62 The Rev. D. Williams on the Geology of Devon ^ CornvoalL 
to the other, ^ve have nothing more than one great wave (of 
probably some far extended undulation) consisting simply of 
two convex arcs inclosing a central trough, apparently the 
result of the same system of forces acting on a vast floor of 
matter, successively and regularly accumulated ; either an 
overlying mass, or a fractured section of an original continua- 
tion of the Cambrian and Silurian deposits ; for if we compare 
the precipitous and vertical cliffs of Nos. 2, 3, 4 and* 5, of 
Exmoor (in echellon arrangement beetling over the deep tide 
way of the Bristol Channel) with the carboniferous limestone 
and secondary rocks of the opposite coast of Wales, we have 
all the evidences of an enormous fault. 
But what are the results if we compare the positive testi- 
mony afforded by gradation, alternation, succession, and con- 
formable supraposition, with that afforded by organic re- 
mains? The Petherwin fossils near Launceston, and those 
of the coral limestones of South Devon, I include without 
doubt or hesitation in a lower horizon, or subdivision of the 
floriferous series. No. 9, above the Posidonia limestones ; so 
that if we suppose the ratio of extinction of vegetable species 
not to have been governed by the causes which effected that 
of marine zoophyta and testacea, the exceptions afforded by 
the Posidonia limestones are but as dust in the balance of or- 
ganic evidence ; and in this respect alone, geologists will in- 
volve themselves in inextricable difficulties and contradictions, 
if they reject the maximum and rely on the minimum amount 
of organic evidence. I repeat the fact, that the lower flori- 
ferous, and Coddon Hill grit series are overlaid in the south 
by the slates of Cornwall, which comprise in their ascending 
terms, first, the St. Germans, and lastly, the Plymouth lime- 
stones ; so that it appears to me, that the great consecutive 
series from No. 2 to 10, evidences a transition of organic type, 
in progress, as it were, from the grauwacke towar'ds the car- 
boniferous limestone; that the latter, or its coal-field, is not 
represented here at all, but that the coarse slaty and red 
arenaceous beds which overlie the Plymouth limestones, ex- 
tending thence to Rame Head on the south, probably do ap- 
pertain to the early period of the Old Red Sandstone pro- 
per. 
The relations of the floriferous. No. 9, to the coral lime- 
stones, and killas. No. 10, are explained with the greatest 
clearness and simplicity at and around Chudleigh ; to aid my 
brief description 1 refer your readers to the accurate and 
faithful sections of Mr. De la Beche. (See Report, Plate IV. 
fig. 7 and 8). But why that able observer should assign a 
different position to the many other groups of coral limestone 
