I have read a sentence:
Wake me at nine bells.
When to wake the people?At nine o'clock?
Traditionally, watches at sea—essentially shifts when any one portion of the crew, particularly the lookout (whence the name)—were four hours long. To keep track of the passage of the watch, the ship’s bell was rung every 30 minutes, indicating how many half hours had passed. Thus, for instance, 6:30 is called “five bells” and is rung as “Ding-ding, ding-ding, ding,” indicating that two and a half hours has passed since the start of the 4 o’clock watch. The end of a watch (and therefore the start of the next) is rung as eight bells.
So at nine bells is not something that would be used literally by any mariner. Depending on context, it could be an ironic way of saying never—a bit like the term eleventh frame used in the context of bowling to mean after a game because games consist of ten frames. Or, if no irony is intended, it could merely reflect the speaker’s ignorance of how ships’ bells strike time and be intended to convey the meaning 9:00.
As discussed, this literally doesn't make any sense. The system of bells on board ships only goes to 8 bells.
It is possible that this was inserted as a deliberate piece of irony - with the meaning of "never". Just as you can imagine someone saying, "I'll do it when the clock strikes thirteen." to mean "I'll never do it." I consider this unlikely, as it is too obscure for the intended readers of this book (young children). Though it might be an "Easter egg", a hidden joke for any sailors reading the book with their children.
It is possible that this ship is using some non-standard system of bells. There are systems with five-hour watches, which would go to 10 bells. Again I consider this unlikely. It is simply a random detail that is to obscure to appear in a book which has a specific purpose of "teaching young children to use a full stop".
It is possible that this is simply a mistake by the author. The author may be aware (from reading Treasure Island) that sailors use expressions like "At three bells". They neither know nor care what the actual meaning of this would be, and has incorrectly assumed that this means "at three o'clock". I consider this to be most likely. The author intends the meaning "Wake me at nine o'clock" (which a child would understand to mean "waking up later than normal" and has incorrectly assumed that this is what "at nine bells" means.
The system of ship's bells is something that the young children who read this book, and 99% of adults know nothing about, except as a nautical expression; something sailor say, like "Heave ho" or "three sheets to the wind"
Before marine mechanical clocks were available, time was tracked with an hourglass. Actually, a half-hour sand-glass. The day started at local noon, determined by the maximum elevation of the sun above the horizon. This was determined with a sextant during the noon navigational fix. When the senior navigator (usually the ship's Master) determined it was "high noon", he would announce "make it noon" and the hourglass would be flipped, starting the day
Each half hour the glass would be flipped and the bell rung, between 1 and 8 times to count off the half-hours. Crew shifts, or "watches" were 4 hours long so after "8 bells", the watch would change and a half hour later the bell would ring once. The bell would never ring 9 times.
Each time the bell sounded, the ship's magnetic heading and speed would be recorded on a slate for later calculation of the dead-reckoned position. Speed would be determined by heaving overboard a "log" on a string. The string fed out for a standard length of time measured with a different sand glass, about 30 seconds. The length of string was measured and converted to speed. The string was knotted at standard intervals, so the sailors could just count knots as they slipped by. Speed was then recorded on the slate as so many "knots" which corresponded to nautical miles per hour.
To this day, mariners still refer to their speedometer as a "log" and refer to speed in knots. Any written or electronic navigation record is still a "log".
For centuries, the Royal Navy would "press gang" (kidnap) citizens to serve in the navy. If the men survived the service, they would return to civilian life with a vocabulary enriched with nautical terms.
Many English expressions have origins in naval terms: