PENGELLT — ON THE AGE OF THE DAETMOOR GEANITES. 17 
Dr. Daubeny pointed out to mc certain pebbles, which he thouglit 
granite, in the red conglomerate at Livermead, in Torbay ; my own im- 
pression, however, is, that they are trap. I do not, of course, sup- 
pose that my opinion would be of any value when opposed to that of 
the eminent man just named, especially on a point of this kind. I 
merely mention the fact, to show that I have not allowed a strong 
bias, supposing me to have one, to overrule my judgment ; or I should 
have quoted the Livermead pebbles as granitic, on Dr. Daubeny 's 
authority. 
But waiving this point, I cannot regard it as certain that the red 
rocks of Torbay and of the South Devon coast generally are entirely 
destitute of Dartmoor detritus. Every one who has paid attention 
to the sandstones there, must be well aware that in many cases they 
are eminently micaceous ; this is very noticeable at the Corbous and 
Livermead ITead, in Torbay, where every newly exj)osed surface 
glistens with an almost metallic glance, from the presence of nume- 
rous large scales of black mica; doubtless a result of the destruction 
of a largo amount of pre-existing rock, of which mica was a consti- 
tuent. It is, no doubt, true that certain gritty members of the older 
rocks of the county sometimes contain scales of mica ; it seems im- 
possible, however, that these can have been the source of those found 
in the lied Sandstone, for, so far as 1 am aware, they are, in the first 
place, always small instead of large ; and, in the second place, in- 
variably white instead of black. On the other hand, in a passage 
already quoted from Sir H. De la Beche's " Keport," it is stated that 
the mica of tlie Dartmoor granite is sometimes black. Kor is it 
difficult to understand that whilst pebbles and boulders might be 
unable to force a passage to what is now the South Devon seaboard, 
comparatively small thin flakes of mica succeeded in accomplishing 
the journey. The fact, however, that nodules of micaceous trap occur 
in the conglomerate, renders it manifestly unsafe to insist on the 
granitic derivation of the scales in the sandstone. 
If it be true that granite pebbles occur at Sampford Courtney, 
North Tawton and Haldon, but do not exist on the southeuii coast 
of the county, — in other words on the north and north-east, but not 
on the east, of Dartmoor, — may we not have, in this fact, an indication 
of the prevailing direction of the most powerful currents, or other 
agents of transportation, in this part of modern Devonshire during 
the Eed Sandstone era ? 
The following appears to be a strikingly parallel case. The low- 
plain known as Bovey Heathfield, in Devonshire, is covered with a 
very coarse gravel, and surrounded, on almost every side, by hills of 
considerable elevation ; on the north and west the granite heights of 
Dartmoor, fringed with traps and metamorphic rocks ; on the north- 
east and east the greensand hills of the llaldons, capped with vast 
accumulations of flint and chert; and on the south a range of hills, 
extending from Newton towards Ashburton, consisting of Devonian 
limestone and associated rocks. The Bovey gravel consists almost 
entirely of Dartmoor material, a flint or chert fragment occurring 
VOL. TI. D 
