222 



WILLIAM H. EMMONS 



location of the rocks analyzed. The most basic (F) is not at the 

 center of the stock, but southeast of it, and the most acid variety 

 (A) is farther from F than the edge of the stock in several other 

 directions. Moreover, the diorite south of F or between F and the 

 border toward the south is less acid than A, though it is much more 

 acid than F. It will hold true, however, that if lines are drawn to 

 the border radiating from F, the composition of the stock along these 

 lines becomes gradually more acid, though at different rates, and 



Fig. 3. — Outline of Haystack stock. The letters show the position of analyzed 

 types. 



some portions of the periphery are more acid than others. The 

 modes of the six varieties are tabulated below. A, B, and C are the 



MODES OF VARIETIES OF HAYSTACK STOCK 



Quartz 



Orthoclase 



Albite. 



Anorthite 



Hornblende 



Pyroxene 



Biotite 



Olivine and Serpen- 

 tine 



Magnetite and Ilme- 

 nite 



Apatite 



4.9 



19.2 

 26.7 



30-9 



4-S 

 6.8 



5-8 



