220 J. D. Dana—Limestone Belts of Westchester Co., N. Y. 
micaceous and contain in addition more or less orthoclase. 
Silica, alumina, iron protoxide, magnesia, lime, soda, potash, 
are all the essential ingredients obtained in analyses of these 
various rocks (excluding the magnetite, apatite, pyrrhotite* and 
pyrite); and it is not mysterious, therefore, that such rocks 
should be among the results of metamorphism 
The title of this paper might, therefore, “a have been 
Soda-granite, noryte, dioryte, hornblendyte, pyroxenyte, and 
various chrysolitic — made through metamorphic agencies in 
one metamorphic proces 
The geologist will nowhere on the continent. find a more in- 
structive spot for a day’s walk than in the western portion of 
the Cortland region. Starting from Cruger’s Station (87 m. 
from New York City), a walk of half a mile brings him to the 
western brick-yard shed; going north from here by a wood 
road carries him along section 3, and in less than a mile in a 
northerly direction (passing brick- -yards at the end of it) he 
will reach Montrose Point and the chrysolitic rocks; follow- 
ing these around by the shore for about a mile he will then 
and chrysolite rocks together; a mile and a half more (pass- 
ing on Ae route the large Verplanck ice-house) will take him to 
caw gil in hee village of Verplanck, near the foot of which 
street, on shore, occur the limestone and its. associated 
augitic a Honibtendic rocks. Thus, in a distance of seven 
een he will see a wonderful diversity of rocks and facts. 
Possibly he may be convinced, at the end of the walk, that 
ro im 
rocks of Verplanck "Point northeas twat , and afterward extend 
his walks in other directions over the Cortland region, and he 
may see enough to satisfy himself finally that, although there 
has been fusion and some eruption, it was not eruption from 
the earth’s deeper recesses, like that which brought up trap 
(doleryte) en a series of great fissures for a thousand miles 
the Kastern Atlantic border, from the Carolinas to Nova 
Scotia, all of it fe of one kind essentially, but eruption from 
less depths, not greater than the lower limits of a series of 
formations that were subjected together to foldings, fractures, 
and metamorphic change, and mostly far short of this. 
The next subject is the distribution of the limestone areas 
of the county. 
* Pyrrhotite is the common iron sulphide of the norytes, hornblendyte, pyrox- 
enyte and chrysolitic rocks, and it is — also in the mica schist that occurs 
interstratified with the Verplane ‘+k limesto 
[To be continued.] 
