BRIDGES FOR GULLIES.
wooden frameFig. 286.—Frame For Bridge.
Fig. 286.—Frame For Bridge.
Fig. 286.—Frame For Bridge.
For small gullies which cross roadways or lanes in farms, and are not the beds of constant streams, but are occasionally filled with surface water, a very simple bridge is sufficient. One like that shown infigure 286is as good as any. The sills,a,a, are sunk in a trench dug against the bank and at least to the level of the bed of the creek. The cross-sills,b,b, are not mortised into them, but simply laid between them. The pressure isall from the outside, hence it will forcea,a, tighter against the endsb,b, which must be sunk a little into the bed of the creek at its lowest point. The posts are mortised into the sills,a,a, and plates,c,c, andd,d, upon which the planks are laid. Props may be put against the lower sides of the posts to hold the bridge against the stream.
simple bridgeFig. 287.—Convenient Farm Bridge.
Fig. 287.—Convenient Farm Bridge.
Fig. 287.—Convenient Farm Bridge.
A cheap but practicable bridge is shown infigure 287. Two logs are laid across the gully, their ends resting on the banks, and to them puncheons or planks are spiked to form the bridge. Stout posts, well propped and reaching above the highest water mark, are placed against the lower side of the logs. If the creek rises, the bridge, being free, will be raised on the surface of the water, while the posts will prevent its being carried away. Should it not rise with the water, it opposes so little surface to the current that the posts will hold it fast.