THE FRAISE.
Another ponton which was adopted for bridge service may be described as a skeleton boat-frame, over which was stretched a cotton-canvas cover. This was a great improvement over the tin or copper-covered boat-frames, which had been thoroughly tested and condemned. It was the variety used by Sherman’s army almost exclusively. In starting for Savannah, he distributed his ponton trains among his four corps, giving to each about nine hundred feet of bridge material. These pontons were suitably hinged to form a wagon body, in which was carried the canvas cover, anchor, chains, and a due proportion of other bridge materials. This kind of bridge was used by the volunteer engineers of the Army of the Potomac. I recall two such bridges.
One spanned the Rapidan at Ely’s Ford, and was crossed by the Second Corps the night of May 3, 1864, when it entered upon the Wilderness campaign. The other was laid across the Po River, by the Fiftieth New York Engineers, seven days afterwards, and over this Hancock’s Veterans crossed—those, at least, who survived the battle of that eventful Tuesday—before nightfall.
But all of the long bridges, notably those crossing the Chickahominy, the James, the Appomattox, which now come to my mind, were supported by wooden boats of the French pattern. These were thirty-one feet long, two feet six inches deep, five feet four inches wide at the top, and four feet at the bottom. They tapered so little at the bows and sterns as to be nearly rectangular, and when afloat the gunwales were about horizontal, having little of the curve of the skiff.
A CANVAS PONTOON BOAT. FROM A PHOTOGRAPH.
The floor timbers of the bridge, known as Balks, were twenty-five and one-half feet long, and four and one-half inches square on the end. Five continuous lines of these were laid on the boats two feet ten inches apart.
The flooring of the bridge, called chesses, consisted of boards having a uniform length of fourteen feet, a width of twelve inches, and a thickness of one and a half inches.
To secure the chesses in place, side-rails of about the same dimensions as the balks were laid upon them over the outer balks, to which the rails were fastened by cords known as rack-lashings.