tions. Even wanting that, however, it is something to know, that though the sea has stood at the existing seamargin since the days of Agricola, and at least a few centuries more, it stood for a considerably longer period at the old coast line. The rock of which those remarkable promontories, the Sutors of Cromarty, are composed, is a granitic gneiss, much traversed by faults, and enclosing occasional masses of a soft chloritic schist, that yields to the waves, while the surrounding gneiss,-hard enough to strike fire with steel,~remains little affected by the attrition of centuries. These promontories have, in consequence, their numerous caves ranged in a double row,-the lower row that of the existing coast, the upper that of the old one; and I have examined both rows with some little degree of care. The deepest of the recent caves measures, from the opening to its inner extremity, where the rock closes, exactly a hundred feet; the deepest of the ancient ones, now so completely raised above the surf, that in the highest tides, and urged upwards by the severest storms, the waves never reach its mouth, measures exactly a hundred and fifty feet. And these depths, though much beyond the respective average depths of their several rows, bear, so far as I could ascertain the point, the proportions to each other that these averages bear. The caves of the existing coast line are as two in depth, and those of the old coast line as three. If the excavation of the recent caves be the work of two thousand years, the excavation of the ancient caves must have been the work of three thousand; or, as two thousand does not bring us much beyond the Roman period, let us assume as the period of the existing coast line and its caves, two thousand two hundred years, and as the proportional period of the old coast line, three thousand three hundred more. Both sums united bring us back five

thousand five hundred years. How much more ancient either coast line may be, we of course cannot determine :

we only know that, on the lowest possible assumption, we reach a period represented by their united ages only less extended by six years than that which the Samaritan chronology assumes as the period during which man has existed upon earth, and only three hundred and fifty-five years less than that assumed by the Masoretic chronology. The chronology of the Septuagint, which many have begun to deem the most adequate of the three, adds about five hundred and eight-six years to the sum of the latter.

Permit me, in closing this part of my subject, to show you that changes of level such as that to which we owe our old coast line in Scotland, and the marginal strip of dry land which we have laid out into so many pleasant gardens and fields, and on which we have built so many of our seaport towns, are by no means very rare events to the geologist. He enumerates at least five localities in the Old World,-Scandinavia, part of the west coast of Italy, the coasts of Cutch and of Arracan, and part of the kingdom of Luzan, in which the level is slowly changing at the present time; and in the New World there are vast districts in which the land suddenly changed its level for a higher one during the present century. On the 19th of November 1822,' says Sir Charles Lyell, 'the coast of Chili was visited by a most disastrous earthquake. When the district around Valparaiso was examined on the morning after the shock, it was found that the whole line of coast for the distance of above one hundred miles was raised above its former level. At Valparaiso the elevation was three feet, and at Quinteno about four feet. Part of the bed of the sea remained bare and dry at high water, with beds of oyster, mussel, and other shells, adhering to the rocks on which they grew, the fish being all dead, and exhaling offensive effluvia.' Again, on the east side of the Bay of Bengal, upon the coast of Arracan, which is at present in the course of rising, there are islands which present on their

shores exactly such an appearance as our own country would have presented some sixty or a hundred years after the elevation of the old coast line. The island of Reguain, one of these, was carefully surveyed in the year 1841 by the officers of Her Majesty's brig Childers; and it has been carefully mapped in the admirable Physical Atlas of the Messrs. Johnston of Edinburgh. We find it, as shown in the map, resembling three islands; the one placed within the other, as, to employ a homely illustration, the druggist, to save room, places his empty pill-boxes the one within the other. First, in the centre, there is the ancient island, with a well-defined coast line, some six or eight feet high, running all around it. At the base of this line there is a level sea of rich paddy fields,—for what may be termed the second island has been all brought into cultivation; and it has also its coast line, which descends some six or eight feet more, to the level of a third island, which was elevated over the sea not more than eighty years ago, and which is still uncultivated; and the third island is surrounded by the existing coast line. Thus the centre island of Reguain consists of three great steps or platforms, each of which marks a paroxysm of elevation; and, with the upheaval of the coast of Chili, and a numerous class of events of a similar character, it enables us to conceive of the last great geological change of which our country was the subject. We imagine a forest-covered land, marked by the bold commanding features by which we recognise our country, but inhabited by barbarous, half-naked tribes, that dwell in rude circular wigwams, formed of the branches of trees,that employ in war or the chase weapons of flint or jasper, -and that navigate their rivers or estuaries in canoes hollowed by fire out of single logs of wood. There has been an earthquake during the night; and when morning rises, the beach shows its broad darkened strip of apparent ebb, though the tide is at full at the time; and when

