Section 4. And be it further enacted by the authority aforesaid, That in all cases where separate views and reports of the roads supposed to be on the dividing lines of counties have been made under the authority of the respective courts of quarter sessions of the adjoining counties, and the said reports do not agree as to the line, then and in such cases, on petition of the supervisors of the highways or inhabitants of the said counties to the justices of the court of quarter sessions of each county, it shall be the duty of the said justices, and they are hereby empowered and required to appoint viewers, and proceed in that same manner as is directed by the second section of this act; and when so confirmed shall be considered as on the county line, and be kept in repair at the joint expense of the adjoining township; Provided always That the viewers in such cases shall have power to vacate any part of the old road for which the new road is to be a substitute.