The captain reached over to the table and took up the sketch. "It's a simple little thing to have caused such a lot of worry, isn't it!" he said musingly. "It looks as harmless and innocent as any butterfly might seem, fluttering about on a May morning. Yet, it is in reality a very deadly little article, Patricia. I'm only thankful to goodness that its deadliness was so well hidden that those Huns never caught on to it. Its particular usefulness is practically over now, since the work I've been doing is all but complete. But it would have been a terribly dangerous thing had it fallen into the hands of the enemy and they had fathomed its meaning. My work would then have been almost valueless.
"And since you have done so much to aid in keeping this a secret, Patricia, I think the time has come to tell you the meaning of it all. You have earned the right, and all I ask is that you will communicate it to no one till I give you permission. I can trust you, I know.
"I have already told you how, when I was a prisoner in Germany, it occurred to me that if I pretended to have lost some of my wits, through shell-shock, as many have, the ruse might benefit me in a number of ways. I was strong and able-bodied at the time, and the Huns were particularly in need of husky prisoners to do their work, and they much prefer those who show symptoms of not having all their wits about them. I was unusually successful in the device, and was finally set to work in an outer section of one of their airplane factories—of course, under strict guard.
"It was here that I came in contact with a German mechanic, a man of somewhat finer caliber than most of them, to whom I was able to render a rather important service or two. He was ill and in want, and he had a serious grievance against his government. He had invented a certain device of immense importance, and he was trying to get them to accept it and pay him enough to assure him a decent living. The government wanted the device badly enough, but was so foolish as to haggle and bargain with him over the price, offering him scarcely enough to keep him for six months. He was too ill to work and earn a living, but he steadily refused to give up his secret till properly reimbursed.
"At length it came to the point where he knew he had but a little longer to live. Angered, perhaps, that his Fatherland should have been so ungrateful and mean-spirited, and hating to have his discovery, of which he was justly proud, lost to the world, he confided it to me, for I had, some time before, allowed him to know that I was not the stupid creature I seemed. I asked him whether he cared if America made use of it, and he replied: 'I care for nothing now. The Fatherland has proved unworthy. Do with it what you will.'
"Later, as you know, I myself managed to escape and get through to the French lines. And so I arrived home. But, being of a somewhat mechanical turn myself, I came to realize that this device, still incomplete as it was, could be perfected into an instrument of the greatest importance to the aviation arm of the service. I cannot explain to you exactly what it is, nor go into all its workings. It would be much too technical for you to understand.
"But I can tell you this much about it. An aviator in a bombing-plane has had one great, and, till now, almost insuperable difficulty to contend with. The velocity of his machine is such that a released bomb will have for an appreciable time after it is dropped the same horizontal velocity. This means, in simpler language, that the bomb will be carried along for a time in the same direction and at almost the same rate at which the machine is going. Thus, you see that the aviator, if he is intending to drop his bomb on a certain building or object, cannot do so when he is directly over that object, but must calculate in some way at what point to release his bomb before he comes directly over the object, or it will not hit its mark.
"There have been many attempts to overcome this difficulty, but none very successful. The device I have perfected comes more nearly to accuracy than anything yet discovered, and our own Government is only too glad to make use of it.
"And now we come to The Crimson Patch. When the German mechanic gave me his secret, he also furnished me with a drawing or diagram of the instrument. This was absolutely necessary to have, as the invention was so complicated that I could not possibly have carried it in my head. But I realized, also, that it would be extremely dangerous to carry it around with me in the shape in which it was. So I camouflaged the whole thing in a sketch of the Crimson Patch butterfly, and in this form it was safe enough, for I had made a point of sketching at times the various butterflies I had seen while in the prison-camp, and the Germans thought me only a harmless lunatic on the subject. The Crimson Patch was no more to them than any other pretty little sketch I had made."
"But, Daddy," cried Patricia, staring at the paper in his hand, "I can't see a trace of anything like the drawing of a mechanical instrument."