_Experiment No. 6._--Humus enables the soil to take up and hold large quantities of water. To illustrate this, two samples of soil should be obtained, one a humus, or alluvial, soil, rich in organic matter, and the other a sandy soil. Put the two samples where they will become thoroughly air dry. Procure, say five pounds each of the dry soils, and put each into a glass tube over one end of which there is tied a piece of muslin, or fine wire gauze. From a graduated glass pour water slowly upon each sample until the water begins to drain from the bottom of the tube. In this way it can be shown which soil has the greater power of holding moisture. Both samples should then be set away to dry. By weighing the samples each day, it can be determined which soil has the greater power of retaining moisture. This experiment may be conducted not only with sand and humus, but with clay, loam, gravel, and all other kinds of soil. _Experiment No. 7._--A finely pulverized soil will hold more film-moisture than a cloddy soil. To illustrate the importance of texture as related to moisture, soil should be secured which is cloddy, or lumpy. One tube should be filled, as heretofore described (Exp. No. 6), with the lumpy soil, and the other tube with the fine soil which results from pulverizing the lumps, equal weights of soil being used in each case. From a graduated glass pour water upon each sample until the drainage begins from the bottom. Notice which soil possesses greater power of absorbing moisture. Put the samples away to dry, and by careful weighing, each day, it can be determined which soil dries out more readily. [Illustration: _Fig. 37. "Foot-prints on the sands of time."_] [Illustration: _Fig. 38. A cross section through one of the foot-prints._]