452 Pirsson and Washington — Geology of New Hampshire. 



Variations from the type. — The rock described may be 

 assumed to be about the average of the Belknap massif, as it 

 agrees with the microscopic examination of most of the speci- 

 mens. Indeed all of them are obviously of the perfelic order 

 and of the sodipotassic subrang. While most of the material 

 undoubtedly belongs to the persalane class there is a distinct 

 tendency in some to be dosalic, through increasing content in 

 alferric minerals. Similarly labradorite appears and may be 

 present in variable amount so that the rang will vary from 

 peralkalic to domalkalic, the latter being the more common as 

 in the type specimen. 



In order to test the amount of variation which, as stated in 

 the geologic description, appears to take place chiefly as the 

 outer border is approached, the mode of two other specimens 

 was determined by Rosiwal's method with the results given 

 below. Of these So. I is from the exposure in a ravine in the 

 little drainage on the south west side of Locke's Hill and not 

 far from the contact. No. II is from the very summit of Gun- 

 stock peak. 



Mode. Chem. composition. Mol. ratios. 



ii? i. uT i. iiT 



4-25 Si0 9 68-16 59*91 1*106 



67-95 A1 9 3 15-27 15-82 -150 



2-53 lV 2 3 0-88 2-93 '006 



13-38 FeO 1-87 4*61 '026 



7*59 MgO 1-26 1-64 -032 



3-82 CaO 0*15 1*92 -003 



0-48 Na o O 4-30 4'52 '069 



KO 7-06 6-61 -075 



Total 100-0 100-00 H 2 0'37 0*43 



Ti0 2 0-59 1-39 -007 

 P 2 5 0-09 0-22 '001 



998 

 155 

 018 

 064 

 041 

 034 

 073 

 070 



018 

 002 



100-00 100-00 



Norms. 





I. 



II. 



Qz 



13*62 



1-86 



Co 



0-61 







Or 



41-70 



38-92 



Ab 



36-15 



38-25 



An 







3-34 



Di 







3-65 



Hy 



492 



6-00 



Mt 



1-39 



4-18 



11 



1-06 



2-74 



Ap 



0-24 



0-50 



H 2 



0-37 



0-43 



10006 99-87 



