All deltas appear by their section to be formed of matter totally different from that of the adjacent country. They are the creation of the rivers themselves, which, having brought down with their floods vast quantities of mud and sand from the upper lands, deposit them in the lowest place, the sea; at whose margin, the current which has hitherto impelled them ceasing, they are deposited by the mere action of gravity. This is particularly illustrated on the western coast of Africa by the shoals off the Rio Grande, Rio Nunez, and others. The coast, as well as the embouchures of the rivers, exhibit a deposit of deep mud, and yet far at sea banks of clean siliceous sand arise. DEMAND. The official paper by which stores are desired for a ship, the making out of which is the duty of the officer in whose charge the stores will be placed: they must be approved by the captain and admiral before being presented to the dockyard authorities. Also, whence from? where bound? DEMI-BASTION. In fortification, a bastion which has a flank on one side only. DEMI-CANNON. An ancient name for a gun carrying a ball of 33 pounds weight, with a length of from 12 to 14 feet, and a diameter of bore of 6-1/2 inches; its point-blank range was estimated at 162 paces, and its random one at 2000. DEMI-CULVERIN. An ancient cannon which threw a ball of 9 pounds weight, was about 9 feet long, and 4 inches in diameter of bore; its point-blank range was called 174 paces, and its random one about 1800. DEMIHAG. A long pistol, much used in the sixteenth century. DEMILANCE. A light horseman, who carried a light lance. DEMILUNE. In fortification, the outwork, more properly called a _ravelin_ (which see). DEMI-REVETMENT. In fortification, that form of retaining wall for the face of a rampart which is only carried up as high as cover exists in front of it, leaving above it the remaining height, in the form of an earthen mound at its natural slope, exposed to, but invulnerable by shot. DEMONSTRATION-SHIPS. Those kept in a certain state of preparation for war, though on a peace establishment. DEMURRAGE. The compensation due to a ship-owner from a freighter for unduly delaying his vessel in port beyond the time specified in the charter-party or bill of lading. It is in fact an extended freight. A ship unjustly detained, as a prize, is entitled to demurrage. Vessels chartered to convey government stores have a term given for discharge by government aid. If not delivered within that period, demurrage, as stated in the document, is paid per diem for any "unavoidable delay." DEN. A sandy tract near the sea, as at Exmouth and other places. DEN AND STROND. A liberty for ships or vessels to run or come ashore. Edward I. granted this privilege to the barons of the Cinque Ports. DE NAUTICO FŒNORE. Of nautical usury; bottomry. DENE. The Anglo-Saxon _dæne_; implying a kind of hollow or ravine through which a rivulet runs, the banks on either side being studded with trees.