May 192017


On this date in 1743 the Lyonnais physicist Jean-Pierre Christin, permanent secretary of the Académie des sciences, belles-lettres et arts de Lyon, working independently of the Swedish astronomer Anders Celsius (who had developed a similar (but inverted) scale), published the design of a mercury thermometer, the “Thermometer of Lyon” built by the craftsman Pierre Casati that used a scale where zero represented the freezing point of water and 100 represented the boiling point of water at one standard atmosphere. It was, and still is (sometimes), called the centigrade scale although more usually it is called the Celsius scale to honor the first creator even though his scale is not quite the same as the centigrade scale. I tend to vacillate between the two names because I grew up calling it centigrade which seems more etymologically satisfying to me – “centi” (100), “gradus” (degree). Honoring people is all right too, though, as for many SI units: joule, amp, volt, etc. etc. I’ll dribble on a bit about the history of the Celsius scale and then turn my attention to why the US is so resistant to the metric system when the rest of the world uses it more or less happily – even Britain, where such changes do not come easily.


As it happens, the Fahrenheit scale, developed by the Dutch-German-Polish physicist, inventor, and scientific instrument maker Daniel Gabriel Fahrenheit, was published only about 20 years before Celsius and Christin published details of their scales, because at that time there was a pressing need in science for accurate measurements of temperature. Fahrenheit’s scale had three calibration points: the freezing point of a stable mix of ice, water, and ammonium chloride  (0°F), the freezing point of distilled water (32°F), and mean human body temperature (96°F). The latter reference point was later shifted slightly higher. The boiling point of distilled water at one atmosphere was set at 212°F, making the range between the freezing and boiling points of water 180 degrees. 180 is a highly composite number (or anti-prime), meaning that it has numerous divisors, so that, in theory, the scale is useful for mathematical calculations that will result in whole number solutions to various equations.


In 1742 Anders Celsius (1701–1744) published details of  a temperature scale which was the reverse of the scale now known by his name: 0 represented the boiling point of water, while 100 represented the freezing point of water. In his paper “Observations of two persistent degrees on a thermometer,” he documented his experiments showing that the melting point of ice is essentially unaffected by pressure. He also determined with remarkable precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the zero point of his temperature scale, being the boiling point, would be calibrated at the mean barometric pressure at mean sea level.

In 1743 Jean-Pierre Christin published his work on a centigrade scale, and in 1744, coincident with the death of  Celsius, Swedish botanist Carolus Linnaeus (1707–1778) reversed Celsius’ scale, but otherwise kept the intervals between degrees the same. Here we have a, not very well known, example of a common habit of scientists coming up with the same results independently. In this case the coincidence is undoubtedly due to the fact that a metric system of measures across the board makes a great deal of sense for computational purposes. Time is the one variable that won’t play nice.

Linnaeus’ custom-made “linnaeus-thermometer,” for use in his greenhouses, was made by Daniel Ekström, Sweden’s leading maker of scientific instruments at the time and whose workshop was located in the basement of the Stockholm observatory. As it happens, numerous physicists, scientists, and instrument makers at the time are credited with having independently (or semi-independently) developed a centigrade scale; among them, Pehr Elvius, the secretary of the Royal Swedish Academy of Sciences (which had an instrument workshop) and with whom Linnaeus had been corresponding; Daniel Ekström, the instrument maker; and Mårten Strömer (1707–1770) who had studied astronomy under Anders Celsius.

The first known Swedish document reporting temperatures in the centigrade scale is the paper “Hortus Upsaliensis” dated 16 December 1745 that Linnaeus wrote for a student of his, Samuel Nauclér. In it, Linnaeus recounted the temperatures inside the orangery at the University of Uppsala Botanical Garden:

…since the caldarium (the hot part of the greenhouse) by the angle of the windows, merely from the rays of the sun, obtains such heat that the thermometer often reaches 30 degrees, although the keen gardener usually takes care not to let it rise to more than 20 to 25 degrees, and in winter not under 15 degrees…

For a long time the Fahrenheit and centigrade systems had roughly equal followings. In Australia where I grew up, in England where I finished secondary school and attended university, and the US where I lived for 35 years, Fahrenheit ruled in weather reporting and (mostly) in the laboratory. Nowadays only the US and a few scattered islands in the Atlantic and Pacific (mostly US dependencies) use Fahrenheit for weather reporting, and every country in the world uses centigrade for scientific purposes (or the closely related Kelvin scale). Here is a map of the world with those countries using centigrade colored in grey, and those using Fahrenheit colored in green. (You will have to click on the map to enlarge it to see the tiny islands).

