 Since each of the first three of the regular solids has equilateral faces, it is possible for any fire, air or water corpuscles to come apart in their interactions—they cut or crush each other—and their faces be reconstituted into corpuscles of one of the two other sorts, depending on the numbers of faces of the basic corpuscles involved. For example, two fire corpuscles could be transformed into a single air corpuscle, or one air corpuscle into two fire corpuscles, given that the tetrahedron has four faces and the octahedron eight (other examples are given at 56d6–e7). In this way Timaeus explains the intertransformation that can occur among fire, air and water. On the other hand, while the faces of the cube particles may also come apart, they can only be reconstituted as cubes since they are based on isosceles right-angled triangles; and so earth undergoes no intertransformation with the other  three.[30]  Having established the construction and interaction of the basic particles, Timaeus continues the physical account of the discourse with a series of applications: differences among varieties of each of the primary bodies are explained by differences in the sizes of the constituent particles (some varieties consisting of particles of different sizes), and compounds are distinguished by their combinations of both different sorts and different sizes of particles. These various arrangements explain the perceptible properties possessed by the varieties of primary bodies and their compounds. An object’s particular arrangement of triangles produces a particular kind of “disturbance” or “experience” (pathos) in the perceiving subject, so that the object is perceived as having this or that perceptible property.