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: 
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Crystalline form and Chemical constitution. 95 
? 
=~ special dimensions of the crystal, yet remains to be ex- 
plain i 
as been more than once implied in the foregoing, that, while, 
according to the principle advanced, tetragonal and hexagonal 
forms depend on the numbers 4 and 8, as explained, the pres- 
ence of these numbers by no means necessitates the occurrence 
of these forms. Multitudes of examples illustrate this: the di- 
morphism of TiO? is one. I would also remark that I express 
No opinion as to whether the molecule of a compound consists 
of the positive and negative atoms simply juxtaposed, or whether 
these so-called atoms are composed of particles, and there is a 
nt disposition in the molecule; and assert only that, what- 
ever the fact on this point, there is tetragonal symmetry in the 
Constitution of the molecule in the tetragonal system, and hex- 
agonal in the hexagonal system. i ; 
I leave the subject here, without discussing at present the 
7 hombic ; 
t, from 
1 (or 2) as in sulphur, upward; and, therefore, although polym- 
erism may turn the 2 Of sulphur (and so, other ccoehaee into 
* See articles I and II referred to on page 89. 
