“And all these things happened to him,” said the Professor. “That's what makes the song so interesting.” “He must have had a very curious life,” said Sylvie. “You may say that!” the Professor heartily rejoined. “Of course she may!” cried Bruno. By this time we had come up to the Gardener, who was standing on one leg, as usual, and busily employed in watering a bed of flowers with an empty watering-can. “It hasn't got no water in it!” Bruno explained to him, pulling his sleeve to attract his attention. “It's lighter to hold,” said the Gardener. “A lot of water in it makes one's arms ache.” And he went on with his work, singing softly to himself, “The nights are very damp!” “In digging things out of the ground which you probably do now and then,” the Professor began in a loud voice; “in making things into heaps--which no doubt you often do; and in kicking things about with one heel--which you seem never to leave off doing; have you ever happened to notice another Professor something like me, but different?” “Never!” shouted the Gardener, so loudly and violently that we all drew back in alarm. “There ain't such a thing!” “We will try a less exciting topic,” the Professor mildly remarked to the children. “You were asking--” “We asked him to let us through the garden-door,” said Sylvie: “but he wouldn't: but perhaps he would for you!” The Professor put the request, very humbly and courteously. “I wouldn't mind letting you out,” said the Gardener. “But I mustn't open the door for children. D'you think I'd disobey the Rules? Not for one-and-sixpence!” The Professor cautiously produced a couple of shillings. “That'll do it!” the Gardener shouted, as he hurled the watering-can across the flower-bed, and produced a handful of keys--one large one, and a number of small ones. “But look here, Professor dear!” whispered Sylvie. “He needn't open the door for us, at all. We can go out with you.” “True, dear child!” the Professor thankfully replied, as he replaced the coins in his pocket. “That saves two shillings!” And he took the children's hands, that they might all go out together when the door was opened. This, however, did not seem a very likely event, though the Gardener patiently tried all the small keys, over and over again. At last the Professor ventured on a gentle suggestion. “Why not try the large one? I have often observed that a door unlocks much more nicely with its own key.” The very first trial of the large key proved a success: the Gardener opened the door, and held out his hand for the money. The Professor shook his head. “You are acting by Rule,” he explained, “in opening the door for me. And now it's open, we are going out by Rule--the Rule of Three.” The Gardener looked puzzled, and let us go out; but, as he locked the door behind us, we heard him singing thoughtfully to himself,