraction) is standard wave optics; the identification of light and radiant heat as electromagnetic waves of different wavelength was completed by Maxwell and Hertz [memory, high], whereas Tyndall's explanation is by ether vibration of molecular periods. Faraday rotation is now treated by the Verdet constant [memory, high]; Tyndall gives no equation. Newton's 1680 comet estimate is described by Tyndall himself as based on doubtful data.

A collection of Tyndall's occasional essays, lectures and addresses from about 1880 to 1891 (primary source, mostly not about physics). Essays covered: The Sabbath (1880, Glasgow Sunday Society address), Goethe's 'Farbenlehre' (1880), Atoms, Molecules, and Ether Waves (1882), Count Rumford (Royal Institution lecture), Louis Pasteur, His Life and Labours (1884 review of Radot), The Rainbow and its Congeners (1884), Address at the Birkbeck Institution (22 October 1884), Thomas Young (1886), Life in the Alps (1887), About Common Water (1889), Personal Recollections of Thomas Carlyle (1890) with the unveiling address (26 October 1882), On the Origin, Propagation, and Prevention of Phthisis (1891, reviewing Cornet) with the 1882 Times letter on Koch, and Old Alpine Jottings (1889 preface; Matterhorn narrative). Each essay is listed separately below. The advertisement on p.514 lists Tyndall's other books including Heat a Mode of Motion and the Lectures on Light.

Key claims

• New Fragments is a collection of essays; the physics bearing on the project is concentrated in 'Atoms, Molecules, and Ether Waves' (PDF pp.91-106), the Rumford essay (pp.107-186) and the Rainbow, Thomas Young and About Common Water essays.

Relevance: Source of Tyndall's own late summary of the absorption/resonance picture (1882) and of his judgement of Rumford, Goethe, Young and Pasteur; contains little on the central experiments and is peripheral for the main reviews except the 1882 essay.

Mainstream conflict: none for the collection as a whole (see individual essays).

Tyndall's popular account of atoms, molecules and the resonance explanation of absorption. Evidence for atoms: fixed proportions (water 1:8 by weight; 2 volumes hydrogen to 1 oxygen) and multiple proportions (hydrogen peroxide has exactly double the oxygen). A molecule is a group of atoms held by affinity; the atoms vibrate millions of millions of times a second, in the range of light and radiant-heat waves. Piano analogy (singing into an open piano): ether waves are absorbed by atoms whose periods match theirs, and because periodic impulses add, weak waves can do what strong ones fail to do. Experiments cited: nitrite of amyl vapour in a sunbeam produces a bright cloud (photolysis), while ultra-red waves of vastly greater energy do not decompose it; Savart's water jet in his Alpine kitchen, where a note near 130 vibrations a second shortened the continuous jet by half (Plateau drop instability). He states without proof that the atoms (not the whole molecule) are the seat of absorption, since decomposition occurs. Heat as explorer of molecular condition: since 1859 gases brought under experiment; hydrogen and nitrogen mixed 3:14 by weight are transparent, ammonia formed from them is 'like pitch or lampblack' to obscure heat although equally transparent to light (qualitative, no percentage). Hypothesis: combination makes atomic vibrations sluggish ('loaded piano strings'), elementary molecules may be out of tune with the ultra-red; he says 'a distinguished authority' (unnamed) entertained it. CO2 is one of the most transparent gases to a stove's radiation, yet the most opaque to a carbonic-oxide flame because emitter and absorber match. New quantitative material: 'the conservation of molecular action': a tube 38 inches long compared with the same number of molecules in a column 10.8 inches long (pressure x length equal; 1 inch of Hg long = 3.5 short, 2 = 7): lime-light, ether-type vapour 18.4 vs 18.8 per cent and 25.7 vs 25.6; platinum spiral 23.5 vs 23.4 and 32.1 vs 32.6 (which of ether or hydride of amyl each pair belongs to is not stated). 'Thermal continuity of liquids and vapours': ether vapour at 7.2 inches Hg (or hydride of amyl at 6.6) condensed to a 1 mm liquid layer: 66.7 per cent absorbed by the vapour against 67.2 by the liquid (platinum spiral); lime-light 33.3 per cent for the vapour, liquid figure garbled in OCR ('no difference whatever'). Water, one of the most opaque liquids to obscure heat, as vapour screens heat leaving the earth more than heat arriving from the sun: 'The elevation of our planet's temperature is therefore a direct consequence of the existence of aqueous vapour in our air.' The detailed data are said to be in the Philosophical Transactions. He notes he found no fact proving that free aqueous vapour is decomposed by solar rays (a polite non-confirmation of the sun-nourishing theory of an unnamed 'President of the British Association').

