MEANING OF ROCK FLOWAGE. 5) 
granolitic textured rock, the individuals wholly lacking orientation, is 
illustrated by the quartzites of the Wausau district of central Wisconsin. 
In the process of recrystallization of rocks it is not supposed that every 
large mineral particle retains a nucleus for lateral growth ; indeed, it is 
certain that some particles of a mineral may retain the modified integ- 
rity above described in a rock in which other particles of the mineral 
may be wholly destroyed. Whtleas yet it has not been fully worked out, 
it is believed that orientation of the mineral particles in reference to the 
varying stresses may have an influence upon their preservation. If the 
original particles happen to be in such positions as they would develop 
as authigenic minerals under the differential stresses, this is believed to 
be favorable to the preservation of their nuclei and to lateral growth. In 
proportion as the orientation of the particles is removed from such posi- 
tions, it is believed that the mineral particles are likely to be destroyed. 
The effect of orientation with reference to the principal stresses upon 
the persistence of a given particle is probably great in proportion as the 
mineral has a tendency to be influenced in its crystallographic orienta- 
tion by the stress differences which exist during deformation. To illus- 
trate: The position of the crystallographic axes in reference to the 
ereatest pressure in mica and feldspar, which show a marked tendency 
to similar orientation, would be a more important factor in their preser- 
vation than in quartz, which only rarely shows similar orientation.* 
In the foregoing non-rotational distortion has beenassumed. In case 
the deformation includes a rotational element, there would be no dis- 
coverable difference in the crystalline schist produced; > but during the 
deformation and recrystallization each of the particles would be similarly 
rotated, as well as flattened or recrystallized, or both, and consequently 
the direction of shortening and elongation might momentarily change. 
Of course, in proportion as the conditions are unfavorable for recrys- 
tallization—that is, as mineral particlés are refractory, as they are coarse- 
grained, as the deformation is slight but rapid, as the depth is little, as 
the temperature is low, as the water content is small—residual strain or 
mechanical granulation will occur instead of recrystallization. This is 
sufficiently evident without further explanation, from the discussion 
already given (see pages 305-312). 
It is therefore concluded from the foregoing that rock flowage, as deep 
as observation extends, is plastic deformation through continuous solu- 
tion and deposition, or, in other words, recrystallization. During the 
adjustment all or only a part of the material nay have passed through 
this change. However, if a matrix, plastic by recrystallization, be filled 
with rigid granules which are not recrystallized, the whole mass may be 
* Principles, cit., p. 635. 
{ Ibid., p. 638. 
XLVIII—Butu. Gron. Soc. Am., Vou. 9, 1897. 
