The border continued to the northern slope of Beth-hoglah and came out at the northern bay of the Salt Sea, at the mouth of the Jordan. This was the southern border.
Jewish Publication Society of America Version (JPS1917) - Joshua 18:19 >And the border passed along to the side of Beth-hoglah northward; and the goings out of the border were at the north bay of the Salt Sea, at the south end of the Jordan; this was the south border.