It is necessary to understand what is meant by this big word. If into a pan of water you dip a glass tube, the water inside the tube rises above the level of the water in the pan. The smaller the tube the higher will the water rise. The greater rise inside is perhaps due to the fact that the glass attracts the particles of water more than the particles of water attract one another. Now apply this principle to the soil. [Illustration: FIG. 6. THE RIGHT WAY TO PLOW] The soil particles have small spaces between them, and the spaces act just as the tube does. When the water at the surface is carried away by drying winds and warmth, the water deeper in the soil rises through the soil spaces. In this way water is brought from its soil storehouse as plants need it. [Illustration: FIG. 7. APPARATUS FOR TESTING THE HOLDING OF WATER BY DIFFERENT SOILS] Of course when the underground water reaches the surface it evaporates. If we want to keep it for our crops, we must prepare a trap to hold it. Nature has shown us how this can be done. Pick up a plank as it lies on the ground. Under the plank the soil is wet, while the soil not covered by the plank is dry. Why? Capillarity brought the water to the surface, and the plank, by keeping away wind and warmth, acted as a trap to hold the moisture. Now of course a farmer cannot set a trap of planks over his fields, but he can make a trap of dry earth, and that will do just as well. When a crop like corn or cotton or potatoes is cultivated, the fine, loose dirt stirred by the cultivating-plow will make a mulch that serves to keep water in the soil in the same way that the plank kept moisture under it. The mulch also helps to absorb the rains and prevents the water from running off the surface. Frequent cultivation, then, is one of the best possible ways of saving moisture. Hence the farmer who most frequently stirs his soil in the growing season, and especially in seasons of drought, reaps, other things being equal, a more abundant harvest than if tillage were neglected. =EXERCISE= 1. Why is the soil wet under a board or under straw? 2. Will a soil that is fine and compact produce better crops than one that is loose and cloddy? Why? 3. Since the water which a plant uses comes through the roots, can the morning dew afford any assistance? 4. Why are weeds objectionable in a growing crop? 5. Why does the farmer cultivate growing corn and cotton? SECTION IV. HOW THE WATER RISES IN THE SOIL [Illustration: FIG. 8. USING LAMP-CHIMNEYS TO SHOW THE RISE OF WATER IN SOIL]