‘Enquiries on Plaister of Paris’: a material history of early agrochemical knowledge in the United States of America, 1785–1812

ABSTRACT

Key figures in the founding years of the United States of America were part of the first American learned agricultural society, known as the Philadelphia Society for Promoting Agriculture (PSPA). Its members were georgic farmers who set out to describe, explore and explain agricultural processes by practical experiences, observations, and theories written in British books. Those theories, however, did not provide any reason for the widespread agricultural practice in Pennsylvania of using plaster as fertilizer, which was German in origin. Although imports were heavily tariffed and later even banned, plaster became, and remained, a top commodity in America. In order to keep agricultural businesses and investments afloat, several members of the PSPA began to scientifically justify the application of plaster fertilization. In so doing, they incorporated chemical theories and methods to both their agricultural practices and investigations. Thus, I argue, they acquired and developed an agrochemical knowledge that was mainly determined by a material history of plaster. Their knowledge was new, unique and more practicable in comparison to the British knowledge in this sector. Eventually, it was through the newly developed knowledge by PSPA members that contributed to the formation of agricultural chemistry as a science in its own respect.

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ORCID

Christopher Halm http://orcid.org/0000-0002-4501-8664

Notes

1 The term georgic farming is used according to Benjamin R. Cohen (2009) – Benjamin R. Cohen, Notes from the Ground. Science, Soil, and Society in the American Countryside, Yale Agrarian Studies Series, ed. by J. C. Scott (New Haven, CT: Yale University Press, 2009).

2 Ibid., pp. 3–5, 9, 11 and further.

3 Ibid., pp. 20, 37–41, 47 and 76. Ierome Bernhard Cohen, Science and the Founding Fathers. Science in the Political Thought of Jefferson, Franklin, Adams, and Madison (New York, NY: W. W. Norton, 1995), p. 66.

4 About Peters: Cohen, Notes from the Ground, pp. 39, 43, 97, 117–19.

5 Liebig’s main work on agricultural chemistry came out in 1840, Davy’s in 1813. Humphry Davy, Elements of Agricultural Chemistry. In a Course of Lectures for the Board of Agriculture (London: W. Bulmer, 1813). Justus Liebig, Die organische Chemie in ihrer Anwendung auf Agricultur und Physiologie (Braunschweig, Vieweg und Sohn, 1840). On the history of agricultural chemistry after those two, see: Margaret W. Rossiter, The Emergence of Agricultural Science. Justus Liebig and the Americans (1840–1880), Yale Studies in the History of Science and Medicine 9 (New Haven, CT: Yale University Press, 1975). Ursula Schling-Brodersen, Entwicklung und Institutionalisierung der Agrikulturchemie im 19. Jahrhundert. Liebig und die landwirtschaftlichen Versuchsstationen, Braunschweiger Veröffentlichungen zur Geschichte der Pharmazie und der Naturwissenschaften 31 (Braunschweig: Pharmazeutisches Seminar der Technischen Universität/Deutscher Apothekerverlag, 1989). E. Patrick Munday, ‘Sturm und Dung: Justus von Liebig and the Chemistry of Agriculture’ (dissertation, Ithaca, NY, 1990). Frank A. J. L. James, ‘“Agricultural Chymistry Is at Present in It’s Infancy”: The Board of Agriculture, The Royal Institution and Humphry Davy’, Ambix, 62, no. 4 (2015), 363–85.

6 For example: Charles Albert Browne, A Source Book of Agricultural Chemistry, Chronica Botanica 8, ed. by F. Verdoorn (Waltham, MA: Chronica Botanica, 1944). Archibald Clow and Nan L. Clow, The Chemical Revolution. A Contribution to Social Technology (Freeport (NY), Books for Libraries Press, ²1970). François Dagognet, Des révolutions vertes: Histoire et principes de l’agronomie (Paris, Hermann, 1973). George E. Fussell, Crop Nutrition. Science and Practice Before Liebig, Coronado Publications in History of Science, ed. by H. Lewis McKinney and Jerry Stannard (Lawrence, KS: Coronado Press, 1971). Charles W. J. Withers, ‘William Cullen’s Agricultural Lectures and Writings and the Development of Agricultural Science in Eighteenth-Century Scotland’, Agricultural History Review, 37 (1989), 144–56.

