144 CONSEQUENCES OF CENTRAL HEAT. 



covered oy water, and at others it is covered by a luxuriant vege- 

 tation. 



44. Peat-bogs are numerous in different parts of the world ; 

 they occupy basins or depressions in the soil at different elevations, 

 even in the Alps. One-tenth of the whole surface of Ireland is 

 said to be covered by peat-bog. In the Great Dismal Swamp of 

 Virginia and North Carolina, there is a deposit of peat from ten to 

 fifteen feet in thickness. 



LESSON VIII. 



EXPLANATION OF VARIOUS PHENOMENA. Consequences of Central 

 Heat First effect of cooling Warm Springs Deposits 

 referable to Sediment Fresh-water Deposits Fossils of Ma- 

 rine Deposits Fossils of Carbona'ceous Deposits. 



EFFECTS ATTRIBUTABLE TO UPHEAVAL AND SUBSIDENCE. Shell 

 Deposits and raised Beaches Submarine ForestsTracks of 

 Quadrupeds and Birds Dislocation of Strata Faults Cra- 

 te' 'riform arrangement of Strata Valleys of Elevation Up- 

 heaval without Dislocation Distortion of Strata Origin of 

 Valleys Valleys from Dislocation, from Subsidence, from 

 Folding or Plaiting, from Erosion or Denudation Origin 

 of Caverns. 



Having established the fact of a central heat capable of keeping every, 

 thing in a stale of fusion, at a short distance beneath the surface we inhabit; 

 having shown the actual effects of earthquakes and of volcanic action ; 

 having pointed out those which waters produce, both by denudation, or de- 

 gradation, and the formation of new deposits, it is natural to attempt, by 

 reference to these effects, the explanation of all geological phenomena which 

 have occurred on the surface of the globe from the first moment of its exist, 

 ence. The causes now in action are the same as those which have acted 

 through all time; but doubtlessly they were more energetic at certain epochs 

 than present observation shows. 



1. CONSEQUENCES OF CENTRAL HEAT. The complete fluidity 

 rf the globe gave rise to its ellipsoidal form : the heat so long pre- 

 served, and still existing beneath the cooled pellicle or crust, has 

 ^reduced, and is now producing a great number of phenomena. 

 The temperature of the surface is nearly stationary, and has not 

 varied since the period of records, and will not probably change. 

 But before reaching this state, which probably required thousands 



44. Where are peat-bogs found ? 



1 . What influence is central heat supposed to exercise over the form of 

 the globe? Had the central heat any influence on climate? How do yoa 

 account for the fossils of tropical plants and animals being found in northern 

 leg i MIS ? 



