THE AVERAGE IGNEOUS ROCK 



781 



for the combined granite and basalt) with Fig. 3. The lines in 

 Fig. 3 intersect within a much smaller area than in Fig. 4, which 



1005: 

 Sandstone 



100% 

 Limestone 



Fig. 4.- — The lines on the triangle show for each constituent the proportions in 

 which the three sediments combine to yield the same amount of that constituent as 

 Clarke's average igneous rock. Compare with Fig. 3. 



is simply another way of expressing the closer accordance of the 

 granite basalt average with the sediments as compared with 

 Clarke's. 



