In the use of the balloon the British showed high proficiency and effectiveness throughout the entire campaign. The huge silken bag was attached to a heavy wagon, and was drawn, fully inflated, by a span of thirty or forty oxen. The successful use of this auxiliary was facilitated by the open nature of the country. The information obtained thus was exceedingly valuable to Lord Roberts during his advance towards Pretoria. Not only, however, is it a material advantage to a force to possess this direct method of getting information, it also has a certain moral effect upon the enemy that is in itself powerful. This is somewhat similar to the effect that a heavy artillery fire has upon well-intrenched infantry; the shells are not apt to hurt anybody--indeed, a heavy artillery bombardment of field intrenchments is usually as harmless as a political pyrotechnic display, except for the trying effect on the imagination and nerves of the men who are being fired at. But the Boers were bothered more by the balloon than by ballooning shells. [Illustration: Boer artillerists waiting under shell fire for the British advance.] One day I was lying in the Boer trenches under an exceedingly heavy artillery fire, which the burghers did not mind more than a hailstorm. They were well under cover of the _schanzes_ which they had built along the ridge of the kopje, and they were calmly awaiting the British advance, smoking and chatting in nonchalant fashion, without a trace of nervousness. Suddenly some one spied the balloon as it slowly rose in front of us, and its apparition created a perceptible consternation for some moments. This agitation was not fear, for the Boers knew perfectly well that danger was no more imminent than before; but the thought that the enemy from whom they were concealing themselves could see them as perfectly as though the mountain were not there certainly got on their nerves. The work of the balloon corps was valuable in that it could discover to the artillery the position not only of the fighting line, but also of the reserves and of the horses, and of the line of retreat. The mid-air observer before Pretoria found and pointed out the range of the railway line leading towards Middleburg, by which the retreat was being made, so that the naval guns began to shell the line, hoping to break it by a lucky shot, or to disable a train. As it happened, however, the trajectories did not strike the narrow lines of rails, but they did cause the American Consul, Mr. Hay, some inconvenience, as they filled his consulate full of holes, though he kept on calmly at his work; finally a sympathetic neighbor sent over his compliments and suggested that they have tea together in the lee of his house; everybody else in that vicinity had fled.