Sentence:  ...on the motion of Sir John Marjoribanks, Bart., Lord Provost, unanimously resolved, July 27, 1814, “that there be annually presented by the town of Edinburgh to the boy at the head of the Greek class, taught by the rector of the High School, a gold medal of the same value [five guineas] as that annually presented to the <WSD>dux</WSD> of the Latin class.” 
Meaning of the word marked with <WSD> tags:  The top academic student in a school, or in a year of school; the top student in a specified academic discipline.