Some kinds of termites live in rotten trees, which they tunnel into, and that is their contribution to soil-making; while others build great, big solid houses of earth and fibres, mixed. These houses are called "termitariums," and are six, eight, ten, even twenty-five feet high; fully 1,000 times the length of the worker. Think of a man five feet high, and then multiply by 1,000, and you see you have got nearly a mile! [Illustration: SKYSCRAPERS A MILE HIGH "Some kinds of termites build great, solid houses of earth and fibres mixed. These houses are six, eight, ten, even twenty-five feet high, fully one thousand times the length of the worker. Think of a man five feet high and then multiply by one thousand, and you see you have got nearly a mile."] These termite skyscrapers aren't much to look at on the outside, but inside they're just fine; they have everything the most particular ant could want. For instance, the termites are right up-to-date in their ideas about fresh air, their houses being well ventilated through windows left in the walls for that purpose. You can see the importance of this fresh-air system when you know there are thousands of termites under the same roof. They also have a sewage system for carrying off the water of the rains. And a fine piece of mechanical engineering the building of it is, too; for these "water-pipes" are the underground passages hollowed out in getting the clay to build the homes. The termites build their homes with one hand and dig the sewer with the other, so to speak. THE THERMOSTATS FOR THE NURSERIES The termitarium has as many rooms in it as a big hotel--oh, I don't know _how_ many--and they are all built around the chambers of the king and queen. Next to the royal apartments are the pantries, a lot of them, and they are all stored with food. In the upper part of the termitarium are the nurseries--many nurseries--for no one nursery could care for any such numbers of babies as the queen has. Between the nursery and the roof is an air-space, and there are also air-spaces on the sides and beneath. The nursery thus being surrounded by air, the eggs and, when they come along, the babies are protected from changes of temperature. It's the same principle that's employed in making refrigerators and thermos bottles. The rooms in which the eggs are kept are divided by walls made of fragments of wood and gum glued together. This mixture is a bad conductor[14] of heat or cold. And so the eggs are kept at an even temperature. [14] A "bad" conductor is often a _good_ thing, as you'll see by looking it up in the dictionary.