roaring geysers, that ever and anon throw up their intermittent jets of boiling fluid, vapour, and thick steam, from these tremulous lands; and, in the dim outskirts of the scene, the red gleam of fire, shot forth from yawning cracks and deep chasms, and that bears aloft fragments of molten rock and clouds of ashes. But should we continue to linger amid a scene so featureless and wild, or venture adown some yawning opening into the abyss beneath, where all is fiery and yet dark,—a solitary hell, without suffering or sin,-we would do well to commit ourselves to the guidance of a living poet of true faculty,-Thomas Aird,-and see with his eyes, and describe in his verse :—

'The awful walls of shadows round might dusky mountains seem,
But never holy light hath touched an outline with its gleam;
'Tis but the eye's bewildered sense that fain would rest on form,
And make night's thick blind presence to created shapes conform.
No stone is moved on mountain here by creeping creature cross'd,
No lonely harper comes to harp upon this fiery coast;
Here all is solemn idleness; no music here, no jars,
Where silence guards the coast ere thrill her everlasting bars;
No sun here shines on wanton isles; but o'er the burning sheet
A rim of restless halo shakes, which marks the internal heat;
As in the days of beauteous earth we see, with dazzled sight,
The red and setting sun o'erflow with rings of welling light.'

END OF THE LECTURES.

NOTE.

'The only shells I ever detected in the brick-clay of Scotland occurred in a deposit in the neighbourhood of St. Andrews, of apparently the same age as the beds at Portobello.'-Lecture Second, page 64.

NOTE. Some time after this statement was made, Mr. Miller devoted himself to a further investigation of the brick-clay beds in the neighbourhood of Portobello, and discovered several species of shells in situ, especially great abundance of Scrobicularia piperata, which he has described in a paper on the brick-clays, to be published hereafter. They form a very interesting portion of his Museum, now in the University of Edinburgh. 'But for him,' said an accomplished geologist, in talking with me on the subject, 'we would have known nothing whatever of the brickclays.'-L. M.

Q

APPENDIX.

GANOID SCALES AND RAYS.

THE scales of the ganoid order consist of three plates,an inner, an outer, and an intervening one. The outer is composed mainly of enamel, and retains, when entire, however long exposed, much of the original dinginess of hue which it bore in the quarry: the inner is a plane of porcelanic-looking bone: the intermediate plate is finely composed of concentric lines, crossed from the centre to the circumference by finely radiating ones; and when, as mostly happens, this middle plate is exposed, the appearance of a mass of scales through the glass is of great beauty. The rays of our soft-finned fish (Malacopterygii), such as the haddock, seem as if cut through at minute distances, and then re-united, though less firmly than where the bone is entire, with the design, it would seem, of giving to the organs of motion which they compose the necessary flexibility, somewhat on the principle that a carpenter cuts halfthrough with his saw the piece of moulding which he intends bending along some rounded corner, or forcing into some concave. But in the ancient ganoid fish, in which the rays are bare enamelled bones, and necessarily of great rigidity, the joints appear real, not fictitious. We see them cut across into short lengths, a single fin consisting of many hundred pieces; and the problem lay in conceiving how

such a fin was to be wrought,-whether, for instance, each detached length was to have its moving ligament; and if so, how a piece of machinery so very complicated and multifarious was to be set and kept in motion. Here, however, I found the problem very simply resolved. The rays of the ganoid fish, like its scales, consist of three plates,two plates of enamel, one on each side, and an interior plate of bone. Now the joints,-though so well marked, that in rays imbricated on the sides, as in those of the Cheirolepis, the imbricated markings turn the corners, if one may so speak, just as the carvings on a moulding recounter, as a workman would say, at the corners of a building, are not real joints after all: they reach but through the inflexible enamel, leaving the central plate of bone undivided. Like the rays of the Malacopterygii, they are formed on the principle of the half-sawn moulding. I observed, too, that the inner plate is in every instance considerably narrower than the plates of enamel which rest upon it. In the lateral edges of every ray which composes the inner portion of the fin there must exist a groove, therefore; and in this groove, it is probable, the connecting membrane at one time lay hid, performing, like an invisible hinge, its work unseen.

RECENT BONE-BED IN THE FORMING.

I ONCE found an interesting illustration of the bone-bed, coupled with at least one of the causes to which it owes its origin, in the upper part of the Moray Firth. I had been spending a night at the herring-fishing, on one of the most famous fishing-banks of the east coast of Scotland,-the bank of Guilliam. It is a long, flat ridge of rock that rises to within ten or twelve fathoms of the surface. On its southern edge there is a submarine valley that sinks to at