Boerhaave’s furnace: the search for peat

Last week, I heard on the news that global oil demand is expected to fall to a record low in 2020 due to the corona crisis. Given the significant role of fossil fuel combustion in climate change, this may not be such a bad thing. It also reminded me of a fossil fuel that has all but disappeared: peat. Although peat is not strictly a fossil fuel – it is renewable, but extremely slowly -, its greenhouse gas emissions are comparable to that of fossil fuels. When Ruben Verwaal and I were working on our project on Boerhaave’s chemical oven, about which we wrote before, one of the issues we struggled with was that of peat.

Our Boerhaave furnace with some glowing peat inside
Our Boerhaave furnace with some glowing peat inside

In his Elementa Chemiae, Boerhaave states that the furnace should be fuelled by ‘a glowing Dutch coal’ (Batavi prunam candefactam), first burnt until it yields no more smoke’, which is put on a thin layer of ash on the bottom of an earthenware vessel, and covered with a layer of ash as well. This, he claims, will produce ‘an equable, moderate heat’, which ‘may be kept up for near twenty-four hours.[1] This posed a number of problems. Primarily, this instruction raised the question what Boerhaave meant by ‘Dutch coal’, as no coal was mined in the Dutch Republic at the time. The only ‘Dutch’ coal mines at the time were in the south, in the area under Austrian Habsburg rule, which makes Dutch stone coal an unlikely option. Indeed, the 1741 English translation hints at a different kind of fuel: here, the translator speaks of ‘Dutch turf’ (Italics original).[2]

‘Turf’ is the Dutch term for peat. This was in fact produced in considerable amounts in the Dutch Republic and the most widely used fuel there in the eighteenth century.[3] It has been signalled before that availability of particular kinds of fuel influenced the design and use of furnaces. The increasing deforestation of Europe saw wood replaced by peat and coal, developments which shaped pyrotechnical innovations from the sixteenth century onwards.[4] Peat generally has a much lower heating value than wood and coal – it produces less energy than those fuels when burned.[5] Yet peat burns slowly and evenly; characteristics that indeed seem desirable for a small wooden furnace that can also supposedly be used to hatch eggs, a process that requires a constant temperature of 37.5°C in case of a chicken egg.

That did not solve the problem of what to fuel our furnace with: there are different varieties of peat, so which one did Boerhaave mean? The most distinctive types of peat produced in the Dutch Republic were those from high moors and low moors (hoogveen and laagveen). These peatlands were too wet to just dig the peat up and use it. High moors, mostly situated in the east of the country, could be drained by digging canals, but low moors, which were found predominantly in the west, could only be extracted by dredging the peat from water, and spreading this ‘mud’ on fields to dry, where it would be compacted by stamping it with wooden slats, after which it could be cut into chunks.[6]

Abraham Rademaker (1676/77-1735), Production of low moor sapric peat (‘slagturf’) near Amstelveen, about 30 kilometers from Leiden. Washed ink drawing. Reproduction courtesy of Noord-Hollands Archief, Provinciale Atlas – Prenten en Tekeningen, Inventarisnummer NL-HlmNHA_359_000279_K

Hence, peat from high moors tended to have a different structure than that from low ones. Moreover, there are various classification systems in use. The most commonly used one distinguishes fibric, hemic, and sapric peat. Fibric peats are the least decomposed and consist of intact plant fibers, and tend to be won from the top layers of soil. Hemic peats contain partially decomposed plants, and sapric peat is the most decomposed variety, dug from the deepest layers.[7] Hard sapric peat, especially from the low moors, was generally considered to be most suitable for heating houses, while the more loosely structured hemic peat from the high moors was predominantly used in businesses that required intensive heating such as those of dyers, brewers, and potters. Fibric peat was mainly used to fertilize soil. As peat had great economic value, trade was well-regulated. Local markets were protected, but specific varieties of peat were transported by special boats to other provinces and even countries where that specific variety was not available.[8]

Differently produced varieties of peat, Veenpark, October 2019. Left to right: automatically dug sapric peat, manually dug sapric peat, and manually dug hemic peat, all from a high moor. Photo: author.

These insights, gained from secondary literature and interviews with volunteers at the peat museum (Veenpark) in Barger-Compascuum in the east of the Netherlands, led us to believe that the Dutch peat Boerhaave was referring to was most likely hard sapric peat from low moors near Leiden, such as the area of Zoeterwoude, which had a long history of peat extraction.[9] This however created a new problem: fuel peat is no longer won commercially in the Netherlands, as its peat lands have long been depleted. And although the country imported 2,252 million kg of peat in 2018, this was almost exclusively fibric peat for gardening and greenhouse agriculture.[10] The only fuel peat we could find for sale was automatically dug, strongly pressed Irish peat, which for some obscure reason could only be purchased through a US web shop and took weeks to ship. Although this is indeed sapric peat, it is more likely to be from a high moor, and produced through automated digging, rather than won by hand. This makes for a much denser, dryer structure then when the peat is dug manually. However, it was the best we could find, and it forced us to keep in mind that the peat Boerhaave used may have burned differently than ours.

