﻿i86 



NEW YORK STATE MUSEUM 



Adams also shows, in his valuable paper, the similarity in compo- 

 sition of his contact amphibolite with other amphibolites, even some 

 of igneous origin. It would seem therefore that we are reasonably 

 safe in assuming that analysis 4 will not depart widely in composi- 

 tion from most of the amphibolites of the region, no matter what 

 their origin. 



The analyses of the two granites have been already discussed. 

 No. 2 does not depart widely from no. 1 in composition, and might 

 well represent a simple variant of the magma. Its field relations, 

 however, preclude that supposition and it is to be noted that, when 

 compared with analyses 1 and 4, it represents an intermediate stage 

 in every single important constituent. On the basis of the silica 

 percentage a mixture of six parts of analysis 1 and one part of 

 analysis 4 would almost give a rock of the composition of analysis 2. 

 Calculated on that basis the following result is arrived at : 



Si0 2 . 



AI2O3 



Fe 2 3 



FeO. 



MgO. 



CaO. 



Na2p 



K 2 0. 



I 



2 



3 



70.13 



70.05 



56.58 



15-47 



14-73 



15-54 



1.52 



1 .42 



3.80 



1. 05 



1.63 



5-4i 



.85 



1. 18 



2.77 



1 .60 



1.99 



4-56 



3-72 



3-i7 



2 .91 



4-39 



5.08 



4-25 



56.62 



16.66 



3.01 



4.14 



3-97 

 5-53 

 3-58 

 3-79 



In column 1 are given the percentages of the soaked rock shown 

 by analysis, and in 2 the calculated percentages on the basis stated 

 above. They seem to us to be sufficiently alike in every constituent 

 to afford a strong probability that the field relations were correctly 

 interpreted, and that the rock is a true soaked rock. The greatest 

 variation between the two is in the alkali percentages, and these 

 are just the ones which vary most in the general granite masses. 

 The total amount of alkalies, however, is much the same in each, 

 8.11$ in the first case and 8.25$ in the second. 



The granitized amphibolite is not so definitely a soaked rock as 

 the other, since the amount of granite in it is so small, that it is 

 an impregnated, rather than a mixed rock. Nevertheless the granite 

 is thoroughly disseminated through it, though granitizing it in 

 patches rather than uniformly. Column 3 gives the rock percent- 



