CARBONIFEROUS VOLCANIC ROCKS. 
545 
formed of rolled pieces of the same serpentinous trap, which 
appear in the dikes above alluded to. 
Period of Oolite and Lias. — Although the green and ser¬ 
pentinous trap-rocks of the Morea belong chiefly to the Cre¬ 
taceous era, as before mentioned, yet it seems that some erup¬ 
tions of similar rocks began during the Oolitic period and 
it is probable that a large part of the trappean masses, called 
ophiolites in the Apennines, and associated with the lime¬ 
stone of that chain, are of corresponding age. 
Trap of the New Red Sandstone Period. — In the southern 
part of Devonshire, trappean rocks are associated with New 
Red Sandstone, and, according to Sir H. De la Beche, have 
not been intruded subsequently into the sandstone, but were 
produced by contemporaneous volcanic action. Some beds 
of grit, mingled with ordinary red marl, resemble sands 
ejected from a.crater; and in the stratified conglomerates 
occurring near Tiverton are many angular fragments of trap 
porphyry, some of them one or two tons in weight, intermin¬ 
gled with pebbles of other rocks. These angular fragments 
were probably thrown out from volcanic vents, and fell upon 
sedimentary matter then in the course of deposition.f 
Trap of the Permian Period. —The recent investigations of 
Mr. Archibald Geikie in Ayrshire have shown that some of 
the volcanic rocks in that county are of Permian age, and it 
appears highly probable that the u 2 :>permost portion of Ar¬ 
thur’s Seat in the suburbs of Edinburgh marks the site of an 
eruption of the same era. 
Trap of the Carboniferous Period. —Two classes of contem¬ 
poraneous trap-rocks occur in the coal-field of the Forth, in 
Scotland. The newest of these, connected with the higher 
series of coal-measures, is well exhibited along the shores of 
the Forth, in Fifeshire, where they consist of basalt with 
olivine, amygdaloid, greenstone, wacke, and tufi*. They ap¬ 
pear to have been erupted while the sedimentary strata were 
in a horizontal position, and to have suffered the same dislo¬ 
cations which those strata have subsequently undergone. In 
the volcanic tuffs of this age are found not only fragments 
of limestone, shale, flinty slate, and sandstone, but also pieces 
of coal. The other or older class of carboniferous traps are 
traced along the south margin of Stratheden, and constitute 
a ridge parallel with the Ochils, and extending from Stirling 
to near St. Andrews. They consist almost exclusively of 
greenstone, becoming, in a few instances, earthy and amyg- 
daloidal. They are regularly interstratified with the sand- 
* Boblaye and Virlet, Morea, p. 23. 
t De la Beche, Geol. Proceedings, vol. ii., p. 198. 
