REPORT OF TITE DIRECTOR AND STATE GEOLOOIST 



inclusions of schist seem to have been slightly blended with the 

 gneiss by melting, but as a rule ihe boundaries arc sharp, and 

 arc always so in the case of quartzite. The latter lock, being 

 more massive, is less apt to furnish elongated inclusions. As 

 in other parts of the region, the elongated inclusions nearly 

 always are placed with their long diameter, parallel to the 

 foliation of the gneiss. 



These phenomena of dikes and inclusions are of the greatest 

 moment, since they afford the chief criteria for establishing the 

 origin and age of the gneisses. This is particularly true of tin? 

 inclusions, since the heart of the Adirondack region consists 

 almost wholly of gneisses, the only positive and direct evidence 

 as to whose origin, so far as the writer is aware, is afforded by 

 scattered inclusions analogous to those above described. For 

 this reason these phenomena demand farther brief consideration. 



The localities described, and others mentioned below, are of 

 particular importance, because the phenomena are presented with 

 such diagrammatic clearness that they admit of but one explana- 

 tion. At the same time, it is evident that they are strictly an- 

 alogous to cases farther south, which, though more obscure, were 

 interpreted in the same manner, as stated at some length in the 

 report for 1895. 



As there stated, the phenomena described might be regarded 

 as broken intrusions, segregations, or inclusions, and reasons were 

 given for concluding that they were the latter. In the present 

 instance, though we have to deal with similar phenomena, it is 

 possible to come to but one conclusion in regard to them. 



The schists and quart zites, as seen in place, are found to be 

 cut and veined in every direction by a granit e-gneiss, and frag 

 mcnts of schist and quartzite, in every way identical with the 

 main mass, are scattered through the granite-gneiss, and are them- 

 selves penetrated by networks of dikes running in from the 

 latter. . 



The composition and structure of the fragments are, in them- 

 selves, enough to show that they are neither intrusions nor 

 segregations, while it is clear that they were solid when the 



