GNEISS, 
75 
CHAPTER III. 
STRATIFIED ROCKS. 
1. Gneiss. 
General considerations. — Contains beds of other rocks, as limestone and hornblende. —' 
Limits and extent. — Dip and strike of gneiss. —Mountain ranges composed of gneiss. — 
Gneiss as a mining rock. — Imbedded minerals, etc. 
Leaving for the present the consideration of the unstratified rocks, I proceed to speak of 
the relations and extent of those which are termed stratified ; in which group is gneiss, a 
rock occupying by far a greater surface than all the other stratified rocks in the Northern 
Division of the State. As its extent and relations will be better understood by tracing it 
beyond the limits of the Second Geological District, I shall commence at Little-Falls, the 
most southerly point of that mass of primary rocks which forms the greatest portion of the 
division to which I have just alluded. 
In the first place, it is necessary that I should observe, that gneiss is not continuous through¬ 
out the great extent of country whose borders I shall define. It is to be understood, that in 
addition to granite and limestone, the extent and relations of which have been pointed out, 
there are frequent interstratifications of hornblende, and a few beds of primitive limestone not 
yet noticed, as well as other rocks of minor extent. Leaving out of view the hypersthene 
and the stratified fossiliferous rocks, gneiss is the principal rock, and the one to which all others 
may be considered in a measure subordinate. Those imbedded masses, as in all the primary 
rocks, are very indistinctly defined, and not clearly limited; and besides being inconstant and 
irregular in their boundaries, they are exceedingly difficult to bound with that clearness which 
is desirable.* 
Commencing then as proposed at Little-Falls, the northwestern border of the gneiss may 
be quite distinctly traced, first in a northerly direction through Norway, Ohio, and the easterly 
* In addition to the above, it is proper to add, that in a great portion of the northern counties, the land surveys are so deficient 
in accuracy, and the landmarks so indifferent, that I had frequently no direct way for locating, with any degree of precision, many 
localities of rocks, and especially those which are limited to a small area. For this reason, I have omitted to notice many beds 
of granite and primary limestone, and of hornblende, which I have carefully examined, not discovering any thing important in 
connection with them. A great portion of the northern primary region appears composed, therefore, of one or two rocks. 