Key claims

• Atoms of a molecule absorb the ether waves whose periods match their own natural periods, as piano strings answer a sung note, and periodic impulses accumulate so that weak waves can decompose a molecule.
• Ultra-red waves, though more energetic, do not decompose nitrite of amyl vapour while visible light does, so a suitable relation between molecule and wave is needed.
• Absorption of radiant heat by a gas depends on the number of molecules, not on their density: the same number of molecules in a 10.8-inch column absorbs the same percentage (0.1 to 0.5 points difference) as in a 38-inch column ('conservation of molecular action').
• Absorption is unchanged by condensation: ether vapour absorbs 66.7 per cent and its equivalent 1 mm liquid layer 67.2 per cent ('thermal continuity of liquids and vapours').
• The earth's temperature is elevated by aqueous vapour because it hinders outgoing obscure heat more than incoming luminous heat.
• Elementary molecules (H-H, Cl-Cl) may be out of period with ultra-red waves, which could explain their neutrality (offered as a hypothesis).

Relevance: Tyndall's 1882 statement of the resonance picture and the first source in the folder for the density- and state-independence of molecular absorption; the numbers are single tabulated examples chosen by Tyndall as representative.

Mainstream conflict: Resonance picture and the dependence on molecular structure are consistent with modern molecular spectroscopy in outline [memory, high], with the caveat that modern accounts use dipole-changing vibrational modes and pressure/line broadening rather than ether and atom-by-atom periods; the density independence tested here is for a mixture of two broadband sources and has no spectral resolution.

Biography and evaluation of Benjamin Thompson, Count Rumford (born 26 March 1753, North Woburn, Massachusetts; loyalist in the American Revolution; Bavarian Minister of War and Police; Rumford soup, workhouse and English garden at Munich; knighted 1784; founder of the Royal Institution in 1799-1800; married Madame Lavoisier in 1805, separated 1809; died 21 August 1814 at Auteuil). Tyndall visited his birthplace in autumn 1872 guided by Dr. George Ellis, whose 1871 biography is the main source. Rumford's gunpowder and ballistic-pendulum work; his funding of the Rumford medal (1796 offer of 1,000l. stock to the Royal Society). Heat work as Tyndall presents it: convection in liquids (Rumford over-stated 'no conduction'), the maximum density of water (Tyndall rejects Rumford's providential reading), weighing heat, the 1803 Munich cooling experiments (glass bottle cools twice as fast as tin; black and white paint equal; goldbeater's-skin vessels black 23.5 min against white 28 min, which Tyndall says measures the Indian-ink coating and not colour), his 'frigorific rays' and Pictet's conjugate mirrors (Tyndall calls these untenable), priority with Leslie (credit 'equally to both'), calorimetry (1 lb charcoal heats about 8,000 lb of water 1 C; 1 lb hydrogen 34,000), photometer, coloured shadows, and the cannon-boring experiment (water 107 deg at 1 hour, 200 at 2 h 20 min, boiling at 2 h 30 min, i.e. Fahrenheit; 26.58 lb of ice-cold water brought to boiling; 2303.8 grains of wax; nine candles; inexhaustible heat so not a material substance). Tyndall adds that Boyle, Hooke and Locke had earlier taken heat to be motion and warns against treating Rumford as the first. Rumford's 1798 memoir is abstracted in Heat's Appendix to Ch. II.

Key claims

• Rumford's 1798 cannon-boring experiments showed an inexhaustible source of heat, which Tyndall takes to prove heat is motion and not a material substance.
• Rumford's black-versus-white goldbeater's-skin cooling result (23.5 vs 28 minutes) reflects the added ink coating and not colour; Rumford's own earlier paint test showed no difference.
• Rumford's 'frigorific rays' reading of Pictet's conjugate-mirror experiment is untenable; the thermometer falls because it radiates to the ice.
• Credit for radiant-heat experiments belongs equally to Rumford and Leslie, independently.

Relevance: Tyndall's account of the Rumford evidence on which the dynamical theory of heat is based; the numerical record is the same as Heat's Appendix to Chapter II.

