In 1760, Saussure made the first of numerous trips to Chamonix valley, to collect plant specimens for the noted Swiss anatomist, physiologist and botanist Albrecht von Haller.

[9] Although a patrician, Saussure held liberal views, which induced him to present in 1774 a plan for the development of scientific education in the Geneva College, which would be open to all citizens, but this attempt failed.

Two Chamonix men, Michel Paccard and Jacques Balmat, attained the summit in 1786, by way of the Grands Mulets, and in 1787 Saussure himself made the third ascent of the mountain.

In 1789, Saussure climbed the Pizzo Bianco near Macugnaga, to observe the east wall of Monte Rosa, and crossed the Theodulpass (3,322 m) to Zermatt, as the first traveler to visit.

[6] Of particular importance was a hair hygrometer that he devised and used for a series of investigations on atmospheric humidity, evaporation, clouds, fogs and rain (Essais sur l'Hygrométrie, 1783).

[12] In 1767, Saussure constructed the first known Western solar oven, trying several designs before determining that a well-insulated box with three layers of glass to trap outgoing thermal radiation produced the most heat.

His geological observations made him a firm believer in the Neptunian theory: He regarded all rocks and minerals as deposited from aqueous solution or suspension, and attached much importance to the study of meteorological conditions.

[6] His work with rocks, erosion, and fossils also led him to believe that the earth was much older than generally thought and formed part of the basis of Darwin's Theory of Evolution.

[16] Saussure carried barometers and boiling-point thermometers to the summits of the highest mountains, and estimated the relative humidity of the atmosphere at different heights, its temperature, the strength of solar radiation, the composition of air and its transparency.

[6] Saussure adapted the thermometer to many purposes: for ascertaining the temperature of the air he used one with a fine bulb hung in the shade or whirled by a string, the latter form being converted into an evaporimeter by inserting its bulb into a piece of wet sponge and making it revolve in a circle of known radius, at a known rate; for experiments on the earth and in deep water he employed large thermometers wrapped in non-conducting coatings so as to render them extremely sluggish, and capable of long retaining the temperature once they had attained it.

He was an early user of the term "geology"—see the "Discours préliminaire" to volume I of his Voyages,[6] published in 1779—though by no means its inventor as some have claimed, the English word having been used in the 1680s and its Latin counterpart "geologia" during the previous several centuries.

[21] The genus of plants Saussurea, some adapted to growing in extreme high-alpine climates, is named after him and his plant-physiologist son Nicolas-Théodore de Saussure.