242 METALS IN THE ATMOSPHERE. 



tity of iiickcl. is not attacked by the action of air and water, and 

 ]s recognizable by its smooth gray tint. 



Nordenskiold concluded from all these facts that a considej'uble 

 number of aerolites constantly enter our atmosphere and are there 

 broken up, thus giving an extraterrestrial origin to the magnetic 

 corpuscles of the air. 



The little meteoric particles do not, however, always ai)pear in the 

 form of polished spheres, nor in the characteristic globules. The 

 iron floating in our atmosphere often appears in irregular black frag- 

 ments formed by a conjuncticm of extremely minute granules grouped 

 in compact masses sometimes with a rough and irregular surface. 



The study of hailstones has led to the same conclusions as that of 

 snow. In a hailstorm at Stockholm, Nordenskiold found some black 

 grains which when ground in an agate mortar i^roduced bits of metal- 

 lic iron. In another case the hailstones had a metallic nucleus in 

 their center. P^verman demonstrated the presence of octahedrons of 

 iron sulphate in some hail from the Prussian province of Oremlwurg, 

 and Pictet recognized the presence of iron in the nucleus of hail- 

 stones which fell in the Majo Province of Spain. Hail collected at 

 Padua in 1834 contained magnetic grains of both iron and nickel, a 

 circumstance Avhich connects them with the aerolites, since a combi- 

 nation of iron and nickel is a characteristic constituent of meteoric 

 iron. 



The apparent planetary origin of these aerial magnetic particles 

 may best be verified by a comparison with lilings froni the surface of 

 actual aerolites. Experiment has shown that the powder thus ob- 

 tained and the corpuscles collected in the atmosphere are very similar. 

 The fragments filed from the l)lack crust adhering to the metal have 

 the form of irregular little coated s])heres. The cosmic particles 

 obtained by NordenskicUd showed a striking resemblance to those 

 extracted with a magnet from the sediment of French rain. 



All these observations establish the fact that much of the feri'u- 

 ginous dust found in the atmosphere comes from meteorites. These 

 metallic masses hurtling through space are broken into fi-agments, 

 t blowing off incandescent particles of metallic iron. The lightest of 

 tiiis <k''bris is carried through the air by atmospheric currents and 

 falls to the earth in the form of magnetic oxide of iron, more or less 

 com})letely fused. Tlie Inminons train of shooting stars is due to 

 combustion of these innnmei-abU> particles, resembling somewhat the 

 sparks thrown off by an iron ribbon burning in oxygen. Meteorites, 

 !'.s e\('r\()ne has ii()tice(l. often ha\'e himinous trains, which are to be 

 atlril)uted to the incandescent debris detached from the mass. 



Thus it ippears that ferruginous j)ow(ler of extraterrestrial origin 

 is falling constantly to the earth and that a part of the atmospheric 

 dust comes from planetary space. As Daubree has brought out in 



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