OF GEOLOGICAL DYNAMICS. 



125 



by the combination of the materials constituting 

 the earth, we may remark first, that the upper 

 crust consists chiefly of metallic oxides, but contains 

 also a large quantity of carbonic acid and water. 

 Now we have the following results, from two very 

 accurate observers, regarding heat of combina- 

 tion reduced so as to show the amount of heat 

 generated per unit mass of the compound substance 

 formed : 



HEAT OK COMBINATION OF VARIOUS ELEMENTS WITH 

 OXYGEN. 



These numbers make it, I think, very certain 

 that the heat of combination per ton of the average 



