50 CHAMPLAIN DIVISION 



the primary. This statement has proved true. On page 230 of the Report for (lie same 

 year, it will be found that a sandstone in Essex county was determined to be the same as 

 the Potsdam, and tliat it is succeeded by the Cakiferous sandrock of Eaton. 



The New-York system commences, then, with the Potsdam sandstone ; a roclv far from 

 being homogeneous in its composition, but consisting mainly of three portions, a conglo- 

 merate at base, an even-bedded sandstone in the middle portions, and a mass of siliceous 

 dark-colored slate with fucoids at the superior portion. Its lithological cliaracters are not 

 uniformly the same. The conglomerate is sometimes wanting, or is imperfectly deve- 

 loj)ed. and it also contains irregular beds of breccia in which there are masses of grey 

 sedimentary limestone ; a fact which is not to be forgotten. Besides these, there is a 

 mass of coarse dark-colored sandstone, traversed or checked by thin seams of grey rpiartz. 

 This last mass is well developed toward Cliamplain in Clinton county. The conglome- 

 rate along the Provincial line of New-York and Canada East, is more than three hundred 

 feet thick. This thick mass thins rapidly southwardly ; and in the valley of the Mohawk, 

 the entire mass of sandstone, as well as the conglomerate, has disappeared. In the 

 absence of the Potsdam sandstone, the succeeding rock, the Calciferous sandstone, rests 

 frecpiently ujjon the Primary system, as at Littlefalls. The fossils of this rock are fucoids, 

 and a single species of Lingula ; the latter are in great abundance at the High bridge near 

 Manchester ujjon the Ausable. The same shell occurs at French creek upon the St. 

 Lawrence. 



The rock succeeding the Potsdam sandstone, is, as has already been stated, the Calcife- 

 rous sandrock of the late Prof. Eaton. This too, is one extremely heterogeneous in its 

 composition ; consisting of a grey sandy limestone, a white but quite siliceous limestone, 

 two or three encrinal masses which are nearly pure limestones, and often with layers fit 

 for polishing, and which form a tolerable handsome reddish marble. The most extraor- 

 dinary mass, however, is a reddish sandstone, witli thin inconsiderable layers of slaty 

 laminfe': if traced upward, it becomes a tolerably pure limestone, stained slightly with 

 iron, but sometimes white. Layers from eighteen inches to two feet thick of black chert 

 often appear, and alternate with the grey sandy variety. In addition to the above, we 

 frequently meet with layers charged with fine quartz chrystals, intermixed with calc spar, 

 sulphate of barytes, sulphuret of iron, etc. 



Another mass, the place of wliich is very doubtful, is a brownish tough sandstone, 

 lying beneath all the other masses composing the Calciferous sandstone. The question in 

 regard to this mass, is whether it is to be considered as an equivalent of the Potsdam 

 sandstone, or as belonging to the succeeding mass, the Calciferous sandstone. The deter- 

 mination of this question is, however, of no importance to the subject under discussion ; 

 yet the mass is in a few places an important rock, as at Mount Toby in Washington 

 county, where it is one or two hundred feet thick. This, together with the red sandstone 

 just spoken of, I am sometimes disposed to consider as equivalents of the Potsdam sand- 

 stone. Perhaps it would be hotter, however, to regard tlieni as intermediate masses, so 

 long as there are no decisive characters on either side. 



