Ch. XXVI.] 
I-IYPOGENE FORMATIONS. 
3S1 
surface ; or, in other words, it must depend on the quantity of 
aqueous action which takes place between two periods, that 
when the heated and melted rocks are cooled and consolidated 
in the nether regions, and that when the same emerge to the 
day. 
Volume of hypogene rocks supposed to have been formed 
since the Eocene period. — If we were to indulge in speculations 
on the probable quantity of hypogene formations,, both strati- 
fied and unstratified, which may have been formed beneath 
Europe and the European seas since the commencement of the 
Eocene period, we should conjecture, that the mass has equalled, 
if not exceeded in volume, the entire European continents. The 
grounds of this opinion will be understood by reference to what 
we have said of the causes which may have upheaved part of 
Sicily to a great height above the level of the sea since the begin- 
ning of the Newer Pliocene period*. If the theory which, in 
that instance, attributes the disturbance and upheaving of the 
superficial strata to the action of subterranean heat be deemed 
admissible, the same argument will apply with no less force to 
every other district, elevated or depressed, since the com- 
mencement of the tertiary period. 
But we have shown, in our remarks on the map of Europe, 
in the second volume, that the conversion of sea into land, since 
the Eocene period, embraces an area equal to the greater 
part of Europe, and even those tracts which had in part emerged 
before the Eocene era, such as the Alps, Apennines, and other 
mountain-chains, have risen to the additional altitude of from 
1000 to 4000 feet since that era. We have also stated the 
probability of a great amount of subsidence and the conversion 
of considerable portions of European land into sea during the 
same period — changes which may also be supposed to arise from 
the influence of subterranean heat. 
From these premises we conclude., that the liquefaction and 
alteration of rocks by the operation of volcanic heat at suc- 
* See above, p. 107. 
