Calcareous shale. Limestone (marine), eight feet. Calcareous shale, with _spirifers_, &c. Coal, six to eight inches. Fire-clay. Sandstone. A short way further down the stream another bed of limestone occurs with several seams of coal below it, one of them attaining a thickness of six feet. In addition to the thin seam at Esperston, the Mid-Lothian field contains several others. Of these by much the most important is that known as the North Greens Seam. It varies in thickness from only a few inches to fully 5 feet, and has been extensively worked for the _parrot_ or gas-coal which it contains. It rests upon a pavement of shale, sometimes of fire-clay, and occurs about midway between two thick marine limestones, being from 80 to 90 feet distant from each. I have laid open many a block of the parrot-coal at the pit mouth, and marked the well-defined outlines of the stigmaria covered with a yellowish efflorescence of iron pyrites, like gilded figures upon a black velvet ground. The plants lie with their divergent rootlets spread out regularly along the stem like teeth on the back of a comb, thus seeming to indicate no hurried agglomeration by some tidal wave or turbid river, but rather a slow and tranquil deposition. The fossils of the coal-seams consist for the most part of the plants above described, which we saw to belong to _terrestrial species_. But the reader will now understand that in dealing with organic remains we cannot infer, because a certain stratum contains nothing but land-plants, that it must necessarily by consequence be a land-formation. For we have seen that the plants of the Burdiehouse limestone, though all terrestrial, gave no support to the idea that the rock had originated on land. In all such cases regard must be had not only to the nature of the imbedded organisms, but their condition and mode of occurrence, and to the character of those associated with them. Especial care must be taken to distinguish what has been transported from what is _in situ_, otherwise, by attending only to one part of the evidence, we shall miss the import of the whole, and altogether misinterpret the records which we seek to decipher.