376 The American Geologist. December, 1894 
sert, the crystalline limestones are simply the Cambrian met- 
amorphosed by intrusives. Such phenomena as those de- 
scribed are universally present where limestones (or other 
rocks such as schists or shales) have been locally metamor- 
phosed by intrusives. One of the best known examples of 
these relations is that at Cortlandt, N. Y., a short distance 
south of Peekskill. G. H. Williams* in describing- the con- 
tact here between the eruptive diorites and the limestone, says : 
The metamorphic action extends but a small distance from the actual 
contact, but is always unmistakable in its nature. The limestone is in 
almost all eases bleached and is frequently rendered more coarsely crys- 
talline. There are new contact minerals developed in it, among the 
most common of which are hornblende and pyroxene. 
Similar conditions are said by Nasonf to occur at the con- 
tact of the limestones and eruptive rocks near Franklin, N. J. 
No such relations occur between the diorites and limestones 
in the Jenny Jump area. The limestones are not more crys- 
talline at the contact with the eruptives than at a distance 
from them. The limestone is uniformly crystalline through- 
out. The accessory minerals, pyroxene, biotite, graphite, etc., 
are not found more abundantly near the contact than else- 
where. The limestone shows no change in crystalline char- 
acter, or in the abundance and character of accessory minerals, 
as the contact with the intrusive is approached. 
(2) There are bands of limestone occupying very consider- 
able areas, and everywhere of perfectly crystalline character, 
which nowhere show the presence of eruptive rocks. The 
uniformly crystalline character of the limestone over consid- 
erable areas is evidence that the metamorphism is not due to 
local intrusives. It was produced by some cause acting uni- 
formly over w T ide areas and resulting in regional as distin- 
guished from local metamorphism. 
The same relations are shown in the outcrops of crystalline 
limestone A to G as in the larger area at the northern end of 
the mountain. Eruptive rocks are of uncommon occurrence 
in the limestone outcrops along the eastern side of the moun- 
tain. At only one locality (B) was an eruptive rock seen in 
the limestone. Here a small dike of gabbro six inches in 
thickness was seen cutting the limestone, apparently in the 
*Am. Jour. Sci., Ill, vol xxxvi, 1888, p. 267. 
fAnn. Rept. Geol. Survey N. J., for 1890, p. '-VI, and elsewhere. 
