DIASTROPHISM AND THE FORMATIVE PROCESSES 691 
itself, and only the larger vibrations are in evidence, but if the 
mass grows indefinitely the internal self-stresses increase and there 
appear in succession the shorter and more intense vibrations 
ranging up through the whole gamut of vibrations to the X-rays 
and doubtless beyond. There is, in this, increased pressure, of 
course, but the activity itself is increasingly divergent as well as 
increased in amount. However this may be interpreted, there is a 
growing complexity of vibration, and it seems to bea safe generaliza- 
tion that growing mass and growing internal pressure are attended 
by increase in the diversity of phases assumed by the compressional 
energy; in other words, there are more varied partitionings of the 
energy and it takes a larger number of paths, including more fre- 
quent interchanges between the endothermic and exothermic 
phases. As there is thus crowding in various directions for ease- 
ment, the direction that gives greatest relief from the stress imposed 
by the environment naturally becomes a predominant trend. 
Where there is high pressure and it is unescapable, the line of 
relief is the passage of energy into a constructional form that gives 
additional density. Where the pressure is weak or absent, an 
expansional or dispersive form of energy may be more efficient in 
giving relief. Both forms are likely to be present and to co-operate 
with one another in any pronounced case. 
THE TESTIMONY OF PRESENT INTERNAL STATES AS TO THE DOMINANT 
DIRECTIONS TAKEN BY ENERGY IN THE INTERIOR 
Tidal* and nutational? evidences concur in indicating a higher 
degree of rigidity and elasticity in the interior, taken as a whole, 
than in the outer shell. Seismic waves add very specific confirma- 
tory evidence, so far as the outer seven-eighths of the volume of the 
earth is concerned. The seismic evidence for the remaining central 
part is as yet obscure, and is differently interpreted by the special 
students of the subject. Ina general way, the whole of the interior 
is covered by the tidal and nutational evidences. These favor 
the interpretation of the central part as highly rigid and elastic, since 
t A. A. Michelson and Henry G. Gale, ‘‘The Rigidity of the Earth,” Jour. Geol., 
Vol. XXVII (1919), pp. 585-601. 
2W. Schweydar, “Die Elasticitat der Erde,” Naturwissenschaften, Part 38. 
Potsdam, Germany (1917). 
