CHAMPLAIN DIVISION. 125 



other, and hence we can not say where one begins and the other ends. Still it is to be re- 

 membered that the thick-bedded mass is not always present : thus, near Utica, it seems to 

 be replaced by the Oneida conglomerate. Thej are not to be regarded, however, as equi- 

 valent rocks, for both exist together in the valley of the Rondoni iii Lister county. The 

 thick beds may be observed in many places east of the High falls, exposed by the exca- 

 vations along the Hudson and Delaware canal, and also by the main road leading up the 

 valley. The mass may be observed to still belter advantage at the northern outcropping 

 along the termination of the Helderberg range, where it probably forms the thickest mass 

 of any other locality in the State : it is here composed of alternating beds of sandstone and 

 black slate, the latter varying in thickness from twelve to eighteen inches. The entire 

 thickness of the mass here is not less than seven hundred feet. It has a slight dip only to 

 the southwest, and is finely exposed from top to bottom by a small stream which flows 

 over it near the roadside. It is here almost destitute of fossils, and in this respect resem- 

 bles the beds which occur in patches upon the east side of the Hudson, along the Western 

 railway. These latter beds may be clearly distinguished from the slates and shales of the 

 Taconic system : they neither conform with them in dip, nor in strike ; and except in the 

 immediate vicinity of the great northern fracture of the Hudson valley, their dip and dis- 

 turbance is not excessive. 



This mass of slate and sandstone is almost worthless as a material for construction. Beds 

 of the thick sandstone, in the course of a few years, break and fall into angular fragments ; 

 and even where they are defended in a great measure from the operation of atmospheric 

 causes, they are very liable to crack. This may be seen on the Western railway, near 

 Greenbush. The stones appear sound when first quarried, and so remain for a year or 

 two, when they begin to show the influence of the weather. It is proper to state, how- 

 ever, that the disposition to crumble by the action of the weather, is less in Oneida and 

 Oswego counties, where the same rock is quarried for grindstones : here the layers are quite 

 regular, at least in some portions of the rock. 



§ 9. Oneida conglomerate. 



This rock is the newest member of the Champlain division, and, like some other depo- 

 sits, is not continuous over wide areas. Its composition and character may be understood 

 by those who are familiar with gravelly and sandy beaches, or pebbly beds, which, when 

 indurated or consolidated, are perfect representatives ofthis mass. It is formed of rounded 

 oval pebbles, small and large, intermixed with sand. Very little cement agglutinates the 

 mass. Green chloritic matter is not uncommon in the body of the rock. It is firm ; quite 

 remarkably so, as it is often employed for millstones. 



The Shawangunk range in Ulster county is composed of this rock, and the conglomerate 

 near Utica belongs to the same formation. It is limited to those two ranges in New-York, 

 and these are disconnected. The first is by far the most extensive and important. At 

 Utica, it is a mass twenty or thirty feet thick, overlying and resting immediately upon the 



