To the general defense the Confederates had here brought two other factors, one of a most important and as yet unknown power. As the sand bank extending eastward from Dauphin Island was to some extent passable by light gunboats, a line of piles was driven in the direction of Fort Morgan nearly to the edge of the channel. Where the piles stopped a triple line of torpedoes began, following the same general course, and ending only at a hundred yards from Fort Morgan, where a narrow opening was left for the passage of friendly vessels--blockade runners and others. Had the electrical appliances of the Confederacy been at that time more highly developed, this narrow gap would doubtless also have been filled with mines, whose explosion depended upon operators ashore. As it was, the torpedo system employed at Mobile, with some few possible exceptions, was solely mechanical; the explosion depended upon contact by the passing vessel with the mine. To insure this, the line was triple; those in the second and third rows not being in the alignment of the first, but so placed as to fill the interstices and make almost impracticable the avoidance of all three torpedoes belonging to the same group. These arrangements were sufficiently well known to Farragut through information brought by refugees or deserters. They--the power of the works, the disposition of the torpedoes, the Tennessee and her companions--constituted the elements of the problem which he had to solve to get his fleet safely past the obstacles into the bay. Although not disposed to lay as much stress as others upon the torpedoes, which were then but an imperfectly developed weapon, prudence dictated to him the necessity of passing between them and the fort; and this was fortunately in accordance with the sound policy which dictates that wooden vessels engaging permanent works, less liable than themselves to penetration, should get as close as possible to the enemy, whose fire they may then beat down by the rapidity of their own. There were certain black buoys floating across the channel, between the piles and Fort Morgan, and it was understood that these marked the position of the torpedoes. The admiral's flag-lieutenant, Lieutenant (now Captain) John C. Watson, had examined these buoys in several nightly reconnaissances; but, although he had not been able to discover any of the mines, the assurances of their existence could not be disregarded. His examination doubtless had some effect upon the admiral's instant determination, in the unforeseen emergency that arose during the action, to pass over the spot where the hidden dangers were said to lie; but in the dispositions for battle the order was given for the fleet to pass eastward of the easternmost buoy, where no torpedoes would be found.