To see all the delicate veins and stalklets, and exact forms of what had once been the green fresh foliage of a remotely primeval forest, thus brought to light again, as preserved in their clay envelope, after they had lain for ages and ages under what must have been the molten outburst of some tremendous volcanic discharge, and which now formed the rock-bound coast of Mull, filled one's mind with an idea of the inconceivable length of time that must have passed since the production of these Wonderful geological phenomena.