The naval battery, which, in the circumvallation was “Number Four,” was constructed entirely of the material at hand, very plentiful and sewn up in bags. It had two traverses six or more feet thick, the purpose of which was to resist a flanking, or in naval parlance a “raking” fire, which might have swept the inner space clean. The guns were mounted in their own ship’s carriages on platforms, being run out with side tackle and hand-spikes, and their recoil checked with sandbags. The ridge on which the battery was planted was opposite the fort of Santa Barbara, parallel with the city walls and fifteen feet above their level. It was directly in front of General Patterson’s command. In the trenches beyond, lay his brigade of volunteers ready to support the work in case of a sortie and storming by the Mexicans. The balls were stacked within the sandy walls, but the magazine was stationed some distance behind. The cartridges were served by the powder boys as on shipboard, a small trench being dug for their protection while not in transit. Here then was “the accumulated science of ages” on the plains of Vera Cruz applied to the naval art, and directed against the doomed city, erected by one of the greatest engineers of the age, Robert E. Lee, with ordnance served by the ablest naval artillerists of the world, the pupils of the leading officer of the American navy, Matthew C. Perry. Most of them had been trained under his eye at the Sandy Hook School of Gun Practice. They were now to turn their knowledge into account. Not a single random shot was fired. The exact range of each of the familiar guns was known, and the precise distance to the nearest and more distant forts. The points to be aimed at had been mathematically determined by triangulation before a piece was fired. Shortly before 10 A. M. on the 24th of March, while the last gun mounted was being sponged and cleared of sand, the cannon of Santa Barbara opened with a fire so well aimed that it was clear that the battery was discovered. A few daring volunteers sprang out of the embrasures to clear away the brush and unmask the work. The chapparal was well chopped away to give free range to the officers who sighted the pieces, the aim being for the walls below the flag-pole. The direct and cross fire of seven forts soon converged on the sandbags, and the castle sent ten- and thirteen-inch shells flying over and around. When one of these fell inside, all dropped down to the ground. For the first five minutes the air seemed to be full of missiles, but our men after a little practice at houses and flag-staffs soon settled down to their work to do their best with navy guns. One lucky shot by Lieutenant Baldwin severed the flag-staff of Santa Barbara; at which, all hands mounted the parapet and gave three cheers. In order to allow free sweep to the big guns, the embrasures had been made large, thus offering a tempting target to the enemy.