Sentence:  The Celebrity, by arts unknown, induced Mrs. Judge Short and two other ladies to call at Mohair on an afternoon when Mr. Cooke was trying a <WSD>trotter</WSD> on the track. The three returned wondering and charmed with Mrs. Cooke; they were sure she had had no hand in the furnishing of that atrocious house. 
Meaning of the word marked with <WSD> tags:  In harness racing, a horse with a gait in which the front and back legs on opposite sides take a step together alternating with the other set of opposite legs; as opposed to a pacer.