Thanks for the Cornell University website. In searching for the name "Ahern" I came upon an unrelated report of the officer commanding CSS Gaines in action off Mobile, AL in August 1864 in which he cites several men for gallantry under fire, including "Paymaster's Clerk Wilson (in charge of the supply of shells to the after division)"

This suggests what paymaster's steward Ahern's duties on the Kearsarge may have been when in action.

-dja