Why is the US so resistant to conversion to the metric system in general? I’d say that there are multiple reasons, including a degree of mindless conservatism (coupled with a resistance to the cost of changing).  Clearly such resistance has its down side. For example, the Hubble telescope had to be retrofitted at great expense and inconvenience because the US engineers who designed and built it confused metric and Imperial units of measurement, and ended up at the outset with a telescope in space with a prime reflecting mirror that could not be focused properly.

When it comes to weather reporting I understand why people in the US don’t want to switch from Fahrenheit to centigrade. Fahrenheit has a human dimension to it that centigrade lacks. I can recalibrate Fahrenheit, used for weather reporting, to what I will call the Juan Alejandro Bloody-Bloody Scale thus: 0°F is BLOODY COLD and 100°F is BLOODY HOT. Both ends of this scale represent well understood extremes with round decimal numbers. Centigrade is not round at all at those temperatures. 0°F  is -17.7778°C and 100°F is 37.778°C (approximately).  For round numbers in the centigrade scale you need to pick 0 (which is critical in some ways, such as for frost or plant growth, but not especially cold for humans), and 40 (which is insanely hot, and not very common). Most places I have lived in the world regularly experience one or other of the extremes of the Fahrenheit scales, but not both. My home in the Catskills in New York, however, had the good fortune to experience both on a regular basis. Not the prime reason, but one of several reasons that I do not live there any more.

What I am getting at is that both 0 and 100 in the Fahrenheit scale represent significant milestones (or turning points) in the ways humans feel about local weather conditions. When someone says, “It’s going to hit one hundred (or zero) today” there’s a sense of importance derived from the number itself. There’s a recognizability to the number even though the difference between 99°F and 100°F is hardly noticeable. Hundreds mark significant achievements in human terms: 100 years old, 100th anniversary (i.e. centennial) etc. So in that sense the Fahrenheit scale has a more human feel to it than centigrade (in my opinion). Even though Fahrenheit is not intrinsically decimal, it has a decimal feel to it where it counts in human experience.

Thermometers have limited, but very important, uses in cooking. In particular they are invaluable in sugar cookery. If you check out the HINTS tab of this blog you will find my notes on the various stages of sugar cooking for different confections and the temperatures needed to achieve those stages (in centigrade). For a recipe I want to turn to Lyon, home of Jean-Pierre Christin whom we are celebrating today, and it would be great if there were a local recipe that I could share that uses a sugar thermometer. Lyon is certainly a major culinary center and there are numerous candied treasures to sample, such as the legendary pink pralines or coussins de Lyon. But . . . their production involves trade secrets. Sorry, save your pennies for the air fare. The best I can offer is a recipe for marrons glacés (candied chestnuts) which are a Lyon specialty. Even there I recommend going to Lyon rather than attempting to make them yourself. It’s a very fiddly and time-consuming job.

Let’s start with the French name and what it implies. There are two French words for “chestnut” – marron and châtaigne. The châtaigne is a low grade chestnut normally used for roasting and the typical chestnut that you find in stores outside of southern France and northern Italy. The marron is a high quality chestnut that can cost four or five times more than regular chestnuts, and are the ones you need for this recipe. One thing that is simple about this recipe is the ratio of ingredients 1:1:1:1 – 1 part peeled chestnuts to 1 part sugar to 1 part water to 1 vanilla bean. Now it gets demanding.

