No. 104.] 195 



4. The Lower Helderbero limestone formation, in its most 

 easterly extension within New York, appears in the Ilclderberg' 

 mountains and extends west as far as Herkimer county. The lower 

 beds of the formation afford a very excellent buildinjjj stone of a 

 dark-bluish color, which, when polished, is nearly black. It is 

 princij)ally quarried at Sdioharie and Cobleskill ; it is likewise 

 worked at Carlisle and Cherry Valley, and to a small extent at points 

 west of the latter place. The middle portion of the group consists 

 of a gray or bluish-gray subcrystalline limestone, but affords no beds 

 of great value for building material. The upper member of this 

 formation is a gray subcrystalline limestone, sometimes variegated 

 with brownish spots from organic remains. It is quarried both for 

 a building stone for rough masonry, and likewise for a marble, bear- 

 ing a pretty good polish, and the variety of color from the fossils 

 gives it a handsome appearance. 



5. The Upper Helderberg limestone formation consists princi- 

 pally of two members, the Onondaga and Seneca limestones. The 

 former was so named from its having been extensively quarried in 

 Onondaga county ; and the latter, from its greater development in 

 Seneca county. 



This formation, or group, extends through the State of New York 

 from the Hudson river westward to Black Rock on the Niagara. 

 Constituting the higher limestone of the Helderberg mountains, it 

 approaches tiie river, and continues in its outcrop along the river 

 counties as far as Kingston in Ulster, where one of its members is 

 largely qu;irried for various building purposes. The Onondaga lime- 

 stone la worked at various points along its outcrop; but the principal 

 quarries are in the county of Onondaga, to the southward of Sja-acuse. 

 From this neighborhood, the stone was used for building some of 

 the locks on the Erie canal in its original construction, and has been 

 extensively used in the enlarged canal, as well as in the buildings of 

 Syracuse. The upper member of the formation is quarried at 

 Springport in Cayuga county, and largely in the neighborhood of 

 Seneca Falls. From this point through the western counties one or 

 both the members of this group are more or less extensively quar- 

 ried, and used in building, or for door and window caps and sills, 

 foundations, and other masonry. 



6. The TuLLY limestone constitutes a belt of formation of from 

 one to twenty-five feet in thickness, lying above the shales of the 

 Hamilton group and below the Genesee slate. The geographical 

 extent of this formation is very limited, having no great thickness 

 or importance to the east of Cayuga county, and almost entirely 

 disappearing on the west within the limits of Ontario county. It is 

 mentioned here among the sources of building material, but it is 

 rarely in such a condition as to be reliable for this purpose. 



