70 THE ESSENTIALS OF AGRICULTURE 



same diameter and length, all stoppered at one end and each contain- 

 ing the same amount of water (200 to 300 centimeters in height), place 

 one sample of soil in each tube. Shake well, stand in upright position, 

 and observe at intervals, to see the way in which the soil settles in 

 each case. Which soil settles first ? Explain. 



3. Percolation of water through soils of different textures. 

 MATERIAL: Three brass, glass, or galvanized-iron tubes from ij to 



2 inches in diameter and from 8 to 10 inches long (straight lamp chimneys 

 may be used) ; a rack or support to hold the tubes in place ; 3 small beakers 

 or cups ; a graduated cylinder. 



Tie a piece of cloth over one end of each tube and fill the tubes level 

 full with the finely sifted soils that are to be tested. Use sand in one 

 tube, loam in a second, and clay or clay loam in a third. Compact all 

 to the same degree by allowing each to drop three times on the table 

 from a height of one inch. Place the tubes in the support, with the 

 beakers beneath, and pour a known amount of water in at the top, 

 beginning with the tube containing the clay. Note the time required 

 for the water to begin dripping. Then pour the same amount of water 

 into each of the other tubes, and note the amount of water that passes 

 through in the length of time allowed the clay tube. Calculate the 

 relative rates of water percolation through these soils. 



4. Effect of texture on capillary rise of water in soil. 

 MATERIAL: Five glass tubes from | to i inches inside diameter and 



2 feet long ; a pan for water ; a support for the tubes. 



Tie a cloth over one end of each tube. Fill one with finely sifted 

 and pulverized clay or clay-loam soil, another with finely sifted sandy- 

 loam soil, and a third with sand. Jar each gently and in the same 

 manner in order to settle the soil equally. Pour four inches of finely 

 sifted sandy loam into the fourth tube, and insert enough finely cut 

 straw to fill it for two inches, and pack the straw with a stick. Fill the 

 tube with the fine sandy loam. In the fifth tube put clods instead of 

 straw to serve as a barrier to the rise of the capillary water, but do 

 not compact with the stick. Support each tube upright with the 

 cloth-covered end in a pan of water and observe the height to 

 which the water has risen in each soil at the following intervals : five, 

 ten, thirty, and sixty minutes; two, three, twenty-four, forty-eight, 

 seventy-two, and ninety-six hours. Plot curves of each to show results. 

 Explain results. 



