292 MEMOIR ON METEORITES. 



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 sepa- 

 ration 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 meteorites the oxygen is in 

 combination with silicon, magnesium, etc., forming silica, mag- 

 nesia, etc., that combine with small portions of other substances 

 to form the predominant earthy minerals of meteorites. When 

 iron is found in combination with oxygen it is found in its 

 lowest state of oxidation, as in the protoxide of the olivine and 

 chrome iron, and as magnetic oxide. 



Without going further into detail as regards the similarity 

 of composition of meteorites, they will be seen to have as 

 strongly marked points of resemblance as minerals coming 

 from the same mountain — I might almost say from the same 

 mine — and it is not asking much to admit their having a 

 common center of origin, and that, whatever the body from 

 which they originate, it must contain no uncombined oxygen, 

 and, I might even add, none in the form of water. 



What is this center of origin? Physics does not point it 

 out; and although the chemist can not explore the elementary 

 constitution of any of the other great celestial bodies than the 

 earth, he can examine those smaller celestial masses which 

 come to the earth, and from his results stand on a firmer basis 

 for theoretical conclusions. 



Origin oe Meteoric Stones. 



In taking up the theoretical considerations of the origin 

 of meteoric stones, it is of the utmost importance to reflect 

 well before we confound shooting-stars and meteoric stones as 

 all belonging to the same class of bodies — a view entertained 

 by many distinguished observers. It is doubtless owing to the 

 fact of their having been confounded that but little advance 

 has been made in settling upon the origin of these bodies; in 

 fact, owing to this manner of viewing the subject, observers 

 such as Arago, Bissel, Olbers, and others have turned away 



