242 METALS IN THE ATMOSPHERE. 



tity oi nickel, is not atlarked l)y llic action of air and water, and 

 IS recognizable by its smooth <>"ray tint. 



XordenskitUd concluded from all these facts that a considerable 

 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 appear in the 

 form of polished si)heres. nor in the characteristic globules. The 

 iron floating in our atmosphere often appears in irregular l)lack frag- 

 ments formed by a conjunction of extremeW minute granules gr()ui)e(l 

 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, Xordenskiold found some black 

 grains which when ground in an agate mortar produced bits of metal- 

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

 their center. Evennan demonstrated the presence of octahedrons of 

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

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

 stones which fell in the Ma jo Province of Spain. Plail collected at 

 Padua in 18.'14 contained magnetic grains of both iron and nickel, a 

 circumstance which 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 filings from the surface of 

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

 tained and the corpuscles collected in the atm()si)heri' are very similar. 

 The fragments filed from the black crust adhering to the metal have 

 the form of irregular little coated spheres. The cosmic particles 

 obtained by "X()rdenskir)ld showed a striking resemblance to those 

 extracted with a nuignet from the sediment of French rain. 



All these observations establish the fact that nuich of the ferru- 

 ginous dust found in the atmosphere comes from meteorites. These 

 metallic nuisses hurtling through sjjace are broken into iTagmenls. 

 throwing oif incandescent })articles of metallic iron. The lightest of 

 this debris is carried through the air by atmosphei'ic currents and 

 ("alls to the earth in the form of magnetic oxide of iron, more or less 

 completely fused. The luminous train of shooting stars is due to 

 combustion of these innumerable particles, resembling somewhat the 

 sparks ihi-own oil' by an ii-on ribl)on burning in oxygen. Meteorites, 

 as everyone has noticed, often have luminous trains, which are to be 

 attributed to the incandescent debris detached from the mass. 



Thus it \ppears that I'errugiiions powder of extraterrestrial origin 

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

 dust comes from planetary space. As Daubree has l)rought out in 



