<P> Unlike civil clock bells, the strikes of a ship's 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 . </P> <P> The classical, or traditional, system was: </P> <Table> <Tr> <Th> Number of bells </Th> <Th> Bell pattern </Th> <Th_colspan="7"> Watch </Th> </Tr> <Tr> <Th> Middle </Th> <Th> Morning </Th> <Th> Fore - noon </Th> <Th> After - noon </Th> <Th_colspan="2"> Dog </Th> <Th> First </Th> </Tr> <Tr> <Th> First </Th> <Th> Last </Th> </Tr> <Tr> <Td> One bell </Td> <Td> </Td> <Td> 0: 30 </Td> <Td> 4: 30 </Td> <Td> 8: 30 </Td> <Td> 12: 30 </Td> <Td> 16: 30 </Td> <Td> 18: 30 </Td> <Td> 20: 30 </Td> </Tr> <Tr> <Td> Two bells </Td> <Td> </Td> <Td> 1: 00 </Td> <Td> 5: 00 </Td> <Td> 9: 00 </Td> <Td> 13: 00 </Td> <Td> 17: 00 </Td> <Td> 19: 00 </Td> <Td> 21: 00 </Td> </Tr> <Tr> <Td> Three bells </Td> <Td> 2 1 </Td> <Td> 1: 30 </Td> <Td> 5: 30 </Td> <Td> 9: 30 </Td> <Td> 13: 30 </Td> <Td> 17: 30 </Td> <Td> 19: 30 </Td> <Td> 21: 30 </Td> </Tr> <Tr> <Td> Four bells </Td> <Td> 2 2 </Td> <Td> 2: 00 </Td> <Td> 6: 00 </Td> <Td> 10: 00 </Td> <Td> 14: 00 </Td> <Td> 18: 00 </Td> <Td> </Td> <Td> 22: 00 </Td> </Tr> <Tr> <Td> Five bells </Td> <Td> 2 2 1 </Td> <Td> 2: 30 </Td> <Td> 6: 30 </Td> <Td> 10: 30 </Td> <Td> 14: 30 </Td> <Td> </Td> <Td> 18: 30 </Td> <Td> 22: 30 </Td> </Tr> <Tr> <Td> Six bells </Td> <Td> 2 2 2 </Td> <Td> 3: 00 </Td> <Td> 7: 00 </Td> <Td> 11: 00 </Td> <Td> 15: 00 </Td> <Td> </Td> <Td> 19: 00 </Td> <Td> 23: 00 </Td> </Tr> <Tr> <Td> Seven bells </Td> <Td> 2 2 2 1 </Td> <Td> 3: 30 </Td> <Td> 7: 30 </Td> <Td> 11: 30 </Td> <Td> 15: 30 </Td> <Td> </Td> <Td> 19: 30 </Td> <Td> 23: 30 </Td> </Tr> <Tr> <Td> Eight bells </Td> <Td> 2 2 2 2 </Td> <Td> 4: 00 </Td> <Td> 8: 00 </Td> <Td> 12: 00 </Td> <Td> 16: 00 </Td> <Td> </Td> <Td> 20: 00 </Td> <Td> 0: 00 </Td> </Tr> </Table> <Tr> <Th> Number of bells </Th> <Th> Bell pattern </Th> <Th_colspan="7"> Watch </Th> </Tr>

Where does the saying 7 bells come from