GEOLOGICAL RELATIONS. 2/ 



Haystack does not belong to this band, but there is reason to believe it lies beneath 

 the mountain. This thicker range of schist also carries large beds of conglomerate. 



The schists are succeeded by a thick deposit of beautiful clay slates, from which are 

 taken annually thousands of bright colored roofing shingles. It is the Georgia slate of 

 the Vermont report, supposed to belong to the lower Postdam group. The dip is east- 

 erly, but the irregularities are great enough in Wells to allow the existence of an 

 inverted anticlinal axis. A somewhat similar band occurs in the eastern part of White- 

 hall. It is not clear whether these two bands are united by a synclinal beneath the 

 schists next west, or whether the eastern belt has been elevated in connection with a 

 fault. 



The anticlinal in the schists west of the R. & W. R. R. is copied from Mather's re- 

 port, p. 424, pi. 28, fig. I. Mather did not accept our representation of the slates to 

 the west of this hill, believing there were successive uplifts of Calciferous sandrock, un- 

 derlaid by the Potsdam sandstone. This anticlinal explains why there should be a 

 broad expanse of the thin Calciferous sandrock, Chazy and Trenton limestones in West 

 Haven, Vt., north of the Poultney river; for all the northern prolongation of New 

 York is entirely occupied by Taconic rocks, which disappear wholly north of the bend 

 of Poultney river. Probably further search will develop the continuation of the Chazy 

 east of this anticlinal, between West Haven, Vt., and Hartford, N. Y. The elevation 

 has been considerable, but patches of this limestone may have escaped denudation in 

 some sheltered spot. The lower slates carry Olenellus and other characteristic lower 

 Potsdam fossils a few miles to the south. These slates agree in age with those holding 

 the Paradoxides in Braintree. The evidence seems to confirm the observations of 

 Emmons,* near Whitehall, to the effect that the Calciferous sandrock rests upon the 

 slates east of the village, the white sandstone having thinned out eastwardly. But it 

 extends a great distance southerly, and there are also a few outliers of this sandstone 

 in the same direction, indicating the greater lateral spread of the original beach mate- 

 rials in that direction. The Potsdam rests unconformably upon a very silicious rock 

 west of Whitehall, but more especially in West Haven. f This may correspond with 

 the quartzites in Dorset, as well as to the lower Potsdam sandstone of the North- 

 western states. 



*■ Agrictilttire of N. V., vol. i, pi. 18. 



t Most observers have passed by this quartzite, as if it were undoubtedly Laurentian. The section showing it 

 is in the Vermont report, vol. i, p. 263. I observed it in 1857, and well remember my speculations respecting it; 

 but, as it was my first view of the world-renowned Potsdam, I could not expect my youthful observations 

 entitled to credence, were any startling generalizations proposed. I said in my note-book, — "Here is a case of 

 unconformability in the Potsdam sandstone; the formation is not a simple one, as is universally described, but 

 represents ages so diverse as to be separated by an unconformability of 25 degrees." In my published descrip- 

 tion, I have not ventured to suggest so much, expressing the opinion that "the rock with the greater dip is as 

 distinctly quartz as the other; and there is also a large ledge of quartz rock upon the west side of Lake Cham- 

 plain, with the same inclination. Hence the sudden change in the dip is to be regarded as a safer distinction 

 between the Silurian and Laurentian series, than a difference of lithological character." 



Since 1857, the recognition of the western Vermont quartzite as lower Potsdam, by Billings, and the formal 

 separation of the St. Croix and Potsdam in the north-west, bring to mind my early speculations, and excite the 

 anticipation that further researches will develop the older group, with its fossils, along the outer line of the Lau- 

 rentian in the Adirondacks. 



