TRAiNSACTIONS OF SECTION G. 729 



It is not easy, however, to define in what condition the mass of iron which must 

 •exist in the heart of the earth is likely to be. Iron is capable of forminnr a vast 

 number of combinations, depending upon the relative proportion of the various 

 elements present. Thus, in the blast-lurnace, oxygen, carbon, nitrogen, calcium, 

 silicon, and iron are associated, and produce, under the action of heat, besides 

 various gases, a carburet of iron and slog, the latter containing chiefly silicon, 

 calcium, and oxygen — that is to say, substances similar to those which form the 

 bulk of the surface of the earth. But these same elements, if there be an excess of 

 oxygen, will not yield any carburet of iron ; and the same result will follow if there 

 be a detieiency of silicon and calcium, because of the large proportion of oxygen 

 ■which they appropriate. In the same way, during the cooling of the earth, if 

 oxygen, carbon, and iron were associated, and if the carbon were in excess of the 

 oxygen, the greater part of the carbon would escape in the gaseous state, while the 

 remaining part would unite with the iron. It is certain that, in the heart of the 

 earth, there must have been a deficiency of oxygen, because of its low specific 

 gravity ; and the argument is supported by the fact that free oxygen and its com- 

 pounds, with the lighter elements, abound on the surface. Further, it must be pre- 

 sumed that much of the ii-on existing at great depths must be covered over and 

 protected from oxygen by a coating of slag ; so that, taking all these considerations 

 into account, it is reasonable to conclude that deep down in the earth there exist 

 large masses of iron in part at least in the metallic state or combined with carbon. 



The above views receive considerable confirmation from the composition of 

 meteoric matter, for it also forms a portion of the solar system, and originated, like 

 the earth, from out of the solar atmosphere. Meteorites are most probably frag- 

 ments of planets, and a large proportion of them include iron in their composition, 

 often as carbides, in the same form as ordinary cast-iron — that is to say, a part of 

 the carbon is free and a part is in chemical union with the iron. It has been shown, 

 besides, that all basalts contain iron, and basalts are nothing more than lavas forced 

 by volcanic eruptions from the heart of the earth to its surface. The same causes 

 may have led to the existence of combinations of carbon with other metals. 



The process of the formation of petroleum seems to be the follomng : It is 

 generally admitted that the crust of the earth is very thin in comparison with the 

 diameter of the latter, and that this crust encloses soft or fluid substances, among 

 ■which the carbides of iron and of other metals find a place. When, in consequence 

 of cooling or some other cause, a fissure takes place through which a mountain range 

 is protruded, the crust of the earth is bent, and at the foot of the hills fissures are 

 formed ; or, at any rate, the continuity of the rocky layers is disturbed, and they 

 are rendered more or less porous, so that surface waters are able to make their way 

 deep into the bowels of the earth, and to reach occasionally the heated deposits of 

 metallic carbides, which may exist either in a separated condition or blended with 

 other matter. Under such circumstances it is easy to see ■vv-hat must take place. 

 Iron, or whatever other metal may be present, forms an oxide with the oxygen of 

 the water ; hydrogen is either set free or combined with the carbon which was 

 a.«sociated with the metal, and becomes a volatile substance — that is, naphtha. The 

 water which had penetrated down to the incandescent mass was changed into steam, 

 a portion of which found its way through the porous substances with which the 

 fissures were filled, and carried with it the vapours of the newly formed hydrocarbons, 

 and this mixture of vapours was condensed wholly or in part as soon as it reached 

 the cooler strata. The chemical composition of the hydrocarbons produced will 

 depend upon the conditions of temperature and pressm'e under which they are 

 formed. It is obvious that these may vary between very ■vs-ide limits, and hence it 

 is that mineral oils, mineral pitch, ozokerit, and similar products difler so greatly 

 from each other in the relative proportions of hydrogen and carbon. I may men- 

 tion that artificial petroleum has been frequently prepared by a process analogous 

 to that described above. 



Such is the theory of the distinguished philosopher, who has framed it not 

 alone upon his wide chemical knowledge, but also upon the practical experience 

 derived from visiting otticially the principal oil-producing districts of Europe and 

 America, from discussing the subject with able men deeply interested in the oil 



