A naval tradition is a tradition that is, or has been, observed in one or more navies. A basic tradition is that all ships commissioned in a navy are referred to as ships rather than vessels, with the exception of submarines, which are known as boats. The prefix on a ship's name indicates that it is a commissioned ship. For example, USS is an acronym which expands to United States Ship; in the Royal Navy, HMS expands to His Majesty's Ship (or when a Queen reigns, Her Majesty's Ship); in the Indian Navy, INS expands to Indian Navy Ship, and so forth. An important tradition on board British naval vessels (and later those of the U.S. and other nations) has been the ship's bell. This was historically used to mark the passage of time on board a vessel, including the duration of four-hour watches. They were also employed as warning devices in heavy fog, and for alarms and ceremonies. The bell was originally kept polished first by the ship's cook, then later by a person belonging to that division of the ship's personnel. Another important tradition is that of Piping someone aboard the ship. This was originally used to give orders on warships when shouted orders could not have been heard. The piping was done by the ship's boatswain and therefore the instrument is known as the boatswain's Pipe or boatswain's call. The two tones it gives and the number of blasts given off, signify the order given. It is also used in a ceremonial way, i.e., to "pipe" someone aboard the ship — usually captains, including the ship's captain, and more senior officers. By English tradition, ships have been referred to as a "she". However, it was long considered bad luck to permit women to sail on board naval vessels. To do so would invite a terrible storm that would wreck the ship. The only women that were welcomed on board were figureheads mounted on the prow of the ship. In spite of these views, some women did serve on board naval vessels, usually as wives of crewmembers. The custom of firing cannon salutes originated in the British Royal Navy. When a cannon is fired, it partially disarms the ship, so firing a cannon for no combat reason showed respect and trust. The British, as the dominant naval power, compelled the ships of weaker nations to make the first