In middle autumn, at the close of the herring season, when the fish have just spawned, and the congregated masses are breaking up on shallow and skerry, and dispersing by myriads over the deeper seas, they rise at times to the surface by a movement so simultaneous, that for miles and miles around the skiff of the fisherman nothing may be seen but the bright glitter of scales, as if the entire face of the deep were a blue robe spangled with silver. I have watched them at sunrise at such seasons on the middle of the Moray Frith, when, far as the eye could reach, the surface has been ruffled by the splash of fins, as if a light breeze swept over it, and the red light has flashed in gleams of an instant on the millions and tens of millions that were leaping around me, a handbreadth into the air, thick as hail-stones in a thunder-shower. The amazing amount of life which the scene included, has imparted to it an indescribable interest. On most occasions the inhabitants of ocean are seen but by scores and hundreds; for in looking down into their green twilight haunts, we find the view bounded by a few yards, or at most a few fathoms; and we can but calculate on the unseen myriads of the surrounding expanse by the seen few that occupy the narrow space visible. Here, however, it was not the few, but the myriads, that were seen--the innumerable and inconceivable whole--all palpable to the sight as a flock on a hill-side; or, at least, if all was not palpable, it was only because sense has its limits in the lighter as well as in the denser medium--that the multitudinous distracts it, and the distant eludes it, and the far horizon bounds it. If the scene spoke not of infinity in the sense in which Deity comprehends it, it spoke of it in at least the only sense in which man can comprehend it. Now, we are much in the habit of thinking of such amazing multiplicity of being--when we think of it at all--with reference to but the later times of the world's history. We think of the remote past as a time of comparative solitude. We forget that the now uninhabited desert was once a populous city. Is the reader prepared to realize, in connection with the Lower Old Red Sandstone--the second period of vertebrated existence--scenes as amazingly fertile in life as the scene just described--oceans as thoroughly occupied with being as our friths and estuaries when the herrings congregate most abundantly on our coasts? There are evidences too sure to be disputed that such must have been the case. I have seen the ichthyolite beds, where washed bare in the line of the strata, as thickly covered with oblong, spindle-shaped nodules as I have ever seen a fishing bank covered with herrings; and have ascertained that every individual nodule had its nucleus of animal matter--that it was a stone coffin in miniature, holding enclosed its organic mass of bitumen or bone--its winged, or enamelled, or thorn-covered ichthyolite.