[Footnote 73: Of course, this deduction is founded, as the reader will notice, on the assumption that we have now the series, as it was deposited, and that no peaty swamp or forest was denuded away, and its site occupied by sand and silt. But the assumption is rendered probable from the conditions of formation indicated by the Roslyn group.] In some of the streamlets that flow into the beautifully wooded vale of the Esk, south of Penicuik, these limestones can be well seen, worn in the water-channel, or crusted over with moss along the banks. Their organisms are singularly abundant, and consist of cyathophylla, encrinites, spirifers, producti, &c., all exclusively marine. In a picturesque brook that falls into the Esk near a saw-mill in the grounds of Penicuik House, I have seen the little cup-corals clustered by dozens on the weathered rock, showing their delicate striated wrinkles in high relief among the scattered valves of productus and innumerable joints of the stone-lily. They were all well preserved, and in their grouping and general appearance differed in no respect from similar organisms in the mountain limestone of Roman Camp Hill. The inference to be drawn from them must accordingly correspond with what has been deduced from the mountain limestone fossils, viz., that they mark the site of a sea-bottom which remained free from mud and sand for considerable periods, during each of which there abounded corals and shells, whose exuviæ went to form several seams of limestone. But that this sea-bottom was at no period very far distant from land, is proved by the drifted plants that occur in the sandstones and shales both below and above, and which often show so little trace of maceration, that we can hardly believe they were carried far, or floated for a long while previous to being enveloped in the sand or mud at the bottom. I have never detected vegetable remains in the limestones themselves, but there seems no reason why they should not be found there.