Looking back from the situation we are in now, these concerns may seem pedestrian. Maybe we can use them as a small reminder that people in the past too struggled with energy transitions and public health issues, and that for all the stupidity and misery in the world, there is also a lot of flexibility, creativity and inventiveness.

[1] Herman Boerhaave, Elementa Chemiae : Quae Anniversario Labore Docuit, in Publicis, Privatisque, Scholis, 3 vols.,vol. 1 (Lugduni Batavorum: Isaac Severinus, 1732), p. 888.

[2] Herman Boerhaave, A New Method of Chemistry : Including the History, Theory and Practice of the Art / Translated from the Original Latin of Dr. Boerhaave’s Elementa Chemiae, as Published by Himself. To Which Are Added, Notes and an Appendix, Shewing the Necessity and Utility of Enlarging the Bounds of Chemistry. By Peter Shaw., trans. Peter Shaw (London: T. Longman, 1741), p. 590.

[3] Jan Willem de Zeeuw, Peat and the Dutch Golden Age : the historical meaning of energy-attainability (Wageningen : Afdeling Agrarische Geschiedenis Landbouwhogeschool, 1978), p. 3-31.

[4] Archibald Clow, Nan L. Clow, The Chemical Revolution. A Contribution to Social Technology (London: Batchworth Press, 1952), pp. 27-29, 271. Peat too, has been used for glassmaking, albeit to a significantly lesser extent. Mogens Schlüter, “The Use of Peat in Danish Glassworks, 1825–1945.” Journal of Glass Studies 30 (1988), 94-101.

[5] For an overview of heating values, see.g.

[6] M.A.W. Gerding, Vier Eeuwen Turfwinning in Groningen, Friesland, Drenthe en Overijssel tussen 1550 en 1950 (‘t Goy-Houten: HES Uitgevers B.V., 1995), p. 34.

[7] Take Stol, De Veenkolonie Veenendaal. Turfwinning en waterstaat in het zuiden van de Gelderse vallei (Walburg Pers / Stichtse Historische Pers, 1992), pp. 148-150. For an overview of peat classification in English, see (last consulted 22 January 2020).

[8] Stol 1992, p. 150. A.J.J. van ‘t Riet, Meeten, boren, en besien. Turfwinning in de buitenrijnse ambachten van het Hoogheemraadschap van Rijnland 1680-1800 (PhD thesis, Leiden University, 2005), pp. 214-5.

[9] Boerhaave famously only left Leiden once in his life, in 1693, when he travelled to Harderwijk to obtain his degree in medicine. On peat production near Leiden, see Milja van Tielhof, “Turfwinning en Proletarisering in Rijnland 1530-1670,” Tijdschrift voor Economische en Sociale Geschiedenis, 2005, vol. 2:4, pp. 95-121.

[10] See (last consulted 22 February 2020).

A short history of respiratory illness epidemics (2)

*This blog post first appeared in Dutch on *

Last week, I discussed that from antiquity until well into the nineteenth century, the idea that contagious diseases were caused by the influence of celestial bodies, the weather, and climate, was common. We still see these ideas in our language: think of catching a cold. This explains why until the twentieth century, quarantines and isolations were not used to battle epidemic respiratory illnesses. After all, if an illness is caused by the weather, isolating patients has little use. The best option, usually only available to the wealthy, was to stay inside, warmly wrapped up.

Quarantining was an existing practice, but it was mostly used in other diseases. During a plague epidemic in Italy in the fourteenth century for example, the crew of mooring vessels was kept on the boat for forty days (quarantaine) to prevent infections.[1] So even though the contagious nature of some diseases and the fact that their spread can be stopped by isolating (suspected) patients have been understood for centuries, isolating patients with respiratory illnesses is a much more recent phenomenon. Only in 1898 did Dutch microbiologist Martinus Beijerinck coin the term ‘virus’ to describe what, up till that point, had been considered extremely small bacteria. And only in 1901 an influenza virus was first isolated, in poultry. The Spanish flu epidemic of 1918 was, in all likelihood, the first flu epidemic in which quarantine was used widely to manage the disease.

