Quote

Lieutenant James Wilson, from the West Norfolk Militia, to be Adjutant, vice Stevenson, appointed Adjutant to Hilsea Barracks.

— The London Gazette, Saturday 17 January 1801 source

The word “vice” is used here in the sense of “in place of” or “as a replacement for”. Lieutenant James Wilson is being appointed as the new adjutant of the Loyal Tarbert Fencibles, replacing Stevenson, who is moving to a similar position at Hilsea Barracks.