DIASTROPHISM AND THE FORMATIVE PROCESSES 699 
united action. This apparently went so far in some cases as to 
verge toward general simultaneous molecular action, but analysis 
seems to show that it remained idiomolecular in actual method. 
From such quasi-collective but really idiomolecular action, cleav- 
age, schistosity, and other forms of structural parallelism arose. 
In glaciers this idiomolecular type of action seems to range from 
snow granulation to the point where fracture takes place and the 
movement becomes a massive shear.* 
By further increases of pressure, the strain limit along selected 
lines was reached and definite fracture and shear took place, or 
else the whole mass was crushed to fragments. In either of these 
cases, the action became diastrophic rather than metamorphic. 
It has been very generally held that when such depths and 
pressures are reached as to inhibit fracture, general movement of 
the molecules over one another after the manner of liquids must 
take place. The original idea of “rock flow” seems to have 
sprung from this notion. In a highly rigid body, such a general 
movement of molecules upon one another requires the breakage of 
all the bonds between molecule and molecule and so involves a 
maximum of force. Moreover, this force must come from dzffer- 
ential stress, since balanced stress, within limits, forces the mole- 
cules into closer and stronger relations. The supposed “‘flow”’ 
seems improbable except when true liquidity, which destroys the 
special rigid bonds of the solid state, is brought about. So far 
as differential stresses affect the solid matter of the interior, ease- 
ment by idiomorphic action, either collective or isolated, seems to 
require much less energy and is hence more probable. With the 
open structure now assigned matter, and with the abundant evi- 
dence that molecules really collect into crystals in the midst of 
rock that seems quite solid, and with other phenomena giving 
evidence that in some way molecules creep through solid matter, 
there seems no substantial ground for excluding idiomolecular 
action from the deep interior. 
t Tt was from the study of the granulation of snow, the growth of glacial granules, 
and the development of schistosity in the glaciers of Greenland, in 1894, that the 
method and importance of this individual action of molecules, while the mass remained 
solid, was first realized by the writer. ‘‘Glacial Studies in Greenland,” Presidential 
Address, Geol. Soc. Amer., Vol. VI (1895), pp. 209-14. 
