"Couldn't you make out people walking, or troops marching, and the like?" asked one of the men. "No, indeed," said Alfred. "Why, how big do you suppose a man would look at a distance of five thousand feet, when you are directly overhead?" "I don't know," replied the sergeant, with an inquiring look. "I don't suppose he could be seen at all, unless he happened to be moving." "Why, at that distance it would be impossible to see the man, moving or not, for he would not appear bigger to the eye than the end of the finest wire," Ralph informed him. "I remember when we made our first flights at Bar-le-Duc, that the lieutenant asked us to give him our impression as to the sizes of objects we saw and to tell him what they were. When a fellow is flying about the first thing he will notice is a river, if there is one anywhere in the neighborhood, and, of course, I saw a bridge. I couldn't wait until we landed before I marked it down on a piece of paper: 'A bridge; 200 feet long.' I thought I'd get it long enough. We were then flying about 5,000 feet above the earth. I saw the lieutenant smile. At that height the bridge looked about like a lead pencil held ten feet from the eye. Well, when we landed, the lieutenant said: 'It was a bridge, sure enough, but it happens to be seven hundred feet long.'" "That reminds me," observed Alfred, "that we talked about several other things on that trip, and it will show how poor the judgment is unless the eye is well trained. Do you remember the drill ground east of Fleury? Well, we were asked to put down the number of men we could estimate in each group, and I was particularly anxious to tell the lieutenant how many men were in each of the squares which were formed. Each block of men, as they appeared to me, were about the size of a domino. I felt sure there couldn't be more than 50 men, but the lieutenant said there were at least two hundred." "But that isn't the worst of it," rejoined Ralph. "We knew they were soldiers, because they were on the drill ground, but if that same number of men had been in the open country, it would have taken an expert to see them. I was fooled in that way not long after the experience I was just telling about, and, although the lieutenant pointed out the marching men, I couldn't spot them until he told me to watch for the glint of steel that would occasionally flash out. Then I understood." "I have heard it said that if every moving object, it mattered not how big it might be, were painted the same color as the earth and other surrounding objects, aviators would not be able to discover them; is that really so?" inquired the sergeant.