120 Igneous Origin of some Trap Rocks. 
ed the outline of similar districts in several countries in Europe, par- 
ticularly in Germany, Hungary and Italy. 
Analogies with Trap Rocks. 
These analogies are at this moment recalled, for the sake of intro- 
ducing the subject of the present notice. The trap rocks, it is well 
known, graduate in their mineralogical characters into the acknowl- 
edged lavas; and not only into those which are compact and sub- 
crystalline, but even into the vesicular ; and the columnar lavas also find 
their counterparts in the rocks of this family. In their geological po- 
sition too, there is great similarity. Lava currents observe no law 
but the law of the strongest; they burst forth, and they intrude, 
wherever the expansive power sufficiently impels them; and they 
flow over, or accumulate upon any and every species of rock and 
soil. The trap rocks are characterized by the same irregularity. 
We cannot say of any particular rocks, that they are the natural asso- 
ciates of the trap rocks; for the latter intrude among and repose 
upon granite and the other primitive rocks ; they are equally recog- 
nized among the transition rocks; and they are found with and over- 
lie the most recent, not excepting bituminous coal, and the tertiary; 
and even lignite, clay and gravel. They cut granite* and other 
primitive rocks in two with their dykes; and the sandstones,f lime- 
stones, and other rocks, are occasionally severed by the same kind 
of basaltic wall. 
Trap Regions of the United States. 
Those persons in this country to whom the name of trap is not fa- 
miliar, may still remember the conspicuous ridges, with perpendicular 
mural fronts, composed of rude columns, with sloping backs; and the 
isolated peaks and groups that divide the states of Connecticut and 
Massachusetts almost centrally in two; commencing in the East and 
West Rocks at New Haven and terminating on the borders of Ver- 
mont; and thus occupying a region which is one hundred and twenty 
miles long, and varies from three to twenty five miles in diameter. 
The Pallisados, on the Hudson, are perhaps still more familiar to 
our domestic tourists ; and it is well known that they cross the state 
of New Jersey, from the Hudson towards the Delaware. The cave 
ee ee a aliens Nan EN A Ge ed em eee 
* At Red Hill, Lake Winipiseogee, New Hampshire. 
+ In East Haven, two miles from New Haven. 
