to the Firft Volume. GOL

will no doubt ftir up the mud or fand, and carry great quantities of them along with the current on the flowing of the tide; and when the tide ebbs, although fome

of the lighter particles will be carried away again, yet it is natural to{uppofe the

heavier ones will be left behind. If the thores are bold and rocky, except juit near the entrance of the river, there will be the lefs of this mud; but, indeed, on fuch fhores there can be little or no occafion for embanking, unlefs, perhaps, in fome creeks, narrow at the entrance and fpreading wide aboye. From fach ereeks, if the fea were excluded, a great deal of land might probably be gained*.”

It is remarked, that‘ embankments againft rivers may be divided into two forts; namely, thofe for preventing their encroaching on the adjacent lands, and for protect- ing thofe lands and the neighbouring level country from being oyerflown when the water rifes above its ordinary level. It may be obferved, that where the courfe of ariver is a ftraight line, or nearly fo, it hardly ever makes any encroachment upon its banks, unlefs, perhaps, in very large rivers, when tbey rife above their com, mon level either owing to an increafe in the waters, or to their being in fome de- gree affected by the tides. In cither cafe the waves occafioned by a firong wind, where the river is wide, will moulder away the banks on that fide upon which it blows, unlefs prevented in proper time. This may be done either by fecuring the bank properly with ftones, or by driving a row of Jong piles pretty clofe together, at a little diftance from the fhore; the piles being of fuch a length, and fo driven, that their tops may be always above the higheft rife of the water. It is furprifing the effet that piles driven in this manner have in refifting the power of waves, Some years ago, when on.duty as.an engineer at a fort near Portfmouth, built.on a point of land much expofed to the fea, the waves:made fuch‘havock that the walls on that fide were conftantly giving way although built inthe moft fubftantial man- ner, and having bulwarksiof Jarge‘heavy fione befidesto prote@ the foundation: however, all would net.do; thofe bulwarks were foon knocked to pieces, and feveral times the wall itfelf. At length it was propofed to drive a number of piles at about

- forty to fifty yards from the fort. Thofe piles were twelve or fifteen inches in dia- y y¥

meter, and driven about.one diameter from each other, nearly in a ftraight line,

parallel to the wall where the waves did fo much damage.‘They were driven into

the ground with a pile engine‘till:perfeétly firm,:perhaps eight or nine feet deep,

and about two feet of ithe top of them eft above the level.of high water mark.

After this was done‘the walls received no further injury, the fpace between the

piles and the fort being always perfectly finooth shawever tempeftuous the waves * Beatton in, Communications tothe Board.of Agriculture, Vol. II.

SAG 2,