7 At this point I refer to my own doctoral project ‘Die Frühgeschichte der Agrikulturchemie (1730–1813). Wie der Ackerboden zu einem laborähnlichen Raum wurde’ [The Early History of Agricultural Chemistry. How Soils Became Laboratory-like Spaces, 1730–1813], which will be soon to be completed.

8 Lissa L. Roberts and Simon Werrett, Compound Histories. Materials, Governance and Production (1760–1840), Cultural Dynamics of Science 2, ed. by Lissa Roberts, Agustí Nieto-Galan, and Oliver Hochadel (Leiden: Brill, 2018). Materials and Expertise in Early Modern Europe. Between Market and Laboratory, ed. by Ursula Klein and Emma C. Spary (Chicago, IL: UCP, 2010).

9 Roberts and Werrett, Compound Histories. Klein and Spary, Materials and Expertise in Early Modern Europe.

10 Id.: ‘Introduction: Why Materials?’, in ibid., pp. 1–23, here p. 10.

11 Lissa L. Roberts and Simon Werrett, ‘Introduction. “A More Intimate Acquaintance”’, in Compound Histories. Materials, Governance and Production (1760–1840), ed. by Lissa L. Roberts and Simon Werrett, Cultural Dynamics of Science 2, hrsg. von Lissa Roberts, Agustí Nieto-Galan, and Oliver Hochadel (Leiden: Brill, 2018), pp. 1–32.

12 Johann Georg Krünitz (1773–1858): Gyps, in: Oekonomische Encyklopädie. Oder allgemeines System der Staats- Haus- und Landwirthschaft, vol. 20, pp. 413–76, Oeconomische Encyclopädie online, <http://www.kruenitz1.uni-trier.de> [accessed 14 December 2017].

13 Johann Friedrich Mayer (1768): Lehre vom Gyps, Als vorzueglich guten Dung zu allen Erd-Gewaechsen auf Aeckern und Wiesen, Hopfen- und Weinbergen (Anspach: Jacon Christoph Posch).

14 Joshua M. Smith, Borderland Smuggling. Patriots, Loyalists, and Illicit Trade in the Northeast, 1783–1820 (Gainesville, FL: University Press Florida, 2006), p. 41.

15 Richard Peters, ‘On Gypsum’, in: Memoirs of the Philadelphia Society for Promoting Agriculture. Containing Communications on Various Subjects in Husbandry & Rural Affairs, ed. by Richard Peters and James Mease (1808). To which is added, a statistical Account of the Schuylkill Permanent Bridge, vol. I (Philadelphia, PA: Jane Aitken), pp. 156–75, here: pp. 161–62. Id. (1811): The Efficacy of Sulphur on vegetation, in: Peters and Mease, Memoirs of the Philadelphia Society for Promoting Agriculture. To which is added at the Request of the Society ‘Agricultural Inquiries on Plaister of Paris’, vol. II (Philadelphia, PA: Johnson and Warner), pp. 206–10, here: p. 207. John Taylor, ‘On Gypsum’, in PSPA Memoirs II (1811), pp. 51–62 and 75–78, here: pp. 51–52.

16 Peters, ‘On Gypsum’, PSPA Memoirs I (1808), pp. 158–59. Id.: ‘Gypsum; whether it is found in the United States’, in: PSPA Memoirs I (1808), pp. 310–16, here: p. 311.

17 Id., ‘On Gypsum’, PSPA Memoirs I (1808), pp. 159–60.

18 On the Effects of Gypsum, or Plaster of Paris, as a Manure. Chiefly Extracted from Papers and Letters on Agriculture, ed. by The Agricultural Society of Canada (London: James Phillips, 1791), pp. 4–5.

19 Rossiter, The Emergence of Agricultural Science, pp. 3–9.

20 Simon Baatz, “Venerate the Plough”. A History of the Philadelphia Society for Promoting Agriculture 1785–1985 (Philadelphia, PA: Philadelphia Society for Promoting Agriculture, 1985), p. 12.