the waters retire, they leave uncovered vast tracts never seen before, comparatively barren in sea-weed, but rich in stony nulliporite incrustations, minute corallines, and fleshy sponges. Ages elapse, and civilisation grows. The added belt of level land is occupied to its utmost extent by man : he lays it out into gardens and fields, and builds himself a dwelling upon it: but no sooner has he rendered it of some value, than the sea commences with him a course of tedious litigation for the recovery of its property; and bit by bit has it been wrested out of his hands. Almost all those tracts on our coasts which have been suffering during the last few centuries from the encroachment of the waves, and which have to be protected against their fury wherever land is valuable, as in this neighbourhood, by lines of bulwarks, belong to the flat marginal strip won from them by the last change of level.

The

Our next great incident in the geologic history of Scotland dates, it would seem, beyond the human period. In passing along the beach between Musselburgh and Portobello, or again between Portobello and Leith, or yet again between Leith and Newhaven, one sees an exceedingly stiff, dark-coloured clay, charged with rounded pebbles and boulders, and which, where washed by the waves, presents a frontage nearly as steep as that of the rock itself. deposit by which it is represented is known technically to the agriculturist as Till, and to the geologist as the BoulderClay. Though not continuous, it is of very general occurrence, in the Lowlands of Scotland, and presents, though it varies in colour and composition, according to the nature of the rocks which it overlies, certain unique appearances, which seem to connect its origin in the several localities with one set of causes, and which no other deposit presents. Like the raised beaches, it has contributed its distinctive quota to the variously featured scenery of our country. The Scottish word scaur, in the restricted signifi

cancy attached to it in many parts of the kingdom, means simply a precipice of clay, and it is almost invariably the boulder-clay that forms scaurs in Scotland; for it is one of the peculiarities of the deposit, that it stands up well-nigh as steeply over the sides of rivers, or on encroaching seabeaches, or on abrupt hill-sides, as rock itself; and these clay precipices bear almost invariably a peculiar set of characters of their own. In some cases they spring up as square and mural, seen in front, as cliffs of the chalk, but seen in profile, we find their outlines described by parabolic curves. In other cases we see the vegetable mould rendered coherent by the roots of shrubs and grasses projecting over them atop, like the cornice of some edifice over its frieze. In yet other cases, though abrupt as precipices of solid rock, we find them seamed by the weather into numerous divergent channels, with pyramidal peaks between; and, thus combining the perpendicularity of true cliffs with the rain-scooped furrows of a yielding soil, they present eccentricities of aspect which strike, by their grotesqueness, eyes little accustomed to detect the picturesque in landscape. Such are some of the features of the scaurs of our country,- -a well-marked class of precipices for which the English language has no name. It is, however, in continuous grass-covered escarpments, which in some parts form the old coast line, and rise in others along the sides of rivers, that we detect at once the most marked and most graceful scenic peculiarity of the boulder-clay. The steep slopes, furrowed by enormous flutings, like those of the antique Doric, appear as if laid out into such burial-mounds as those with which a sexton frets the surface of a country churchyard, but with this difference, that they seem the burial-mounds of giants tall and bulky as those that of old warred against the gods. On a grass-covered escarpment of the boulder-clay in the neighbourhood of Cromarty, these mounds are striking enough to have caught the eye of the