CHAPTER III.. How the Boulder Came to Be One--"crag and Tail"--Scenery of

How the boulder came to be one--"Crag and tail"--Scenery of central Scotland: Edinburgh--"Crag and tail" formerly associated in its origin with the boulder-clay--This explanation erroneous--Denudation an old process--Its results--Illustration from the Mid-Lothian coal-field--The three Ross-shire hills--The Hebrides relics of an ancient land--Scenery of the western coast--Effects of the breakers--Denudation of the Secondary strata of the Hebrides--Preservative influence of trap-rocks--Lost species of the Hebrides--Illustration--Origin of the general denudation of the country--Illustrative action of streams--Denudation a very slow process--Many old land-surfaces may have been effaced--Varied aspect of the British Islands during a period of submergence--Illustration,