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WorkÉmilie du Châtelet

Dissertation on the Nature and Propagation of Fire

Her anonymous entry for the Académie's prize on fire, written without Voltaire's knowledge, argues that fire weighs nothing and drives the parts of every body apart.

by Émilie du Châtelet132 passages held

  • French, the original language
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Original title
Dissertation sur la nature et la propagation du feu
First published
(aged 32)
Original language
French

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Overview

When the Académie des sciences in Paris set the nature and propagation of fire as the question for its prize of 1738, Voltaire, who shared the château of Cirey with Émilie du Châtelet, began experimenting for an entry. She prepared one of her own without telling him and sent it in anonymously in August 1737. Her essay argues that fire is a substance unlike all others: it has no weight, it is drawn toward no centre, and its universal effect is neither heat nor light but expansion, swelling bodies and forcing their parts apart. Light and heat are two separate ways it acts on us, and she shows them coming apart: moonlight gathered by a burning glass gives light without warmth, while iron about to catch fire burns the hand without shining. Against reports that metals heated in a burning mirror grow heavier, she cites masses of iron, from one pound to two thousand, weighed in her presence while glowing and again when cold: the weight did not change. She also asks whether colour matters. She had a cloth dyed in the seven colours of the prism, wetted it evenly, and watched violet dry first and red last; she then urged the judges to test whether red rays heat more than violet ones, an experiment she had not been able to make herself. The prize went to Leonhard Euler, the Swiss mathematician, and two other entrants, but the Académie printed her essay and Voltaire's alongside the winners in 1739. She went on revising it, and in 1744 the Paris bookseller Prault issued the revised text as a separate book, in two parts that end on thirteen and eighteen numbered conclusions, the last of them that a central fire burns inside the Earth.

Key concepts

What does rarefaction mean in du Châtelet's essay on fire?

It is fire's universal effect: swelling a body in every dimension and, if fire keeps acting, separating its parts down to their elements. It does not depend on heat or light, since air on high mountains is rarefied where no warmth is felt. Even bodies that shrink in fire, like horn, fit the rule: fire has first driven out the water between their parts, leaving them more compact.

Why does the essay call heat and light modes of fire?

A mode is a way a thing exists, not the thing itself. Light is fire travelling in a straight line to the eye, and heat is the agitation fire stirs in every direction once it enters our pores. The two behave differently: veil a burning mirror and the light at its focus vanishes at once, while a body placed there stays hot for a long time afterwards.

What does it mean that fire tends to equilibrium?

Fire spreads evenly through space whenever nothing stops it, so in the same air every lifeless body holds the same amount. It is shared out by space, not by mass: gold and an emptied air pump contain equally much. A glowing body touched to a cold one gives up fire until the two are level, which is also why everything heated cools again.

Why does friction matter so much in the essay's account of fire?

Because rubbing does not create fire, it rouses fire already lodged between the parts of bodies. Iron struck on stone vitrifies almost at once, and the experiment works in shade and at night as well as in sunlight, which shows that not all fire comes from the Sun. The essay ranks this friction the most powerful way to excite fire, more so with heavier, more elastic and faster bodies.

What is the central fire in the essay on fire?

A store of fire placed by the Creator at the Earth's centre, warming it independently of the Sun. Mairan had calculated the summer Sun's heat at sixty-six times the winter Sun's, yet thermometers show summer differing from freezing only as eight from seven, so a stock of heat must lie below. Volcanoes, hot springs and deep wells that never freeze are its signs, and its heat rises with depth.

Themes of the book

What this book returns to, gathered into themes and ordered by how much of the text each one occupies.

Fire without heat or light

If moonlight can shine without warming and iron can burn without shining, what is fire itself? The essay looks for a sign of fire that does not depend on human senses.

Heat and light, du Châtelet argues, are two separate ways fire acts on us, not its essence: light is fire reaching the eye in a straight line, heat the agitation it stirs in our pores. A blind person would define fire as what warms, someone without touch as what shines, and beings on a globe near Sirius with neither sense would have no idea of it, though fire would be there all the same. Its universal mark can be seen, touched and measured: it swells bodies in every dimension and, if it keeps acting, drives their parts asunder. Motion does not make fire. Fire makes the inner motion of bodies.

  • fire
  • heat
  • light
  • perception
  • causation
  • motion
  • thermal expansion
  • rarefaction
  • thermometry
  • measurement
  • scientific explanation
  • matter

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A substance that weighs nothing

Does fire have weight like every other body, or is it the one thing that flees the Earth's centre? The answer decides whether fire belongs to ordinary matter at all.

Chemists reported that metals heated in a burning mirror grew heavier. Du Châtelet blames what the fire carried in: particles scraped from the iron spatula used for stirring, salts and sulphurs from the air. Her own evidence is iron weighed glowing and again cold, from one pound to two thousand, with no difference. Fire, she concludes, weighs nothing, or too little ever to be felt, and it rises rather than falls, the perpetual antagonist of weight, without which everything would be packed solid. Whether fire is impenetrable she leaves open, since countless rays cross through a pinhole without blurring.

  • weight
  • gravity
  • matter
  • matter theory
  • impenetrability
  • experiment
  • experimental philosophy
  • combustion
  • optics
  • measurement
  • fire

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From a dyed cloth to the fire under the Earth

How does fire spread through things, and where does it come from if not only from the Sun? The second half of the essay follows fire into colours, ice, the Sun and the depths of the Earth.

Fire is spread evenly through all lifeless bodies, so that two stones struck together kindle it at night as well as by day: not all fire comes from the Sun. Du Châtelet had a cloth dyed in the seven colours of the prism, wetted it evenly and watched violet dry first and red last, and she asked for a test of whether red rays heat more than violet. The Sun, she argues, must be a solid body, or it would scatter in an instant. A thermometer reads warmer in a cellar 84 feet deep than in one of 30, which points to a fire at the Earth's centre.

  • color
  • optics
  • central heat
  • freezing
  • theories of cold
  • friction
  • vacuum
  • electricity
  • elasticity
  • cohesion
  • natural philosophy
  • heat
  • light

Enter a dialogue

Within this work

passages held
132
distinct concepts
150
by passages held, corpus-wide
#448

What this book thinks together

The wheel takes this book’s leading concepts and shows how often they come up together. The wider the band between two, the more of its passages speak of both. Among them, most often together: “fire” and “heat”.
Concept co-occurrence, strongest first 8 concepts, joined by 28 pairings. 82 pairings reach beyond these concepts and are not drawn.
ConceptPaired conceptShared passages
fireheat24
firematter18
heatmatter15
causationheat11
fireperception10
causationfreezing8
heatperception8
firelight7
firemotion7
heatlight7
heatmotion7
causationfire6
causationmatter6
freezingheat6
mattermotion6
lightmatter4
freezingmatter3
lightmotion3
freezingmotion2
lightperception2
causationlight1
causationmotion1
causationperception1
firefreezing1
freezinglight1
freezingperception1
matterperception1
motionperception1

Works held

The author's work in order, this book marked in place. Your-language title first, the original beneath it where the two differ; side chips show which full texts are held.

  1. 1738 Dissertation on the Nature and Propagation of Fire (Dissertation sur la nature et la propagation du feu) you are here FR
  2. 1741 Réponse à la lettre de M. de Mairan sur la question des forces vives

    A sequel to her Institutions de physique (1740): Mairan's attack was on that book, and this public letter defends its case for living forces.

     FR
  3. 1746 Discourse on Happiness (Discours sur le bonheur)

    Unlike her physics, a private essay on how to live, written in the mid-1740s and put into print thirty years after her death.

     FR
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