Here the Confederates had established their defenses, or more properly speaking, here they had made themselves masters of defenses created by the National Government before a thought of civil war had arisen in any mind. So far as the "back door" approach was concerned--the approach by way of Lake Borgne and the Rigolets and Lake Pontchartrain--New Orleans was adequately defended by the shallowness of the water at critical points. Unless a special fleet of shallow-draught gunboats should be built at Ship Island or elsewhere there was no possibility of reaching the chief city of the Confederacy by that route. Farragut's only hope lay, therefore, in ascending the Mississippi river. His first obstacle was encountered in the mouth of the Mississippi itself. The great river carries with it to the sea a limitless quantity of mud which it deposits in whatever spot there may be ready to receive it. It is credited by the geologists with having created in this way all the low-lying lands from Cairo to the gulf, a distance of nearly twelve hundred miles by the river's course. At the several mouths of the stream it is still depositing mud and still pushing the land out into the gulf. Very naturally its mud deposits create bars at the several mouths. Long after the war was over, Captain Eads with his jetties undertook to compel the current to wash out channels in the principal mouths and thus to render easy the approach of ships to New Orleans. But nothing of that kind had been done in the early sixties, and the Federal fleet that was charged with the duty of reducing the forts and capturing the city must first force its way through shifting mud banks in order to get into the river. The useless mortar schooners entered easily by the Pass á l'Outre, but the vessels that were to do the effective fighting had far greater difficulty. It required three weeks of strenuous night and day exertion to force them through the Southwest Pass--the principal mouth of the river--and even then one of them, the _Colorado_, had to be left outside. Having thus passed the first and purely natural defense of New Orleans, Farragut had next to encounter the artificial defenses of the river itself. These consisted of two forts at the narrowest part of the stream, together with some adjunctive defenses presently to be mentioned. These forts were two very imperfectly armed works--Fort St. Philip on the eastern bank, and Fort Jackson on the western. They mounted about 109 effective guns, some of them of obsolete pattern, only a few of which--estimated at fourteen--were protected by casemates. Captain Mahan, in his "Life of Farragut," tells us that these forts had been largely stripped of their armament, and were very imperfectly equipped for the defensive work required of them.