Vacuum
in physics, a portion of space void of matter. The possibility of the existence of a perfect vacuum has been a favorite subject of discussion among metaphysicians; and that the negative view was popular is indicated by the historical phrase "the vacuum which nature abhors." Descartes asserted that if the contents of a hollow vessel were taken out without anything entering to fill its place the sides of the vessel would be in contact. This assertion, however, is based on the dogma that the only essential property of matter was its VACUUM CLEANER extension; that, in other words, matter was indistinguishable from space. Such inquiries, however, can lead to nothing definite. The experimental phil- VAIL zles and hoses may be attached in different parts of the buildings.