Deck Watches and Ship’s Bells

My Dad and I were having a discussion the other day about the traditional sequence of deck watches on a ship. Ideally, the ship’s crew splits into three or four groups and they take turns at keeping watch (running the ship). If a crew is short-handed then they may only split into two groups. The deck watches are traditionally four hours long, with 2 two hour watches in the early evening which force a rotation of the watch so that a single group do not keep the same watches on consecutive days. The sequence of watches is as follows:

First watch20:00 to Midnight
Middle watchMidnight to 04:00
Morning watch04:00 to 08:00
Forenoon watch08:00 to Midday
Afternoon watchMidday to 16:00
First dog watch16:00 to 18:00
Last dog watch18:00 to 20:00

Each watch is split into thirty minute segments with the ship’s bell being rung at the end of each half hour. Each ding of the bell represents the number of half hours that have elapsed during the current watch, up to a maximum of eight. Eight bells (dings) represent the end of the watch, and therefore the start of the new watch.

It is standard practice to group the dings into pairs with a slight pause between each pair. So, 4 bells (which is two hours into the current watch) would be rung as “ding-ding, pause, ding-ding”. This makes it easier to calculate the progression of the watch: counting the groups tells you how many whole hours have elapsed, and then if the last group is only one ding you know that the current hour is only half way through.

The last dog watch can be rung in two different ways: either as 5,6,7 and 8 bells; or as 1,2,3 and 4 bells. Traditionally it is rung as a continuation of the first dog watch; that is, the first half hour into the last dog watch (18:30) is 5 bells. However, the British Navy changed this in 1797 after a mutiny amongst the naval ships anchored in the Nore anchorage on the Thames estuary. The mutineers used the sounding of the 5 bells of the last dog watch to signal the start of the mutiny. After this, the British Admiralty decided that the last dog watch would be sounded using 1,2,3 and 4 bells; that is, 18:30 is 1 bell.