UPPER HELDERBERG LIMESTONE. 



447 



feet, as given by H. P. Rogers. The thickness of that part of the Taconic system which is 

 supposed to correspond to it is not less than 22,000 feet thick. 



6. The Organic remains of the Taconic and lower Silurian Rocks are entirely different from 

 one another. " The species of fossils differ from the Silurian types ; that is, the species 

 are different, and they are not intermingled with the well known Silurian types, for of the 

 latter none are yet known, and this last fact(?) is a significant one. If the beds which 

 contain fossils contain none which are Silurian, what are we to infer, especially if this is a 

 general fact ; certainly, that if fossils are to have weight in determinations of this kind, 

 it goes strongly against the doctrine that the series is Silurian. If it is an established 

 doctrine that rocks which are separated in vertical space, and also in time, will be charac- 

 terized by different fossils, then that doctrine should govern our opinions. If we can 

 account for the absence of fossils in a fossiliferous series, on established principles, their 

 absence becomes of no account in questions of age ; but when the fact is general, and it 

 prevails for a thousand miles, it becomes significant. A fossil period will furnish fossils 

 somewhere on lines so extended and if on lines thus extended they are not found, then 

 we are justified in the belief that the period was not one of life and vitality." (American 

 Geology, Part II, pp. 121, 122.) 



UPPER HELDERBERG LIMESTONE. 



We describe under this head two belts of limestone ; one in Massachusetts, and the 

 other extending from Vermont into Canada, and exhibiting its peculiarities best out of 

 the limits of the State. 



Fis. 266. 



N.W 



Section in Bernardston, Mass. 



Explanation of Fig. 266. 



A Clay slate. 



B Quartz rock and quartzose conglomerate. 



C Quartz rock. 



D Clay slate. 



E Magnetic iron ore in F. 



F Encrinal limestone (Upper Hclderberg ?). 



G Clay slate. 



H Quartzose conglomerate. 

 I Quartz rock (slaty), dip west. 

 J Quartz rock, dipping east. 

 K Clay slate. 



The first deposit of limestone which we will notice is not located in Vermont, but is so 

 intimately connected with the continuation of rocks from Vermont, that it must be briefly 

 described. It is in Bernardston, Massachusetts. The clay slate of Vernon and Guilford, 

 when extended a few miles southerly, is associated with limestone, quartz rock, and mag- 

 netic iron ore. The limestone does not appear in Vermont ; but the overlying quartz rock 

 is developed in Vernon, immediately overlying the clay slate, unconformably, we suspect. 



