Hello,
For 3sillydogs : Thank you for your links, but they are about later shippings, circa 1850-1900.
I found on googlebook that the Antelope was used in 1824 to carry settlers from Cape Town to Natal area with another ship (the Julia, I think).
On Lloyds List, it seems that in 1822, the captain was named Cole, but the ship was sold in 1823. Perhaps, Butler became captain of this ship in 1824, but I would like to confimr with some look-up into local newspapers...