21 Cohen, Notes from the Ground, p. 54

22 The Agricultural Society of Canada, On the Effects of Gypsum, pp. 3, 5, 17.

23 John Spurrier, The Practical Farmer. Being a New and Compendious System of Husbandry, Adapted to the Different Soils and Climates of America. Containing the Mechanical, Chemical and Philosophical Elements of Agriculture. With Many other Useful and Interesting Subjects (Wilmington: Brynberg and Andrews, 1793). Thomas Jefferson, ‘From Thomas Jefferson to John Spurrier, 18 June 1793’, in Founders Online – National Archives (Original source, ed. by John Catanzariti: The Papers of Thomas Jefferson, vol. 26 (Princeton, NJ: Princeton University Press, 1793), S. 318 <https://founders.archives.gov/documents/Jefferson/01-26-02-0289> [accessed 29 September 2019]. Cohen, Notes from the Ground, pp. 17–23, 26–34, 39–41.

24 George Winter, A New and Compendious System of Husbandry. Containing the Mechanical, Chemical, and Philosophical Elements of Agriculture (Bristol: W. Routh, 1787), title page.

25 See the second edition of the same book: George Winter, A New and Compendious System of Husbandry. Containing the Mechanical, Chemical, and Philosophical Elements of Agriculture. To which is added [four further essays] (London: Mrs. E. Newberry, ²1797), title page and VIf. As an example to his writings in the journals of different learned societies: Id., 1787, title page.

26 Winter stood up to Young’s accusations in a pamphlet he wrote under the pseudonym Benjamin Bramble – Bramble, Benjamin [= Winter, George], The Farmer Convinced. Or, the Reviewers of the Monthly Reviewed anatomized. Their Ignorance Exposed. And Their Vague, Futile, and Fallacious Assertions Refuted. Also W-----’s New and Comendious System of Husbandry Dissected. With Remarks on his patent Dirll Machine (London: Timothy Type, 1788).

27 John Lang, ‘On Liming Land’, in PSPA Memoirs II (1811), pp. 299–304, here: p. 304.

28 The Agricultural Society of Canada, On the Effects of Gypsum, pp. 4, 9–10, 17.

29 William Cullen, ‘The Substance of Nine Lectures, on Vegetation and Agriculture, Delivered to a Private Audience in the Year 1768, with a Few Notes by George Pearson’, in Additional Appendix to the Outlines of the Fifteenth Chapter on the Proposed General Report from the Board of Agriculture. On the Subject of Manures (London: W. Bulmer, 1796), No. II, pp. 1–41, here: pp. 5–7, 27–32, 36, 39–40.

30 On the British island, next to Cullen his colleague Home and his former student George Fordyce (1736–1802). In Sweden: Wallerius and Pehr Adrian Gadd (1727–1797). In the German countries: Johann Adam Külbel (1686–1754) and Johann Theodor Eller (1689–1760). In France to some extent Pierre-Joseph Macquer (1718–1784) and Antoine Baumé (1728–1804). Concerning both the conception of agricultural chemistry in Sweden and the mucilage/fat-nutrition-theory, see: Christopher Halm, ‘Eine frühe Konzeption der Agrikulturchemie. Johan Gottschalk Wallerius’ “Agriculturæ Fundamenta Chemica”’ (1761), in Mitteilungen, Gesellschaft Deutscher Chemiker / Fachgruppe Geschichte der Chemie 25 (2017), pp. 57–73.

31 Fame and Fortune. Sir John Hill and London Life in the 1750s, ed. by Clare Brant and George Sebastian Rousseau (London: Palgrave Macmillan, 2018). George Sebastian Rousseau, The Notorious Sir John Hill. The Man Destroyed by Ambition in the Era of Celebrity (Bethlehem, PA: Lehigh University Press, 2012). Jacques Voisine, ‘Henry Pattullo’s Contribution to the French Enlightenment’, Canadian Review of Comparative Literature/Revue Canadienne de Littérature Comparée, 1, no. 2 (1974), pp. 97–103.

32 For example: Thomas Hale’s popular “Compleat Body of Husbandry, Vol. I” (²1758) and Arthur Young’s “General View of the Agriculture of […] Essex, Vol. II” (1807) do not discuss chemical principles. The latter was in the possession of the PSPA.

33 This is pointed out very impressively by Peters himself: Richard Peters, Agricultural Enquiries on Plaister of Paris. Also, Facts, Observations and Conjectures on that Substance when applied as a Manure (Philadelphia, PA: Charles Cist; John Markland, 1797), pp. 82–83. See also Lucius F. Ellsworth, ‘The Philadelphia Society for the Promotion of Agriculture and Agricultural Reform, 1785–1793’, Agricultural History, 12, no. 3 (1968), 189–200.

