17 THE STORY OF THE EARTH. 



abundant constituents of surface rocks, no true 

 quartz has been r© : . ill any meteorite. But 



a rare mineral asmanite with many of the proper- 

 of quartz (u curs, which somewhat resembles 

 variety of quartz found in some volcanic 

 rocks, which has been distinguished under the 

 name tridymite. 



tot ten rare minerals are met with in me- 

 which have never been recognised in the 

 reck materials of the globe. 



On the other hand, earthy meteorites have 

 ded many of the constituents of volcanic and 

 crystalline rock 



TWO kinds of felspar — named labradorite and 



baVC been recorded m meteorites, and 



h minerals as Augite, Bronzite, 



, which upon the earth are often combined with 



the ' - in mineral union to form line 



But the and too obscure 



|0 more than stimulate interest in the relation 

 of the earth to the bodies among which it mo | 



CHAPTER II. 



THE | tRTH'l IN 11 ANAL HIAT. 



THI earth has an internal heat Of its own, 



whi< The t 



aturc of P itta sum- 



[n mil India at a depth of 



:it all the y 



an unv.. 



it ioo fe< : th's 



surface, i to Increase be 



