166 Pi'of. J. D. Dana — Metamorphism of 



(2) Vicinity of the Feelcslcill Limestone areas. — The Peekskill 

 limestone areas have similar stratigraphical relations to the norite 

 and the other Cortland rocks. One of the two areas extends up 

 Sprout Brook or Canopus Hollow, and the other up the valley in the 

 village of Peekskill along which Center-street descends toward the 

 river. The southern extremities of these areas are shown on the 

 map, page 60 ; the former has the strike N. 62° E. and dip 75° S. ; 

 the latter N. 78° E. dip 75° S. Figure 17 represents a section 



Fig. 17. 



a b c d e f g h 



about 1300 yards in length fi'om north to south, along the line 

 marked a h c on the map, starting from the limestone at the mouth 

 of Sprout Brook, near the Ironworks. The limestone (a) lies 

 against true, whitish, well-bedded, conformable quartzite (a to h) ; 

 this quartzite changes gradually to jointed massive granitoid and 

 gneissoid quartzite, with only an occasional bedded band or plane ; 

 each such band or plane is conformable in direction to the limestone 

 and the adjoining bedded quartzite. This quartzite (the rock 

 referred to on p. 24, vol. xx. Am. Jour. Sci.) continues southward to the 

 Center-street valley, but on the north side of the valley, just back of 

 Hill's Foundry, it is followed by an arenaceous mica-schist (c d), 

 with the strike varied to N. 78° E. the dip remaining the same ; 

 then, on the south side of the valley, 50 yards above Baxter's Iron 

 Works (on Water-street), the limestone of the second belt outcrops, 

 having the same dip and strike as the mica-schist ; and behind these 

 ironworks, thin-fissile dark-grey mica-schist (containing both white 

 and black mica) appears conformable in position to the limestone ; 

 then, after an earth-covered interval of about 200 yards, there is an 

 outcrop of massive norite along South-street, north of Hudson- 

 street, which is without bedding, but has an extremely micaceous 

 layer — a kind of coarse mica-schist — intersecting it near its middle, 

 which is conformable in its strike and dip with the mica-schist and 

 limestone of Center-street valley ; and it shows conformable planes 

 of bedding also near its south extremity. Moreover, this norite has 

 a lighter-grey colour and contains more quartz and orthoclase than in 

 other outcrops more remote from the mica-schist and limestone, and 

 thus exhibits an intermediate character corresponding with its inter- 

 mediate position. This stratification in portions of the norite is 

 also distinct a mile to the eastward of this locality on the same side 

 of the limestone, at the point mentioned on page 59. 



The granitoid and gneissoid quartzite of Peekskill loolcs much like 

 true granite and gneiss ; but its transition to bedded quartzite shows 

 what it in fact is ; and this is confirmed by the examination of thin 

 slices, the quartz in it proving to consist of an aggregation of grains 

 just like a sandstone. (The transition of this granitoid quartzite to 



