Traitez de l’équilibre des liqueurs, et de la pesanteur de la masse de l’air

12mo of (14) ff., 232 pp., (4) ff. and 2 folding plates.
Contemporary vellum, marginal damp stains and foxing to a few leaves. Contemporary binding.

144 x 85 mm.

Pascal, Blaise. Treatise on the Equilibrium of Liquids, and on the Weight of the Mass of Air. 
Paris, Guillaume Desprez, 1663.

First edition of the foundational treatise on the principles of hydrostatics.
Tchemerzine, V, 59; Dibner Heralds (“The relationship of barometric change and change in the weather was first outlined here”); Sparrow Milestones of Science, 157; Waller, 12161; Norman, 1650; DSB X, 330.
It is decorated with 2 large folding plates illustrating Pascal’s various experiments.

“In 1638, the fountain engineers of the Duke of Florence, having attempted to raise water to more than 32 feet (10.4) using a suction pump, found that the water could not rise above 31 feet. They consulted Galileo. All Aristotelian antiquity had claimed that water ascended in pumps because nature abhors a vacuum. Galileo, though he doubted this assertion, had no answer, and tasked his disciple Torricelli (1608-1647) to investigate the question further. Torricelli had the idea of replacing the water with quicksilver (mercury), which is 14 times denser, and predicted that the liquid would rise much less. The experiment was verified by Viviani in 1643. Torricelli then supposed that it was solely atmospheric pressure that could cause the mercury to rise in the tube.”

These experiments were followed with great interest by Pascal. He recorded his first results in a small book published in 1647, New Experiments Concerning the Vacuum, in which he clearly proved that all the effects previously attributed to the horror of the vacuum were in fact caused by the weight of the air. He faced many critics. For this reason, he decided upon an experiment that would be decisive.

The great experiment on the equilibrium of liquids was carried out at the Puy de Dôme, on September 19, 1643, and entrusted to Florin Périer, Pascal’s brother-in-law. The latter established irrefutably that the height of the mercury suspended in Torricelli’s tube could vary with altitude. It follows, said Pascal, that the weight and pressure of air are the only causes of the suspension of mercury, and not the horror of the vacuum, and that, on the contrary, nature accommodates the vacuum quite easily.

Pascal generalized all these results by formulating the principles of hydrostatics, which he recorded in the Treatise on the Equilibrium of Liquids and on the Weight of the Mass of Air.

This collection was published in 1663, one year after Pascal’s death. The experiments of Pascal and Torricelli had the great merit not only of proving the phenomenon of atmospheric pressure, but also the existence of a vacuum—a vacuum which would go on to play such an important role in modern physics.”

Precious copy preserved in its contemporary vellum.