Plate 2 from Nova Reperta
by Johannes Stradanus

Boyle's Air Pump


Robert Boyle was a central figure in the investigations of the natural world by means of experimentation that were carried out by the members of the Royal Society and other experimental philosophers in England and elsewhere in the seventeenth century. Boyle already had a long-standing interest in pneumatics when he read of the experiments (carried out in 1644) by Evangelista Torricelli (1608-1647) and Vincenzo Viviani (1622-1703) that effectively created a barometer. They had filled a tube with mercury, closed it at the end, and inverted it into a dish of mercury, whereupon the column sank to about 760 millimeters above the dish, leaving an empty space in the tube above the mercury. Torricelli concluded that his instrument might be used to measure atmospheric pressure. The experiment was of great philosophical interest because it seemed to disprove the Aristotelian dictum that "nature abhors a vacuum."

Boyle heard of these experiments by the early 1650s and Click Here for a Larger Viewrepeated them. He then attempted to create a variation of the apparatus that would allow the introduction of larger objects into the empty space, and thus allow further investigation of the nature of air. He was aided again by hearing of experiments carried out in 1647 by the mayor of Magdeburg, Otto Guericke. Guericke built an air suction pump with a cylinder, a piston, and two flap valves. Boyle set for his assistant Robert Hooke (1635-1703) the problem of creating an air pump that was suitable for carrying out experiments concerning the nature of air. The image that appears in Boyle's treatise, New Experiments Physico-Mechanical Touching the Spring of the Air, displays the apparatus that Hooke devised and that was used for the numerous experiments described in the treatise.

Boyle provides a complete description of the apparatus, which included two main parts: the glass vessel and a pump to draw the air out. He labels and describes each part, including an account of the way in which it was constructed and the materials with which it was made. These details contribute to the immediacy of the descriptions of the experiments. They suggest that Boyle is not referring to Aristotelian common experience (agreed upon by everyone) but rather to particular experiments, carried out at a particular time by specific experimenters, watched by reliable witnesses, and using a specific, complex apparatus.

Boyle's phrase, the "spring of the air," points to a major focus of the experiments, the capacity of the air to exert pressure and to expand. Boyle was cautious about overdrawing his conclusions. For example, he did not claim that the air pump created a true vacuum, that is, that the space became truly empty. Rather, he referred to the removal of "ordinary air," leaving open whether or not the operational vacuum was a true one. This refusal was part of his methodology in which he claimed to be dealing only in "facts" rather than hypothesis and theory.

By the end of the seventeenth century, the principle that the atmosphere was a fluid possessing weight and that its pressure could be excluded from the interior of a closed vessel so as to obtain a vacuum was incorporated into the construction of the first steam engines, the technology that came eventually to define the course of the Industrial Revolution.

Pamela O. Long
Washington, DC

Harry Kitsikopoulos
New York University

Suggested Reading

Boyle, Robert. The Works of Robert Boyle. Vol. 1, Experiments Physico-Mechanical touching the Spring and Weight of Air. Edited by Michael Hunter and Edward Davis. Brookfield, Vermont: Pickering and Chatto, 1999-2000.

Dear, Peter. Discipline and Experience: The Mathematical Way in the Scientific Revolution. Chicago: University of Chicago Press, 1995.

Dear, Peter. Revolutionizing the Sciences: European Knowledge and Its Ambitions, 1500-1700. Princeton: Princeton University Press, 2001.

Frank, Robert G. Harvey and the Oxford Physiologists: Scientific Ideas and Social Interaction. Berkeley: University of California Press, 1980.

Shapin, Steven, and Simon Schaffer. Leviathan and the Air-pump: Hobbes, Boyle, and the Experimental Life. Princeton: Princeton University Press, 1985.