Recherches sur les modifications de l'atmosphere, contenant l'histoire critique du baromètre et du thermomètre [...]

Measuring the Mountain: Deluc on the Summit of the Buet

New edition, the second after the original Geneva edition of 1772, published in Paris in 1784 by the widow Duchesne, in four octavo volumes. Illustrated with six folding plates engraved by G. Dheulland and C. G. Geissler, depicting barometers, thermometers, and various measuring instruments, together with a folding table comparing atmospheric heights calculated according to the formulae of several scientists, including Mariotte, Halley, Cassini, Daniel Bernoulli, and Bouguer.

Contemporary full mottled polished calf. Smooth gilt-decorated spines, tan morocco lettering-pieces, green morocco numbering-pieces, blue marbled edges. Upper headcap of volume I worn away, with the upper joint exposed at the head; loss at the head of volume III. Six corners rubbed, one exposing the board in volume I. Some signs of use, but nevertheless an attractive and internally fresh copy.

From the library of Richard Tremblot, with his engraved bookplate.

A Genevan trained in mathematics by Georges-Louis Le Sage, Jean-André Deluc (1727-1817) devoted a long series of experiments to the study of the atmosphere and, more particularly, to the determination of altitude by means of the barometer. In the Recherches sur les modifications de l’atmosphère, he compares the theories of his predecessors, refines the use of scientific instruments, and seeks to establish a sufficiently reliable method for converting changes in atmospheric pressure into differences of elevation.

This scientific ambition naturally led Deluc beyond the study. From the 1750s onwards he explored the Alps with his brother Guillaume-Antoine; beginning in 1765, the two made several attempts to reach the summit of Mont Buet, then still very rarely climbed. After two unsuccessful attempts, they finally gained the summit on 20 September 1770, carrying their scientific instruments with them.

The ascent was in no sense a sporting undertaking in the modern meaning of the term. For Deluc, the Buet became a genuine high-altitude laboratory: he observed the behaviour of the barometer and thermometer, studied the boiling point of water under reduced atmospheric pressure, and tested his calculations over a difference in elevation great enough to assess their reliability. The instruments illustrated in the plates are therefore not merely objects of theoretical demonstration; they belong to an experimental programme tested directly on the mountain itself.

The account of the ascent gives the Recherches a particular place in the history of Alpine exploration. Sixteen years before the first ascent of Mont Blanc by Balmat and Paccard, Deluc made the climbing of a summit the direct extension of scientific enquiry. High-mountain travel was no longer solely an exercise in curiosity or exploration: it became a method for obtaining observations and measurements impossible to reproduce in the lowlands.

Deluc’s atmospheric research preceded the more systematic formulation of his ideas on the history of the Earth, developed notably from 1778 in his Lettres physiques et morales. Like Saussure a few years later, he thus helped establish the Alps as a privileged field for the combined study of the atmosphere, mountain structure, and the formation of the globe.

In this work, the mountain therefore ceases to be merely a setting and becomes an instrument of knowledge: the six plates describe the apparatus, the tables compare competing calculations, and the ascent of the Buet tests the entire system in the field. The Recherches sur les modifications de l’atmosphère consequently stand among the major texts of the early history of scientific mountaineering, at the moment when climbing a summit also became a way of measuring the world.