From the blackened plants that darkened the upper layers of the boulder, the transition was natural to the matrix in which they lay. The whole rock consisted of a fine quartzy sand more or less distinctly laminated, and showing in its lower parts well-rounded pebbles of quartz, green grit, and felspathic trap. The contemplation of these features suggested the existence of some old land with elevated ranges of hills, and wide verdant valleys traversed by rivulets and rivers which bore a ceaseless burden of mud, sand, and gravel, onwards to the sea. The pebbles afforded some indication of the kind of rocks that formed the hill-sides. Perhaps the higher grounds exhibited that grey wrinkled appearance peculiar to the quartz districts of the north-western Highlands, with here and there a bluff crag of felspathic trap shooting up from among the fern-brakes of the valley, or cutting across the channel of some mountain stream that tumbled over the pale rock in a sheet of foam. And there may have been among these uplands smooth undulating districts, dotted over with dark araucarian pines, and densely clothed with a brushwood of rolling fern, but which showed in all their ravines the green grit that formed the framework of the country,--its beds twisted and contorted, jointed and cleaved, like the grits and slates along the banks of many a stream, beloved by the angler, in the classic ground of the Ettrick and the Yarrow. But whatever may have been the special features of its scenery, there can be no doubt of the land's existence. The carbonized plants stand up to tell us of its strange and luxuriant vegetation. We have listened to their story, and suffered them to lead us away into forest, and lake, and sea, to look on the various forms of life, vegetable and animal, which abounded in that far-distant age. We return again to the boulder, and shall now seek to learn the lessons which the sand and pebbles have to teach us. Their subject belongs to what is called physical geology, and will bring before us some of the more mechanical operations of nature, such as the slow but constant action of air, rain, and rivers, upon hard rock, the grinding action of the waves, and the consequent accumulation of new masses of sedimentary rock. In all the departments of nature that come under the cognizance of man, there is seen to be an endless succession of mutations. According to the Samian philosopher-- "Turn wheresoe'er we may by land or sea, There's nought around us that doth cease to be. Each object varies but in form and hue, Its parts exchange; hence combinations new. And thus is Nature through her mighty frame For ever varying, and yet still the same."