THE man behind the gun risks his life on his faith in the ammunition train to keep him supplied with powder and shell. An old warrior estimates that an army of 60,000 men, comprising a fair average of infantry, cavalry, artillery and engineers must be provided with no less than 18,000,000 ball cartridges for small arms, rifles, muskets, carbines and pistols for six months' operation. In the field an infantry soldier usually carries about sixty rounds. The lives of the men depend upon the promptness of the ammunition trains. To supply these 60,000 men requires one thousand ammunition wagons and 3,600 horses. The wagon constructed for this service will carry 20,000 rounds of small-arm munition. The cartridges are packed in boxes and the wagon is generally drawn by four to six horses or mules. Several wagons are organized into an "equipment," moving under the charge of an artillery, and there are several such "equipments" for an army of this magnitude, one for each division of infantry, a small portion for the cavalry, and the rest in reserve. Early in the Civil War a chemist suggested to General McClellan that he could throw shells from a mortar that would discharge streams of fire "most fearfully in all directions." McClellan replied: "Such means of destruction are hardly within the category of civilized warfare. I could not recommend their employment until we have exhausted the ordinary means of warfare." The Government preferred to depend largely upon these silent, ghost-like wagons, with their deadly loads of millions of cartridges, pressing toward the battle lines throughout the conflict. This picture shows an ammunition train of the Third Division Cavalry Corps in motion with the army encamped on the distant hills. It is one of Brady's best negatives. [Illustration: PHOTOGRAPH TAKEN AS AMMUNITION TRAINS WERE MOVING]