34 Smith, Borderland Smuggling, p. 41.

35 Ibid., p. 42.

36 Ibid., p. 69 and further.

37 Peters has expected 20,000 tons each year by 1807. Peters, ‘Gypsum in the United States’, PSPA Memoirs I, pp. 312 and 314.

38 Smith, Borderland Smuggling, p. 69.

39 Richard Peters, ‘Agricultural Inquiries on Plaister of Paris’, in PSPA Memoirs II (1811), Appendix, pp. 1–118, here: p. 86.

40 Smith, Borderland Smuggling, p. 96f.

41 Benjamin Franklin, ‘A Proposal for Promoting Useful Knowledge Among the British Plantations in America, National Humanities Center Resource Toolbox, Becoming American: The British Atlantic Colonies, 1690–1763’ (1743), <http://nationalhumanitiescenter.org/pds/becomingamer/ideas/text4/amerphilsociety.pdf> [accessed 17 December 2017].

42 Franklin also listed: ‘New Improvements in Planting, Gardening, [and] Clearing Land[.]’. Ibid.

43 Only the first edition of the Transactions of the American Philosophical Society lists agriculture as a separate category, see: Transactions of the American Philosophical Society. Held at Philadelphia for Promoting Useful Knowledge, vol. 1, 1 January 1769 to 1 January 1771 (Philadelphia, PA: William and Thomson Bradford, 1771, reprint, New York, NY: Klaus Reprint, 1966).

44 Baatz, “Venerate the Plough”, pp. 3 and 8–10. Ellsworth, ‘The Philadelphia Society for the Promotion of Agriculture’, pp. 189–98.

45 ‘List of Members’, PSPA Memoirs I, pp. XII–XIV.

46 Henry Wynkoop, On Plaister of Paris as a Grass Manure, Read 4 September 1787, MsColl 92, Box 11, pp. 1785–1810, Philadelphia Society for Promoting Agriculture records, University of Pennsylvania, Kislak Center for Special Collections, Rare Books and Manuscripts. (With slightly changes = Copy of a Letter from Mr H. Wynkoop, The Agricultural Society of Canada, On the Effects of Gypsum, p. 8.)

47 Ibid.

48 n.a.: Soil Preparation for Wheat, Draining and Manure, December 1785, MsColl 92, Box 6, Folder 253, Philadelphia Society for Promoting Agriculture records, University of Pennsylvania, Kislak Center for Special Collections, Rare Books and Manuscripts.

49 Ibid.

50 Baatz, “Venerate the Plough”, pp. 14–15. Ellsworth, ‘The Philadelphia Society for the Promotion of Agriculture’, pp. 192–93.

51 Experiments, &c. on the Plaster of Paris, made in the Province of Pennsylvania […], Copy of a Letter from Robert Morris to Jesse Lawrence, The Agricultural Society of Canada, On the Effects of Gypsum, p. 6f. To Morris’s life records, see: Robert Morris (1734–1806), ‘Penn People’, UPenn University Archives & Records Center, <https://archives.upenn.edu/exhibits/penn-people/biography/robert-morris> (accessed 30 October 2019).

52 Other reasons were, for example, a constant lack of money and the outbreak of yellow fever. Baatz, “Venerate the Plough”, pp. XI and 16.

53 Ibid., p. 3 and 8. Ellsworth, ‘The Philadelphia Society for the Promotion of Agriculture’, pp. 191–99.

54 Ibid., p. 191.

55 Peters, ‘On Gypsum’, PSPA Memoirs I, pp. 173 and 175.

56 Id.; Enquiries on Plaister of Paris, p. VII.

57 ‘Chemists … ’, PSPA Memoirs II, Index ‘C’.

58 Peters, ‘On Liming’, PSPA Memoirs II, p. 285.

59 Peters, Enquiries on Plaister of Paris, pp. 84–89 and 94–101.

60 Geerdt Magiels, From Sunlight to Insight. Jan IngenHousz, the Discovery of Photosynthesis & Science in the Light of Ecology (Brussels: Academic and Scientific, 2010), pp. 10–13.

61 Peters, Enquiries on Plaister of Paris, pp. 97–101.

62 Magiels, From Sunlight to Insight, p. 30.

63 Jan Ingenhousz to Benjamin Franklin, Letter from the 5th December 1780, Franklin Papers, ALS: American Philosophical Society, <http://franklinpapers.org/franklin//framedVolumes.jsp?vol=34&page=120b> [accessed 12 December 2017].

