580 



Report of the State Geologist. 



Series II. Crystalline limestones, ophicalcites, black hornblendic- 

 pyroxenic schists and thinly laminated garnetiferous gneisses. 



Series III. Rocks of the gabbro family, ranging from aggregates of 

 pure labradorite through varieties with increasing amounts of dark silicates 

 to basic olivine-gabbro. The varieties rich in feldspar are called anorthosites, 

 following the Canadian practice. They shade from perfectly massive varie- 

 ties into others strongly gneissoid. 



Sei'ies IV. Palaeozoic sediments, viz., sandstone, limestone and shale, 

 of which the Potsdam of the Cambrian is the oldest and the Utica shale of 

 the lower Silurian is the latest. 



Series V. Trap dikes and porphyries. 



Series VI. The glacial and post-glacial gravels, sands and clays. 

 In the subsequent descriptions a topographic sketch is first given of the 

 town, and then the several series are taken up in the above order. The iron 

 ores or other economic products conclude the local notes. The townships are 

 described in general from north to south, as follows : 



Chesterfield (revised), page 580 Schroon, .... page 592 



Jay, "581 Ticonderoga (revised), " 600 



Wilmington, ... " 585 Minerva, .... " HOC) 

 St. Armand, ... " 588 Newcomb, .... " 604 

 North Hudson, . . " 590 



Chesterfield. 



In my previous report, a map and description of Chesterfield were given 

 on page 463. The map was based on the county atlas, as the Willsboro sheet 

 of the United States Geological Survey had not at that time appeared. I was 

 misled into thinking that the western line of the town lay just beyond the 

 valley in which is Trout pond, but the new maps, especially the Ausable 

 sheet of the United States Geological Survey, and field work along the border 

 from Jay, have shown that another valley and brook lie in the interval and 

 that the gneisses extend across this western boundary, as far to the east as 

 Clintonville, embracing on the south the little crystalline limestone area, and 

 projecting into Jay. 



The rocks on the south are puzzling gneissoid types, but after a trip 

 :tc7'oss the southwestern corner of Chesterfield to Bluff mountain, in Lewis 

 township, and observations on the trend of the ranges, I am led to redraw 

 Chesterfield as in the accompanying newer copy herewith submitted This 

 also has the drainage correctly drawn and in much greater detail. 



