An hour or two thus spent will pass swiftly and pleasantly away, and on quitting the quarry he will have gained a new light in which to look on the landscape that lies spread out below. The mountain limestone of Mid-Lothian consists, as has been mentioned, of several seams interbedded with black and calcareous shales. The quarries on Roman Camp Hill have been opened in several of the thickest of these seams. Let us enter one of the excavations. A vertical face of rock forms the background, overhung above by long dangling tufts of withered grass, and washed below by a pool of water having that milky green tint peculiar to old lime-quarries. The lowest rock visible is a dull grey limestone with a yellowish weathered surface. Above it rests a mass of hard yellow calcareous shale, known to the workmen as "bands." This rock is worthless as a source of lime, nor from its irregular laminations and shivery structure has it much value in any other way. A few inches of surface-soil form the upper part of the section. It requires but a glance over the weathered surface of the limestone to mark that the rock abounds in fossils. Of these by far the most numerous are the joints of the stone-lily, for the most part of small size, and when broken across, with their minute central apertures, looking like so many fractured stems of tobacco-pipes. Other organisms also occur, such as a small delicately-plaited productus, a larger and more boldly-ribbed spirifer, a small cyathophyllum or cup-coral, and the fragile interlacing meshes of one of the net-like bryozoa--the fenestella. Of rarer occurrence are the whorled shells called bellerophon, the long chambered shells of orthoceratites, and the grooved tapering shells of pinnæ. Many of the same fossils can be detected in the beds above, which thus evidently all form part of one series with the rock below. What, then, were the circumstances under which these strata originated?