The first naval achievement of the war which was attended with any important result was the successful attack of the fleet under Commodore Stringham, accompanied by General B. F. Butler, and his land forces, upon Forts Hatteras and Clark, at Hatteras Inlet, North Carolina. [Illustration: ATLANTIC COAST FROM FORTRESS MONROE TO FORT MACON. ] The whole length of the Atlantic coast from Chesapeake Bay to Charleston has a peculiar character. A long line of low, sandy beaches, of variable width and elevation, rise above the surface of the ocean, broken at occasional intervals by a passage, ordinarily of shallow depth of water, communicating from the open sea with the lagoons inside. These bodies of water, by the indentations of the main land and the mouths of the rivers, expand into large bays, of which Pamlico and Albemarle Sounds are the principal. These two form capacious highways of safe and easy communication along the coast, and through the Dismal Swamp Canal connect with the Chesapeake Bay, on the north, at Norfolk, Va. At the south-western extremity of the long, narrow island or beach, the outer angle of which has received the name of Cape Hatteras, and which gives its name to the inlet, the rebels had erected two strong fortifications known as Forts Hatteras and Clark. Captain Samuel Barron, late of the United States navy, was here in command of the naval forces, while Colonel William F. Martin, of the Seventh North Carolina Volunteers, and Major W. S. G. Andrews, commanded the garrisons. Hatteras Inlet was one of the principal passages through which the vessels of the Confederacy made their way, in defiance of the blockade, and which it was desirable to command with the Federal forces and fleet. An expedition was accordingly planned, and the preparations were far advanced when General Wool reached Fortress Monroe. All things having been made ready, on the 26th of August, the fleet, under Commodore S. H. Stringham, left Hampton Roads for its destination. It consisted of the flag-ship Minnesota, Captain G. A. Van Brune, having in company the United States steamers Wabash, Captain Samuel Mercer; Monticello, Commander John P. Gillis; Pawnee, Commander S. C. Rowan; Harriet Lane, Captain John Faunce; United States chartered steamers Adelaide, Commander Henry S. Stellwagen; George Peabody, Lieutenant R. B. Lowry; and tug Fanny, Lieutenant Pierce Crosby, all of the United States navy. The transports Adelaide and George Peabody, towing schooners with surf-boats on them, and the Monticello and Pawnee surf-boats only. General Butler embarked his land forces on the two transports Adelaide and George Peabody, having with him five hundred of the Twentieth New York regiment, Colonel Weber; two hundred and twenty of the New York Ninth regiment, Colonel Hawkins; one hundred of the Union Coast Guard, Captain Nixon; and sixty of the United States Second Artillery, Lieutenant Larned.