228

PRACTICAL CONSTRUCTION.

soil as will at least cover the face of the embankment from d to e , eventhough it should have to be made up with gravel. The whole face will

Fig. 21$.

THI MOST BFrJCTUiL IMBtNKMENT ON A ORAVSLCT BOTTOM.

require to be turfed; for, should any breakage take place on the face, the gravelforms such a bad element that it will all go by the run. A ditch is sometimesformed behind the embankment for leakage water ; this, however, unless undercertain circumstances, should not be formed, it merely weakening the stabilityof the whole by breaking the surface, and causing the water to leak morereadily from the bottom of the ditch.”

987. Where the banks of a river are perpendicular, and composed of looseor friable earth, the best plan to prevent the continual washing away by theaction of the river, is to slope the bank, as shown in fig. 219, from a to b to the

surface of the water. This should bedone early in spring, and the slope coveredwith turf, or sown “ very thick with theseeds of some small mat-rooted grass : thecreeping meadow-grass (Poa reptans) isa proper grass for this purpose.” Thebreast of the bank, from b to c, is formedby throwing in small stones about the sizeof a man’s hand, the slope being a con-tinuation of that from a to b. Thesestones wall be best suited for the purposeif taken off cultivable land, and greatcare should be taken to make the slope or face of the heap as smooth aspossible.

988. On the use of stones for the protection of river-sides, Mr George Stephens,in his work on Irrigation and Draining, has the following: “ The sheathing orprotecting of river-sides with small stones is so very simple in itself, that,where stones are to be had, there is not the least difficulty in preserving theirbanks at a trifling expense, provided the injured part be immediately filled.Instead of putting a few cartloads in heaps at random along the affected part,they ought to be laid regularly along the affected part; for, in the first case,they only serve to break the cement, forming partial waterfalls where there werenone, whereby the injury is increased instead of diminished ; but in the lattercase the bank will be secured. Even in districts where stones cannot be had,half the ravages committed by watercourses winding through low groundsmight be prevented by timely and judiciously keeping down the perpendicularbanks, and sowing or planting the skqies with small-rooted aquatic plants, suchas bog-reeds, sedges, water spiderwort, rushes, and seeds of any kind of plantswhich are known to thrive in and near water.”

Fig. 219.

COTTINO OF R1VB.R-BANK9 TO PRSVINT WASH1NO AWAT.