1 
322. VAN HISE—METAMORPHISM OF ROCKS AND ROCK FLOWAGE.: 
which are numerous large fragments. In many of these the matrix is 
completely recrystallized. The fragments, unlike the matrix, show 
important strains, which not infrequently pass to the point of partial 
granulation or recrystallization. 
Indeed, to explain the phenomena in the case of crystalline schists 
which have been developed during a continuous process of deformation 
it does not seem necessary to suppose that complete recrystallization of 
all of the material is necessary. 
If the case of a large grain of quartz or feldspar in a recrystallizing 
rock be taken, we may suppose the process to go on somewhat as fol- 
lows: Because of the lack of homogeneity of the rock the stresses are 
irregularly distributed. At the most exposed places upon the mineral 
particles the conditions are favorable for solution, for the following 
reasons: ‘The particle is. there greatly strained, perhaps to the point of 
granulation, and, so far as strain exists or small granules are formed, 
these conditions are favorable to solution. At the places of great strain - 
the material is therefore taken into solution and transported to the parts 
of the particles less strained. At such places the conditions are favor- 
able to deposition, on account of the relatively large size of the residual 
original grains as compared with the granules. The mineral where least 
strained separates from the solution material like itself, attaching it to 
itself,in orientation with the core in an unstrained or little strained con- 
dition. ‘The process of growth is analogous to that of mineral growth 
by secondary enlargement. The entire process is similar in several re- 
spects to that of the continuous solution and deposition of calcium car- 
bonate in the chemical laboratory when water is passed through a layer 
of this material under pressure. Where the pressure is greatest in the 
upper part, the grains are taken into solution. At the place of escape, 
where the pressure is least, the material is deposited from solution, and 
the grains increase in size or grow. 
During the deformation of the rocks this process of solution and 
deposition of a mineral particle is continuous. 
If it be supposed to go on to a stage in which the original particle is 
one-half or one-third as thick as it was originally, it is not necessary to 
suppose that the central part of the mineral particle has been recrystal- 
lized. This is illustrated by figure 2. The spherical grain is supposed 
to have changed to the superimposed spheroidal grain. The common 
portion C may be an uncrystallized part of the old grain, but the mate- 
rial A A has been dissolved and added to the borders at BB. Corre- 
sponding to this explanation, some of the flat quartz grains of the mica- 
slates and mica-schists of the Black Hills of Dakota show residual 
cores.* 
* Bull. Geol. Soc. Am., cit., p. 224. 
