134 NEW YORK STATE MUSEUM 



only in scattered areas of small extent, wholly inadequate to ex- 

 ercise any influence on the general metamorphisrn of the region. 



A second result of interest is the finding of frequent lumps and; 

 lenses of hornblende gneiss scattered through the more acid 

 gneisses all over the region. These masses are analogous to the 

 fragments described in the report for 1895 as probable inclusions: 

 in an igneous gneiss. That they really are such now seems quite 

 certain, and they are regarded as affording most important evi- 

 dence as to the origin of the gneisses. 



A third phenomenon appears in the region about Longlake sta- 

 tion, where a light red granitoid gneiss seems., without doubt, to- 

 be intrusive in an older gray gneiss. This is directly in line with 

 facts observed near Gouveraeur, St Lawrence county, also de- 

 scribed in the report for 1895, and, as there stated, shows that all 

 parts of the gneiss are not of the same age. 



Finally, the red granitoid gneiss in the vicinity of Alexandria 

 Bay, on the St Lawrence river, was found to be younger than and 

 intrusive in the adjacent schists, which doubtless belong to the 

 limestone formation. This is analogous to many instances pre- 

 viously described in St Lawrence and Lewis counties, but is, if 

 anything, more clearly defined. It is important in affording- 

 another example of an undoubted igneous gneiss, which in every 

 way closely resembles the great areas of gneiss farther south, 

 that are regarded as igneous, and yet, on account of the absence 

 of other formations, show no conclusive proof of their origin. 

 Furthermore, this Alexandria gneiss contains many hornblende 

 inclusions almost identical with the widespread hornblende 

 masses in the gneiss formation mentioned above. Final conclu- 

 sions as to the origin of these gneisses must be based chiefly or* 

 analogy and internal evidence, such as composition and texture,, 

 and every new occurrence of closely related rocks whose origin 

 is clear is a step toward the solution of the problem. 



This occurrence of intrusive gneiss at Alexandria Bay is also- 

 important in its bearing on the question of time relations. It 

 has been generally assumed that either the gneiss and limestone 

 are one formation or that the gneiss is the older, the latter view 



