244 METALS IN THE ATMOSPHERE. 



high temperatures. Iron is also found in semitranspareiit masses, 

 green, yellow, or pink, mixed with opa(iue l)la('k pai'ticles. These 

 M. Stanislas Meunier believes to have come from tlie debris of ser- 

 pentine minerals — diorite, ainphibolite. serpentine — containing gran- 

 nies of magnetite and always rich in oxidized iron. 



But this terrestrial source of ferruginous dusts can not explain the 

 extraordinary abundance of microscopic particles of iron fonnd in 

 ])olar and alpine snows and in rains collected in open country. The 

 presence of this nickel-bearing iron dust can be explained only as a 

 powder obtained from the surface of meteorites in the ways we have 

 shown. 



Metals otlicr than iron. — It follows, then, that iron is the metal 

 most abundant in the air, and that in every case when its origin is 

 extraterrestrial it is associated in variable proportions with nickel 

 and cobalt ; but there are also other metals in the atmosphere. The 

 analysis of their cinders, as already mentioned, shows that they are 

 composed of some substances soluble in water, others soluble in hydro- 

 chloric acid, and some insoluble. The almost white sediments col- 

 lected in the fields contain about 40 per cent of salts soluble in water, 

 80 per cent of such matter as calcium and magnesium carbonates, 

 oxide of iron, and some insoluble substances like silica and clay, with 

 small quantities of carbon. 



An examination of the dust deposited in the towers of Notre Dame 

 gave ()7 per cent mineral matter. 9 per cent of which was soluble in 

 water, 23 per cent soluble in hydrochloric acid (this decomposing 

 into ().l per cent sesquioxide of iron. Ki per cent calcium carbonate, 

 and 2.1 per cent magnesium carbonate, with traces of aluminum and 

 phosphorus), and 31.3 per cent of matter, principally silica, not solu- 

 ble in the acids. A grayish powder, fine and soft as meal, collected 

 at Boulogne on October 9, 187(), contained in a dry state, besides 9.7 

 per cent of organic substances, 55 per cent of silica, 1.8 per cent alumi- 

 num (with traces of iron), 30.0 per cent calcium carbonate, and 2.5 

 per cent magnesium carbonate. In the ash calcium, aluminum, mag- 

 nesimn, and other metals were also found. 



Besides their two principal compoiienls- iron and nickel — meteor- 

 ites and their debris contain small n ariable quantities of cobalt, man- 

 iranese, chrome, tin, magnesium, and aluminum. Some minerals in 

 particular are contained in these bodies: Schreibersite (phosphide of 

 iron and nickel), magnetite and chrome iron, which is sometimes 

 found in considerable <iuan(iti(>s in tlie foi'm of tiny grains, and 

 minute crystals, together with olivine and otlier silicates. In short, 

 meteorites may l)e arranged in a long series, at one extremity of which 

 are those c()ini)osed chiefly of iron and nickel and at the other chiefly 

 nonmctallic mineral substances, as olivine, enstatite, feldspar, amphi- 



