ravines through them backward from the sea, the rest must wait for disintegration and the wash of rain. The sea begins the deltas and alluviums and preserves them now. And in this sense the sea may be said to fill valleys in, instead of scooping them out. This subject will be treated in the last chapter.

But besides this No. 1 theory of his own, which I shall call the submarine theory, Lyell freely adopts three other theories, each of them contradictory to his own theory, and each contradictory to the other. No. 2, a theory of Mr. Hopkins's that valleys are cracks formed in the igneous elevation of the land, and Lyell says that Mr. Hopkins accounts for these 'by mathematical methods;' I shall call this the igneous mathematical theory. No. 3, the erosion of their banks by rivers, the erosion theory; and No. 4, the subaerial denudation from disintegration and the wash of rain, the subaerial theory. All these four theories Lyell uses, sometimes each as if it was his only theory, and always each as if it were consistent with the other three. Indeed, I think I shall show that a fifth and a sixth theory for the formation of valleys may fairly be placed to Lyell's credit (or discredit?)

Let us try if one theory will not suffice: the last of the four, the subaerial theory; and if in

supporting this theory against the three first, arguments are sometimes used against all three generally, and sometimes the fight is shifted abruptly from one particular theory to the other, the blame must not be laid on the writer of this. If either of the first three theories were true; Valleys formed according to three out of if valleys were formed by submarine denudation, four of Lyell's theories should either by waves or currents; or if they were formed by 'mathematical earthquakes,' or by the erosion of their banks by rivers, in all these cases valleys ought to be more bare of soil than any other parts of the earth. But they are more rich in soil than any other parts of the earth.

be bare of soil,

Valleys are rich in soil.

Soil is simply rotten subsoil (mixed with vegetable remains). But there are particular spaces so steep (precipices) that even gravity or wind, independent of the wash of rain, would never suffer a grain of soil to remain on them for an instant. Soil is not the less in perpetual formation on these spaces. The faces of precipices and bare rocks rot, and thus soil is in perpetual formation over the whole surface of the earth. And from the whole surface of the earth it is in perpetual movement, by the wash of rain to the bottom of the sea. This travelling rotten part of the earth is the only part which supports vegetable existence, and consequently animal existence.

The reason why valleys are richer in soil than

other parts of the earth, is, that they are the roads which soil travels to the sea. And the same cause which has excavated valleys, and which still denudes them-rain-also deposits in them. And valleys always hold soil as rivers always hold water, though the soil and the water are both in transitu. Directly as each valley lengthens, its longitudinal slope becomes gentle. Directly as it widens, its lateral slope becomes gentle. And directly as the gentleness of the slope of each valley is the accumulation of soil. For as rain takes the soil from the hill-top down the valley to the sea, in proportion to the flatness of the valley will deposit of soil exceed denudation. Man's subsistence, and therefore his Accumulation existence, depend very much on these vast accu- sistence and mulations of soil. And therefore (I was going existence to say) it is of infinite consequence to man to dependent on know the principles on which depend the forma- of soil. tion, accumulation, and denudation of soil. But

poor hungry sinner'-does not wait for his dinner till he is shown where to get it by a scientific theory. He finds by practice where he can grow the crops which support him and his domestic animals. There are, however, infinite myriads of cases where denudation of soil may be retarded by man, and where accumulation of soil may be facilitated by him, if the true principles

of man's sub

therefore man's

greatly

accumulation

on which these depend are understood. And so far the knowledge of these principles may be said to be of consequence to us all, quicunque terræ munere vescimur, from the labourer to the throne, reges sive inopes erimus coloni.

sive

But besides our food, besides producing and supporting the vegetable crops and animals most valuable to man, alluvial deposits are the magazines of the minerals most valued by man. Platina, gold (5500l. worth has been picked up in one nugget), tin, diamonds, and precious stones, are sifted, sorted, and stored by Nature in these beds, during her universal operations of disintegration, denudation, and deposit. The subject, also, is of vital importance-the very foundationstone-in theories of geology and physical geography; also in engineering questions touching harbours and docks, the embanking of alluvial rivers, the reclaiming of land from the sea or marshes (works which place in daily jeopardy millions of lives), and the drainage, sewage, and supply of water to the cities of the plain.' And last, and oh, ye gold-finders and utilitarians, not least,

the boundless store

Of charms which nature to her votary yields,

the subject explains the origin even of these. The alternation of the ravine and ridge, the hill and

dale, the exquisite beauty of the earth's surfaceof all that we see of the earth-the dread magnificence' of the Alpine chasm, and the rich loveliness of the alluvial vale, are the everchanging products resulting from (start not at the bathos) the daily wash of rain.'

In addition therefore, to what I published in the second edition of the Tree-lifter,' I shall devote this treatise to what I conceive to be the errors of Lyell on this important subject. For I think that I can show that this illustrious writer is here not only contradictory to what we see in nature, but completely contradictory to himself throughout.