96 SCIENCE OF COMMON THINGS. 



Meteoric iron. Origin of meteors. Shooting stars. 



619 Do tJie aerolites resemUe in composition any other bodies upon the 

 surface of the earth f 



They do not : malleable iron is rarely if ever found 

 in terrestrial substances / and metallic nickel does not 

 occur upon the surface of the earth naturally. 



620 What is peculiar to the composition of meteoric iron t 



It has a highly crystalline arrangement, so peculiar 

 that it is especially distinguished by it. This arrange- 

 ment .of its particles enables us to decide upon the 

 meteoric origin of masses of iron which are occasionally 

 found scattered up and down the surface of the earth. 



621 Where have such masses been found? 



In the south of Africa, in Mexico, /Siberia, and on 

 the route overland to California. Some of these masses 

 are of immense weight, and undoubtedly fell from the 

 atmosphere. 



622 How are meteorites supposed to originate ? 



four hypotheses have been advanced to account for 

 the origin of these extraordinary bodies : 1. That they 

 are thrown up from terrestrial volcanoes. 2. That they 

 are produced in the atmosphere from vapors and gases 

 exhaled from the earth. 3. That they are thrown from 

 lunar volcanoes. 4. That they are of the same nature 

 as the planets, either derived from them, or existing 

 independently. 



623 Which of these hypotheses is regarded as most probabk ? 



The fourth most fully explains the facts connected 

 with the appearance of meteorites, and the third like- 

 wise has some strong evidence in its favor. 



624 In what respect do shooting stars differ from meteors ? 



Their altitude and velocity are greater, they are far 

 more numerous and frequent, and are unaccompanied 

 by any sound or explosion. Their brilliancy is also 

 much inferior to that of the meteor / and no portion of 

 their substance is ever known to have reached the earth. 



625 What do we know concerning their altitude f 



Owing to their great number and frequency of occur- 

 rence, many careful observations have been made upon 