Take each chestnut and cut through the tough outer skin all the way around the chestnut so that you cut to the lower membrane, but do not pierce the meat. With a little labor you can peel off the outer skin, but it goes quicker if you place the chestnuts in the microwave on high heat for 20 seconds. This produces some steam as the chestnuts cook a little, loosening the skin. Peel off the tough outer skin being careful not to damage the meat. Then remove the inner skin. Some people use the point of a paring knife, others scrub off the skin with steel wool or an abrasive pad (used only for cooking). Using an abrasive rather than a knife makes damage to the meat less likely. Be prepared for a certain number of damaged chestnuts. These will not make pretty confections, but candy them anyway and then chop them for use with ice cream or in pies and cakes.

Place the water, sugar, and vanilla bean (split lengthwise) in a saucepan and bring to a boil, stirring to dissolve the sugar. Place the peeled chestnuts in a wire basket and lower them into the syrup. Boil vigorously for 1 minute.  Take from the heat and let cool. Keep the chestnuts 24 hours in the syrup, then repeat the process of boiling, cooling, and preserving for 24, hours three times. After the last cooling remove the wire basket from the syrup and separate the chestnuts on wire racks to dry. They are best if eaten quickly !!

May 232015


Today is the birthday (1707) of Carl Linnaeus (also known after his ennoblement as Carl von Linné), Swedish botanist, physician, and zoologist, who laid the foundations for the modern biological naming scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology. Many of his writings were in Latin, and his name is rendered in Latin as Carolus Linnæus (after 1761 Carolus a Linné).

Linnaeus was born in the countryside of Småland, in southern Sweden. He received most of his higher education at Uppsala University, and began giving lectures in botany there in 1730. He lived abroad between 1735 and 1738, where he studied and also published a first edition of his Systema Naturae in the Netherlands. He then returned to Sweden, where he became professor of medicine and botany at Uppsala. In the 1740s, he was sent on several journeys through Sweden to find and classify plants and animals. In the 1750s and ’60s, he continued to collect and classify animals, plants, and minerals, and published several volumes. At the time of his death, he was one of the most acclaimed scientists in Europe.

In August 1728, Linnaeus decided to attend Uppsala University on the advice of a mentor, who believed it would be a good choice if Linnaeus wanted to study both medicine and botany. Although the faculty and lectures had seen better days, Linnaeus met a new benefactor there, Olof Celsius, who was a professor of theology and an amateur botanist. He received Linnaeus into his home and allowed him use of his library, which was one of the richest botanical libraries in Sweden, as well as taking him on specimen collecting expeditions.


In 1729, Linnaeus wrote a thesis, Praeludia Sponsaliorum Plantarum on plant sexual reproduction. This attracted the attention of Olaf Rudbeck of the medical faculty who in May 1730 selected Linnaeus to give lectures at the university even though he was only a second-year student. His lectures were popular, and Linnaeus often addressed an audience of 300 people. In June, Linnaeus moved from Celsius’ house to Rudbeck’s to become the tutor of the three youngest of his 24 children. His friendship with Celsius did not wane, however, and they continued their botanical expeditions. Over that winter, Linnaeus began to doubt the validity of the then current Tournefort system of classification and decided to create one of his own. His plan was to divide the plants by the number of stamens and pistils. He began writing several books, which would later result in, for example, Genera Plantarum and Critica Botanica. He also produced a book on the plants grown in the Uppsala Botanical Garden, Adonis Uplandicus.


During a visit with his parents, Linnaeus told them about his plan to travel to Lapland; Rudbeck had made the journey in 1695, but the detailed results of his exploration were lost in a fire seven years afterwards. Linnaeus’ hope was to find new plants, animals and possibly valuable minerals. He was also curious about the customs of the native Sami people, reindeer-herding nomads who travelled Scandinavia’s vast tundra. In April 1732, Linnaeus was awarded a grant from the Royal Society of Sciences in Uppsala for his journey.

Linnaeus began his expedition from Uppsala in May; he travelled on foot and horse, bringing with him his journal, botanical and ornithological manuscripts and sheets of paper for pressing plants. Near Gävle he found great quantities of Campanula serpyllifolia, later known as Linnaea borealis, the twinflower that would become his favorite. He sometimes dismounted on the way to examine a flower or rock and was particularly interested in mosses and lichens, the latter a main part of the diet of the reindeer, a common and economically vital animal in Lapland.

