Bartow—A Mechanical Cause of Homogeneity of Crystals. 588 
something has already been said.! We shall now consider the 
production of these groups by the simple means postulated at 
the outset of this inquiry, their nature and the effects of their 
presence. 
1. As to their production :— 
Suppose any homogeneous closest-packed assemblage of 
independent balls to pass uniformly into a partially tied state,’ 
or, which will have the same result, suppose such an assemblage, 
after it has experienced a change to the solid state,’ to pass 
partially, but not completely back into the unfettered state; and 
suppose the change to take place wniformly and symmetrically 
throughout the assemblage. Some of the adjacent balls will now be 
linked together, and some will not, and it is manifest that the ties 
subsisting between those which are linked will exhibit a homo- 
geneous! arrangement. For if anywhere two balls become linked, 
or cease to be linked, as the case may be, we shall have a similar 
change occurring in the case of every other similar set the indi- 
vidual balls of which are similarly related. 
Granted then that the process is sufficiently feta for the 
homogeneity of the assemblage, so long as no permanent move- 
ment takes place, to continue unimpaired, two or three distinct 
possibilities present themselves. Thus after the change has taken 
place the assemblage may consist of detached groups all of one 
kind, or of two or more different kinds, as just defined in the 
heading of this section, or it may consist of a single homo- 
geneous network of linked balls, the meshes of which are occupied 
by balls which are not linked to one another, or to those forming 
the network. 
Deferring the consideration of the last-mentioned contingency 
. 
equilibrium. The intermolecular movements which are undoubtedly present, can, as a 
rule, be neglected, for they can be supposed to be periodic about a centre of equilibrium. 
Thus, from a stereochemical standpoint, a molecule can, as a rule, be regarded as a 
statical system of material points whose dynamical properties only need to be taken 
into account under certain conditions, such as change of arrangement.’”’ (‘‘ Grundriss 
der Stereochemie,’’ yon A. Hantzsch, Breslau, 1893, p. 1). Comp. ‘‘ Stéréochimie,”’ par 
van ’t Hoff et Meyerhoffer, Paris, 1892, p. 1. Also see post, note 1, p. 688. 
1 See pages 535 and 556, comp. pp. 609 et seq. 
2 See p. 530. 3 See note 1, p. 530. 
4 Homogeneous according to the definition before referred to. See note 1, p. 531. 
