The _Field Line Commissions_ are the executive agents of the Director of Railways in the discharge of the various duties assigned to him. The number of these Commissions is decided by the Directeur de l'Arrière, and the date of their entering on their functions is fixed by the Director of Railways. Each Commission consists of a staff officer and a railway engineer. Of these the former is military president of the Commission and has the controlling voice. When he considers it necessary that he should accept, in addition to his own responsibility, that of the technical commissioner, the latter must defer to his views and to the orders he gives. The president has an assistant--also a staff officer--who can replace him when necessary, while the Commission has a staff of secretaries and orderlies as approved by the Minister of War. The personnel of the Commissions includes Railway Troops ("Sapeurs de chemins de fer" and "Sections de chemins de fer de campagne"); a telegraphy staff; Station Commissions; and "gendarmerie" to undertake police duties in the stations and on the trains. In addition to making traffic arrangements and undertaking the operation of those lines at the theatre of war that may pass under full military control, the Field Line Commissions are required to carry out such construction, repair, maintenance or destruction work on the railways as should be found necessary. On the _Lines of Communication_ passing through the two zones and ensuring direct communication between the interior and such accessible points on the railway as may, from time to time, be nearest to the armies in the field, the leading stations _en route_ are required to serve a variety of military purposes; though in each and every such instance the system of organisation is such that the duties to be discharged or the responsibilities to be fulfilled are undertaken by, or are under the control of, a Commission formed on the now established basis of representation thereon of both the military and the technical elements. For the conveyance of troops, there are, in the first place, _Mobilisation Stations_ and _Junction Stations_, whence the men within a certain district are sent to the _Embarkation Stations_, at which complete units for the front are made up. These are followed by _Stations for Meals_ ("Stations haltes-repas"), for men and horses; though in this case the "stations" may really be goods or locomotive sheds, able to accommodate a large number of men. At the end of the railway line, so far as it is available for troops, come the _Detraining Stations_.