BarLtow—A Mechanical Cause of Homogeneity of Crystals. 667 
of the other assemblage will be squeezed together, and some con- 
siderable disturbance of the symmetrical arrangement of the parts 
will ensue, because the constituents forming the framework 
through being linked together are unable to alter their relative 
situations sufficiently to produce a fresh homogeneous arrange- 
ment; in other words, the symmetry of the framework will have 
to suffer distortion. The general distribution and the general 
outlines of the mass will, however, continue of much the same 
kind and form. 
If the mass before the abstraction of some of the liquid portion 
displays anisotropic properties, the diminution of internal re- 
gularity caused by this change will impair these properties, 
anisotropism requiring uniformity of the conditions at correspond- 
ing points, 7.e., at points which in the unaltered structure have 
similar surroundings similarly orientated. 
With regard to any change in the general form arising 
from the same cause, the maximum distortion will be found at 
the outer boundaries, because there the conditions around a given 
point are least symmetrical owing to the absence of ties in one 
direction ; it will diminish inwards and at the centre will be a 
minimum. 
Again, if before the withdrawal of the removable portion 
parallel layers of the linked portion are found in which none of 
the former is contained, so that these layers are unchanged 
by the process, it is evident that the crushing together will 
almost certainly be less in the direction of these planes than in 
other directions. 
Finally if the portions which have been removed, or portions 
of a similar assemblage, be supplied to a shrunken framework? 
we shall expect the advent of these constituents to restore the 
linked framework to its primitive condition, and therefore rather 
to increase than to diminish the symmetry, and if anisotropism 
is present, to intensify it. 
There is considerable resemblance between the properties thus 
traced and the behaviour of erystalloids. 
1 The way in which the loose particles penetrate the shrunken assemblage is re- 
ferred to in a subsequent section. See p. 682. 