Detail of Jan Luyken, The Apothecary (1694), ets. Rijksmuseum RP-P-OB-44.502

Of course, people did try to manage and cure respiratory illness before the late nineteenth century too. Until the 1850s, most people depended on selfcare: ‘cures’ bought at the pharmacist, from herbal healers, or made from supplies from their own garden or pantry. Those who could afford it asked a doctor for advice, who would visit the patient at home and might give them a recipe for the apothecary. Hospitals were places where poor people would go if they were at the end of their tether, and no one could take care of them at home. Most people who went into a hospital had little hopes of coming out alive.[2]

Physicians like the Amsterdam medical doctor Steven Blankaart (1650-1704) advised rest and warm coverings in case of coughing and colds, very much in line with Hippocratic understandings of colds as caused by the weather. He also prescribed cures prepared by pharmacists, which could contain ingredients that we still use in cough medicine today, such as ginger and aniseed, but also plants and substances that have been nearly forgotten now. Blankaart warned that using sugary syrups and pastilles was useless, and that so-called plasters, swaths of fabric drenched in extracts, were no good either. The only possible exception were plasters containing substances like camphor, because the smell – much like Vicks VapoRub today – could ease the patient: “Some place plasters on the chest, but I cannot see what use they have, because this means should penetrate the lungs through the breastbone, which would be absurd, therefore these means are of no importance, unless they reek of Musk, Saffron, or Camphor, &C. And that smell by breathing it in could do something useful in our blood.”[3]

Sweets and substances that are quite similar to modern liquorice were popular though, something we see reflected in books like ‘The Perfect Dutch Kitchen Maid’ (De Volmaakte Hollandsche Keuken-Meid, 1752). Here ‘chest sugar’, sugar pastilles with expensive exotic spices like saffron or cloves, and ‘tablets of liquorice’, made from liquorice extract, aniseed, Arabic gum, and rosewater were recommended for colds and coughs respectively.[4]  Less prosperous citizens had to make do with drinks made of cucumber juice or marjoram, or brews with aniseed, fennel seed, liquorice, honey, or hyssop.[5]

Cures for colds and coughs, Steven Blankaart, Verhandelinge van de Opvoedinge En Ziekten Der Kinderen (Amsterdam: Hieronymus Swierts, 1684), p. 176.

Although such preparations, either made by the apothecary or at home from the pantry, were probably easing colds, they of course did not cure respiratory illnesses – although that is not that different today. In premodern descriptions of epidemics of respiratory illness, it is often noted in a rather off-hand way that it were mostly the elderly who died from them. ‘Elderly’ is relative of course, and in the past people grieved the loss of their loved ones too. But such remarks do suggest that death was much more present in everyday life than it is today; and that would not change until the second half of the nineteenth century.

Finally, we have seen over the past few weeks that scientists are trying to find a vaccine against covid-19. The first rudimentary vaccines in Europe, against smallpox, date back to the eighteenth century. In China and Asia, such immunisation practices had existed much longer.[6] Bacterial pneumonia could increasingly be treated successfully from the start of twentieth century, especially when penicillin became commercially available.  The Spanish flu epidemic of 1918 led to a search for new treatments for flu. This would eventually result in the first flu shots during World War II, developed by the American army.

The history of our understanding of and ways of dealing with epidemic respiratory illnesses thus shows that we have come to understand the causes, spreading, and effects of respiratory infections in completely new ways over the past 150 years. However, there is still a lot of confusion among the general public about the differences between flu, colds, and infections like covid-19. We have become much more successful in treating severe cases of lower respiratory tract infections, but the treatment of upper respiratory tract infections has not changed significantly since the seventeenth century. We have relatively little experience in the prevention, curtailing, and ‘flattening’ of epidemics of respiratory infections, which partly explains the wide variety of current measures.

[1] See e.g. Monica Green (ed.) “Pandemic Disease in the Medieval World”, special issue of The Medieval Globe, vol. 1, 2014.

[2] See e.g. Ruth Richardson, Death, Dissection, and the Destitute (Chicago: University of Chicago Press, 2001).

[3] Steven Blankaart, Verhandelinge van de Opvoedinge En Ziekten Der Kinderen (Amsterdam: Hieronymus Swierts, 1684), p. 173-180: “Op de borst leggen sommige Pleisters, maar ik kan niet sien wat groote nut zy konnen uitrichten, want dit Middel zoude moeten door het Borst-been tot in de Longe doordringen, het welke absurd soude zijn, derhalven zijn die Middelen mede al van geen belang, ten zy ze riekende zijn van Moschus, Saffraan, Campher, &c. En die reuk door het inademen onse sappen en bloed eenig nut aanbracht.”

[4] De Volmaakte Hollandsche Keuken-Meid… Als Meede Eenige Huismiddelen. Voor de Verkoudheid (Amsterdam: Steven van Esveldt, 1752)

[5] Evert Jan Thomassen a Thuessink, Prysverhandeling over de Vraag, Voorgesteld Door Het Geneeskundig Genootschap […] Servandis Civibus, in Hoe Verre Zou Men, by Gebrek van de Apotheek, Uit Kelder En Keuken de Vereischte Geneesmiddelen […] Kunnen Bekomen. (Amsterdam: Petrus Conradi, 1789), p. 11, 192. Heyman Jacobaus, Schat Der Armen, of Huismedicyn Boekje, 1606, p. 49, 197.

[6] See e.g. Anne Eriksen, “Cure or Protection? the Meaning of Smallpox Inoculation, ca. 1750—1775”, Medical History 57(4):516-36 (2013).