Convict overseers in Tasmania

I am looking for sources of information connected to publications relating to convict overseers in Tasmania around the mid 1800s. My GGGFather, Bernard O'Reilly (1826-1893), arrived in Sydney in 1848, marrying a Mary Ann Vaughan in 1848 in that city. They moved to Tasmania where I believe he was employed as a convict overseer (he was originally a member of the British Army).

The first two issues of the marriage were a Francis Robert O'Reilly (1849-    ), and a Bernard O'Reilly (1851-    ). It MAY have been Bernard the son who was in fact the overseer....I'm not sure how the dates would fit?

Thanking you in anticipation!

Cheers, Pete Lovett