NATURE-STUDY LESSONS. 153 



3. (a) Compare variations, if any, in color and depth 



of soil and color of subsoil in the diiiferent 

 excavations made. 

 {b) Account as far as possible for each variation 

 noted. 



4. Of what is the surface layer in the forest composed? 



The dark surface matter found in woods and formed of decaying vegeta- 

 tion is organic matter. 



The part of the soil resulting from the decomposition of rocks is 

 inorganic matter. 



The organic matter, whether of vegetable or animal origin, in a soil is 

 called humus. 



5. {a) At a selected^excavation, carefully take off 



about a/pec k/ of the soil, cutting from the 

 surface straight down to the subsoil. 



(J)) By hand or with a trowel, break up and thor- 

 oughly stir and mix the soil on a board to 

 obtain a true sample. 



if) Weigh out a pound and spread it out thin on a 

 board or sheet of paper. Put it in a drying- 

 place for twelve hours or longer, occasionally 

 stirring it to " air-dry " it. 



6. {a) Weigh the dried soil. 



{b) Compare with the weight before drying. 

 (^) Observe any change in color. 

 {d) State your conclusions. 



7. (a) Place the air-dried soil on a flat shovel or spread 



it in a pan and put on a stove, or in a hot 

 oven for three or four hours to " kiln-dry " it. 

 (J?) Weigh again and compare as before. 



8. Return the kiln-dried soil to the shovel and put it 

 on the fire — not on the stove. When it has burned and 

 smouldered until it ceases to smoke remove, cool, and 



