It was the original of one of those pictures we sometimes see now with a smile, murmuring, "How quaint!" A huge round boiler, standing high in the back, supplied fully half its bulk. Ford made a hasty calculation of the probable weight of water it carried, in proportion to its power. The result appalled him. He thoughtfully watched the engine until it was out of sight. Then he resumed his way home. On the train he sat in deep thought, now and then figuring a little on the back of an old envelope. "I couldn't get that steam engine out of my mind," he says. "What an awful waste of power! The weight of the water in that boiler bothered me for weeks." CHAPTER X "WHY NOT USE GASOLINE?" One sympathizes with young Mrs. Ford during the weeks that followed. In two years of marriage she had learned to understand her husband's interests and moods fairly well; she had adjusted herself with fewer domestic discords than usual to the simple demands of his good-humored, methodical temperament. She had begun to settle into a pleasant, accustomed routine of managing her house and poultry yard, preparing the meals, washing the dishes, spending the evenings sewing, while Henry read his mechanics' journals on the other side of the lamp. Now everything changed. Henry had returned from that trip to Detroit with something on his mind. In reply to her anxious inquiries he told her not to bother, he was all right--a statement that had the usual effect of confirming her fears. She was sure something terrible had occurred, some overwhelming business catastrophe--and Henry was keeping it from her. From the kitchen window she saw him sitting idly on the horse-block in the middle of the forenoon, twisting a straw in his fingers and frowning intently at the side of the barn. Sometimes after supper, instead of settling quietly down with his papers, he walked up and down, up and down, the sitting-room, with his hands behind his back and that same frown on his forehead. At last she could endure it no longer. She begged him to tell her the worst. He replied, surprised, that it was a steam engine--he couldn't figure out the ratio of power to weight satisfactorily. The blame thing bothered him. "Oh, is that all?" Mrs. Ford said indignantly. "Well, I wouldn't bother about it if I were you. What does an old steam engine matter, anyhow? Come and sit down and forget about it." It was the one thing Ford could not do. His mind, once started on the project of building an engine to use on the farm, remained obstinately at work on the details. He spent weeks considering them one by one, thinking out adaptations, new devices, in an effort to overcome the difficulty. Still he could not see how to construct a cheap engine which would pull across his soft fields, carry the necessary weight of water, and still develop enough free power to be useful.