THE SMITHSONIAN INSTITUTION. 161 



ibove ; a large portion of it consists of the kind of iron already men- 

 tioned, cellular in its character, and the spaces filled up with stony- 

 materials, similar in appearance to those constituting the second class. 



Although there are some instances of bodies of undoubted meteoric 

 origin not properly falling under either of the above heads, still they 

 will be seen, upon close investigation, not to interfere in anyway 

 with the general conclusions that are attempted to be arrived at ; for 

 these constituents, are represented in the stony materials of the second 

 class, from which their only essential difference consists in the ab- 

 sence of metallic particles. 



If we now examine chemically the three classes mentioned, we find 

 them all possessed of certain common characteristics that link them 

 together, and at the same time separate them from everything terres- 

 trial. Take first the metallic masses ; and in very many instances, in 

 some fissure or cavity, exposed by sawing or otherwise, stony mate- 

 rials will frequently be found, and a stony crystal is sometimes ex- 

 posed : now examine the composition of these, and then compare the 

 results with what may be knovfn of the stony meteorites, and in every 

 instance it will agree with some mineral or minerals found in this 

 latter class, as olivine or pyroxene, most commonly the former ; but 

 in no instance is it a mineral not found in the stony meteorites. If 

 these last, in their turn, be examined, differing vastly in their ap- 

 pearance from the metallic meteorites, they will, with but two or 

 three exceptions, be found to contain a malleable metal identical in 

 composition with the metal constituting the metallic meteorites. 



As to the mixed meteorites in which the metallic and stony por- 

 tions seem to be equally distributed, their two elements are but rep- 

 resentatives of the two classes just described. Examined in this way, 

 there will be no difficulty in tracing their connexion. 



There is one mineral v^^hich there is every reason to believe con- 

 stantly accompanies the metallic portions, and which may be regarded 

 as a most peculiar mark of difference between meteorites and terres- 

 trial bodies. It is the mineral Schreibersite, (mentioned in the first 

 part of this lecture,) to which the constant presence of phosphorus in 

 meteoric iron is due. This mineral, as already remarked, has no 

 parallel on the face of the globe, whether we consider its specific or 

 generic character ; there being no such thing as phosphuret of iron 

 and nickel, or any other phosphuret, found among minerals. These 

 facts render the consideration of Schreibersite one of much interest, 

 running, as it probably does, through all meteorites, and forming 

 another point of difference between meteorites and terrestrial objects. 



Another striking similarity in the composition of meteorites is the 

 limited action of oxygen on them. In the case of the purely metallic 

 meteorites we trace an almost total absence of this element. In the 

 stony m^eteorites the oxygen is in combination with silicon, magne- 

 sium, &G., forming silica, magnesia, &c., that combine with small 

 portions of other substances to form the predominant earthy minerals 

 of meteorites ; and when iron is found in combination with oxygen, 

 . it occurs in its lowest state of oxydation, as in the protoxyd of the 

 olivine and chrome iron, and as magnetic oxyd. 



Without coing further into detail as regards tbe similarity of com- 

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