I9I2.] 



CLARKE— SOME GEOCHEMICAL STATISTICS. 



217 



igneous rocks of North America, and the analyses are nearly all 

 taken from the Survey records. 



(F) Average of 250 analyses of rocks from the Atlantic slope, 



Maine to Georgia. 78 of these are taken from Washing- 

 ton's tables, the others were made in the Geological 

 Survey. 



(G) Average of 113 analyses of rocks from the Yellowstone Park. 

 (H) Average of 137 analyses of rocks from Colorado. 



(/) Average of 195 analyses of rocks from California. 



(/) Average for all North America. The figures of column E 



combined with those of 398 analyses given in Washington's 



tables. 



For Europe the following data are sufficient, all the figures, ex- 

 cept Harker's, having been taken from Washington's tables. 

 (K) Harker's average for British rocks, as previously cited. 

 (L) Average of 231 analyses of rocks from Norway, Sweden and 



Finland. 

 (M) Average of 420 analyses of rocks from the German and Aus- 



tro-Hungarian Empires. 

 (N) Average of 250 analyses of Italian rocks. 

 (0) General mean of the foregoing 1,427 analyses, plus 122 of 



rocks from parts of Europe not otherwise covered. 

 Good analyses of rocks from Asia, Africa and Australia, at 

 least as given by Washington, are too few for satisfactory combi- 

 nation. In the next table I give a general average for North 



