The position of the ironclads being determined by these considerations, the arrangement of the wooden ships for the attack conformed to the admiral's principle, that the greatest security was to be found in concentrating upon the enemy the heaviest fire attainable from his own guns. As at Port Hudson, a large proportion of the fourteen vessels he purposed to take in with him were of the gunboat class, or a little above it. Resort was accordingly again had to the double column adopted there; the seven ships that had the most powerful batteries forming the right column to engage Fort Morgan. The lighter ones were distributed in the other column, and lashed each to one of the heavier ships, in an order probably designed, though it is not expressly so stated, to make the combined steam power of the several pairs as nearly equal as possible. Among the gunboats there were three that had side-wheel engines, the machinery of which is necessarily more above water, and so more exposed than that of a screw--a condition which, although their batteries were powerful for their tonnage, emphasized the necessity of sheltering them behind other ships during the furious few minutes of passing under the guns of the fort. The sum of these various considerations thus resulted in the fleet advancing into action in a column of pairs, in which the heaviest ships led in the fighting column. To this the admiral was probably induced by the reflection that the first broadsides are half the battle, and the freshest attack of the enemy should be met by the most vigorous resistance on his own part; but it is open to doubt whether one of these powerful vessels would not have been better placed in the rear. Upon a resolute enemy, the effect of each ship is simply to drive him to cover while she passes, to resume his activity when relieved from the pressure of her fire. The case is not strictly similar to the advance of a column of troops upon a fortified position, where the head does the most of the fighting, and the rear mainly contributes inertia to the movement of the mass. It is at least open to argument that a fire progressively diminishing from van to rear is not, for the passage of permanent works, a disposition as good as a weight of battery somewhat more equally distributed, with, however, a decided preponderance in the van. The last of the ships in this column received a shot in the boiler, which entirely disabled her--an accident that may have been purely fortuitous, and to which any one of her predecessors was in a degree liable, but also possibly due to the greater activity of the enemy when no longer scourged by the more powerful batteries which preceded. She was saved from the more serious results of this disaster, and the squadron spared the necessity of rallying to her support, by the other admirable precautions dictated by Farragut's forethought.