G. H. Williams—Norites of the “Cortlandt Series.” 191 
Art. XXII.—TZhe WNorites of the ‘ Cortlandt Series” on. the 
Hudson River near Peekskill, N.Y.; by G. H. WILLIAMs. 
[Continued from page 144.] 
3. Mica Norite. 
The purest types of this rock are to be found in the eastern 
part of Cortlandt Township, along the road leading from Mon- 
trose Station (Munger’s Corners) to Montrose Point on the river. 
Nos. 40, 41, 49, 51 and 52 and a slide marked Mt. 9 in Prof. 
Dana’s collection were obtained along the section described in 
detail in Prof. Dana’s paper and adduced by him as evidence of 
the metamorphic origin of the rocks from sedimentary deposits.* 
The microscopic studv of these slides is therefore important 
with reference to the light which it may throw upon this ques- 
tion. 
This section, which occurs just at the residence of Mr. Butler 
(1883), has been called by the writer the ‘ Butler Section” 
(see above). Professor Dana gives a profile of it and says (p. 
218): “It consists mainly of noryte and augite-noryte, but with 
some hornblendyte and noryte-gneiss and has distinct planes of bed- 
ding in several places, all of which are conformable to one another. 
.... This ledge, although made up of massive noryte and 
augite-noryte, bears thus positive evidence of its having once 
had bedding throughout, and affords thereby a demonstration 
that its noryte is of metamorphic origin and that the associated 
beds comprised also the limestone of the region.” + 
The specimens 41 (c), 47 (9), 49 (e), 51 (c)t and 52 are identi- 
cal in structure and composition, except in so far as they con- 
tain different proportions of biotite. They consist of aggre- 
gates of magnetite, hypersthene and biotite which are curiously 
bent and twisted around larger areas of feldspar, so as to form 
a pronounced ‘“ microflaser” structure. The feldspar too shows 
to a remarkable degree both mechanical and-optical deforma- 
tion. Its crystals are bent or broken; secondary twinning 
lamellz have been abundantly produced by strain, and the 
extinction is very uneven. Moreover portions of the areas are 
frequently seen to be broken up into the peculiar mosaic which 
both Lehmann§ and Lossen|| have shown to be a characteristic. 
result of pressure. Then again garnet, a mineral well known 
to be the product of dislocation metamorphism in rocks, is here 
abundant in some of the most schistose bands, notably Nos. 
51 and 52. 
* This Journal, September, 1880, xx, p. 218. 
+ The italics are those of Professor Dana. eye 
¢ These letters in parentheses are those used by Professor: Dana to designate 
particular beds in his section. 
$ Ueber die Entstehung der altkrystallinen Schiefergesteine. Bonn, 1884. 
|| Jahrbuch der kon. preuss. geolog. Landesanstalt fiir 1883. Berlin, 1884. 
s 
