Figure 8
One of the first graphic representations of the seven crystal `systems' with their derived `centered' forms (to be read, from the upper left, in alphabetical order: a, b etc.). Together they constitute the 14 `space lattices'. When the various `axes of symmetry' and `mirror planes' are applied to them, there result 32 crystal `classes' (source: Niggli, 1920BB26; the order has been adapted to Bravais' deduction).  [article HTML]