358 GEORGIA GEOUP. 



extending from Milton to Starksboro. Reasons are presented elsewhere for supposing 

 that other bands of clay slate in the State may be of the same age. 



We use the term Georgia Group to designate this terrain, from the town of Georgia 

 in Franklin County, where it is developed in its full proportions, and where the most 

 interesting fossils have been found. It is a name also which does not involve any theory, 

 and may be used by both parties in the controversy respecting its age. 



The name of Georgia Group or Georgia date is given to this group of rocks rather than 

 any other, such as FairJiaven slate or Castleton slate, because it is a purely geological 

 designation, and has no reference to the economical value of the slate. Two reasons 

 may be given for the preference of Georgia : 1. The whole of the group is developed in 

 the town of Georgia, but is not in either of the others mentioned. It is a rule of 

 geological nomenclature, that the whole series of rocks must be developed in the town, 

 mountain, or along the river, from which the name is derived. 2. Nowhere but in 

 Georgia, in Vermont, are the characteristic fossils of the group displayed. They have 

 as yet been found only in the New York portion of the southern terrain. The 

 geological character of the group is best developed in Georgia, and we are therefore 

 compelled to use the name of this town in describing the slates geologically. 



Lithological Characters. 



The Georgia slate includes all the following varieties of rock : 



1. Clay slate. 



2. Eoofing slate. 



3. Clay slate, approximating to micaceous sandstone. 



4. Various kinds of limestone. 



5. Brecciated limestone. 



6. Conglomerate, composed of pebbles of lynestone. 



The Georgia slate includes what Prof. Emmons has ranked as the black slate, Taconic 

 slate, and roofing slate ; and yet not altogether, for we have regarded all the black slate be- 

 neath the red sandrock as belonging to the Hudson River Group. The characteristic tril- 

 obites of the Georgia slate are represented by Emmons in his Taconic System, 1844, as found 

 in the black slate. The color of this variety seems to be due to the presence of carbon- 

 aceous matter. The Taconic slate is described " as an even-bedded aluminous slate, vary- 

 ing from the finest possible grit to one that is coarse and rather uneven-bedded, and 

 passing into a rock having many of the characteristics of a sandstone. We include both 

 these varieties under the general term of clay slate, which is the most prominent member 

 of the Georgia slate throughout the State. 



The roofing slate, or that variety of clay slate which is sufficiently fine and compact to 

 be used for roofing purposes, may be distinguished in general from the Hudson River 

 slates in Vermont by the absence of any calcareous matter. Yet this is not an infallible 

 character, because in the west part of Rutland County, and in a large part of Chittenden 

 County, upon the third or eastern range of this slate, there is a small percentage of car- 

 bonate of lime present. This is noticeable in the slate at Hubbell's Falls at Essex 

 Junction, where the rock may possibly have derived this element of its composition from 

 an adjacent limerock. Some parts of the Hudson River slates, too, contain no carbonate 

 of lime. 



