( so )

were placed twenty feet asunder, and connectedwith chains, as well with each other as withthose in the rear line ; the masts in the one linecovering the intervals in the other. These lineswere twenty-four feet asunder, and the chainsallowed to hang slack, so as to be about twelvefeet below the surface of the water. Twostrong thirteen-inch cables were stretched alongthe whole line of masts, and set as tight as pos-sible, securing them, by lashings, to both ends ofeach mast. Four gun-boats were placed in ad-vance of this boom, to assist in its protection;and on each bank of the river was placed abattery of three travelling eighteen-pounders;while light boats were constantly kept in readi-ness, with fire-grapplings, to meet and anchoranything that might be drifted down the stream,before it reached the boom; and during thenight, guard boats, and boats of observation,were kept constantly rowing about.

The chief disadvantage in substituting cablesfor beams is, that the navigation of the rivercannot be opened, by removing one or two boatswith their proportion of floor, as shown atpage 81 , 82 ; for the cables being stretched bycapstans from bank to bank, and only borne bythe boats, cannot be partially removed, to with-draw a part of the bridge. Cables are, more-over, expensive, and with every precaution,