Figure 6 . Tetrachloroplatinum can be represented as a C 4 C 4 C 4 C 4 figure. Figure 7 . A C 4 C 4 C 4 C 4 figure is tessellated to show the symmetry of the PtCl 4 molecule. These results serve simultaneously to illustrate tessellation symmetries and three-dimensional molecular symmetries.
Some analogies are more obvious than others, and further examples are possible.
A future paper will discuss these in relation to the symmetries of frieze border patterns. Another reason is hydrogen-bonding, which is outside of the focus of this paper. Consult any introductory chemistry text. Reprinted as Fantasy and Symmetry , 1976. I, N. F. M. Henry and K. Lonsdale, eds., Kynoch Press, Birmingham, England, 1952.