80 
Table of the more important Igneous Rocks, Strata, anti 
other Deposits of South Devon. 
X Igneous Rocks, upheaved at different 
GRANITE, 
SERPENTINE, 
SCHORL ROCK, 
HORNBLENDE,' 
AND OTHER 
TRAPP ROCKS, j 
J 
periods. They existed probably in a some¬ 
what similar form in the interior of the 
earth prior to their elevation, and it is also 
national to think, that some portion of them 
or their modifications, have had their pre¬ 
sent elevation from some more ancient eera, 
or even ab initio. This class of rocks is 
termed by many geologists “ Primitive 
Formations .” 
LIME, 
SLATE, 
SANDSTONE. 
Rocks of the Transition or Greywacke 
group, and so far as the south-west of Devon 
is concerned, apparently coevally deposited. 
The source of the substances of which they 
'are constituted is very problematical, but, 
though the immediate derivation from prior 
existing rocks is questionable in respect of 
the lime and slate, it is hardly so in regard 
of the sandstones. 
CLAY. 
ACCUMULATIONS \ 
OF FRAGMENTS 
OF ROCK, 
PEBBLES, 
SAND, &C. 
Substances formed or removed to their 
present sites apparently by the passage of 
a vast current of water over the land, but, 
having no solidifying power on the disin¬ 
tegrated particles, or severed and transported 
portions of rock. The clay may possibly 
have been derived from the argillaceous 
formations previously existing. Aggregately 
these substances are called “ Diluvium .” 
I have omitted the mention of gneiss, porphyry, 
greywacke rock, and various other modifications of 
the above characteristic or typical strata, these 
being considered elsewhere. In the above table 
also, I have not included the sandstones and con¬ 
glomerates of the south-east of Devon, respecting 
the formation of which, there appears some peculi¬ 
arity, and to which perhaps the above remarks do 
not apply. 
