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Richmann, Georg Wilhelm

RICHMANN, GEORG WILHELM

(b. Pernau, Estonia [now Pärnu, U.S.S.R.], 11 July 17I1; d. St. Petersburg, Russia [now Leningrad, U.S.S.R.], 26 July 1753)

physics.

Richmann was the posthumous son of Wilhelm Richmann, a German in the Swedish administration at Dorpat (Tartu), who had fled to Pernau to avoid the advancing armies of Peter the Great. Pernau itself fell to the Russians just before Richmann’s birth; he consequently spent his youth, as he did his entire professional career, in the Russian empire. He received his early education in Reval (Tallinn), doubtless in one of the schools operated by the large German colony there. He subsequently attended the universities of Halle and, especially, Jena. There he studied mathematics and physics under G. E. Hamberger (1697–1755), who conceived of physics in the manner of Descartes and encouraged the search for what he called “natural laws,” phenomenological relations between measurable physical quantities. Richmann firmly adopted this program, to which he had to recall Hamberger, who once negligently admitted special innate forces as the cause of cohesion.

About 1735 Richmann went to St. Petersburg as tutor to the sons of the powerful foreign minister A. I. Osterman. Richmann continued his own studies at the University staffed by members of the St. Petersburg Academy of Sciences. He worked primarily under G. W. Krafft (1701–1754), a facile mathematician much abler than Hamberger and no less interested in applying his art to quantifiable physical problems. In 1739—having enjoyed the unusual distinction of attending the Academy’s meetings while yet a student (“because of his remarkable erudition and other good qualities”)—Richmann entered it as an adjunct; two years later he was named extraordinary professor of physics; and in 1745 he succeeded Krafft, who had returned to Germany, as ordinary professor and director of the physical laboratory.

Richmann’s first significant work concerned the determination of the temperature T produced by mixing a quantity of water m1, at temperature T1; with a quantity m2; at temperature T2;. The problem, an old chestnut in medical literature, had earlier engaged Krafft, who concluded by experiment that

T = (11m1T1 + 8m2T2)/(11m1 + 8m2), T1 > T2.

This result disagreed with some measurements of Richmann’s and, more importantly, with his excellent physical intuition, which assured him that Fahrenheit’s thermometer was approximately linear and that (to use an anachronism) the specific heat of water was scarcely altered with temperature.1 The problem then became, as many medical writers had glibly assumed, a simple case of averaging; and one should expect

T = (m1T1 + m2T2)/(m1 + m2).

Very careful measurements,2 taking into account what we would call the water equivalent of the thermometer and container, confirmed Richmann’s equation and revealed the cause of Krafft’s error. “The whole business,” he said, “shows clearly that physics should avoid mathematical abstractions with all diligence and whenever possible, and attend to every circumstance in individual cases.”3 This by no means meant defection from Hamberger’s goals. Richmann explicitly made it his “business” to establish the quantitative phenomenologieal laws that form the basis of sound physics;4 “only if we have accurately determined the properties of bodies can we legitimately infer other truths with certainty.”5

Heat phenomena lent themselves preeminently to this program. Richmann painstakingly investigated how a body’s rate of heating, of cooling, and (in the case of water) of evaporation, depended upon its nature and upon the difference between its temperature and that of the surrounding air. He succeeded in confirming Newton’s law of cooling6 and in demonstrating—independently of Nollet and in contradiction to most physicists—that the rate of gain or loss of heat bears no evident relation to density, elasticity, or hardness.7 The former result seemed to him so secure that he later proposed using it and his own law of evaporation to define (and, suitably implemented, to measure) the time average of the ambient temperature;8 as for the latter, it was just another “proof that in physics nothing can be established securely without experiments.”9

Throughout these experiments Richmann assumed that heat was “a certain motion of certain corporeal particles,” and could no more be known “absolutely” than could motion itself. Since, on this theory, the “cohesion of substances”—including the mercury in Fahrenheit’s instruments—could be expected to decrease with increasing temperature, it eventually caused Richmann to question the linearity of the thermometer and to undermine the assumptions on which most of his work had been based.10

