THE DENlLIQUIISr OR BAEEATTA METEOEITE. 99 



h. Non-metallic Meteorites or Meteoric Stones. These are mixtures 

 of several minerals, chiefly silicates, such as olivine, felspar, 

 augite, &c. These are also known as aerolites. 



c. Mixed Meteorites. This class includes all those v. hich are 

 mixtures of metallic iron with various silicates. This mixed kind 

 is far more abundant than that containing only earthy matter. 

 They are known also as siderolites. 



Meteoric iron is always mixed with other elements ; nickel is 

 the one most commonly present, and in amounts varying from 1 

 to 15 or 20 per cent. Some cobalt is usually present also, and 

 occasionally manganese, copper, chromium, tin, magnesium, &c. 



Amongst the non-metallic elements we find silicon, carbon, 

 sulphur, and phosphorus. 



The presence of carbon is remarkable, and more especially as it 

 has been proved to exist in two states ; as free carbon or 

 gi'aphite, and also in chemical combination with the iron, just as 

 in cast iron. Meteoric iron emits the same foetid-smelling 

 hydrogen gas when treated with hydrochloric acid as does com- 

 mon pig iron, due in both cases to the hydrogen being contami- 

 nated with traces of some evil-smelling liquid hydro-carbon. 



Most specimens of metallic meteorites when polished and then 

 etched with an acid, show remarkable more or less crystalline 

 markings known as " Widmanstadt's" figures. Berzelius attri- 

 buted the formations of these figures to the presence of an alloy 

 of nickel and iron disseminated through the mass, and this alloy 

 being less soluble in the acid resisted its action more than the 

 iron itself, and thus stood out in relief on the removal of the iron 

 by solution. 



But since certain masses of meteoric iron do not exhibit these 

 figures, although rich in nickel, it has been thought that they 

 owe their origin to a phosphide of iron and nickel (Schreibersite) 

 which forms the major part of the residue which is left on dis- 

 solving the iron in acid. 



Masses of iron found on or a little below the surface of the 

 earth are usually regarded as meteoric when containing nickel, 

 although the actual fall of the specimen may not have been 

 observed. 



The phosphorus present usually exists combined with iron and 

 nickel, forming the mineral Schreibersite, a magnetic steel-gray 

 mineral, of H. 6'5, and with a sp. gr. of 7'2 ; its chemical 

 composition is represented by the formula (FeilSTi)?. 



The suphur also is usually in combination with the iron, either 

 as magnetic pyrites (Fe7S8) or the monosulphide of iron (FeS.), 

 known as Troilite ; both may be present in the same meteorite. 



Troilite is of a brownish colour, while the magnetic pyrites is 

 more of a bronze yellow, brittle, and attracted by the magnet. 



