696 T. C. CHAMBERLIN 
of the shale was due to the mechanical elimination of porosity. 
In forming the schists there was true reorganization with increased 
density, and still later there was further partial reorganization 
into much heavier minerals of the garnetic group. In the case 
of the garnets there is a rise in density from the schist minerals 
which formed them of 36 to 84 per cent, as pointed out by Van Hise.* 
In these cases the rise of density is unequivocally the result of the 
metamorphic reorganization of very common and representative 
kinds of material. It is to be noted further that one reorganization 
follows another even in this limited zone. 
These specific cases show the possibilities and the actual tenden- 
cies to increase of density by metamorphism, quite apart from 
mechanical compacting. They point to the very significant fact 
that the chief density effects are to be sought in metamorphism 
rather than mere mechanical compacting by pressure. The crux 
of the compressional problem therefore lies in metamorphic reorgani- 
zation, in selective liquefaction, and in the extrusion of magmas. 
The concrete task thus imposed is the tracing of the paths followed 
by the compressional energy and the study of the kind of work each 
phase of energy does. The specific phenomena to be explained are 
(1) the rising density, rigidity, and elasticity of the interior material; 
(2) such a distribution of density as to satisfy the intimations of the 
precession of the equinoxes and the nutation of the poles; (3) the 
amounts and kinds of diastrophism recorded in the structure of the 
earth; and (4) the protrusion and persistent maintenance of the 
continents and the complementary depression of the ocean basins, 
as well as the special configurations of the earth. It is not suffi- 
cient to explain these separately by isolated postulates. unless 
these are shown to be mutually compatible and connected with a 
common origin; these features are to be explained as a co-ordinate 
group of phenomena arising from a common origin and a common 
line of dynamic procedure. 
THE SPECIFIC PATHS OF THE COMPRESSIONAL ENERGY 
In the following analysis, it is to be understood that the earth 
is assumed to be, and to have been at all stages after the formation 
™C.R. Van Hise, of. cit., pp. 205 ff. 
