1. Tell the life-story of the common gull. 2. Make a list of all the sea birds you know. 3. The common gull has very large wings, curious beak and feet. Can you explain what these are for? [Illustration: Engine puffing on a cold day.] X.—DEW, FROST, RAIN. “How is it, Uncle George, that there is always a clear space between the spout of the kettle and the puff of steam?” It was Frank that asked the question. He had been watching the kettle boiling for a long time. “It is the same with the railway engine,” said Tom. “There is always a big space between the funnel and the puff.” “That is so,” said Uncle George. “But if you watch carefully, you will notice that the space between the funnel of the engine and the puff of steam is not always of the same size.” [Illustration: Engine puffing on a hot day.] “No,” said Frank, “I have noticed that the white puff is farther away from the funnel on a hot day than on a cold day.” “That is true,” said his uncle. “Perhaps you have also noticed that, as the engine rushes along, it leaves a long white cloud trailing in the air behind it. Sooner or later this long white cloud melts away from sight. It melts away sooner on a hot day than on a cold day. Where does it go?” “It goes into the air,” said Frank; “just as the cloud from this kettle goes into the air of the room.” “Very good,” said Uncle George. “Tom, will you please fetch me a tumbler full of cold water, and see that the outside of the glass is quite dry?” When Tom came back with the glass of cold water, Uncle George wiped it outside with a clean dry cloth. When he was sure that the outside of it was dry, he placed the tumbler of water on the table in the middle of the warm room. “Now,” he said, “let us try to answer Frank’s question about the clear space between the spout of the kettle and the puff of steam. “The fact is,” Uncle George went on, “the white puff which we call _steam_ is not steam at all. We might just as well call it ‘_water-dust_.’ For it is made up of tiny droplets of water—so tiny that they float in air. Steam is water in the form of gas. Like the air we breathe, it cannot be seen. In fact, this water-gas forms part of the air around us. The clear space between the spout of the kettle and the puff is made up of hot steam. We cannot see it. As it comes out into the colder air, it is cooled into the tiny droplets which form the puff. It is only when cooled into tiny droplets that we can see it. “If you hold any cold object, such as a knife, in the puff, these water particles run together and form large drops upon it. The cloud of water-dust melts away in the room, as Frank told us. What takes place is this. The tiny droplets, when spread out into the warm air, become real steam, or ‘water-gas,’ again. “The outside of this tumbler of cold water was quite dry when I placed it on the table. Run your finger along it and tell me what you find.”