[Illustration: A TOR, SHOWING WEATHERING OF GRANITE] Dartmoor, consisting mainly of a great upheaved mass of granite, and of a margin of strata that have been tilted up round it, forms an elevated region some thirty-two miles from north to south and twenty from east to west. The heated granite has altered the slates in contact with it, and is itself broken through on the west side by an upward gush of molten matter which has formed Whit Tor and Brent Tor. The greatest elevations are reached on the outskirts, and there, also, is the finest scenery. The interior consists of rolling upland. It has been likened to a sea after a storm suddenly arrested and turned to stone; but a still better resemblance, if not so romantic, is that of a dust-sheet thrown over the dining-room chairs, the backs of which resemble the tors divided from one another by easy sweeps of turf. Most of the heights are crowned with masses of rock standing up like old castles; these, and these only, are tors.[2] Such are the worn-down stumps of vast masses of mountain formation that have disappeared. There are no lakes on or about the moor, but this was not always so. Where is now Bovey Heathfield was once a noble sheet of water fifty fathoms deep. Here have been found beds of lignite, forests that have been overwhelmed by the wash from the moor, a canoe rudely hollowed out of an oak, and a curious wooden idol was exhumed leaning against a trunk of tree that had been swallowed up in a freshet. The canoe was nine feet long. Bronze spear-heads have also been found in this ancient lake, and moulds for casting bronze instruments. A representation of the idol was given in the _Transactions of the Devonshire Association_ for 1875. The new Plymouth Reservoir overlies an old lake-bed. Taw Marsh was also once a sheet of rippling blue water, but the detritus brought down in the weathering of what once were real mountains has filled them all up. Dartmoor at present bears the same relation to Dartmoor in the far past that the gums of an old hag bear to the pearly range she wore when a fresh girl. The granite of Dartmoor was not well stirred before it was turned out, consequently it is not homogeneous. Granite is made up of many materials: hornblende, feldspar, quartz, mica, schorl, etc. Sometimes we find white mica, sometimes black. Some granite is red, as at Trowlesworthy, and the beautiful band that crosses the Tavy at the Cleave; sometimes pink, as at Leather Tor; sometimes greenish, as above Okery Bridge; sometimes pure white, as at Mill Tor. The granite is of very various consistency, and this has given it an appearance on the tors as if it were a sedimentary rock laid in beds. But this is its little joke to impose on the ignorant. The feature is due to the unequal hardness of the rock which causes it to weather in strata.