The answer is that the piece of iron has been heated to the point where it gives off light of its own. The red you see is only one stage in the development of iron to the point where it makes its own light. If you heat it still more it will make a white light. You know that it produces the light itself, because if you take a piece of iron into a perfectly dark room and heat it to a white heat it will show better than where there is other light. If you continue the process the iron will melt and change in form. Therefore, the “red hot” name for a piece of iron in that state is a perfect name. It is a warning that the iron is coming to a point where if the heating process is continued, it will change its form and in this state, when treated according to known methods, the iron is turned into steel, which has many characteristics that iron does not possess. Now, I can, of course, hear you ask why doesn’t an iron kettle get red hot? and I can answer that easily. If you treat the kettle the same way as you do the piece of iron, it will get red hot. The difference is that you are thinking of an iron kettle with water in it. As long as there is any water in the kettle, that keeps it from getting hot. The water inside keeps the kettle from becoming red hot. If you took a hollow rod of iron and filled it with water, it would not become red hot as long as any water remained in the hollow portion. How Did the Sand Get on the Seashore? The sand on the seashore is nothing more or less than ground-up sandstone. In dealing with the inanimate things in the world we find that a very important element of all of them has been given the name silicon. When the crust of the earth, which is the part we call the land and rocks, and includes the part under the sea, was a molten mass, this silicon was burned, combining with the oxygen which surrounded everything, and produced what is known as silica. Silica is the name given to the thing which is left after you burn silicon. A very large part of this silica was deposited in parts of the earth, and when the crust of the earth cooled off it was sand. By pressure and contact with other substances it became stuck together, just as you can take wet sand at the seashore to-day and make bricks and houses and tunnels, excepting that in the case we speak of it was something besides water that pressed and stuck the little particles of sand together. They stuck together more permanently. Then when the oceans were formed, as shown in another part of this book, much of the sandstone was found to be at the bottom and on the shores of the oceans. The action of the water continually washing against the sandstone gradually broke the sandstone up into the tiny particles of sand again, and this is what makes the sand on the seashore. What Makes a Soap Bubble?