The early antiquaries discovered the hand of the Druids in certain unusual rock-shapes, now known to be the work of Nature--such as rock-basins, which are developed in the granite by the action of wind and rain; tolmens, or holed stones; and logans, or rocking-stones. Granite on the moor generally weathers irregularly, and if the lower part of a piled-up mass partly crumbles away, a huge layer of harder granite remains balanced on one or two points, and becomes what is called a logan-stone. In some cases, though the slab is almost impossible to remove, it will rock at a finger-touch. Perhaps the most striking example on Dartmoor is the Rugglestone, near Widdecombe, which it has been calculated weighs about one hundred and ten tons; but there are several in the neighbourhood, and a logan called the Nut-Crackers is perched among the thickly scattered boulders on Lustleigh Cleave. This lovely little valley lies on the eastern edge of the moor, and the River Bovey flows through it. Masses of granite crown the ridge; lower on the hill-side is a jungle of tall bracken, and the stream is overshadowed by a wood, crowded with matted undergrowth and with innumerable rocks tumbled together. Granite more consistent than that found on most of the tors--that is, 'not broken into the usual layers of soft beds alternating with hard layers'--forms the great masses of rock on Hey Tor, and these have not weathered into strange, jagged outlines. William Howitt wrote a charming description of Hey Tor in his 'Rural Life of England,' from which I quote a few lines: 'Below, the deep dark river went sounding on its way with a melancholy music, and as I wound up the steep road all beneath the gnarled oaks, I ever and anon caught glimpses of the winding valley to the left, all beautiful with wild thickets and half-shrouded faces of rock, and still on high these glowing ruddy tors standing in the blue air in their sublime silence. My road wound up and up, the heather and bilberry on either hand.'