Re Hiram Henry Slocum William Wanton Slocum G'day Randy,
I just found your posting after doing a search for William Wanton Slocum (b 1875 Graytown, Victoria, Australia). He was a son of Hiram Henry Slocum b 1829 (who you list), and Jane Sarah Bell. The William Wanton Slocum listed (b 1824, and who appears as a brother of Hiram Henry), wasn't the one I was looking for and, not surprisingly, wasn't the only William Wanton Slocum. Hiram Henry Slocum is a 2nd great grandfather.
I know that William Wanton Slocum (b 1875 in Graytown), went to the U.S.A. to live, became naturalized and ended up in Detroit. He and his wife (Lillian nee Bittman) and son (William W.) appear in the 1941 Census. I have been trying to find some of their descendants.
I know there was also a daughter of William and Lillian: Catherine J Slocum, b 1910. Older relatives back in Australia, told me that she travelled to S.E. Asia (Rangoon, Burma)? She was probably caught up in the Japanese invasion at the time that war was declared on Japan in 1941. This could explain why she doesn't appear at home in the 1941 Census. Of course there may be other reasons (e.g. married name etc.); although at the moment all I have to go on is what I have been told by other family members. There are still people in Australia who wonder what happened to her and whether she ever got out and back home.
Let me know if you can add to this or if I can help with anything regarding the Slocums in Australia.