314 GEOLOGY OF THE SECOND DISTRICT. 



of the slone being a bluish grey. This mass has a compact structure, and breaks in conchoidal 

 surfaces ; and from its appearance, I consider it a good livdrauhc hmcstonc. In weathering, it 

 softens and disintegrates, and forms a yellowish earthy svibstance. 



Another variety of hydraulic lime is in the same field with the preceding ; its color is bluish 

 black ; it breaks with a conchoidal fracture, and thus resembles the black hornstone. This 

 mass is only four feet thick, and is interesting principally as adding to the varieties of this 

 rock, which have been already shown to be great. 



In Chazy, those strata which are drab-colored never contain fossils ; but at Glen's-Falls, 

 the strata equivalent to these contain fucoids, but they lie between the layers, and do not pene- 

 trate the interior. 



As the drab-colored layers of the calciferous sandrock of Eaton never contain bivalve or 

 univalve shells, it is higldy probable that the combination, or the materials forming the mass, 

 contained substances which were injurious to animal life ; or it may be possible that they were 

 formed of thick muddy matter — matter which accumulated rapidly, forming in consequence 

 a bottom unfavorable to their habits and wants. Both causes may operate : the muddy mass 

 itself may contain decomposed pyrites, or some other metallic salt, and the mass may be only 

 a few days in forming. 



Range and extent of the Calciferous sandrock. 



I have taken my type of the calciferous from the exhibition of this rock at Chazy. Such 

 will probably be found to be its prevailing character in Clinton. Such appears to be the fact, 

 from indications wherever we have an opportunity to examine it. Much of the surface, how- 

 ever, is covered with debris, and hence the opportunities for obtaining a full and correct 

 knowledge of this rock are wanting. Commencing south near Unionville in Peru, upon the 

 Little Ausable, some ten miles west of Lake Champlain, I found the calciferous outcropping 

 here upon a line running nearly north. This brings its western edge a little west of Peru 

 village ; and following this direction, with the assistance of its occasional appearance, I find 

 it four or five miles west of Plattsburgh. At about the same distance west, it runs to Chazy, 

 near Lawrence corners, where the drab-colored layers outcrop. With some interruption, it 

 pursues its course towards Chazy village, appearing about half a mile west ; though imme- 

 diately west, it is only eighty rods to the eastern outcrop of the potsdam sandstone. We find 

 it therefore verging towards the east; and hence we find that in Champlain, the adjoining 

 town, it has approached the lake full three miles. Some of the strata belonging to this rock, 

 in fact, appear upon the lake, though we still find outcropping masses two miles towards the 

 village of Champlain. The line of junction between the potsdam and calciferous is no where 

 distinctly seen. I was able often to limit this doubtful point down to thirl}^ or forty yards ; 

 but the debris, which is thick, has always prevented a full disclosure of the whole mass of the 

 superior rock. 



The western outcrop of the calciferous sandrock may then be considered as about ten miles 

 west of Lake Champlain, in the south part of Clinton, and as running a north-northeast course, 



