r94 NEW YORK STATE MUSEUM 



other than those found in the Adirondacks, the same rude cor- 

 relations will apply which are attempted there. 



The Little Falls syenite differs slightly from the usual Adiron- 

 dack syenite. It is unlike that of Franklin county in its gray, 

 rather than green color, in its very evident cataclastic structure 

 and much more pronounced foliation. The feldspar augen often 

 reach a length of an inch or more, while the remainder of the rock 

 is very finely granular. The Franklin county rocks are more even 

 grained, the augen are comparatively few and small, and the body 

 of the rock is far coarser than the granular portion of the Little 

 Falls rock. These differences largely disappear in the more basic 

 varieties^ but the Franklin representatives are, again, usually 

 coarser. These differences are mainly attributable to the more 

 severe metamorphism at Little Falls. But the combination of 

 numerous and often large feldspar augen with very fine grained 

 matrix, is not to be thus explained, and seem« to the writer to 

 point to an original porphyritic structure in this rock. Had the 

 original grain been equidimensional, it must have been very 

 coarse in order to permit of such large remaining augen, and it is 

 difficult to see how metamorphism could so profoundly change 

 most of the rock and yet leave such large crystals unaffected. 

 But, if these represent original porphyritic crystals, the complete 

 shattering of the finer portion of the rock might be easily effected 

 without great damage to the rest. Porphyritic phases of large 

 granite and acid syenite bodies are of frequent occurrence; and 

 the assumption here would afford a reasonable explanation of 

 the somewhat abnormal character of the rock when compared 

 with the usual Adirondack syenite. 



The Diana syenite seeme to possess a strictly intermediate char- 

 acter. Its color is nearer to that of the Little Falls rock, but its 

 augen do not approach those in size, nor is the residue of the 

 rock so fine grained and gneissoid, though the augen are usually 

 surrounded by a narrow zone of very fine, cataclastic material. 

 The writer is therefore disposed to class all these syenites to- 

 gether, as springing from the same magma at the same time or 

 at least at times not remotely separated. Certainly this is the 

 most natural view, in default of direct evidence to the contrary. 



