35 



Experiuii'tif Xo. 9. 



DETERMINATION OK THE POWEK OF LOOSE i^OII.S To RETAIN MOISTURE. 



1. Place 100 grains of the air-dried soil in a beaker and add 100 riiliic centimeters 



of distilled water. 



2. Mix the soil and water thoroughly and rinse the soil upon a previously sat- 

 urated filter with a known amount of distilled water. Cover the top of the funnel 

 with a glass plate to prevent evaporation. 



3. Catch the water which drains away, in a graduate, and deduct the amount of 

 water caught from the total amount used. The remainder represents the amount 



retained by the soil. 



4. With'a special sample of the soil used determine the per cent of hygroscopic 



water. 



Calculation.— Aitev finding the per cent of hygroscopic water, determine the 

 amount of water-free soil in the lOO-gram sample taken. Add the total amount of 

 hygroscopic water to the capillary water retained and divide the sum l)y tlie weight 

 of water-free soil, and the quotient will represent the per cent of water held, calcu- 

 lated on the basis of water-free soil. 



Per cent of water retained was: Sand, ; clay, ; loam, ; gravel, 



Why do you use air-dried soil in this experiment? 

 Why do you moisten the filter? . 



Experiment Nu. 1£. 



DETERMINATION OF THE RATE OF I'ERCOLATION OF AlU THKOlOlI SOIL.S. 



1. Fill the series of tubes provided for this experiment with the finely pulverized 

 and sifted soils without compacting. 



2. Attach the tubes successively to the aspirator and note the length of time 

 required to force or draw 10 liters of air thnjugh each sample of soil. The aspirator 

 weight must be started from the same height in each case. 



This experiment illustrates the relative aeration of soils, a question whicii is of 

 importance in connection with the subject of the growth and development of the 

 nitrifying and other Itacteria of the soil concerned in the production of plant food. 



Time required for sand, ; gravel, ; loam, ; clay, . 



Experiment No. 13. 



CAPILLARY ATTRACTION OF SOILS. 



1. Close the lower en<l of 12 of the large glass tubes l)y a piece of thin muslin tied 

 firmly to the tubes. The tubes are then filled with the finely pulverized air-dried 

 soils, which have been carefully sifted to remove all small stones. These tubes are 

 to be filled with each soil— No. 1, by simply pouring the soil as loosely as possible 

 into the tube; No. 2, by compacting the soil gently liy tapping the lower end of the 

 tube upon the bench, and No. 4, by compacting the soil by ramming with a rod. 

 Care must be taken to compact the different soils to the same degree, both in the 

 jarring and ramming, by jarring or ramming each tube the same number of times. 



The tuljes are n(jw placed in the supporting frame in such a manner that tlie lower 

 ends shall dip one-half inch beneath the surface of a tray of water. 



The experiment is now ready for observation at intervals of twenty-four liouis, 

 when the height to which the water has risen is carefully measured and recorded- 



