In chapter 11 we learn a little more about Mr.Arrow and what might have happened to him. Explain.

It's chapter 10 when we hear that Mr. Arrow is a drunken sod. He was pretty much useless as the first mate. He is presumed drowned having fallen overboard in a drunken stupor. Later Jim overhears Silver talking to Dick Johnson and Israel Hands. Jim figures out that it was probably the pirates who kept Mr. Arrow supplied with rum from their own stash of booze, leading to his mysterious death.