It was in reference to such a piece of transfer that the Secretary of the Treasury, John A. Dix, sent to New Orleans that famous telegram which thrilled the whole North:-- "IF ANY ONE ATTEMPTS TO HAUL DOWN THE AMERICAN FLAG, SHOOT HIM ON THE SPOT!" Great was the peril. More vessels must be had, and that at once. The seventeen warships in foreign ports were called home, scores of steamers were bought and dozens were built as quickly as possible. =327. Urgent Need of Vessels to blockade Southern Ports.=--One of the most urgent needs for a navy was to blockade the Southern ports. This was to be done by stationing well-armed ships near the mouth of every harbor to seize any vessel trying to get out with a cargo of cotton, or to capture any ship coming in with supplies. "Running" this blockade was a profitable but dangerous business. But we can judge whether our gallant navy did its duty in watching the eighteen hundred miles of Southern coast line, if we remember that during the four years of the war the Union blue-jackets captured or destroyed over fifteen hundred blockade runners--more than one a day. =328. Naval Operations on the Western Rivers.=--The Confederates had fortified many cities and important bluffs along the Mississippi River and its branches, and had built many heavy gunboats. Our government had at first not a single gunboat to meet them. Something must be done very soon. In less than a hundred days there were built at St. Louis, from the keel up, with powerful engines, heavy armor plate, and cannon, eight powerful gunboats, all ready for action. These ironclads, with some mortar boats, did effective service at the capture of Forts Henry and Donelson, of Columbus, Memphis, and Vicksburg, and all along the rivers. =329. How New Orleans was protected against an Attack by the Union Forces.=--While the Union ironclads were fighting farther north along the Mississippi and other large rivers, Commodore Farragut was doing valiant work below New Orleans. This city was protected by two strong forts. Just below the forts there stretched from each bank towards the middle a big boom of logs. The space in the middle of the river between the ends of the booms was filled with hulks of old ships, first firmly anchored, then heavily chained to each other, and lashed to the booms with huge cables, making almost a bridge. Above this formidable barrier was a fleet of iron rams and gunboats. Besides all this, there were a number of fire rafts, loaded with cotton and hay, ready to be set in a blaze and float down on any Union craft that would dare to come up. How was it possible for the Union vessels to force their way up the river in the face of these obstructions? [Illustration: ADMIRAL FARRAGUT.]