62 



CLARKE AND STEIGERI METALLIC ELEMENTS 



In round numbers, abolit 1200 such analyses, nominally com- 

 plete, have been made and in 793 of them barium oxide was 

 determined or proved to be absent. The mean of these determi- 

 nations, counting absences as zero, is 0.0104 per cent, which is 

 probably a maximum. If the remaining 407 rocks were all free 

 from barium, and so regarded, the average percentage of BaO 

 would be 0.069, a minimum; and between the two figures the most 

 probable value would lie, their mean being 0.086. Upon this 

 basis of computation the following table of percentages has been 

 constructed. 



TABLE 3 

 Summary of Data from Rock Analyses 



In three of the composite analyses already cited, similar deter- 

 minations were made, and the results obtained fit in fairly well 

 with the figures of this table. 



The percentages found are shown in the following table : 



The data so far obtained may not be final; but they clearly 

 indicate the several orders of magnitude which it was sought to 

 determine. 



