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. — hnbedded minerals, etc. 



Leaving for the present the consideration of the imstratified rocks, I proceed to speak of 

 the relations and extent of those whicli 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 wliich 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, Oliio, and the easterly 



* In addition to the above, it is proper to add, lliat in a great portion of the northern counties, the land surveys are so deficient 

 in accuracy, and the landmarlts so indifferent, that I had frequently no direct way for locating, with any degree of precision, many 

 localities of rocks, and especially those which arc limited to a small area. For this reason, I have omitted to notice many hed* 

 of "ranite 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. 



