Sandy soils with sandy subsoils do not often need drainage; such soils are naturally drained. With clay soils it is different. It is very important to remove the stagnant water in them and to let the air in. When land has been properly drained the other steps in improvement are easily taken. After soil has been dried and mellowed by proper drainage, then commercial fertilizers, barnyard manure, cowpeas, and clover can most readily do their great work of improving the texture of the soil and of making it fitter for plant growth. [Illustration: FIG. 10. A TILE IN POSITION] =Tile Drains.= Tile drains are the best and cheapest that can be used. It would not be too strong to say that draining by tiles is the most perfect drainage. Thousands of practical tests in this country have proved the superiority of tile draining for the following reasons: 1. Good tile drains properly laid last for years and do not fill up. 2. They furnish the cheapest possible means of removing too much water from the soil. 3. They are out of reach of all cultivating tools. 4. Surface water in filtering through the tiles leaves its nutritious elements for plant growth. =EXPERIMENTS= =To show the Effect of Drainage.= Take two tomato cans and fill both with the same kind of soil. Punch several holes in the bottom of one to drain the soil above and to admit air circulation. Leave the other unpunctured. Plant seeds of any kind in both cans and keep in a warm place. Add every third day equal quantities of water. Let seeds grow in both cans and observe the difference in growth for two or three weeks. =To show the Effect of Air in Soils.= Take two tomato cans; fill one with soil that is loose and warm, and the other with wet clay or muck from a swampy field. Plant a few seeds of the same kind in each and observe how much better the dry, warm, open soil is for growing farm crops. SECTION VI. IMPROVING THE SOIL We hear a great deal about the exhaustion or wearing out of the soil. Many uncomfortable people are always declaring that our lands will no longer produce profitable crops, and hence that farming will no longer pay. Now it is true, unfortunately, that much land has been robbed of its fertility, and, because this is true, we should be most deeply interested in everything that leads to the improvement of our soils. When our country was first discovered and trees were growing everywhere, we had virgin soils, or new soils that were rich and productive because they were filled with vegetable matter and plant food. There are not many virgin soils now because the trees have been cut from the best lands, and these lands have been farmed so carelessly that the vegetable matter and available plant food have been largely used up. Now that fresh land is scarce it is very necessary to restore fertility to these exhausted lands. What are some of the ways in which this can be done?