We shall see later how motor-cars are used for the supply of food or ammunition. Many more cars are needed for the hospitals, ambulances, and the carrying of the wounded. The consumption of gasoline, notwithstanding the suppression of the abuses which were for a long time prevalent on the Anglo-French Front, remains considerable. France is supplied with it exclusively by the United States and Mexico. =5. General remarks on transportation.= The question of supplies of all sorts will be one of the difficulties connected with the organization of the American Armies on French soil. The United States will not merely have to convey troops from one continent to the other, but also to ship all that is necessary for the subsistence of her armies, their upkeep, their armament, their artillery, etc., just as if they were expected to land in a desert country where the barest necessaries of life would be lacking. The American Government and the General-in-Chief have from the start been aware of the difficulties awaiting them, and, immediately after the landing of the first troops, very important works were begun for the improvement of the French ports of landing and for the duplication of French railroads, wherever needed. This work is being actively carried out under the direction of American engineers. =6. Camouflage.= Everything pertaining to the equipment and employment of troops must be hidden, so far as possible, from the sight of enemy aviators, and the various devices resorted to for this purpose are termed “Camouflage” (disguise). Artillery, transportation parks, ammunition dumps, camps, roads of communication, etc., are masked in many ways, on the general principle of causing the object to be concealed to blend with the tint of the soil or the foliage, or to melt into the landscape and avoid the eye. Coverings of brushwood or straw represent the simpler, and framework supporting artificial greenery or painted canvas, the more ambitious forms of camouflage. Objects irregularly blotched with paint of different colours are practically invisible at a certain distance--a device borrowed from the “protective colouring” of the animal kingdom. Batteries of dummy guns are often used in this, as in former wars, to deceive the enemy. It is highly important to have good points of observation within the first lines, whence the enemy’s defences may be searched with powerful field-glasses. To meet this need, artificial trees, rocks, etc., have been provided when nature failed to supply them. The camouflage of the French army has been entrusted to a special corps of professional artists, which has proved a most useful unit, since it is necessary that the work done should deceive not only the human eye, but the sensitive plate of the camera. CHAPTER IV COMPOSITION AND USE OF THE ARTILLERY 1. Retrospective view. General considerations.