Although Richmann flirted with many subjects besides heat (for example, artificial magnets and several types of balance barometers),11 the only other study that claimed his continuous attention was electricity, which he took up early in 1745. He commenced with the experiments of S. Gray, Dufay, C. A. Hausen, and G. M. Bose, which he found in Doppelmayr’s admirable Neu-entdeckte Phaenomena (1744). Naturally Richmann quickly felt the need for a measuring instrument. He first took as a measure of electrical force the weight required to bring into equilibrium a balance one pan of which hung above the electrified object. But the device proved unsatisfactory, and he changed to the angle formed between a vertical rule attached to the electrified body and a thread suspended from the top of the rule. With this “index,” as he called it, he found that the “capacity” of an insulated conductor (corpus derivativae electricitatis finitae connexionis) depended not only on its total mass but also upon its shape.12 These experiments, which date from 1745, are perhaps the earliest of their kind. Richmann then examined the relative conductivity of silk rubbers of various colors and measured, as one might expect, the rate of leak of electricity from insulated conductors as a function of humidity. Such problems occupied him until 1752, when he learned of the lightning experiments at Marly and acquired a copy of Franklin’s Experiments and Observations on Electricity.

Richmann repeated the experiments, pointing out exaggerations and errors which the Philadelphians would not have made, he said, had they bothered to construct a decent electrometer, for example, by utilizing the principle of the otherwise frivolous “electrical jack.”13 For his part he preferred his index, which he took to measure the “agitation” of “a certain electrical matter which surrounds electrified bodies to a certain distance.”14 He could not bring himself to accept negative electricity (“unless it is agreed that, as in mechanics, motion made in a contrary direction is negative”)15 or the impenetrability of glass, against which he designed an interesting experiment,16 which Aepinus later showed to be in perfect, even in quantitative, agreement with Franklin’s principles. But Richmann enthusiastically embraced the new doctrine about lightning and installed in his home an insulated rod with which to probe the agitated electrical matter of thunder clouds. He was more aware than Franklin of the risks involved. Fear of lightning, he wrote, is quite natural and will only be overcome when one understands how and why its stroke can be averted. That, of course, will require many observations and experiments. “Evidently in these times even the physicist has an opportunity to display his fortitude.”17 Richmann and his friend and colleague Lomonosov let no storm go by without carefully following its effects on the indicators attached to their insulated poles. On 26 July 1753 it thundered in St. Petersburg. Richmann ran home from the Academy and bent to read his index. At that instant lightning hit the pole and struck him dead, a martyr to his mania for measurement.

NOTES

1. Richmann, “De quantitate caloris…,” in Novi commentarii, 1 (1747–1748), 152–154.

2. “Formulae pro gradu excessus…,” Ibid., 168–173.

3. “De quantitate caloris…,” Ibid., 166.

4. “De indice electricitatis…,” Ibid., 4 (1752–1753), 301.

5. “Inquisitio in decrementa et incrementa…,” Ibid., 241–242.

6. “Inquisitio in legem…,” Ibid., 1 (1747–1748), 174–197.

7. “De argento vivo…,” Ibid., 3 (1750–1751), 309–339; and “Inquisitio in decrementa et incrementa…,” Ibid., 4 (1752–1753), 241–270.

8. “Usus legis decrementi…,” Ibid., 2 (1749), 172–178.

9. “De argento vivo…,” Ibid., 3 (1750–1751), 309.

10. “Tentamen rationem calorum …,” Ibid., 4 (1752–1753), 277–300.

11. “De barometro…,” Ibid., 2 (1749), 181–209.

12. “De electricitate…,” in Commentarii, 14 (1744–1746), 299–324.

13. “De indice electricitatis…,” in Novi commentarii, 4 (1752–1753), 301–302, 323.

14.Ibid., 305.

15.Ibid., 323–324.

16.Ibid., 324–325.

17.Ibid., 335.

BIBLIOGRAPHY

I. Original Works. Richmann’s published work consists of 22 Latin memoirs, of which Poggendorff gives a full list, in the Commentarii and Novi commentarii academiae scientiarum imperialis petropolitanae. The most important memoirs are “De electricitate in corporibus producenda nova tentamina,” in Commentarii, 14 (1744–1746), 299–324; “De quantitate caloris, quae post miscelam fluidorum certo gradu calidorum, oriri debet, cogitationes,” in Novi commentarii, 1 (1747–1748), 152–167; “Formulae pro gradu excessus caloris supra gradum caloris mixti ex nive et sale ammoniaco, post miscelam duarum massarum aquarum, diverso gradu calidarum, confirmatio per experimenta,” Ibid., 168–173; and “De indice electricitatis et ejus usu in definiendis artificialis et naturalis electricitatis phaenomenis, dissertatio,” Ibid., 4 (1752–1753), 301–340.