Mainstream conflict: Rumford's conclusion (heat is motion) is consistent with modern thermodynamics [memory, high]; Tyndall's reading that the Rumford experiment proves heat is not a substance rather than that the friction work supplies the energy is the historical interpretation.

Tyndall's review/introduction for the English translation (Lady Claud Hamilton, Longman) of Valery Radot's life of Pasteur, his son-in-law. Contents: optical activity (Arago, Biot, Pasteur's separation of the right- and left-handed tartrates); Pasteur's claim that molecular dissymmetry belongs to life, which Tyndall doubts (quartz crystal rotates, dissolved quartz does not; Faraday converted more than 150 symmetric solutions to active ones; he quotes his own 1865 words on the 'mystery and miracle of vitality'); fermentation by living ferments (Penicillium selected the right-handed tartrate); Schwann's calcined-air flasks; Pouchet and Bastian on spontaneous generation; Tyndall's own qualification of Radot's boiling-kills-all-germs statement (hay-bacillus spores survived one to four hours of boiling and once eight hours, which would have made Bastian right on the death temperature); silkworm disease (June 1865, Alais 1869); Koch and anthrax (Tyndall received Koch's memoir from Cohn in 1876 and predicted his rise; he regrets Radot's disparaging references); the fowl-cholera and anthrax attenuated vaccines and the Melun trial (25 unvaccinated sheep: 21 dead, 4 dying; 25 vaccinated sheep in full health); rabies commission preliminary report relayed (23 vaccinated dogs, none attacked). He claims his own discontinuous heating (February 1877) rests on the spore/fugitive difference, and notes his offered 'exhausted soil' idea (c.1869) is superseded. The germ theory is described as meeting opposition like gravitation or evolution. Tyndall acts as friend and advocate of Pasteur here, and the rabies figures are a preliminary commission report as relayed.

Key claims

• Pasteur's anthrax-vaccination trial at Melun: 25 unvaccinated sheep, 21 dead and 4 dying; 25 vaccinated sheep 'in full health and gaiety'.
• Hay-bacillus spores can survive one to four hours of boiling, and in one case eight hours of continuous boiling failed to sterilise a desiccated-hay infusion.
• Pasteur's 'irrefragable barrier' between organic and inorganic dissymmetry is not permanent (Tyndall's disbelief, citing Jungfleisch, Faraday and quartz).
• The rabies parasite had not been isolated in 1884; 23 vaccinated dogs in the commission report were not attacked after inoculation.

Relevance: Peripheral to the radiant-heat programme; shows Tyndall's germ-theory advocacy and the sources for his own sterilisation claims.

Mainstream conflict: Germ theory and attenuated vaccines are now mainstream [memory, high]; the hay-spore heat-resistance observation is consistent with modern knowledge of bacterial spores [memory, high].

Tyndall examines the copy of Goethe's Farbenlehre given to him by Carlyle in May 1878 (a gift Goethe had sent Carlyle with a catalogue letter of 14 June 1830). He lists Goethe's parts (physiological colours, prismatic colours, chemical colours) and his 'geforderte Farben', relates the visiting-card and turbid-media experiments to Newton's theory, and judges that Goethe's facts are rich but his turbid-medium theory cannot explain the passage of yellow into red or the Newtonian spectrum. Tyndall quotes Newton's 1666 prism letter to Oldenburg and Goethe's invective against Newton ('petrified aperçu'), concedes Goethe's one valid hit (Newton's mistake on achromatism, corrected by Dollond), and says scattered light is blue and transmitted light complementary yellow, deducible from the undulatory theory (small particles scatter short waves more). He mentions artificial skies made from light-decomposed vapours. Conclusion: poetic and scientific approaches to nature should not exclude each other.

Key claims

• Goethe's turbid-media theory does not account for the Newtonian spectrum, but his experimental facts are rich.
• Light scattered by small particles is blue and the transmitted light complementary yellow, deducible from the wave theory.
• Newton's belief that refraction without colour is impossible was wrong (Dollond's achromatic lens).

Relevance: Contrast between Goethe's qualitative colour theory and the wave-theory explanation of scattering (also used in Six Lectures XI).

Mainstream conflict: Newton's spectrum and Rayleigh-type scattering are mainstream; Goethe's theory is the alternative Tyndall rejects [memory, high].

