286 



ANNUAL REPORT SMITHSONIAN INSTITUTION. 1920. 



of aluminum 7.30, and of the other most abundant elements in simi- 

 larly slightly less amounts than in Table II. When thus reckoned 

 chlorine and carbon fall in between titanium and phosphorus, with 

 percentages, respectively, of 0.29 and 0.18, while nitrogen appears 

 between chromium and zirconium with a percentage of 0.03. 



Leaving these refinements out of consideration here, there are some 

 striking features presented in the table to which attention may be 

 called. The first is the appearance among the abundant elements of 

 some that are usually counted as rare. Among these are especially 



1. 



2. 



3. 



4. 



5. 



6. 



7. 



8. 



9. 

 10. 

 11. 

 12. 

 13. 

 14. 

 15. 

 16. 

 17. 

 18. 

 19. 

 20. 

 21. 

 22. 

 23. 



Table II. — The chief elements in the earth's crust in order of abundance. 



Oxygen 46. 43 



Silicon 



Aluminum 



Iron 



Calcium 



Sodium 



Potassium 



Magnesium 



Titanium 



Phosphorus. _. 



Hydrogen 



Manganese 



Fluorine 



Chlorine 



Sulphur 



Barium 



Chromium. 

 Zirconium.. 



Carbon 



Vanadium. . 



Nickel 



Strontium.. 

 Lithium 



27.77 

 8.14 

 5.12 

 3.63 

 2.85 

 2.60 

 2.09 

 .629 

 .130 

 .127 

 .096 

 .077 

 .055 

 .052 

 .048 

 .037 

 .028 

 .027 

 .021 

 .019 

 .018 

 .003 



100.000 



titanium, barium, chromium, zirconium, vanadium, nickel, strontium, 

 and lithium, with copper, cerium, glucinum, cobalt, and boron among 

 those to which no definite figures can be assigned as yet. Titanium 

 occupies the ninth place among the elements (tenth among the oxides) , 

 although it is usually considered a " rare " element, and its name and 

 existence are possibly unknown to many persons. The establishment 

 of this fact, probably a very important one in our study of the con- 

 stitution of the earth, is due primarily to the chemists of the United 

 States Geological Survey, who, under the leadership of Dr. W. F. 

 Hillebrand beginning in the early eighties of the last century, first be- 

 gan to determine the " rarer " elements in their analyses of the rocks 

 of this country. Similarly, they found that some others of the sup- 



