RELATIVE ABUNDANCE OF THE ELEMENTS. 19 



Solid crust Ocean Mean 



93 %. 7 %. including air. 



1. Oxygen ... 47*29 85-79 49-98 



2. Silicon ... 27'21 25-30 



3. Aluminium ... 7'81 7'26 



4. Iron ... 5-46 5-08 



5. Calcium ... 3-77 0'05 3-51 



6. Magnesium ... 2-68 0-14 2-50 



7. Sodium ... 2-36 1-14 2-28 



8. Potassium ... 2-40 0-04 2-23 



9. Hydrogen ... 0-21 10-67 0-94 



10. Titanium ... 0'33 0'30 



11. Carbon ... 0'22 0-002 0-21 



12. Chlorine ... 0-01 2-07 0-15 



13. Phosphorus ... 0-10 0-09 



14. Manganese ... 0-08 0-07 



15. Sulphur ... 0-03 0'09 0-04 



16. Barium ... 0-03 0-03 



17. Nitrogen ... 0-02 



18. Fluorine ... 0-02 0'02 



19. Chromium ... 0-01 O'Ol 



These numbers, it must be remembered, are merely esti- 

 mated, and can only claim to be approximations. They have 

 been deduced from many analyses of rocks, but our acquain- 

 tance with the distribution and relative abundance of these 

 rocks must obviously be incomplete. 



The above table, however, giving as it does the proportions 

 by weight of the elements, does not really represent their 

 relative abundance reckoned in atoms. This latter certainly 

 appears to the author to be the more correct way of grading 

 their importance. In order to find the relative number of 

 atoms it is only necessary to divide the numbers in the above 

 table by the respective atomic weights. In this way the 

 following table has been calculated, giving the number of atoms 

 of each element present in a total of 100,000 atoms. 



Table showing the relative numbers of atoms of the elements 

 present in the earth's crust to a depth of 10 miles, including 

 the ocean and the atmosphere : 



c 2 



