ADIKOXDACK SYEXTTK AIIEAS 187 



when weathered, are absolutely not to be cliBtingiiished from other rocks 

 of apparently quite different relationships. 



A variation is also shown in the opi)osite direction. Belts of very 

 acid, red granitic gneisses consisting essentiall}^ of microperthite and 

 quartz, with or w^ithout hornblende and augite, occur in the syenite- 

 gneisses and seem to grade into them. For the most part they differ 

 greatly in appearance from the usual granitic gneisses of the Adiron- 

 dacks, being of coarse grain, with the quartz in the much elongated form 

 in wdiich it is found in the syenite-gneiss. These rocks are not so w^ell 

 shown in the Loon Lake belt as in others to he luentioned. The seem- 

 inq gradation of the one into the other, the identity of the horn))lende 

 and augite, when they occur, in the two rocks, and the peculiar type of 

 quartz are the reasons for assuming a near relationship to one another. 



SALMOX EIVER 



A smaller belt of syenite-gneiss, some 6 miles long and 2 miles broad, 

 runs from a point about 7 miles south of Malone down into Duane town- 

 ship. It is cut through by the Salmon river and the rocks well ex- 

 posed, especially at Chasm falls. The fresh green gneisses are quite like 

 those at Loon lake; but red gneisses make up a more considerable i)art 

 of the exposures here, and in part the color is produced b}^ weathering, 

 instead of indicating a more acid rock. As a whole, hornblende is more 

 prominent and p3^roxenes less so in this belt, but no other differences 

 appear and the identity of the rocks is beyond question. The only 

 doubt is in regard to their areal extent, as they fade out into other rocks 

 through puzzling intermediate phages. 



DIANA 



According to Smyth the Diana s^^enite belt is fi^om 15 to 20 miles long 

 and 2 to 4 broad, with very indefinite limits on all sides but the north .-^ 

 To the south patches of it appear frequently in the midst of gneiss, into 

 which it seems to blend, although the relation is obscure. Irruptive 

 contacts with the limestones of the Grenville series are well shown, es- 

 pecially at Bonaparte lake. Professor Smyth writes me that he has 

 found no other large area of this rock in the western and southern 

 Adirondacks, though occasional small patches occur, with a wide range 

 in distribution.'!" 



MOUNT DEFIANCE 



Professor Kemp has called my attention to the probable identity of 



*C. H. Smyth, Jr. : This Bull., vol. vi, pp. 27W74. 



t An extended description of the Diana belt will be fouutl in Prufc&Nor bmyth'fo forthcoming 

 report in the 17th Aiin. Rep, State Geologi&t of New York, 



