Thanks, Dawn, I hadn't thought of that .
I forgot to mention that, according to the 1881 census, William was a "sea engineer mariner". He's not living with his family in Stockton in 1899 or 1901 - I'm guessing he was probably at sea.
The actual record lists the names of the ships the deceased were on - except for William. He's the only one on the page with a blank space there.
Jan