Firing on the up roll versus the down roll

From the excellent Perilous Fight by Stephen Budiansky, an account of the naval aspects of the War of 1812. Page 133.

The lopsided casualty figures in most of the Royal Navy’s encounters with the French were largely due to the fact that the French sought to disable and capture their enemy’s ships, while the British sought to kill and maim as many of their opponents as they possibly could. French crews were taught to fire as the ship began its up roll, and they tended to shoot high to disable spars, masts, and rigging. British crews fired on the down roll, straight into the hull. While enough shots low to the waterline could eventually sink a ship, that was not the purpose: it was to send cannonballs crashing directly into the gun crews of the ship lying a dozen yards away. In fourteen major engagements between 1794 and 1806, French losses totaled twenty-three thousand killed and wounded versus seven thousand for the British. One in four British casualties was fatal: more than half of the French sailors’ were.