Boyle, who heard of von Guericke’s experiments via Schott, retained Robert Hooke to construct a similar air pump for him. Boyle’s experiments supported his “corpuscular” view of matter, that air is comprised of particles in motion. For Boyle, air behaves as if it were made of springs, increasing in pressure as they are reduced in volume. The 2d ed. expressed succinctly what we now know as Boyle’s law: “...the Hypothesis, that supposes the pressures and expansions to be in reciprocal proportion” (1662). Boyle, a central figure in 17th-century chemistry, championed an experimental methodology in service of the mechanical philosophy.