THE DARTMOOR VOLCANO. 
147 
Carboniferous rocks occupy the surface, exposing in turn the lower 
strata of Devonian, Silurian, and probably Cambrian rocks in the 
West Cornwall mining district, with Archaean in the Lizard pro- 
montory. Dartmoor is about as large as all the other granitic areas of 
the West together, and has always had great relative importance. 
On a wide view Dartmoor presents the aspect of a tableland, 
with an elevation more decided in relation to the surrounding 
country than the rise of its highest points above its average level. 
This plateau character is best recognised in such a distant view 
as that from the Cheesewring. It can be seen from Staddon Heights, 
Maker, in a minor degree from Eoborough Down, and several other 
points ; but the Cheesewring coup d'oeil is most distinctive. It is 
far more strongly marked on the south of the Moor than on the 
north, where isolated heights are more common in the outskirts. 
The average height of Dartmoor above sea-level is 1200 feet, 
whereas the two highest points — High Willhayse and Yes Tor — 
are 2039 feet and 2029 feet respectively. The general contours are 
peculiar. The outer hills, the boundary rampart of the granite 
region, rise as a rule between 800 and 1000 feet, while the more 
broken belt of heights immediately succeeding averages between 
1200 and 1400. Still further in are two main areas of special 
elevation — the one in the northern and the other in the southern 
quarter — and these are divided by a line which follows practically 
the main road across the Moor from Dousland Barn to Moreton- 
hampstead, and undulates between 1000 and 1400 feet. 
The most elevated tract of Dartmoor is six miles in length 
KKW. to S.S.E., from Yes Tor to Cut Hill, and three miles 
wide. None of the heights here are under 1800 feet, and they 
range up to 2039. Near the centre of this region, approaching 
1900 feet above sea-level, is Cranmere, from the bogs around 
which, at a general elevation exceeding 1800 feet, issue the head 
waters of the Dart, Tavy, Okement, Taw, and Teign. 
East, and west, and south of this area, for a space of five 
miles broad and seven miles long, the tors attain a height of 
1700 feet; and beyond it, on the N.E., Cosdon Beacon rises in 
solitary majesty to 1784. The descent from the Moor at its 
extreme N.W. corner, near Okehampton, is more sudden and 
marked than at any other point, but otherwise it is somewhat 
less decided on the west than on the east. 