Historical and experimental account of the rainbow: Alhazan, Kepler's approximate refraction rule, Snell about 1621, Descartes's explanation (rays near 41 deg-42 deg leave a drop in a nearly parallel sheaf), Newton's colours, the maximum deviation 42 deg 28 min near 58-59 deg incidence (red 42 deg 30 min, violet 40 deg 30 min), supernumerary bows from wave interference (Young, Airy). White fog-bows (Ulloa at Pambamarca, radius 33 deg 30 min; Hind Head), Brocken spectres, Fo-Kuang on Emei-shan (Baber). Tyndall made artificial rainbows at the Royal Institution from a copper boiler (20 lb steam) and later from sprays of water, turpentine and paraffin, proposing 'physical spectrum analysis' of a mixed shower from the bows' sizes.

Key claims

• The primary bow's angle (about 41-42 deg) follows from a maximum in the deviation of rays inside a drop; red 42 deg 30 min, violet 40 deg 30 min.
• Supernumerary bows result from interference of rays equally deflected on either side of the maximum and require drops of nearly equal size.
• A mixed spray of two liquids would show a bow for each, so a composite shower can be analysed by its bows (Tyndall's prediction, tested with water plus paraffin or turpentine).

Relevance: Optics and scattering background for the reader; peripheral to the heat experiments.

Mainstream conflict: none; mainstream geometric and wave optics [memory, high].

Tyndall's last lecture at the Royal Institution on Young (born 13 June 1773 at Milverton, died 10 May 1829): languages, medical studies, the theory of accommodation of the eye (curvature of the lens, with the dispute with John Hunter, Home and Ramsden), the Royal Institution professorship (3 August 1801), the wave theory and the principle of interference (Royal Society 16 January 1800), the explanation of Newton's rings and diffraction, Brougham's Edinburgh Review attacks that kept Young's optics from view for thirteen years until Fresnel, transverse vibrations and the semi-solid ether, the Young-Helmholtz three-colour theory, heat as vibration, the use of the term energy (mv squared), and hieroglyphics (Rosetta stone, Champollion priority dispute with Peacock's account). Footnote notes the Young-Fresnel priority ('Arago realises Young had anticipated Fresnel by thirteen years').

Key claims

• Young anticipated Fresnel's interference work by thirteen years and proposed transverse vibrations of light.
• Young's accommodation theory (change of curvature of the crystalline lens) is 'completely verified' though the muscular mechanism is still moot.
• Brougham's Edinburgh Review attacks kept Young's optical work out of public view until Fresnel's rediscovery.

Relevance: Historical background for the wave theory of light and its reception; shows how a correct but unpopular theory was suppressed by one hostile reviewer.

Mainstream conflict: none; Young's wave theory is mainstream [memory, high].

Tyndall's memoir of Carlyle: the Rectorial address in Edinburgh (March-April 1866, with Huxley), Mrs. Carlyle's death on 21 April 1866, the winter trip to Mentone (22 December 1866), conversations on Goethe, homeopathy, Darwin, the 'Eyre' question, Irish repeal and race. Tyndall shows Carlyle his moteless (dust-free) chambers, explaining germs, and claims dust-free air left infusions unputrefied. Contains passages about scientific metaphor in Carlyle and 'dynamic, not didactic'. Carlyle died 5 February 1881. Reports Carlyle's views on the 'Negro question' and race. Not relevant to the heat experiments.

Key claims

• In the early 1870s Tyndall's dust-free (moteless) air left meat, fish, fowl and vegetable infusions unputrefied, which he took to show that organisms need germs from outside.
• Carlyle's 1831 passage about the smithy-fire 'kindled at the sun' anticipates energy conservation (Tyndall's reading).

Relevance: Biographical context only; includes the germ-theory demonstration to Carlyle.

Mainstream conflict: none for the physics; opinions on race are Tyndall's and Carlyle's period views and are reported, not endorsed.

Tyndall's review of Cornet's work on tuberculosis: tubercle bacilli in the dust of rooms of consumptives (virulent in 15 of 21 private sick-rooms), the danger of dried sputum rubbed to dust, rejection of heredity as the cause, cleanliness and spittoons as prevention, and the high tuberculosis mortality of nursing orders (1,320 of 2,099 deaths in 25 years in 38 hospitals). The 1882 Times letter summarises Koch's discovery of the tubercle bacillus, guinea-pig inoculation (four of six infected), growth between 86 and 104 F, and virulence of dried sputum after eight weeks. Note (October 1891) cites Tappeiner's self-exposure experiment.

