Limestone Belts of Westchester County, N. Y. 219 
noryte above as well as below it. The quartzyte looks some- 
what like a pale quartzose porphyritic granite; but, as observed 
in thin slices, the quartz consists of aggregated grains like 
sandstone; showing a resemblance to the Peekskill quartzyte. 
The feldspar is mainly orthoclase. 
C. CONCLUSIONS AS TO THE CORTLAND ROCKS. 
Many more observed facts might be here reported. But the 
above appear to be sufficient to settle the question as to the re- 
lations of the rocks of the Cortland series. They appear to 
sustain fully the following conclusions : 
(1) These rocks, although they include soda-granite, noryte, 
augite-noryte, dioryte, hornblendyte, pyroxenyte, and chryso- 
f 
v 
litic kinds, are not independent igneous rocks erupted from 
great depths. 
_ (2) However complete their former state of fusion or plas- 
ticity may have in some cases been, they are metamorphic in 
(They are younger rocks if of different age, since they con- 
tain and intersect portions of the Verplanck limestone.) 
(4) These Cortland rocks differ from the other Westchester 
County rocks because the metamorphic process had to do with 
sedimentary beds that differed in constitution or were in some 
respects under different conditions from those that existed else- 
where. 
On the view reached, it follows that the limestones, schists, 
and other rocks of the Cortland region originally constituted 
together one series of horizontal strata. They underwent an 
upturning through subterranean movements, and in the course 
of it, they became metamorphosed ; part into mica schist and 
gneiss, part, by loss of bedding, into the massive rocks. The 
number of these rocks does not imply widely different ingre- 
dients in the original strata. For hornblendyte and pyroxen- 
yte have the same chemical constitution ; the chrysolitic rocks 
contain no ingredient not in them also, and are peculiar mainly 
in their less proportion of silica. Moreover, the dioryte, noryte 
and augite-noryte are alike in containing the same bases in 
nearly the same proportions. The soda-granite differs in 
chemical constituents only through its mica, which indicates 
the présence of potash; but the other rocks also are often 
