CLINTON COUNTY. 315 



when it actually reaches the lake near the Provincial line. The potsdam sandstone prevails 

 immediately west of this outcropping edge. But I do not intend to convey the impression that 

 this outcrop still pursues this north-northeast course : it has its limit here ; for I find that 

 according to tlie known geological structure of the northern slope into Canada, this line of 

 outcrop sweeps around to the west ; and upon this there is the same succession of rocks, in 

 advancing north again, as we have upon and adjacent to the shore of Lake Champlain. For 

 example, nine miles south or southwest of St. Johns, the identical encrinal masses of the 

 chazy rocks crop out, and are quarried for building stone. The fact, too, is brought out by 

 the dip of the potsdam in Mooers and EUcnburgh ; and from these lower masses the formation 

 or group runs up to the loraine siiales, which are fully formed at Laprairie, and are geologically 

 the highest masses on the river south of Quebec. 



I have now defined the western outcrop of the calciferous in Clinton county ; and as the dip 

 of the rocks is generally easterly, or rather northeasterly, we shall have a belt of this rock 

 parallel with that of the potsdaui sandstone. It is, however, narrow : at Chazy, it is only 

 eighty rods wide ; and it probably will not average a mile in width from Unionville to Cham- 

 plain, the whole length of the county. 



From the preceding observations, it will appear that the calciferous sandrock in Clmton 

 presents the same general characters as elsewhere. There are wanting, however, one or two 

 varieties which are found at other places ; for instance, the cherty mass, and that which 

 abounds in geodes of crystals. Both of them are found at Whitehall, and also at Essex, 

 though at the latter place it is not largely developed. The difference, however, between this 

 rock in Clinton, and as it exists in the Mohawk valley, is, that in the former a greater pro- 

 portion of calcareous matter enters into its formation, and in the latter, silex predominates. 

 Still the same general characters, as remarked above, appear in each region ; there is not, in 

 either case, so great a disproportion as to give the masses aspects which are specifically different. 



CuAZY Limestone. 



The chazy limestone, in the ascending order, succeeds the calciferous, which, as I shall 

 be able to show, has been separated from the preceding for substantial reasons. 



It is a dark-colored, thick-bedded limestone, and as it formed at Chazy, is quite rough and irregular 

 in its exterior. Its planes of bedding are very indistinctly defined and uneven, and hence never separating 

 in smooth surfaces. Its general structure appears concretionary, but ill defined. Chert or hornstone is 

 often diffused through it, particularly in those places where fossils occur, many of which are siliceous 

 casts. 



The characters above given are not absolutely uniform ; as at Westport in Essex, it is a 

 tolerably even-bedded rock, and though not free from siliceous matter, still it may be quarried 

 and employed for many purposes, being susceptible of even and handsome surfaces. But at 

 Chazy, the greater part is too irregular and uneven, and too much filled with nodular masses 

 containing chert, to be employed economically. The best exhibition of the rock is only a few 

 rods west of the village, where it forms several important ridges running nearly north and 

 south. 



