s it is necessary to the productiveness of a soil that the warm rainwater should penetrate below the line of vegetation, the drains should be laid at such a depth as to be clear of the plow and spade, and the frost and the tap roots of larger plants. As soils are very rarely broken below eighteen inches from the surface, and roots are known to reach down as far as the soil is rich, while the frost penetrates to an average depth of three feet, it would be safe in districts, affected by frost to lay drains four feet under the surface, and in warmer cli mates at a depth of one foot below the line of cultivation. With a suitable connection between the main and the drains, no soil, no matter how wet it may be, can fail to be reduced to a condition fit for cultivation. As localities differ widely in their physical features, and various circumstances compel special treatment in almost every case, it is not practicable to designate, beyond the general principles that should govern the construction and arrangement of reclamation works, any form of embankment, drain, sluice, or pump to be adhered to under all circumstances. Locality, prevailing winds, cli mate, range of tide, strength and velocity of local currents, the nature of the soil and vegeta tion, all combine to altar the character of the works, and a common standard would be impos sible. It may be said of all these that locality is the one on which all the others depend for their importance. We find as we traverse the Atlantic coast of this continent a great many varieties of soil in the marshes. This is owing to the differ ent kinds of vegetation produced on these marshes, or which composed their soil originally, and the rapidity of decomposition of this vege table material in the soil. With locality, climate varies considerably, and climate regulates the character and growth of plants, their develop ment, their time of maturity and of decay. A natural result of all this influence must be that in localities possessing warm climates the vege tation is more varied, more luxuriant, and con sequently enters more largely into the composi tion of the soil than in places where the climate is less favorable for the development of vegeta tion. The rapid growth and quick succession of crops must tend to a large annual deposit of vegetable matter on the surface, which, before it becomes thoroughly decayed, is itself a soil, from which other plants spring, and the deposit becoming in this way more rapid than the decay which should convert it into vegetable mold, a soil is formed many degrees less dense in its structure than that of a place where the climate is colder and the growth of vegetation is slower and It has been remarked that spongy, vegetable soils will retain water, when sandy and porous soils will not, and the work of drainage will be increased in proportion to the quantity of vegetable matter found in the soil. It also occurs that this rapidly formed soil is less fitted for the construction of water tight embankments than that of a more gradual deposit, on account of its being more permeable to water, and it is often found necessary, there fore, to reject the soil we proposc to reclaim, as a material for the embankment, and use that from another place. While locality and cli mate materially affect the manner of reclama tion, prevailing winds also exercise an influence by their action on the tidal wave. In exposed situations, the winds exercise this influence to such a degree as to necessitate a complete change in the plan of reclamation, especially on the tidal marshes along the coast and the shores of our rivers. According to the course of the river, against the overflow of which embank ments are erected, as well as the direction of the opening by which the waters reach the sea, the wind at certain seasons, causes a raising of the tide wave above its ordinary level, and of course necessitates higher and stronger embankments to resist it. Reference is not made to the semi monthly occurrence of spring tides, but to the powerful effect of strong winds on the surface of water, forcing it in the direction in which it , blows. When a strong wind and a spring tide occur at the same time, the tide will be raised over the level of spring tide in proportion to the strength of the wind; and when both meet a heavy freshet after a rain storm, the increased volume of the stream is not unlikely to overflow the banks, and inundate the surrounding coun try for many miles, doing much damage to property, and sometimes causing loss of life. In level countries the wind blows in a downward direction at an angle of something over 18° with the horizon. The pressure of the wind is in proportion to its velocity—the former increases as the square of the latter. The following table of velocities and pressures of the wind is taken from Burnell's Hydraulic Engineering: An instance of the effect of strong wind on water is mentioned by Franklin. A pond, nine miles-wide, and of an average depth of three feet, was acted on by a strong wind, which forced the water from one side so that it was laid bare, and the depth of water on the other side was increased to six feet. Next to the influ
ence of winds and waves on reclamation works, is the action- of currents. Where the shore is concave, it would be imprudent to erect embankments close to the water-line, unless some protection in the shape of masonry or pil ing be placed against the wearing action of the current; while, on the other hand, when the shore is convex, the embankment may be placed even at the water's edge, as the fore-shore will continue to gain in the latter case as it loses in the former. In like manner, on sea-coast embankments, where the bank is likely to be washed by any of the numerous currents cre ated by the movement of the tides, the greatest caution should be exercised in protecting the works from injury, and the exterior slopes should be strengthened in the best manner to resist the action of the water. To preserve the embankment against the damaging effects of frost, it is well to cover the face of the exte rior and interior slopes with thick sods, by which a protection is afforded to the bank by the cover ing of grass, and the frost is not permitted to penetrate so deep into the soil composing it. In California it is estimated that there are 3,000,000 acres of swamp lands, which when drained will be the most valuable in the State.
Since 1870 this work has been prosecuted with energy, one company alone having a nominal capital of $12,000,000, and owning, in 1872, 120,000 acres of land in the delta of the Sacra mento and San Joaquin rivers, and embracing we believe, both salt water and fresh water tide land. In the West there are large areas of what are known as low prairie, not marshes, but lands suffering from excess of water in the spring and interspersed through with ponds seldom dry. In Iroquois county, Ill., vast areas have been reclaimed by a careful system of drainage, ren dering them among the most valuable lands in the State. In Iowa there arc large tracts of the same nature requiring comparatively little expense to fit them for the plow, also many river bottoms of large extent, subject to overflow in floods occur ring both in spring and summer. A good begin ning has also been made in that • State in the reclamation of these lands by surface drainage and by embankments. In the West there has been so much unoccupied land requiring no drainage, that until within a few years, but little attention has been paid to systematic drainage. It is now found that these lands are the richest in the several States, and that they may be re claimed at a comparatively light cost. Hence, capital and energy have sought these channels of industry, and have acquired large tracts worth many millions of dollars in the aggregate, and adding a large yearly surplus of agricultural pro ducts for export, or for consumption at home, through being fed to fattening cattle and swine. There is another class of soils, the richest in the world, lying along the great rivers of the Missis sippi valley, especially those vast areas near the Mississippi and Missouri rivers, subject to over flow in great freshets, because lying below the high water line, that if protected at all must be so by expensive systems of levees, requiring large outlays of capital. This system has been in operation in the South many years, and yet only imperfectly accomplished, since with streams carrying a large amount of sediment, the natural consequence of diking the banks, is to cause a deposit of sediment at the bottom of the stream, so that, the bed of the river may come to be ultimately higher than the land itself. This is found to be the case in some of the streams of Europe, that have been diked for many centu ries. The same effect seems to be going on in the lower Mississippi, the result being that the levee must be raised constantly higher and higher. Natural 'reasoning will show that there is a limit beyond which human art may not strive, and already, a number of schemes have been advo cated to take the pressure from the banks. The recurrence of destructive inundations like those iu the last decade, (1876 and 1881), in the upper Mississippi, and in 1881 along the Missouri as well, would seem to point to the fact that some means must be taken to ease the pressure of water, in very high floods, by straightening the channel, and causing a freer flow, with increased velocity, in. connection with higher and more substantial embankments. The floods of would seem to teach this plainly. Another fact seems plain. The lands lying along the Missis sippi are of sufficient value to bear a large outlay in perfecting the embankments. For whatever the cost, it must be done thoroughly. The dam age by the flood of 1881 would undoubtedly cover the entire cost of the system of embank ments or levees, or at least the recurrence of another such %a one certainly would. It would seem to be a wise course that such disasters to property be prevented, if in future.