Key claims

• Dust from the rooms of consumptives contains virulent tubercle bacilli (15 of 21 private sick-rooms), and dried sputum can stay virulent for weeks.
• Heredity or constitutional predisposition is not the cause of phthisis (Cornet and Koch; Tyndall agrees).

Relevance: Peripheral; evidence of Tyndall's later public-health writing.

Mainstream conflict: Bacterial cause of tuberculosis is mainstream [memory, high].

Autobiographical address: school-leaving 1839, Ordnance Survey and railway surveys (1840s), Queenwood College (1847) with Frankland, study at Marburg under Bunsen and Stegmann (autumn 1848; dissertation on a screw surface; first physical research on the sound of a water jet), Berlin 1851, Helmholtz's conservation of energy translated, Humboldt interview, Hirst, closing on duty. Gives the origin of his training in mathematics and experimental physics.

Key claims

• Tyndall worked as an Ordnance Survey draughtsman, railway surveyor and teacher (Queenwood, 1847) before studying at Marburg under Bunsen and Stegmann from autumn 1848 (autobiographical statement).

Relevance: Biography of the inventor/scientist: education and career.

Mainstream conflict: none.

Tyndall argues for opening museums and gardens on Sundays against Sabbatarian rigour, with a historical account of Sabbath law (Exodus versus Deuteronomy reasons, Puritan judgements, Westminster Confession, witch persecutions) and an appeal to experience. Not about physics.

Key claims

• Sunday closing of public museums is not justified by the original or later Christian authorities (Tyndall's argument).

Relevance: No scientific content.

Mainstream conflict: none.

Life in the Alps: Tyndall's Bel Alp chalet in the commune of Naters, Valais; snow loads, avalanches, a guide killed, an avalanche descent with a watch lost and found three weeks later, the Jungfrau accident, the creep of boulders on the slope, the mechanism of glaciers (friction at the sides and bed, moulins, ice tables, medial moraines, crevasses). About Common Water: water as the basis of life, springs and hard/soft water (chalk versus greensand; his 225 ft well), boiling and scale (bicarbonate to carbonate), cave stalactites, carbonic acid in breath turning lime-water milky, Clark's softening process (9 oz lime precipitates 32 oz chalk), blue colour of water and ice, water's low compressibility, expansion on freezing, frost shattering rock, ice melted internally by a sun-lens ('six-petalled liquid flowers'). Gives a popular treatment of the water cycle consistent with Heat Ch. VI.

Key claims

• Boiling hard water precipitates carbonate (kettle scale) because the soluble bicarbonate loses carbonic acid; adding lime-water removes it (Clark's process, 9 oz lime precipitates 32 oz chalk).
• A glacier moves fastest at the centre and surface because of friction at sides and bed.

Relevance: Popular background on water and glacier phenomena that complement Heat Chapters V-VI.

Mainstream conflict: none.

Climbing narratives and glaciological observations: the Matterhorn attempts of 1860, 1862 (with Bennen; halted at the final precipice) and 1868 (traverse with Joseph Maquignaz), glacier stake measurements with Hirst (Morteratsch, 100 hours: 56, 47, 30 inches at three positions), rejection of the earthquake origin of Alpine gorges (sawn by water), ice-cones and cloud formation by adiabatic cooling, the Finsteraarschlucht, meltwater collection. Ends with a poem on the unknowable ('We yearn, and grope, and guess, but cannot know'). In summer 1866 Tyndall climbed the Titlis (guide Maurer of Meyringen, base at Engstlen) and 'repeated with a hand spectroscope the observations of M. Janssen on the absorption-bands of aqueous vapour' (p.472); no result, wavelengths, sky condition or inference is given.

Key claims

• Alpine gorges (Via Mala, Finsteraarschlucht, etc.) were cut by running water rather than earthquakes.
• Glacier surface velocity measured by stakes at Morteratsch: 56, 47, 30 inches in 100 hours (highest, middle, lowest row).
• In summer 1866, on the summit of the Titlis, Tyndall repeated with a hand spectroscope Janssen's observations of the absorption bands of aqueous vapour; the book reports the attempt only, with no result.

Relevance: Field glaciology and mountaineering; background to Tyndall's glacier work. The Titlis sentence is a bare mention of spectroscopic evidence for atmospheric vapour absorption (Janssen); it is not data from Tyndall.

Mainstream conflict: none; erosion by water and ice is the mainstream view [memory, high].