PERMANENCE OE CONTINENTS AND OCEANS. 117 
tion of dry land. We may appeal also to fresli-water forma¬ 
tions, such as the Purbeck and Wealden, to prove that in the 
Oolitic and N^eocomian eras there were rivers draining an¬ 
cient lands in Europe in times when we know that other 
S23aces, now above water, were submerged. 
How far the Transfer of Sediment from the Land to a 
neighboring Sea-bottom may affect Subterranean Movements. 
—Little as we understand at present the laws which govern 
the distribution of volcanic heat in the interior and crust of 
the globe, by which mountain chains, high table-lands, and 
the abysses of the ocean are formed, it seems clear that this 
heat is the prime mover on which all the grander features in 
the external configuration of the planet depend. 
It has been suggested that the stripping off by denuda¬ 
tion of dense masses from one part of a continent and the 
delivery of the same into the bed of the ocean must have a 
decided effect in causing changes of temperature in the 
earth’s crust below, or, in other words, in causing the subter¬ 
ranean isothermals to shift their position. If this be so, one 
part of the crust may be made to rise, and another to sink, 
by the expansion and contraction of the rocks, of which the 
temperature is altered. 
I can not, at present, discuss this subject, of which I have 
treated more fully elsewhere,* but may state here that I be¬ 
lieve this transfer of sediment to play a very subordinate 
part in modifying those movements on which the configura¬ 
tion of the earth’s crust depends. In order that strata of 
shallow-water origin should be able to attain a thickness of 
several thousand feet, and so come to exert a considerable 
downward pressure, there must have been first some inde¬ 
pendent and antecedent causes at work which have given 
rise to the incipient shallow receptacle in which the sediment 
began to accumulate. The same causes there continuing to 
depress the sea-bottom, room would be made for fresh ac¬ 
cessions of sediment, and it would only be by a long repe¬ 
tition of the depositing process that the new matter could 
acquire weight enough to affect the temperature of the rocks 
far below, so as to increase or diminish their volume. 
Permanence of Continental and Oceanic Areas. — If the 
thickness of more than 40,000 feet of sedimentary strata be¬ 
fore alluded to in the Appalachians proves a preponderance 
of downward movements in Palaeozoic times in a district 
now forming the eastern border of North America, it also 
proves, as before hinted, the continued existence and waste 
of some neighboring continent, probably formed of Lauren- 
* Principles, vol. ii., p. 229. 1868. 
