Report of the State Geologist. 



21 



in such abundance as sometimes to constitute a tremOlite schist. Enterbedded 

 with the limestones are, sometimes, gneissic rocks. The author infers that the 

 limestones, having their greatest development in the northwest part of the 

 county, decrease rapidly in passing southeastward toward the heart of the 

 Adirondack^. 



Under the heading, "Origin of the Gneisses," the two important 

 problems are discussed — the origin of the gneisses, and their relations to the 

 limestones. In considering the first of these, three explanations are presented 

 as possible, and worthy of consideration; the first, that the gneisses are meta- 

 morphosed sediments; the second, that they are of igneous origin ; the third, 

 that they are partly metamorphic and partly igneous. It is shown that the 

 principal evidence in favor of the first hypothesis lies in the association of 

 the limestones with the gneisses, but this is regarded as insufficient to prove 

 that the gneisses belong to the limestone series. The second hypothesis is 

 considered in much detail. Evidence in its favor is found in the general 

 foliation of the gneisses, and in the microscopic structure of the rock afford- 

 ing various evidences of pressure, flow, and secondary changes. Facts are 

 brought forward to show that the gneiss contains masses which are inclusions 

 of some older formation, perhaps taken up by the gneiss when it was in a 

 molten state. 



As the author does not regard the gneisses and the limestones as parts 

 of one series, the former must be older or younger than the latter, and he 

 believes that the gneiss is, in part at least, the younger, and instances are cited 

 where the gneiss appears to be intrusive into the limestones, and accompanied 

 by local metamorphic contact effects. With regard to the general relations of 

 the gneisses and limestone, it is concluded by the author that the gneisses 

 constitute a complete series of rocks, differing somewhat in age, and largely, 

 if not almost wholly, of igneous origin ; that parts of this series are younger 

 than the limestones ; and while it is possible that other parts may be older 

 than the latter, there is, however, no absolute proof of this assumption. 



Report on the Geology of Clinton County. 



By H. P. Cusiiixg. 



After a general presentation of the topography of this region, the author 

 takes up for especial consideration seriatim the geologic formations, as 

 follows : 



