Extremely Rare Reaumur Manuscript on Condensation and the Life Cycle of a Caterpillar

Signed by Rene Antoine Ferchault de Reaumur

Item: 1933
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REAUMUR, RENE ANTOINE FERCHAULT DE. (1683-1757). French entomologist, meteorologist and naturalist; originator of the Reaumur temperature scale. AMs. (Unsigned). 2pp. 4to. N.p., N.d. Autograph manuscript notes for a meteorological experiment plus observations about a caterpillar written on the sheet’s verso.



if very cold air will condense according to the same barometric points as ordinary air does

and if it will condense as much by the same procedures

This is an element which will enter into calculations which are made regarding the weight of air in the atmosphere. There is very cold air in the atmosphere… trial with a mixture of wine spirit in a tube sealed hermetically.


“the pink caterpillar of the cherry tree. You find the same one, or one that resembles it very much, on the pear tree. It doesn’t have any feelers and a simple [?]. It is quite pretty. The body is a pearl grey and it has a border of [?] yellow on the back and [?] the legs, it is all yellow. It has 16 legs. All the black dots that mark it are small black grains that are raised. They made their cocoon around the fifteenth of July. They are of white silk, rather thin, but tight nevertheless.

1 the caterpillar

2 the cocoon

3 the chrysalid

4 the butterfly born in the month of September or October. It was born while I was not present. It belongs to the class of those with antennae or articulated feelers, (one can distinguish them from fixed feelers) and which have no proboscis. In so far as one can tell from a dead specimen it seems to carry its wings horizontally. The predominant color of the upper wing is a brownish blue on which there are greyish spots. That caterpillar seems to me the same one as that of thorn shrubs.”


Rene Antoine Ferchault De Reaumur

Reaumur’s scientific inquiries extended into many fields, including mathematics, geometry, physics, geology, metallurgy, natural history, meteorology, agriculture, and entomology; he is even considered among the first to study of animal behavior.

In 1730, Reaumur invented a thermometer containing diluted alcohol in which 0° Ré was freezing and 80° Ré was water’s boiling point, and our manuscript might be concerned with experiments relating to his thermometer. Although the adoption of the metric system in the 1790s led to its demise in France, Reaumur’s temperature scale remained in use through the next century in other parts of Europe and Russia and it is still used in some industrial food manufacturing.

One of Reaumur’s notable contributions to the field of entomology was his six-volume Mémoires pour servir à l’histoire des insects which included descriptions of all known insects (with the exception of beetles) and detailed plates showing them in various stages of life. The verso of our manuscript details Reaumur’s observations of a caterpillar transforming into a butterfly, a methodical approach which led his friends to dub him the “Pliny of the 18th century.”

Two portions of the text on the verso are crossed out, one with an X and the other with a single diagonal line. Light wear and in overall fine condition. Manuscripts of Reaumur are very rare.

Extremely Rare Reaumur Manuscript on Condensation and the Life Cycle of a Caterpillar

Signed by Rene Antoine Ferchault de Reaumur

$3500 • item #1933

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