226 
soon afterwards applied this new arrangement not only to the groups 
of Devonshire originally under review, but with a boldness which 
does credit to their sagacity, extended it to the whole of the slaty 
and calciferous strata of Cornwall, till then known only as grau- 
wacke, clay-slate, or killas; assigning to those strata, likewise, the 
date of the old red sandstone, and resting this determination entirely 
on the character of the fossils. This change—the greatest ever 
made at one time in the classification of our English formations— 
was announced in a memoir read before the Geological Society in 
April 1839; the authors then also proposing for the whole séries 
(including both the old red sandstones of Herefordshire, and the 
fossiliferous slates and limestones of South Devon and Cornwall,) the 
new name of “the Devonian system,” and expressing their belief, 
that many of the groups hitherto called grauwacke, in other parts 
ot the British Islands and on the continent, would ere long be re- 
ferred to the same geological epoch. 
The proposed alteration, therefore, will terminate the perplexity 
hitherto arising from the circumstance, that the o/d red sandstone of 
Werner has been frequently confounded with the new red sandstone 
formation of English geologists. It also explains the cause of the 
English old red sandstone having been rarely recognised on the 
continent :—for if the Devonian slates afford the normal type of 
this formation, whilst the marly sandstones and conglomerates of 
Herefordshire are abnormal exceptions in it, we see the reason why 
their slaty continental equivalents, like the greater part of the South 
Devon slates, have been referred to the undivided Wernerian forma- 
tion of grauwacke. 
Mr. Austen, in a communication relating to the structure of the 
south of Devon, has identified the caleareous slate and limestone 
of the south of Cornwall with the limestones of this district, and con- 
siders that of Torbay among the newest deposits in the latter series. 
sandstone—entirely distinct as to form and species—are as unlike those 
of the Silurian system, as they are to those of the overlying carboniferous 
system :’ adding, “that he has no doubt, although at present unprovided 
with geological links to connect the whole series, that such proofs will 
be hereafter discovered, and that we shall then see in them as perfect evi- 
dence of a transition between the old red sandstone and carboniferous 
rocks, as we now trace from the Cambrian, through the Silurian, into the 
old red system.”’—See Silurian System, p. 585, line 22, e¢ seq. 
