which, has elapsed since the stone implements of prehistoric tribes were first buried under beds of gravel and sand by the rivers now represented by the Thames or the Somme. Still vaster, however, is the idea of antiquity suggested by the geographical conformation of such valleys as those in which these rivers flow. The drift-beds lie on their sides often 100 to 200 feet, and even more, above the present flood- levels. As such highest deposits seem to mark the time when the rivers flowed at heights so far above the present channels, it follows that the drift-beds, and the men whose works they enclose, must have existed during a great part of the time occupied by the rivers in excavating their valleys down to their present beds. Granting it as possible that the rivers by which this enormous operation was performed were of greater volume and proportionately still greater power in flood-time than the present streams, which seem so utterly inadequate to their valleys, and granting also, that under different conditions of climate the causing of debacles by ground-ice may have been a powerful excavating agent, nevertheless, with all such allowances the reckoning of ages seems vastly out of proportion to historical chronology. It is not convenient to discuss here Mr Prestwich s division of the drift gravels into high and low level beds, nor Mr A. Tylor s argument against this division, nor the latter s theory of a Pluvial period succeeding the Glacial period (see Quart. Journ. Geol. Soc., vol. xxiv. part 2, vol. xxv. part 1). The geology of the Quaternary or Post-tertiary gravels, on which the geological argument for the high antiquity of man mainly rests, has been especially treated
by Prestwich in the Philos. Trans., 1860, p. 277, and 1864, p. 247; see also J. Evans, Ancient Stone Impts., ch. 25; references to the writings of other geologists will be found in the already mentioned works of Lyell and Lubbock.
Beside these arguments, which suggest high antiquity rather than offer means of calculation, certain inferences (accounts of which are also given in the last-named works) have been tentatively made from the depth of mud, earth, peat, &c. which has accumulated above relics of human art imbedded in ancient times. Among these is Mr Horner's argument from the numerous borings made in the alluvium of the Nile valley to a depth of 60 feet, where down to the lowest level fragments of burnt brick and pottery were always found, showing that people advanced enough in the arts to bake brick and pottery have inhabited the valley during the long period required for the Nile inundations to deposit 60 feet of mud, at a rate probably not averaging more than a few inches in a century. Another argument is that of Professor von Morlot, based on a railway section through a conical accumulation of gravel and alluvium, which the torrent of the Tiniere has gradually built up where it enters the Lake of Geneva near Villeneuve. Here three layers of vegetable soil appear, proved by the objects imbedded in them to have been the successive surface-soils in two prehistoric periods and in the Roman period, and which now lie 4, 10, and 19 feet underground; on this it is computed that if 4 feet of soil were formed in the 1500 years since the Roman period, we must go 5000 years farther back for the date of the earliest human inhabitants. Calculations of this kind, loose as they are, deserve attention.
The interval between the Quaternary or Drift period and the period of historical antiquity is to some extent bridged over by relics of various intermediate civilisations, mostly of the lower grades, and in some cases reaching back to remote dates. The lake dwellings of Switzerland are perhaps among the more recent of these. They were villages of huts built on piles in the water at some distance from the shore, for security from attack in fact, fortified water settlements of the same nature as those of Lake Prasias in the time of Herodotus, and as those still inhabited in New Guinea and West Africa. The remains of these Swiss villages are found with the stumps of the piles still standing, often imbedded in an accumulation of mud or growth of peat which has preserved a kind of illustrative museum of the arts and habits of the lake men. From examination of the sites, it appears that the settlements are of various dates, from the neolithic or polished stone period, when instruments of metal were still unknown, to the time when bronze was introduced, and beyond this into the later age marked by the use of iron. A few of the lake villages lasted on till the Roman dominion, as is proved by the presence of Roman coins and pottery, but they were soon afterwards abandoned, so that their very existence was forgotten, and their rediscovery only dates from 1853, when the workmen excavating a bed of mud on the shore of the Lake of Zurich found themselves standing among the piles of a lake settlement. In Germany, Italy, and other countries, similar remains of a long pre-Roman civilisation have been found. (The special works on lake habitations are Dr Keller's Lake Dwellings, translated by J. E. Lee, London, 1866; and Troyon's Habitations Lacustres). Indications of man's antiquity, extending farther back into prehistoric times, are furnished by the Danish Shell-heaps or “kjökkenmödding,” which term, meaning " kitchen refuse-heap," has been Anglicised in " kitchen midden " (the word "midden," a dung-heap, being still current in the north of England). Along the shores of nearly all the Danish islands extensive beds or low mounds, like raised beaches, maybe seen, consisting chiefly of innumerable cast-away shells, intermingled with bones, &c. Such shell- heaps are found in all quarters of the globe by the sea-shore, and may be sometimes seen in process of formation ; they are simply the accumulations of shells and refuse thrown away near the huts of rude tribes subsisting principally on shell-fish. The Danish kitchen middens, however, are proved to belong to a very ancient time, by the remains of the quadrupeds, birds, and fish, which served as the food of these rude hunters and fishers; among these are bones of the wild bull, beaver, seal, and great auk, all now extinct or rare in this region. Moreover, a striking proof of the antiquity of these shell-heaps is, that the shells of the common oyster are found of full size, whereas it cannot live at present in the brackish waters of the Baltic except near its entrance, so that it is inferred that the shores where the oyster at that time flourished were open to the salt sea. Thus, also, the eatable cockle, mussel, and periwinkle abounding in the kitchen middens are of full ocean size, whereas those now living in the adjoining waters are dwarfed to a third of their natural size by the want of saltness. It thus appears that the connection between the ocean and the Baltic has notably changed since the time of these rude stone-age people. (See the reports by Forch- harnmer, Steenstrup, and Worsaae on the kjökkenmöddings, made to the Copenhagen Academy of Sciences.) Various other evidence is adduced in this part of the argument, such as that from the Danish peat-mosses, which show the existence of man at a time when the Scotch fir was abundant ; at a later period the firs were succeeded by oaks, which have again been almost superseded by beeches, a succession of changes which indicate a considerable lapse of time. For further references to special accounts, the reader may consult the already mentioned general works on the antiquity of prehistoric man.
