On Thu, Oct 14, 2004 at 07:11:59PM +0100, Paul Millar wrote:
If it [the possessing object] does [end with an s], then add just the apostrophe. For example: if Simons owns a ball, which is red, then Simons' ball is red.)
Actually this is generally regarded as archaic, at least in the UK[1] - the form Simons's ball is usually preferred. One exception is with the name Jesus where we would have Jesus' ball.
Huw. [1] See Fowler's Modern English Usage.