EFFECTS REFERRED TO THEIR CAUSES. 843 



XI. Igneous Action. Earthquakes. 



Pages, 722, 804. 



XII. Change of Temperature. Sources of Heat. 



1. Transformation of motion into heat. — 1. By movements in strata; 

 an important source in metamorphism, pp. 719, 762, 822. 



2. By means of movements in water or air, as in the breaking of waves on a rocky 

 coast; very feeble in its action, if at all appreciable, unless in warming slightly the 

 atmosphere. 



2. The Earth's interior heat.— 1. Through escape outward from the earth's 

 interior, p. 716. 



2. Through convection upward into strata, or " a rise of the isogeothermals," in 

 consequence of the accumulation of sedimentary beds at surface, pp. 718, 762, 820. 



3. Through convection from masses or dikes of fused rock into the adjoining rocks- 



3. Chemical change, p- 719. 



4. The Sun, p. T14. 



XIII. Secular Variations in Climate. 



1. Through change in amount of heat given out by the sun, p. 716. 



2. Through the escape outward of the earth's interior heat, p. 718. 



3. Through a secular change in the density of the atmosphere, that is, in the amount 

 of carbonic acid, moisture, etc., pp. 353, 716. 



4. Through changes in the amount, position, and height of lands over the earth, 

 pp. 44, 541. 



5. Through changes in the courses of oceanic currents, pp. 541, 712. 



6. Through variations in the eccentricity of the earth's orbit, p. 714. 



XIV. Origin of Continents and Oceanic Basins. 



Page 797. 



XV. Extinction of Species. 



The ordinary effects of nearly all the following causes of extinction are simply 

 destruction of life. But they may also occasion extinction of species. 



I. Catastrophic Causes, not Climatal. 



1. Through the emergence of a region, with its aquatic life. 



2. Through the submergence of a region, with its terrestrial life. 



3. Through a change in the level of wave action, or in the relations of a sea to 

 currents, these bearing detritus or not. 



4. Through a change of salt-water seas or lagoons to fresh-water, and the reverse, 

 p. 610. 



5. Through the partial or complete evaporation of salt-water seas or lagoons. 



6. Through earthquake-waves. 



7. Through the heating of the ocean's waters by means of extensive igneous erup- 

 tions, or through the flooding of the land by such eruptions; effectual for volcanic 

 islands, but hardly for wide continental or oceanic areas. 



II. Climatal Causes. 



8. Through the change of level of an emerged region, changing its climate as to its 

 range of temperature, moisture, etc., or as to the excesses of that range. 