Linnaeus travelled clockwise around the coast of the Gulf of Bothnia, making major inland incursions from Umeå, Luleå and Tornio. He returned from his six-month-long, over 2,000 kilometer (1,200 mi) expedition in October, having gathered and observed many plants, birds and rocks. Although Lapland was a region with limited biodiversity, Linnaeus described about 100 previously unidentified plants. These became the basis of his book Flora Lapponica.


In Flora Lapponica Linnaeus first used his ideas about nomenclature and classification in a practical way. The account covered 534 species, used the Linnaean classification system and included, for the described species, geographical distribution and taxonomic notes. Flora Lapponica is now credited with being the first modern treatise on botany. The staggering fact about Linnaeus’ system of classification of plants and animals is that it not only organizes them according to perceived PATTERN in nature (very important to Enlightenment thinkers), but inherent in it is the PROCESS whereby the pattern emerged: evolution. Species in the same genus don’t just look alike, they are like “cousins” in a gigantic “family.” Lions and tigers, for example, must have had a common ancestor at some point. This an intellectual hobbyhorse of mine which I could veer off into at this point, but I’ll spare you. Instead, if you are interested, read the chapter on taxonomy in The Natural History of the Traditional Quilt :

[Not sure why Amazon classifies me as an “African Writer”]


It was also during this expedition that Linnaeus had a flash of insight regarding the classification of mammals. Upon observing the lower jawbone of a horse at the side of a road he was traveling, Linnaeus remarked: “If I only knew how many teeth and of what kind every animal had, how many teats and where they were placed, I should perhaps be able to work out a perfectly natural system for the arrangement of all quadrupeds.”

In 1734, Linnaeus led a small group of students to Dalarna. Funded by the Governor of Dalarna, the expedition was to catalogue known natural resources and discover new ones, but also to gather intelligence on Norwegian mining activities at Røros.

Back in Uppsala, Linnaeus’ relations with a colleague who was helping him took a turn for the worst, and thus he gladly accepted an invitation from the student Claes Sohlberg to spend the Christmas holiday in Falun with Sohlberg’s family. Sohlberg’s father was a mining inspector, and let Linnaeus visit the mines near Falun. Sohland’s father suggested to Linnaeus he should take his son to the Dutch Republic and continue to tutor him there for an annual salary. At that time, the Dutch Republic was one of the most revered places to study natural history and a common place for Swedes to take their doctoral degree; Linnaeus, who was interested in both of these, accepted.

April 1735, Linnaeus and Sohlberg set out for the Netherlands, with Linnaeus to take a doctoral degree in medicine at the University of Harderwijk. On the way, they stopped in Hamburg, where they met the mayor, who proudly showed them a wonder of nature which he possessed: the remains of a seven-headed hydra. Linnaeus quickly discovered it was a fake: jaws and clawed feet from weasels and skins from snakes had been glued together. The provenance of the hydra suggested to Linnaeus it had been manufactured by monks to represent the Beast of Revelation. As much as this may have upset the mayor, Linnaeus made his observations public and the mayor’s dreams of selling the hydra for an enormous sum were ruined. Fearing his wrath, Linnaeus and Sohlberg had to leave Hamburg quickly.


When Linnaeus reached Harderwijk, he began working toward a degree immediately; at the time, Harderwijk was known for awarding “instant” degrees after as little as a week. First he handed in a thesis on the cause of malaria he had written in Sweden, which he then defended in a public debate. He is now known to have been wrong about the cause, not having a microscope good enough to see malarial parasites, which were spread by mosquitoes breeding in the water that collected in ruts and puddles.

The next step was to take an oral examination and to diagnose a patient. After less than two weeks, he took his degree and became a doctor, at the age of 28. During the summer, Linnaeus met a friend from Uppsala, Peter Artedi. Before their departure from Uppsala, Artedi and Linnaeus had decided should one of them die, the survivor would finish the other’s work. Ten weeks later, Artedi drowned in one of the canals of Amsterdam, and his unfinished manuscript on the classification of fish was left to Linnaeus to complete.

