ALG ONKIA N RO CKS IN VERMONT. 4 1 5 



briefly mentioned. Along the south slope of a hill just south of 

 Mechanicsville, a section is exposed showing fine-grained biotite 

 gneiss at the base, passing imperceptibly into a sugared quartz- 

 ite above. This in turn is overlain by coarse saccharoidal lime- 

 stone ; and a muscovitic, garnetiferous schist overlies this, capping 

 the summit of the hill. These rocks strike in general east and 

 west and dip northerly. A section on the southwest slope of 

 Ludlow Mountain, two miles southeast of here, exhibits at least 

 two beds of coarse limestone grading into tremolite and green 

 hornblende, interstratified with layers of schist. These rocks 

 strike west of north and dip easterly. On the southwest slope 

 of Saltash Mountain a bed of tremolitic limestone interstratified in 

 biotitic gneiss trends northwest. At Northam village, a similar 

 coarse limestone occurs associated with a vitreous quartzite, a lam- 

 inated eruptive rock and a rusty muscovitic schist. All through 

 the core there are patches of these coarse limestones in a great 

 variety of association, such as with coarse augen-gneisses (a 

 common occurrence), quartzites, schists, and other rocks. Fine- 

 grained, blue marbles are present in two or three localities. In 

 all cases the limestones are in irregular lenses, and are extremely 

 local ; their occurrence with coarse gneiss affords no evidence of 

 structure ; these scattered, irregular outcroppings and differences 

 of association make them impossible of correlation. There may 

 be two horizons of limestone in the core or there may be a dozen. 

 The same is true of the quartzites and other sedimentary rocks. 

 Limestone belts are, however, frequently identified by their meta- 

 morphosed equivalent, tremolite, or in rare instances, serpentine 

 replaces the limestone. The Mount Holly series has scattered 

 all through it these undoubted areas of sedimentary rocks recog- 

 nizable where from manifold causes they have escaped destruc- 

 tion or metamorphism, and their clastic characters have not been 

 obliterated. They probably represent remnants of a once great 

 sedimentary series older than the Mendon series. 



The rocks associated with the evident elastics present a 

 great variety of texture and mineral composition. Thin sections 

 show, however, that the differences are mainly due to variations 



