Following the beds downwards along the beach, I found that one of the lowest which the tide permitted me to examine,--a bed colored with a tinge of red,--was formed of a denser limestone than any of the others, and composed chiefly of vast numbers of small univalves resembling Neritæ. It was in exactly such a rock I had found, in the previous year, the reptile remains; and I now set myself, with no little eagerness, to examine it. One of the first pieces I tore up contained a well-preserved Plesiosaurian vertebra; a second contained a vertebra and a rib; and, shortly after, I disinterred a large portion of a pelvis. I had at length found, beyond doubt, the reptile remains _in situ_. The bed in which they occur is laid bare here for several hundred feet along the beach, jutting out at a low angle among boulders and gravel, and the reptile remains we find embedded chiefly in its under side. It lies low in the Oölite. All the stratified rocks of the island, with the exception of a small Liasic patch, belong to the Lower Oölite, and the reptile-bed occurs deep in the base of the system,--low in its relation to the nether division, in which it is included. I found it nowhere rising to the level of high-water mark. It forms one of the foundation tiers of the island, which, as the latter rises over the sea in some places to the height of about fourteen hundred feet, its upper peaks and ridges must overlie the bones, making allowance for the dip, to the depth of at least sixteen hundred. Even at the close of the Oölitic period this sepulchral stratum must have been a profoundly ancient one. In working it out, I found two fine specimens of fish jaws, still retaining their ranges of teeth;--ichthyodorulites,--occipital plates of various forms, either reptile or ichthyic,--Ganoid scales, of nearly the same varieties of pattern as those in the Weald of Morayshire,--and the vertebræ and ribs, with the digital, pelvic, and limb-bones, of saurians. It is not unworthy of remark, that in none of the beds of this deposit did I find any of the more characteristic shells of the system,--Ammonites, Belemnites, Gryphites, or Nautili.
I explored the shores of the island on to the _Ru Stoir_, and thence to the Bay of Laig; but though I found detached masses of the reptile bed occurring in abundance, indicating that its place lay not far beyond the fall of ebb, in no other locality save the one described did I find it laid bare. I spent some time beside the Bay of Laig in reëxamining the musical sand, in the hope of determining the peculiarities on which its sonorous qualities depended. But I examined, and cross-examined it in vain. I merely succeeded in ascertaining, in addition to my previous observations, that the loudest sounds are elicited by drawing the hand slowly through the incoherent mass, in a segment of a circle, at the full stretch of the arm, and that the vibrations which produce them communicate a peculiar titillating sensation to the hand or foot by which they are elicited, extending in the foot to the knee, and in the hand to the elbow. When we pass the wet finger along the edge of an ale-glass partially filled with water, we see the vibrations thickly wrinkling the surface: the undulations which, communicated to the air, produce sound, render themselves, when communicated to the water, visible to the eye; and the titillating feeling seems but a modification of the same phenomenon acting on the nerves and fluids of the leg or arm. It appears to be produced by the wrinklings of the vibrations, if I may so speak, passing along sentient channels. The sounds will ultimately be found dependent, I am of opinion, though I cannot yet explain the principle, on the purely quartzose character of the sand, and the friction of the incoherent upper strata against under strata coherent and damp. I remained ten days in the island, and went over all my former ground, but succeeded in making no further discoveries.