The rock consisted of a hard grey sandstone finely laminated above, and getting pebbly and conglomeritic below. The included pebbles were well worn, and belonged to various kinds of rock. The upper part of the block was all rounded, smoothed, and deeply grooved, and, when split open, displayed numerous stems and leaflets of plants converted into a black coaly substance. These plants were easily recognisable as well-known organisms of the carboniferous strata, and it became accordingly evident that the boulder was a block of carboniferous sandstone. The pebbles below, however, must have been derived from more ancient rocks, and they were thus seen to represent some older geological formation. In this grey rock, therefore, there could at once be detected well-marked traces of at least two widely-separated ages. The evidence for each was indubitable, and the chronology of the whole mass could not be mistaken. The surface striation bore undoubted evidence of the glacial period, the embedded plants as plainly indicated the far more ancient era of the coal-measures, while the pebbles of the base pointed, though dimly, to some still more primeval age. I had here, as it were, a quaint, old, black-letter volume of the middle ages, giving an account of events that were taking place at the time it was written, and containing on its earlier pages numerous quotations from authors of antiquity. The scratched surface, to complete the simile, may be compared to this old work done up in a modern binding. Let us, then, first of all, look for a little at the exterior of the volume, and inquire into the origin of that strangely-striated surface, and of the clay in which the boulder rested. CHAPTER II. 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. Has the reader, when wandering up the course of a stream, rod in hand perhaps, ever paused at some huge rounded block of gneiss or granite damming up the channel, and puzzled himself for a moment to conjecture how it could get there? Or when rolling along in a railway carriage, through some deep cutting of sand, clay, and gravel, did the question ever obtrude itself how such masses of water-worn material came into existence? Did he ever wonder at the odd position of some huge grey boulder, far away among the hills, arrested as it were on the steep slope of a deep glen, or perched on the edge of a precipitous cliff, as though a push with the hand would hurl it down into the ravine below? Or did he ever watch the operations of the quarryman, and mark, as each spadeful of soil was removed, how the surface of the rock below was all smoothed, and striated, and grooved?