MAPPING CRYSTALLINE ROCKS OF ADIRONDACK REGION 135 



being the more prevalent. But in the report for 1895 it was 

 shown that several large areas of gneiss are younger than the 

 limestone; and both in that and in the report for 1897 it was 

 stated that there is nothing to show that the limestone is not the 

 oldest formation of the region. Like the question of origin, that 

 of relative age must always be troublesome and, in many cases, 

 be answered only by indirect evidence; hence,, again, the import- 

 ance of localities, like the one under consideration, where the 

 relation is evident. 



As already intimated, the general areal relations indicated in 

 the report for 1897 have been found to hold good for the entire 

 western half of the Adirondack region, gneisses being the pre- 

 dominant rock, with minor crystalline limestones, granites, gab- 

 bros, etc. 



In regard to the gneisses, one farther point demands particular 

 mention. In the last report much space was given to the dis- 

 cussion of the augite syenite of Diana and Pitcairn, and it was 

 shown to pass over into typical gneisses. Much evidence indi- 

 cates that the syenite gneiss is a widespread and important rock; 

 and Prof. Cushing has described 1 large areas in Franklin county. 

 In the field work of the past season it was found impossible to 

 separate this rock from other gneisses in the time available, and, 

 as previously said, it therefore is not distinguished on the map 

 except in the single type locality where its relations to the lime- 

 stone show its undoubted intrusive nature. 



iBul. geol. soc. Amer. 10:177-92. 



