SIGNIFICANCE OP THE THREEFOLD STATE. 67 



shows that, in the former case, 73,700 calories are evolved, and in the 

 latter 58,300; that is, 3FeO + H 2 O *- Fe 3 O 4 + H 2 + 15,400 calories. As 

 heat is evolved in this process, a rise of temperature would accelerate the 

 reaction in this direction less than the reverse. In other words, the higher 

 the temperature, the more would the formation of ferrous oxide and water 

 be favored as compared with the conditions at lower temperatures. 



Because of this, there is much reason to suppose that, at the depths 

 where lavas originate, hydrogen and oxygen exist combined as water, 

 since up to temperatures of 2000 C., the dissociation of water takes place 

 only to a limited extent. If a state of equilibrium between hydrogen, 

 water, and the iron compounds were established in the heated interior 

 where a magma originated, as soon as it commenced its way upward and 

 began to lose heat the condition of equilibrium would be destroyed. With 

 the falling temperature, the tendency to reestablish equilibrium would 

 favor the formation of that system which was produced with the libera- 

 tion of heat, i. e., magnetic oxide and free hydrogen. In ascending lavas 

 which are losing heat, the tendency, therefore, is to produce hydrogen and 

 magnetite, or ferroso-ferric compounds. This is doubtless an important 

 source for the hydrogen which is so copiously exhaled during a volcanic 

 eruption. At the same time, this process accounts for the widespread 

 occurrence of magnetite in igneous rocks. The considerable deposits of 

 magnetite, formed apparently from magmatic segregation, which are com- 

 mon in various regions, may, perhaps, owe their origin to a combination of 

 causes, in which this equilibrium reaction is an important factor. 



In general, these reversible reactions tend to show that it is but a short 

 step from hydrogen to water, and from carbon dioxide to monoxide, and 

 vice versa, and that all of these must occur within the earth owing to the 

 processes tending toward equilibrium. Whether hydrogen, in a particular 

 case, occurs in the magmas in the free state, or in the form of water-gas, 

 therefore becomes relatively unimportant. Because of this variation of 

 state, the problem becomes more complex and broader in scope. For the 

 most part, these water-gases are to be regarded as truly magmatic, and 

 not derived from surface-waters penetrating to the liquid lavas, as will 

 be brought out later. They are here put forward as essential factors in 

 the evolution of the magmas from the original planetary matter. 



The reactions working towards equilibrium are able to supply hydro- 

 gen and carbon monoxide under conditions favorable to their absorption 

 and retention, even if they were not originally present as occluded gases. 

 The sources of the gases obtained from rocks are so complex that it is 

 difficult to determine how much is to be assigned to each. Because of the 

 penetration of surface-waters containing carbonic acid in solution, through- 

 out the accessible rocks of the earth's exterior, it is likely that, in many 

 cases, the bulk of the gas obtained by heating powders in vacuo has been 

 derived from acquired water and carbonated compounds. But in fresh 

 meteorites, which presumably have not been subjected to action of this 

 sort, occlusion is relatively more important. 



From the constitution of meteorites, some of the principles of early 

 terrestrial evolution may, perhaps, be inferred, though the growth of the 



