Porosity.

Porosity. By this term we express the experimental fact that no kind of matter completely fills the space it occupies. On the atomic theory it is obvious that this must be the case if the atoms of matter are spherical, or, indeed, if they have any form save one or two special ones, such as cubes or rhombic dodecahedrons. The Florentine Academicians, in their attempts to compress water, proved the porosity of silver by flattening a sphere of that metal, filled with water and soldered. The water escaped through the silver, and stood in fine drops on its surface. The porosity of liquids is easily shown by mixing alcohol and water. The bulk of the mixture is considerably less than the sum of the bulks of the components.