logging railroad bridge

[gacuster]

I'm looking for a picture of a certain type of bridge the short line logging railroads of northern Wisconsin used to cross the Pine and Peshtigo rivers. All that's left of these structures are mounds of small rocks spaced at regular intervals across the stream. I'm guessing that log cribs were placed in the water, filled with rock and heavy logs or timbers placed from crib to crib to form the bridge, but I can't find a picture to confirm this.