There is a difference between walking and strolling. Ask Howard Zar, who presides over Lyndhurst Mansion, the 67-acre Gothic Revival estate of the late railroad tycoon Jay Gould. Simply writ, walking is how you get from one place to another. However, strolling is what you did on a summer’s day in the 19th century, wearing your best frock, all gussied up, posing with a certain air and cadence, gliding with perfect aplomb around the grounds of the estate overlooking the Hudson River. Zar has recreated this leisurely ritual by rebuilding the winding concrete paths that started at the veranda and curved in and out of the greenery to the Hudson River.