GEOLOGY OF THE CONNECTICUT VALLEY DISTRICT. 3 II 



direction. At A — 3 there is a mass one hundred feet wide, vertical, 

 running nortli-east, and seen for five hundred feet distance. The two 

 bands probably make a synclinal axis with each other, as in the main 

 range. AH the phenomena in the two ranges are identical. 



Topographically speaking, the conglomerate ledges always occupy the 

 highest ground. The eastern bands just mentioned in Lyman average 

 about a thousand feet altitude above the sea, falling off after entering 

 Bath, where the whole country slopes towards the Ammonoosuc. While 

 the western band is usually greatly elevated, it does not follow the crest 

 of the hill beyond the vicinity of Aldrich's. From about V — 12 to J. 

 Williams's, there is a uniform descent of nearly seven hundred feet. The 

 great depression along Smith brook I have thought may indicate a sink- 

 ing of the strata, rather than the complete result of erosion. Such a 

 supposition may aid us in elucidating the marvellous changes in the sur- 

 face of the country since Huronian times. To the south of Smith brook 

 the country rises, but not so greatly as at Aldrich's, and it falls off to 

 about the level of Smith brook at its southern termination. The topog- 

 raphy of the eastern belt of the conglomerate agrees essentially with that 

 of the western. 



Cambrian Clay Slate. 



From northern Massachusetts to Fairlee pond, Vt., there is a nearly 

 continuous band of clay slate believed to be of Cambrian age. As may 

 be seen upon the map, it lies to the west of the Huronian. Occasionally, 

 as at Norwich, there seem to be limited bands of this formation left in 

 the synclinal axes, as relics of its former extent, covering over the green 

 schists. If wc continue the line of outcrop northerly, it strikes across 

 Bath and Lyman exactly in the course of an extensive development of 

 the same rock, occupying the centre of the Ammonoosuc gold field, and 

 isolated from all connection with similar layers elsewhere. For this and 

 other reasons it is probable that the Ammonoosuc slates belong to the 

 same range with those farther south in the Connecticut valley, and that 

 all of them are to be regarded as Cambrian, or of the same age with the 

 auriferous slates of Nova Scotia, called the representatives of the Eng- 

 lish Lingula flags, by Selwyn. Nevertheless, it is true that there is also 

 a range of this slate west of the Huronian, above the mouth of the Pas- 

 sumpsic river in Vermont. 



