Frazer.] 



406 



[April 16, 



Assuming the jjyroxene analyzed by Mr. Hawes to represent that con- 

 stituting part of these traps, and assuming furthermore, the above 

 average of 40 analysis of Labradorite as constituting the remaining part, 

 we have the following comparative table, which is calculated by com- 

 paring the sum of the percentages of each element of the two minerals 

 with double the percentage of the same element in West Rock. 



Pek Cent. 



Of the constituents necessary to form a mixture of one molecule of each 

 of the above mentioned minerals, there are in West Rock : 



* Dana's Min., p. 218, PI. 7. 



