690 TI. C. CHAMBERLIN 
range of the accessible terranes, that while exothermic reactions 
preponderate in the outer or katamorphic zone, the preponderance 
is reversed below and endothermic reactions take precedence in 
the anamorphic zone. It is to be noted that while katamorphic 
action, exothermic action, and the lowering of density, commonly 
go together, as also anamorphic action, endothermic action, and 
rise of density, they do not invariably coincide; and further, that 
none of these necessarily excludes the others from any horizon. 
The essential question is not one of exclusive action but of pre- 
ponderant action.’ It is in the natural order of things that in the 
great contact zones between the atmosphere, the hydrosphere, 
and the lithosphere, there should be a trend of energy toward its 
agitative phases, and that in the stabler solid zones below there 
should be a compensating trend toward the constructional and the 
persistent, without limiting either zone to one type of action. In 
terms of the two basal types of energy, exothermic action, on the 
average, involves a change of organizing or revolutional energy 
into vibratory-dissipative energy; while endothermic action is 
commonly the reverse. 
THE CONDITIONS THAT DETERMINE THE INTERCHANGES 
In a very broad sense, open conditions and freedom from 
pressure or other forms of restraint, favor exothermal reactions, 
while confinement and pressure favor endothermal reactions. 
Any form of crowding, even self-stress, naturally tends toward 
divergence of energy into the various paths available to it, since 
this affords relief. ‘The higher the stress, the more it forces itself 
into unoccupied paths. Concentrative stress, therefore, favors the 
passage of a portion of the energy along endothermic lines and the 
formation of dense substances; while dispersive stress, low stress, 
and no stress, are less compulsory and give exothermic action freer 
scope. Apparently crowding is not confined to imposed stresses, 
but arises from what may be styled the self-stress of the activity. 
A small mass of gas in open space exerts little interior stress upon 
tCompare C. K. Leith, “‘The Structural Failure of the Lithosphere,” Vice- 
Presidential Address, Geol. Soc. Amer., Science, N.S., Vol. LIII (March 6, 1921), 
pp. 205-7. 
