ship's bell

Watch-glass Sand-Glass Striking Bells...
​Originally sand-glasses were the timekeepers at sea. Glasses is the maritime word for each of the 8 half-hourly periods of which the watches consist and indicated by bell-strokes. The 24 hours of a day and night are divided into six 4-hourly watches. An hourglass, at sea: half-hourglass, is a timekeeper consisting of two funnel-shaped glass containers with their tops turned towards each other and connected by a narrow opening, through which fine sand runs from one container to the other in half an hour. The moment the glass has run empty, it’s turned upside down and the ship’s bell is struck the appropriate number of times. A ship’s clock sounding bells indicate the time by the number of struck bells = passed half hours from the beginning of the watch. For example, at 12 noon 8 bells striking mean “Watch is over!” a new watch is beginning and shall end 8 bells later at 16 hours. One advantage about a ship’s clock striking bells is that you can tell the time at any whole or even half hour, which is to your advantage, especially if you cannot see the clock.