DESTRUCTION OF BRIDGES AND FORDS.
§ 264. When four three-inch guns fire upon a bridge 1,000 yards distant with shells it will in the general case be destroyed in about 10 or 15 minutes.
§ 265. A wooden bridge is rendered impassable by tearing up the planks, in 15 or 20 minutes; a brick or stone bridge in 30 minutes or 1 hour. To burn a wooden bridge at least half an hour’s preparation is required. To prepare to blow up a wooden bridge at a particular time, 90 minutes; a brick or stone bridge, 2 or 3 hours.
A ford may sometimes be destroyed in 1 or 2 hours.

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