378 The American Geologist. December, 1894 
evidences of their contemporaneity. The belt of limestone 
outcrops along the middle of the mountain (A-E) is nowhere 
in contact with the blue limestone; on the contrary, wherever 
the rocks adjacent to the limestone on either side appear they 
are granitoid gneisses. 
At the northern end of the mountain the crystalline lime- 
stones occupy a distinct area, and no outcrops of blue lime- 
stone are known within that area. North of the northern end 
of this area, however, blue limestone occurs at H (see map), 
not over two hundred feet from the crystalline limestone. 
The blue limestone here is the typical fine-grained blue lime- 
stone which outcrops further west in Kittatinny valley. The 
crystalline limestone is in part characteristic for that rock, 
and in part a local variety (pyroxene-rock or quartz-rock) 
frequent^ found associated with the limestone. There are 
no eruptive rocks cutting the crystalline limestone here. The 
two outcrops are perfectly characteristic of their respective 
varieties, and there is no tendency in either toward gradation 
into the other. It seems hardly possible that the passage 
should not show in this locality, if there is a gradation be- 
tween the two rocks, for they are separated by less than two 
hundred feet. The crystalline limestones of Jenny Jump 
mountain are in all eases sharply distinct from the blue 
Cambrian limestones ; and at the locality where the two occur 
nearest together, there is no gradation in lithological charac- 
ter between them. 
Conclusion. In conclusion, the crystalline limestones of 
Warren county are believed to be distinct from and older than 
the blue magnesian limestone of Cambrian age which occurs 
along the northwestern side of the New Jersey highlands. 
They are believed to be distinct for the following reasons: 
first, they have a well developed crystalline character, and 
they hold large quantities of accessory metamorphic minerals; 
second, they show no intimate association in areal distribu- 
tion with the blue Cambrian limestone ; third, they show no 
tendency to grade into blue limestone. They are believed to 
be older, because, first, they have been subjected to general 
metamorphic forces resulting in great changes, of which the 
neighboring blue limestones show no trace; second, they oe- 
