Bells and watches are the shipboard way of managing time and labour.
Since a ship was manned at all times while at sea, the crew was divided into two groups, the port and starboard watches, one of which was 'on deck', or on duty, at any one time. The ship's surgeon, cook, carpenter, etc. were known as idlers as they did not stand watch since they were considered on duty at all times. Watchstanders were Lieutenants as Officer of the Deck, Midshipman of the watch, and the other hands to assist trimming the sails, steering the ship (manning the helm), and gunners which would assist the other hands with the sails. While one watch was 'on deck', the other was either doing chores during the day such as polishing the deck with their 'holystones', making repairs and upkeep of the ship's equipment and so forth, or doing whatever they like in the evening or sleeping. Anytime a major change was needed to the sails, all hands were called. The idler's would also assist at this time.
So, the port and starboard watches as they were called, took turns on deck for handling the ship. The time they were on deck is referred to as a watch, usually a four hour period of time. So, from midnight to 0400 hours, the port watch may be on deck on a given day, and the starboard watch is 'below' or off watch. at 0400 they switch; the starboard watch is on deck whilst the port watch is below. So that the same watch (group of hands) are not stuck with the same watches every day, the time from 1600 (4 pm) to 2000 (8pm) is divided into two 'dog' watches, of two hours each. That way whomever had the mid-watch on one night would be sleeping during the same night the next.
So, watches (shifts) went like this, let's say, the port watch on deck for the mid-watch on a given day, one can see that the starboard watch would be on deck for mid-watch the next day.
- 0000-0400, mid-watch, port watch on deck, starboard watch sleeping
- 0400-0800, morning watch, starboard watch on deck, port watch begins to holystone the deck, morning meal
- 0800-1200, forenoon watch, port watch on deck, starboard watch morning meal, begins ship upkeep, noon meal
- 1200-1600, afternoon watch, starboard watch on deck, port watch, noon meal, continues ship upkeep
- 1600-1800, first dog watch, port watch on deck, starboard watch evening meal
- 1800-2000, second dog watch, starboard watch on deck, port watch evening meal
- 2000-2400, first watch or evening watch, port watch on deck, starboard watch idle or sleeping
Since the only timepieces on board ship at that time was the ship's chronometer and whatever watches the officers had, how did they tell time on board ship?
The ship's chronometer usually kept time according to a standard such as the time at zero degrees longitude (today at Greenwich, England). The Captain, the Master, or the Officer of the Deck would declare the instant of noon according the sighting of his sextant, if the sun if visible. The altitude of the sun was compared to an ephemeris (a table of altitude of the sun each day of the year) and calculate the ship's latitude. A sand hourglass, or, 'the glass' was turned and the ship's bell was rung eight times in pairs ('ding-ding ding-ding ding-ding ding-ding'). This was the beginning of the afternoon watch. The master could then compare local noon with the chronometer and calculate the ship's longitude. Midshipman were usually engaged in the same exercise to learn the calculations.
The glass was turned each half-hour until the next day when it was re-calibrated by the sun. When the glass was turned, the ship's bell was struck to note the time of day. This was done each half-hour around the clock. the bell was struck in pairs, any odd note at the end. So, the day went like this:
- 0030, 0430, 0830, 1230, 1630, 2030, ding
- 0100, 0500, 0900, 1300, 1700, 2100, ding-ding
- 0130, 0530, 0930, 1330, 1730, 2130, ding-ding ding
- 0200, 0600, 1000, 1400, 1800, 2200, ding-ding ding-ding
- 0230,0630, 1030, 1430, 1830, 2230, ding-ding ding-ding ding
- 0300,0700, 1100, 1500, 1900, 2300, ding-ding ding-ding ding-ding
- 0330,0730, 1130, 1530, 1930, 2330, ding-ding ding-ding ding-ding ding
- 0400, 0800, 1200, 1600, 2000, 2400, ding-ding ding-ding ding-ding ding-ding