THE WORLD IN THE MAKING 23 



Naturally the great central mass, our sun, grew even more 

 rapidly, for its pull was in proportion to its mass, so that it 

 reached out in its might to draw to itself many times the 

 number of planetesimals that the relatively small earth could 

 reach. 



This process has been going on for long ages and still goes on. 

 The earth comes near some small mass moving in its orbit and 

 by its tremendous gravity pulls it toward itself. It rushes 

 toward the earth, passes through the outer air with such ve- 

 locity that the friction heats it intensely; it continues to fall a 

 burning mass and usually is consumed, but at times may reach 

 the earth's surface. These bodies we call meteors or, improperly, 

 falling stars ; if a star should hit the earth we would not live to tell 

 the tale. H. A. Newton estimates from his careful observations 

 that sixteen millions of these meteorites enter our atmosphere 

 every twenty-four hours. According to William H. Pickering 

 they add over one hundred tons to the earth each year. "By 

 far the most of them are so minute that they are consumed before 

 they reach the ground, though about one thousand do that every 

 year, some of them of considerable size." The meteorite that 

 Peary brought down from the North now in the American 

 Museum of Natural History, New York, weighs more than thirty- 

 seven tons. There have probably been much larger ones. 



Not far from Flagstaff, Arizona, is a remarkable crater-like depression 

 [Fig. 20]. The rim of it, rising about 140 feet above the plain, can be seen 

 from the railroad, passing Canon Diablo. The depression has a diameter 

 of about three-quarters of a mile, and the bottom is 500 feet below the top 

 of the rim, 350 feet below the surface of the plain. No one can look upon 

 this remarkable phenomenon without thinking of the craters of the moon. 

 But there are no signs of volcanic action ever having taken place in this 

 region; the thing is out of the question. The rim piled around the crater 

 has not come from the interior of the earth, but is composed of sandstone, 

 which in some way has been lifted above the plain. Some of the great 

 masses of this sandstone have apparently been highly heated and crystal- 

 lized, but most of the rock has been crushed and shattered. The whole 

 neighborhood is sown with meteors. 



