For some time past, the Society has been shipping ambulance cars, and also touring cars, to the Continent as rapidly as means of transit have permitted. The requirement seems to be enormous, but even so there does not appear to be any likelihood of the supply falling short of it. Many motorists have placed not only their cars, but their own services ungrudgingly at the disposal of the Society. The usual practice is for the Society, after accepting a car for service, to undertake to have a suitable ambulance body put upon it in place of its own. In some cases, however, motorists have even taken this charge upon themselves, and whatever may be the disadvantages of dependence upon volunteer service, it can at least be said that in this case such dependence has served in some measure to show how many men, unable for one reason or another to take up military duties, are only too anxious to expend their energies and their money on any object of national value in connection with which they are able to be of use. CHAPTER VI THE TRANSPORT OF AMMUNITION AND ARTILLERY The System of Ammunition Supply--The Traction Engine--French Four-Wheeled Tractors for Hauling Guns--German Gun-Carrying Motors. The system of maintaining ammunition supplies for troops in the field is very similar to that already described in connection with the supply of food. Stocks of ammunition are kept at depôts of the Army Ordnance Corps at various points between the base and railhead, to which they are forwarded as required. From railhead they are brought forward daily by the motor lorries of the divisional ammunition parks to a convenient re-filling point, where they are transhipped on to horsed ammunition carts for distribution in detail. With the troops entirely dependent on the motor vehicle for the maintenance of their supplies both of food and of ammunition, there is no need to labour the enormous importance of mechanical transport in modern warfare, or the terrible consequences which would follow anything approaching a general failure in the reliability of the machines used. For the haulage of very heavy guns some form of engine power is of course essential, and the ordinary steam traction engine provides the most obvious solution, since it is to be assumed that if the roads and bridges to be traversed are sufficiently strong to bear the gun itself, they will also bear the engines which haul it. The big traction engine is a very British product, and it is interesting, if not quite satisfactory, to note that the huge siege guns of the German army are stated to be hauled by engines of British origin. For lighter guns, the steam tractor, or small traction engine, can be employed, but very many efforts have been made to dispense with its service in favour of an internal combustion tractor, less dependent on constant renewal of fuel and water supplies. [Illustration: A BRITISH “MARSHALL” INTERNAL COMBUSTION TRACTOR SUITABLE FOR THE HAULAGE OF ARTILLERY.]