By the evening of the 3d of July, the preparations for the bombardment of the Emperor's castle were completed; ditches had been dug to the extent of more than two thousand yards, and the batteries some of which were within musket shot of the walls, were armed with six sixteen-pounders, ten twenty-four-pounders, four eleven-inch mortars and six nine-inch howitzers. In order to secure themselves against any general attack, the French had likewise established communications between the different bodies of their forces by roads across the field and gardens, while they had barricaded or otherwise fortified the lanes and passes which separated their positions from those of their enemies. All this was done notwithstanding the bold and persevering efforts of the Algerines, who maintained an almost constant though ill-directed fire on the workmen from their batteries, and annoyed them by frequent sorties. At day break on the morning of the 4th, a rocket was thrown up from the quarters of the French commander as a signal for the commencement of the attack, and all the batteries were instantly opened on the devoted fortress. Its dauntless defenders returned the fire, which they continued for some time with great spirit but with little effect, their balls and shells causing scarcely any damage to the persons or works of the besiegers. The walls of the castle, high and entirely exposed, soon exhibited evidences of the skill of the French artillerists; the materials of which they were built, crumbled under the “iron shower” falling incessantly upon them; and the embrasures, made unnecessarily wide, afforded but little protection either to the guns or to those engaged in serving them.