  a ship's bell is used to indicate the time aboard a ship and hence to regulate the sailors' duty watches. the bell itself is usually made of brass or bronze and normally has the ship's name engraved or cast on it. ==timing of duty periods== unlike civil clock bells, the strikes of the bell do not accord to the number of the hour. instead, there are eight bells, one for each half-hour of a four-hour watch. in the age of sailing, watches were timed with a 30-minute hourglass. bells would be struck every time the glass was turned, and in a pattern of pairs for easier counting, with any odd bells at the end of the sequence. the classical system was:  {| class="wikitable" |- ! number of bells ! bell pattern !valign=bottom|middlewatch !valign=bottom|morningwatch !valign=bottom|forenoonwatch !valign=bottom|afternoonwatch !valign=bottom|firstdogwatch !valign=bottom|lastdogwatch !valign=bottom|firstwatch |- |one bell |align="left"|1 |align="right"|0:30 |align="right"|4:30 |align="right"|8:30 |align="right"|12:30 |align="right"|16:30 |align="right"|18:30â  |align="right"|20:30 |- |two bells |align="left"|2 |align="right"|1:00 |align="right"|5:00 |align="right"|9:00 |align="right"|13:00 |align="right"|17:00 |align="right"|19:00â  |align="right"|21:00 |- |three bells |align="left"|2 1 |align="right"|1:30 |align="right"|5:30 |align="right"|9:30 |align="right"|13:30 |align="right"|17:30 |align="right"|19:30â  |align="right"|21:30 |- |four bells |align="left"|2 2 |align="right"|2:00 |align="right"|6:00 |align="right"|10:00 |align="right"|14:00 |align="right"|18:00 | |align="right"|22:00 |- |five bells |align="left"|2 2 1 |align="right"|2:30 |align="right"|6:30 |align="right"|10:30 |align="right"|14:30 | |align="right"|18:30 |align="right"|22:30 |- |six bells |align="left"|2 2 2 |align="right"|3:00 |align="right"|7:00 |align="right"|11:00 |align="right"|15:00 | |align="right"|19:00 |align="right"|23:00 |- |seven bells |align="left"|2 2 2 1 |align="right"|3:30 |align="right"|7:30 |align="right"|11:30 |align="right"|15:30 | |align="right"|19:30 |align="right"|23:30 |- |eight bells |align="left"|2 2 2 2 |align="right"|4:00 |align="right"
Bells_(instrument) Nautical_terms Navies Percussion_instruments Time_measurement_systems Time_signals