and these, because in great part made up of the older beds, are like them, and require experience to distinguish. In these old terrace deposits implements of man's undoubted work have long been found; but recently it has been said that some of these beds belong to the older series. This, then, becomes a matter of opinion. For my part, being well acquainted with the deposits in question, and having listened to the evidence, I give my testimony quite against the glacial or the interglacial age of any of the beds from which the hatchets came. It is, however, said that other evidence has since been found, conclusive as to this. I can but criticise that which has been adduced; but I will say that if such has been found and been so long withheld, while there are so many deeply interested, and so many who would like to verify at once and on the ground the statements made, then I do hold that there has not been shown that love of full investigation which is the soul of science.

Upon the screen I give diagrammatic views of some of the sections showing the newer beds in which the implements were found, and older middle glacial, from which their relative position may be seen. These I have more fully described elsewhere.†

In many countries where rocks of limestone tower in cliffs and crags above the valleys, and are tapped below by undermining streams, the rain which falls upon the higher ground is lost in cracks and joints, and carries off the rock dissolved in water, which contains a little acid caught by the falling rain or drawn from decomposing plants. The fissures thus enlarged into the gaping chasms called "swallows' holes," the "katabothra" of the Greeks, admit a copious torrent, carrying stones and sand which grind and bruise and open out the jointed rock into great caves and subterranean courses. These, when tapped at lower levels, are soon left dry, and offer to prowling beasts of prey a safe retreat, and often man availed himself of them, as testify the Adullamites and Troglodytes of every age.

From such a cave up in the crags of Craven some evidence is adduced that man existed far back into glacial times, and this, perhaps, is the best case that has been urged. There a large group of animals, such as occur elsewhere along with man, and more doubtfully traces of man himself, were found in beds overlapped by glacial clay which had sealed up the mouth of the vast den in which these relics lay. This excavation I have watched myself at intervals from the commencement, and I hold

* Mem. Geol. Surv. Geology of Fenland.

+ Journ. Anthro. Inst. vol. vii. November, 1877, p. 162.
Tiddeman, Brit. Assoc. Reports, 1870-8.

that as the cliff fell back by wet or frost, and limestone fragments fell over the cave mouth, with them came also masses of clay, which, since the glacial times, had laid in hollows in the rock above. We dug and found such there, and, more, I observed that the clay lay across the mouth as though it had thus fallen, and not as if it came direct from glacial ice that pushed its way athwart the athwart the crag in which the cave occurs. It seemed to have fallen obliquely from the side where the fissured rock more readily yielded to the atmospheric waste, so that it somewhat underlay the part immediately above the cave. On the inside the muddy water which collected after flood, held back by all this clay, filled every crevice and the intervals between the fallen limestone rock, while still outside was the open talus of angular fragments known as "screes."

These are the most important cases that I know where man has been referred to glacial or inter-glacial times; but all, it seems to me, quite inconclusive. On the contrary, there is much in them, and much besides pointing the other way. In support of which opinion I will now offer some independent evidence, showing that some similar beds with man and the beasts that are found with him in earliest times can be proved to be post-glacial.

There are river gravels, as near Cambridge, at Barrington and Barnwell, which contain an ancient group* of mammals, earlier, it would appear, than those which most commonly occur with man, and yet the gravel in which they are found is made up largely of the washings and siftings of the boulder clay, which, therefore, was more ancient.

In a cave high in the limestone rocks that overhang the Elwy, in North Wales, are found human remains associated with rhinoceros, hyæna and cave-bear; but underneath and in the beds in which they lie are found fragments of rocks which must have come from other basins, transported by glacial agency across the watershed, and washed in where they are found, out of the boulder clay, which, therefore, in this case also is shown to be more ancient.† We should expect before the glacial times a somewhat different group, but on this head more evidence is wanting.

I will not waste time to discuss whether the objects we refer to man now found in numbers in post-glacial river gravels are really of human work. That is now generally allowed, and I have placed upon the table specimens from some of the more

*Fisher, Camb. Phil. Soc. February, 1879.

↑ Journ. Anthro. Inst. vol iii. 1873.

See Evans, Ancient Stone Implements of Great Britain.

important places. Accepting such things as human work, I will just enumerate a few of the many districts where they are found, to show that it is not an exceptional case to be explained by some local cataclysm caused by the sudden upheaving of the land, perhaps with earthquake shocks, or to the bursting of a barrier where the waters long pent up rushed down and filled the valley. We have to deal with facts so clear, so numerous, so widespread, and so similar everywhere, that we see we must at once refer them to the common ways of river denudation.

Along the Somme, loam, sand, and gravel, nearly a hundred feet above the river level of to-day, have yielded these works of man. We know that they are river gravels, from the shells that they contain. Similar implements are found along the Garonne, and in the basin of the Loire. They are brought from Africa and from India. In our own country, in the valleys of the Thames, the Ouse, the Medway, and the Avon, at 40, 50, 60, 80 feet above the river level; along the Solent and the coast near Barton, and near Bournemouth, and in the Isle of Wight, in terraces of ancient rivers, 100 to 150 ft. above the sea, they have been found. Everywhere in these older beds, with nearly the same groups of animals, the same types of instruments are found, distinct from later forms, quite recognisable.

