The plaintiff was using the highway by travelling thereon for a lawful purpose.

He was not a servant or agent of the city in any such sense *418as to take away his right of action for the injury sustained by him. He was a public officer, appointed to discharge important duties, in which the city had no special interest, and from which they derived no particular advantage. Buttrick v. City of Lowell, ante, 172. Exceptions overruled.