100 THE DENILIQTIIN OR BABKATTA METEORITE. 



In some cases the iron sulphides are visibly disseminated 

 throughout the mass in the form of grains ; in others, they exist in 

 such a fine state of division that they can only be detected by the 

 evolution of sulphuretted hydrogen on treating with acids. 



The non-metallic constituents of meteorites are usually crys- 

 talline. This can at once be proA'ed, in such as are transparent, 

 "by the colours which they in thin sections display under the 

 polariscope. 



Amongst the minerals found in them are — 

 Olivine. 



Bronzite or Enstatite. 

 Augite. 

 Anorthite. 

 Labradorite. 

 Calcium sulphide. 



Asmanite, a form of silica crystallizing in the rhombic system. 

 The first two are essentially silicates of magnesium ; augite is a 

 silicate of aluminium and calcium ; anorthite and labradorite 

 are felspars, and in composition are silicates of aluminium, 

 calcium, and sodium. 



But perhaps the most surprising constituents of some few 

 meteorites are peculiar compounds of carbon and hydrogen. 

 Thus, the Bokkeveld meteorite, from Cape Colony, yielded a 

 bituminous and waxy substance to alcohol ; and when heated, it 

 furnished a sublimate containing the readily volatile salt sulphate 

 of ammonium. This meteorite contains, in round numbers, some 

 80 per cent, olivine, about 7 per cent, nickeliferous ii'on, 5'5 per 

 cent, other silicates, and 2 per cent, carbon and bituminous 

 matter. 



About one-third of the known elements have been found in 

 meteorites, as follows : — 



Aluminium, calcium, carbon, chromium, cobalt, copper, iron, 

 magnesium, manganese, nickel, oxygen, phosphorus, potassium, 

 silicon, sulphur, titanium, tin, and probably in some instances 

 antimony, arsenic, chlorine, hydrogen, and lead.. All of them 

 occur in minerals constituting the crust of the earth. 



If we arrange the elements according to their importance or 

 abundance in meteorites, they will take up the following order, 

 thus : — magnesium, then iron, silicon, oxygen, and sulphur ; next 

 will come calcium, aluminium, nickel, phosphorus, carbon, &c., &c. 



I need hardly remind you that but a few years ago. Professor 

 Grraham, of the English Mint, exhibited specimens of hydrogen 

 gas which he had pumped out of a meteorite, and which had been 

 occluded within its pores. 



The nature and constituents of meteorites prove beyond a 

 doubt that they have been formed under conditions which either 

 did not furnish sufficient oxygen to combine with the iron, a 