One of the first scientists Linnaeus met in the Netherlands was Johan Frederik Gronovius to whom Linnaeus showed one of the several manuscripts he had brought with him from Sweden. The manuscript described his new system for classifying plants. When Gronovius saw it, he was very impressed, and offered to help pay for the printing. With an additional monetary contribution by the Scottish doctor Isaac Lawson, the manuscript was published as Systema Naturae (1735).


Linnaeus became acquainted with one of the most respected physicians and botanists in the Netherlands, Herman Boerhaave, who tried to convince Linnaeus to make a career there. Boerhaave offered him a journey to South Africa and America, but Linnaeus declined, stating he would not stand the heat. Instead, Boerhaave convinced Linnaeus that he should visit the botanist Johannes Burman. After his visit, Burman, impressed with his guest’s knowledge, decided Linnaeus should stay with him during the winter. During his stay, Linnaeus helped Burman with his Thesaurus Zeylanicus. Burman also helped Linnaeus with the books on which he was working: Fundamenta Botanica and Bibliotheca Botanica.


Linnaeus’ classification system revolutionized biology in many ways. Most importantly it paved the way for the development of theories of evolution. The Linnaean system classified nature within a nested hierarchy, starting with three kingdoms. Kingdoms were divided into classes and they, in turn, into orders, and thence into genera (singular: genus), which were divided into species (singular: species !!!). Below the rank of species he sometimes recognized taxa of a lower (unnamed) rank; these have since acquired standardized names such as variety in botany and subspecies in zoology. Modern taxonomy includes a rank of family between order and genus and a rank of phylum between kingdom and class that were not present in Linnaeus’ original system.

Linnaeus’ groupings were based upon shared physical characteristics, and not simply upon differences. Of his higher groupings, only those for animals are still in use, and the groupings themselves have been significantly changed since their conception, as have the principles behind them. Nevertheless, Linnaeus is credited with establishing the idea of a hierarchical structure of classification which is based upon observable characteristics and intended to reflect natural relationships. While the underlying details concerning what are considered to be scientifically valid “observable characteristics” have changed with expanding knowledge (for example, DNA sequencing, unavailable in Linnaeus’ time, has proven to be a tool of considerable utility for classifying living organisms and establishing their evolutionary relationships), the fundamental principle remains sound.


According to German biologist Ernst Haeckel, the question of the origin of humans began with Linnaeus. He helped future research in the natural history of Homo sapiens by describing humans just as he described any other plant or animal. Linnaeus classified humans among the primates (as they were later called) beginning with the first edition of Systema Naturae. During his time at Hartekamp, he had the opportunity to examine several monkeys and noted similarities between them and humans. He pointed out both species basically have the same anatomy; except for speech, he found no other differences. Thus he placed humans and monkeys under the same category, Anthropomorpha, meaning “like humans.” This classification received criticism from other biologists such as Johan Gottschalk Wallerius, Jacob Theodor Klein and Johann Georg Gmelin on the ground that it is illogical to describe a human as “like a human.” In a letter to Gmelin from 1747, Linnaeus replied:

It does not please [you] that I’ve placed Man among the Anthropomorpha, perhaps because of the term ‘with human form’, but man learns to know himself. Let’s not quibble over words. It will be the same to me whatever name we apply. But I seek from you and from the whole world a generic difference between man and simian that [follows] from the principles of Natural History. I absolutely know of none. If only someone might tell me a single one! If I would have called man a simian or vice versa, I would have brought together all the theologians against me. Perhaps I ought to have by virtue of the law of the discipline.

There were, of course, reactions from the church. First, putting humans at the same level as monkeys or apes lowered the spiritually higher position that humans were assumed to have in the great chain of being. Second, because the Bible says humans were created in the image of God (theomorphism), if monkeys/apes and humans were not distinctly and separately designed, that would mean monkeys and apes were created in the image of God as well. This was something many could not accept. The conflict between world views that was caused by asserting humans are a type of animal is ongoing. Linnaeus started it.

