18 MANUAL OF GENEBAL AGKRICULTUBE. 



taining water. Tightly close the fruit jar and set in the 

 sun. Repeat, using clay and loam. "Weigh at each labora- 

 tory meeting thereafter until the weight becomes constant. 

 Remove the receptacle at each weighing. 



Calculate the amount of moisture absorbed in each 

 case. These amounts are not the total moisture since the 

 hygroscopic moisture was always present. 



Questions: 1. Which class of soils absorb the larg- 

 est amount of moisture, and why? 2. If soil absorbs so 

 little moisture from a saturated atmosphere; why do 

 wilted plants "freshen" on a foggy morning? 



16. EFFECT OF LIME ON SOILS. 



Materials: Clay or clay soil, 2 cigar boxes, slaked 

 lime. 



Prepare four moulds one inch in width and the length 

 of the width of the cigar box. Use pieces of one cigar box 

 for the partitions in the other, thus having the four 

 moulds in one box. "Weigh out four 100 gr. samples of 

 clay soil and add the following amounts of well-pulverized 

 slaked lime : 



No. 1, add none. 



No. 2, add one gram. 



No. 3, add five grams. 



No. 4, add ten grams. 



Mix each sample thoroughly in a pan, then add just 

 enough water to make the soil plastic. Mould each sam- 

 ple into a form of a stick by compressing the moist clay in 

 the moulds. Leave in the sun at least a week, or bake in 

 an oven until thoroughly dry. Remove the sticks and 

 determine the weight necessary to break each in the fol- 

 lowing manner: 



Rest the ends of a stick of clay upon supports and sus- 

 pend from its center a bucket into which sand is slowly 

 poured. 



Tabulate the results. 



Questions: 1. How does lime effect the tenacity of 

 clay? 2. What effect on the physical condition of clay 

 has lime? 



