The interlaced Tetrahedrons suggest the origin of the plane symbol--the interlaced triangles; but the full beauty of the symbol does not appear until we notice that the axis of symmetry of the Tetrahedrons coincides with the diagonal of the Cube, and that the orthographic projection of all these on a plane perpendicular to the diagonal gives a perfect hexagon with the interlaced triangles in the center. The interlaced Tetrahedrons--one a reflection of the other--in fact define the eight corners of the Cube. The Tetrahedron is "3," and the Cube is "4" (or 6). So we see one way in which the "three fall into the four," and why it is a septenary, and a decad, as well as a three, or a four, according to the various aspects and interrelations considered of the electric, rotary, magnetic, or vibratory forces symbolized by the various lines. Science has already reached the speculation that the hypothetical carbon "atom" has a tetrahedronal form. Let us look at this Tetrahedron with the eye opposite the middle of an edge and in line with the center. The two opposite edges now form the Cross, composed of two equal lines, but separated by a space. One is reminded of an electric wire, and a magnetized needle placing itself at right angles to, although at some distance from, the current in the wire. Thus the opposite edges, whether as rotational vectors or in some other way, indicate a connexion with the dual forces of attraction and repulsion. The Tetrahedron, a triangular pyramid, may be a Fire-symbol. In any case the following passage is suggestive: When the molecules of salt, clustering together, begin to deposit themselves as a solid, the first shape they assume is that of triangles, of small pyramids and cones. It is the figure of _fire_, whence the word "_pyramids_"; while the second geometrical figure in _manifested_ nature is a square or a cube, 4 and 6; for, "the particles of earth being cubical, those of fire are pyramidal" truly--(Enfield). The pyramidal shape is that assumed by the pines--the most primitive tree after the fern period. Thus the two opposites in cosmic nature--fire and water, heat and cold--begin their metrographical manifestations, one by a trimetric, the other by a hexagonal system. For the stellate crystals of snow, viewed under a microscope, are all and each of them a double or treble six-pointed star, with a central nucleus, like a miniature star within the larger one. (_The Secret Doctrine_, II, 594.) The number Five penetrates the whole system of the Five solids in a remarkable way. Thus there are 24 pentagons visible, and by joining other corners of the Dodecahedron, Five Cubes are seen, which of course produce Five Octahedrons, and twice that number of principal interlaced Tetrahedrons. Five has been said to be the Number of Life.