That there are many large tracts of land in different parts of the kingdom, both on the sea-coasts and on the sides of Lakes and rivers, easily attainable, there cannot lie the smallest dunk. It is, therefore, an object worthy of the attention of those who are so fortunate as to possess property of this nature, to have it ascertained by persons of experience in such matters, how far the acquisition of additional portions of land may be adequate to the expense which it may be neces sary to incur in procuring it. But embankments are important in other views than those of gaining gromid by them. When rivers are concerned, one material advantage is the deepening of their courses, by which vessels of greater burden than they admitted formerly, may be permitted to navigate them.
And farther, as embankments become more frequent on the holders of rivers and sea-shores, the intervening distances may become a sort of bays, in which accumulations of shell, mud, sand, gravel, and other matters, may take place by the influx of tie tides; and these, however difficult they may be at first to embank, will in time lie as easy to perfO•m the work on, as the natural bays and creeks are at. this period. In this way many rivers, which in their present state are eight or ten miles in width at their junction or influx with the sea, may in the course of years be reduced to less than half these distances. consequently, such embankments would be equally beneficial to the proprietors of land, and the mer chant or manufacturer, as many rivers would become more easily navigable, and those obstacles which interrupt their months be wholly removed.
In embanking against the encroachments of the sea, it is necessary to ascertain, with great accuracy, the maximum height to which the water rises ; the methods of doing this have been already shown. But as new works of this sort, especially where the banks are large, are liable to subside too much, it may be a proper precaution to take the levels fre quently fir some time after they are completed, in order to guard sgainst any mischief which might arise in this way.
Where the banks are low, this is not, however, so necessary, as it) higher ones, as the settling is always more or less according to their height ; iu low hanks it will of course be very little. In the making of such einbankunents, it is scarcely possible to lay down any general rule in regar 1 to their size or dimensions, as these must he directed by situation and circum stances, under the management of an expert engineer. In
cases where the embankment to be ti allied is to exclude the sea from a piece of low marshy ground, over which it only flows at spring-tides, the work is easy, and capable of being accomplished at no great expense. But where it is intended to reclaim a portion of laud which is covered every tide, in some or creek, or on the sides or windings of some large river in which the tide ebbs and flows, the business will be in some degree more difficult, according to the depth and rapi dity of the current of the water. And where it is proposed to exclude the sea from an exposed situation at the mouth of a river, or in a bay, or inlet, which is uncovered every tide, the operation will be the most difficult and expensive of all, according as it is exposed to prevalent winds, and the depth of the water to be resisted. Each of these situations, therefore, requires a different method of management.
The business of embanking against the sea, when at any considerable distance within high-water mark, is not only the most tedious, but at the same time the most difficult ; as, when the materials are not very good and the work not well per formed, the force of the water at every flowing of the tide will quickly undo all that has been effected. especially if the soil be of a sandy nature, as is often the case in such situations. It' it be a strong clay, as is sometimes the case in marshy places, there will he the less risk of its being washed away. In sandy situations it has been advised by some to lay bun dles of straw or reeds well filstened down, or any other impe diment, to hinder the soil from being carried away by the ebbing tide. Where a sufficient supply of good strong turf cannot be had, other expedients may be tried ; but where such turf can be provided, as is the case in most marshy situations, and where the embankment required is not to exceed the height of four or five feet, it is best to finish the slope with good turf as expeditiously as possible, as the work proceeds ; that is, supposing the length of 30, 40, or 50 feet or yards of it can be completed in a tide, it is better to finish that length to its intended height, than to trace out or a greater extent than can be finished before the tide returns, by which a great deal of the soil might be carried away, and much of the work demolished, which is not so likely to be the case when the slope is finished. Turf which contains the roots of bent or rushes is very good for this use.