370 Story of the Mississijojpi-Missouri .— Claypole. 
states into Canada and to the Polar sea, near the mouth of 
the Mackenzie river. This area includes the whole of the 
basin of the Missouri which river therefore we have already 
said had then no existence. In this sea the beds of the Trias- 
sic, Jurassic and Cretaceous ages were laid down, and it must 
therefore have continued perhaps with minor changes during 
the entire mesozoic era. All this time it is nearly certain that 
the older river continued the even tenor of its way through 
ages that witnessed great and striking events in geologi¬ 
cal history. In this interval occurred the outbreak of the vol¬ 
canoes of Pennsylvania which have covered with their ashes 
large areas in the southeast part of that state and have inter¬ 
sected with dykes of dolerite the Triassic strata of that and of 
the adjoining region. The Atlantic seaboard has probably 
never experienced so violent and extensive an outburst. The 
outflows of lava reached from Nova Scotia to Carolina, a dis¬ 
tance of more than a thousand miles, and the products of the 
eruption—the traps—are of the same nature over all this 
great length of country. Then it w T as that some of the most 
striking features of the scenery of the eastern states were 
rendered possible. Then flowed out the masses of igenous rock 
of which Mt. Tom and Mt. Holyoke in Massachusetts are 
composed. Then came from the interior of the earth the basalt 
of the Hanging Hills near Meriden, Bergen Hill in New Jersey 
and last though by no means least in this region the famed 
and beautiful columnar palisades of the Hudson. All these are 
bosses of hard trap-rock capable of resisting the action of the 
weather and exposed by the erosion of the softer material un¬ 
der which they formerly lay buried. 
The volcanic action and the outflow of trap were not con¬ 
fined to the spots already indicated. Further to the north 
there were vast eruptions in New England and in Nova Scotia. 
All along the valley of the Connecticut the edges of the lava 
beds can be seen and on the shores of the bay of Fundy lies a 
massive sheet of basalt well seen in the red and commanding 
bluffs of cape Blomidon on the bay of Mines. 
Southward again extended the region of volcanic action and 
the Triassic strata of Pennsylvania and of Virginia are cut in 
all directions by basaltic walls and sheets of igneous rock. 
The now sadly memorable features of the desperate and de¬ 
cisive battle-field of Gettysburg are consequences of those dis- 
