Cause of the shape of deltas.

instead of tearing down, build up the banks, and although they cannot build higher than themselves, each year's building increases next year's ponding, and so, without scaffolding, they may build infinitely higher than the floods of former years; and this yearly increasing ponding not only raises the deposits on the alluvial plain, but up the unalluvial plain. The banks of an alluvial river being then high enough to accommodate the flood-water till it only just overflows, it is evident that the spring-water of each tributary, though it will increase the volume, will not increase the width of an alluvial river. The flood-water of tributaries is not contained at all, but overflows, and so increases the building of the height of the banks. If man prevents the overflow of an alluvial river, he must consider it as an unalluvial river. He cannot, indeed, increase the width between the natural banks, but he may the width between the artificial banks.

There seems to be a reason in nature for the shape (A) of all deltas. For the centre stream or streams, however they may vary their courses, besides causing the delta to bow out in the middle towards the sea, also cause it to bow up in the middle, along their courses. For all deposits from moving water must die off in the direction in which the water moves. And in this case the

deposits have a lateral slope from the river five or six times as great as their longitudinal slope, from ponding. Thus the water does not return over the general surface traversed, as it left the river, and so denude the banks which it has deposited. In the alluvial plain the flood-water returns to the river by particular longitudinal channels parallel to the river, which it reenters below, or by particular lateral channels cut down to the level of the spring-water. But in the delta the flood-water after depositing its load, escapes to the nearest points of the sea, along the two low outsides of the delta.

In the last century a French nobleman made a bet that he would get an English horse to do twenty miles in one hour. The savans in Paris clearly proved that this was impossible, on account of the resistance of the atmosphere. Gimcrack was, however, imported to France from England. And Dr. Johnson, in giving an account of the affair, concludes thus, Gimcrack, being no philosopher, set to work and did it.'

6

Dii facientes adjuvant, the English for which is 'try.' And if the United States set to work nationally to embank the Mississippi, whatever human skill and energy can do will be effected by that great nation, but not the less for knowing the true principles of the formation of alluvial plains. you have a powerful enemy to contend with,

If

you may as well know his real force and his mode of attack, and what his supplies are, and also what your own weak points are.

And in endeavouring to point out that the natural causes at work in the valley of the Mississippi against Ellet's magnificent schemes are greater than his estimation of them, it is not meant to argue against those schemes in particular, or against the object of those schemes in general. In Holland those who have perished by floods are numbered by hundreds of thousands. But since those who have there enjoyed exquisite existences are numbered by thousands of millions, would any one advocate the desertion by man of the delta of the Rhine? If so, we must desert all those parts of the globe which are richest in the accumulation of soil, therefore in vegetable existence, therefore in animal existence, and therefore in human subsistence and consequently existence.

Liberal, not lavish, is kind Nature's hand,
Nor was perfection made for man below;
Yet all her schemes with nicest art are planned,
Good counteracting ill, and gladness woe.

Nihil est ab omni parte beatum. Is life anywhere without risk of death? Are plague, pestilence and famine, empty words? Are battle, murder, and sudden death mere bugbears to scare the timid? Has vegetation no blight? flesh no

epidemic? But man takes the bite with the buffet.' Liquid lava expels him not from his fruitful fields. Tempests sweep him not from the surface of the ocean, nor fire-damp from the bowels of the earth. But of all the baits at which hungry man rises, none hooks him to such a certainty as the fat valley. From its rank, rich rottenness springs the abundance which gives man ease and time to civilise himself.

The first improvement on the man who fed on acorns and game was the isolated herdsman, who roamed over vast tracts of hill, or plains of poor soil. The rich valleys were thick forests and jungles. When the agriculturist cleared alluvial plains, man became at once condensed and civilised.

Witness, in the Old World, China, India, Chaldæa and Egypt. On the wings of steam modern commerce and colonisation call forth and interchange the glorious products of every valley of the two worlds, uniting all by mutual benefit. We shall not be stopped out of this by an inundation or two. No, nor by anything short of an angel with a fiery sword. On this globe the paradise for man is that alluvial one prepared for him by

RAIN AND RIVERS.