Exterior of the boulder--Travelled stones a difficult problem--Once referred to the Deluge--Other theories--Novelty of the true solution--Icebergs formed in three ways--Progress and scenery of an iceberg--Its effects--Size of icebergs--Boulder clay had a glacial origin--This explanation confirmed by fossil shells--Laws of the distribution of life--Deductions, 6 CHAPTER III. 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, 18 CHAPTER IV. Interior of the boulder--Wide intervals of Geology--Illustration--Long interval between the formation of the boulder as part of a sand-bed, and its striation by glacial action--Sketch of the intervening ages--The boulder a Lower Carboniferous rock--Cycles of the astronomer and the geologist contrasted--Illustration--Plants shown by the boulder once grew green on land--Traces of that ancient land Its seas, shores, forests, and lakes, all productive of material aids to our comfort and power--Plants of the Carboniferous era--Ferns--Tree-ferns--Calamites--Asterophyllites-- Lepidodendron--Lepidostrobus--Stigmaria--Scene in a ruined palace--Sigillaria--Coniferæ, Cycadeæ--Antholites, the oldest known flower--Grade of the Carboniferous flora--Its resemblance to that of New Zealand, 30 CHAPTER V.