Bartow—A Mechanical Cause of Homogeneity of Crystals. 598 
Enantiomorphously related groupings — resemblances to optical and 
other stereo-isomerism. 
It is possible for the same balls wnder the same general conditions 
to be formed into groups in different ways. 
1. Thus suppose that two similarly-constituted homogeneous 
assemblages of balls are enantiomorphous to one another and that 
they experience a similar change of state so that corresponding 
similar groups are formed in each, but that the groups in one are 
enantiomorphous to those formed in the other; then suppose that 
disturbance from without breaks up all symmetry in both except 
that of thearrangement of the parts in the groups. 
We then have two fluid assemblages in which all corresponding 
mean distances between the ball centres are identically the same in - 
both, and to most tests the two assemblages will appear indis- 
tinguishable from one another, and indeed destitute of symmetry, 
but since the arrangement of the balls in the groups is not identical but 
enantimorphous in the two assemblages, the latter will differ from one 
another in regard to any property which is affected by this difference of 
arrangement. 
The difference in the grouping of the balls in fluid assemblages 
thus related finds a parallel in the enantiomorphous difference in 
the grouping of the atoms in the molecule which Pasteur, van ’t 
Hoff, le Bel, and others have concluded must, in some shape or 
- other, be present to account for some cases of isomerism, 7. e., those 
cases in which the chemical and physical properties of two carbon 
compounds are entirely alike, with the single exception that they 
exercise an opposite, but otherwise similar influence on a ray of 
plane-polarized light. Thus Pasteur in 1860, refers to the case of 
dextro- and levo-tartaric acid in the following way :—“ Are the 
atoms of the dextro-tartaric acid grouped in such a manner as to 
follow the winding of a right-hand screw, or are they placed at the 
corners of an irregular tetrahedron, or is their disposition such as to 
exhibit some particular kind of unsymmetrical arrangement ? We 
(Bedson and Williams’ translation, p. 87). Compare this writer’s similar observations 
respecting Carboxyl and other groupings, p. 83. (Bedson and Williams’ translation, 
p. 89). See also below, p. 595. 
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