594 



Report ok the State Geologist. 



The gneisses form the western lake shore, with intervals (Nos. 76a, 77). 

 No. 78 is a light grey variety like that of the western shore, but No. 76 and 79 

 are darker, full of plagioclase, with brown hornblende, and in No. 7<> diallage, 

 so that the mineralogy suggests an altered igneous rock. The gneisses 

 continue across the hills on the south. At No. 109, on the southwest, a 

 quartz-hornblende-gneiss is met. 



On the highway running west from Sehroon lake post office, at No. 83, 

 is a quartz-hornblende-gneiss, and at No. 82 a basic hornblendic variety. 

 Outcrops are few along the road to the west, but the gneisses and limestones 

 occur just over the border in Minerva, along this general line. Particular 

 interest attaches to these relations because just to the north the spurs of 

 Hoffman mountain begin to rise and shade from gneissoid gabbros into the 

 massive anorthosites, so that the highway is not far from the boundary 

 between the two. 



Series II. The crystalline limestones are quite widespread and of con- 

 siderable area] importance. As always, they favor the depressions. Along 

 the south side of Paradox lake they are strongly developed, At No. 98b, is a 

 high ledge with a good-sized cave extending into it. The limestones reach 

 up into the valley to the northeastern portion of the town, and are prolonged 

 into Crown Point, as show n on the map of that town already published. In 

 the valley of Alder brook, that is the outlet of Crane pond, the limestones are 

 abundant all along the highway, and with them are the usual black schists. 

 The limestones appear again at Nos. 7<>a and 77, on the west shore of Sehroon 

 lake. They were not met elsewhere, although abundantly developed iu 

 Minerva. 



The limestones are white, coarsely crystalline and graphitic. They 

 seldom show any large cross-section, say twenty-five to fifty feet, without 

 bunches and knobs of dark silicates, or scattered irregular bits of pyrrhotite, 

 hornblende, pyroxene, Hakes of phlogopite, etc. 



Series III. The anorthosites and gabbros constitute the northern portion 

 of the town and rather more than one-third of its area. They are prevailingly 

 gneissoid, and as the areas of the gneisses of Series I are approached, they 

 become very strongly so, almost to the extent of schistosity. This tends to 

 decrease in the interior hills, and at No. 95 quite coarsely massive varieties 

 are attainable. All over the adjacent areas on the south are huge boulders, 

 often as large as a small house, of the light bluish anorthosite, that has 

 come from the inner hills. At or near No. 87a, I paced one that was roughly 

 oval, 30x20 feet, and that projected six feet above the turf, w ith an unknown 



