GEOLOGY OF THE NORTHERN ADIRONDACK REGION 317 



that future work will show that this is not the case. There are 

 several considerable masses of the rock in this county, the chief 

 ones being the Loon lake, Tupper lake, Saranac river, Duane and 

 Salmon river areas. They all show very similar rocks, and all 

 run into mixed rocks at their boundaries, that is, gneisses which 

 seem referable to the syenite are inextricably involved with other 

 rocks of all sorts, so much so as utterly to defy mapping except 

 on an unwarrantably large scale. The Saranac river mass gets 

 over the border into Essex county, and there are some small 

 masses of the rock in Clinton county, notably in Black Brook 

 township. Kemp has noted the presence of much similar rock in 

 Essex, Warren and Washington counties, though here usually 

 very gneissoid and so much involved with other rocks as to render 

 it somewhat uncertain whether it is of the same age as the Frank- 

 lin rocks or not. Undoubtedly much of the rock will be found in 

 Hamilton and Herkimer counties when these shall have been more 

 carefully investigated. The work of both Kemp and Smyth in 

 these counties indicates the presence of a considerable quantity 

 of this rock, though mostly in small masses, so that the gneissoid 

 border phases, involved with other gneisses, are the usual types 

 found. 



Special reference may be made to the Little Falls syenite in 

 Herkimer. The coarse syenite of the Precambric outliers at 

 Little Falls and Middleville is very similar and wholly uncon- 

 taminated with other rocks except for a few cutting dikes. They 

 seem quite certainly parts of the same mass whose extent is con- 

 cealed by the rocks of the Paleozoic cover. To the northward is 

 a large area of a very gneissoid syenite, much involved with other 

 gneisses mostly of Grenville age, so much so as to defy attempts 

 to fix the relationships of the two, but forming a complex very 

 like that around many of the belts. 



A further special interest attaching to the Little Falls syenite 

 arises from its plainly shown gradation into a gabbroic-looking 

 rock which is very similar to the corresponding rock at Diana and 

 represents a variation of precisely the same sort. 1 



In one of the cuts at Loon lake is an apparent inclusion of 

 Grenville rocks in the syenite, which is by no means so decisive 



1 For details see N. Y. State Geol. 20th An. Rep't. p.r85-r92. 



