AN ATTRACTIVE COPY without library markings. Norman states that "Guericke's invention of the air pump grew out of his interest in the nature of space, particularly in Descartes' belief in the equivalence of space and matter and denial of the possibility of vacuum. Guericke suspected otherwise, and, after several false starts, managed to construct a hollow apparatus from which he evacuated the air with a suction pump, thus disproving Descartes' claims and resolving the old controversy between the vacuists and the plenists." The most important result of Guericke's experiments was the discovery of the elasticity of air which led him to investigate the decrease of air density with height, and to relate variations in air pressure to changes in weather.

The folding plate (illustrated above) shows the famous Magdeburg experiment of 1657, when two teams of draught-horses proved unable to pull apart two copper hemispheres filled with a vacuum.