64 Jan Ingenhousz to Benjamin Franklin, Letter from the 18th October 1777, Franklin Papers, ALS: Historical Society of Pennsylvania, <http://franklinpapers.org/franklin//yale?vol=25&page=085a&ssn=001-77-0038> [accessed 12 December 2017].

65 Jan Ingenhousz, ‘An Essay on the Food of Plants and the Renovation of Soils’, in Additional Appendix to the Outlines of the fifteenth Chapter on the Proposed General Report from the Board of Agriculture. On the Subject of Manures (London: W. Bulmer, 1796), No. III, pp. 1–20 – Among others, Fordyce can be found in it, too.

66 Jan Ingenhousz, ‘Über Ernährung der Pflanzen und Fruchtbarkeit des Bodens. Aus dem Englischen übersetzt und mit Anmerkungen versehen’ (1798). Nebst einer Einleitung über einige Gegenstände der Pflanzenphysiologie von F. A. von Humboldt, Orig.: An Essay on the Food of Plants and the Renovation of Soils (Eng.), trans. by Gotthelf Fischer von Waldheim (Leipzig: Schäferische Buchhandlung, 1796), p. 114. This also applies to Dundonald, whose work Peters became acquainted with later. Peters, ‘On Gypsum’, PSPA Memoirs I, p. 173.

67 Peters, Enquiries on Plaister of Paris, p. 102.

68 Ibid., pp. 12–14

69 Ibid., pp. 16, 26 and 46.

70 Ibid. p. 31.

71 Ibid., p. 36.

72 Ibid., p. 43.

73 Ibid., p. 82. Id., ‘Inquiries on Plaister of Paris’, PSPA Memoirs II, Appendix, p. 86.

74 Id., Enquiries on Plaister of Paris, p. 82.

75 It cannot be completely excluded that this letter originally came from Peters himself. Also Wynkoop or someone else could have been the author. Anonymous, ‘Extract of a Letter from a Gentleman in the State of Pennsylvania, to his friend in Quebec/Experiments on Gypsum as a Manure’, in On the Effects of Gypsum or Plaster of Paris as a Manure; chiefly extracted from the Papers and Letters on Agriculture, by the Agricultural Society in Canada (London: James Phillips, 1791), pp. 3–5, here p. 3.

76 Peters, Enquiries on Plaister of Paris, p. 82.

77 Ibid., p. 86.

78 ‘My way has been to heat it in a dry pot ; and judge by the ebullition. But now I take it as I can get it’. Peters, ‘Obserations on Colonel Taylor’s Letter’, PSPA Memoirs II, pp. 63–74, here: p. 66.

79 Id., ‘On Gypsum’, PSPA Memoirs I, pp. 157–58.

80 Id., Enquiries on Plaister of Paris, p. 47.

81 Ibid., p. 47

82 Ingenhousz, ‘Über Ernährung der Pflanzen’, p. 114.

83 Peters, Enquiries on Plaister of Paris, p. 69 – In regard to liming land, Peters later emphasized the idea of a tool-like function of manures even more clearly. Id., ‘On Liming Land’, PSPA Mempoirs II, Peters, p. 283. This idea traces back to Wallerius, see: Halm, ‘Eine frühe Konzeption der Agrikulturchemie’ – Wallerius is hardly mentioned in the American context, but his major work on agriculture was at least in Jefferson’s library in Monticello. Browne, A Source Book of Agricultural Chemistry, p. VII.

84 A new commentary in the new edition of the Enquiries makes it clear that this is definitely the senior, about whom Peters was writing. In the footnote, Peters distinguishes between the opinion of the old and the young. Peters, ‘Inquiries on Plaister of Paris’, PSPA Memoirs II, Appendix, p. 54.

85 Duffield in: Peters, Enquiries on Plaister of Paris, p. 47.

86 Duffield also was the executor of Franklin’s last will. Record to Edward Duffield, in ‘Franklin Papers’, <http://franklinpapers.org/franklin//framedNames.jsp> (10 December 2017). Enclosed, Duffield’s son was already taking a contrary view – see: Peters, ‘Inquiries on Plaister of Paris’, PSPA Memoirs II, Appendix, p. [XII] (Contents) and 84.

