12 
THE GEOLOGIST. 
It has long been known that the age of the granitic rocks of Dart- 
moor can be safely limited on the side of antiquity. That they are 
less ancient than the culmiferous beds of North and Central Devon 
has been established on satisfactory evidence produced by various 
observers. 
Sir Henry De la Beche, in his ' Eeport,' says, " The intrusion of 
the Dartmoor mass was certainly after the deposit of the carbo- 
naceous series of North Devon, be the age of that series what it may ; 
it thrusts the southern portion of this series northwards to Oak- 
hampton, cuts oif the ends of trappean bands and of associated beds 
of grit and shale near Cristow and Bridford, and sends veins into it 
in the valley of the Dart, at the junction of the two masses of rock." * 
Professor Sedgwick and Sir E. I. Murchison, in their paper on 
"The Physical Structure and Older Stratified Deposits of Devon- 
shire," say, " Granite veins, passing from the central mass into the 
superimposed stratified rocks, are found on all sides of Dartmoor. 
"We have seen them above Ivybridge, injected amongst the oldest 
slates of Devonshire ; and near Oakham pton we have seen them in 
like manner, penetrating the culm-measures ; and they are finely ex- 
posed in the beautiful gorges of the Teign and the Dart, where those 
rivers descend from the granite to the culmiferous series. These ex- 
amples, to which we could add many more, are sufficient for our pur- 
pose. Now these veins, taken in general, are mere prolongations of 
the central granite, inseparable from it, and contemporaneous with 
it; they cannot therefore (as the granite is one mass) be contempo- 
raneous with stratified rocks of diflferent ages. Consequently they 
are true veins of injection, and the granite was protruded at a time 
posterior to all the other stratified systems." f In another part of 
the same paper these authors go on to say, " It appears that the rocks 
of Devon and Cornwall belong to three periods of formation. The 
oldest includes the various groups of slate rocks, and at least a part 
of the associated traps. The next includes the culm series, the upper 
division of which contains fossils identical with those in the upper 
division of the coal measures. The granite belongs to the newest 
period. "J 
Mr. Godwin-Austen, in his paper on " The Geology of the South- 
East of Devonshire," speaks of similar granite veins, and, in a some- 
what qualified manner, confirms the opinion of the authors just quoted 
respecting the chronology of the granite ; stating that " The observa- 
tion of Professor Sedgwick and Mr. Murchison, above quoted, as to 
the age of the Dartmoor granite, applies necessarily to the schorly 
portion alone, which comes in contact with sedimentary deposits, for 
the entire mass is not of the same age." He then gives a figure of a 
section, " showing the manner in which the usual porphyritic granite 
has intruded itself among such as had already become compact and 
jointed, and containing schorl," and adds, " Again, this porphyritic 
* 'Report on the Geology of Cornwall, Devon, etc.,' p. 165. 
t Geol. Trans., 2nd series, vol. v. part iii. p. 686. 
X Geol. Traus., 2ud series, vol. v. part iii. p. &S7. 
