104 ELEMENTS OF AGRICULTURE 



a little water and examine a drop (XlOO). Only a little of the silt is 

 better than too much in a drop. Mix the clay with water and examine a 

 drop of the slightly rily water (X500). Have each student make a draw- 

 lying of a few particles of each. Notice that the soil particles are real 

 minute rocks and humus. Find black particles of humus and draw them. 

 Find flocculated particles of clay, i. e., a number of particles united to 

 form a compound particle. If such particles are not readily seen, a little 

 clay soil moistened and a drop put under the micsrocope will show 

 them. Do you see any reason for having the soil soak a day? Keeping 

 a clay in good condition is largely a matter of keeping the particles 

 thus flocculated or united into small crumbs. 



38. One Effect of Humus and of Lime and of Freezing on a Clay Soil 



(for Humid Regions). 



Materials Two quarts of clay, one-fourth pound unslaked lime, 

 leaf mold or rotted manure, bottles or beakers. 



(a) An hour or more before the class, period, the lime should be 

 nearly covered with water to slake it. Divide the clay into four equal 

 parts. To the first two add water; to the third add water and about 

 half its volume of humus; to the fourth add lime-milk. Make each into 

 a ball and set aside to dry. If the weather is cold, put one of the first 

 two where it will freeze. In a few days examine and see which is more 

 mellow. What do you conclude as to the probable effect of working 

 clay land when too wet? What is one value of organic matter in clay 

 soil? What is one value of using lime on a clay soil? In what way do 

 farmers add organic matter to their soils? 



(6) Put about a tablespoonful of clay in each of the two bottles 

 Fill with water and shake. Add a little lime-milk to one bottle. Which 

 one settles more rapidly? Why? Is lime used on soils in your vicinity? 



39. Soil Solutions. 



Materials. Four or more "slips" of Wandering Jew or Inch Plant 

 (Tradescantia), two bottles, two crucibles, well water, rain water, or 

 distilled water. 



(a) Evaporate some well water in one crucible and some rain-water 

 in another. What is left in each case? What causes the inside of a 

 tea-kettle to become coated? 



(6) Put two of these slips in each bottle, fill one with well-water 

 and one with rain-water. Change the water about three times a week, 

 until the results are secured. In which do the plants grow best? Why? 



