He began putting away his things. It was Ernestine's birthday, and he had promised to be home early, for they were going to the theatre. "It will be like all the rest," he mused. "Once done, it will seem so easy that we will wonder why it was not done long before." Again the fire leaped high within him. To do it! Perhaps after all he did see it too complexly. He must not let the husk dull his eye to the kernel. A man building a beautiful tower must erect a scaffold. But the scaffolding should not make him forget the tower! Some way in this last hour his mind had seemed to clear. His immense amount of useless work was not hanging about his neck like a millstone. Something had cut that away. He was free from it all. He could feel within himself that his approach to his problem was better than it had been before. Perhaps he had made the mistake of the others of looking at it as something fearfully complex, something it would be the hardest thing in all the world for any man to do. It all looked more simple now. It was as if muscles strained to the point of tenseness had relaxed, and in an easy and natural way he foresaw victory as a logical part of his work. He was happy to-night, light-hearted. The windows of the laboratory were open to the soft air of that glorious day of early spring, and his spirit was open too, open to the soul of the world, taking unto itself the sweet and simple spirit of the men who have done the greatest things. From his window he could see one of the tennis courts. Some of the students were playing. "Good!" he exclaimed enthusiastically to himself, as he watched a return that had looked impossible. He was glad they were playing tennis. Why shouldn't they? Professor Hastings heard him whistling softly to himself--a German love song--as he walked through the big laboratory, and catching a glimpse of the younger man's face, he nodded his head and smiled. It had been a good afternoon--that was plain. Now let there be more afternoons like this--and then--to think it should be done right here under his very eyes! Was not that joy enough for any man? On the steps of the building Karl stopped suddenly, put his hand in his inner pocket and drew out a small box. Yes, it was there all right, and a girl passing up the steps just then was amazed and much fluttered to think Dr. Hubers should be smiling so beautifully at her. In fact, Dr. Hubers did not know that the girl was passing. She had simply been in the direction of his smile; and he was smiling because it was Ernestine's birthday, and because he had so beautiful a present for her. He walked along very fast. He could scarcely wait to see her face when he gave it to her. Too bad he had kept her waiting so long! CHAPTER XI PICTURES IN THE EMBERS They were back home now.