It was a fine June morning when they set out from the Gare de Lyon; but Mary became sad and apprehensive as one green mile after another was left behind under the changeless blue sky, for though she had ceased to pine for the life of the basement in Paternoster Row, she always felt while she was still in Paris that she knew the way back and that if ever she should be faced with something unbearably disagreeable, she should be able to escape. Now she was being carried farther away every moment like that bluebottle who was buzzing on the warm glass of the carriage windows. She began to make up a story about that bluebottle while Grandmamma dozed among her cushions on the opposite seat--a story of how this father bluebottle would arrive at Châteaublanc and try to find the mother bluebottle and all the little bluebottles. Of course if he knew the way back he would be better off than herself, because he would be able to fly. But he wouldn't know the way back, and he would go buzzing about Châteaublanc trying to find his home until one day he would be killed, and the mother bluebottle and all the little bluebottles in Paris would never know what had become of him. Mary was so much moved by the woeful story that she felt a tear spring to her eyes and a lump in her throat. If only she had thought of it sooner, she might have let the bluebottle out. Perhaps even now he would not have traveled too far to know his way back. Mary raised the blind and tried to help the bluebottle out of the open window with her handkerchief; but he did not seem able to understand that she was trying to help him and went buzzing all over the compartment until at last he buzzed across Grandmamma's nose and woke her up. "What are you doing, Mary?" Mary did not like to explain just what she was really doing. So she looked abashed and said that she was doing nothing. "Well, don't," said Grandmamma, dozing off again. Mary tried to think how one did not do nothing; which raised an old problem of how one thought about nothing, and she tried once more to think about nothing. "But if I think about nothing," she thought, "I'm thinking about thinking about nothing. And if I think about thinking about nothing I'm thinking about something." She once asked Uncle William if he could think about nothing and if not why not. Whereupon Uncle William had told her that Parmenides had been puzzled by the same problem two thousand years ago and more. "Who was Pa Many D's?" Mary had asked, for that was the way she pictured the name. Uncle William had informed her that Parmenides was a philosopher who founded the Eleatic school.