No uncertainty of this kind is felt in tracing the history of the purely lacustrine deposits: for these seldom are deficient in the characteristic organic forms of fresh water. Perhaps in both of these classes of phenomena, we may reasonably look for more zealous and persevering research than have been lately bestowed upon them. Old lakes deserve all the attention of palaeontology and physical geology: for their history goes far back on the scale of geological time, and by their contents we know at least somewhat of our "native" land in Pleistocene, tertiary, oolitic, and perhaps carboniferous periods. Nor is any survey of the primeval world at all complete which fails to inquire into the river action of early geological times, since this action is an index of the state of the land, and many of our valleys are even of palæozoic date, and contain conglomerates heaped in them by palæozoic, mesozoic, and cainozoic waves. And, even where no trace of the valley remains, we not infrequently mark the positive effect, or the probable vicinity, of a great ancient river. Thus, in the Weald of Sussex, we have such a combination of reliquiæ as to mark, not a bay of the sea, but an estuary nourished by a richly wooded river; nor can we easily escape from the conviction that the alternating sediments of the coal formation in many cases require the intervention of powerful streams from the land. To show where that land was posited, and what was its character, may be an impracticable problem, but it cannot be prosecuted without some indirect advantages, perhaps more than commensurate with the effort which it requires.
The recent work of Mr. Chambers, entitled "Ancient Sea Margins," may be perused with advantage for many examples of old sea and tide river terraces at various stated levels, round a great part of the British shores, and along many of the valleys.
Ancient Valley Formations.
I have some time ago proposed this term, for the
