310 VAN HISE—METAMORPHISM OF ROCKS AND ROCK FLOWAGE. 
of the rocks metamorphosed by metasomatic change, without mass dy- 
namic action, contain as high or higher percentages of water than the soils 
and clays the water contents of which have been quoted. If later such 
hydrated rocks, whether of igneous or aqueous origin, were subjected to 
mass dynamic action, under proper conditions, recrystallized schists 
might be developed. 
The foregoing facts seem to show that whether granulation or recrys- 
tallization occurs in a given district in rocks of a certain chemical com- 
position does not depend upon whether the rocks are igneous or aqueous, 
but, other things being equal, upon whether sufficient water is present, by 
means of which recrystallization may occur. As this is more frequently 
the state of affairs in the sedimentary rocks than in the igneous rocks, it 
follows that the sedimentary rocks are more frequently recrystallized 
than the igneous rocks, though in many instances recrystallization rather 
than granulation has been the process of modification for the igneous 
rocks. 
The experimental work of Adams and Nicholson * upon the deforma- 
tion of marble is fully confirmatory of the above conclusions in reference 
to the influence which water so frequently has in determining whether 
granulation or recrystallization occurs. Thus far their experiments have 
been performed without the presence of water, and granulation has been 
the natural result. Particles were subjected to sufficient pressure to 
bring them close enough to one another to be within the sphere of mo- 
lecular attraction, and adhesion or welding was the result—a result 
easily obtained with the soft metals, but requiring great pressure in the 
case of brittle substances, such as calcite. Adams now proposes to make 
similar experiments with the presence of water. When these are per- 
formed, if under proper conditions, it may be anticipated that recrystal- 
lization, instead of granulation, to some extent at least, will take place. 
Temperature.—Low temperature is favorable to granulation ; high 
temperature is favorable to recrystallization. The temperature of 180° C. 
is more nearly crucial between the processes than any other. Below 
180° C. granulation is likely to be prevalent, especially if the deformation 
israpid. Above 180° C. recrystallization is so rapid that the mechanical 
strains probably do not go far before they are largely obliterated by 
recrystallization. 
Temperature increases with depth; therefore the less the depth, the 
greater the tendency to deformation by granulation; the greater the 
depth, the greater the tendency for recrystallization. Since 180° C. is a 
* Experiments on the flow of rocks now being made at McGill University, by Frank D. Adams 
and John T. Nicholson: A paper presented to the Geol. Soc. Am., Montreal meeting, 1897. (Sum- 
mary in Science, vol. vii, 1898, pp. 82, 83.) 
