the Rigolets will defend the entrance by one passage into Lake Pontchartrain, and also into Pearl River, which empties into the Gulf at that point.  Between the Rigolets and Mobile Bay there are but two inlets which deserve the name, those of St. Louis and Pascagola, the entrance into which is too shallow even for the smallest vessels; and from the Rigolets to Mobile Bay the whole coast is equally shallow, affording the depth of a few feet of water only.  Cat Island, which is nearest the Rigolets, is about 7-1/2 miles distant from the coast and 30 from the Rigolets.  Ship Island is distant about 10 miles from Cat Island and 12 from the coast.  Between these islands and the coast the water is very shallow.

As to the precise depth of water in approaching those islands from the Gulf, the report of the topographical engineers not having yet been received, it is impossible to speak with precision; but admitting it to be such as for frigates and even ships of the line to enter, the anchorage at both is unsafe, being much exposed to northwest winds.  Along the coast, therefore, there is no motive for such strong works on our part—­no town to guard, no inlet into the country to defend—­and if placed on the islands and the entrance to them is such as to admit large ships of war, distant as they are from the coast, it would be more easy for the enemy to assail them with effect.

The position, however, at Mobile Bay is essentially different.  That bay takes its name from the Mobile River, which is formed by the junction of the Alabama and Tombigbee, which extend each about 300 miles into the interior, approaching at their head waters near the Tennessee River.  If the enemy possessed its mouth, and fortified Mobile Point and Dauphine Island, being superior at sea it would be very difficult for us to dispossess him of either, even of Mobile Point; and holding that position, Pensacola would soon fall, as without incurring great expense in the construction of works there it would present but a feeble resistance to a strong force in its rear.  If we had a work at Mobile Point only, the enemy might take Dauphine Island, which would afford him great aid in attacking the point, and enable him, even should we succeed in repelling the attack, to render us great mischief there and throughout the whole Gulf.  In every view which can be taken of the subject it appears indispensable for us to command the entrance into Mobile Bay, and that decision being taken, I think the considerations which favor the occupation of Dauphine Island by a strong work are conclusive.  It is proper to observe that after the repulse before New Orleans in the late war the British forces took possession of Dauphine Island and held it till the peace.  Under neither of the reports of the Board of Engineers and Naval Commissioners could any but sloops of war enter the bay or the anchorage between Dauphine and Pelican islands.  Both reports give to that anchorage 18 feet at low water and 20-1/2 at high.  The