580 T. C. CHAMBERLIN 
differentiations were necessarily absent—against the great stress- 
differences involved, is an obdurate problem that now takes on a 
new and definite aspect because of the very considerable depth 
to which the differentiation of specific gravity is found to extend. 
This, however, is not a problem to be discussed here; its solution 
is the task of those who entertain the view of the former fluency 
of the earth. The question is serviceable here by way of giving 
emphasis to the lateral stresses that inevitably exist in a protruding 
continental body due to its own gravity. If the continents were 
instantly converted into a molten condition they would flow at 
once and with violence toward an isostatic state and give a catas- 
trophic illustration of the difference between the present state and 
a complete isostatic state. 
The nature and the intensity of the mie stresses in the con- 
tinental protuberances may be easily visualized by means of an 
analytical picture of the continents and the great basins. Let these 
be assumed to be in isostatic equilibrium in the limited sense of 
the term as commonly used and let the protuberances be divided 
into independent vertical prisms of uniform dimensions. Then, 
if we choose to take the isostatic flotation view, each prism will 
float freely at a height inversely proportionate to its specific gravity, 
assumed to be the present height; or, if we prefer the solid isostatic 
view, each prism exerts the same pressure as each other prism on 
its base at the level of compensation. If the prisms be viewed as 
independent of one another, they must be sustained against the 
tendency to spread and collapse under their own gravity by a 
rigid coherent force acting transversely and equal at each point to 
the gravitative pressure at that point. This pressure is easily 
computed. If for this purpose we take the very conservative reliefs 
of 6,000 feet for the summit swells of the continents and of 12,000 
feet for the bed of the ocean, the relief-difference will be 18,000 
feet. This is not half the extreme actual differences but may 
perhaps fairly represent the continents if they were reduced to 
symmetrical swells. If we assume a specific gravity of 2.7 for con- 
tinental rock, the gravitative pressure of the base of a prism rising 
from the horizon of the ocean bed to the border of the continents 
at sea-level, 12,000 feet, would not be far from 14,000 pounds to 
