Sentence:  Behind the Counter stood a complaisant Spark, who I observ'd shew'd as much Breeding in the sale of a Penny-worth of Tobacco, and the change of a Shilling, as a "Courtier's Footman" when he meets his Brother <WSD>"Skip</WSD>" in the middle of "Covent-Garden"; and is so very dexterous in discharge of his Occupation, the he guesses from a Pound of Tobacco to an Ounce to the certainty of one Corn ... 
Meaning of the word marked with <WSD> tags:  A college servant.