LECTURES ON GEOLOGY.

LECTURE FIRST.

Junction of Geologic and Human History-Scottish History of Modern Date-The Two Periods previous to the Roman Invasion: the Stone Age and the Bronze Age-Geological Deposits of these Prehistoric Periods-The Aboriginal Woods of Scotland-Scotch Mosses consequences of the Roman Invasion-How formed -Deposits, Natural and Artificial, found under them-The Sand Dunes of Scotland-Human Remains and Works of Art found in them-An Old Church disinterred in 1835 on the Coast of Cornwall-Controversy regarding itAncient Scotch Barony underlying the Sand-The Old and New Coast Lines in Scotland-Where chiefly to be observed-Geology the Science of Landscape -Scenery of the Old and New Coast Lines-Date of the Change of Level from the Old to the New Coast Line uncertain-Beyond the Historic but within the Human Period-Evidences of the fact in remains of Primitive Weapons and Ancient Boats-Changes of Level not rare events to the Geologist-Some of these enumerated-The Boulder-Clay-Its Prevalence in the Lowlands of Scotland-Indicated in the Scenery of the Country-The Scratchings on the Boulders accounted for-Produced by the grating of Icebergs when Scotland was submerged-Direction in which Icebergs floated, from West to East'Crag and Tail:' the effect of it-Probable Cause of the Westerly Direction of the Current.

IN most of the countries of Western Europe, Scotland among the rest, geological history may be regarded as ending where human history begins. The most ancient portions of the one piece on to the most modern portions of the other. But their line of junction is, if I may so express myself, not an abrupt, but a shaded line; so that, on the one hand, the human period passes so entirely into the geological, that we found our conclusions respecting the first human inhabitants rather on what may be deemed

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geologic than on the ordinary historic data; and, on the other hand, some of the later and lesser geologic changes have taken place in periods comparatively so recent, that, in even our own country, we are able to catch a glimpse of them in the first dawn of history proper,-that written history in which man records the deeds of his fellows.

In Scotland the ordinary historic materials are of no very ancient date. Tytler's History opens with the accession of Alexander III. in the middle of the thirteenth century; the Annals of Lord Hailes commence nearly two centuries earlier, with the accession of Malcolm Canmore; there still exist among the muniments of Durham Cathedral charters of the gracious Duncan,' written about the year 1035; and it is held by Runic scholars that the Anglo-Saxon inscription on the Ruthwell Cross may be about two centuries earlier still. But from beyond this comparatively modern period in Scotland no written document has descended, or no native inscription decipherable by the antiquary. A few votive tablets and altars, lettered by the legionaries of Agricola or Lollius Urbicus, when engaged in laying down their long lines of wall, or rearing their watch-towers, represent a still remoter period; and a few graphic passages in the classic pages of Tacitus throw a partial and fitful light on the forms and characters of the warlike people against which the ramparts were cast up, and for a time defended. But beyond this epoch, to at least the historian of the merely literary type, or to the antiquary of the purely documentary one, all is darkness. 'At one stride comes the dark.' The period is at once reached which we find so happily described by Coleridge. 'Antecedently to all history,' says the poet, and long glimmering through it as a hazy tradition, there presents itself to our imagination an indefinite period, dateless as eternity,—a state rather than a time. For even the sense of succession is lost in the uniformity of the stream.'

It is, however, more than probable that the age of Agricola holds but a midway place between the present time and the time in which Scotland first became a scene of human habitation. Two great periods had passed ere the period of the Roman invasion,-that earliest period now known to the antiquary as the stone age,' in which the metals were unknown, and to which the flint arrow-head and the greenstone battle-axe belong; and that after-period known to the antiquary as the bronze age, in which weapons of war and the chase were formed of a mixture of copper and tin. Bronze had in the era of Agricola been supplanted among the old Caledonians by iron, as stone had at an earlier era been supplanted by bronze; and his legionaries were met in fight by men armed, much after the manner of their descendants at Sheriffmuir and Culloden, with broadsword and target. And it is known that nearly a century and a half earlier, when Cæsar first crossed the Channel, the Britons used a money made of iron. The two earlier periods of bronze and stone had come to a close in the island ere the commencement of the Christian era; and our evidence regarding them is, as I have said, properly of a geologic character. We read their history in what may be termed the fossils of the antiquary. Man is peculiarly a tool-and-weapon-making animal; and his tools and weapons represent always the stage of civilisation at which he has arrived. First, stone is the material

out of which he fashions his implements.

If we except

that family of man which preserved the aboriginal civilisation, there seems never to have been a tribe or nation that had not at one time recourse to this most obvious of substances for their tools and weapons. Then comes an age in which stone is supplanted by the metals that occur in a native state,-i.e., in a state of ductility in the rock, such as copper, silver, and gold. Of these, copper is by much the most abundant; and in all

countries in which it has been employed for tools and weapons means have been found by the primitive workers to harden it through an admixture of other metals, such as zinc and tin. Last of all, the comparatively occult art of smelting iron is discovered, and the further art of converting it into steel; and such is its superiority in this form to every other metal employed in the fabrication of implements, that it supplants every other; and the battle-axe and chisel of hardened copper (bronze) are as certainly superseded by it as the chisel and the battle-axe of stone had at an earlier period been superseded by the bronze.1 Now, it is truly wonderful how thoroughly, for all general purposes, this scheme of classification, which we owe to the Danish antiquary Thomsen, arranges into corresponding sections and groups the antiquities of a country, and gives to it a legible history in ages unrecorded by the chronicler. With the stone tools or weapons there are found associated in our own country, for instance, a certain style of sepulture, a certain type of cranium, a certain form of human dwellings, a certain class of personal ornaments, certain rude log-hollowed canoes, undressed standing stones, and curiously-poised cromlechs. The bronze tool or weapon has also its associated class of antiquities,-massive ornaments of gold,

1 In an interesting article on Ireland which lately appeared in the Scotsman newspaper, I find it stated that for a very considerable distance, 'between Lough Rea and Lough Derg, the river Shannon was fordable at only one point, which of course formed the only medium of communication between the natives of the two banks. They seem, however,' it is added, 'to have met oftener for war than peace; and from this ford a whole series of ancient warlike weapons was dug out. These weapons are now preserved in the fine collection of antiquities in the Museum of the Royal Irish Academy in Dublin, and are partly bronze and partly stone. Their position in the river bed told a curious tale, both historically and geologically. The weapons of bronze were all found in the upper stratum, and below them those of stone; showing, as antiquaries well know, that an age of bronze followed not an age of gold, but an age of stone.'