The possession of the north side of Sevastopol offered the Allies considerable advantages.[237] The town, barracks, dockyards, and arsenal are built on the south side of an extensive creek, deep enough to float the largest ships of war, which runs from the sea in an easterly direction four miles inland, 1000 to 1200 yards in breadth. This inlet, forming the roadstead or harbour of Sevastopol, is defended at its mouth by several strong forts, some of those on the north side being perched on cliffs 100 feet high. The northern bank entirely commands the south side, and rises from the water’s edge more abruptly than the latter. These things were known to the Allies before they landed in the Crimea. It is obvious that, if the invaders could have established themselves on this northern bank, they would have taken the town and some of the forts in reverse; and that, if they could have brought up sufficient guns of the requisite calibre, the fortress itself would have been untenable, and the destruction of the ships in the harbour ensured by the force of plunging fire directed upon them. ----- Footnote 237: See Map No. 5, p. 182. ----- While we lingered on the Alma, General Menshikoff had not been idle, and he determined to secure all the advantages which the Russian fleet of the Black Sea might be able to confer. It was hopeless to suppose that this fleet could cope with our own magnificent ships which lay outside the harbour; and indeed, ever since the battle of Sinope, it had been carefully kept out of harm’s way. The only use to which it could be put, was to convert it into an addition to the land defences of Sevastopol; but even then, it would be exposed to danger, for the enemy had a wholesome dread of what the historic daring of British seamen is capable of achieving when directed by an enterprising commander. On the night of the 22nd, therefore, he effectually barred the entrance of the roadstead by sinking seven vessels, and by constructing a boom across it, and thus he secured his shipping from any direct attack which our navy might have contemplated. Hence, the Russian war-ships became stationary floating batteries, and their function was to play their guns upon the ground that bordered the roadstead. For this device, also, the Allies must have been prepared, and might have taken it into consideration before even they started on the expedition. Now, the plateau on the top of the heights overlooking the town from the north, was much less (if at all) exposed to the enemy’s naval artillery than the ground over which the invaders must advance, if they meant to deliver their attack from the south; and the fire directed upon this plateau would be uncertain and inefficient, since considerable portions of it were out of sight of the ships below.