Also of interest are “Inquisitio in legem, secundum quam calor fluidi in vase contenti, certo temporis intervallo, in temperie aëris constanter eadem decrescit vel crescit…,” Ibid., 1 (1747–1748), 174–197; “Tentamen, legem evaporationis aquae calidae in aëre frigidiori constantis temperiei definiendi,” Ibid., 198–205; “Usus legis decrementi caloris ad definiendam mediam certo temporis intervallo temperiem aëris ostentus…,” Ibid., 2 (1749), 172–178; “De barometro cuius scala variationis insigniter augeri potest…,” Ibid., 181–209; “De argento vivo calorem celerius recipiente et celerius perdente, quam multa fluida leviora experimenta et cogitationes,” ibid. 3 (1750–1751), 309–339; “Inquisitio in decrementa at incrementa caloris solidorum in aëre,” Ibid., 4 (1752–1753), 241–270; and “Tentamen rationem calorum respectivorum lentibus et thermometris definiendi,” Ibid., 277–300.

Many of Richmann’s scientific MSS and some correspondence, preserved in the Archives of the Russian Academy of Sciences, have been published in G, W. Richmann. Trudy po fizike, A. A. Eliseev, V. P. Zubov, A. M. Murzin, eds. (Moscow, 1956).

II. Secondary Literature. Most Western sources, for example, Jöcher; Poggendorff; J. G. Meusel, in Lexikon, 11 (1811), 261–263; J. F. von Riecke and K. E. Napiersky, in Allgemeines Schriftsstellerslexikon, 3 (1831), 531–534; and L. Stieda, in Allgemeine deutsche Biographie, 28 (1899), 442–444, all copy one another and, ultimately, Novi commentarii, 4 (1753), 36. A valuable exception is F. C, Gadebusch, Livländische Bibliothek, 3 (1777), 22–29. Russian sources are much fuller: Russkii biograficheskii slovar’, 16 (1913), 233–240; and P. Pekarskii, Istoriia imperatorskoi akademii nauk v Peterburge, 1 (St. Petersburg, 1870), 697–717. See also Protokoly zasdanii konferentsii imperatorskoi akademii nauk s 1725 po 1803 goda = Procès-verbaux des séances de I’académie impériale des sciences depuis sa fondation jusqu’à 1803, I-II (St. Petersburg, 1897); Materialy dlya istorii imperatorskoi akademii nauk (1716–1750), II-X (St. Petersburg. 1885–1900); and L. Euler, Perepiska. Annotirovannyi ukazatel, A. P. Youschkevitch, and V. I. Smirnov, eds. (Leningrad, 1967). A good portrait appears in Materialy, 4 , opposite p. 370.

A general account of Richmann’s work is V. P. Zubov, “Die Begegnung der deutschen und der russischen Naturwissenschaft im 18. Jahrhundert und Euler,” in Die deutsch-riissisc/ie Begegnung und Leonhard Euler (Berlin, 1958), 19–48. On calorimetry, see D. McKie and N. H. de V. Heathcote, The Discovery of Specific and Latent Heats (London. 1935), 59–76; and V. P. Zubov, “La formule calorimétrique et ses origines,” in Mélanges Alexandre Koyré, 1 (Paris, 1964), 654–661, and “Kalorimetricheskaya formula Rikhmana i ee predistorya,” in Trudy instituta istorii estestvoznaniia i tekhniki, 5 (1955), 69–93. On the barometer, see W. E. Knowles Middleton, The History of the Barometer (Baltimore, 1964), 107, 376. On electricity, see B. S. Sotin, “Raboty G. V. Rikhmana po elektrichestvu.” in Trudy Instituta istorii estestroznetniia i tekhniki. 44 (1962), 3–42; A. G. Dorlman and M. I. Radovskii, “B. franklin i russkie elektriki XVIII v.,” Ibid., 19 (1957), 290–312; and B. G. Kuznetzov, “Razvitie ucheniia ob elektrichestve v russkoi nauke XVIII v.,” Ibid., 313–385.

On Richmann’s death, see “An Account of the Death of Mr. George Richmann,” in Philosophical Transactions of the Royal Society, 44 (1755), 61–69; B. N. Menshutkin, Russia’s Lomonosov (Princeton, 1952), 86–89; and D, Miiller-Hillebrand. “Torbern Bergman as a Lightning Scientist,” in Daedalus. Tekniska museets årsbok (1963), 35–76.

John L. Heilbron

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