464 
GEOLOGY OF THE FIRST DISTRICT. 
Berkshire county in Massachusetts. In tracing the superposition of the rocks in Essex 
county, from the Potsdam sandstone, which rests on the Primary rocks, he run his section 
across Lake Champlain into Vermont. Describing his section,* he says, “Now the most 
important fact in this section, is the position of the last member of the group, the grey lime¬ 
stone. It is a stratum which, in Berkshire county and other parts of the country, has gene¬ 
rally been placed, among the primary rocks ; it is identical with the limestone at the base of 
Saddle mountain, and which covers more or less of the western flank of the Green moun¬ 
tains. As yet ] have not been able to find any very distinctive difference between it and the 
white and grey marbles along the whole range just mentioned. No one has ever doubted the 
primary character of these marbles ; yet, if the preceding views are correct, will they not 
have to be removed into the transition class ? That there is a well marked difference between 
the marbles and what I have in another place described as the true primary limestone, I 
cannot doubt.t The whole matter evidently requires a reexamination ; and if the above 
remarks lead only to this result, I shall be repaid the labor of all the attention I have bestowed 
upon them, though other opinions than those expressed above are finally adopted.”* 
Prof. Hitchcock has traced the connection of the granular quartz rock, in patches highly 
inclined, with gneiss, mica slate, talc slate, argillite and limestone,^; the dolomitization of 
the limestone, and the almost constant intervention of the mica slate between the dolomite 
and talc slate.§ This intervention he attributes, it is believed justly, to the limestone absorb¬ 
ing the magnesia from the talc,|l while subject to metamorphic agency. 
Prof. Hitchcock has also shown that the white crystalline limestone of Bernardston, Mas¬ 
sachusetts, contains fossil remains. Quartz rock overlies, and argillaceous slate underlies 
the limestone, though the contact was not seen.H The slate and limestone in this range of 
rock extending into Vermont, are very similar to the corresponding rocks in New-York and 
Massachusetts. 
After reviewing all the facts observed both by others and myself, I have been led to the 
conclusion, that the limestones that are frequently crystalline, white and variegated marbles 
in the western parts of Vermont, Massachusetts and Connecticut, and in the eastern part of 
New-York, from Mount Washington to the city of New-York (that have been described in 
this chapter), are metamorphic rocks ; that they were originally the Mohawk limestone and 
Calciferous sandstone, and that the associated rocks were originally the Potsdam sandstone 
and the slate rocks of the Hudson valley; that they were, in fact, the rocks of the Champlain 
division, hut much more altered and modified by metamorphic agency than the Taconic 
rocks. 
* Vide Second Annual Geological Report of New-York, 1838, p. 232. 
t The “ true primary limestone” here alluded to, is the same that forms the second class of Metamorphic limestones in this 
volume, and which is next to be described as the metamorphic limestones of the Highlands and west of the Hudson, and of 
Washington county. 
t Final Geological Report of Massachusetts, 1841, p. 589. § Ibid. p. 573. 11 Ibid. p. 582, 584. U Ibid. p. 5G0, 561. 
