DIASTROPHISM AND THE FORMATIVE PROCESSES 519 
the great processes that form the earth-habit, but in this set of 
views it is to be assumed that they serve as subordinate elements 
and merely condition the dominance of elastic solidity. 
The development of a system of tenets on the elastico-rigid basis 
is also invited by the grave objections that have arisen from new 
phenomena against the gaseous cosmogony and its sequences which 
lie back of the older system of tenets. The planetesimal cosmogony 
offered to meet these difficulties is founded on orbital mechanics 
and parts company with gaseous mechanics at the outset. Being 
thus dynamically diverse from the start, it has occasion for its own 
set of tenets. These need elaboration to meet the whole range of 
phenomena involved in the major problems of geology. The task 
of working these out has been steadily pursued but the labor is 
great, and progress, if guided by prudence and circumspection, is 
necessarily slow. 
While many of these tenets of course have no immediate concern 
with the physics of the body of the earth and are not necessarily of 
the elastico-rigid order when they do, yet the dominant tendency 
from the nature of the hypotheses is in that direction. The plane- 
tesimal cosmogony opens the way at least for the evolution of an 
elastico-solid earth in the very mode of growth it postulates, though 
it does not exclude the possibility of a molten earth or even the 
probability that molten and gaseous states may dominate planets 
much more massive than the earth. With a body of the mass of the 
earth limited in its power to control the lighter gases, the trend of 
probabilities favors an essentially solid earth from an early stage of 
growth if not from the very beginning. An orbital organization 
may have dominated even the earth-nucleus of the parent nebula. 
At any rate, the long slow growth of the main mass of the planet 
offers rather strong presumption of a relatively cool solid accretion 
attended by heterogeneities of composition and differentiations of 
accession and crystalline organization that were never smoothed out 
by liquefaction but have remained of the same type as those now 
presented by the earth. An elastico-solid state is thus rather a 
matter of direct genesis than of subsequent derivation as is the case 
in the alternative mode of origin. 
Following this hypothesis, therefore, one comes to a mature 
