BASALTIC ROCKS. 
275 
cing at Piuckemin, and running near the towns of 
Springfield and Patterson, approaching the primary 
region near Pompton. The rock varies from a fine- 
grained, compact basaltic trap to coarsely-crystal- 
lized greenstone, and contains, besides its essential 
components, hornUende, feldspar^ and augite, vari- 
ous mineral ingredients, such as epidote^ prehnite^ zeo- 
lite^ stitbite, analcime, and datholite. The trap rocks 
of New-Jersey evidently repose upon the general 
sandstone strata of the country, as may be ascer- 
tained by viewing the eastern base of the Pali- 
sades skirting the Hudson, or the bed of the Passaic 
River below the Falls at Patterson, or the Newark 
Mountains. " From what is now universally ad- 
mitted," says Professor Rogers,* " concerning the 
igneous origin of trap, it is plain that over this por- 
tion of territory it has burst up in a molten state 
through a series of nearly parallel fissures in the 
strata, and after their consolidation and subsequent 
difiturbance, which caused them to dip towards the 
northwest, and has overspread their adjacent por- 
tions without eff"ecting any material change in their 
stratification, and producing only certain modifica- 
tions in their mineral contents and structure." In 
some of the cliff's at Patterson, the greenstone as- 
sumes a columnar structure ; and between it and the 
sandstone on which it reposes, we find an interme- 
diate rock of six or eight feet in thickness, resem- 
bling toadstone or amygdaloid, holding nodular crys- 
tals of several minerals, prehnite^ analcime^ k,Q,. Be- 
neath this, a layer of the sandstone of a few inches 
thickness exhibits a baked appearance, and is ful[ 
of small vesicular cavities, as if produced by the 
extrication of some gaseous matter or steam. The 
same appearances are common in the trap rock 
near New-Haven. 
Trap rocks also occur in the State of Maine, 
* Geol. Survey of New-Jersey. 
