METEORIC DUST. 9 



in distinguishing it from dust of earthly origin ; but where 

 it falls upon fields of eternal snow and ice (Figs. 3 and 4), 

 far removed from any rock or soil which could produce 

 ordinary dust, it is more easily collected; and, from his 



Fig. 4. VEGETATION IN A DROP OF EVAPORATED SNOW. 



{Magnified 500 times.) 



experience in the Arctic regions, the Professor is of opinion 

 that more than 500,000 tons fall uniformly and steadily 

 over the whole globe in each year. 



Observations, since repeated by the Russian scientists 

 in Central Siberia, have yielded similar results, for the dust 

 is found to be composed in large measure of metallic par- 

 ticles, such as are characteristic of meteorites, though others 