After such criticism, Linnaeus felt he needed to explain himself more clearly. The 10th edition of Systema Naturae introduced new terms, including Mammalia and Primates, the latter of which would replace Anthropomorpha as well as giving humans the full binomial Homo sapiens. The new classification received less criticism, but many natural historians still believed he had demoted humans from their former place to rule over nature, not be a part of it. Linnaeus believed that humans biologically belong to the animal kingdom and had to be included in it. In his book Dieta Naturalis, he said, “One should not vent one’s wrath on animals. Theology decrees that man has a soul and that the animals are mere ‘aoutomata mechanica,’ but I believe they would be better advised that animals have a soul and that the difference is of nobility.”

Linnaeus added a second species to the genus Homo in Systema Naturae based on a figure and description by Jacobus Bontius from a 1658 publication: Homo troglodytes (“caveman”) and published a third in 1771: Homo lar. Swedish historian Gunnar Broberg states that the new human species Linnaeus described were actually simians or native people clad in skins to frighten colonial settlers, whose appearance had been exaggerated in accounts to Linnaeus.

In early editions of Systema Naturae, many well-known legendary creatures were included such as the phoenix, dragon, and manticore as well as cryptids like the satyrus, which Linnaeus collected into the catch-all category Paradoxa. Broberg thought Linnaeus was trying to offer a natural explanation and demystify the world of superstition. Linnaeus tried to debunk some of these creatures, as he had with the hydra; regarding the purported remains of dragons, Linnaeus wrote that they were either derived from lizards or rays. For Homo troglodytes he asked the Swedish East India Company to search for one, but they did not find any signs of its existence. Homo lar has since been reclassified as Hylobates lar, the lar gibbon.


In the first edition of Systema Naturae, Linnaeus subdivided the human species into four varieties based on continent and skin color: “Europæus albus” (white European), “Americanus rubescens” (red American), “Asiaticus fuscus” (brown Asian) and “Africanus Niger” (black African). In the tenth edition of Systema Naturae he further detailed stereotypical characteristics for each variety, based on the concept of the four temperaments from classical antiquity, and changed the description of Asians’ skin tone to “luridus” (yellow). Additionally, Linnaeus created a wastebasket taxon “monstrosus” for “wild and monstrous humans, unknown groups, and more or less abnormal people.”

Linnaeus travelled Scandinavia and nearby parts of Europe, but, because he lived in the great Age of Discovery, his disciples journeyed the world and expanded his system greatly. Every ship sent out to map the world had at least one naturalist aboard. What Linnaeus set in motion is incalculable in any number of scientific fields from Anthropology to Zoology.

On his travels Linnaeus visited Gotland, largest of the Baltic Islands, and on my foodie bucket list. The most famous regional dish is Saffron Rice pudding “Saffranspannkaka”. It is served with whipped cream and dewberry jam ”Salmbärssylt”. Other traditional dishes include “Glödhoppa” (lightly cured lamb, boiled, then fried with a mustard-coating) and “Ugnstrull” (a rye bun filled mainly with pork). Where’s my plane ticket?

I’m in a dreadful rush, so here’s a recipe for Saffranspannkaka modified from here:




1 cup short-grain rice

1⁄2 teaspoon salt

1 1⁄2 cups water

1 1⁄4 cups cream

1 cup milk

1/4 teaspoon saffron

2 tablespoons sugar

1⁄2 cup almonds, skins removed and roughly chopped

5 eggs


Boil the rice on low heat with the salt and water until it is almost dry.

Blend in the cream and continue to boil. Pour in the milk and stir to form a creamy porridge.

Take off the heat and stir in the saffron, sugar and almonds.

Beat the eggs and add them to the porridge, stirring well to combine.

Pour the batter into a buttered oven dish about 11 x 15 inches.

Bake at 225°C/435°F about 30 minutes. Test with a toothpick. It should not be too dry or too moist.

When serving, cut it up directly from the dish and serve with whipped cream and dewberry (traditional), lingonberry, or mulberry jam.