And in caves we find traces of man with the extinct and migrated mammalia. In the Dordogne they have been classified by date, La Madelaine, the two Laugeries, and Le Moustier, the oldest being Le Moustier. In our own country, on the coast of Devon, in the cliffs of Yorkshire, Derbyshire, in Wales both North and South, along the Wye, and almost wherever limestone crags are found, these caves have furnished shelter to an early race of man. I do not know that as yet any exact relation has been established between a cave with works of man and any terrace with the same. A diagram on the screen shows the position of one of the celebrated Pyrenean caves (Gourdan)* with reference to the higher terraces of river gravel opposite to it. They stand at the same height above the river. This cave contains the usual group of extinct and migrated mammalia, and of man abundant evidence in bone and stone, of which examples lie upon the table. The terraces immediately opposite have not, so far as I am aware, yielded remains of man, but lower down the river instruments of paleolithic type have been procured by M. Noulet, and may be seen in the Museum at Toulouse.

* Piette, Acad. des Sci. 31 Juil., 1871; Matériaux pour l'Hist. de l'Homme, 1871, p. 494.

Perhaps no cave-deposits that we know are quite so old as the oldest river terrace that has yielded traces of man, still all the earlier ones may be included in the same bracket, and referred to the oldest stone or palæolithic times.

From the caves we cannot get much evidence of the lapse of time. The circumstances that affect the mode and rate of their formation, or the growth of travertine, or the slow infilling of the cave with mud, are far too variable, and dependent upon too many local causes to found on them a date. have myself found modern bottles under as great a depth of stalagmite as elsewhere covers mammoth bones.

I

But from the terraces we may derive some help to form an estimate of the great lapse of time, though we may not as yet assign a term of years. What, then, are these terraces, and how formed? It might appear at first an explanation not quite consistent with known facts to state that all the valleys with which we are concerned in this inquiry were scooped out by the gradual action of the streams, and that the terraces but mark old margins, where the streams once ran at higher levels. Why, it is said, if so, do we not find at every intermediate step of this continuous gradual waste the marginal deposits? Elsewhere* I have more fully dwelt upon this question, pointing out that every river only just hands on along the flat the mud and gravel it receives from higher lands, but at the rapids and the waterfalls it still cuts back its channel, lengthening the lower reaches of the river at the expense of the upper. The terrace generally marks the vertical height of the higher above the lower reach. It is clear that synchronous deposits may be found at the two levels, but it is also clear that, if we see a terrace far above the level of the present stream and far down the valley from the waterfall or rapid that tumbles from the level of that terrace higher up the stream, then we may measure the antiquity of that terrace by the time that it would take the waterfall or rapid to cut back from where it was when the terrace was being formed to where we find it now. Some circumstances we must take account of which would increase the rate of waste, and so reduce the time. If an upheaval take place near the sea where formerly the long low flats were added to, not cut through by the river, then the flood, tumbling over the now-raised soft deposits of mud or sand or gravel into the sea, would soon cut back its channel. Also movements in the hills might cause some changes; or again, a not unimportant thing in chalk districts, the gradual removal of a clay covering which caused the water to collect in runlets first, then streams, would let the water soak into the porous

*Royal Institution, March 24th, 1876.

beds below, to find its way out in springs at lower levels, or, possibly, beneath the sea, and so all denudation by the streams be stopped. No observations have, as far as I can tell, been made in any of the river basins with which we are now concerned upon the rate of retrocession of the rapids or falls, such as would enable us to form a numerical estimate of the number of years that must have elapsed since the implementbearing terrace gravels were left where they now lie.

But there are circumstances that give the impression which, in most of those who have seen many similar examples, amounts to a conviction, that the time must have been in most cases enormously long.

At the Reculvers, on the Thames estuary, a bed of gravel caps the cliff quite 50 feet above the sea. This has flint weapons in it. When the Thames ran at that level down by its mouth, it cannot have run at a lower level by London; yet, as far as we know from old remains, London was as now 2,000 years ago. Teddington, to which they say the tide came up when first it got its name, was then no higher, and so we trace the valley far up into the oolitic hills, so far I doubt whether now we could identify the corresponding levels. How long did it take to cut back such a valley and so far, seeing that within the time of history we know of no great difference in its channel?

So for the Somme. The Romans left what they lost down in the peat quite 80 feet below the terrace on which the city of Amiens stands. This terrace we can trace much further both up and down the valley. Beds of the same age, too, are found at Menchecourt at a lower level. They may be synchronous with those of Amiens, if the rapids then came between. The rapids had passed Amiens before the Roman times. Where are they now? Far back towards central France. How long it took to cut the valley back so far I will not try to speculate, having no data, but I feel that it must be something very great, seeing that the historic period of 2,000 years has done so little.

Another line of inquiry I will mention to conclude with. In the long periods of geologic time races appear and last awhile, and then are not, and a new group of living things represents them in the next succeeding age. How they went out we cannot tell. It was not by cataclysms, for they go one by one, and the deposits tell of slow accumulation; but more as if some gradual changes over various regions of the earth made each successive place in time unsuitable for all the life that once was there. First, those which were most susceptible and able to migrate went off. So nature has arranged for a constant succession upon earth's surface ;