116 On the Symmetry of Homogeneous Structures. 



Class 5, 



Finally, a parallel to those among the substances which 

 rotate the plane of polarization both when amorphous and 

 when crystalline, in which the circular-polarization, when the 

 latter state prevails, is a specific property of the homogeneous 

 structure, Is afforded by 



Homogeneous structures which contain effective configurations 

 that do not , on the whole, neutralize one another, and some of 

 which are not destroyed when the structure is partitioned sym- 

 metrically and dislocated. 



A careful examination of the various types of enantiomor- 

 phous homogeneous structure reveals the fact that in most 

 of them the presence of effective configurations of any one 

 kind, which are not helical structures, involves the presence 

 in the same structure of other configurations formed of the 

 same particles as those which compose the first-named con- 

 figurations but differently allotted, which configurations, 

 whether very similar or not, are of the opposite hand*. 



In such cises the two kinds of configurations need not. of 

 course, neutralize one another, although probably in many 

 cases they would practically do so. 



However, there are many other types whose parts are not 

 thus balanced, and which certainly will not by any such 

 property be made inactive. 



It is one of these latter which is selected as an illustration. 



In a structure of type 12 f we may suppose that the effective 

 configurations consist of particles so placed as to form Sohncko 

 24- point-sets whose centres A are the cube-centres of a close- 

 packed system of cubes. 



These same particles may tben equally well be regarded 

 as forming 24-point-sets whose centres B occupy all the cube 

 angles, but the two kinds of configuration cannot possibly in 

 this case be supposed to neutralize one another because they 

 are both of the same hand. They must, on the contrary, be 

 expected to reinforce one another. 



Symmetrical partitioning into similar fragments, followed 

 by dislocation, if it leaves one of the two sets of configurations 

 intact, will destroy the other, and thus we may look for 

 different specific rotation in the broken from that in the 

 unbroken structure as the result of such a dislocation. 



Cases are conceivable in which effective configurations of 

 opposite hand are present in a structure, and those destroyed 



* Comp. p. 112. 



t Zeitschr.f. Rnjst. xxiii. p. 21. 



