(3)Military insanes shall invariably be conveyed in second class carriages. In the case of non-military prisoners it is in the discretion of the Superintendents to despatch them in second class, inter class or third class carriages. In all cases, however, in which it is considered desirable that the escort of such prisoners should consist of police the prisoners will be conveyed in second class carriages."All other prisoners not included in the foregoing categories shall be conveyed in second class carriages.