ONONDAGA LIMESTONE. 179 



former anil the Ontario divison ; but as yet the relationship has not been fully stated, and 

 perhaps it will be many years before it can be determined. The same limestone which is 

 here described under the above name, is known and described in England under the name 

 of Wenlock limestone. Ours probably resembles the latter as far as any two distant rocks 

 can resemble each other. It is doubted by a few geologists, at least, whether any of our 

 rocks can be considered strictly as identical with those of Europe. For this reason, it is 

 proper, where the identity is not established, to give distinct names to the systems which 

 are widely asunder, and especially when there is really such an amount of difference as 

 there is now proved to be between the Silurian system of Mr. Murchison and the New- 

 York system. 



§ 9. Summary of the principal facts relating to the helderberg division. 



1. The greatest thickness and most perfect development exists in Albany and Schoharie 



counties, or in the eastern part of the State. 



2. The Salt group is developed only in the central part of the State. 



3. The upper part of the Onondaga limestone is the most persistent mass ; it extends 



from near the Hudson river at Catskill to Blackrock, and maintains its importance 

 throughout, though subject to variation in thickness. 



4. The lower part is the reservoir of the salt springs, the gypsum, and the hydraulic 



limes, which are the principal valuable productions of this division. 



5. The lower part of the Onondaga limestone is susceptible of receiving a polish, and 



may be wrought into mantle pieces, etc. 



6. The agricultural characters are strongly marked and important, both in the inferior 



and superior masses, but less so in the middle. 



7. The superior part is well denned, and the era of its deposit is clearly an important one. 



8. The dip of the rocks included in this division, is conformable with the Ontario and 



Erie divisions : it amounts to thirty feet to a mile, and its general direction is south- 

 west. 



3. The surface of the country over which the rocks of the Helderberg division extend, is 

 hilly in the eastern counties, but is comparatively a plain and level country in the 

 western counties, or rather the hills are not so elevated. The ranges of hills have 

 usually a north and south direction, and hence receive more sunshine than if they 

 ranged east and west. 



10. The gorges and waterfalls, though epiite remarkable in this, are less so than in the 

 Ontario division : they are formed mostly in the lower masses, the red slate and 

 Onondaga-salt group, and the limestone shales of the Hydraulic lime series. 



23* 



