332 



STRATIGRAPHICAL GEOLOGY. 



find the purest carbonate of lime yet seen. This is interrupted by chlo- 

 ritic rock, — to be succeeded by fossihferous slate and limestone, — which 

 passes west of the slate quarry and lower down 

 the hill, if its strike does not alter. Commenc- 

 ing near the fork in the road turning to the slate 

 quarry, there is, first, the chlorite rock on Fig. 41, 

 with its usual position; second, the Helderberg 

 rocks just mentioned. The slates predominate, 

 and decompose readily and unequally. High up 

 the hill is the gray sandstone, decomposing white, 

 continued from Fig. 40. The hornblende rock on 

 the crest of the hill is one massive stratum, with 

 no indication of divisional planes. The slates 

 were at first thought to be the continuation of 

 the quarry ledge on Fig. 42. Both have the py- 

 rites in abundance, and the same general aspect; 

 but, by comparing the several figures together, 

 it seems as if the sandstone would properly corre- 

 spond with the conglomerate back of the quarry ; 

 and the hornblende rocks agree with the green 

 schist. That would make the slates just men- 

 tioned correspond with each other, as well as the 

 harder dark slates in which a synclinal appears. 

 The latter slate is a hard, black, even-bedded rock, which also shows 

 itself continuously nearly to Parker brook. The east part of the syncli- 

 nal is wanting in Fig. 41, its supposed place being covered by the allu- 

 vium of the Ammonoosuc. The strike varies to the north-west near L. 

 A. Parker's house, at the east end of the section ; and the rock makes a 

 part of the zigzag arrangement before alluded to. 



The next section (Fig. 42) passes from the slate quarry to the Ammo- 

 noosuc river, near the south line of Littleton, a mile and seven eighths 

 long, and seven eighths of a mile south-west from P^ig. 41. The same 

 hill is traversed as before, but the upper slates are better displayed. They 

 are covered by two grades of argillaceous sandstones, the lower portion 

 being more argillaceous and of a darker color; the upper grayish, and of 

 a different texture from the sandstones on Figs. 40 and 41. The hill 



