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that the rock, or white-backed dove, is the original of our domestic species.

LINE OF CROMARTY SUTOR.

We find that there leaned against one of the precipices of the Southern Sutor, now washed by the spring-tides, a talus of loose débris, such as we see still leaning against the precipices of the old coast line, and that a calcareous spring, dropping upon it from an upper ledge, had, in the course of years, converted its apex into a hard breccia, and cemented it to the rock, while the base below remained incoherent as at first. During this period it must have lain beyond the sweep of the waves. But a change of level took place ; the waves came dashing against the loose débris, and swept it away; and all that now remains of the talus is the consolidated apex, projecting about three feet from the rock. Under another precipice of the Cromarty Sutor we find a line of consolidated débris,—which, like the breccia of the apex, must have been the work of a calcareous spring,— running out about fifty feet into the ebb, where it is altogether impossible it could have formed now. must have flowed downwards for these fifty feet ere it The spring reached the sea; for no sooner could it have touched the latter than its waters would have been diffused and lost; and, even could they have avoided such diffusion, the waves must have prevented the loose gravel on which the calcareous matter acted from remaining sufficiently stationary for a single tide. In each of these cases is the value of the evidence enhanced by the circumstances in which it is given. Both the talus and the brecciated line were formed on a basis of granitic rock, so hard that it strikes fire with steel, and which only a general change of level could have let down to the influence of the tide, or elevated over it.

LESSON TO YOUNG GEOLOGISTS FROM CLAY-BED OF THE NORTHERN SUTOR.

THERE is a stiff blue clay much used in Cromarty and the neighbourhood for rendering the bottom of ponds watertight, and the foundations of cellars impervious to the landsprings, and which, save for its greater tenacity, much resembles the blue boulder-clay of our Coal Measures. It is found in the ebb at half-tide, in a bed varying from eighteen inches to three feet in thickness, which overlies the red boulder-clay, and contains minute fragments of shells, too much broken to be distinguished. I had deemed it a sort of re-formation from strata of a greyish-coloured aluminous shale, which occur in the Old Red Sandstone, and are laid bare in the neighbourhood by the sea. The waves dash against them, and then roll back turbid with the lighter particles, to deposit these in the deep still water outside. But in the place at present occupied by the bed the waves could not have deposited them; it is so much exposed to the surf, that the deposit is gradually wearing down under the friction, and it must have been formed, therefore, at a lower level, and when the sea beat against the ancient beaches. We find further proof that such must have been the case in a soft stratum of grey, shaly sandstone, which rises through the bed, and which is thickly perforated by cells of the Pholas candidus, containing in abundance the dead shells, but which has been elevated to a too high place to form any longer a fit habitat for the living animals. I had often examined the fragmentary shells of this clayey layer, in the hope of being able to elicit from them somewhat regarding the history of a deposit older than our present coast line, yet newer than our boulder-clay; but I had hitherto found them in every case too comminuted to

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yield the necessary evidence. I now succeeded, however, in detecting the same deposit under the Northern Sutor, in the same close neighbourhood as on the Cromarty side to the grey aluminous shale of the Old Red Sandstone, to which it seems to have owed its origin, and abounding in organisms marine and terrestrial. All are recent. I found it containing cones of our common Scotch fir, hazel-nuts, fragments of alder and oak, shells of the common mussel much decomposed, and shells, too, of one of the Gaper family (Myæ arenaria), still lying in pairs. The blue adhesive clay in which they are embedded can scarce be distinguished from that of the Lower Lias of Eathie; the sets of organisms in the two deposits are also the same,-indicating that their deposition must have taken place under similar conditions. The Lias, like the recent clay, has its cones, its bits of wood, and its marine bivalves lying in pairs; and the sole difference that obtains between them is, that while the cones, and wood, and bivalves of the blue clay are all existences of the present time, the cones, and wood, and bivalves of the Lias represent classes of organic beings that have long since passed into extinction. This clay-bed of the Northern Sutor is one of the best places I know for the young geologist taking his first lesson upon. I deemed it of interest chiefly as corroborative of the fact that our raised beaches on the shores of the Cromarty and Moray Firths belong to exactly the present state of things; nay, that for a very considerable period ere their elevation, when the blue bed was forming in comparatively deep water, both sea and land were stored with their existing productions.

GLACIAL APPEARANCES AT NIGG AND LOGIE.

THERE are two several localities in which, after acquainting one's-self with the glacial moraines of Brora, one may

examine with advantage the glacial moraines of the neigh bourhood of Cromarty. One of these we find in the parish of Logie, not a hundred yards distant from the great coach road; the other, in the parish of Nigg, on one of the slopes in which the lofty ridge whose south-western termination forms the Northern Sutor sinks at its north-eastern boundary into the plain of Easter Ross. The Logie moraine extends, for full three quarters of a mile, in a line parallel to the mountain range from which its glacier must have descended. There is a furzy level in front, mottled over with groups of cottages; the moraine,-thickly planted with fir, and amid whose sheltering hollows the gipsies' tent may be seen in the warmer months, and the houseless Free Church congregation at this inclement season,-forms a long undulating ridge, in what a painter would term the middle ground of the landscape; while on the swelling acclivities behind, over which the icy plane must have once extended, we see woods, and fields, and stately manor-houses, and, high above all, the heathy mountain ridge, where the sky seems resting on the land. I have not seen the rock laid bare in any part of the cultivated tract which intervenes between the moraine and the upland ridge; but I entertain little doubt that its surface will be found to bear the characteristic groovings and polishings of the glacial period. The moraines of the hill of Nigg, as might be premised from the lower elevation and narrower slopes of the eminence from which their glacier descended, are of small extent compared with the moraine of Logie. There is, however, one of the number, a beautiful grassy Tomhan, fringed at the base with its thickets of dwarf-birch and hazel, that was deemed commanding enough, in some early age, to be selected as the site of a hill-fort, still known to tradition as the Danish camp, and whose double mound of turf we may still see encircling the summit. It must have been a dreary period when the great glacier of Logie, sloping towards the south,

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and the lesser glacier of the hill of Nigg, sloping towards the north, saw themselves reflected in the separating strait of sea which at this remote period flowed through the flat valley between. The valley is still occupied for half its length by a sandy estuary, known as the Sands of Nigg, which ere the upheaval of the higher beaches, must have existed as a shallow channel, through which the Firth of Cromarty, then a double-mouthed arm of the sea, with the hill of Nigg as a mountainous island in the midst,—communicated with the Moray Firth beyond.

PHENOMENA EXPLANATORY OF ACCUMULATIONS OF SHELLS.

THERE are scarce any of the appearances with which the geologist is conversant more mysterious than the immense accumulations of shells which he occasionally finds, as in some parts of Sweden, separated from all extraneous matter, as if they had been subjected to some sifting process,― cleaned, as it were, and laid by; and it has long been a question with him how this sifting process has been effected. The theory that the accumulation had been heaped up by great floods, through which substances of the same specific gravity were huddled together, has been the commonly accepted one; but who ever saw a flood, however great, that did not cast down its mud and its clay among its transported shells, or that had not mingled them, in the process of removal, with its lighter gravels or its sand? In the flat estuary of Nigg, I have seen the sifting process effected through a simple but adequate agency. For about two miles from where the estuary opens into the Cromarty Firth, its wild tracts of yielding sand are thickly occupied by the shells that love such localities,-in especial, by the common cockle. Almost every tide, when the animals are in season, furnishes its vast quantities for the