Ch. XXVL] HYPOGENE FORMATIONS. 381 



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 sue- 



* See above, p. 107. 



