In the Schneider, the drive is taken from a gear box containing two sets of sliding gears through cardan shafts to the front and back axles, and alternatively, when required, to a capstan enabling the engine to haul through the medium of a wire rope. In the Chatillon-Panhard, the transmission is so arranged as to involve no universal joints, and only one differential gear. This is mounted on a transverse countershaft, and the power is taken to the wheels through bevel gears at the ends of the countershaft, and four diagonal shafts driving in their turn auxiliary shafts upon which are bevels engaging with similar bevels on the wheels. The Renault is a very simple machine of its type. The drive is taken fore and aft from the gear box by cardan shafts leading to differential gears on the front and back axle. Either one of the differentials can be locked when desired to help the machine to find its way out of difficult positions. Yet another machine which is available to the French Government, though it did not take part in the trials mentioned, employs electrical machinery in place of the usual mechanical transmission gear. The engine drives an electric dynamo, which supplies current to four electric motors, one for each wheel. On the whole, the French four-wheel driven tractors have performed very well under severe tests, and it is stated that approximately 300 tractors of one or other of the types mentioned are available for military service, though it is possible that this estimate is somewhat exaggerated. [Illustration: _“The Autocar” illustration._ A KRUPP MOTOR GUN-CARRYING LORRY, SHOWING THE RAMPS UP WHICH THE GUN HAS BEEN HAULED SERVING ALSO THE PURPOSE OF HOLDING IT SECURELY IN POSITION.] For the rapid transport of light artillery various special machines have been devised, providing either for the carriage of a gun upon the platform of a motor lorry, or for the construction of a gun-carrying vehicle forming one complete unit. In this branch of development the Germans have shown the most initiative, and Krupps have got out several interesting designs. In all of these strong motor lorry chassis are used. A usual system is to fit, by hinging to the back of the chassis, strong ramps up which the gun may be hauled, either by the power of the motor engine or by other means. When on the platform, the gun wheels sink into depressions formed to take them and also bear up against shaped vertical stops. When the gun is in place the ramps are swung over, and are so designed that their ends can then be conveniently attached rigidly to the vertical stops, the ramps themselves also bearing against the gun wheels and holding them quite secure; or in an alternative method, the ramps are arranged to grip the axle of the gun carriage.