578 T. C. CHAMBERLIN 
whereas great sea-transgressions and great terranes of parallel 
sediments require either a movement that retains the parallelism 
of the sea-surface and the sea-bottom, or else the essential absence 
of any movement at all. A constant upwarping of the land inevita- 
bly defeats extensive sea-transgression and its consequent terranes. 
In further pursuing the conditions that favor or oppose great 
sea-transgression and the formation of the great parallel terranes 
of marine strata, we have now to consider the unbalanced stresses 
that inevitably arise within the continents as a consequence of 
their own protrusions. These are to be distinguished from the 
internal stresses of a more general nature that are usually regarded 
as the cause of orogenic and epeirogenic movements which are here 
covered by the phrase, ordinary diastrophism. ‘The stresses that 
arise within the continents simply because they protrude above the 
ocean beds are of a much more special and limited class. These 
stresses depend simply on gravity acting on the protruding matter 
as such without regard to other conditions; they are strictly 
inevitable and in the main independent. If the base on which the 
continents rest were absolutely inflexible, lateral stresses would 
arise within the continents from their gravitative pressures on their 
own masses, just as such stresses arise in continental glaciers and 
actuate them. If, on the other hand, the continents floated on a 
molten interior, or were in any other way kept in a continuous 
state of isostatic adjustment—in the usual sense of isostasy in which 
each column equals every other column in radial pressure—there_ 
would still arise within the protuberances unbalanced Jateral 
stresses in proportion to the degree of protrusion. 
It is perhaps necessary to remark here for the sake of complete 
clearness that isostasy, in the most complete and unlimited sense 
of the term, involves equal pressures in all directions, not merely 
equal pressures in vertical directions. Equal pressures in all 
directions are predicable only of perfect fluids. In this radical 
sense, the earth cannot be in complete isostatic adjustment at the 
present time because of its inequalities of surface and because 
of the differences in the lateral distribution of specific gravity 
in its crust, even if every vertical column balances every other 
vertical column perfectly. If the earth were ever in a complete 