87 Peters, ‘On Gypsum’, PSPA Memoirs I, p. 171 and Dundonald in: Extracts from Lord Dundonald’s ‘Treatise on the connection of Agriculture with Chemistry. Page 150’, PSPA Memoirs I, Appendix, p. 27–33, here: pp. 30–32. Based on: Archibald Cochrane Dondonald [Earl of], A Treatise, shewing the intimate Connection that subsists between Agriculture and Chemistry. Addressed to the Cultivators of the Soil, to the Proprietors of Fens and Mosses, in Great Britain and Ireland; and to the Proprietors of West India Estates (London: J. Murray and S. Highley, 1795).

88 Peters, ‘Inquiries on Plaister of Paris’, PSPA Memoirs II, Appendix, p. 33. Id., ‘The Efficacy of Sulphur on Vegetation’, PSPA, Memoirs II, p. 207–210.

89 Id., Enquiries on Plaister of Paris, pp. 9–100.

90 Id., On gypsum, PSPA Memoirs I, p. 158.

91 Record to: Seybert, Adam (1773–1825), in: Biographical Directory of the United States Congress, 1774 – Present, Biography, «http://bioguide.congress.gov/scripts/biodisplay.pl?index=S000264» (11/04/2019).

92 Mease wrote to Jefferson in 1803: “I do not understand German, but my friend Dr Seybert of this City is master of that language, and without any possible exception, the best chemist in America theoretical and practical and theoretical.” «https://founders.archives.gov/?q=adam%20seybert&s=1111311111&sa=&r=5&sr=» (12/11/2017)

93 Peters knew, that some scientific texts about plaster written in German existed, albeit he obviously did not know its contents in detail. Peters, Enquiries on Plaister of Paris, p. 83. Id., On gypsum, PSPA Memoirs I, p. 164–165. In regard to Franklin: Letter from Franklin, Benjam to Ingenhousz, Jan (Tue, Oct 2, 1781 to June 21, 1782), Franklin Papers, ALS: American Philosophical Society, «http://franklinpapers.org/franklin//yale?vol=35&page=544b&ssn=001-77-0038» (12/12/2017).

94 Taylor, John (1811): On Gypsum, in: PSPA Memoirs II, p. 51–62 and 75–78.

95 Id. (1813): Arator. Being a Series of Agricultural Essays, practical & political: in Sixty One Numbers, Georgetown (US-CO) {J.M. and J.B. Carter).

96 Peters, ‘Observations on Taylor’, PSPA Memoirs II, p. 66.

97 James Cutbush, ‘Analysis of American Limestone’, in PSPA Memoirs II (1811), pp. 305–08. More to Cutbush, see: Edgar F. Smith, James Cutbush. An American Chemist (1788-1823) (Philadelphia: J. B. Lippincott Company, 1919).

98 Peters, ‘On Gypsum’, PSPA Memoirs I, p. 166.

99 Id., Enquiries on Plaister of Paris, p. 101.

100 See: The Domestic Encyclopaedia. Or a Dictionary of Facts and useful Knowledge. Comprehending a concise View of the latest Discoveries, Inventions, and Improvements chiefly applicable to rural and domestic Economy, ed. by Anthony Florian Madinger Willich and James Mease (in five Volumes), Bd. 3/First American Edition (Philadelphia, PA: William Young Birch, 1803).

101 Willich and Mease, Dictionary, p. 103.

102 Ibid., p. 103.

103 Ibid., pp. 234 and 244.

104 With a reference to Mr. Smythe (?) of the Board of Agriculture in London: Mease, Dictionary, pp. 243–44.

105 Peters, ‘Gypsum in the United States’, PSPA Memoirs I, p. 316.

106 In addition to the already mentioned: Lang, John (1811): Some hints concerning Lime, occasioned by reading ‘Darwin’s Phytologia’, PSPA Memoirs II, pp. 1–8. Thomas Newbold, ‘On Leeced Ashes as a Manure’, PSPA Memoirs II (1811), pp. 105–06. Richard Peters, ‘On Salt as a Manure’, PSPA Memoirs II (1811), pp. 173–77.

107 Id., ‘On Liming Land’, PSPA Memoirs II, p. 276.

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Funding

This work was supported by the Science History Institute, Freundeskreis der Universität Regensburg, and Heinrich Böll Stiftung.