When a hard bed of granite lies on one that is very soft, the latter becomes disintegrated and eaten completely away. The hard bed is left either balanced on one point or more, or else has its centre of gravity so placed as to precipitate it from its position. Plenty of rocks may be seen in all these conditions. If it should chance that a rock remains poised on one point, then possibly a little pressure at one end of the slab will set it in motion. This, then, is known as a logan, or rocking stone, which antiquaries of old pronounced to have been employed by the Druids as oracles, or for purpose of divination. All this was bred out of the phantasy of the antiquaries. There is absolutely not a particle of evidence to show that they were supposed to be mysterious, or were employed in any rites, and it is also absolutely certain that they were formed by the hand of Nature alone. There are many logan rocks on Dartmoor. One is on Black Tor, near Princetown. It is instructive, as it not only shows the process of weathering which made it what it is, but it has on top of it a rock basin that decants by a lip over the edge of the stone when the latter is made to vibrate. The "Nutcracker" stone near Amicombe Hill above the West Ockment rolls in a high wind like a boat that is anchored. There were two very fine logans on Staple Tor above Merivale Bridge, but quarrymen wantonly destroyed the whole of one of the steeples, together with the finest logan on Dartmoor that was on it. The other remains. On Rippon Tor is one, another in Lustleigh Cleave. The felspar dissolved by the rain was carried away, and has been deposited in many places, filling up an ancient lake-bed and forming Bovey Heathfield, coating plains and hills with a deposit white as snow; this is kaolin, and is worked as china clay at Lee Moor and in Shaugh. The water flowing from the works is like milk, and, curiously enough, cows relish it. Having got rid of the rock basins and logan stones as pseudo-antiques, we will now address ourselves to those which are genuine. [Illustration: RIPPON TOR, LOGAN STONE]