410 THE JOURNAL OF GEOLOGY. 



mistaken for the dip by the early workers in this region. A line 

 drawn tangentially across the apices of the serratures shows the 

 dip to be some 45° westerly in the upper (westerly) part. In this 

 section the schist may be safely assumed to have a thickness of 

 800 feet. In some localities it is not over 50 feet thick, but 

 just south of Chittenden village more than looo feet occur. All 

 through the area the schist carries abundant lenses of secondary 

 quartz introduced along the bedding and cleavage planes. These 

 are considered genetically to be the excess of silica, resulting 

 in great part from the decomposition of silicates originally in the 

 rock, the alumina and potassium going to form the muscovite. 

 Phases of the rock are without such lenses and are nearly free 

 from quartz ; other phases are largely quartz layers with thin 

 folds of mica between. Some phases carry secondary feldspars, 

 but they are exceptional. Under the microscope the normal 

 constituents of the schist are seen to be a varying percentage of 

 chlorite, a great deal of muscovite in slender, closely-packed 

 plates and quartz in thin layers and scattered through the rock. 

 Biotite in larger flakes is also universally present, with occasional 

 feldspar grains. 



Beneath the schist is the micaceous quartzite horizon, poorly 

 represented in this section, but on Nickwacket Mountain having 

 a thickness of 500 feet at least, and carrying several thin beds of 

 crystalline limestone. Here there are not over 100 feet, with no 

 interstratified limestone beds. It has scattered through it 

 abundant pebbles of feldspar (microcline and orthoclase) besides 

 quartz. The pebbles are small and have undoubted clastic out- 

 lines. Owing to their occurrence, this horizon is particularly 

 easy to identify. Its strike is a little west of north, and the dip 

 80° easterly. Going east from the Olenellus quartzite the dips 

 have grown continually steeper and now we find the rocks over- 

 turned to the west. This horizon presents many phases ; traced 

 south five miles it becomes a muscovitic schist, highly contorted, 

 in which there is no evidence of detrital material ; traced east- 

 ward towards the heart of the range, when caught in synclinal 

 folds it is a granular, micaceous gneiss. Secondary feldspars 



