GEOLOGY OF FRANKLIN COUNTY 89 



tures are the same. Upper and Lower Chateaugay lakes on the 

 Chateaugay, Chazy lake, in which the Great Chazy rises, and the 

 many small ponds at the headwaters of the Salmon and Deer 

 show the flat, poorly drained character of their upper reaches. 

 Ooing downstream, frequent falls and rapids occur where the 

 present channels are not precisely in line with the old ones. The 

 Chateaugay is out of its former channel for a long distance, and 

 lias sawed a deep, narrow gorge into the Potsdam sandstone, 

 second only in impressiveness to the Ausable chasm. The Sal- 

 mon is cutting a gorge at Malone, and has a rock bottom, with 

 rapids, at several points in Westville. While the still smaller 

 streams have scraped away the drift down to bedrock in a few 

 places, they have made no great progress in cutting into the 

 rock. 



PRECAMBEIAN ROCKS 



The Precambrian rocks of Franklin county are wholly crystal- 

 line and have for the most part a foliated, or gneissoid structure. 

 They consist in large part of rocks which are of unmistakable 

 igneous orgin, comprising gabbroic, syenitic and granitic rocks; 

 in small part of rocks of sedimentary origin, coarsely crystalline 

 limestones associated with certain peculiar and characteristic 

 schists and (gneisses; in large part again of other, mostly finely 

 granular, gneissoid rocks of unknown age and of uncertain, but 

 probably of igneous origin. These rocks are in all respects simi- 

 lar to the Canadian rocks to the northward, from which they are 

 separated by the interval in which the paleozoic rocks of the St 

 Lawrence valley are at the surface. In the writer's judgment, 

 they are to be as unhesitatingly classed with them as would be 

 the case were the covering of later rocks to be swept away, so that 

 they could be followed foot by foot across the intervening dis- 

 tance. 



These Canadian rocks were subdivided into the fundamental 

 gneiss and the Grenville series by Logan, the two constituting 

 his Lower Laurentian. Both were supposed to consist largely of 

 sedimentary rocks, and the former was regarded as the older. It 



