PRE-CAMBRIAN NORTH AMERICAN LITERATURE 305 
3. A series of crystalline limestones and quartzites, together with certain 
gneisses usually found associated with them. In these rocks the granulated 
structure is very subordinate or entirely absent. They are characterized by 
a very extensive recrystallization with the development of new minerals. 
These minerals have crystallized under the influence of the pressure which 
granulated the gneisses of the second class, and are not in any marked man- 
ner deformed by it. These gneisses also differ from the granites and gneisses 
of classes 1 and 2 in chemical composition, giving analyses almost identical 
with those of slates. Moreover, the rocks of this class are very frequently 
graphitic, and analyses show that the gneisses correspond in chemical com- 
position more closely with slates than with granites. 
4. Pyroxene-gneisses, pyroxene-granulites, and allied rocks whose origin 
is as yet doubtful. 
With regard to the Grenville series, from the presence of numerous and 
heavy beds of limestone and quartzite, their prevalent banded character, the 
widespread occurrence of graphite, and the fact that the gneisses associated 
with the limestones and quartzites have the composition of sands and muds 
and not of igneous rocks, it is concluded that it is extremely probable that 
this is an altered sedimentary series, which has been deeply buried, invaded 
by great masses of igneous rocks, and recrystallized. In places the Gren- 
ville sediments may have been mingled with the igneous rocks by actual 
fusion. 
Sinnyydige (Ce els | pte describes the crystalline limestones and associated rocks 
of the northwestern Adirondack region. The limestones, instead of being in 
limited patches as in the eastern part of the Adirondacks, are in extended belts 
many square miles in area. The limestone belt running through the town- 
ships of Rossie and Gouverneur has been traced more than twenty miles along 
the strike, while the average width is perhaps six miles. A narrower belt 
extends across Fowler into Edwards township. A third belt crosses the town- 
ships of Diana and Pitcairn, with an average width of two or three miles. 
In addition to these belts, numerous scattered patches have been noted in the 
western Adirondacks. 
The limestones are highly crystalline, coarse, light gray or white rocks, 
containing silicates in separate crystals or segregated in lumps. Among 
these phlogopite, graphite, pyroxene, and tourmaline are most common. The 
limestone is usually so massive that it is difficult to ascertain the strike and 
dip with any accuracy. When observable, the strike is generally northeast 
and the dip northwest, though exceptions are common. Garnetiferous and 
micaceous gneisses and pyroxenic and hornblendic gneisses are intimately 
associated with the limestone. The former are in some cases distinctly inter- 
‘Crystalline Limestones and Associated Rocks of the Northwestern Adirondack 
Region, by C. H.Smyvu, Jr. Bull. Geol. Soc. of Am., Vol. VI., 1895, pp. 263-284. 
