"What would happen then?" asked Bill, deeply interested.
"Well, if the aeroplane is correctly balanced with the tail a little higher than the nose it will be ready for a glide if the engine goes dead, and on the other hand it is apt to lose headway, and go down tail first. And that, you know," added Ernest, laughing, "is often very uncomfortable for the occupants of the car."
"I should say so!" agreed Bill.
"Chaps make such a mistake trying to build their own cars," said Ernest. "More accidents come from that than people realize. While the war was going on, no one had time to tinker at building, but now half the chaps I know are studying up and attempting to make aeroplanes for themselves.
"It just can't be done. For instance, every piece of wood used in a machine must be tested with the greatest care. A chap can't do that himself. Every piece of wire used has got to be stretched in a machine specially invented for the purpose. For instance, to find the breaking strain of a piece of wire, a piece fifteen inches long is placed between the jaws of a standard testing machine, so that a length of ten inches of the wire is clear between the two ends. What they call the 'load' is then put on by means of a handle at the rate of speed of about one inch a minute. You can't do this yourself, and by the time you have sent your wire, or have taken it where the test can be applied, and have also had the test made on the twist of your wire, and all the woodwork, you will have a machine that will cost more than one made by skilled workmen. There is another test too that is very necessary. That is for your wing fabric. It ought all to be soaked in salt water. If the fabric has been varnished, the salt will soften it. Then dry the sample in the sun and if it neither stretches nor shrinks, you will know that it is all right, and you will feel safe about using it."
"I took in all I could learn, without actually going up, at the Aviation field at Sill," said Bill. "I will get my chance some day. I wrote mother this morning, telling her about our trip and all, and I asked her if she thought she would sometime feel like letting me fly. I didn't ask her to let me, you know, but I have a hunch that something might happen sometime and I might almost have to fly. So I told her just how I felt about it. Whatever she says goes."
"That's a good sport!" said Ernest, smiling. "It seems to me that I would be willing to give up anything in the world if I could have my mother alive to make sacrifices for. Of course I have dad, and he is a corking pal and just an all-round dear, but a chap's mother is different, somehow. I think you were wise to write that letter, for you never know what might come up. If your mother is what I should think she is, she will understand that you are not trying to fix a loophole for yourself or tying a string to your word of honor."
"No, she won't think that," said Bill positively. "Mother and I understand each other. I can trust her and she knows she can trust me. It makes things nice all around. She will be crazy about this machine of yours. Perhaps she will take a little glide with you, if she doesn't feel like actually going up. She has promised to come on and spend the Thanksgiving vacation with me."
"Good work! That makes me feel glad that I can't go home. I am going to stay right through the whole year and put in some extra work during the vacations."
"Mom will like you too," said Bill. "She will want to know all about the plane, and when she gets through listening she will know 'most as much as you do. There is one thing I am afraid of, if I should fly, and that is spinning. Now if you begin to side-slip, either outward or inward, you are apt to commence to spin, and—well, there is usually a speedy and more or less painless end to you and your hopes."