CHAP. XXXII 
DEVONSHIRE 
97 
The geographical conditions in which the red rocks of Devonshire 
accumulated were those so characteristic of the Permian and Trias 
formations throughout Britain. The red sandstones and sandy marls 
gathered in inland basins, where the water seems to have become too 
saline and bitter to support animal life. The strata are consequently 
singularly devoid of organic remains. The climate was probably arid, 
and the absence or scarcity of traces of terrestrial vegetation indicates 
that the land around the water-basins stretched in wide sandy and rocky 
wastes. In the dry atmosphere and under the influence of rapid radiation 
the cliffs and crags of Culm-measures would disintegrate into angular rubbish, 
and this material, slipping into the lakes or washed down by occasional rain- 
storms, forms now the breccias that constitute so typical a feature in the 
Permian system. 
It was while this geographical type continued in the South-west of 
Fig. 228. — Section at Belvedere, S.W. of Exeter. 
a, Culm-measures ; b, breccia and marls ; c, lavas ; d, red pebbly sandstones. 
England that the volcanic eruptions took place which we are now considering. 
Ee la Beehe correctly referred these eruptions to the early part of the red 
sandstone series. A brief examination of the ground suffices to show that 
although, as he pointed out, the volcanic rocks lie towards the base of that 
series, as shown in Fig. 228, they do not all occupy the same platform. That 
111 some cases the lavas lie directly on the Culm-measures, while in others 
t ui}' are separated from these strata by 100 feet or more of red sandstones 
and breccias (Fig. 229), would not in itself be proof of any difference of 
Fig. 229.— Diagram to show the unconformability and overlap of the Permian rooks 
in the Creditou Valley. 
Culm -measures ; i>, breccias ami sandstones ; c, lava-group ; rf, breccias with fragments of lava 
passing up into sandstones and marls (c). 
fP p stratigraphical position in the igneous rocks, for the floor on which 
le ermian formations were here laid down can be shown to have been 
an j^ r- Ussher informs me that in the quarry the visible exposure of the acid rock is surrounded 
overed by mica-porphyrite, probably andesite. 
VOL II. 
II 
