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. The scratched and grooved surface of the boulder was produced when it was fast frozen in some iceberg, and driven gratingly across some submarine summit, or stranded on some rocky coast-line. But, from its rounded form, the stone had evidently undergone a long process of wear and tear previous to its glacial journey. Probably it had hitherto lain along a surf-beaten beach, where in the course of ages it had gradually been worn into its present rounded shape. But how came it there? It must originally have formed part of a flat sandstone bed, with many other beds piled above it. By what agency, then, was this great pile reduced to fragments? The answer to these questions must be a somewhat lengthened one, for the subject relates not to a few beds of rock hastily broken up and dispersed, but to the physical changes of an entire country, carried on during a vast succession of geological periods.