Sorry, unfortunately, as far as I've gone, there aren't any records of who William Henry Arnall's wife was. I keep looking under various rocks and stones, but it's as if she didn't exist.
I recently posted another message on the Genealogy.com Arnall message forum with a summary of all I've found on this branch. I think it is mostly a repeat of what I've posted on this forum, but I think I may have tossed in a few extra details. The message is in reply to someone's request of information on a Jonathan Gholston Arnall, who I believe he had confused with John Gholston Arnall.
Are you also descended from John Gholston Arnall? I've wondered if William H. Arnall had any other children, but all the descendants I've ever run across were through John Gholston Arnall.
My line is:
William H. Arnall
John Gholston Arnall
Joshua Fleming Arnall
Luther Edwards Arnall
Carolyn Arnall, my grandmother