256 Trees, Stars, and Birds 



and Washington have many specimens, as have the Field 

 Museum at Chicago and the museums of Amherst, 

 Harvard, and Yale ; but the majority of small museums 

 have none, although amateur collectors are likely to 

 think that some of their peculiar-looking stones are 

 meteorites. Only about 300 of the meteors which have 

 fallen in the past 115 years have been found by any one, 

 so far as we know. Some, however, have burst while 

 passing through the air, giving rise to hundreds of frag- 

 ments which have been picked up. Genuine meteorites 

 are very interesting, because meteors are the only celes- 

 tial bodies we know that ever come to the earth. Until 

 about the beginning of the nineteenth century learned 

 men were not convinced that stones ever came to the 

 earth from a distance. Previous to that time reports 

 of falling stones had given rise to much discussion, but 

 they were explained as a consequence of thunderstorms 

 or of volcanic eruptions. 



The motion of meteors. The rapid motion of a 

 meteor when it first enters the air is unlike anything 

 we have seen moving on the earth, but is like the motion 

 of the earth itself in its course around the sun. Astrono- 

 mers believe that the meteors before we see them are 

 moving in long orbits about the sun and would continue 

 so to move if the earth did not get in their way. Comets 

 move around the sun in the same manner, and there 

 are good reasons for believing that meteors were once 

 parts of comets. 



When first seen, meteors and shooting stars muat be 

 about 100 miles, or a little less, from the surface of the 

 earth, because they are invisible until made luminous 



