Émilie du Châtelet - An Essay On Heat - 1739 - #1

In 1739 the Paris Academy of Sciences proposed a question: what is fire?  A prize was offered for the best response. Entries were to be presented anonymously. The prize was awarded to Euler.  Voltaire, who had also entered the competition, did not know until the list of entrants was published with the prize award notification that his entry had been in competition against one from his lover.  Although Émilie du Châtelet did not win the prize, her entry was considered so remarkable that, at the request of Réaumur, the Academy decided to have it printed at its own expense.

Émilie du Châtelet's 1738 essay - Dissertation sur la nature et la propagation du feu - deserves, in my opinion, a much wider readership.  In her dissertation on heat* she critically examined the then current state of knowledge and theory - and extended it.  The dissertation covers four main topics: thermometers; light; the nature of heat; the formation of ice.  At that time many philosophers thought that ice formation could be caused by chemicals in the environment.  The latter theory is now disproven, but the remainder of the essay still offers much of scientific and historical value.

[*]  The French word 'feu' usually means fire, light or lamp.  I translate it here as 'heat' because that, in essence, is the topic of the Dissertation.


Émilie du Châtelet's name is most frequently linked to that of Voltaire.  That should not be surprising: they were science collaborators, science rivals and lovers.  But for the purposes of this article, the link between du Châtelet and Newton appears to me to be of much greater importance to science.

The age in which Newton published his theories was an age dominated by two 'establishments' - one the church and the other the dominant school of natural philosophy.  In England, as in many European countries at that time, church and state were one.  Thus it was that every natural philosopher had to avoid any perception of heresy or treason in his or her writings.

Newton's writings on gravity supported the idea of a Sun-centered universe, a universe which some die-hard religious zealots were still foolishly attempting to refute.  As to the philosophers, the dominant gravitational theory of the day was the vortex theory, of Descartes and Huygens.  Newton was much ridiculed by his opponents on that score.

Newton's theories did not suddenly open the eyes of the scientific world.  It took some time for his theories to be accepted and improved on.  A full understanding of Newton required the mathematical skill to understand his new method of calculating masses and orbits.  There was amongst mathematicians one who not only fully understood Newton's theories, but understood them enough to point out errors.  That mathematician was Émilie du Châtelet.

In the prevailing religious and social context it is easy to see why Émilie du Châtelet felt the need to mention the role of the Creator in her dissertation.  It appears to me that this was not in any way an appeal to magic as an explanation of physical phenomena: it was a suggestion that if the Creator had made matter, energy and laws, then He had no need to specially create every single thing in the universe.

Sir Isaac Newton "has demonstrated to the eye, by the bare assistance of the prism, that light is a composition of coloured rays, which, being united, form white colour. A single ray is by him divided into seven, which all fall upon a piece of linen, or a sheet of white paper, in their order, one above the other, and at unequal distances. The first is red, the second orange, the third yellow, the fourth green, the fifth blue, the sixth indigo, the seventh a violet-purple. " - Voltaire.

Émilie du Châtelet demonstrated that "It is very possible that ... there are in Nature other colors than those that we know of in our world."

I have transcribed the original text into plain text.  The original uses an F and an S that are nearly identical; there are some Middle French spellings; there are some obvious typographical and spelling errors.  Thus, despite the great care I have taken, there are almost certainly going to be minor errors still in my plain text transcription.  The dissertation is rather long at 139 small pages - about 30 A4 pages equivalent - so I have separated it into two parts where, rather conveniently, the original is in two logical parts. 

The two parts of the transcription are posted here:
Émilie du Châtelet - An Essay On Heat - 1739 - #2
Émilie du Châtelet - An Essay On Heat - 1739 - #3

A translation is in hand.

In the dissertation, many philosophers are cited.  Many of the names are spelled strangely, and many are not widely known.  Accordingly, to assist readers, I list here these names, with alternative spellings and links.

Citations in the essay:

de Billerez - M. Billerez - see note below.
Boërhaave (Boerhaave)
de Boze - M. des Boz - see below.
Faheinrheit (Fahrenheit)
see also, in French,
Hartsoëker (Hartsoeker)
Hauksbée (Hauksbee)
de Mairan
de Musschenbroek, also as: de Mulkhenbroëk
de Réaumur
Roëmer (Rømer , Roemer)
de Tournefort

Note: the names above which are not linked to web pages were cited by Émilie du Châtelet in connection with ice in caves, such as that at Besançon. For information on that topic, please see
Ice caves of France  &  Switzerland by G.F. Browne, chapter XV11.