ON CHANGES IN THE DISPOSITION 1*2 the Mosaic deluge. The other case is more abstruse, and of peculiarly difficult investigation. In either, the source of the alluvia cannot be mistaken ; from that regularity of stratification which can only occur in the case of a river deposit, the facts being such as not to admit of a former lake ; and if the original stream cannot be found in the neighbourhood, the only re maining solution is, that of the lowering of the moun tains, through the usual waste; thus cutting oft’ that supply of water which originally produced a large river where there is now but a rill, or perhaps nothing. Of such extensive losses of land there can be no doubt, as I shall show hereafter; while it is obvious that higher lands must have produced larger rivers. And when I find that the most striking cases of this nature occur at the foot of trap ridges, so especially bearing marks of great waste, this solution becomes even more satisfactory. In concluding this branch of the action of rivers, it is now evident that I but partially agree with those who, in their eagerness after a system, have asserted that all valleys have been excavated by their rivers: while it must be plain that the long-continued dispute among geologists, whether the beds of rivers had been prepared, or w r ere made by themselves, is but the dis pute of children in this science. It is evident that the original drainage consisted in the irregularities of the elevated rocky surface; nor can I understand how this necessity should have been overlooked by those with whom this forms an essential part of the wdiole system. Were the rivers the causes of the valleys, every land should have been a table of mountain, without other discontinuity than a fissure. Were this theory true, how is there any lake at all; above all, how arc there such lakes as Loch Ness, many hundred feet deeper than the surrounding seas? No river could have ex-